CN113632557A

CN113632557A - Generating sequences for reference signals

Info

Publication number: CN113632557A
Application number: CN201980094709.3A
Authority: CN
Inventors: 梁春丽; 蒋创新; 夏树强
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2019-03-26
Filing date: 2019-03-26
Publication date: 2021-11-09
Also published as: WO2020191624A1

Abstract

Methods, systems, and apparatus for generating sequence pairs for reference signals in mobile communication technologies are described. An exemplary method of wireless communication includes: a reference signal is transmitted with a wireless node over a plurality of subcarriers using a digital modulation technique, wherein the reference signal includes M (M ≧ 2) sequences selected based on a search of a set of sequences in a manner such that the M sequences satisfy at least one search termination condition.

Description

Generating sequences for reference signals

Technical Field

This document relates generally to wireless communications.

Background

Wireless communication technology is pushing the world to an increasingly connected and networked society. The rapid growth of wireless communications and advances in technology have resulted in greater demands for capacity and connectivity. Other aspects such as energy consumption, device cost, spectral efficiency, and latency are also important to meet the needs of various communication scenarios. Next generation systems and wireless communication technologies need to provide support for an increased number of users and devices, and support for higher data rates, compared to existing wireless networks, thereby requiring user equipment to implement power saving techniques.

Disclosure of Invention

Methods, systems, and apparatus for generating sequences for reference signals in mobile communication technologies, including 5 generation (5G) communication systems and new air interface (NR) communication systems. In one exemplary aspect, a method of wireless communication is disclosed. The method comprises the following steps: a reference signal is transmitted with a wireless node over a plurality of subcarriers using a digital modulation technique, wherein the reference signal includes M (M ≧ 2) sequences selected based on a search of a set of sequences in a manner such that the M sequences satisfy at least one search termination condition.

In another exemplary aspect, a method of wireless communication may comprise: receiving, at a wireless node, data and a reference signal using a plurality of subcarriers, wherein the reference signal comprises M sequences over M (M ≧ 2) symbols and is used to demodulate the data; and detecting the reference signal based at least in part on searching a set of sequences in a manner such that the M sequences satisfy at least one condition.

In yet another exemplary aspect, the M sequences include at least one pair of sequences A, B arranged in a hopping A, B, A, B, A, B, … … repeating pattern.

In another exemplary aspect, the above-described method is embodied in the form of processor executable code and stored in a computer readable program medium.

In yet another exemplary aspect, an apparatus configured or operable to perform the above method is disclosed.

The above and other aspects and embodiments thereof are described in more detail in the accompanying drawings, the following description and the claims.

Drawings

Fig. 1 illustrates an example of a Base Station (BS) and a User Equipment (UE) in wireless communications, in accordance with some embodiments of the disclosed technology.

Fig. 2 is a block diagram of an example implementation of a wireless communication device.

Fig. 3A and 3B are block diagram representations of a portion of an apparatus in accordance with some embodiments of the disclosed technology.

Fig. 4 illustrates an example of a wireless communication method in accordance with some embodiments of the disclosed technology.

Detailed Description

There is an increasing demand for fourth-Generation mobile communication technology (4G), Long-Term Evolution (LTE), Long-Term Evolution Advanced (LTE-Advanced/LTE-a), and fifth-Generation mobile communication technology (5G), the 4th Generation mobile communication technology. From the current trend of development, 4G and 5G systems are researching features supporting enhanced mobile broadband, ultra-high reliability, ultra-low delay transmission and massive connection.

In a new generation nr (new radio) technology, a Physical Uplink Control Channel (PUCCH) and a Physical Uplink Shared Channel (PUSCH) support pi/2-BPSK modulation in order to further reduce a peak-to-average power ratio (PAPR) of a signal. pi/2-BPSK is generated from a standard BPSK signal by multiplying a sequence of symbols with a rotating phasor that is incremented by pi/2 in phase per symbol period. pi/2-BPSK has the same error rate performance as BPSK on linear channels, however, it exhibits less envelope variation (i.e., PAPR) making it more suitable for transmission with non-linear channels. This improves the power amplifier efficiency cost in the mobile terminal at lower data rates.

pi/2-BPSK modulation is used to modulate the data portion of the signal, while the reference signal (or DMRS (demodulation reference signal) signal herein) still uses Zadoff-chu (zc) sequences or QPSK-based computer-generated sequences (referred to as CGS sequences). The current embodiment has shown that the PAPR is different between the data part and the reference signal if the data part is modulated using pi/2-BPSK and the reference signal uses a ZC sequence or a CGS sequence, where the PAPR of the data part is lower than the PAPR of the reference signal. In the current embodiment, when a user transmits PUSCH or PUCCH, power can only be adjusted for the entire PUSCH or PUCCH; that is, the transmission power of a specific symbol cannot be adjusted individually. Thus, the unequal PAPR of the data portion to the PAPR of the reference signal portion results in the low PAPR performance of the pi/2-BPSK modulation not being fully utilized because the power adjustment is based on the higher PAPR of the reference signal. Therefore, higher requirements are placed on the design of the reference signal. Thus, sequence design with low peak-to-average ratio becomes a problem to be solved. Furthermore, when the reference signal comprises at least two sequences (e.g., in two symbols), identifying and/or combining the two sequences together for better performance is another problem to be solved. This patent document addresses this need, among other things. The present document is directed to selecting sequence pairs from a set of sequences such that at least one search termination condition is achieved or satisfied, resulting in better system performance. In some embodiments, the search termination condition may relate to a joint autocorrelation condition associated with the sequence pair. In some embodiments, the search termination condition may be related to the length of the sequences in the sequence pair. It should be understood that although the discussion herein is based on sequence pairs, such discussion is for illustrative purposes only. In some embodiments, for example, the pair of sequences may be included in the reference signal as M sequences arranged in a repeating hopping pattern denoted A, B, A, B, … ….

Embodiments of the disclosed technology

Fig. 1 shows an example of a wireless communication system (e.g., an LTE, 5G, or new air interface (NR) cellular network) including a Base Station (BS)120 and one or more User Equipments (UEs) 111, 112, and 113. In some embodiments, the upstream transmission (131, 132, 133) includes a pi/2 BPSK modulated data portion and a reference signal including a sequence described by the presently disclosed technology. The UE may be, for example, a smartphone, a tablet, a mobile computer, a machine-to-machine (M2M) device, a terminal, a mobile device, an internet of things (IoT) device, and/or the like.

Section headings and sub-headings are used herein to facilitate ease of understanding, and do not limit the scope of the disclosed techniques and embodiments to certain sections. Thus, the embodiments disclosed in the different sections may be used together with each other. Moreover, the examples herein using the 5G protocol and new air interface (NR) network architecture from 3GPP are merely for ease of understanding, and the disclosed techniques and embodiments may be practiced in other wireless systems using communication protocols different from the 3GPP protocol.

Fig. 2 depicts a block diagram representing an architecture of a communication device, such as a User Equipment (UE) terminal or wireless communication device 200. Terminal 200 may include one or more processor electronics 210, such as a microprocessor, implementing one or more of the wireless technologies presented herein. The terminal 200 may include transmitter electronics 215 and receiver electronics 220 to transmit and/or receive wireless signals over one or more communication interfaces, such as an antenna 220. In some embodiments, the transmitter electronics 215 and the receiver electronics 220 may be integrated into a single electronic transceiver unit or module. The terminal 200 may include other communication interfaces for transmitting and receiving data. The terminal 200 can include one or more memories 205 configured to store information such as data and/or instructions related to the methods disclosed herein. In some implementations, the processor electronics 210 may include at least a portion of transceiver electronics. In some embodiments, at least some of the disclosed techniques, modules, or functions are implemented using sequence generation module 225.

Embodiments for generating reference signals

Fig. 3A and 3B are block diagram representations of a portion of an apparatus in accordance with some embodiments of the disclosed technology. For example, FIG. 3A is a schematic diagram of reference signal generation based on π/2-BPSK. The binary sequence b (n) is modulated by pi/2-BPSK modulation module 302 and produces the output sequence d (n). Then, d (n) is precoded by DFT operation in a DFT (discrete fourier transform) module 304 and then mapped to REs for transmission in the frequency domain by a Resource Element (RE) mapping module 306. The RE mapping module 306 is connected to an IFFT (inverse fast fourier transform) module 308 for IFFT operation. The output of the IFFT module 308 corresponds to a time domain sequence. RE mapping and IFFT in the frequency domain is similar to the generation of OFDM (orthogonal frequency division multiplexing) signals.

The relationship between d (n) and b (n) for π/2-BPSK is given by:

where exp () is an exponential function and mod is a modulo operation.

When the length of the reference signal is relatively short, e.g., shorter than 30, a Computer Generated Sequence (CGS) may be used as a symbol of the reference signal. To obtain the desired/target sequence, various sequence selection criteria may be used during the search process, such as low PAPR, low autocorrelation, and low cross-correlation between the two sequences. To generate the sequence, the bit stream b is listed in Table 1, Table 2 and Table 3_u(n) may be used with pi/2-BPSK modulation techniques of lengths 12, 18, and 24, respectively.

Table 1: CGS for pi/2-BPSK with N-12

Table 2: CGS for pi/2 BPSK with N-18

Table 3: CGS for pi/2-BPSK with N-24

Fig. 3B shows an example of reference signal generation based on an 8-PSK modulation technique. The reference signal generated using 8-PSK is similar to pi/2-BPSK, e.g., 8-PSK modulation block 301 is used in place of pi/2-BPSK modulation block 302. Various sequence selection criteria may be used during the search process, such as low PAPR, low autocorrelation, and low cross-correlation between the two sequences.

The relationship between d (n) and b (n) for 8-PSK can be represented by equation (2). To generate the sequence, bit stream b as listed in Table 4_u(N) may be used with an 8-PSK modulation technique having a length N-6.

Table 4: CGS for 8-PSK with N-6

Embodiments for selecting at least one pair of sequences

In the current NR specifications, one-symbol DMRS (e.g., when the reference signal includes a single sequence) and two-symbol DMRS (e.g., when the reference signal includes two sequences) are supported for PUSCH. In the case of a two-symbol DMRS, two options are disclosed in this patent document:

option 1: a new sequence is designed for the two DMRS symbols that satisfies the predefined condition of joint autocorrelation. In some embodiments, the sequence set used in designing the two-symbol DMRS is different from the sequence set used in designing the one-symbol DMRS.

Option 2: a deterministic sequence pair is designed for the two DMRS symbols that satisfies a predefined condition for joint autocorrelation. In some embodiments, the sequence set used in designing the two-symbol DMRS may be the same sequence set as used in designing the one-symbol DMRS.

One advantage of option 2 over option 1 is that a single set of sequences may be used for both the one-symbol DMRS and the two-symbol DMRS, which saves memory (e.g., storage requirements) at the UE and/or the base station (gNB). Thus, it is disclosed herein how to design/select a two-symbol DMRS. For example, this document discusses how to select a sequence pair from a set of sequences such that the sequence pair may satisfy one or more search termination conditions. It should be understood that although the discussion herein is based on sequence pairs, such discussion is for illustrative purposes only. In some embodiments, for example, the sequence pairs may be included in the reference signal as M sequences arranged in a repeating hopping pattern denoted A, B, A, B, … …. In some embodiments, the M sequences may be based at least in part on an identification of at least a cell, a user, or a communication channel.

The autocorrelation of the sequence can be expressed as:

where d (·) denotes the sequence, d (·) denotes the conjugate of d (), N denotes the length of the sequence, and j is a cyclic shift.

If the sequence has perfect autocorrelation

In practice, it can be extremely difficult to generate a sequence with zero autocorrelation. For example, pi/2-BPSK based sequences (listed in tables 1-3) and 8-PSK based sequences (listed in Table 4) do not have perfect autocorrelation. Thus, in some embodiments employing two DMRS symbols, joint or combined autocorrelation may be used as a criterion to determine the pair of sequences to be used in the two DMRS symbols. Therefore, perfect (equal to zero) or nearly perfect (close to zero) joint autocorrelation is desired.

The joint autocorrelation of a sequence pair can be defined as:

wherein d is_a(n) and d_b(n) are the two sequences used in the two DMRS symbols.

This document is directed to selecting (or searching) sequence pairs (referred to herein as winning pairs) among a collection of computer-generated sequences such that a desired search termination condition is achieved. For example, the search termination condition may be based on a joint autocorrelation condition. For example, if the sequence set is represented as S1, S2, S3, joint auto-correlation of (S1, S2), (S1, S3), and (S2, S3) is calculated. These calculations are repeated over one or more cyclic shifts of S1, S2, S3. Herein, several embodiments for selecting winning sequence pairs are discussed. They are as follows.

Embodiment 1: a joint autocorrelation is computed for each sequence pair in the sequence set. Then, based on the joint autocorrelation values, the pair of sequences having the largest number of zero (or near zero) joint autocorrelation values at one or more cyclic shifts is selected as a winning pair. A near zero condition can be achieved by checking that the joint autocorrelation value does not exceed 0.00001. In this embodiment, the search termination condition is based on a maximum number of zero (or near zero) joint autocorrelation values.

Embodiment 2: a joint autocorrelation is computed for each sequence pair in the sequence set. Then, based on the joint autocorrelation values, the pair of sequences having the smallest maximum joint autocorrelation (e.g., below a threshold) at one or more cyclic shifts is selected as the winning pair. In this embodiment, the search termination condition is based on the minimum of the maximum joint autocorrelation values.

Embodiment 3: the joint variance of each sequence pair in the sequence set is calculated. Then, based on the joint variance value, the pair of sequences with the smallest maximum joint variance (e.g., below a threshold) over one or more cyclic shifts is selected as the winning pair. In this embodiment, the search termination condition is based on the minimum of the maximum joint variance values.

Embodiments 1 to 3 may be implemented individually or in combination. Examples of federated embodiments are discussed next.

Embodiment 4: the first combination of embodiment 1 and embodiment 2.

Step 1: the joint autocorrelation of each sequence pair in the sequence set is calculated based on equation (4) in all cyclic shifts or a specific cyclic shift. Among all cyclic shifts or a specific cyclic shift, pairs of maximum joint autocorrelation values are recorded in a first table (e.g., table 5A). The pair-wise number of zero (or near zero) joint autocorrelation values among all or a particular cyclic shift is recorded in a second table (e.g., table 5B).

Step 2: those sequence pairs with high joint autocorrelation, e.g., sequences with joint autocorrelation above a threshold, are excluded from the first table. The threshold may be related, at least in part, to the length of the sequences in the set of sequences (denoted as N). For example, when N-12 and pi/2-Binary Phase Shift Keying (BPSK) modulation technique is used, the threshold may be 0.3333. The threshold may be 0.2222 when N is 18 and pi/2-Binary Phase Shift Keying (BPSK) modulation techniques are used. The threshold may be 0.25 when N is 24 and pi/2-Binary Phase Shift Keying (BPSK) modulation techniques are used. When N is 6 and 8-PSK modulation technique is used, the threshold may be 0.4714. The remaining sequence pairs are labeled as a candidate set of sequence pairs for subsequent selection.

Step 3: sequence pairing is performed across the sequence sets until the pair with the smallest maximum joint autocorrelation can be selected from the first table. If a sequence (e.g., Sx) has been selected that pairs with another sequence (e.g., Sy), then all sequence pairs with sequence Sx may be excluded from the candidate set. The candidate set of sequence pairs is updated and step 3 is repeated until all sequences in the set have been paired. In some scenarios, multiple sequences may have the same maximum joint autocorrelation value given the sequences in a pair. Thus, to break the tie, the pair of sequences with the largest number of zero (or near zero) joint autocorrelation values is selected, as indicated in the second table. However, if there is another tie where the number of even zero (or near zero) joint auto-correlations is the same across multiple sequences, one of the multiple sequences is randomly selected for pairing with the given sequence. For example, given the sequence S1, if the sequence pairs (S1, S2), (S1, S3), (S1, S4) have the same maximum joint autocorrelation, the second table is used to determine the number of zero (or near zero) joint autocorrelation values for the sequence pairs (S1, S2), (S1, S3), (S1, S4). If the numbers of zero (or near zero) joint autocorrelation values of (S1, S2), (S1, S3), (S1, S4) are assumed to be 10, 12, 11, respectively, the sequence S3 is selected to pair with S1.

Embodiment 5: a second combination of embodiment 1 and embodiment 2.

Step 2: those sequence pairs having a small number of zero (or near zero) joint autocorrelation values (e.g., the number of zero (or near zero) joint autocorrelation values does not exceed a threshold) are excluded from the second table. The threshold may be related, at least in part, to the length of the sequences in the set of sequences (denoted as N). The remaining sequence pairs are labeled as a set of candidate sequence pairs for further down-selection.

Step 3: sequence pairing is performed across the sequence set until the sequence pair with the largest number of zero (or near zero) joint autocorrelation values can be selected from the second table. If a sequence (e.g., Sx) has been selected that pairs with another sequence (e.g., Sy), then all sequence pairs with sequence Sx may be excluded from the candidate set. The candidate set of sequence pairs is updated and step 3 is repeated until all sequences in the set have been paired. In some scenarios, multiple sequences may have the same maximum number of zero (or near zero) joint autocorrelation values given the sequences in a pair. Thus, to break the tie, the pair of sequences with the smallest maximum joint autocorrelation is selected, as indicated in the first table. However, if there is another tie in which even the largest joint auto-correlation is the same among the multiple sequences, one of the multiple sequences is randomly selected for pairing with the given sequence.

Table 5A: a first table in embodiment 1, wherein N is 12

Table 5B: second table in embodiment 1, where N is 12

Tables 5A and 5B correspond to the first table and the second table in embodiment 4 and embodiment 5, each of which has 30 rows and 30 columns corresponding to a sequence set of 30 sequences. As an example of discussion, if sequence 0 (i.e., the first column) is considered for the first symbol, table 5B indicates that the maximum number of zero joint autocorrelation values is 10. In other words, for sequence pairs (0, 0), (0, 2), (0, 4), (0, 15), (0, 16) and (0, 18), there are 10 cyclic shifts with zero joint autocorrelation values, implying that the second symbol can be selected from sequences 0, 2, 4, 15, 16 and 18. When performing a search, 30 sequences are considered collectively for the search termination to be reached.

Details of the procedure of embodiment 3 may be inferred from the procedure of embodiment 2 because the joint variance of each sequence pair may be calculated from joint autocorrelation, and herein, embodiment 4 or 5 is used as an example of selecting a winning sequence pair (e.g., shown in tables 6A, 7A, 8A, and 9A) to be included in a DMRS symbol. The first sequence is used in a first DMRS symbol and the second sequence is used in a second DMRS symbol. The CGS indices of the winning sequence pairs are listed in tables 6A, 7A, 8A and 9A. Specifically, tables 6A, 7A, 8A show winning sequence pairs for sequence lengths of 12, 18, 24, respectively, when the digital modulation technique is pi/2-Binary Phase Shift Keying (BPSK) and the size of the sequence set is 30. Table 9A shows winning sequence pairs for a sequence length of 6 when the digital modulation technique is 8-PSK and the size of the sequence set is 30.

Tables 6B, 7B, 8B, 9B show the average (i.e., mean) and maximum joint autocorrelation values for the winning pairs listed in tables 6A, 7A, 8A, 9A, respectively. For comparison purposes, the autocorrelation of a single symbol DMRS is also listed. Tables 6B, 7B, 8B, 9B indicate that the mean and maximum values of the joint autocorrelation of two-symbol DMRSs are reduced compared to a single-symbol DMRS. Lower joint autocorrelation means a flatter frequency response, which results in better channel estimation performance. Thus, the design/selection of winning pairs as disclosed herein provides at least one patentable benefit.

Table 6A: CGS pairing table showing indices for winning sequence pair of N-12

Table 6B: autocorrelation values for winning pairs in Table 5A

Table 7A: CGS pairing table showing indices for winning sequence pair of N-18

Table 7B: joint autocorrelation values for winning pairs in Table 6A

Table 8A: CGS pairing table showing indices for winning sequence pair of N-24

Table 8B: autocorrelation values for winning pairs in Table 7A

Table 9A: CGS pairing table showing indices for winning sequence pair of N-6

Table 9B: joint autocorrelation values for winning pairs in Table 8A

In some embodiments, the two DMRS symbols may or may not be adjacent to each other in the time domain. In some embodiments, the maximum joint autocorrelation value is associated with a cyclic shift that varies from 1 to (N-1). In some embodiments, the maximum joint autocorrelation value is associated with a predetermined cyclic shift based at least in part on N, e.g., the predetermined cyclic shift may be: when N is 6, j is 1, when N is 12, j is 2 or 3, when N is 18, j is 4 or 5, and when N is 24, j is 5 or 6.

Exemplary methods of the disclosed technology

Fig. 4 illustrates an example of a wireless communication method 400 for generating winning sequence pairs for use in reference signals in mobile communication technology. The method 400 includes: at step 410, a reference signal is transmitted from the wireless node using a digital modulation technique, wherein the reference signal includes M sequences (M ≧ 2) based on a search of a set of sequences in a manner such that the M sequences satisfy at least one condition.

In some embodiments, a method may be implemented at a receiving wireless node. The method can comprise the following steps: receiving data and a reference signal using a plurality of subcarriers, wherein the reference signal includes M sequences (M ≧ 2) over M symbols and is used for demodulating the data; and detecting the reference signal based at least in part on searching a set of sequences in a manner such that the M sequences satisfy at least one condition.

In some embodiments, the data and reference signals are transmitted on a Physical Uplink Shared Channel (PUSCH) or a Physical Uplink Control Channel (PUCCH). In other embodiments, the data includes uplink traffic data and uplink control information. In other embodiments, the reference signal is used to demodulate data. In one aspect, the sequences described and constructed by embodiments of the disclosed technology advantageously achieve improved demodulation performance due to their PAPR and autocorrelation characteristics.

The specification and drawings are to be regarded in an illustrative manner only, with the illustrative meaning being exemplary and do not imply ideal or preferred embodiments unless otherwise specified. As used herein, the use of "or" is intended to include "and/or" unless the context clearly indicates otherwise.

Some embodiments described herein are described in the general context of methods or processes, which may be implemented in one embodiment by a computer program product, embodied in a computer-readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. The computer-readable medium may include removable and non-removable storage devices, including but not limited to Read Only Memory (ROM), Random Access Memory (RAM), Compact Discs (CDs), Digital Versatile Discs (DVDs), and the like. Generally, program modules may include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Computer-or processor-executable instructions, associated data structures, and program modules represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes.

Some disclosed embodiments may be implemented as a device or module using hardware circuitry, software, or a combination thereof. For example, a hardware circuit implementation may include separate analog and/or digital components integrated as part of a printed circuit board, for example. Alternatively or additionally, the disclosed components or modules may be implemented as Application Specific Integrated Circuits (ASICs) and/or Field Programmable Gate Array (FPGA) devices. Some implementations may additionally or alternatively include a Digital Signal Processor (DSP), which is a special purpose microprocessor having an architecture optimized for the operational needs of digital signal processing associated with the disclosed functionality of the present application. Similarly, various components or sub-components within each module may be implemented in software, hardware, or firmware. Connections between modules and/or components within modules may be provided using any of the connection methods and media known in the art, including, but not limited to, communications over the internet, wired, or wireless networks using an appropriate protocol.

Although this document contains many specifics, these should not be construed as limitations on the scope of the claimed invention or of what may be claimed, but rather as descriptions of features specific to particular embodiments. Certain features that are described herein 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 claimed combination can in some cases be excised from the combination, and the claimed 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.

Only a few embodiments and examples are described and other embodiments, enhancements and variations can be made based on what is described and illustrated in this disclosure.

Claims

1. A method of wireless communication, comprising:

transmitting a reference signal from a wireless node using a digital modulation technique, wherein the reference signal comprises M sequences, M being greater than or equal to 2, the M sequences being based on searching a set of sequences in a manner such that the M sequences satisfy at least one condition.

2. The method according to claim 1, wherein the at least one condition associated with the M sequences is a joint autocorrelation value calculated as:

wherein d is_a(n) and d_b(N) represents a sequence pair of the M sequences, j is a cyclic shift of the two sequences, N is the length of the sequence in the sequence pair, which isWhen the entire sequence set is computed, the at least one condition is satisfied if the sequence pair has the largest number of zero joint autocorrelation values for each cyclic shift of the sequence pair.

3. The method according to claim 1, wherein the at least one condition associated with the M sequences is a joint autocorrelation value calculated as:

wherein d is_a(n) and d_b(N) denotes a pair of sequences of the M sequences, j is a cyclic shift of both sequences, N is a length of a sequence of the pair of sequences, wherein the at least one condition is satisfied if the pair of sequences has a minimum value of a maximum joint autocorrelation value for each cyclic shift of the pair of sequences when the entire set of sequences is computed.

4. The method according to claim 1, wherein the at least one search termination condition associated with the M sequences is a joint autocorrelation value calculated as:

wherein d is_a(n) and d_b(N) denotes a sequence pair of the M sequences, j being the cyclic shifts of both sequences, N being the length of the sequences in the sequence pair, wherein when calculating the entire sequence set, for each cyclic shift of the sequence pair, the sequence pair has the largest number of zero joint autocorrelation values, a first search termination condition is fulfilled, and when calculating the entire sequence set, for each cyclic shift of the sequence pair, the sequence pair has the smallest value of the largest joint autocorrelation values, a second search termination condition is fulfilled.

5. The method according to any of claims 2 to 4, wherein a maximum joint autocorrelation value is associated with the respective cyclic shifts varying from 1 to (N-1).

6. The method according to any of claims 2 to 4, wherein a maximum joint autocorrelation value is associated with a predetermined cyclic shift based at least in part on N.

7. The method of claim 6, wherein the predetermined cyclic shift comprises: when N is 6, j is 1, when N is 12, j is 2 or 3, when N is 18, j is 4 or 5, and when N is 24, j is 5 or 6.

8. The method of claim 1, wherein the M sequences are based at least in part on an identification of at least a cell, a user, or a communication channel.

9. The method of claim 1, wherein the wireless node is a User Equipment (UE) or a base station.

10. The method of claim 1, wherein the digital modulation technique is pi/2-Binary Phase Shift Keying (BPSK), and the size of the sequence set is 30, and N is equal to 12, 18, or 24.

11. The method of claim 1, wherein the digital modulation technique is octal phase shift keying (8-PSK), and the sequence set has a size of 30, and N equals 6.

12. The method of claim 10, wherein each sequence in the set of sequences corresponds to the following mathematical form:

where exp () is an exponential function, mod is a modulo operation, b_u(N) is the u-th sequence in the set of sequences, where u is an integer that indexes each sequence in the set of sequences, and u is 0, 1, … …, 29, and where N varies from 0 to N-1.

13. The method of claim 11, wherein each sequence in the set of sequences corresponds to the following mathematical form:

14. The method of claim 10, wherein N-12, and wherein, when M-2, the reference signal is a demodulation reference signal (DMRS) that includes first and second DMRS symbols identifiable by a computer-generated sequence (CGS) index, the CGS index including at least one of the following CGS indices:

15. the method of claim 10, wherein N-18, and wherein, when M-2, the reference signal is a demodulation reference signal (DMRS) that includes first and second DMRS symbols identifiable by a computer-generated sequence (CGS) index, the CGS index including at least one of the following CGS indices:

16. the method of claim 10, wherein N-24, and wherein, when M-2, the reference signal is a demodulation reference signal (DMRS) that includes first and second DMRS symbols identifiable by a computer-generated sequence (CGS) index, the CGS index including at least one of the following CGS indices:

17. the method of claim 11, wherein, when M-2, the reference signal is a demodulation reference signal (DMRS) comprising first and second DMRS symbols identifiable by a computer-generated sequence (CGS) index, the CGS index comprising at least one of the following CGS indices:

18. the method of any one or more of claims 2 to 4, wherein the zero joint autocorrelation value comprises a joint autocorrelation value that takes on a value of zero or that takes on a value close to zero.

19. The method of any one or more of claims 2 to 4, wherein the maximum joint autocorrelation value comprises a joint autocorrelation value that is below a specified threshold.

20. The method of claim 19, wherein when N-2, the specified threshold is 0.3333; when N is 18, the specified threshold is 0.2222; when N is 24, the specified threshold is 0.25; and when N is 6, the specified threshold is 0.4714.

21. A method of wireless communication, comprising:

receiving data and a reference signal at a wireless node using a plurality of subcarriers, wherein the reference signal comprises M sequences over M symbols and is used to demodulate the data, M being greater than or equal to 2; and

detecting the reference signal based at least in part on searching a set of sequences in a manner such that the M sequences satisfy at least one condition.

22. The method of any one or more of claims 1 to 21, wherein the M sequences are adjacent to each other or non-adjacent to each other on the time-domain representation.

23. The method of claim 1, wherein the M sequences comprise at least one pair of sequences A, B, the at least one pair of sequences A, B arranged in a hopping A, B, A, B, A, B, … … repeating pattern.

24. The method of any one of claims 1 to 23, wherein the reference signal is transmitted on a Physical Uplink Shared Channel (PUSCH) or a Physical Uplink Control Channel (PUCCH).

25. The method of any one or more of claims 10 or 14, wherein the sequence set corresponds to:

26. the method of any one or more of claims 10 or 15, wherein the sequence set corresponds to:

27. the method of any one or more of claims 10 or 16, wherein the sequence set corresponds to:

28. the method of any one or more of claims 11 or 17, wherein the sequence set corresponds to:

29. a wireless communication device comprising a memory and a processor, wherein the processor reads code from the memory area and implements the method of any of claims 1 to 28.

30. A computer readable program storage 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 28.