阅读说明：本技术 使用扩展码的传输 (Transmission using spreading codes ) 是由 辛雨 边峦剑 于 2018-03-05 设计创作，主要内容包括：描述了与减少正交频分复用(OFDM)技术的带外发射有关的方法、系统和设备。在一个代表性方面,一种无线通信方法包括：通过将N个数据与N个扩展码相乘来获得N组扩展数据,将所述N组扩展数据合并成数据序列,将所述数据序列调制到2K个子载波上,以及传输所调制的数据序列。具体地,所述N个扩展码中的单个扩展码包括被组织为K对的序列的2K个元素,其中,所述对符合以下中的至少一项(1)一对中的两个元素具有180度相位差或(2)相邻对中的相应元素具有180度相位差。N和K是大于1的整数,并且N小于2K。(Methods, systems, and devices related to reducing out-of-band emissions of Orthogonal Frequency Division Multiplexing (OFDM) techniques are described. In one representative aspect, a method of wireless communication includes: the method includes obtaining N sets of spread data by multiplying N data by N spreading codes, combining the N sets of spread data into a data sequence, modulating the data sequence onto 2K subcarriers, and transmitting the modulated data sequence. In particular, a single spreading code of the N spreading codes comprises 2K elements organized as a sequence of K pairs, wherein the pairs are in accordance with at least one of (1) two elements of a pair have a 180 degree phase difference or (2) corresponding elements of adjacent pairs have a 180 degree phase difference. N and K are integers greater than 1, and N is less than 2K.)

1. A method of wireless communication, comprising:

obtaining N sets of spread data by multiplying the N data by N spreading codes;

merging the N sets of spread data into a data sequence;

modulating the data sequence onto 2K subcarriers; and is

The modulated data sequence is transmitted and,

wherein a single spreading code of the N spreading codes comprises K pairs of elements, wherein the K pairs of elements are in accordance with at least one of: (1) two elements in a pair have a 180 degree phase difference or (2) corresponding elements in adjacent pairs have a 180 degree phase difference, and

wherein N and K are integers greater than 1, and N < 2K.

2. The method of claim 1, further comprising:

the N spreading codes are selected from 2K spreading codes orthogonal to each other.

3. The method of claim 1, wherein the merging of the N sets of extension data comprises:

and adding the plurality of groups of spread data to generate the data sequence.

4. The method of claim 1, wherein the merging of the multiple sets of extension data comprises:

applying coefficients to each of the N sets of spread data to generate a plurality of sets of weighted spread data; and

adding the plurality of sets of weighted spread data to generate the data sequence.

5. The method of claim 4, wherein the coefficients of the plurality of sets of extended data are ordered based on their corresponding absolute values.

6. The method of claim 1, wherein the 2K subcarriers are equally spaced 2K subcarriers in a frequency domain.

7. The method of claim 6, wherein the equal spacing in the frequency domain is equal to the width of m subcarriers, m being greater than or equal to 1.

8. The method of claim 1, wherein the N spreading codes comprise a spreading code that satisfies the following condition: the two elements in each pair have a phase difference of 180 degrees.

9. The method of claim 1, wherein N-3, and the spreading code comprises: s1 ═ C, -C, S2 ═ C, -C, -C ], and S3 ═ C, -C, C is a complex number.

10. The method of claim 1, wherein N-2 or 3, and the spreading code comprises: s1 ═ C, -C, C ] and S2 ═ C, -C, C are complex numbers.

11. The method of claim 1, wherein the spreading code comprises: s1 ═ C, -C, C is a complex number.

12. A method of wireless communication, comprising:

receiving a data sequence modulated on 2K subcarriers, wherein the data sequence is generated by combining N sets of spread data obtained by multiplying N data by N spreading codes; and is

Demodulating the data sequence based on the N spreading codes to obtain the N data,

wherein a single spreading code of the N spreading codes comprises K pairs of elements, wherein the K pairs of elements are in accordance with at least one of: (1) two elements in a pair have a 180 degree phase difference or (2) corresponding elements in adjacent pairs have a 180 degree phase difference, and wherein N and K are integers greater than 1, and N < 2K.

13. The method of claim 12, wherein the N spreading codes are selected from 2K spreading codes that are orthogonal to each other.

14. The method of claim 12, wherein the data sequence is generated by adding the sets of spread data together.

15. The method of claim 12, the data sequence being generated by:

applying coefficients to each of the N sets of spread data to generate a plurality of sets of weighted spread data; and

adding together the sets of weighted spread data.

16. The method of claim 15, wherein the coefficients of the plurality of sets of extended data are ordered based on their corresponding absolute values.

17. The method of claim 12, wherein the 2K subcarriers are equally spaced 2K subcarriers in a frequency domain.

18. The method of claim 17, wherein the equal spacing in the frequency domain is equal to a width of m subcarriers, m being greater than or equal to 1.

19. The method of claim 12, wherein the N spreading codes comprise a spreading code that satisfies the following condition: the two elements in each pair have a phase difference of 180 degrees.

20. The method of claim 12, wherein N-3 and the spreading codes comprise: s1 ═ C, -C, S2 ═ C, -C, and S3 ═ C, -C, C are plural.

21. The method of claim 12, wherein N-2 or 3, and the spreading code comprises: s1 ═ C, -C, C ] and S2 ═ C, -C, C are complex numbers.

22. The method of claim 12, wherein the spreading code comprises: s1 ═ C, -C, C is a complex number.

23. A wireless communication apparatus comprising a processor configured to perform the method of any of claims 1-22.

24. A non-transitory computer-readable medium having code stored thereon, which, when executed by a processor, causes the processor to implement the method of any one of claims 1 to 22.

Technical Field

This patent document relates generally to digital wireless communications.

Background

Mobile communication technology is pushing the world to an increasingly interconnected and networked society. Rapid development of mobile communications and advances in technology have resulted in greater demands for capacity and connectivity. Other aspects such as energy consumption, equipment cost, spectral efficiency, and latency are also important to meet the needs of various communication scenarios. Various techniques are being discussed, including new methods for providing higher quality of service.

Disclosure of Invention

This document discloses methods, systems, and devices related to digital wireless communications, and more particularly, to techniques related to reducing out-of-band emissions of Orthogonal Frequency Division Multiplexing (OFDM) techniques.

In one representative aspect, a method for wireless communication is disclosed. The method includes obtaining N sets of spread data by multiplying the N sets of data by N spreading codes, combining the N sets of spread data into a data sequence, modulating the data sequence onto 2K subcarriers, and transmitting the modulated data sequence. Individual ones of the N spreading codes include 2K elements organized as a sequence of K pairs, wherein the pairs are at least one of (1) two elements in a pair have a 180 degree phase difference, or (2) corresponding elements in adjacent pairs have a 180 degree phase difference. N and K are integers greater than 1, and N is less than 2K.

In another representative aspect, a method for wireless communication is disclosed. The method includes receiving a data sequence modulated on 2K subcarriers, wherein the data sequence is generated by combining N sets of spread data obtained by multiplying N sets of data by N spreading codes; and demodulating the data sequence based on the N spreading codes to obtain the N sets of data. A single spreading code of the N spreading codes includes 2K elements organized as a sequence of K pairs, wherein the pairs are at least one of (1) two elements of a pair have a 180 degree phase difference or (2) corresponding elements of adjacent pairs have a 180 degree phase difference. N and K are integers greater than 1, and N is less than 2K.

In another representative aspect, a wireless communications apparatus that includes a processor is disclosed. The processor is configured to implement the methods described herein.

In yet another representative aspect, the various techniques described herein may be embodied as processor executable code and stored on a computer readable program medium.

The details of one or more implementations are set forth in the accompanying drawings, the drawings, and the description below. Other features will be apparent from the description and drawings, and from the claims.

Drawings

Fig. 1A shows a schematic diagram of side lobes in the frequency domain that produce overlapping spectra between subcarriers.

Fig. 1B is a diagram of different subcarrier spacings and corresponding slot sizes.

Fig. 2A is a flowchart representation of a method for wireless communication.

Fig. 2B is a flowchart representation of another method for wireless communication.

Fig. 3A shows a comparison between a conventional OFDM technique and an improved OFDM technique using different spreading codes.

Fig. 3B shows another comparison between conventional OFDM techniques and improved OFDM techniques using different spreading codes.

Fig. 4 illustrates an example of a wireless communication system in which techniques in accordance with one or more embodiments of the present technology may be applied.

Fig. 5 is a block diagram representation of a portion of a radio station.

Detailed Description

Orthogonal Frequency Division Multiplexing (OFDM) is a method of encoding digital data over a multi-carrier frequency. OFDM has developed into a mainstream scheme of broadband digital communication and is applied to many communication systems such as a fourth generation (4G) wireless communication network and a fifth generation (5G) wireless communication network. The OFDM technique utilizes the property that subcarriers are orthogonal to each other and do not interfere with each other, and allows multiple data transmissions to be made simultaneously on multiple subcarriers.

One possible drawback of conventional OFDM is that its out-of-band (OOB) emission level is relatively high due to the sidelobes of the subcarriers. Out-of-band leakage may cause strong interference to adjacent frequency bands. Fig. 1A shows a schematic diagram of a side lobe 101 that produces overlapping spectra between subcarriers in the frequency domain. To reduce the effect of out-of-band leakage, the edge of the transmission band may specify a certain frequency as a guard interval to reduce the effect of out-of-band leakage on adjacent bands. However, the guard interval introduces waste in the frequency band and reduces spectral efficiency. This becomes an important issue for communication systems, especially when many different radio systems co-reside in a dense spectrum band.

Furthermore, as wireless communication technology advances, the subcarrier spacing is no longer strictly uniform. For example, New Radio (NR) technologies developed as 5G technology solutions support different subcarrier spacing values. Table 1 shows five parameter sets supported by NR, each corresponding to a different subcarrier spacing. Fig. 1B is a diagram of different subcarrier spacings and their corresponding slot sizes. Since adjacent subcarriers may have different sets of parameters, out-of-band leakage may result in strong interference to adjacent frequency bands (e.g., between 15KHz and 240KHz subcarriers).

Different parameter sets in table 1NR

μ	Δf＝2μ·15[kHz]	Cyclic prefix
			0	15	Is normal
1	30	Is normal
			2	60	Normal, extended
3	120	Is normal
			4	240	Is normal

Currently available techniques do not effectively reduce out-of-band leakage, thereby achieving better spectral efficiency. The present disclosure describes data modulation techniques that may be used in various embodiments to reduce out-of-band emissions. The disclosed techniques may be used to construct embodiments that significantly improve the spectral utilization efficiency of transmissions based on OFDM techniques.

SUMMARY

A set of spreading codes that allow sidelobe amplitudes to be cancelled may be used to help reduce out-of-band leakage. For example, a set of data may be spread by multiplying the data by a spreading code having a length L (L > 1). The extension data may then be transmitted on the L subcarriers. However, doing so may reduce data transmission efficiency because the same data is transmitted on multiple subcarriers.

To solve the problem of data transmission efficiency, multiple sets of data can be combined together for transmission. Fig. 2A is a flowchart representation of a method 200 for wireless communication. The method 200 includes, at 202, obtaining N sets of spread data by multiplying the N sets of data by N spreading codes. The method 200 includes, at 204, merging the N sets of spread data into a data sequence. The method includes modulating a data sequence onto 2K subcarriers, at 206. The method 200 also includes transmitting the modulated data sequence, at 208. Here, a single spreading code of the N spreading codes comprises 2K elements organized as a sequence of K pairs. The pairs are at least one of (1) two elements in one pair have a 180 degree phase difference, or (2) corresponding elements in adjacent pairs have a 180 degree phase difference. N and K are integers greater than 1, and N < 2K.

In some embodiments, the method further comprises selecting N spreading codes from the 2K spreading codes. In some embodiments, the 2K spreading codes are orthogonal to each other. In some embodiments, the N spreading codes may be selected from at least 2K spreading codes (e.g., (2K + P) spreading codes), where a subset of the spreading codes are not orthogonal to each other.

In some embodiments, the combining of the N sets of spread data includes summing the sets of spread data to generate the data sequence.

In some embodiments, the combining of the sets of spread data includes applying coefficients to each of the N sets of spread data to generate sets of weighted spread data and adding the sets of weighted spread data to generate the data sequence. In some embodiments, the coefficients of the sets of extended data are ordered based on their corresponding absolute values.

In some embodiments, the centers of the 2K subcarriers are spaced apart by equal distances in the frequency domain. For example, the equal distance in the frequency domain may be equivalent to the frequency domain spacing between the centers of adjacent subcarriers.

In some embodiments, the N spreading codes comprise a spreading code that satisfies the following condition: the two elements in each pair have a phase difference of 180 degrees.

Fig. 2B is a flowchart representation of a method 200 for wireless communication. The method 250 includes, at 252, receiving a data sequence modulated on 2K subcarriers, wherein the data sequence is generated by combining N sets of spread data obtained by multiplying N sets of data by N spreading codes. The method also includes demodulating the data sequence based on the N spreading codes to obtain the N sets of data, at 254.

Details of the disclosed technology are described in the following examples. In the following embodiments, the transmission of the data sequence is performed over a transmission band. The transmission band refers to a frequency resource for transmitting data. The transmission band may include a plurality of subcarriers. The transmission band may be a wideband, a sub-band within a wideband, or a frequency resource comprising multiple transmission bandwidths and/or sub-bands. For example, a wideband channel may include 128, 512, 1024 or more number of subcarriers, for example, and may span a bandwidth of several MHz (e.g., 1MHz, 5MHz, 10MHz, 20MHz, or greater than 20 MHz). It should also be noted that the following embodiments are primarily concerned with spreading codes comprising four elements (K-2). However, the disclosed technique is not limited to K ═ 2, and can be applied to spreading codes having various numbers of elements.

Example embodiment 1

This embodiment describes the selection of the N spreading codes.

The spreading code may have an element, which is C or-C, where C is a complex value. To obtain a spreading code having 2K elements, a pool of 2K spreading codes may be generated such that the 2K spreading codes are orthogonal to each other.

The individual spreading codes are organized as sequences of K pairs. In some embodiments, the N spreading codes are selected such that the selected codes satisfy at least one of: (1) two elements in one pair have a 180 degree phase difference or (2) corresponding elements in adjacent pairs have a 180 degree phase difference.

In some embodiments, simulations may be performed to determine whether some spreading codes (e.g., (2K-M) codes) in the pool are not effective in suppressing out-of-band leakage. The remaining M spreading codes can then effectively suppress out-of-band leakage, and the N spreading codes selected from the M spreading codes can be used to obtain spread data for transmission over a plurality of subcarriers. M is an integer greater than 1, and N < ═ M < 2K. For example, the value of N may be 1, 2, 3, …, M.

For example, when K ═ 2, a pool of four spreading codes may be determined: s1 ═ C, -C, C ], S2 ═ C, -C, S3 ═ C, -C, and S4 ═ C, C. S1, S2, and S3 are chosen because, for each of them, the phase difference of two elements in a pair is pi, or the phase difference of the corresponding elements in adjacent pairs is pi. S4 was not selected because it did not satisfy either condition and therefore it could not be used to effectively suppress out-of-band leakage.

In some embodiments, the elements in the spreading code may have different absolute values (i.e., modulus). The modulus of each element in the spreading code affects the amplitude of the resulting signal, and thus the sidelobe amplitude and out-of-band leakage. Selecting a different modulus for each element may improve or affect the effectiveness of the spreading code in suppressing out-of-band leakage. For example, the spreading code may include the following element [ C ]₁,-C₂,C₃,-C₄]。C₁，C₂，C₃And C₄The modulus of at least two of which are different.

Simulations may be performed to evaluate the effectiveness of each spreading code. Fig. 3A shows a comparison between a conventional OFDM technique and an improved OFDM technique using different spreading codes. The top curve 301 shows the power spectral density of conventional OFDM. The bottom curve 302 shows the power spectral density of the OFDM modulation using spreading code S1. The middle curves 303, 304 show the power spectral density of the OFDM modulation using spreading code S2 and the power spectral density of the OFDM modulation using spreading code S3, respectively. It follows that S1 is the most efficient spreading code to suppress out-of-band leakage, followed by S2. Of the three codes (S1, S2, and S3), S3 is the least efficient.

Since the effectiveness of different spreading codes to suppress out-of-band leakage is different (e.g., S1> S2> S3), more efficient spreading codes may be more desirable for various scenarios. The most efficient spreading codes can be used in different scenarios, while less efficient spreading codes can be used in a limited number of scenarios. For example, when N ═ 1 group data is transmitted, S1 is selected to expand the data. When N-2 group data is transmitted, S1 and S2 are selected to expand the data. When transmitting N-3 groups of data, S1, S2, and S3 are all selected to expand the data.

Example embodiment 2

The present embodiment describes the merging of multiple sets of extension data.

In some embodiments, multiple sets of spread data may be combined by adding the multiple sets together. In some embodiments, a set of coefficients may be used to obtain a weighted sum of multiple sets of data. Weighted sums may be beneficial because different spreading codes have different effects on suppressing out-of-band leakage.

For example, as shown above, S1 is more efficient than S2 and S3 (i.e., S1> S2> S3). Each spreading code has a respective coefficient P (1), P (2) and P (3). The absolute value (i.e. modulus) of the coefficients may correspond to the validity of the spreading code. For example, in some embodiments, | P (1) | > | P (2) | ≧ | P (3) |. In some embodiments, the coefficients may have the same modulus value. It should be noted that the modulus of the coefficients can affect the data demodulation performance. Therefore, it is desirable to consider the performance of the transmission band in configuring the coefficients.

Example embodiment 3

The present embodiment describes subcarriers on which spread data is transmitted.

After the multiple sets of data are spread and combined, the combined data is modulated and transmitted on 2K subcarriers. In some embodiments, the 2K subcarriers are contiguous in the frequency domain. In some embodiments, the 2K subcarriers may be separated.

For example, the 2K subcarriers may be spaced apart at equal intervals from each other. In some embodiments, two adjacent subcarriers are separated by m intervals in the frequency domain (m ≧ 0). The value of m may be configured according to various factors such as channel conditions or transmission scenarios.

Example embodiment 4

Fig. 3B shows another comparison of a conventional OFDM technique with an improved OFDM technique using a different spreading code. The curve shown in fig. 3B is generated based on the following scenario. In particular, the top curve 311 shows the power spectral density of conventional OFDM.

When N is 1, extended data is obtained by multiplying a set of data by S1 ═ C, -C, C ]. The size of the extension data is four times the size of the original data. The spread data is then transmitted on four subcarriers. Out-of-band leakage (as shown by the bottom curve 312) can be greatly reduced, but the data transfer efficiency is only 25%.

When N is 2, spread data is obtained by multiplying the two sets of data by a spreading code. Multiplying the first set of data by S1 ═ C, -C, C]. Multiplying the second set of data by S2 ═ C, -C, -C]. By using the coefficient P (1) ═A weighted sum of the two sets of data is obtained to combine the two sets of spread data. The combined spreading number is then transmitted on four subcarriers. Out-of-band leakage can be reduced (as shown by curve 313) and the data transfer efficiency is 50%.

When N is 3, spread data is obtained by multiplying the three sets of data by a spreading code. Multiplying the first set of data by S1 ═ C, -C, C]. Multiplying the second set of data by S2 ═ C, -C, -C]. Multiplying the third set of data by S3 ═ C, -C]. By using coefficientsA weighted sum of the three sets of data is obtained to combine the three sets of spread data. The combined spread data is then transmitted on four subcarriers. Out-of-band leakage may be reduced (as shown by curve 314) and the data transfer efficiency is 75%.

Example 5

This example describes a detailed implementation of the techniques disclosed herein.

In this example, K is 2 and N is 3. Three spreading codes are selected from 2K-4 spreading codes: s1 ═ 1, -1, -1,1, S2 ═ 1, -1, and S3 ═ 1,1, -1, -1.

Some or all of the data to be transmitted in the OFDM symbols of the transmission band are divided into three groups. The first group comprises [ a₁,a₂,a₃,…,a_m]. The second group consisting of₁,b₂,b₃,…,b_m]. The third group includes [ c₁,c₂,c₃,…,c_m]。

The first set of data to be transmitted is [1, -1, -1,1] with S1]Multiplying to obtain [ a ]₁,-a₁,-a₁,a₁,a₂,-a₂,-a₂,a₂,a₃,-a₃,-a₃,a₃,…,a_m,-a_m,-a_m,a_m]. The second set of data to be transmitted is [1, -1,1, -1] with S2]Multiplying to obtain [ b ]₁,-b₁,b₁,-b₁,b₂,-b₂,b₂,-b₂,b₃,-b₃,b₃,-b₃,…,b_m,-b_m,b_m,-b_m]. The third set of data to be transmitted is [1,1, -1] with S3]Multiplying to obtain [ c ]₁,c₁,-c₁,-c₁,c₂,c₂,-c₂,-c₂,c₃,c₃,-c₃,-c₃,…,c_m,c_m,-c_m,-c_m]。

These three sets of spread data are combined by performing a weighted sum operation of the sets using coefficients P (1), P (2), and P (3): d is P (1) × [ a ]₁,-a₁,-a₁,a₁,a₂,-a₂,-a₂,a₂,a₃,-a₃,-a₃,a₃,…,a_m,-a_m,-a_m,a_m]+P(2)×[b₁,-b₁,b₁,-b₁,b₂,-b₂,b₂,-b₂,b₃,-b₃,b₃,-b₃,…,b_m,-b_m,b_m,-b_m].+P(3)×[c₁,c₁,-c₁,-c₁,c₂,c₂,-c₂,-c₂,c₃,c₃,-c₃,-c₃,…,c_m,c_m,-c_m,-c_m]. The values of P (1), P (2) and P (3) may be equal or different depending on the channel conditions. Then, the combined data D is transmitted on (2K × m ═ 4m) subcarriers.

Fig. 4 illustrates an example of a wireless communication system in which techniques in accordance with one or more embodiments of the present technology may be applied. The wireless communication system 400 may include one or more Base Stations (BSs) 405a, 405b, one or more wireless devices 410a, 410b, 410c, and 410d, and a core network 425. Base stations 405a and 405b may provide wireless service to wireless devices 410a, 410b, 410c, and 410d in one or more wireless sectors. In some embodiments, base stations 405a and 405b include directional antennas to generate two or more directional beams to provide wireless coverage in different sectors.

The core network 425 may communicate with one or more base stations 405a, 405 b. The core network 425 provides connectivity to other wireless and wireline communication systems. The core network may include one or more service subscription databases to store information related to subscribed wireless devices 410a, 410b, 410c, and 410 d. The first base station 405a may provide wireless service based on a first radio access technology, while the second base station 405b may provide wireless service based on a second radio access technology. Depending on the deployment scenario, the base stations 405a and 405b may be quasi co-located, or may be installed separately on site. The wireless devices 410a, 410b, 410c, and 410d may support a plurality of different radio access technologies.

In some embodiments, a wireless communication system may include multiple networks using different wireless technologies. A dual-mode or multi-mode wireless device includes two or more wireless technologies that may be used to connect to different wireless networks.

Fig. 5 is a block diagram representation of a portion of a radio station. A radio station 505, such as a base station or wireless device (or UE), may include processor electronics 510, such as a microprocessor implementing one or more radio technologies presented in this document. The radio station 505 may include transceiver electronics 515 to transmit and/or receive wireless signals over one or more communication interfaces, such as antenna 520. The radio station 505 may include other communication interfaces for transmitting and receiving data. The radio station 505 may include one or more memories (not explicitly shown) configured to store information such as data and/or instructions. In some embodiments, the processor electronics 510 may include at least a portion of the transceiver electronics 515. In some embodiments, at least some of the disclosed techniques, modules, or functions are implemented using a radio station 505.

It is therefore apparent that a method and corresponding apparatus related to reducing out-of-band emissions are disclosed. Using the disclosed techniques, out-of-band emissions can be significantly suppressed without sacrificing much transmission efficiency. Thus, the spectrum utilization can be improved for transmission based on OFDM techniques.

From the foregoing, it will be appreciated that specific embodiments of the disclosed technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the scope of the invention. Accordingly, the disclosed technology is not limited, except as by the appended claims.

The disclosed embodiments and other embodiments, modules, and functional operations described in this document can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this document and their equivalents, or in combinations of one or more of them. The disclosed embodiments and other embodiments may be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer-readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter effecting a machine-readable propagated signal, or a combination of one or more of them. The term "data processing apparatus" encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or multiple computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to suitable receiver apparatus.

A computer program (also known as a program, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

The processes and logic flows described in this document can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit). .

Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or optical disks. However, a computer need not have such a device. Computer-readable media suitable for storing computer program instructions and data include various forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and CD ROM disks and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

While this patent document contains many specifics, these should not be construed as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features specific to particular embodiments of particular inventions. Certain features that are described in this patent document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a described combination can in some cases be excised from the combination, and the described combination may be directed to a subcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Moreover, the separation of various system components in the embodiments described in this patent document should not be understood as requiring such separation in all embodiments.

Only some embodiments and examples are described and other embodiments, enhancements and variations can be made based on what is described and illustrated in this patent document.