阅读说明：本技术 无线通信设备的调度 (Scheduling of wireless communication devices ) 是由 托马斯·尼尔松 罗科·迪塔兰托 列夫·维尔赫姆森 于 2017-05-24 设计创作，主要内容包括：公开了使接入点调度多个无线通信设备以进行传输的方法。该方法包括：为多个无线通信设备中的每个选择(210)相应的调制和编码方案MCS,其中相应的MCS中的每个与相应的功率回退相关联；将多个无线通信设备分类(220)成两个或更多个组,其中每个组具有最大尺寸；以及在不同的相应传输资源上调度(230)无线通信设备的两个或更多个组中的每个组。分类包括使具有相同的第一相应MCS和相同的第一相应功率回退的第一无线通信设备属于相同的组。分类还包括(如果未达到该组的最大尺寸)：如果满足分组标准,则使具有第二相应MCS和第二相应功率回退的第二无线通信设备属于该组。分组标准至少基于第一相应功率回退。还公开了对应的装置、接入点和计算机程序产品。(A method of an access point scheduling a plurality of wireless communication devices for transmission is disclosed. The method comprises the following steps: selecting (210) a respective modulation and coding scheme, MCS, for each of a plurality of wireless communication devices, wherein each of the respective MCSs is associated with a respective power backoff; classifying (220) the plurality of wireless communication devices into two or more groups, wherein each group has a maximum size; and scheduling (230) each of the two or more groups of wireless communication devices on a different respective transmission resource. The classifying includes causing first wireless communication devices having a same first corresponding MCS and a same first corresponding power backoff to belong to a same group. The classification also includes (if the maximum size of the group is not reached): if the grouping criterion is satisfied, a second wireless communication device having a second corresponding MCS and a second corresponding power backoff is made to belong to the group. The grouping criterion is based at least on the first respective power backoff. Corresponding apparatus, access points and computer program products are also disclosed.)

1. A method for an access point (100) to schedule a plurality of wireless communication devices (110, 120, 130, 140, 150, 160) for transmission, the method comprising:

selecting (210) a respective modulation and coding scheme, MCS, for each of the plurality of wireless communication devices, wherein each of the respective MCSs is associated with a respective power backoff;

classifying (220; 420) the plurality of wireless communication devices into two or more groups, wherein each group has a largest size, and wherein classifying comprises:

causing (422) first wireless communication devices having a same first respective MCS and a same first respective power backoff to belong to a same group; and

if the maximum size of the group is not reached (423), causing (425) a second wireless communication device having a second respective MCS and a second respective power backoff to belong to the group if a grouping criterion is met (424), wherein the grouping criterion is based at least on the first respective power backoff; and

each of the two or more groups of wireless communication devices is scheduled (230) on a different respective transmission resource (371, 372, 373).

2. The method of claim 1, wherein the different transmission resources comprise one or more of: different time resources, different frequency resources, and different spatial resources.

3. The method of any of claims 1-2, wherein the grouping criteria comprises: an absolute difference between the first respective power backoff and the second respective power backoff is less than any other non-zero absolute difference between the first respective power backoff and a respective power backoff associated with a respective MCS of any one of the plurality of wireless communication devices.

4. The method of any of claims 1-3, wherein a transmission channel between the access point and the second wireless communication device is characterized by a performance metric.

5. The method of claim 4, wherein the grouping criteria comprises: the performance metric is greater than a performance metric threshold, wherein the performance metric threshold is based on the first respective power backoff.

6. The method according to any one of claims 4 to 5, wherein the classifying (220) further comprises: selecting (426) a new first respective MCS for the first wireless communication device associated with a new first respective power backoff, the new first respective power backoff being lower than the first respective power backoff.

7. The method of any of claims 4 to 5, wherein selecting the respective MCS comprises: selecting the first respective MCS for a potential first wireless communication device based on at least one of:

-one or more second corresponding MCSs that have been selected for potential second wireless communication devices; and

-the performance metric is greater than a potential performance metric threshold, the potential performance metric threshold being based on the first respective power backoff to select.

8. A computer program product comprising a computer readable medium having thereon a computer program comprising program instructions, the computer program being loadable into a data-processing unit and configured to: the computer program, when executed by the data processing unit, causes the method of any of claims 1-7 to be performed.

9. An apparatus for an access point to schedule a plurality of wireless communication devices for transmission, the apparatus comprising a controller (500) configured to cause:

selecting a respective modulation and coding scheme, MCS, for each of the plurality of wireless communication devices, wherein each of the respective MCS is associated with a respective power backoff;

classifying the plurality of wireless communication devices into two or more groups, wherein each group has a largest size, and wherein the controller is configured to classify by:

causing first wireless communication devices having a same first respective MCS and a same first respective power backoff to belong to a same group; and

if the maximum size of the group is not reached, causing a second wireless communication device having a second corresponding MCS and a second corresponding power backoff to belong to the group if a grouping criterion is satisfied, wherein the grouping criterion is based at least on the first corresponding power backoff; and

scheduling each of the two or more groups of wireless communication devices on a different respective transmission resource.

10. The apparatus of claim 9, wherein the different transmission resources comprise one or more of: a different time resource; different frequency resources; and different spatial resources.

11. The apparatus of any of claims 9 to 10, the grouping criteria comprising: an absolute difference between the first respective power backoff and the second respective power backoff is less than any other non-zero absolute difference between the first respective power backoff and a respective power backoff associated with a respective MCS of any one of the plurality of wireless communication devices.

12. The apparatus of any of claims 9 to 11, wherein a transmission channel between the access point and the second wireless communication device is characterized by a performance metric.

13. The apparatus of claim 12, wherein the grouping criteria comprises: the performance metric is greater than a performance metric threshold, wherein the performance metric threshold is based on the first respective power backoff.

14. The apparatus according to any of claims 12 to 13, wherein the controller is further configured to perform the classifying by: selecting a new first respective MCS for the first wireless communication device associated with a new first respective power backoff, the new first respective power backoff being lower than the first respective power backoff.

15. The apparatus of any of claims 12 to 14, wherein the controller is adapted to select the respective MCS by selecting a potential first respective MCS for a potential first wireless communication device based on at least one of:

-one or more second corresponding MCSs that have been selected for potential second wireless communication devices; and

-the performance metric is greater than a potential performance metric threshold, the potential performance metric threshold being based on the potential first respective power backoff to select.

16. An access point comprising the apparatus of any one of claims 9 to 15.

Technical Field

The present disclosure relates generally to the field of wireless communications. More particularly, the present invention relates to multi-user scheduling of wireless communication devices.

Background

Orthogonal Frequency Division Multiplexing (OFDM) is a communication scheme well suited for broadband systems in frequency selective fading environments. For example, deep fading or narrowband interference typically affects only some of the subcarriers of an OFDM system, and this effect can typically be mitigated by forward error control coding. Furthermore, OFDM is bandwidth efficient since narrow subcarriers can be used to create power spectral density patterns with very sharp edges. Orthogonal Frequency Division Multiple Access (OFDMA) is a multi-user version of OFDM, in which multiple access is achieved by allocating disjoint sets of subcarriers to each user.

Example systems to which OFDMA applies include several of the 802.11 standard developed by IEEE (institute of electrical and electronics engineers) and UMTS LTE (universal mobile telecommunications system, long term evolution) developed by 3GPP (third generation partnership project).

In OFDMA where different sets of subcarriers are allocated to different users and different users may be associated with different Modulation and Coding Schemes (MCS), the maximum transmit power selection is typically dependent on EVM (error vector size) and PAPR (peak to average power ratio), as will be detailed below.

An ideal transmitter transmits only the exact signal constellation (constellation) points of the applicable MCS. However, various deficiencies in the implementation of practical transmitters (e.g., non-linearity, in-phase/quadrature (IQ-) imbalance, phase noise, etc.) cause the actually transmitted signal to deviate from the ideal signal constellation point of the MCS. EVM can be used as a measure of the amount of change in the transmitted signal from an ideal signal constellation point and can therefore be used to quantify the performance of a digital radio transmitter. Higher order signal constellations, such as 64-QAM (quadrature amplitude modulation) and 256-QAM, typically require a much lower EVM than lower order signal constellations, such as BPSK (binary phase shift keying) and QPSK (quadrature phase shift keying). Table 1 illustrates this by listing the requirements for relative signal constellation errors (expression associated with EVM) for all MCSs in the physical layer of ieee802.11ac.

Table 1:

MCS	modulation	Coding rate	Relative constellation error (dB)
				0	BPSK	1/2	-5
1	QPSK	1/2	-10
				2	QPSK	3/4	-13
3	16-QAM	1/2	-16
				4	16-QAM	3/4	-19
5	64-QAM	2/3	-22
				6	64-QAM	3/4	-25
7	64-QAM	5/6	-27
				8	256-QAM	3/4	-30
9	256-QAM	5/6	-32

High PAPR, which is a characteristic when using high order signal constellations, generally reduces the efficiency that can be achieved in the Power Amplifier (PA) of a transmitter, because the PA must operate in a region with a large linear range, and this region is generally not achievable if too high transmission power is used. Therefore, when transmitting an OFDM signal (or other signal having a high PAPR), it is generally necessary to apply a back-off (back-off) transmission power. For example, the transmission power backoff may be defined as the difference between the average transmission power used and the maximum transmission power associated with the transmitter.

Thus, a relatively high order signal constellation results in the need for a relatively large power back-off due to a high PAPR, and the (average) transmit power for higher order modulation formats is typically a few dB lower than for lower order (robust) modulation formats. Thus, and because the EVM requirements for higher order signal constellations are relatively stringent, relatively higher order signal constellations can only be used if channel conditions are favorable.

In an OFDMA system, different orders of modulation formats may typically be used for different users. When operating a power amplifier in OFDMA case, the most stringent modulation requirements for EVM determine the power backoff. The performance of low order modulation may be degraded if the power backoff is relatively large, which may result from using high order modulation for another user at the same time.

WO 2010/101497 a1 discloses identifying users requiring different modulation orders and grouping transmissions to different users into different subunits such that transmissions to users requiring the same modulation order are grouped into the same subunit.

This method is not always effective. For example, a packet may result in unused transmission resources due to a small group.

Therefore, there is a need for alternative or improved methods for multi-user scheduling of wireless communication devices (users). Preferably, this method is efficient in terms of transmission resources. Furthermore, these methods should preferably achieve that the throughput of one user is not unnecessarily limited by the requirements of another user.

Disclosure of Invention

It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. 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 is an object of some embodiments to address or mitigate, alleviate or eliminate at least some of the above or other disadvantages.

According to a first aspect, the object is achieved by a method for an access point to schedule a plurality of wireless communication devices for transmission. The method comprises the following steps: selecting a respective Modulation and Coding Scheme (MCS) for each of a plurality of wireless communication devices (wherein each of the respective MCSs is associated with a respective power backoff); classifying the plurality of wireless communication devices into two or more groups (wherein each group has a maximum size); and scheduling each of the two or more groups of wireless communication devices on a different respective transmission resource.

The classification includes: causing first wireless communication devices having a same first respective MCS and a same first respective power backoff to belong to a same group; and (if the maximum size of the group is not reached) if the grouping criterion is met, causing a second wireless communication device having a second corresponding MCS and a second corresponding power backoff to belong to the group. The grouping criterion is based at least on a first respective power backoff.

According to some embodiments, the second respective power backoff is lower than the first respective power backoff. In some embodiments, the second respective power backoff is equal to the first respective power backoff. In other embodiments, the second respective power backoff is less than or equal to the first respective power backoff.

In some embodiments, the method further comprises: data is transmitted to a plurality of wireless communication devices according to a schedule for two or more groups.

According to some embodiments, the different transmission resources comprise one or more of different time resources, different frequency resources and different spatial resources.

In some embodiments, the grouping criteria include: an absolute difference between the first respective power backoff and the second respective power backoff is less than any other non-zero absolute difference between the first respective power backoff and a respective power backoff associated with a respective MCS of any one of the plurality of wireless communication devices.

According to some embodiments, a transmission channel between the access point and the second wireless communication device is characterized by a performance metric.

In some embodiments, the grouping criteria include: the performance metric is greater than a performance metric threshold, wherein the performance metric threshold is based on the first respective power backoff.

According to some embodiments, the classifying further comprises: a new first respective MCS associated with a new first respective power backoff is selected (for the first wireless communication device), the new first respective power backoff being lower than the first respective power backoff.

In some embodiments, selecting the respective MCS comprises: selecting (for the potential first wireless communication device) a first respective MCS based on at least one of:

-one or more second corresponding MCSs that have been selected for potential second wireless communication devices; and

-the performance metric is greater than a potential performance metric threshold, the potential performance metric threshold being based on the first respective power backoff to select.

A second aspect is a computer program product comprising a computer readable medium having thereon a computer program comprising program instructions. The computer program is loadable into a data processing unit and configured to: the method according to the first aspect is performed when the computer program is run by the data processing unit.

A third aspect is an apparatus for an access point to schedule a plurality of wireless communication devices for transmission. The apparatus includes a controller configured to: selecting a respective Modulation and Coding Scheme (MCS) for each of a plurality of wireless communication devices (wherein each of the respective MCSs is associated with a respective power backoff); classifying the plurality of wireless communication devices into two or more groups (wherein each group has a maximum size); and scheduling each of the two or more groups of wireless communication devices on a different respective transmission resource.

The controller is configured to classify by: causing first wireless communication devices having a same first respective MCS and a same first respective power backoff to belong to a same group; and (if the maximum size of the group is not reached) if the grouping criterion is met, causing a second wireless communication device having a second corresponding MCS and a second corresponding power backoff to belong to the group. The grouping criterion is based on at least a first respective power backoff.

In some embodiments, the controller is further configured to: data is transmitted to a plurality of wireless communication devices according to a schedule for two or more groups.

In some embodiments, the selection may be performed by a selector (e.g., selection circuitry, link adaptation circuitry). In some embodiments, the classification may be performed by a classifier (e.g., scheduler, scheduling circuitry). In some embodiments, the scheduling may be performed by a scheduler (e.g., scheduling circuitry). In some embodiments, the transmitting may be performed by a transmitter (e.g., transmit circuitry).

A fourth aspect is an apparatus for an access point to schedule a plurality of wireless communication devices for transmission. The device includes: a selection circuit configured to select, for each of a plurality of wireless communication devices, a respective Modulation and Coding Scheme (MCS) (wherein each of the respective MCSs is associated with a respective power backoff); a classification circuit configured to classify the plurality of wireless communication devices into two or more groups (wherein each group has a maximum size); and scheduling circuitry configured to schedule each of the two or more groups of wireless communication devices on different respective transmission resources.

The classification circuit is configured to classify by: causing first wireless communication devices having a same first respective MCS and a same first respective power backoff to belong to a same group; and (if the maximum size of the group is not reached) if the grouping criterion is met, causing a second wireless communication device having a second corresponding MCS and a second corresponding power backoff to belong to the group. The grouping criterion is based on at least a first respective power backoff.

A fifth aspect is an access point comprising the apparatus of any of the third or fourth aspects.

In some embodiments, any of the above aspects may additionally have features that are the same as or correspond to any of the various features described above for any of the other aspects.

An advantage of some embodiments is that efficient scheduling of multiple wireless communication devices is provided. For example, the efficiency may be manifested by one or more of the following:

-not unnecessarily leaving empty available transmission resources,

not unnecessarily forcing the user to use a modulation order lower than possible,

not unnecessarily forcing the user to use a power backoff that is larger than necessary.

Drawings

Other objects, features and advantages will be apparent from the following detailed description of embodiments, which is made with reference to the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating example embodiments.

FIG. 1 is a diagram illustrating an example scenario in which some embodiments may be applicable;

FIG. 2 is a flow diagram illustrating example method steps according to some embodiments;

FIG. 3 is a diagram illustrating an example scheduling of groups, according to some embodiments;

FIG. 4 is a flow diagram illustrating example method steps according to some embodiments;

FIG. 5 is a schematic block diagram illustrating an example apparatus according to some embodiments; and

FIG. 6 is a schematic diagram illustrating an example computer-readable medium, according to some embodiments.

Detailed Description

Embodiments of the present disclosure will be described and illustrated more fully hereinafter with reference to the accompanying drawings. The solutions disclosed herein may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the following, embodiments will be described in which multiple wireless communication devices (used interchangeably herein with "user" and "STA" (for station)) can be efficiently scheduled for downlink transmissions. This embodiment is typically performed by an access point serving a plurality of wireless communication devices.