Frequency/time selective precoding for positioning reference signals

文档序号：890061 发布日期：2021-02-23 浏览：11次中文

阅读说明：本技术 用于定位参考信号的频率/时间选择性预编码 (Frequency/time selective precoding for positioning reference signals ) 是由 A·马诺拉克斯 S·阿卡拉卡兰 J·B·索里亚加骆涛 J·E·斯密 N·布衫于 2019-07-17 设计创作，主要内容包括：公开了用于在多径多输入多输出(MIMO)信道上传送用于定位估计的参考信号以及处理该参考信号的技术。在各方面,第一节点配置用于传送第一参考信号集和第二参考信号集的第一参考信号资源集和第二参考信号资源集,其中该第一参考信号资源集和第二参考信号资源集出现在MIMO信道的第一子带和第二子带上和/或在MIMO信道上的第一时间区间和第二时间区间期间,其中该第一参考信号资源集和第二参考信号资源集中的每个参考信号资源至少利用第一MIMO预编码器和第二MIMO预编码器；以及在该MIMO信道上向第二节点传送该第一参考信号集和第二参考信号集,其中该第一节点传送该第一参考信号集和第二参考信号集以辅助该第二节点基于该第一参考信号集和第二参考信号集的联合处理来执行定位测量。(Techniques for transmitting and processing reference signals for position estimation over a multipath multiple-input multiple-output (MIMO) channel are disclosed. In aspects, a first node configures first and second sets of reference signal resources for transmitting first and second sets of reference signals, wherein the first and second sets of reference signal resources occur on first and second subbands of a MIMO channel and/or during first and second time intervals on the MIMO channel, wherein each reference signal resource of the first and second sets of reference signal resources utilizes at least a first MIMO precoder and a second MIMO precoder; and transmitting the first and second reference signal sets to a second node over the MIMO channel, wherein the first node transmits the first and second reference signal sets to assist the second node in performing positioning measurements based on joint processing of the first and second reference signal sets.)

1. An apparatus for transmitting reference signals for position estimation over a multipath multiple-input multiple-output (MIMO) channel, comprising:

at least one processor of a first node, the at least one processor configured to:

configuring a first set of reference signal resources for transmitting a first set of reference signals, wherein the first set of reference signal resources occur on a first subband of the MIMO channel and/or during a first time interval on the MIMO channel, and wherein each reference signal resource in the first set of reference signal resources utilizes at least a first MIMO precoder; and

configuring a second set of reference signal resources for transmitting a second set of reference signals, wherein the second set of reference signal resources occur on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel, and wherein each reference signal resource in the second set of reference signal resources utilizes at least a second MIMO precoder; and

at least one transmitter of the first node, the at least one transmitter configured to:

transmitting the first set of reference signals to a second node over the MIMO channel using the first set of reference signal resources during the first time interval on the first subband of the MIMO channel and/or on the MIMO channel; and

transmitting the second set of reference signals to the second node over the MIMO channel using the second set of reference signal resources on the second subband of the MIMO channel and/or during the second time interval on the MIMO channel,

wherein the first node transmits the first set of reference signals and the second set of reference signals to assist the second node in performing positioning measurements based on processing of the first set of reference signals and the second set of reference signals.

2. The apparatus of claim 1, wherein each reference signal resource in the first set of reference signal resources utilizes a first plurality of MIMO precoders that vary over time and/or frequency, including the first MIMO precoder, and

wherein each reference signal resource in the second set of reference signal resources utilizes a second plurality of MIMO precoders that vary over time and/or frequency, including the second MIMO precoder.

3. The apparatus of claim 2, wherein the first and second pluralities of MIMO precoders vary over time and/or frequency for each of the first and second sets of reference signal resources based on configured precoder granularity.

4. The apparatus of claim 3, further comprising a receiver of the first node, the receiver configured to:

receiving, from the second node, an indication of the configured precoder granularity.

5. The apparatus of claim 2, wherein the first and second pluralities of MIMO precoders vary over time and/or frequency for each of the first and second sets of reference signal resources based on the configured temporal coherence parameter.

6. The apparatus of claim 5, further comprising a receiver of the first node, the receiver configured to:

receiving an indication of the configured temporal coherence parameter from the second node.

7. The apparatus of claim 2, wherein the first and second pluralities of MIMO precoders vary with time and/or frequency for each of the first and second sets of reference signal resources based on configured Small Delay Cyclic Delay Diversity (SDCDD).

8. The apparatus of claim 7, further comprising a receiver of the first node, the receiver configured to:

receiving an indication of the configured SDCDD from the second node.

9. The apparatus of claim 2, wherein the first and second pluralities of MIMO precoders vary over time and/or frequency for each of the first and second sets of reference signal resources based on a configured set of precoder cycles and precoder cyclic ordering.

10. The apparatus of claim 9, further comprising a receiver of the first node, the receiver configured to:

receiving, from the second node, an indication of the configured precoder cycling set and precoder cycling ordering.

11. The apparatus of claim 1, further comprising a receiver of the first node, the receiver configured to:

receiving, from the second node, an indication of a number of reference signal resources to include in the first set of reference signal resources and the second set of reference signal resources.

12. The apparatus of claim 1, wherein the first set of reference signal resources comprises a plurality of reference signal resources on a same Orthogonal Frequency Division Multiplexing (OFDM) symbol in disjoint subbands of the MIMO channel.

13. The apparatus of claim 1, wherein the first and second MIMO precoders used in each of the first and second subbands are pseudo-randomly chosen MIMO precoders based on a cyclic set of MIMO precoders.

14. The apparatus of claim 1, further comprising a receiver of the first node, the receiver configured to:

receiving, from the second node, a recommendation of the first and second MIMO precoders to be used for encoding the first and second sets of reference signal resources.

15. An apparatus for processing reference signals for position estimation over a multipath multiple-input multiple-output (MIMO) channel, comprising:

a transceiver of a second node, the transceiver configured to:

receiving, from a first node, a first set of reference signal resources on a first set of reference signal resources, wherein the first set of reference signal resources occur on a first subband of the MIMO channel and/or during a first time interval on the MIMO channel, and wherein each reference signal resource in the first set of reference signal resources utilizes at least a first MIMO precoder; and

receiving, from the first node, a second set of reference signal resources on a second set of reference signal resources, wherein the second set of reference signal resources occurs on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel, and wherein each reference signal resource in the second set of reference signal resources utilizes at least a second MIMO precoder; and

at least one processor of the second node, the at least one processor configured to:

identifying at least one reference signal transmitted on the first set of reference signal resources and the second set of reference signal resources as following a line-of-sight (LOS) path between the second node and the first node; and

performing time difference of arrival (TDOA) measurements based on the at least one reference signal.

16. The apparatus of claim 15, wherein each reference signal resource in the first set of reference signal resources utilizes a first plurality of MIMO precoders that vary over time and/or frequency, including the first MIMO precoder, and

17. The apparatus of claim 16, wherein the transceiver is further configured to:

transmitting, to the first node, an indication of the configured precoder granularity, wherein the first and second plurality of MIMO precoders vary over time and/or frequency for each of the first and second sets of reference signal resources based on the configured precoder granularity.

18. The apparatus of claim 16, wherein the transceiver is further configured to:

transmitting, to the first node, an indication of the configured temporal coherence parameters, wherein the first plurality of MIMO precoders and the second plurality of MIMO precoders vary over time and/or frequency for each of the first set of reference signal resources and the second set of reference signal resources based on the configured temporal coherence parameters.

19. The apparatus of claim 16, wherein the transceiver is further configured to:

transmitting an indication of the configured Small Delay Cyclic Delay Diversity (SDCDD) to the first node, wherein the first and second plurality of MIMO precoders vary with time and/or frequency for each of the first and second sets of reference signal resources based on the configured SDCDD.

20. The apparatus of claim 16, wherein the transceiver is further configured to:

transmitting, to the first node, an indication of the configured precoder cyclic set and precoder cyclic ordering, wherein the first and second plurality of MIMO precoders vary over time and/or frequency for each of the first and second sets of reference signal resources based on the configured precoder cyclic set and precoder cyclic ordering.

21. The apparatus of claim 15, wherein the transceiver is further configured to:

sending a recommendation to the first node of a number of reference signal resources to include in the first set of reference signal resources.

22. The apparatus of claim 15, wherein the transceiver is further configured to:

sending, to the first node, a recommendation of the first and second MIMO precoders to be used for encoding the first and second sets of reference signal resources.

23. A method performed by a first node for transmitting reference signals for positioning estimation over a multipath multiple-input multiple-output (MIMO) channel, comprising:

wherein the first node transmits the first set of reference signals and the second set of reference signals to assist the second node in performing positioning measurements based on joint processing of the first set of reference signals and the second set of reference signals.

24. The method of claim 23, wherein each reference signal resource in the first set of reference signal resources utilizes a first plurality of MIMO precoders that vary over time and/or frequency, including the first MIMO precoder, and

25. The method of claim 23, wherein the first set of reference signal resources comprises a plurality of reference signal resources on a same Orthogonal Frequency Division Multiplexing (OFDM) symbol in disjoint subbands of the MIMO channel.

26. The method of claim 23, wherein the first and second MIMO precoders used in each of the first and second subbands are pseudo-randomly chosen MIMO precoders based on a cyclic set of MIMO precoders.

27. A method performed by a second node for processing reference signals for position estimation over a multipath multiple-input multiple-output (MIMO) channel, comprising:

performing time difference of arrival (TDOA) measurements based on the at least one reference signal.

28. The method of claim 27, wherein each reference signal resource in the first set of reference signal resources utilizes a first plurality of MIMO precoders that vary over time and/or frequency, including the first MIMO precoder, and

29. The method of claim 27, further comprising:

sending, by the second node, a recommendation to the first node of a number of reference signal resources to include in the first set of reference signal resources.

30. The method of claim 27, further comprising:

sending, by the second node to the first node, a recommendation of the first and second MIMO precoders to be used for encoding the first and second sets of reference signal resources.

Technical Field

Various aspects described herein relate generally to wireless communication systems, and more particularly, to frequency/time selective precoding for positioning reference signals.

Background

Wireless communication systems have evolved over several generations, including first generation analog wireless telephone service (1G), second generation (2G) digital wireless telephone service (including transitional 2.5G and 2.75G networks), third generation (3G) internet-capable high-speed data wireless service, and fourth generation (4G) service (e.g., Long Term Evolution (LTE) or WiMax). There are many different types of wireless communication systems in use today, including cellular and Personal Communication Services (PCS) systems. Examples of known cellular systems include the cellular analog Advanced Mobile Phone System (AMPS), and digital cellular systems based on Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), global system for mobile access (GSM) TDMA variants, and the like.

Fifth generation (5G) mobile standards require higher data transfer speeds, a greater number of connections and better coverage, among other improvements. According to the next generation mobile network alliance, the 5G standard is designed to provide data rates of tens of megabits per second to each of thousands of users, and 1 gigabit per second to tens of employees on an office floor. Hundreds or thousands of simultaneous connections should be supported to support large sensor deployments. Therefore, the spectral efficiency of 5G mobile communication should be significantly improved compared to the current 4G standard. Furthermore, the signaling efficiency should be improved and the latency should be reduced substantially compared to the current standard.

Some wireless communication networks, such as 5G, support operation at very high frequency and even Extremely High Frequency (EHF) bands, such as the millimeter wave (mmW) band (in general, wavelengths of 1mm to 10mm, or 30 to 300 gigahertz GHz). These very high frequencies can support very high throughput, such as up to six gigabits per second (Gbps). However, one of the challenges in wireless communication at very high or very high frequencies is that significant propagation losses may occur due to the high frequencies. As the frequency increases, the wavelength may decrease and the propagation loss may also increase. At the mmW band, propagation loss may be severe. For example, the propagation loss may be on the order of 22 to 27 decibels (dB) relative to that observed in the 2.4GHz or 5GHz frequency bands.

Propagation loss is also a problem in multiple-input multiple-output (MIMO) and massive MIMO systems in any frequency band. The term MIMO as used herein will generally refer to both MIMO and massive MIMO. MIMO is a method for multiplying the capacity of a radio link by using multiple transmit and receive antennas to exploit multipath propagation. Multipath propagation occurs because Radio Frequency (RF) signals travel not only along the shortest path between the transmitting and receiving parties, which may be a line of sight (LOS) path, but also on several other paths, as these RF signals spread away from the transmitting party and are reflected by other objects, such as hills, buildings, water, etc., on their way to the receiving party. A transmitting party in a MIMO system includes multiple antennas and exploits multipath propagation by orienting the antennas to each transmit the same RF signal on the same radio channel to a receiving party. The receiving party is also equipped with multiple antennas tuned to the radio channel, which can detect the RF signals transmitted by the transmitting party. When the RF signals reach the receiving party (some of the RF signals may be delayed due to multipath propagation), the receiving party may combine them into a single RF signal. Propagation loss is also a problem in MIMO systems because the transmitter transmits each RF signal at a lower power level than would otherwise be transmitted for a single RF signal.

To support position estimation in terrestrial wireless networks, mobile devices may be configured to measure and report observed time difference of arrival ("OTDOA"; OTDOA is also referred to simply as "time difference of arrival" or "TDOA") or Reference Signal Timing Difference (RSTD) between reference RF signals received from two or more network nodes, e.g., different base stations or different transmission points (e.g., antennas) belonging to the same base station. In order to make OTDOA-based positioning accurate, the receiving party needs to be able to accurately estimate the LOS or earliest path of the channel. However, due to blockage (e.g., hills, buildings, water, etc.), RF signals on LOS paths may be received at significantly lower power than RF signals on other non-LOS (nlos) paths (multipath). Thus, the recipient may erroneously treat any of these NLOS paths as LOS paths.

SUMMARY

The following presents a simplified summary in connection with one or more aspects disclosed herein. As such, the following summary should not be considered an extensive overview relating to all contemplated aspects, nor should the following summary be considered to identify key or critical elements relating to all contemplated aspects or to delineate the scope associated with any particular aspect. Accordingly, the sole purpose of the following summary is to present some concepts related to one or more aspects related to the mechanisms disclosed herein in a simplified form prior to the detailed description presented below.

In an aspect, a method for transmitting reference signals for position estimation over a multipath MIMO channel, comprising: configuring, by a first node, a first set of reference signal resources for transmitting a first set of reference signals, wherein the first set of reference signal resources occur on a first subband of the MIMO channel and/or during a first time interval on the MIMO channel, and wherein each reference signal resource of the first set of reference signal resources utilizes at least a first MIMO precoder; configuring, by the first node, a second set of reference signal resources for transmitting a second set of reference signals, wherein the second set of reference signal resources occur on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel, and wherein each reference signal resource in the second set of reference signal resources utilizes at least a second MIMO precoder; transmitting, by the first node, a first set of reference signals on the MIMO channel to a second node using a first set of reference signal resources on a first subband of the MIMO channel and/or during a first time interval on the MIMO channel; and transmitting, by the first node, a second set of reference signal resources on the MIMO channel during a second time interval on a second subband of the MIMO channel and/or on the MIMO channel to the second node, wherein the first node transmits a first set of reference signals and a second set of reference signals to assist the second node in performing positioning measurements based on joint processing of the first set of reference signals and the second set of reference signals.

In an aspect, a method for processing reference signals for position estimation over a multipath MIMO channel, comprising: receiving, by a second node from a first node, a first set of reference signal resources on a first set of reference signal resources, wherein the first set of reference signal resources occur on a first subband of and/or during a first time interval on the MIMO channel, and wherein each reference signal resource in the first set of reference signal resources utilizes at least a first MIMO precoder; receiving, by the second node from the first node, a second set of reference signal resources on a second set of reference signal resources, wherein the second set of reference signal resources occur on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel, and wherein each reference signal resource in the second set of reference signal resources utilizes at least a second MIMO precoder; identifying, by the second node, at least one reference signal transmitted on the first set of reference signal resources and the second set of reference signal resources as following a LOS path between the second node and the first node; and performing, by the second node, time difference of arrival (TDOA) measurements based on the at least one reference signal.

In an aspect, an apparatus for transmitting reference signals for position estimation over a multipath MIMO channel, comprising: at least one processor of a first node, the at least one processor configured to: configuring a first set of reference signal resources for transmitting a first set of reference signals, wherein the first set of reference signal resources occur on a first subband of the MIMO channel and/or during a first time interval on the MIMO channel, and wherein each reference signal resource in the first set of reference signal resources utilizes at least a first MIMO precoder; and configuring a second set of reference signal resources for transmitting a second set of reference signals, wherein the second set of reference signal resources occur on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel, and wherein each reference signal resource in the second set of reference signal resources utilizes at least a second MIMO precoder; and a transmitter of the first node, the transmitter configured to: transmitting a first set of reference signals to a second node over the MIMO channel using a first set of reference signal resources on a first subband of the MIMO channel and/or during a first time interval over the MIMO channel; and transmitting, on the MIMO channel, a second set of reference signal resources on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel to the second node, wherein the first node transmits a first set of reference signals and a second set of reference signals to assist the second node in performing positioning measurements based on joint processing of the first set of reference signals and the second set of reference signals.

In an aspect, an apparatus for processing reference signals for position estimation over a multipath MIMO channel, comprising: a transceiver of the second node, the transceiver configured to: receiving, from a first node, a first set of reference signal resources on a first set of reference signal resources, wherein the first set of reference signal resources occur on a first subband of the MIMO channel and/or during a first time interval on the MIMO channel, and wherein each reference signal resource in the first set of reference signal resources utilizes at least a first MIMO precoder; and receiving a second set of reference signals on a second set of reference signal resources from the first node, wherein the second set of reference signal resources occur on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel, and wherein each reference signal resource in the second set of reference signal resources utilizes at least a second MIMO precoder; and at least one processor of the second node, the at least one processor configured to: identifying at least one reference signal transmitted on a first set of reference signal resources and a second set of reference signal resources as following a LOS path between a second node and a first node; and performing, by the second node, TDOA measurements based on the at least one reference signal.

In an aspect, an apparatus for transmitting reference signals for position estimation over a multipath MIMO channel, comprising: means for processing of a first node, the means configured to: configuring a first set of reference signal resources for transmitting a first set of reference signals, wherein the first set of reference signal resources occur on a first subband of the MIMO channel and/or during a first time interval on the MIMO channel, and wherein each reference signal resource in the first set of reference signal resources utilizes at least a first MIMO precoder; and configuring a second set of reference signal resources for transmitting a second set of reference signals, wherein the second set of reference signal resources occur on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel, and wherein each reference signal resource in the second set of reference signal resources utilizes at least a second MIMO precoder; and means for communicating of the first node, the means configured to: transmitting a first set of reference signals to a second node over the MIMO channel using a first set of reference signal resources on a first subband of the MIMO channel and/or during a first time interval over the MIMO channel; and transmitting, on the MIMO channel, a second set of reference signal resources on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel to the second node, wherein the first node transmits a first set of reference signals and a second set of reference signals to assist the second node in performing positioning measurements based on joint processing of the first set of reference signals and the second set of reference signals.

In an aspect, an apparatus for processing reference signals for position estimation over a multipath MIMO channel, comprising: means for the second node for communicating, the means configured to: receiving, from a first node, a first set of reference signal resources on a first set of reference signal resources, wherein the first set of reference signal resources occur on a first subband of the MIMO channel and/or during a first time interval on the MIMO channel, and wherein each reference signal resource in the first set of reference signal resources utilizes at least a first MIMO precoder; and receiving a second set of reference signals on a second set of reference signal resources from the first node, wherein the second set of reference signal resources occur on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel, and wherein each reference signal resource in the second set of reference signal resources utilizes at least a second MIMO precoder; and means for processing of the second node, the means configured to: identifying at least one reference signal transmitted on a first set of reference signal resources and a second set of reference signal resources as following a LOS path between a second node and a first node; and performing, by the second node, TDOA measurements based on the at least one reference signal.

In an aspect, a non-transitory computer-readable medium storing computer-executable instructions for transmitting reference signals for position estimation over a multipath MIMO channel, comprising computer-executable instructions, the computer-executable instructions comprising: at least one instruction instructing a first node to configure a first set of reference signal resources for transmitting a first set of reference signals, wherein the first set of reference signal resources occur on a first subband of the MIMO channel and/or during a first time interval on the MIMO channel, and wherein each reference signal resource in the first set of reference signal resources utilizes at least a first MIMO precoder; at least one instruction instructing the first node to configure a second set of reference signal resources for transmitting a second set of reference signals, wherein the second set of reference signal resources occur on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel, and wherein each reference signal resource in the second set of reference signal resources utilizes at least a second MIMO precoder; at least one instruction to instruct a first node to transmit a first set of reference signals to a second node over the MIMO channel using a first set of reference signal resources on a first subband of the MIMO channel and/or during a first time interval on the MIMO channel; and at least one instruction instructing a first node to transmit a second set of reference signals to the second node on the MIMO channel using a second set of reference signal resources on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel, wherein the first node transmits a first set of reference signals and a second set of reference signals to assist the second node in performing positioning measurements based on joint processing of the first set of reference signals and the second set of reference signals.

In an aspect, a non-transitory computer-readable medium storing computer-executable instructions for transmitting reference signals for position estimation over a multipath MIMO channel, comprising computer-executable instructions, the computer-executable instructions comprising: at least one instruction instructing a second node to receive a first set of reference signal resources on a first set of reference signal resources from a first node, wherein the first set of reference signal resources is present on a first subband of the MIMO channel and/or during a first time interval on the MIMO channel, and wherein each reference signal resource in the first set of reference signal resources utilizes at least a first MIMO precoder; at least one instruction instructing a second node to receive a second set of reference signal resources from the first node on a second set of reference signal resources, wherein the second set of reference signal resources occurs on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel, and wherein each reference signal resource in the second set of reference signal resources utilizes at least a second MIMO precoder; at least one instruction instructing the second node to identify at least one reference signal transmitted on the first set of reference signal resources and the second set of reference signal resources as following a LOS path between the second node and the first node; and at least one instruction to instruct the second node to perform TDOA measurements based on the at least one reference signal.

Other objects and advantages associated with the aspects disclosed herein will be apparent to those skilled in the art based on the drawings and detailed description.

Brief Description of Drawings

A more complete appreciation of the various aspects described herein, and many of the attendant advantages thereof, will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, which are given by way of illustration only, and not by way of limitation, and wherein:

fig. 1 illustrates an example wireless communication system in accordance with various aspects.

Fig. 2A and 2B illustrate example wireless network structures in accordance with various aspects.

Fig. 3 illustrates an example base station and an example UE in an access network in accordance with various aspects.

Fig. 4 illustrates an example wireless communication system in accordance with various aspects of the present disclosure.

Fig. 5A is a diagram of a structure of an example LTE subframe sequence with PRS positioning occasions.

Fig. 5B is an illustration of an exemplary mapping of PRSs to resource elements.

Fig. 6 is a graph illustrating RF channel response over time at a UE, in accordance with aspects of the present disclosure.

Fig. 7 is a block diagram of an embodiment of a transmitter unit to precode data for a multipath channel.

Fig. 8 and 9 illustrate exemplary methods for transmitting reference signals for positioning estimation over a MIMO channel and processing the reference signals.

Detailed Description

Various aspects described herein relate generally to wireless communication systems, and more particularly to frequency/time selective precoding for positioning reference signals in 5G NR.

These and other aspects are disclosed in the following description and related drawings to illustrate specific examples related to various exemplary aspects. Alternative aspects will be apparent to those skilled in the relevant art(s) upon reading this disclosure, and may be constructed and practiced without departing from the scope or spirit of the disclosure. Additionally, well-known elements will not be described in detail or may be omitted so as not to obscure the relevant details of the aspects disclosed herein.

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any aspect described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects. Likewise, the term "aspect" does not require that all aspects include the discussed feature, advantage or mode of operation.

The terminology used herein describes only certain aspects and should not be read as limiting any of the aspects disclosed herein. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood by those within the art that the terms "comprises," "comprising," "includes" and/or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Further, various aspects may be described in terms of sequences of actions to be performed by, for example, elements of a computing device. Those skilled in the art will recognize that various actions described herein can be performed by specific circuits (e.g., Application Specific Integrated Circuits (ASICs)), by program instructions being executed by one or more processors, or by a combination of both. Additionally, these sequence of actions described herein can be considered to be embodied entirely within any form of non-transitory computer readable medium having stored thereon a corresponding set of computer instructions that upon execution would cause an associated processor to perform the functionality described herein. Thus, the various aspects described herein may be embodied in a number of different forms, all of which have been contemplated to be within the scope of the claimed subject matter. Additionally, for each aspect described herein, the corresponding form of any such aspect may be described herein as, for example, "logic configured to" perform the described action and/or other structural components configured to perform the described action.

As used herein, the terms "user equipment" (or "UE"), "user device," "user terminal," "client device," "communication device," "wireless communication device," "handheld device," "mobile terminal," "mobile station," "handset," "access terminal," "subscriber device," "subscriber terminal," "subscriber station," "terminal," and variations thereof, may interchangeably refer to any suitable mobile or stationary device capable of receiving wireless communication and/or navigation signals. These terms are also intended to include a device that is in communication with another device that is capable of receiving wireless communication and/or navigation signals (such as via a short-range wireless, infrared, wired, or other connection), regardless of whether satellite signal reception, assistance data reception, and/or positioning-related processing occurs at the device or at the other device. In addition, these terms are intended to include all devices, including wireless and wired communication devices, which are capable of communicating with a core network via a Radio Access Network (RAN), and through which a UE is capable of connecting with external networks, such as the internet, as well as with other UEs. Of course, other mechanisms of connecting to the core network and/or the internet are also possible for the UE, such as over a wired access network, a Wireless Local Area Network (WLAN) (e.g., based on IEEE 802.11, etc.), and so forth. The UE can be implemented by any of several types of devices, including but not limited to a Printed Circuit (PC) card, a compact flash device, an external or internal modem, a wireless or wired phone, a smart phone, a tablet, a tracking device, an asset tag, and so forth. The communication link through which the UE can send signals to the RAN is called an uplink channel (e.g., a reverse traffic channel, a reverse control channel, an access channel, etc.). The communication link through which the RAN can send signals to the UEs is called a downlink or forward link channel (e.g., paging channel, control channel, broadcast channel, forward traffic channel, etc.). As used herein, the term Traffic Channel (TCH) may refer to an uplink/reverse or downlink/forward traffic channel.

According to various aspects, fig. 1 illustrates an example wireless communication system 100. The wireless communication system 100, which may also be referred to as a Wireless Wide Area Network (WWAN), may include various base stations 102 and various UEs 104. The base station 102 may include a macro cell (high power cellular base station) and/or a small cell (low power cellular base station), where the macro cell may include an evolved node B (eNB), where the wireless communication system 100 corresponds to an LTE network or G B node (gNB), where the wireless communication system 100 corresponds to a 5G network or a combination of both, and the small cell may include a femtocell, a picocell, a microcell, etc.

The base stations 102 may collectively form a RAN and interface with an Evolved Packet Core (EPC) or Next Generation Core (NGC) over a backhaul link. Base station 102 may perform functions related to, among other functions, communicating user data, radio channel ciphering and ciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, distribution of non-access stratum (NAS) messages, NAS node selection, synchronization, RAN sharing, Multimedia Broadcast Multicast Service (MBMS), subscriber and equipment tracking, RAN Information Management (RIM), paging, localization, and delivery of alert messages. The base stations 102 may communicate with each other directly or indirectly over backhaul links 134 (e.g., through the EPC/NGC), which backhaul links 134 may be wired or wireless.

The base station 102 may communicate wirelessly with the UE 104. Each base station 102 may provide communication coverage for a respective geographic coverage area 110. In an aspect, although not shown in fig. 1, the geographic coverage area 110 may be subdivided into multiple cells (e.g., three) or sectors, each cell corresponding to a single antenna or antenna array of the base station 102. As used herein, the term "cell" or "sector" can correspond to one of multiple cells of base station 102 or base station 102 itself, depending on the context.

While neighboring macro cell geographic coverage areas 110 may partially overlap (e.g., in a handover region), some geographic coverage areas 110 may be substantially overlapped by larger geographic coverage areas 110. For example, the small cell base station 102 'may have a geographic coverage area 110' that substantially overlaps the geographic coverage area 110 of one or more macro cell base stations 102. A network that includes both small cells and macro cells may be referred to as a heterogeneous network. The heterogeneous network may also include a home enb (HeNB) that may provide services to a restricted group referred to as a Closed Subscriber Group (CSG). The communication link 120 between base station 102 and UE 104 may include Uplink (UL) (also known as reverse link) transmissions from UE 104 to base station 102 and/or Downlink (DL) (also known as forward link) transmissions from base station 102 to UE 104. The communication link 120 may use MIMO antenna techniques including spatial multiplexing, beamforming, and/or transmit diversity. These communication links may be over one or more carriers. The allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated to DL than UL).

The wireless communication system 100 may further include a Wireless Local Area Network (WLAN) Access Point (AP)150 in communication with a WLAN Station (STA)152 via a communication link 154 in an unlicensed spectrum (e.g., 5 GHz). When communicating in the unlicensed spectrum, the WLAN STA 152 and/or the WLAN AP 150 may perform a Clear Channel Assessment (CCA) to determine whether the channel is available prior to communicating.

The small cell base station 102' may operate in licensed and/or unlicensed spectrum. When operating in unlicensed spectrum, the small cell base station 102' may employ LTE or 5G technology and use the same 5GHz unlicensed spectrum as used by the WLAN AP 150. A small cell base station 102' employing LTE/5G in unlicensed spectrum may boost coverage and/or increase capacity of an access network. LTE in unlicensed spectrum may be referred to as LTE unlicensed (LTE-U), Licensed Assisted Access (LAA), or

Extremely High Frequencies (EHF) are part of the RF in the electromagnetic spectrum. The EHF has a range of 30GHz to 300GHz and a wavelength between 1 millimeter and 10 millimeters. Radio waves in this frequency band may be referred to as millimeter waves. Near mmW can extend down to frequencies of 3GHz and wavelengths of 100 mm. The ultra-high frequency (SHF) band extends between 3GHz to 30GHz, which is also known as a centimeter wave. Communications using the mmW/near mmW radio frequency band have high path loss and relatively short range. The wireless communication system 100 may further include a mmW base station 180, the mmW base station 180 operable in mmW frequencies and/or near mmW frequencies to be in communication with the UE 182. The mmW base station 180 may utilize beamforming 182 with the UE 182 to compensate for the very high path loss and short range. Further, it is to be appreciated that in alternative configurations, one or more base stations 102 may also transmit using mmW or near mmW and beamforming. Accordingly, it will be appreciated that the foregoing is merely an example and should not be construed as limiting the various aspects disclosed herein.

The wireless communication system 100 may further include one or more UEs, such as UE 190, indirectly connected to one or more communication networks via one or more device-to-device (D2D) peer-to-peer (P2P) links. In the example of fig. 1, the UE 190 has a D2D P2P link 192 with one of the UEs 104 connected to one of the base stations 102 (e.g., the UE 190 may indirectly obtain cellular connectivity through therebetween), and a D2D P2P link 194 with the WLAN STAs 152 connected to the WLAN AP 150 (the UE 190 may indirectly obtain WLAN-based internet connectivity through therebetween). In an example, the D2D P2P link 192-194 may use any well-known D2D Radio Access Technology (RAT), such as LTE-direct (LTE-D), WiFi-direct (WiFi-D), or,Etc.) to support.

According to various aspects, fig. 2A illustrates an example wireless network structure 200. For example, the NGC 210 may be functionally viewed as a control plane function 214 (e.g., UE registration, authentication, network access, gateway selection, etc.) and a user plane function 212 (e.g., UE gateway function, access to a data network, Internet Protocol (IP) routing, etc.) that operate cooperatively to form a core network. A user plane interface (NG-U)213 and a control plane interface (NG-C)215 connect the gNB 222 to the NGC 210, in particular to the control plane functions 214 and the user plane functions 212. In an additional configuration, the eNB 224 may also connect to the NGC 210 via the NG-C215 to connect to the control plane functions 214 and to the NGC 210 via the NG-U213 to connect to the user plane functions 212. Further, eNB 224 may communicate directly with the gNB 222 via backhaul connection 223. Accordingly, in some configurations, the new RAN 220 may have only one or more gnbs 222, while other configurations include one or more of enbs 224 and gnbs 222. The gNB 222 or eNB 224 may communicate with a UE 240 (e.g., any UE depicted in fig. 1, such as UE 104, UE 182, UE 190, etc.). Another optional aspect may include a location server 230 that may be in communication with the NGC 210 to provide location assistance for the UE 240. Location server 230 may be implemented as a plurality of structurally separate servers or, alternatively, may each correspond to a single server. The location server 230 may be configured to support one or more location services for the UE 240, the UE 240 being able to connect to the location server 230 via the core network, the NGC 210, and/or via the internet (not illustrated). Further, the location server 230 may be integrated into a component of the core network or alternatively may be external to the core network.

According to various aspects, fig. 2B illustrates another example wireless network structure 250. For example, the NGC 260 (also referred to as a "5 GC") may be functionally considered a control plane function provided by an access and mobility management function (AMF)/User Plane Function (UPF)264, and a user plane function provided by a Session Management Function (SMF)262, which operate cooperatively to form a core network (i.e., the NGC 260). User plane interface 263 and control plane interface 265 connect eNB 224 to NGC 260, and in particular to SMF 262 and AMF/UPF 264, respectively. In an additional configuration, the gNB 222 may also be connected to the NGC 260 via a control plane interface 265 to the AMF/UPF 264 and a user plane interface 263 to the SMF 262. Further, eNB 224 may communicate directly with gNB 222 via backhaul connection 223, whether with or without gNB direct connectivity with NGC 260. In some configurations, the new RAN 220 may have only one or more gnbs 222, while other configurations include one or more of both enbs 224 and gnbs 222. The gNB 222 or eNB 224 may communicate with a UE 204 (e.g., any UE depicted in fig. 1). The base stations of the new RAN 220 communicate with the AMF side of the AMF/UPF 264 over an N2 interface and with the UPF side of the AMF/UPF 264 over an N3 interface.

The functions of the AMF include registration management, connection management, reachability management, mobility management, lawful interception, transmission of Session Management (SM) messages between the UE 204 and the SMF 262, transparent proxy service for routing SM messages, access authentication and access authorization, transmission of Short Message Service (SMs) messages between the UE 204 and a Short Message Service Function (SMSF) (not shown), and security anchor functionality (SEAF). The AMF also interacts with an authentication server function (AUSF) (not shown) and the UE 204 and receives intermediate keys established as a result of the UE 204 authentication procedure. In case of authentication based on UMTS (universal mobile telecommunications system) subscriber identity module (USIM), the AMF retrieves security material from the AUSF. The functions of the AMF also include Secure Context Management (SCM). The SCM receives keys from the SEAF, which are used by the SCM to derive access network-specific keys. The functionality of the AMF also includes location service management for administrative services, transmission of location service messages between the UE 204 and the Location Management Function (LMF)270 and between the new RAN 220 and the LMF 270, Evolved Packet System (EPS) bearer identifier allocation for interworking with EPS, and UE 204 mobility event notification. In addition, the AMF also supports the functionality of non-3 GPP access networks.

The functions of the UPF include: serving as an anchor point for intra-RAT/inter-RAT mobility (when applicable), serving as an external Protocol Data Unit (PDU) session point interconnected to a data network (not shown), providing packet routing and forwarding, packet inspection, user plane policy rule enforcement (e.g., gating, redirection, traffic steering), lawful interception (user plane collection), traffic usage reporting, quality of service (QoS) handling for the user plane (e.g., UL/DL rate enforcement, reflective QoS tagging in DL), UL traffic verification (service data flow (SDF) to QoS flow mapping), transport level packet tagging in UL and DL, DL packet buffering and DL data notification triggering, and sending and forwarding one or more "end markers" to the source RAN node.

The functions of the SMF 262 include session management, UE Internet Protocol (IP) address assignment and management, selection and control of user plane functions, configuration of traffic steering at the UPF for routing traffic to the correct destination, control of the policy enforcement and QoS components, and downlink data notification. The interface through which SMF 262 communicates with the AMF side of AMF/UPF 264 is referred to as the N11 interface.

Another optional aspect may include an LMF 270 that may be in communication with the NGC 260 to provide location assistance for the UE 204. LMFs 270 may be implemented as a plurality of separate servers (e.g., physically separate servers, different software modules on a single server, different software modules that extend across multiple physical servers, etc.), or alternatively may each correspond to a single server. LMF 270 may be configured to support one or more location services for UE 204, UE 240 being able to connect to LMF 270 via a core network, NGC 260, and/or via the internet (not illustrated).

According to various aspects, fig. 3 illustrates an example base station 310 (e.g., eNB, gNB, small cell AP, WLAN AP, etc.) in communication with an example UE 350 in a wireless network, in accordance with various aspects of the present disclosure. Base station 310 may correspond to any base station described herein. In the DL, IP packets from the core network (NGC 210/EPC 260) may be provided to the controller/processor 375. Controller/processor 375 implements functionality for a Radio Resource Control (RRC) layer, a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, and a Medium Access Control (MAC) layer. Controller/processor 375 provides RRC layer functionality associated with measurement configuration for broadcast system information (e.g., Master Information Block (MIB), System Information Blocks (SIBs)), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter-RAT mobility, and UE measurement reporting; PDCP layer functionality associated with header compression/decompression, security (ciphering, integrity protection, integrity verification), and handover support functions; RLC layer functionality associated with delivery of upper layer Packet Data Units (PDUs), error correction by automatic repeat request (ARQ), concatenation, segmentation and reassembly of RLC Service Data Units (SDUs), re-segmentation of RLC data PDUs, and re-ordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, scheduling information reporting, error correction, priority handling, and logical channel prioritization.

The Transmit (TX) processor 316 and the Receive (RX) processor 370 implement layer-1 functionality associated with various signal processing functions. Layer-1, which includes the Physical (PHY) layer, may include error detection on the transport channel, Forward Error Correction (FEC) encoding/decoding of the transport channel, interleaving, rate matching, mapping onto the physical channel, modulation/demodulation of the physical channel, and MIMO antenna processing. The TX processor 316 processes the mapping to the signal constellation based on various modulation schemes (e.g., Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), M-phase shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to Orthogonal Frequency Division Multiplexed (OFDM) subcarriers, multiplexed with reference signals (e.g., pilots) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to generate a physical channel carrying a time-domain OFDM symbol stream. The OFDM stream is spatially precoded to produce a plurality of spatial streams. The channel estimates from channel estimator 374 may be used to determine coding and modulation schemes and for spatial processing. The channel estimate may be derived from a reference signal transmitted by the UE 350 and/or channel condition feedback. Each spatial stream can then be provided to a TX MIMO processor (described further below with reference to fig. 7) and from there to one or more different antennas 320 via a separate transmitter 318 a. Each transmitter 318a may modulate an RF carrier with a respective individual spatial stream for transmission.

At the UE 350, each receiver 354a receives a signal through its respective antenna 352. Each receiver 354a recovers information modulated onto an RF carrier and provides the information to RX processor 356. The TX processor 368 and the RX processor 356 implement layer-1 functionality associated with various signal processing functions. The RX processor 356 may perform spatial processing on the information to recover any spatial streams destined for the UE 350. If multiple spatial streams are destined for the UE 350, they may be combined into a single OFDM symbol stream by the RX processor 356. RX processor 356 then transforms the OFDM symbol stream from the time-domain to the frequency-domain using a Fast Fourier Transform (FFT). The frequency domain signal includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, as well as the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the base station 310. These soft decisions may be based on channel estimates computed by channel estimator 358. These soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the base station 310 on the physical channel. These data and control signals are then provided to a controller/processor 359 that implements layer-3 and layer-2 functionality.

The controller/processor 359 can be associated with memory 360 that stores program codes and data. Memory 360 may be referred to as a non-transitory computer-readable medium. In the UL, the controller/processor 359 provides demultiplexing between transport and logical channels, packet reassembly, cipher interpretation, header decompression, and control signal processing to recover IP packets from the core network. The controller/processor 359 is also responsible for error correction.

Similar to the functionality described in connection with the DL transmission by base station 310, controller/processor 359 provides RRC layer functionality associated with system information (e.g., MIB, SIB) acquisition, RRC connection, and measurement reporting; PDCP layer functionality associated with header compression/decompression and security (ciphering, integrity protection, integrity verification); RLC layer functionality associated with delivery of upper layer PDUs, error correction by ARQ, concatenation, segmentation and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and re-ordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing MAC SDUs onto Transport Blocks (TBs), demultiplexing MAC SDUs from TBs, scheduling information reporting, error correction by hybrid automatic repeat request (HARQ), priority handling, and logical channel prioritization.

Channel estimates, derived by a channel estimator 358 from reference signals or feedback transmitted by base station 310, may be used by TX processor 368 to select appropriate coding and modulation schemes, as well as to facilitate spatial processing. The spatial streams generated by TX processor 368 may be provided to an optional TX MIMO processor (described further below) and from there to different antennas 352 via separate transmitters 354 b. Each transmitter 354b may modulate an RF carrier with a respective spatial stream for transmission. In an aspect, the transmitter 354b and the receiver 354a may be one or more transceivers, one or more discrete transmitters, one or more discrete receivers, or any combination thereof.

UL transmissions are processed at the base station 310 in a manner similar to that described in connection with receiver functionality at the UE 350. Each receiver 318b receives a signal through its respective antenna 320. Each receiver 318b recovers information modulated onto an RF carrier and provides the information to RX processor 370. In an aspect, the transmitter 318a and receiver 318b may be one or more transceivers, one or more discrete transmitters, one or more discrete receivers, or any combination thereof.

The controller/processor 375 can be associated with a memory 376 that stores program codes and data. Memory 376 may be referred to as a non-transitory computer-readable medium. In the UL, the controller/processor 375 provides demultiplexing between transport and logical channels, packet reassembly, cipher interpretation, header decompression, control signal processing to recover IP packets from the UE 304. IP packets from controller/processor 375 may be provided to a core network. The controller/processor 375 is also responsible for error correction.

Fig. 4 illustrates an example wireless communication system 400 in accordance with various aspects of the disclosure. In the example of fig. 4, the UE 404 (which may correspond to any of the UEs described above with respect to fig. 1 (e.g., UE 104, UE 182, UE 190, etc.)) is attempting to compute an estimate of the location of the UE 404, or assists another entity (e.g., a base station or core network component, another UE, a location server, a third party application, etc.) in computing the estimate of the location of the UE 404. The UE 404 may wirelessly communicate with multiple base stations 402a-d (collectively referred to as base stations 402) using RF signals and standardized protocols for modulating the RF signals and exchanging packets of information, the base stations 402 may correspond to any combination of base stations 102 or 180 and/or WLAN AP 150 in fig. 1. By extracting different types of information from the exchanged RF signals and utilizing the layout of the wireless communication system 400 (i.e., the locations, geometries, etc. of the base stations 402), the UE 404 can determine its location, or assist in determining its location in a predefined reference coordinate system. In an aspect, the UE 404 may specify its location using a two-dimensional coordinate system; however, aspects disclosed herein are not so limited, and may also be applicable to determining a position fix using a three-dimensional coordinate system where additional dimensions are desired. Additionally, although fig. 4 illustrates one UE 404 and four base stations 402, there may be more UEs 404 and more or fewer base stations 402, as will be appreciated.

As used herein, a "network node" may be a base station 402, a cell of the base station 402, a remote radio head, an antenna of the base station 402, wherein the antenna location of the base station 402 is different from the location of the base station 402 itself or any other network entity capable of transmitting reference RF signals. Further, as used herein, a "node" may refer to a network node or a UE.

The term "base station" may refer to multiple physical transmission points where a single physical transmission point may or may not be co-located. For example, where the term "base station" refers to a single physical transmission point, the physical transmission point may be a base station antenna corresponding to a cell of a base station (e.g., base station 402). Where the term "base station" refers to a plurality of co-located physical transmission points, the physical transmission points may be an antenna array of the base station (e.g., as in a MIMO system or where beamforming is employed by the base station). In case the term "base station" refers to a plurality of non-co-located physical transmission points, the physical transmission points may be Distributed Antenna Systems (DAS) (a network of spatially separated antennas connected to a common source via a transmission medium) or Remote Radio Heads (RRHs) (remote base stations connected to a serving base station). Alternatively, the non-collocated physical transmission point may be a serving base station that receives a measurement report from a UE (e.g., UE 404) and a neighbor base station for which the UE is measuring its reference RF signal. Thus, fig. 4 illustrates an aspect in which base stations 402a and 402b form a DAS/RRH 420. For example, base station 402a may be a serving base station for UE 404, and base station 402b may be a neighbor base station for UE 404. As such, base station 402b may be the RRH of base station 402 a. The base stations 402a and 402b may communicate with each other over a wired or wireless link 422.

A location server (e.g., location server 230) may transmit assistance data to UE 404, the assistance data including: an identification of one or more neighbor cells of the base station 402, and configuration information for the reference RF signals transmitted by each neighbor cell. Alternatively, the assistance data may originate directly from each base station 402 itself (e.g., in an overhead message that is periodically broadcast, etc.). Alternatively, the UE 404 may detect the neighbor cells of the base station 402 itself without using assistance data. As further described herein, the UE 404 (e.g., based in part on assistance data, if provided) may measure and (optionally) report RTTs between itself and individual network nodes. Using these measurements and the known locations of the measured network nodes (i.e., the base station(s) 402 or antenna(s) that transmitted the reference RF signal measured by the UE 404), the UE 404 or location server may determine the distance between the UE 404 and the measured network nodes and calculate the location of the UE 404 therefrom.

The term "location estimate" is used herein to refer to an estimate of the location of a UE (e.g., UE 404), which may be geographic (e.g., may include latitude, longitude, and possibly altitude) or municipal (e.g., may include a street address, a building designation, or an exact point or area within or near a building or street address, such as a particular entrance to a building, a particular room or suite in a building, or a landmark, such as a civic square). The position estimate may also be referred to as "position," "fix," "position estimate," "fix estimate," or some other terminology. The manner in which the position estimate is obtained may be generally referred to as "positioning," addressing, "or" position-locking. A particular solution for obtaining a location estimate may be referred to as a "location solution". The particular method for obtaining a location estimate as part of a location solution may be referred to as a "location method," or as a "location method. The location estimate may include an expected error or uncertainty (e.g., by including an area or volume in which the location is expected to be included with some specified or default confidence).

To support position estimation, the base stations 402 may be configured to broadcast reference RF signals (e.g., Positioning Reference Signals (PRS), cell-specific reference signals (CRS), channel state information reference signals (CSI-RS), Narrowband Reference Signals (NRS), synchronization signals, etc.) to UEs 404 in their coverage areas to enable the UEs 404 to measure RTT between the UEs 404 and the transmitting base station 402. In general, the beam of interest for RTT measurement is a LOS beam, or a beam that excites the shortest RF path (which may be a LOS beam or an NLOS beam that follows the shortest path to the receiver).

However, RF signals not only travel along the LOS/shortest NLOS path between the transmitting and receiving parties, but also on several other paths, as the RF signals spread out from the transmitting party and are reflected by other objects (such as hills, buildings, water, etc.) on their way to the receiving party. Thus, fig. 4 illustrates several LOS paths 410 and several NLOS paths 412 between the base station 402 and the UE 404. In particular, fig. 4 illustrates base station 402a transmitting on LOS path 410a and NLOS path 412a, base station 402b transmitting on LOS path 410b and two NLOS paths 412b, base station 402c transmitting on LOS path 410c and NLOS path 412c, and base station 402d transmitting on two NLOS paths 412 d. As illustrated in fig. 4, each NLOS path 412 is reflected by some object 430 (e.g., a building). As will be appreciated, each LOS path 410 and NLOS path 412 transmitted by the base station 402 can be transmitted by different antennas of the base station 402 (e.g., as in a MIMO system), or can be transmitted by the same antenna of the base station 402 (thereby illustrating propagation of RF signals). Furthermore, as used herein, the term "LOS path" refers to the shortest path between the transmitter and the receiver, and may not be the actual LOS path but the shortest NLOS path.

In an aspect, one or more base stations 402 may be configured to transmit RF signals using beamforming. In this case, some of the available beams may focus the transmitted RF signal along the LOS path 410 (e.g., these beams produce the highest antenna gain along the LOS path), while other available beams may focus the transmitted RF signal along the NLOS path 412. A beam with high gain along a particular path and thus focusing the RF signal along that path may still propagate some RF signal along other paths; the strength of the RF signal naturally depends on the beam gain along those other paths. The "RF signal" includes an electromagnetic wave that transmits information through a space between a transmitting side and a receiving side. As used herein, a transmitting party may transmit a single "RF signal" or multiple "RF signals" to a receiving party. However, as described further below, due to the propagation characteristics of the various RF signals through the multipath channel, the receiver may receive multiple "RF signals" corresponding to each transmitted RF signal.

In the case where the base station 402 uses beamforming to transmit RF signals, the beam of interest for data communications between the base station 402 and the UE 404 will be the beam carrying the RF signal that reaches the UE 404 with the highest signal strength (as indicated by, for example, Received Signal Received Power (RSRP) or SINR in the presence of directional interference signals), while the beam of interest for location estimation will be the beam carrying the RF signal that excites the shortest path or LOS path (e.g., LOS path 410). In some frequency bands and for commonly used antenna systems, these beams will be the same beams. However, in other frequency bands (such as mmW), where a large number of antenna elements may typically be used to create a narrow transmit beam, they may not be the same beam. That is, in some cases, the signal strength of the RF signal on the LOS path 410 may be weaker (e.g., due to an obstruction) than the signal strength of the RF signal on the NLOS path 412, which arrives later on the NLOS path 412 due to propagation delay.

Fig. 5A illustrates a structure of an example LTE subframe sequence 500 with PRS positioning occasions. The subframe sequence 500 may be applicable to broadcast of PRS signals from base stations (e.g., any of the base stations described above) or other network nodes. Although fig. 5A provides an example of a subframe sequence for LTE, similar subframe sequence implementations may be implemented for other communication technologies/protocols (such as 5G and NR). In fig. 5A, time is represented horizontally (e.g., on the X-axis), where time increases from left to right, and frequency is represented vertically (e.g., on the Y-axis), where frequency increases (or decreases) from bottom to top. As shown in fig. 5A, the downlink and uplink LTE radio frames 510 may each have a duration of 10 milliseconds (ms). For a downlink Frequency Division Duplex (FDD) mode, in the illustrated example, the radio frame 510 is organized into ten subframes 512 each of 1ms duration. Each subframe 512 includes two slots 514, each having, for example, a 0.5ms duration.

In the frequency domain, the available bandwidth may be divided into evenly spaced orthogonal subcarriers 516 (also referred to as "tones" or "bins"). For example, for a normal length Cyclic Prefix (CP) using, for example, a 15kHz spacing, subcarriers 516 may be grouped to have tenA group of two (12) subcarriers. The resources of one OFDM symbol length in the time domain and one subcarrier in the frequency domain, represented as a block of the subframe 512, are referred to as Resource Elements (REs). Each grouping of 12 subcarriers 516 and 14 OFDM symbols is referred to as a Resource Block (RB) or Physical Resource Block (PRB), and in the above example, the number of subcarriers in a resource block may be written asFor a given channel bandwidth, the number of available resource blocks on each channel 522 (which is also referred to as the transmission bandwidth configuration 522) is represented asFor example, for the 3MHz channel bandwidth in the example above, the number of available resource blocks per channel 522 is determined byIt is given.

The base station may transmit a radio frame (e.g., radio frame 510) or other physical layer signaling sequence supporting PRS signals (i.e., Downlink (DL) PRS) according to a frame configuration similar to or the same as the frame configuration shown in fig. 5A, which may be measured and used for UE (e.g., any of the UEs described above) position determination. Other types of wireless nodes (e.g., DAS, RRHs, UEs, APs, etc.) in a wireless communication network may also be configured to transmit PRS signals configured in a manner similar (or identical) to that depicted in fig. 5A.

The PRS, which has been defined in 3GPP LTE Release 9 and later, may be located by the base station (e.g., by operation and maintenance (O)&M) the server) transmits in the wireless communication network just after the adaptation. PRSs may be transmitted in special positioning subframes grouped into positioning occasions. For example, in LTE, PRS positioning occasions may include a number N_PRSA number N of consecutive positioning subframes_PRSMay be between 1 and 160 (e.g., values 1, 2, 4, and 6, and other values may be included). PRS positioning occasions for cells supported by base stations may be periodically spaced (by a number T)_PRSAt intervals of one millisecond (or subframe)Mark) occurs, wherein T_PRSMay be equal to 5, 10, 20, 40, 80, 160, 320, 640, or 1280 (or any other appropriate value). As an example, fig. 5A illustrates the periodicity of positioning occasions, where N is_PRSEqual to 4(518), and T_PRSGreater than or equal to 20 (520). In some aspects, T_PRSIt can be measured in terms of the number of subframes between the start of each consecutive positioning occasion.

Within each positioning time, PRSs may be transmitted at a constant power. PRSs may also be transmitted at zero power (i.e., muted). Muting of regularly scheduled PRS transmissions may be useful when PRS signals between different cells overlap by occurring at or near the same time. In this case, PRS signals from some cells may be muted while PRS signals from other cells are transmitted (e.g., at a constant power). Muting can assist a UE in signal acquisition and time of arrival (TOA) and RSTD measurements of non-muted PRS signals (by avoiding interference from PRS signals that have been muted). Muting can be considered as not transmitting PRSs for a given positioning occasion of a particular cell. The bit string may be used to signal (e.g., using LTE Positioning Protocol (LPP)) a muting pattern (also referred to as a muting sequence) to the UE. For example, in a bit string signaled to indicate a muting pattern, if the bit at position j is set to '0', the UE can infer that the PRS is muted for the jth positioning occasion.

To further improve the audibility of PRSs, the positioning subframes may be low-interference subframes transmitted without user data channels. As a result, in a perfectly synchronized network, the PRS may be subject to interference from PRS of other cells with the same PRS pattern index (i.e., with the same frequency shift), but not from data transmissions. The frequency shift is defined, for example, in LTE as a function of PRS ID for a cell or other Transmission Point (TP) (denoted as) Or a function of the Physical Cell Identifier (PCI) if no PRS ID is assigned (denoted as) Which results in an effective frequency reuse factor of six (6).

To also improve the audibility of the PRS (e.g., when the PRS bandwidth is limited such as to have only 6 resource blocks corresponding to a 1.4MHz bandwidth), the frequency band for consecutive PRS positioning occasions (or consecutive PRS subframes) may be changed via frequency hopping in a known and predictable manner. In addition, a cell supported by a base station may support more than one PRS configuration, where each PRS configuration may include a specific frequency offset (vshift), a specific carrier frequency, a specific bandwidth, a specific code sequence, and/or have a specific number of subframes per positioning occasion (N)_PRS) And a specific periodicity (T)_PRS) The PRS positioning timing specific sequence of (a). In some implementations, one or more PRS configurations supported in a cell may be used for directional PRSs and may then have additional specific characteristics (such as specific transmission directions, specific horizontal angular ranges, and/or specific vertical angular ranges). Further enhancements to PRS may also be supported by base stations.

To assist in positioning operations, OTDOA assistance data for a "reference cell" and one or more "neighbor cells" or "neighboring cells" relative to the "reference cell" may be provided to the UE by a location server (e.g., location server 230). For example, the assistance data may provide a center channel frequency for each cell, various PRS configuration parameters (e.g., N)_PRS、T_PRSA muting sequence, a hopping sequence, a PRS ID, a PRS bandwidth), a cell global ID, PRS signal characteristics associated with directional PRS, and/or other cell-related parameters applicable for OTDOA or some other location method. PRS based positioning by a UE may be facilitated by indicating a serving cell for the UE in OTDOA assistance data (e.g., where a reference cell is indicated as the serving cell).

In some cases, the OTDOA assistance data may also include an "expected RSTD" parameter along with an uncertainty of the expected RSTD parameter, which provides the UE with information about the RSTD value that the UE expects to be measured at the current location between the reference cell and each neighbor cell. The expected RSTD along with the associated uncertainty may define a search window for the UE within which the UE is expected to measure the RSTD value. The OTDOA assistance information may also include PRS configuration information parameters that allow the UE to determine when a PRS positioning occasion occurs on a signal received from a respective neighbor cell relative to a PRS positioning occasion for a reference cell and to determine PRS sequences transmitted from the respective cells in order to measure the signal TOA or RSTD.

The location of the UE may be calculated (e.g., by the UE or a location server) using RSTD measurements, known absolute or relative transmission timing of each cell, and known location(s) of the wireless node physical transmit antenna for the reference cell and the neighboring cells. More specifically, the RSTD of the neighbor cell k relative to the reference cell Ref may be given as (TOA)_k-TOA_Ref) Wherein the TOA value may be measured modulo the duration of one subframe (1ms) to remove the effect of measuring different subframes at different times. The TOA measurements for different cells may then be converted to RSTD measurements (e.g., as defined in 3GPP TS 36.214 entitled "physical layer; measurement") and sent by the UE to the location server. The location of the UE may be determined by using (i) RSTD measurements, (ii) known absolute or relative transmission timing of each cell, (iii) known location(s) for physical transmit antennas of the reference cell and neighboring cells, and/or (iv) directional PRS characteristics such as direction of transmission.

In LTE, PRSs are transmitted using "antenna port 6" with a particular bandwidth and pattern. The mapping of PRSs to Resource Elements (REs) is shown in fig. 5B for a normal cyclic prefix and one or two transmit antenna ports. Fig. 5B illustrates a subframe 512 of 12 subcarriers over 14 OFDM symbols. Each box in fig. 5B indicates an RE having a frequency domain index k and a time domain index. Subframe 512 is marked with "R₆"indicates PRS RE.

In LTE, antenna ports do not correspond to physical antennas, but are logical entities distinguished by their reference signal sequences. Thus, multiple antenna port signals may be transmitted on a single transmit antenna, and a single antenna port may be extended across multiple transmit antennas. However, in some cases (such as MIMO systems), each antenna port signal may be transmitted on a separate physical antenna to create spatial diversity between the paths. Table 1 shows a mapping between the types of downlink LTE reference signals and the antenna ports used by them. As shown in table 1, PRS in LTE uses antenna port 6.

TABLE 1

Referring back to fig. 5B, the UE may process all REs on the bandwidth jointly and perform an inverse fourier transform to convert the received signal to the time domain and thereby identify the earliest path on the channel. The UE creates a Channel Energy Response (CER), the graph 600 of which is illustrated in fig. 6 and identifies the earliest peak. As illustrated in fig. 6, the UE detects a first CER peak at ToA1, a second CER peak at ToA2, and a third CER peak at ToA 3. The first CER peak detected at ToA1 corresponds to the earliest arriving reference RF signal. Thus, the received reference RF signal corresponding to the CER peak at ToA1 is assumed to follow the LOS path.

ToA T at UE for shortest path from cell i_iIs represented as:

wherein tau is_iIs the sum of the transmission time from cell i, the NLOS transmission time and the UE timing measurement noise, D_iIs a position (q)_i) Bee ofThe euclidean distance between cell i and the UE at location (p), and c is the speed of light in air (i.e., 299,700 km/s). It can be assumed that the cell location qi is known through the cell information database. The PRS can be used to estimate T_i。

The following is an equation for calculating the euclidean distance:

where D is the distance between two points on the surface of the earth, R is the radius of the earth (i.e., 6371km),andrespectively, the latitude of the first point (in radians) and the latitude of the second point (in radians), and β₁And beta₂Respectively the longitude (in radians) of the first point and the latitude (in radians) of the second point.

As mentioned above, the 5G NR implementation is designed to significantly enhance the spectral efficiency of mobile communications compared to the current 4G/LTE standard. Furthermore, the signaling efficiency should be improved and the latency should be reduced substantially compared to the current standard. In particular, there are several design goals with reference to the positioning reference signal in 5G, sometimes referred to as the Navigation Reference Signal (NRS). For example, NRS should allow a receiving party (e.g., UE) to take accurate measurements that are robust to multipath. NRS should be able to provide navigation and positioning support (such as range, pseudorange and angle measurements for positioning, and doppler measurements for velocity estimation and navigation). Another design goal is that the NRS should also have a uniform and independent signal structure that allows for independence of Cyclic Prefix (CP), antenna port number, and native symbol length, which can be supported by service multiplexing. Additionally, only NRS should be permitted within the NRS envelope, i.e., not intermixed with CRS, Tracking Reference Signals (TRS), Primary Synchronization Signals (PSS), Secondary Synchronization Signals (SSS), Physical Broadcast Channel (PBCH), etc. Yet another design goal is for the NRS to provide a higher level of orthogonality/isolation between cells, which will help to alleviate the "near-far" problem (the receiver needs to be able to distinguish between near-end and far-end transmitters; however, near-end transmitters may overpower far-end transmitters, especially when they are operating on the same channel, making it difficult or impossible for the receiver to receive far-end transmitters). Therefore, NRS should provide time-frequency orthogonality, code isolation, and antenna pattern isolation. Yet another design goal is that the NRS should require low power consumption at the receiver.

As mentioned above, to support position estimation in terrestrial wireless networks, a UE may be configured to measure and report OTDOA or RSTD between reference RF signals (e.g., PRSs, NRSs, etc.) received from two or more network nodes (e.g., different base stations or different transmission points (e.g., antennas) belonging to the same base station). In order to make OTDOA-based positioning accurate, the UE needs to be able to accurately estimate the LOS, or earliest path, of the channel. However, due to obstructions (e.g., hills, buildings, water, etc.), RF signals on the LOS path may be received at significantly lower power than RF signals on other NLOS paths and thus are essentially "hidden" from the UE. Thus, the UE may erroneously consider one of these NLOS paths to be an LOS path.

To better distinguish between LOS and NLOS paths, the present disclosure provides techniques for introducing frequency and/or time diversity for reference RF signals used for positioning, such as NRs in 5G NR. In an aspect, the reference RF signal may be transmitted with a different MIMO precoder in each frequency subband or in each time interval to enable a transmitting party (e.g., a base station) to adjust the CER measured at a receiving party (e.g., a UE) in an attempt to make detection of the earliest path of the channel easier and more robust. Using a frequency selective precoder may result in a strong NLOS path being smooth and a LOS path being more easily detected. More specifically, if the precoder in the frequency domain is adjusted, the corresponding time-domain impulse response of the channel will be convolved with the time-domain impulse response of the precoder. This may result in the NLOS path(s) being smoothed out to a greater extent than would occur for the LOS path. Thus, the NLOS path(s) may not be persistent when the precoder adjusts. The receiver can process each measurement independently in a constant precoder frequency/time region and keep track of the main RF signal path.

In conventional single-stream RF signal transmission, the same RF signal is transmitted from each transmit antenna with the appropriate weighting (phase and gain) so that the signal power is maximized at the receiving side. "precoding" is a technique that determines and applies appropriate weights to an RF signal stream based on channel conditions between the transmitting and receiving sides. Specifically, the transmitting side estimates channel conditions between itself and the receiving side, and determines a weight for each transmit antenna based on the estimated channel conditions. In this manner, precoding reduces the damaging effects of the communication channel.

Fig. 7 is a block diagram of an example transmitter 700 that precodes data for a multipath channel in accordance with aspects of the present disclosure. The transmitter 700 may correspond to a transmitter portion of the base station 310 or the UE 350 in fig. 3. Transmitter 700 includes a TX processor 710 (which may correspond to TX processor 316 or TX processor 368), among other components, that receives and processes traffic and pilot data to provide (up to) N_TA plurality of precoded symbol streams; and a TX MIMO processor 720, which preconditions the precoded symbol stream to provide (up to) N_TA stream of pre-conditioned symbols.

In the example of fig. 7, TX processor 710 includes a symbol mapping element 716 and a precoder 718.

Symbol mapping element 716 receives and multiplexes pilot data with the scrambled reference RF signal sequence and further symbol maps the multiplexed data according to one or more modulation schemes to provide modulation symbols. A separate modulation scheme may be used for each data stream or each group of one or more data streams. Alternatively, a common modulation scheme may be used for all data streams. Symbol mapping for each data stream may be achieved by: (1) grouping the multiplexed set of data bits to form non-binary symbols; and (2) applying each non-binary codeThe bins are mapped to points in the signal constellation corresponding to the modulation scheme selected for the data stream. Each mapped signal point corresponds to a modulation symbol. Symbol mapping element 716 provides a vector s (n) of modulation symbols for each symbol period n, where the number of modulation symbols in each vector is equal to the number of spatial subchannels to be used for that symbol period. Thus, symbol mapping element 716 provides (up to) N_TA stream of modulation symbols (i.e., a sequence of vectors of modulation symbols, wherein each vector comprises up to N_TOne modulation symbol).

To perform precoding at transmitter 700, the response of the MIMO channel may be estimated (e.g., by channel estimator 374 or channel estimator 358) and used to precode modulation symbols and to further precondition the precoded symbols prior to transmission over the MIMO channel. In an FDD system, the downlink and uplink are allocated different frequency bands, and the channel responses for the downlink and uplink may not be correlated to a sufficient degree. For FDD systems, the channel response may be estimated at the receiver and sent back to the transmitter. However, in a Time Division Duplex (TDD) system, the downlink and uplink share the same frequency band in a time division multiplexed manner, and there may be a high degree of correlation between downlink and uplink channel responses. Thus, for a TDD system, the transmitter 700 may estimate the uplink channel response (e.g., based on the pilot transmitted on the uplink by the receiver system) and derive the downlink channel response by accounting for the differences between the transmit and receive antenna arrays and front end processing. However, in some cases, there may not be an estimate of the MIMO channel that may be used to perform MIMO precoding. Alternatively, some predetermined or pseudo-random precoding selection may be used. For example, as described further herein, a certain precoder granularity, a Small Delay Cyclic Delay Diversity (SDCDD) parameter, a pseudo-random seed, a precoder cyclic ordering, or a precoder cyclic set may be used.

Precoder 718 receives and precodes the modulated symbol stream s (n) to provide a precoded symbol stream c (n). As further described herein, in the case where the RF signal to be transmitted is a reference signal, the precoder 718 may precode the reference signal for different subbands and/or for different time intervals. That is, different resources carrying reference RF signals may use different MIMO precoders and thus appear to be transmitted on different antenna ports. TX MIMO processor 720 then performs MIMO processing on the precoded symbol streams c (n) to orthogonalize the symbol streams at the receiving system (e.g., UE 350). As mentioned above, MIMO processing may be performed in the time domain or the frequency domain.

A convolver 722 receives and pre-modulates the precoded symbol stream c (n) with a pulse-shaping matrix (e.g., convolves the precoded symbol stream c (n) with the pulse-shaping matrix) to derive the transmitted signal vector x (n). Each element of transmitted signal vector x (n) corresponds to a stream of pre-conditioned symbols to be transmitted on a respective transmit antenna 732, which may correspond to transmit antenna 320 or transmit antenna 352. N is a radical of_TA stream of preconditioned symbols (i.e., a sequence of vectors of preconditioned symbols, with each vector including up to N_TOne preconditioned symbol) is also labeled N_TThe transmitted signal. N is a radical of_TThe stream of pre-conditioned symbols is provided to a transmitter 730 (which may correspond to transmitter 318a or transmitter 354b) and processed to derive N_TA modulated signal which is then converted from N_TEach antenna 732 transmits.

As mentioned above, the present disclosure provides techniques for selectively precoding reference RF signals for positioning (such as NRs in 5G NR) to introduce frequency and/or time diversity. As mentioned above, in LTE, PRSs are transmitted on antenna port 6, so each PRS will have the same MIMO precoder. However, in the techniques of this disclosure, a transmitter (e.g., TX processor 710) may configure reference RF signal resources for different subbands and/or different time intervals to make it appear as if they were transmitted on different antenna ports.

As used herein, a reference RF signal "resource" is a resource in a time-frequency grid (as illustrated in fig. 5A and 5B) that carries a reference RF signalA set of source elements. For example, in LTE, the reference RF signal resources for PRS will be the resource elements (labeled "R" in fig. 5B) that carry PRS in the subframe₆"). Thus, each resource element of the reference RF signal resource carries a reference RF signal. A "set" of reference RF signal resources refers to a set of such sets of resource elements that carry reference RF signals.

In an aspect, each reference RF signal resource or set of reference RF signal resources may use a different MIMO precoder and thus appear to be transmitted on a different antenna port than the other reference RF signal resources or sets of reference RF signal resources. Alternatively, each resource element of the reference RF signal resource may use a different MIMO precoder. The MIMO precoder may be different for each frequency subband and/or each time interval in which the reference RF signal resource (set) is configured. Because the MIMO precoders are different for each reference RF signal resource or set of reference RF signal resources, the receiving party (e.g., UE) cannot infer that a given reference RF signal resource (set) is on the same antenna port or is transmitting using the same MIMO precoder as another reference RF signal resource (set) unless they are being transmitted on the same subband or at the same time interval. The recipient may process all reference RF signals in the (set of) reference RF signal resources to determine which signal follows the LOS path.

As an example, the first set of four reference RF signal resources may carry four reference RF signals that appear to the receiving party to have been encoded by the first antenna port or the first MIMO precoder. The second set of four reference RF signal resources may carry four reference RF signals that appear to the receiving party to have been encoded by different antenna ports or different MIMO precoders. As another example, the first reference RF signal resource may have multiple resource elements that carry reference RF signals that each have been encoded by a different antenna port or a different MIMO precoder as viewed by the receiving party. The second reference RF signal resource may have the same configuration of resource elements carrying reference RF signals that appear to the receiving party to have each been encoded by the same antenna port or the same MIMO precoder as the resource elements in the first reference RF signal resource. That is, the resource elements that carry the reference RF signal in the reference RF signal resource will be encoded differently, but identically across multiple reference RF signal resources.

These techniques may be implemented in various ways. In one aspect, each positioning reference RF signal resource may have a configured precoder granularity (PRG), which may be equal to a wideband frequency (in which LTE operates), or a narrowband frequency value. In another aspect, each positioning reference RF signal resource can have a configured temporal coherence parameter that indicates whether the receiving side can assume that the antenna port used for the positioning reference RF signal resource is the same across OFDM symbols/slots within the temporal coherence parameter.

For example, if the temporal coherence parameter is four OFDM symbols, the receiving side may assume that the reference RF signals transmitted within a group of four symbols use the same antenna port/MIMO precoder, but cannot assume that the reference RF signals transmitted within a subsequent group of four symbols use the same antenna port/MIMO precoder as the first group of four symbols.

However, the receiver will be able to determine the LOS path using the reference RF signals in both symbol groups.

In yet another aspect, the receiver may be configured with multiple positioning reference RF signal resources on the same OFDM symbol but in disjoint subbands, and the receiver may report TDOA estimates after jointly processing these resources. These resources may belong to the same set of locations, and the receiver may report one TDOA estimate across that set. The receiver may also report which reference RF signal resource in the set was used among all RS resources in the set to derive the reported TDOA measurement. That is, the receiving party may determine which reference RF signal resource in the set has an LOS reference RF signal, use the reference RF signal to determine the TDOA, and report the reference RF signal resource to the transmitting party. The transmitter may then use the reference RF signal resource/MIMO precoder when transmitting reference RF signals to the receiver in the future.

In an aspect, precoder cycling or SDCDD may be used to transmit positioning reference RF signal resources. In SDCDD, one reference RF signal resource is transmitted with a first predetermined delay, a subsequent reference RF signal resource is transmitted with another predetermined delay, and so on. In this way, the recipient may be able to determine which uses the LOS path. For precoder cycling, the transmitting side uses a different precoder sequence for each of some cycles of precoding (e.g., four precoding), and then repeats. The receiver may be configured with reference resources and positioning reference RF signal resources, one of which is transmitted using an antenna port derived using a predefined precoder cycling method with respect to the reference resources. The reference resource may be a Synchronization Signal Block (SSB), CSI-RS, TRS, or another positioning reference RF signal resource.

In the above aspects, the receiving party may indicate a PRG, or a precoder cycling sequence, or a time delay to be applied to the SDCDD, or a number of different positioning reference RF signal resources in the reference RF signal resource set. The indication(s) of the receiver may be based on the receiver's capabilities with respect to PRG, precoder cycling sequence, time delay, etc. The indication(s) of the recipient may only be applicable in scenarios based on recipient-based positioning (where the recipient determines its own location) rather than recipient-assisted positioning (where a location server or other network entity determines the location of the recipient). In the case of receiver-assisted positioning, the receiver assumes that a wideband precoder is used for positioning the reference RF signal.

Note that although the foregoing description has generally described the transmitting party being a base station and the receiving party being a UE, it will be understood that the transmitting party may be a UE and the receiving party may be a base station, or both the transmitting party and the receiving party may be a UE or a base station.

Fig. 8 illustrates an example method 800 for transmitting reference signals for positioning estimation over a MIMO channel in accordance with at least one aspect of the present disclosure. The method 800 may be performed by a first node, such as a base station 310 or a UE 350 having a transmitter 700.

At 802, a first node 805 (e.g., TX processor 710 and/or TX MIMO processor 720) configures a first set of reference signal resources (of one or more reference signal resources) for transmitting a first set of reference signal(s). In an aspect, a first set of reference signal resources may occur on a first subband of a MIMO channel and/or during a first time interval on the MIMO channel. In an aspect, as described herein, each reference signal resource in the first set of reference signal resources can utilize at least a first MIMO precoder or a plurality of MIMO precoders (e.g., a different MIMO precoder for each reference signal resource). In an aspect, each reference signal resource in the first set of reference signal resources may utilize a first plurality of MIMO precoders (including a first MIMO precoder) that vary over time and/or frequency.

At 804, the first node 805 (e.g., the TX processor 710 and/or the TX MIMO processor 720) configures a second set of reference signal resources (of the one or more reference signal resources) for transmitting a second set of reference signal(s). In an aspect, a second set of reference signal resources may occur on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel. In an aspect, as described herein, each reference signal resource in the second set of reference signal resources can utilize at least a second MIMO precoder or a plurality of MIMO precoders (e.g., a different MIMO precoder for each reference signal resource). In an aspect, each reference signal resource in the second set of reference signal resources may utilize a second plurality of MIMO precoders (including a second MIMO precoder) that varies over time and/or frequency. In an aspect, the method 800 may further include receiving, at the first node 805, an indication of a number of reference signal resources to include in the first set of reference signal resources and the second set of reference signal resources from the second node.

In an aspect, the first plurality of MIMO precoders and the second plurality of MIMO precoders may vary over time and/or frequency for each reference signal resource in the first set of reference signal resources and the second set of reference signal resources based on the configured precoder granularity. In an aspect, the method 800 may further include receiving, at the first node 805, an indication of the configured precoder granularity from the second node.

In an aspect, the first plurality of MIMO precoders and the second plurality of MIMO precoders may vary over time and/or frequency for each of the first set of reference signal resources and the second set of reference signal resources based on the configured temporal coherence parameters. In an aspect, the method 800 may further include receiving, at the first node 805, an indication of the configured temporal coherence parameters from the second node.

In an aspect, the first and second plurality of MIMO precoders may vary over time and/or frequency for each of the first and second sets of reference signal resources based on the configured SDCDD. In an aspect, method 800 may further include receiving, at the first node 805, an indication of the configured SDCDD from the second node.

In an aspect, the first and second plurality of MIMO precoders may vary over time and/or frequency for each of the first and second sets of reference signal resources based on the configured precoder cycling sets and precoder cycling orderings. In an aspect, the method 800 may further include receiving, at the first node 805, an indication of the configured precoder cycling set and precoder cycling ordering from the second node.

At 806, the first node 805 (e.g., the antenna(s) 732, the transmitter(s) 730, the TX MIMO processor 720, and/or the TX processor 710) transmits a first set of reference signals over the MIMO channel to a second node (e.g., the other of the base station 310 or the UE 350) using a first set of reference signal resources over a first subband of the MIMO channel and/or during a first time interval over the MIMO channel.

At 808, the first node 805 (e.g., antenna(s) 732, transmitter(s) 730, TX MIMO processor 720 and/or TX processor 710) transmits a second set of reference signals to the second node over the MIMO channel using a second set of reference signal resources during a second time interval on a second subband and/or on the MIMO channel.

In an aspect, the first set of reference signal resources may comprise a plurality of reference signal resources on the same OFDM symbol in disjoint subbands of a MIMO channel. In an aspect, the method 800 may further comprise: the TDOA estimate is received at the first node 805 from the second node based at least in part on the first and second sets of reference signals transmitted on the first and second sets of reference signal resources, or a location estimate for the second node calculated at the first node 805 from the second node based at least in part on the first and second sets of reference signals transmitted on the first and second sets of reference signal resources. In an aspect, method 800 may further include receiving, at the first node 805 from the second node, identifiers of reference signal resources in the first and second sets of reference signal resources used to derive the TDOA estimate or the location estimate for the second node. In an aspect, the first node 805 transmits subsequent reference signals to the second node using the identified reference signal resources.

In an aspect, the first and second MIMO precoders used in each of the first and second subbands may be pseudo-randomly chosen MIMO precoders based on a cyclic set of MIMO precoders.

In an aspect, the method 800 may further include receiving, at the first node 805, a recommendation from the second node of a first MIMO precoder and a second MIMO precoder to be used for encoding the first and second sets of reference signal resources.

Fig. 9 illustrates an example method 900 for processing reference signals for position estimation over a MIMO channel. The method 900 may be performed by a second node, such as the base station 310 or the UE 350.

At 902, the second node 905 (e.g., antenna(s) 320, receiver(s) 318b, and/or RX processor 370, or antenna(s) 352, receiver(s) 354a, and/or RX processor 356) receives, from the first node (e.g., the other of base station 310 or UE 350), reference signal(s) of the first set of reference signal resources (of one or more reference signal resources). In an aspect, a first set of reference signal resources may occur on a first subband of a MIMO channel and/or during a first time interval on the MIMO channel. In an aspect, as described herein, each reference signal resource in the first set of reference signal resources can utilize at least a first MIMO precoder or a plurality of MIMO precoders (e.g., a different MIMO precoder for each reference signal resource). In an aspect, each reference signal resource in the first set of reference signal resources may utilize a first plurality of MIMO precoders (including a first MIMO precoder) that vary over time and/or frequency.

At 904, second node 905 (e.g., antenna(s) 320, receiver(s) 318b, and/or RX processor 370, or antenna(s) 352, receiver(s) 354a, and/or RX processor 356) receives, from the first node, a second set of reference signal(s) on a second set of reference signal resources (of one or more reference signal resources). In an aspect, a second set of reference signal resources may occur on a second subband of the MIMO channel and/or during a second time interval on the MIMO channel. In an aspect, as described herein, each reference signal resource in the second set of reference signal resources can utilize at least a second MIMO precoder or a plurality of MIMO precoders (e.g., a different MIMO precoder for each reference signal resource). In an aspect, each reference signal resource in the second set of reference signal resources may utilize a second plurality of MIMO precoders (including a second MIMO precoder) that varies over time and/or frequency.

At 906, the second node 905 (e.g., RX processor 370 and/or controller/processor 375, or RX processor 356 and/or controller/processor 359) identifies at least one reference signal transmitted on the first set of reference signal resources and the second set of reference signal resources as following a LOS path between the second node and the first node.

At 908, second node 905 (e.g., RX processor 370 and/or controller/processor 375, or RX processor 356 and/or controller/processor 359) performs TDOA measurements based on the at least one reference signal.

In an aspect, the method 900 may further include sending, by the second node 905, an indication of the configured precoder granularity to the first node, wherein the first plurality of MIMO precoders and the second plurality of MIMO precoders may vary over time and/or frequency for each reference signal resource in the first set of reference signal resources and the second set of reference signal resources based on the configured precoder granularity.

In an aspect, the method 900 may further include sending, by the second node 905, an indication of the configured temporal coherence parameter to the first node, wherein the first plurality of MIMO precoders and the second plurality of MIMO precoders may vary over time and/or frequency for each of the first set of reference signal resources and the second set of reference signal resources based on the configured temporal coherence parameter.

In an aspect, the method 900 may further include sending, by the second node 905, an indication of the configured SDCDD to the first node, wherein the first plurality of MIMO precoders and the second plurality of MIMO precoders may vary over time and/or frequency for each of the first set of reference signal resources and the second set of reference signal resources based on the configured SDCDD.

In an aspect, the method 900 may further include sending, by the second node 905, an indication of the configured precoder cycling set and precoder cycling ordering to the first node, wherein the first plurality of MIMO precoders and the second plurality of MIMO precoders may vary over time and/or frequency for each reference signal resource in the first reference signal resource set and the second reference signal resource set based on the configured precoder cycling set and precoder cycling ordering.

In an aspect, the method 900 may further include sending, by the second node 905, a recommendation to the first node of a number of reference signal resources to include in the first set of reference signal resources.

In an aspect, the method 900 may further include: transmitting, by the second node 905, to the first node, an identifier of a reference signal resource carrying the at least one reference signal used to derive a TDOA measurement or a location estimate for the second node, the TDOA measurement or the location estimate for the second node calculated based, at least in part, on the first and second sets of reference signals transmitted on the first and second sets of reference signal resources.

In an aspect, the method 900 may further include sending, by the second node 905, a recommendation to the first node of the first and second MIMO precoders to be used for encoding the first and second sets of reference signal resources.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Furthermore, those of skill in the art will appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the aspects disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the various aspects described herein.

The various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or other such configuration).

The methods, sequences and/or algorithms described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), flash memory, read-only memory (ROM), Erasable Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, a hard disk, a removable disk, a CD-ROM, or any other form of non-transitory computer-readable medium known in the art. An exemplary non-transitory computer readable medium may be coupled to the processor such that the processor can read information from, and write information to, the non-transitory computer readable medium. In the alternative, the non-transitory computer-readable medium may be integral to the processor. The processor and the non-transitory computer readable medium may reside in an ASIC. The ASIC may reside in a user equipment (e.g., UE) or a base station. Alternatively, the processor and the non-transitory computer readable medium may be discrete components in a user equipment or a base station.

In one or more exemplary aspects, the functions described herein may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a non-transitory computer-readable medium. Computer-readable media may include storage media and/or communication media including any non-transitory medium that can facilitate transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Any connection is properly termed a computer-readable medium. For example, if the software is implemented using coaxial cable, fiber optic cable, twisted pair, DSL, or a software interface such as infrared, radio, and microwaveSuch as a web site, server, or other remote source, a coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. The terms disk and disc, which may be used interchangeably herein, include Compact Disc (CD), laser disc, optical disc, Digital Video Disc (DVD), floppy disk anddisks, which often reproduce data magnetically and/or optically with a laser. Combinations of the above should also be included within the scope of computer-readable media.

While the foregoing disclosure shows illustrative aspects, those skilled in the art will appreciate that various changes and modifications may be made therein without departing from the scope of the disclosure as defined by the appended claims. Furthermore, those of skill in the art will appreciate that the functions, steps, and/or actions recited in any of the above-described methods and/or in any of the appended method claims need not be performed in any particular order, in accordance with the various illustrative aspects described herein. Still further, to the extent that any element is recited in the above description or in the appended claims in the singular, those skilled in the art will appreciate that the singular also contemplates the plural unless limitation to the singular is explicitly stated.

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