Reference signals for wireless communication systems

Abstract

Embodiments of the present invention relate to a first communication device and a second communication device for channel estimation using a novel reference signal in a communication system. The reference signal is based on a modulation sequence in a set of QA modulation sequences having a length L > = 1. The set of the QA modulation sequences comprises Q modulation sequence subsets, Q is greater than or equal to 1, each modulation sequence subset comprises A modulation sequences, and A is greater than or equal to 1. The correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset satisfies a first correlation criterion; a correlation between any two reference signals based on any two modulation sequences in the respective any two different subsets of modulation sequences satisfies a second correlation criterion. The correlation between any two reference signals based on any two modulation sequences in the same subset of modulation sequences is lower than the correlation between any two reference signals based on any two modulation sequences in the corresponding any two different subsets of modulation sequences. The invention further relates to a corresponding method and to a computer program.

Description

Technical Field

[0001] Embodiments of the present invention relate to a reference signal for a wireless communication system, wherein the wireless communication system is implemented by a first communication device and a second communication device using the reference signal. In addition, the present invention also relates to a corresponding method and a computer program. Background Art

[0002] For most wireless communication systems (e.g., 3GPP 5G), accurate channel state information (CSI) is crucial in ensuring efficient and reliable data transmission between the transmitter and the receiver. CSI enables the transmitter to perform appropriate precoding design, modulation and coding scheme (MCS) selection, power control, user scheduling, etc. to adapt to the dynamically changing wireless channel, while also enabling the receiver to perform correct signal detection and interference avoidance.

[0003] In a time-division duplexed (TDD) cellular communication system, it is usually assumed that the uplink (UL) and downlink (DL) propagation channels between the user equipment (UE) and the base station (BS) / transmit-receive point (TRP) are the same. That is, channel reciprocity holds. The CSI at the BS / TRP is obtained by having the UE send a sounding reference signal (SRS) to the BS / TRP. The BS / TRP then estimates the UL channel based on the SRS received from the UE and interprets the UL channel as a DL channel for transmitter design for future DL data transmission. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a solution to reduce or solve the shortcomings and problems of traditional solutions.

[0005] Another object of the embodiments of the present application is to provide a solution to alleviate the channel aging problem.

[0006] Another object of the embodiments of the present application is to provide a solution to the problem of intra-cell / inter-cell cross-reference signal interference.

[0007] The above objects and other objects are achieved by the subject matter claimed in the independent claims. Further embodiments of the invention are provided in the dependent claims.

[0008] According to a first aspect of the present application, the above-mentioned object and other objects are achieved by a first communication device, wherein the first communication device is configured to perform the following steps:

[0009] Acquire a reference signal, wherein the reference signal is based on a modulation sequence in a set of QA modulation sequences of length L≥1, the set of QA modulation sequences includes Q modulation sequence subsets, Q≥1, each modulation sequence subset includes A modulation sequences, A≥1, wherein the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset meets a first correlation standard; the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets meets a second correlation standard; the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset is lower than the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets; send the reference signal.

[0010] According to the first aspect, the advantage of the first communication device is that a set of QA modulation sequences can be used to generate a larger number of reference signals, which is Q times the number of existing reference signals generated in the same time-frequency resources. In the same time-frequency resources, the larger number of reference signals can be used to support a larger number of first communication devices in each cell, thereby achieving a higher system throughput. Another advantage is that in the same frequency resources, the same number of first communication devices in each cell can support a shorter reference signal transmission period, thereby alleviating the channel aging problem. Yet another advantage is that in the reduced time-frequency resources, the same number of first communication devices in each cell can support the same reference signal transmission period, so that the reference signal transmissions in adjacent cells can be coordinated to occupy orthogonal time-frequency resources, thereby alleviating cross-interference between cells.

[0011] According to the first aspect, in an implementation of the first communication device, the first correlation criterion defines that a reference signal based on a modulation sequence in a modulation sequence subset is orthogonal to consecutive multiple cyclic shifted versions of another reference signal based on another modulation sequence in the same modulation sequence subset.

[0012] The advantage of this implementation is that, according to the first correlation criterion, under multiple consecutive cyclic shift delay offsets, the periodic cross-correlation function of two reference signals based on any two modulation sequences in the same modulation sequence subset is zero. Therefore, the A reference signals based on all A modulation sequences in the same modulation sequence subset have a zero correlation zone (zero correlation zone, ZCZ), and the length of the ZCZ is equal to the number of consecutive cyclic shift delay offsets when the periodic cross-correlation function is zero. When a reference signal based on any modulation sequence in the same modulation sequence subset is sent from the same or different first communication devices through an appropriate timing advance (timing advance, TA) adjustment, and the maximum delay of the wireless channel experienced by the reference signal is not greater than the length of the ZCZ of all reference signals based on all modulation sequences in the same modulation sequence subset, interference between these reference signals at the receiver can be completely avoided, which means that the wireless channel experienced by the reference signal can be accurately estimated.

[0013] According to the first aspect, in an implementation of the first communication device, the second correlation criterion defines that the cross-correlation of multiple consecutive cyclic shifted versions of a reference signal based on a modulation sequence in a modulation sequence subset and another reference signal based on another modulation sequence in a different modulation sequence subset is lower than a predetermined threshold.

[0014] The advantage of this implementation is that, according to the second correlation criterion, under a plurality of consecutive cyclic shift delay offsets, the amplitude of the periodic cross-correlation function of two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets is lower than a predetermined threshold. Therefore, all QA reference signals based on all QA modulation sequences in the set of modulation sequences have a low correlation zone (LCZ), the length of which is equal to the minimum of the following two values: the number of consecutive cyclic shift delay offsets when the amplitude of the periodic cross-correlation function is lower than the predetermined threshold, and the ZCZ length of all A reference signals based on all A modulation sequences in each modulation sequence subset of the Q modulation sequence subsets. When a reference signal based on any modulation sequence in a set of QA modulation sequences is sent from the same or different first communication devices through appropriate TA adjustment, and the maximum delay of the wireless channel experienced by the reference signal is not greater than the length of the LCZ of all reference signals of all modulation sequences in the set of the modulation sequence, the interference between the reference signals at the receiver is low, and the LCZ characteristics of all reference signals of all modulation sequences in the set of the modulation sequence can ensure that the interference between these reference signals at the receiver (also called intra-cell cross interference) can be efficiently separated by a channel estimation method based on compressed sensing (CS). This means that even if there is intra-cell cross interference, the wireless channel experienced by the reference signal can be accurately estimated.

[0015] According to the first aspect, in an implementation of the first communication device, at least one modulation sequence in the set of QA modulation sequences is based on a first sequence in a first sequence set with a length of A, a second sequence in a second sequence set with a length of B≥1, and a third sequence with a length of L, wherein the first sequence set includes Q first sequence subsets, each first sequence subset includes A constant envelope sequences, wherein all A constant envelope sequences are mutually orthogonal; the second sequence set includes Q constant envelope sequences, wherein the correlation between any two second sequences in the Q second sequence sets satisfies a third correlation criterion; and the third sequence is a constant envelope sequence.

[0016] The advantage of this implementation is that this modulation sequence construction method ensures that all A reference signals based on all A modulation sequences in each modulation sequence subset in the Q modulation sequence subsets meet the first correlation standard, and all QA reference signals based on all QA modulation sequences in the set of the entire modulation sequence meet the second correlation standard. Specifically, the mutual orthogonality of all A first sequences in each first sequence subset in the Q first sequence subsets ensures that the reference signals based on the corresponding A modulation sequences in each modulation sequence subset in the Q modulation sequence subsets meet the first correlation standard. The third correlation standard for the second sequence also ensures that the reference signals based on the corresponding QA modulation sequences in the set of the entire modulation sequence meet the second correlation standard.

[0017] According to the first aspect, in an implementation of the first communication device, the modulation sequences in the set of QA modulation sequences are based on element-by-element multiplication of periodic repetitions of the first sequence, the second sequence, and the third sequence.

[0018] The advantage of this implementation is that it provides an explicit and efficient method for generating a modulation sequence in the set of modulation sequences. Specifically, the length L of the third sequence is the same as the length of the modulation sequence, while the lengths of the first sequence and the second sequence are shorter than the length of the modulation sequence. In order to generate the modulation sequence, the first sequence and the second sequence need to be periodically extended to the same length L as the modulation sequence before an element-by-element multiplication operation can be performed.

[0019] According to the first aspect, in an implementation of the first communication device, the first sequence in each first sequence subset is a column of an A×A constant envelope orthogonal matrix, or is based on the element-by-element multiplication of the columns of the A×A constant envelope orthogonal matrix and a cover sequence, wherein the A×A constant envelope orthogonal matrix is ​​any one of the following: an A×A discrete Fourier transform (DFT) matrix, an A×A Hadamard matrix, an A×A matrix whose columns are different cyclic shift versions of a constant-amplitude zero auto-correlation (CAZAC) sequence with a length of A and including a Zadoff-Chu (ZC) sequence, or an A×A matrix whose columns are different cyclic shift versions of a modulated CAZAC (mCAZAC) sequence with a length of A; the cover sequence is a constant envelope sequence with a length of A, which is the same for all the first sequences in each first sequence subset, and can be the same or different for different first sequence subsets.

[0020] The advantage of this implementation method is that it can ensure that the A first sequences constructed in each first sequence subset of the Q first sequence subsets are mutually orthogonal, thereby ensuring that all A reference signals based on all A modulation sequences in each modulation sequence subset of the Q modulation sequence subsets meet the first correlation standard.

[0021] According to the first aspect, in an implementation of the first communication device, the second sequence is common to all modulation sequences in the same modulation sequence subset, and is different for modulation sequences in different modulation sequence subsets, wherein the length B of the second sequence is an integer, and the integer is a multiple of A and a factor of L; the second sequence is any one of the following: an all-"1" sequence of length B, a CAZAC / mCAZAC sequence of length B, a CAZAC / mCAZAC sequence of length less than B and periodically extended to length B, or a CAZAC / mCAZAC sequence of length greater than B and truncated to length B.

[0022] The advantage of this implementation is that it can ensure that the second sequence constructed in the Q second sequence sets meets the third correlation standard. In addition, by making the length B of the second sequence an integer, which is a multiple of A and a factor of L, it can be ensured that the QA reference signals based on the QA modulation sequences in the set of the entire modulation sequence meet the second correlation standard. In addition, selecting different (periodically extended / truncated) CAZAC / mCAZAC sequences for the second sequence may result in different peak-to-average power ratios (PAPR) of the obtained reference signal. Therefore, an additional advantage of this implementation is that by selecting a suitable (periodically extended / truncated) CAZAC / mCAZAC sequence as the second sequence, the obtained reference signal can be achieved to have a low PAPR. For example, when the second sequence is selected as a ZC sequence with a prime length close to B, there will be about B candidate ZC root indexes, and the second sequence can be selected as a ZC sequence with an optimized root index, so that a reference signal with a low PAPR can be obtained.

[0023] According to the first aspect, in an implementation of the first communication device, the length B of the second sequence is predefined; or the first communication device is used to receive a control signal indicating the length B of the second sequence, wherein the length B of the second sequence is determined by a length of The bit string indicates that the operator Returns the smallest integer not less than x, N B is the number of integers in the set of integers that are multiples of A and factors of L; or is the number of integers in a predefined subset of the set of integers that are multiples of A and factors of L.

[0024] The advantage of this implementation is that the first communication device can obtain necessary signaling information to determine the length B of the second sequence for generating a modulation sequence and further generating a reference signal.

[0025] According to the first aspect, in an implementation manner of the first communication device, the third correlation criterion defines that a mutual correlation of all cyclic shift versions of a second sequence in the second sequence set and another second sequence in the second sequence set is lower than a predetermined threshold.

[0026] The advantage of this implementation is that, according to the third correlation criterion, the amplitude of the periodic cross-correlation function of any two second sequences in the set of Q second sequences is lower than the predetermined threshold value under all cyclic shift delay offsets. This and the condition that the length B of the second sequence is selected as an integer, which is a multiple of the number A of modulation sequences in each modulation sequence subset and a factor of the length L of the modulation sequence, together ensure that all QA reference signals based on all QA modulation sequences in the set of modulation sequences have a certain length of LCZ in their periodic cross-correlation functions. When reference signals based on any modulation sequence in the set of QA modulation sequences are sent from the same or different first communication devices through appropriate TA adjustment, and the maximum delay of the wireless channel experienced by these reference signals is not greater than the length of the LCZ of all reference signals of all modulation sequences in the set of modulation sequences, the LCZ characteristics of these reference signals can ensure that the interference (also called intra-cell cross-interference) between these reference signals at the receiver is low, and can be efficiently separated by a CS-based channel estimation method, so that even if there is intra-cell cross-interference, the wireless channel experienced by these reference signals can be accurately estimated.

[0027] According to the first aspect, in an implementation manner of the first communication device, the third sequence is any one of the following: a CAZAC / mCAZAC sequence with a length of L, a CAZAC / mCAZAC sequence with a length less than L and periodically extended to a length of L, or a CAZAC / mCAZAC sequence with a length greater than L and truncated to a length of L.

[0028] The advantage of this implementation is that it can ensure that the constructed third sequence has a constant envelope. In addition, by selecting different third sequences using any of the above methods, for example, based on different CAZAC / mCAZAC sequences or especially ZC sequences with different root indexes, a set of multiple modulation sequences can be constructed to generate multiple reference signal sets for different cells, and the cross-correlation between reference signals in different reference signal sets is low.

[0029] According to the first aspect, in an implementation of a first communication device, the first communication device is used to perform the following steps: sending the reference signal by mapping the modulation sequence onto a set of L subcarriers out of N consecutive subcarriers, N≥L, wherein the N consecutive subcarriers are divided into t subbands including an equal number of consecutive subcarriers; the set of L subcarriers includes A subcarriers from each subband, and the positions of the A subcarriers in each subband are the same for all of the t subbands.

[0030] The advantage of this implementation is that the frequency resources occupied by the modulation sequence present a block repetition structure, which can ensure that the reference signal based on any modulation sequence in the set of modulation sequences is orthogonal to multiple consecutive cyclic shift versions of itself, that is, each reference signal has a zero auto-correlation zone (ZAZ), the length of which is equal to the number of consecutive cyclic shift values ​​when the periodic autocorrelation function of each reference signal is zero. When such a reference signal is transmitted on a wireless channel with a maximum delay not greater than the length of the ZAZ, the channel experienced by the reference signal can be accurately estimated at the receiver, for example, by first periodically correlating the received reference signal with a locally generated reference signal that is the same as the transmitted reference signal, and then using a suitable detection window for the correlation output, the length of which is not less than the maximum channel delay and not greater than the length of the ZAZ. The estimated channel of the transmitted reference signal can be obtained from the output of the detection window.

[0031] According to the first aspect, in an implementation manner of the first communication device, the value of Q is predefined; or the first communication device is configured to receive a control signal indicating the value of Q.

[0032] The advantage of this implementation method is that the first communication device can obtain the necessary signaling information to determine the number of first sequence subsets and the number of modulation sequence subsets and the number of reference signal subsets, so that the identification of the modulation sequence can be correctly determined based on the control signal indicating the identification of the modulation sequence.

[0033] According to the first aspect, in an implementation of a first communication device, the first communication device is configured to receive a control signal indicating an identifier of the modulation sequence, wherein the identifier of the modulation sequence is indicated in the following manner: A single bit string of bits, where N group is the number of reference signal groups defined in the communication system (500); or the lengths are and Two bit strings of , wherein the first bit string indicates a reference signal group index, and the second bit string indicates an index of a modulation sequence in a set of modulation sequences associated with the reference signal group index; or the lengths are and The invention provides three bit strings, wherein the first bit string indicates a reference signal group index, the second bit string indicates an index of a modulation sequence subset in a set of modulation sequences associated with the reference signal group index, and the third bit string indicates an index of a modulation sequence in the modulation sequence subset.

[0034] The advantage of this implementation is that the second communication device can indicate the identification of the modulation sequence to the first communication device, so that the first communication device can generate the correct modulation sequence and then generate the correct reference signal. This implementation also provides identification signaling in several flexible and efficient ways, thereby reducing signaling overhead.

[0035] According to a second aspect of the present invention, the above and other objects are achieved by a second communication device, wherein the second communication device is configured to perform the following steps:

[0036] Receive a reference signal; obtain a modulation sequence from a set of QA modulation sequences of length L≥1, wherein the set of QA modulation sequences includes Q modulation sequence subsets, Q≥1, each modulation sequence subset includes A modulation sequences, A≥1, wherein the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset meets a first correlation criterion; the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets meets a second correlation criterion; the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset is lower than the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets; estimate a wireless channel based on the received reference signal and the modulation sequence.

[0037] According to the second aspect, the advantage of the second communication device is that a set of QA modulation sequences can be used to generate a larger number of reference signals, which is Q times the number of existing reference signals generated in the same time-frequency resources. In the same time-frequency resources, the larger number of reference signals can be used to support a larger number of first communication devices in each cell, thereby achieving a higher system throughput. Another advantage is that in the same frequency resources, the same number of first communication devices in each cell can support a shorter reference signal transmission period, thereby alleviating the channel aging problem. Yet another advantage is that in the reduced time-frequency resources, the same number of first communication devices in each cell can support the same reference signal transmission period, so that the reference signal transmissions in adjacent cells can be coordinated to occupy orthogonal time-frequency resources, thereby alleviating cross-interference between cells.

[0038] According to the second aspect, in an implementation of the second communication device, the first correlation criterion defines that a reference signal based on a modulation sequence in a modulation sequence subset is orthogonal to consecutive multiple cyclic shifted versions of another reference signal based on another modulation sequence in the same modulation sequence subset.

[0039] The advantage of this implementation is that, according to the first correlation criterion, under multiple consecutive cyclic shift delay offsets, the periodic cross-correlation function of any two reference signals based on any two modulation sequences in the same modulation sequence subset is zero. Therefore, all A reference signals based on all A modulation sequences in the same modulation sequence subset have a ZCZ, the length of which is equal to the number of consecutive cyclic shift delay offsets when the periodic cross-correlation function is zero. When reference signals based on any modulation sequence in the same modulation sequence subset are sent from the same or different first communication devices through appropriate TA adjustment, and the maximum delay of the wireless channel experienced by these reference signals is not greater than the length of the ZCZ of all reference signals based on all modulation sequences in the same modulation sequence subset, interference between these reference signals at the receiver can be completely avoided, which means that the wireless channel experienced by the reference signal can be accurately estimated.

[0040] According to the second aspect, in an implementation of the second communication device, the second correlation criterion defines that the cross-correlation of multiple consecutive cyclic shifted versions of a reference signal based on a modulation sequence in a modulation sequence subset and another reference signal based on another modulation sequence in a different modulation sequence subset is lower than a predetermined threshold.

[0041] The advantage of this implementation is that, according to the second correlation criterion, under a plurality of consecutive cyclic shift delay offsets, the amplitude of the periodic cross-correlation function of any two reference signals based on any two modulation sequences in the corresponding arbitrary two different modulation sequence subsets is lower than a predetermined threshold. Therefore, all QA reference signals based on all QA modulation sequences in the set of modulation sequences have an LCZ, and the length of the LCZ is equal to the minimum of the following two values: the number of consecutive multiple cyclic shift delay offsets when the amplitude of the periodic cross-correlation function is lower than the predetermined threshold, and the ZCZ length of all A reference signals based on all A modulation sequences in each modulation sequence subset of the Q modulation sequence subsets. When reference signals based on any modulation sequence in the set of QA modulation sequences are sent from the same or different first communication devices through appropriate TA adjustment, and the maximum delay of the wireless channel experienced by these reference signals is not greater than the length of the LCZ of all reference signals based on all modulation sequences in the set of modulation sequences, the interference between the reference signals at the receiver is low, and the LCZ characteristics of all reference signals based on all modulation sequences in the set of modulation sequences can ensure that the interference between these reference signals at the receiver (also known as intra-cell cross interference) can be efficiently separated by a CS-based channel estimation method. This means that the radio channel experienced by the reference signal can be accurately estimated even in the presence of intra-cell cross interference.

[0042] According to the second aspect, in an implementation of the second communication device, at least one modulation sequence in the set of A modulation sequences is based on a first sequence in a first sequence set with a length of A, a second sequence in a second sequence set with a length of B≥1, and a third sequence with a length of L, wherein the first sequence set includes Q first sequence subsets, each first sequence subset includes A constant envelope sequences, wherein all A constant envelope sequences are mutually orthogonal; the second sequence set includes Q constant envelope sequences, wherein the correlation between any two second sequences in the Q second sequence sets satisfies a third correlation criterion; and the third sequence is a constant envelope sequence.

[0043] The advantage of this implementation is that this modulation sequence construction method ensures that all A reference signals based on all A modulation sequences in each modulation sequence subset in the Q modulation sequence subsets meet the first correlation standard, and all QA reference signals based on all QA modulation sequences in the set of the entire modulation sequence meet the second correlation standard. Specifically, the mutual orthogonality of all A first sequences in each first sequence subset in the Q first sequence subsets ensures that the A reference signals based on the corresponding A modulation sequences in each modulation sequence subset in the Q modulation sequence subsets meet the first correlation standard. The third correlation standard for the second sequence also ensures that the QA reference signals based on the corresponding QA modulation sequences in the set of the entire modulation sequence meet the second correlation standard.

[0044] According to the second aspect, in an implementation of the second communication device, the modulation sequences in the set of QA modulation sequences are based on element-by-element multiplication of periodic repetitions of the first sequence, the second sequence, and the third sequence.

[0045] The advantage of this implementation is that it provides an explicit and efficient method for generating a modulation sequence in the set of modulation sequences. Specifically, the length L of the third sequence is the same as the length of the modulation sequence, while the lengths of the first sequence and the second sequence are shorter than the length of the modulation sequence. In order to generate the modulation sequence, the first sequence and the second sequence need to be periodically extended to the same length L as the modulation sequence before an element-by-element multiplication operation can be performed.

[0046] According to the second aspect, in an implementation of the second communication device, the first sequence in each first sequence subset is a column of an A×A constant envelope orthogonal matrix, or is based on the element-by-element multiplication of the columns of the A×A constant envelope orthogonal matrix and a cover sequence, wherein the A×A constant envelope orthogonal matrix is ​​any one of the following: an A×ADFT matrix, an A×A Hadamard matrix, an A×A matrix whose columns are different cyclic shift versions of a CAZAC sequence with a length of A and including a ZC sequence, or an A×A matrix whose columns are different cyclic shift versions of an mCAZAC sequence with a length of A; the cover sequence is a constant envelope sequence with a length of A, which is the same for all the first sequences in each first sequence subset, and can be the same or different for different first sequence subsets.

[0047] The advantage of this implementation method is that it can ensure that the A first sequences constructed in each first sequence subset of the Q first sequence subsets are mutually orthogonal, thereby ensuring that all A reference signals based on all A modulation sequences in each modulation sequence subset of the Q modulation sequence subsets meet the first correlation standard.

[0048] According to the second aspect, in an implementation of the second communication device, the second sequence is common to all modulation sequences in the same modulation sequence subset, and is different for modulation sequences in different modulation sequence subsets, wherein the length B of the second sequence is an integer, and the integer is a multiple of A and a factor of L; the second sequence is any one of the following: an all-"1" sequence of length B, a CAZAC / mCAZAC sequence of length B, a CAZAC / mCAZAC sequence of length less than B and periodically extended to length B, or a CAZAC / mCAZAC sequence of length greater than B and truncated to length B.

[0049] The advantage of this implementation is that it can ensure that the second sequence constructed in the Q second sequence sets meets the third correlation standard. In addition, by making the length B of the second sequence an integer, which is a multiple of A and a factor of L, it can be ensured that the QA reference signals based on the QA modulation sequences in the set of the entire modulation sequence meet the second correlation standard. In addition, selecting different (periodically extended / truncated) CAZAC / mCAZAC sequences for the second sequence may result in different PAPRs of the obtained reference signal. Therefore, an additional advantage of this implementation is that by selecting a suitable (periodically extended / truncated) CAZAC / mCAZAC sequence as the second sequence, it can be achieved that the obtained reference signal has a low PAPR. For example, when the second sequence is selected as a ZC sequence with a prime length close to B, there will be about B candidate ZC root indexes, and the second sequence can be selected as a ZC sequence with an optimized root index, so that a reference signal with a low PAPR can be obtained.

[0050] According to the second aspect, in an implementation of the second communication device, the length B of the second sequence is predefined; or the second communication device is used to send a control signal indicating the length B of the second sequence, wherein the length B of the second sequence is a length of The bit string indicates that N B is the number of integers in the set of integers that are multiples of A and factors of L; or is the number of integers in a predefined subset of the set of integers that are multiples of A and factors of L.

[0051] The advantage of this implementation is that the second communication device can send necessary signaling information to the first communication device so that the first communication device can determine the length B of the second sequence for generating a modulation sequence and further generating a reference signal.

[0052] According to the second aspect, in an implementation of the second communication device, the third correlation criterion defines that a mutual correlation of all cyclic shift versions of a second sequence in the second sequence set and another sequence in the second sequence set is lower than a predetermined threshold.

[0053] The advantage of this implementation is that, according to the third correlation criterion, the amplitude of the periodic cross-correlation function of any two second sequences in the set of Q second sequences is lower than the predetermined threshold value under all cyclic shift delay offsets. This and the condition that the length B of the second sequence is selected as an integer, which is a multiple of the number A of modulation sequences in each modulation sequence subset and a factor of the length L of the modulation sequence, together ensure that all QA reference signals based on all QA modulation sequences in the set of modulation sequences have a certain length of LCZ in their periodic cross-correlation functions. When reference signals based on any modulation sequence in the set of QA modulation sequences are sent from the same or different first communication devices through appropriate TA adjustment, and the maximum delay of the wireless channel experienced by these reference signals is not greater than the length of the LCZ of all reference signals of all modulation sequences in the set of modulation sequences, the LCZ characteristics of these reference signals can ensure that the interference (also called intra-cell cross-interference) between these reference signals at the receiver is low, and can be efficiently separated by a CS-based channel estimation method, so that even if there is intra-cell cross-interference, the wireless channel experienced by these reference signals can be accurately estimated.

[0054] According to the second aspect, in an implementation manner of the second communication device, the third sequence is any one of the following: a CAZAC / mCAZAC sequence with a length of L, a CAZAC / mCAZAC sequence with a length less than L and periodically extended to a length of L, or a CAZAC / mCAZAC sequence with a length greater than L and truncated to a length of L.

[0055] The advantage of this implementation is that it can ensure that the constructed third sequence has a constant envelope. In addition, by selecting different third sequences using any of the above methods, for example, based on different CAZAC / mCAZAC sequences or especially ZC sequences with different root indexes, a set of multiple modulation sequences can be constructed to generate multiple reference signal sets for different cells, and the mutual correlation between the modulation sequences in the sets of different modulation sequences is low.

[0056] According to the second aspect, in an implementation of a second communication device, the second communication device is used to perform the following steps: receiving the reference signal on a set of L subcarriers out of N consecutive subcarriers, N≥L, wherein the N consecutive subcarriers are divided into t subbands including an equal number of consecutive subcarriers; the set of L subcarriers includes A subcarriers from each subband, and the positions of the A subcarriers in each subband are the same for all of the t subbands.

[0057] The advantage of this implementation is that the frequency resources occupied by the modulation sequence present a block repetition structure, which can ensure that the reference signal based on any modulation sequence in the set of modulation sequences is orthogonal to multiple consecutive cyclic shift versions of itself, that is, each reference signal based on each modulation sequence has a zero auto-correlation zone (ZAZ), and the length of the ZAZ is equal to the number of consecutive cyclic shift values ​​when the periodic autocorrelation function of each reference signal is zero. When the reference signal is sent on a wireless channel with a maximum delay not greater than the length of the ZAZ, the channel experienced by the reference signal can be accurately estimated at the receiver, for example, by first periodically correlating the received reference signal with a locally generated reference signal that is the same as the transmitted reference signal, and then using a suitable detection window for the correlation output, the length of which is not less than the maximum channel delay and not greater than the length of the ZAZ. Then, the estimated channel of the transmitted reference signal can be obtained from the output of the detection window.

[0058] According to the second aspect, in an implementation manner of the second communication device, the value of Q is predefined; or the second communication device is configured to send a control signal indicating the value of Q.

[0059] The advantage of this implementation method is that the second communication device can send necessary signaling information to the first communication device so that the first communication device can determine the number of first sequence subsets and the number of modulation sequence subsets and the number of reference signal subsets, so that the identification of the modulation sequence can be correctly determined based on the control signal indicating the identification of the modulation sequence.

[0060] According to the second aspect, in an implementation of the second communication device, the second communication device is used to send a control signal indicating an identifier of the modulation sequence, wherein the identifier of the modulation sequence is indicated in the following manner: comprising A single bit string of bits, where N group is the number of reference signal groups defined in the communication system (500); or the lengths are and Two bit strings of , wherein the first bit string indicates a reference signal group index, and the second bit string indicates an index of a modulation sequence in a set of modulation sequences associated with the reference signal group index; or the lengths are and The invention provides three bit strings, wherein the first bit string indicates a reference signal group index, the second bit string indicates an index of a modulation sequence subset in a set of modulation sequences associated with the reference signal group index, and the third bit string indicates an index of a modulation sequence in the modulation sequence subset.

[0061] The advantage of this implementation is that the second communication device can indicate the identification of the modulation sequence to the first communication device, so that the first communication device can generate the correct modulation sequence and then generate the correct reference signal. This implementation also provides identification signaling in several flexible and efficient ways, thereby reducing signaling overhead.

[0062] According to a third aspect of the present invention, the above and other objects are achieved by a method for a first communication device, the method comprising the following steps:

[0063] Acquire a reference signal, wherein the reference signal is based on a modulation sequence in a set of QA modulation sequences of length L≥1, the set of QA modulation sequences includes Q modulation sequence subsets, Q≥1, each modulation sequence subset includes A modulation sequences, A≥1, wherein the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset meets a first correlation standard; the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets meets a second correlation standard; the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset is lower than the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets; send the reference signal.

[0064] The method provided in the third aspect can be extended to an implementation corresponding to the implementation of the first communication device provided in the first aspect. Therefore, the implementation of the method includes one or more features of the corresponding implementation of the first communication device.

[0065] The advantages of the method according to the third aspect are the same as the advantages of the corresponding implementation of the first communication device according to the first aspect.

[0066] According to a fourth aspect of the present invention, the above and other objects are achieved by a method for a second communication device, the method comprising the following steps:

[0067] Obtain a modulation sequence from a set of QA modulation sequences of length L≥1, wherein the set of QA modulation sequences includes Q modulation sequence subsets, Q≥1, each modulation sequence subset includes A modulation sequences, A≥1, wherein the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset satisfies a first correlation standard; the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets satisfies a second correlation standard; the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset is lower than the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets;

[0068] A wireless channel is estimated based on the received reference signal and the modulation sequence.

[0069] The method provided in the fourth aspect can be extended to an implementation manner corresponding to the implementation manner of the second communication device provided in the second aspect. Therefore, the implementation manner of the method includes one or more features of the corresponding implementation manner of the second communication device.

[0070] The advantages of the method according to the fourth aspect are the same as the advantages of the corresponding implementation of the second communication device according to the second aspect.

[0071] An embodiment of the present invention further relates to a computer program, characterized by a program code, when the program code is executed by at least one processor, the program code causes the at least one processor to perform any method provided by the embodiment of the present invention. In addition, an embodiment of the present invention further relates to a computer program product, comprising a computer-readable medium and the computer program, wherein the computer program is included in the computer-readable medium and may include one or more of the following groups: read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), flash memory, electrically erasable PROM (EEPROM), hard disk drive, etc.

[0072] Other applications and advantages of embodiments of the present invention will be apparent from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The accompanying drawings are intended to illustrate and explain different embodiments of the present invention, in which:

[0074] Figure 1 A first communication device according to an embodiment of the present invention is shown;

[0075] Figure 2 A flow chart of a method for a first communication device according to an embodiment of the present invention is shown;

[0076] Figure 3 A second communication device according to an embodiment of the present invention is shown;

[0077] Figure 4 A flow chart of a method for a second communication device according to an embodiment of the present invention is shown;

[0078] Figure 5 A communication system according to an embodiment of the present invention is shown;

[0079] Figure 6 shows a common frequency resource used for a reference signal;

[0080] Figure 7 A signaling diagram of control signaling according to an embodiment of the present invention is shown;

[0081] FIG8 shows some performance results of an embodiment of the present invention;

[0082] FIG. 9 shows some other performance results of an embodiment of the present invention. DETAILED DESCRIPTION

[0083] The UL SRS-based channel estimation mechanism described above has two main problems, namely, channel aging and interference. The channel aging problem is caused by the dynamic nature of the wireless propagation channel. In the time interval between UL SRS transmission and DL data transmission, the channel may change due to UE mobility and / or environmental changes around the UE or BS / TRP, resulting in a channel mismatch experienced by the UL SRS and DL data. This mismatch is more obvious when the time interval is large and / or the UE mobility is high. Therefore, the DL precoding design at the BS / TRP becomes inefficient and causes severe interference between data streams of the same or different UEs at the UE receiver, which significantly reduces the achievable DL throughput of the communication system. In order to ensure efficient transmission of DL data based on UL channel estimation, it is usually necessary to keep the time interval as short as possible, so a shorter SRS transmission period is required to avoid severe channel aging.

[0084] The interference problem is caused by the concurrent transmission of multiple SRS on the same time-frequency resources. In a cellular communication system containing multiple cells and multiple UEs in each cell, the allocated SRS time-frequency resources are usually kept as small as possible to leave more time-frequency resources for UL / DL data transmission. Therefore, it is impossible to allocate dedicated time-frequency resources for each SRS, and the concurrent transmission of multiple SRS is inevitable.

[0085] In the existing 5G New Radio (NR) wireless communication system using orthogonal frequency division multiplexing (OFDM) modulation, the Rel-16 / Rel-17 NR SRS of each cell is obtained by dividing a given SRS frequency band of N consecutive subcarriers into K TC Comb to construct, by having The common cyclic repeating ZC sequence with equidistant phase rotation generates multiple The modulation sequence is then mapped to the subcarriers of each comb, where the i-th The modulation sequence is given by the following equation:

[0086]

[0087] in, a r (u) is a cyclically repeated ZC sequence, the root index r of which is defined in this specification, and the length is N / K TC is the maximum prime number not greater than the number of subcarriers per comb.

[0088] This construction leads to TC The number of cells generated on each comb The SRS has a length of When these When multiple SRSs are sent concurrently by the same or different UEs in the same cell with appropriate TA adjustment, conventional matched filtering-based channel estimation can be used, using an appropriate window with a length not greater than the length of ZCZ, to avoid intra-cell SRS interference between them, provided that the maximum channel delay L experienced by these SRSs is max No greater than the selected window length. However, Rel-16 / Rel-17SRS can support up to orthogonal transmission of concurrent SRS. When there is E> In order to avoid SRS interference in the cell, these UEs need to be divided into groups and multiplex these in TDM mode SRS, that is, the same SRS is sent by different UEs, or the same UE is sent from different antenna ports on different OFDM symbols. This means that the longer the SRS period, the more serious the channel aging problem. In addition, since the SRS time-frequency resource allocation between adjacent cells is the same, cross-cell SRS interference is inevitable.

[0089] The problem of cross-cell SRS interference is more serious in the scenario of coherent joint transmission (CJT) between multiple BSs / TRPs, where the cooperative TRP may need to estimate the channel of the UE in the adjacent cell by receiving the SRS sent by the UE far away from it, while being strongly interfered by the SRS sent by other UEs near it. Therefore, the resulting channel estimation error may be very large, thereby reducing the CJT performance. In order to solve the serious interference problem of CJT, one possible method is to make the adjacent cells coordinate their SRS resource allocation, that is, to jointly perform orthogonal SRS resource allocation for the UE. However, in this case, the available orthogonal SRS resources of each cell will be reduced, which may result in a longer SRS period for TDM-based transmission between UEs in a cell, resulting in more serious channel aging problems. Therefore, a new SRS design method with enhanced SRS capacity is needed to efficiently handle the channel aging problem and intra-cell / inter-cell cross-SRS interference problems.

[0090] The embodiment of the present invention discloses a scheme that can increase the reference signal capacity in a communication system by Q times on the same time-frequency resources, while being superior to the prior art in terms of channel estimation performance. The embodiment of the present invention has two purposes: to alleviate the channel aging problem by enabling each cell to concurrently transmit more reference signals to achieve a shorter reference signal transmission period, and to solve the cross-interference problem between cells by enabling each cell to concurrently transmit the same number of reference signals as Rel-16 / Re1-17 SRS on fewer time-frequency resources, thereby making the time-frequency resource allocation of reference signals between adjacent cells orthogonal to each other without increasing the reference signal transmission period of each cell.

[0091] Figure 1 FIG. 1 shows a first communication device 100 according to an embodiment of the present invention. Figure 1In the illustrated embodiment, the first communication device 100 includes a processor 102, a transceiver 104, and a memory 106. The processor 102 is coupled to the transceiver 104 and the memory 106 via a communication component 108 known in the art. The first communication device 100 can be used for wireless and / or wired communication in a communication system. Wireless communication capabilities can be provided by an antenna or antenna array 110 coupled to the transceiver 104, and wired communication capabilities can be provided by, for example, a wired communication interface 112 coupled to the transceiver 104. The processor 102 can be referred to as one or more general-purpose central processing units (CPUs), one or more digital signal processors (DSPs), one or more application-specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more programmable logic devices, one or more discrete gates, one or more transistor logic devices, one or more discrete hardware components, or one or more chipsets. The memory 106 can be a read-only memory, a random access memory (RAM), or a non-volatile RAM (NVRAM). The transceiver 304 may be a transceiver circuit, a power controller, or an interface that provides the ability to communicate with other communication modules or communication devices (e.g., network nodes and network servers). The transceiver 104, the memory 106, and / or the processor 102 may be implemented in a separate chipset or in a common chipset. In the present invention, the first communication device 100 is used to perform certain actions, which may be understood to mean that the first communication device 100 includes a suitable component for performing the action, such as the processor 102 and the transceiver 104.

[0092] According to an embodiment of the present invention, the first communication device 100 is used to obtain a reference signal 510. The reference signal 510 is based on a modulation sequence in a set of QA modulation sequences of length L≥1, the set of QA modulation sequences includes Q modulation sequence subsets, Q≥1, each modulation sequence subset includes A modulation sequences, A≥1, wherein the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset meets the first correlation standard; the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets meets the second correlation standard; the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset is lower than the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets. The first communication device 100 is also used to send the reference signal 510. Specifically, the reference signal can be obtained by mapping the modulation sequence to a set of L subcarriers in a given frequency band with N≥L continuous subcarriers to obtain N sets of Fourier coefficients. The acquired Fourier coefficient set can be converted to the time domain by inverse DFT (IDFT) to generate a time domain reference signal. In addition, when the first communication device 100 has multiple antennas and / or antenna ports to support concurrent transmission of multiple reference signals, the first communication device 100 can be used to acquire multiple reference signals based on multiple modulation sequences in the set of QA modulation sequences.

[0093] Figure 2 It is shown that the first communication device 100 (for example, Figure 1 2 . The method 200 includes acquiring 202 a reference signal 510, wherein the reference signal 510 is based on a modulation sequence in a set of QA modulation sequences of length L≥1, the set of QA modulation sequences including Q modulation sequence subsets, Q≥1, each modulation sequence subset including A modulation sequences, A≥1, wherein the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset meets a first correlation criterion; the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets meets a second correlation criterion; the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset is lower than the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets. The method 200 includes sending 204 the reference signal 510.

[0094] Figure 3 FIG. 3 shows a second communication device 300 according to an embodiment of the present invention. Figure 3In the illustrated embodiment, the second communication device 300 includes a processor 302, a transceiver 304, and a memory 306. The processor 302 is coupled to the transceiver 304 and the memory 306 via a communication component 308 known in the art. The second communication device 300 also includes an antenna or antenna array 310 coupled to the transceiver 304, meaning that the second communication device 300 is used for wireless communication in a communication system. The processor 302 may be referred to as one or more general-purpose CPUs, one or more DSPs, one or more ASICs, one or more FPGAs, one or more programmable logic devices, one or more discrete gates, one or more transistor logic devices, one or more discrete hardware components, or one or more chipsets. The memory 306 may be a read-only memory, a RAM, or an NVRAM. The transceiver 104 may be a transceiver circuit, a power controller, or an interface that provides the ability to communicate with other communication modules or communication devices. The transceiver 304, the memory 306, and / or the processor 302 may be implemented in a separate chipset or in a common chipset. In the present invention, the second communication device 300 being used to perform certain actions may be understood to mean that the second communication device 300 includes appropriate components for performing the actions, for example, the processor 302 and the transceiver 304 .

[0095] According to an embodiment of the present invention, the second communication device 300 is used to receive a reference signal 510. The second communication device 300 is also used to obtain a modulation sequence from a set of QA modulation sequences of length L≥1, wherein the set of QA modulation sequences includes Q modulation sequence subsets, Q≥1, each modulation sequence subset includes A modulation sequences, A≥1, wherein the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset meets the first correlation standard; the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets meets the second correlation standard; the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset is lower than the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets. The second communication device 300 is also used to estimate the wireless channel 530 based on the received reference signal 510 and the modulation sequence.

[0096] Figure 4 It is shown that the second communication device 300 (for example, Figure 34. The method 400 includes receiving 402 a reference signal 510. The method 400 also includes obtaining 404 a modulation sequence from a set of QA modulation sequences of length L≥1, wherein the set of QA modulation sequences includes Q modulation sequence subsets, Q≥1, each modulation sequence subset includes A modulation sequences, A≥1, wherein the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset meets the first correlation criterion; the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets meets the second correlation criterion; the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset is lower than the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets. The method 400 also includes estimating 406 a wireless channel 530 based on the received reference signal 510 and the modulation sequence.

[0097] Figure 5 A communication system 500 according to an embodiment of the present invention is shown. The communication system 500 in the disclosed example includes a first communication device 100 and a second communication device 300 for communicating and operating in the communication system 500. For simplicity, the communication system 500 shown includes only one first communication device 100 and one second communication device 300. However, the communication system 500 may include any number of first communication devices 100 and any number of second communication devices 300 without departing from the scope of the present invention.

[0098] In a non-limiting example, the first communication device 100 can be used or configured as a client device to communicate with a second communication device 300 used or configured as a network access node. The network access node can be part of a radio access network (RAN), which is connected to the network through a suitable communication interface. The network can be a core network that can be connected to an external network of the same or other communication system. In these examples, the first communication device 100 sends a reference signal 510 to the second communication device 300 in the UL. However, it is worth noting that the opposite order is also possible, that is, the second communication device 300 is used as a client device and the first communication device 100 is used as a network access node. The first communication device 100 can also be represented as a transmitter device or a transmitter. Accordingly, the second communication device 300 can be represented as a receiver device or a receiver.

[0099] Generally speaking, the first communication device 100 can be used to perform the following steps:

[0100] Step 1: Determine frequency resources for all reference signals in the reference signal set

[0101] Step 2: Generate Q modulation sequence subsets, each modulation sequence subset contains A modulation sequences;

[0102] Step 3: Map the modulation sequence to frequency resources to obtain the Fourier coefficients;

[0103] Step 4: Convert the Fourier coefficients into a time domain reference signal through IDFT to obtain a reference signal set.

[0104] Steps 1 to 4 may be performed in any suitable order, for example, step 2 may be performed before step 1 or in parallel with step 1. In the following disclosure, other embodiments of the present invention are presented with reference to steps 1 to 4. These embodiments are set in the context of 3GPP 5G to better understand the present invention. Therefore, implementation examples are described and presented using terminology, expressions, and system architecture according to the 3GPP 5G NR system. In the disclosed example, the first communication device is represented as a UE, and the second communication device 300 is represented as a TRP, a BS, or a gNB. In addition, the reference signal is presented herein as an SRS sent by the UE in the UL. However, the embodiments of the present invention are not limited to this.

[0105] Frequency resources

[0106] In an embodiment of the present invention, the first communication device 100 is used to send a reference signal 510 on a set of L subcarriers out of N consecutive subcarriers, N≥L, wherein the N consecutive subcarriers are divided into t subbands including an equal number of consecutive subcarriers; the set of L subcarriers includes A subcarriers from each subband, and the positions of the A subcarriers in each subband are the same for all t subbands.

[0107] In NR, the SRS band consists of N subcarriers with frequencies f = {f0,…,f N-1}, the uniform spacing between adjacent frequencies is Δf. Without loss of generality, we can assume f0 = 0 and Δf = 1, so we denote the fully available frequency resources as f = {0, 1, ..., N-1}, that is, we refer to the subcarrier frequencies by the corresponding subcarrier index.

[0108] We assume that N = δt, where δ and t are positive integers, and divide the N subcarriers into t interleaved subbands of δ consecutive subcarriers. Then, we can further divide each interleaved subband into Orthogonal generalized physical resource blocks (gPRBs), each gPRB contains A (A≤δ) subcarriers, where: is the largest integer less than or equal to x.

[0109] The mth (m=0,1,…,K TC -1) The index of A subcarriers in gPRB is represented by {j m,l |l=0,1,…,A-1}, satisfying 0≤j m,0 <j m,1 <… <j m,A-1 ≤δ-1, can be arbitrarily distributed in the interleaved subbands, but is the same for all t interleaved subbands. For a set of all t such gPRBs, each gPRB is selected from an interleaved subband to form an interleave, which is mathematically described as the set of used L=At, i.e., the allowed subcarrier frequencies Defined as:

[0110]

[0111] For example, when N = 32, δ = 8, t = A = 4, Figure 6 a shows an exemplary frequency resource allocation, where {j m,l}={0,1,3,6}.

[0112] The waveform whose spectrum is defined as Equation (2) can be classified as a generalized version of the block-interleaved frequency-division multiple access (B-IFDMA) waveform. The B-IFDMA waveform, which constructs the frequency resources of the OFDM waveform, is a baseband analog signal with a comb-shaped spectrum, with non-zero DFT coefficients only at discrete frequencies within a certain number of equidistant and identically uniformly spaced subcarrier blocks. In general, we can construct K in a given SRS frequency band. TC orthogonal interleavings that satisfy:

[0113]

[0114] In one embodiment of the present invention, the parameter A may be set as a factor of δ such that The subcarriers in each gPRB can be selected to have the same starting position in each interleaved subband. TC subcarriers, namely:

[0115] j m,l =j m,0 +K TCl,l=0,1,…,A-1 (4)

[0116] In this case, the common frequency resources of the SRS set are reduced to a comb structure as in Rel-16 / Rel-17 SRS. Figure 6 b shows an exemplary frequency resource allocation, where N=32, δ=8, and t=A=4.

[0117] Modulation sequence

[0118] In the embodiment of the present invention, QA modulation sequences {c q,n Each modulation sequence in {u)|q=0,1,…,Q-1,n=0,1,…,A-1,u=0,1,…,L-1} is a constant envelope sequence of length L=At, constructed as:

[0119]

[0120] in,

[0121] b q,n (l), l = 0, 1, ..., A-1 is the nth (n = 0, 1, ..., A-1) constant envelope sequence of length A in the ath (q = 0, 1, ..., Q-1)th orthogonal subset. We can call such a sequence the first sequence or "short" sequence. All A short sequences in the qth orthogonal subset are mutually orthogonal.

[0122] · l=0,1,…,B-1 is a constant envelope sequence, which is common to all SRSs in the same qth (q=0,1,…,Q-1) subset and different for different SRS subsets. The length B of the constant envelope sequence is an integer, which is a multiple of the number A of SRSs in each subset and a factor of the length L of the modulation sequence, that is:

[0123] B∈{B′|A <B′<L, B′ mod A=0, L mod B′=0} (6)

[0124] We can call such a sequence the secondary sequence or the "intermediate" sequence.

[0125] a(u) is an arbitrary constant envelope sequence of length L = At. We can call such a sequence a third sequence or a "long" sequence.

[0126] Therefore, according to an embodiment of the present invention, at least one modulation sequence in a set of QA modulation sequences is based on a first sequence in a first sequence set with a length of A, a second sequence in a second sequence set with a length of B≥1, and a third sequence with a length of L. The first sequence set includes Q first sequence subsets, wherein each first sequence subset includes A constant envelope sequences, and all A constant envelope sequences are mutually orthogonal. The second sequence set includes Q constant envelope sequences, wherein the correlation between any two second sequences in the Q constant envelope sequences meets a third correlation criterion. The third sequence is a constant envelope sequence. The modulation sequences in the set of QA modulation sequences are based on the periodic repetition of the first sequence, the element-by-element multiplication of the periodic repetition of the second sequence and the third sequence. For example, when L=8, A=2 and B=4, the modulation sequence (c(0), c(1),…, c(7)) can be a first sequence (b(0), b(1)) with a length of A=2, a second sequence (b(0), b(1)) with a length of B=4

[0127] Example construction of the first sequence (short sequence): The qth (q=0,1,…,Q-1)th subset {b q,n (l)} are mutually orthogonal to ensure that all A SRSs in the same subset have the ZCZ property. These first sequences can be selected as a set of all columns of an A×A orthogonal matrix, which can be a DFT matrix, a Hadamard matrix, a matrix with columns of all different cyclic shift versions of a CAZAC sequence of length A (for example, a ZC sequence with a certain root index when A is a prime number), or an mCAZAC sequence of length A. If a CAZAC sequence of length L=At remains a CAZAC sequence after element-wise multiplication (i.e., modulation) with a t-times periodic extended version of an arbitrary constant envelope short sequence of length A, it is called an mCAZAC sequence. The orthogonal matrices of different subsets can be the same or different (for example, one can be a DFT matrix and the other can be a Hadamard matrix), or can be constructed based on different CAZAC / mCAZAC sequences. In the case where the first sequence is selected as the set of all columns of the A×ADFT matrix, the first sequence is the same as the equidistant phase rotation used in the Rel-16 / Rel-17 SRS. The A×A orthogonal matrix obtained by any of the above methods can also be multiplied by any constant phase factor, or element-by-element multiplied with a constant envelope cover sequence of length A, where the constant envelope cover sequence can be any constant envelope sequence of length A, where the constant phase factors / cover sequences of different orthogonal subsets can be the same or different.

[0128] In other words, the first sequence in each first sequence subset is a column of an A×A constant envelope orthogonal matrix, and can also be multiplied by a cover sequence based on the column of the A×A constant envelope orthogonal matrix. The A×A constant envelope orthogonal matrix is ​​any of the following: an A×ADFT matrix, an A×A Hadamard matrix, an A×A matrix whose columns are different cyclic shift versions of a CAZAC sequence with a length of A and including a ZC sequence, or an A×A matrix whose columns are different cyclic shift versions of an mCAZAC sequence with a length of A. The cover sequence is a constant envelope sequence with a length of A, which is the same for all first sequences in each first sequence subset, and can be the same or different for different first sequence subsets.

[0129] Example construction of the second sequence (middle sequence): Second sequence requiring different subsets (q=0,1,…,Q-1) are different and have low periodic cross-correlation with each other, that is, the third correlation criterion is satisfied to ensure that any two SRS generated from different subsets have low and sparse cross-correlation. Since there is a low but non-zero periodic cross-correlation between the two second sequences of different subsets, their corresponding modulation sequences (and the resulting SRS) are usually non-orthogonal to each other. As shown below, the length B of the second sequence controls the sparseness of the cross-correlation between two SRSs from different subsets, and its periodic cross-correlation function is only in all N delay offset positions. The percentage is non-zero, otherwise it cannot be achieved if the second sequence is removed from the modulation sequence design. The second sequence of a subset can be set to a full "1" sequence of length B, and the second sequences of other Q-1 subsets can be set to different CAZAC or mCAZAC sequences of length B, or periodic extensions of different CAZAC / mCAZAC sequences with a length less than B, or truncation of different CAZAC / mCAZAC sequences with a length greater than B. In one example, the second sequence can be set to a (periodically extended / truncated) ZC sequence with different root indices. The second sequence obtained by any of the above methods can also be multiplied by a constant phase factor (the constant phase factor can be the same or different for different subsets), and / or multiplied element by element with a common and arbitrary constant envelope cover sequence of length B. Due to the low periodic cross-correlation characteristics of different CAZAC / mCAZAC sequences (for example, ZC sequences with different root indices), the Q second sequences constructed by any of the above methods can ensure that their periodic cross-correlation functions have low correlation under any cyclic delay offset. In addition, selecting different (periodically extended / truncated) CAZAC / mCAZAC sequences for the second sequence may result in different PAPRs of the obtained SRS. Therefore, the second sequence can be optimized to achieve a low PAPR for the obtained SRS, for example, by selecting the second sequence as a (periodically extended / truncated) ZC sequence with an optimized root index, so that an SRS with a low PAPR can be obtained.

[0130] Therefore, in summary, the second sequence is common to all modulation sequences in the same modulation sequence subset and is different for modulation sequences in different modulation sequence subsets. The length B of the second sequence is an integer, which is a multiple of A and a factor of L; the second sequence is any of the following: an all-"1" sequence of length B, a CAZAC / mCAZAC sequence of length B, a CAZAC / mCAZAC sequence of length less than B and periodically extended to length B, or a CAZAC / mCAZAC sequence of length greater than B and truncated to length B. The third correlation criterion definition: the cross-correlation of all cyclic shift versions of a second sequence in the second sequence set and another sequence in the second sequence set is lower than a predetermined threshold.

[0131] Example construction of the third sequence (long sequence): The third sequence a(u) can be set to a CAZAC or mCAZAC sequence of length L, or a periodic extension of a CAZAC / mCAZAC sequence of length less than L, or a truncation of a CAZAC / mCAZAC sequence of length greater than L. In one example, the third sequence can be set to a (periodically extended / truncated) ZC sequence with a certain root index, and different third sequences can be obtained from different (periodically extended / truncated) ZC sequences with different root indices to generate an additional SRS set, which can be used in different cells of a cellular communication system, for example. The third sequence is any of the following: a CAZAC / mCAZAC sequence of length L, a CAZAC / mCAZAC sequence of length less than L and periodically extended to length L, or a CAZAC / mCAZAC sequence of length greater than L and truncated to length L.

[0132] In an embodiment of modulation sequence generation, the first sequence in a subset is selected as all columns of an A×ADFT matrix, where The second sequence in the subset is selected as a sequence of all "1"s of length B, and the third sequence is selected as a ZC sequence that is a periodic extension of a root defined in the standard for Rel-16 / Rel-17 NR SRS. In this case, when selecting a common frequency resource To form a comb, among these Rel-16 / Rel-17 NR SRS, the generated The SRSs are exactly the same. Therefore, the QA reference signal set contains the existing Rel-16 / Rel-17 NR SRS in one of its subsets and is therefore compatible with the existing Rel-16 / Rel-17 NR SRS. In this case, a second sequence in the other Q-1 subsets can be selected from the candidate (periodic extended / truncated) CAZAC / mCAZAC sequences, especially the (periodic extended / truncated) ZC sequences with different root indices, so that an SRS with a low PAPR can be obtained.

[0133] In an embodiment of modulation sequence generation, the length of the second sequence is selected as the largest integer in the set defined by equation (6). In this case, the periodic cross-correlation function of two reference signals based on two modulation sequences in different subsets can be kept sparse while having a low correlation value within the LCZ.

[0134] In an embodiment of the modulation sequence generation, the length of the second sequence is selected as the smallest integer in the set defined by equation (6) that is not less than a predetermined threshold. In this case, the amplitude of the periodic cross-correlation function of the two reference signals based on the two modulation sequences in different subsets can be kept at a satisfactorily low value, while the number of non-zero correlation values ​​within the LCZ is the sparsest, which results in a lower computational complexity in the corresponding CS-based channel estimation at the receiver.

[0135] Fourier coefficients

[0136] Get a sequence of N Fourier coefficients based on the following equation:

[0137]

[0138] Due to the existence of K TC non-intersecting intersection We can use the same set of modulation sequences {c q,n (u)} construct up to K TC Since different interlaces are mutually orthogonal by definition, any two SRSs from different interlaces have zero periodic cross-correlation and can therefore be sent in parallel in the same cell without introducing interference to each other.

[0139] Time Domain SRS

[0140] Time Domain SRS m,q,n (k)} through its corresponding Fourier coefficient {S m,q,n (f)}, we get:

[0141]

[0142] q=0,1,…,Q-1,n=0,1,…,A-1,k=0,1,…,N-1

[0143] The scaling constant is Ensure the sequence m,q,n (f)} and the corresponding SRS {s m,q,n (k)} have the same energy E=L.

[0144] In one embodiment of the present invention, the time domain SRS {s m,q,n (k)} is cyclically shifted, which is equivalent to the Fourier coefficients {S m,q,n(f)} performs linear phase rotation, and then generates time domain SRS through IDFT using step 4. In this case, the cyclic shift values ​​of the SRS in the same subset should be the same to maintain the ZCZ characteristics between the SRS, and the cyclic shift values ​​of the SRS from different subsets can be different. The advantage of this additional cyclic shift operation is that the delay offset position, i.e., the cyclic shift, of the non-zero periodic cross-correlation values ​​of two SRSs from different subsets can be changed. When the two SRSs are transmitted concurrently through their respective multipath channels, the estimate of one channel path of the target SRS may just receive the interference generated by the interfering SRS through a certain channel path. Through this additional cyclic shift operation, the interference of the interfering SRS can be shifted to another delay offset position, so that the channel path of the target SRS can be accurately estimated.

[0145] Alternative Implementation

[0146] When the SRS capacity growth factor Q is a factor of the length B of the intermediate sequence, an equivalent implementation of equation (5) is to re-index all QA modulation sequences and construct them as:

[0147]

[0148] in,

[0149] b′ n (l) is a sequence of length QA, which is obtained by a constant envelope sequence of length A. With a constant envelope sequence ξ of length Q n mod Q The Kronecker product of (l) is obtained, namely:

[0150]

[0151] Here all QA sequences of length A {b q,n (l)},q=0,1,…,Q-1,n=0,1,…,A-1 can be obtained by

[0152] (5) is constructed in the same way as the first sequence. All Q sequences ξ of length Q q (l), q=0,1,…,Q-1 can all be any constant envelope sequence, which can be the same or different.

[0153] · is a constant envelope sequence of length B, which is different for different q (q=0, 1, ..., Q-1) and can be constructed in the same way as the second sequence in equation (5).

[0154] a(u) is a constant envelope sequence of length L, which can be constructed in the same way as the third sequence in equation (5).

[0155] The equivalence between the modulation sequence constructions of equations (5) and (9) can be obtained by substituting equation (10) into equation (9) and defining To prove, we get:

[0156]

[0157] This is the same as equation (5).

[0158] exist In an example of a modulation sequence when q,n (I) and ξ q (I) Be selected as:

[0159]

[0160] The third sequence is selected to be the same as the periodically extended ZC sequence used for Rel-16 / Rel-17 NR SRS, i.e., a(u)=a in equation (1). r (u). Then, we can get:

[0161]

[0162] Equation (9) can be expressed as:

[0163]

[0164] That is, the modulation sequence disclosed in the present invention can be based on Rel-16 / Rel-17 NR SRS by first rotating the equidistant phase The number of is increased by Q times, and then combined with the mask sequence (the sequence is the second sequence in the set of Q second sequences with a length of B) It is generated by element-wise multiplication of a periodic extended version of .

[0165] Characteristics of the proposed reference signal

[0166] In this subsection, the periodic auto / cross-correlation properties of the proposed reference signals are demonstrated.

[0167] Periodic autocorrelation: From SRS{s m,q,n (k)} Starting from the frequency domain definition of the periodic autocorrelation function, we obtain:

[0168]

[0169] From equation (15), we can conclude that the periodic autocorrelation function of each SRS has a length of at least DzAZ =ZAZ of t-1.

[0170] Periodic cross-correlation: For m,q,n (k) and s m,q,n′ For any two SRS of (k), we obtain:

[0171]

[0172] In addition, due to {b q,n (l)} and {b q,n′ (l)} is the first sequence in the same orthogonal subset, i.e. We get:

[0173]

[0174] Therefore, there exists a length Q ZCCZ =t-1 zero cross-correlation zone (ZCCZ). Combining this with equation (15), we can conclude that the SRS from the same subset has a length of D ZCZ = ZCZ of t-1. A first correlation criterion defines that a reference signal based on a modulation sequence in a subset of modulation sequences is orthogonal to consecutive cyclically shifted versions of another reference signal based on another modulation sequence in the same subset of modulation sequences.

[0175] For different subsets s m，q，n (k) and s m，q′，n′ For any two SRS of (k), by defining Z = B / A, we obtain:

[0176]

[0177] Therefore, the periodic cross-correlation between two SRSs from different subsets is only The percentages are sparse and non-zero. These non-zero correlation values ​​depend on the frequency resource allocation of the modulation sequence. Detailed selection and selection of the first and second sequences.

[0178] In one implementation example, frequency resource allocation is chosen as the comb in equation (4), and the first sequence is chosen as the column of the A×ADFT matrix, i.e. Then, the first two sums in equation (18) can be written as:

[0179]

[0180] It is the intermediate sequence and The oversampling period cross-correlation of and When all are selected as different CAZAC / mCAZAC sequences, for example, ZC sequences with different root indices, the amplitude of the periodic cross-correlation function of these sequences can be approximately Furthermore, the third sum in equation (18) can be written as:

[0181]

[0182] Therefore, the amplitude of the periodic cross-correlation function of two SRSs in different subsets can be approximately written as:

[0183]

[0184] Since when B is large enough, it is considered that the value is low, so the two SRSs generated based on any two modulation sequences from different modulation sequence subsets have low cross-correlation with each other under all cyclic shift delay offsets. Combined with the fact that all A SRSs generated based on all A modulation sequences in each of the Q modulation sequence subsets have a ZCZ of length t, we can conclude that all QA SRSs generated based on the disclosed idea have a LCZ of length t. The second correlation criterion is defined as follows: The cross-correlation of a reference signal based on a modulation sequence in a modulation sequence subset with a plurality of consecutive cyclic shift versions of another reference signal based on another modulation sequence in a different modulation sequence subset is lower than a predetermined threshold.

[0185] Signaling

[0186] Figure 7 FIG. 1 shows some signaling aspects of an embodiment of the present invention. Figure 7 In step I, the second communication device 300 sends a control signal 520 to the first communication device 100. Figure 7 In step II, the first communication device 100 derives the information in the control signal 520. Based on the information in the control signal 520, Figure 7 In step III, the first communication device 100 generates one or more reference signals based on one or more modulation sequences. In step IV, the first communication device 100 sends one or more reference signals to the second communication device 300. Figure 7 In step V, the second communication device 300 receives one or more reference signals. Figure 7In step VI, the second communication device 300 estimates the wireless channel between the first communication device 100 and the second communication device 300 based on the received one or more reference signals and the one or more modulation sequences obtained / generated locally. Therefore, before the first communication device 100 sends the SRS in the UL in NR, the first communication device 100 needs to determine the configuration of the SRS to be sent based on the control signal 520, which can be received in the high-layer signaling. The configuration of the SRS may include the SRS time-frequency resources of each SRS antenna port, such as the starting position in the time domain, the number of consecutive OFDM symbols in each SRS period, the starting position in the frequency domain, the SRS bandwidth and the number of combs, etc. The SRS time-frequency resources may be indicated in the same manner as in 3GPP NR (e.g., by SRS resource configuration signaling), and the identification of the SRS sequence may be indicated in different manners as described in detail below. It should be noted that the values ​​of δ, A and t can be derived from the SRS time-frequency resource configuration, so even if they can be indicated, they do not need to be indicated separately.

[0187] In one embodiment of the present invention, when the first communication device 100 needs to send SRS from multiple SRS antenna ports on the same time-frequency resources, all or part of these SRSs are selected from the same orthogonal SRS subset on the same interlace and indicated to the first communication device 100.

[0188] In one embodiment of the present invention, when the first communication device 100 needs to send SRS from multiple SRS antenna ports on the same time-frequency resources, all or part of these SRS are selected to have a modulation sequence constructed based on the first sequence in the same orthogonal first sequence subset and the same second sequence and third sequence, mapped to different interleavings, and then indicated to the first communication device 100.

[0189] In one embodiment of the present invention, the value of Q, i.e., the number of modulation sequence subsets in the set of modulation sequences, is a constant pre-defined in the standard and therefore does not need to be indicated. However, in another embodiment of the present invention, the value of Q is configurable and can be selected from a plurality of N pre-defined in the standard. Q The value {Q0,Q1,…,Q NQ -1}, and its detailed value is obtained through The bit string indicates to the UE. Therefore, the value of Q is predefined, or the first communication device 100 is used to receive a control signal 520 indicating the value of Q.

[0190] The first communication device 100 may also be configured to receive a control signal 520 indicating an identification of a modulation sequence.

[0191] In one embodiment of the present invention, the identification of the modulation sequence includes A single bit string indicates N bits, where N group is the number of reference signal groups defined in the communication system (500). In NR, the SRS sequence identifier By including A single bit string of bits is indicated to the UE, where N group is the number of SRS groups defined in the system (ie, a group of cells), Q is the number of orthogonal SRS subsets in each SRS group, and A is the number of orthogonal SRSs in each orthogonal SRS subset.

[0192] In one embodiment of the present invention, the modulation sequence is identified by the lengths of and The first bit string indicates the reference signal group index, and the second bit string indicates the index of the modulation sequence in the set of modulation sequences associated with the reference signal group index. The lengths are and The first bit string is used to indicate the number of SRS groups, and the second bit string is used to indicate the index of the SRS sequence in each SRS group.

[0193] In one embodiment of the present invention, the modulation sequence is identified by the lengths of and The first bit string indicates the reference signal group index, the second bit string indicates the index of the modulation sequence subset in the set of modulation sequences associated with the reference signal group index, and the third bit string indicates the index of the modulation sequence in the modulation sequence subset. The three lengths are and The bit string indicates, wherein the first bit string is used to indicate the SRS group index, the second bit string is used to indicate the index of the orthogonal SRS subset within each SRS group, and the third bit string is used to indicate the index of the SRS within each orthogonal SRS subset.

[0194] In one embodiment of the present invention, the length B of the second sequence is a constant predefined and specified in the standard, or can be derived from the SRS time-frequency resource configuration, and therefore does not need to be indicated separately. For example, the length B of the second sequence is the largest integer in the set defined in equation (6), or the smallest integer in the set defined in equation (6) that is greater than a predetermined threshold, and therefore can be derived from L and A. In one embodiment, the length B of the second sequence is a constant of length The bit string indicates that |SB | is the number of elements in the set defined in equation (6), or is the number of elements in a predefined subset of the set defined in equation (6). Therefore, the length B of the second sequence is predefined, or the first communication device 100 is used to receive a control signal 520 indicating the length B of the second sequence. The length B of the second sequence can be determined by a length of The bit string indicates that N B is the number of integers in the set of integers that are multiples of A and factors of L; or is the number of integers in a predefined subset of the set of integers that are multiples of A and factors of L.

[0195] Channel Estimation

[0196] The periodic autocorrelation / cross-correlation properties introduced in the previous section enable CS-based channel estimation of the proposed SRSs when they are transmitted concurrently from the same or different first communication devices with appropriate TA adjustment, as described below.

[0197] When all QA SRSs constructed based on the disclosed method are sent concurrently from the same or different first communication devices through appropriate TA adjustment, the second communication device 300 allocates frequency resources. The signal received on each subcarrier can be expressed as:

[0198]

[0199] Among them, H q,n (f) SRSs m,q,n (k) is the frequency domain channel coefficient experienced by the f-th subcarrier, z(f) is the corresponding noise term, and h q,n (l),l=0,1,…,L max -1 for SRSs m,q,n (k) The time domain channel coefficient of the channel path experienced when the time delay is l. By allocating frequency resources The signals received on all L subcarriers are collected into a vector, namely:

[0200] Y=(Y(j m,0 ) Y(j m,1 ) … Y(j m,A-1 ) Y(δ+j m,0 ) … Y((t-1)δ+j m,A-1 )) T (twenty three)

[0201] We rewrite equation (22) into the following matrix form:

[0202] Y=Wh+Z (24)

[0203] Where Z is the corresponding noise vector, h q,n =(h q,n (0)h q,n (1)…h q,n (L max -1)) T For m,q,n (k) The length of the channel traversed is L max The channel impulse response (CIR) of W = (W 0,0 W 0,1 … W 0,A-1 W 1,0 … W Q-1,A-1 ) is L×QAL max Matrix, whose L×L max Sub-matrix W q,n Each submatrix in is composed of the SRS sequence {s m,q,n (k)} is determined. The detailed derivation of equation (24) is given in the Appendix. q,n,l Represents the submatrix W q,n The lth (l=0,1,…,L max -1) columns. As described in the Appendix, the normalized correlation between any two columns W satisfies:

[0204]

[0205] The premise is that the maximum delay of the channel experienced by all SRS satisfies L max ≤t.

[0206] Equation (25) means that as long as the value of B is large, the correlation between the columns of W is low. In addition, since the length is AQL max The vector h of QA (i.e., the concatenation of the CIRs experienced by all QA SRSs) is usually sparse and contains a smaller number of non-zero entries than the vector length QAL max is much less, so estimating the sparse CIR from Eq. (24) can be regarded as a CS problem and solved using a suitable CS-based algorithm, e.g., orthogonal matching pursuit (OMP).

[0207] In addition, it can be seen from equation (25) that only when the corresponding two SRSs come from different subsets and When the two columns w q,n,l and w q′,n′,l′ This means that the matrix W can be viewed as The CS-based channel estimation problem in equation (24) can be decomposed into L / B smaller CS problems and solved in parallel, thereby reducing the computational complexity.

[0208] In summary, the disclosed QO SRS scheme can increase the SRS capacity by Q times at the cost of introducing intra-cell interference between SRSs transmitted in the same cell, which is similar to the conventional scheme. However, the conventional scheme does not have corresponding processing at the receiver to solve this intra-cell interference problem. In contrast, the disclosed QO SRS scheme can control the interference between SRSs from different subsets at a low level, so that CS-based channel estimation can be applied at the receiver to separate the intra-cell interference between SRSs. Therefore, compared with the conventional scheme, better channel estimation performance can be expected in subsequent DL data transmission, and thus better block error rate (BLER) / throughput performance, as shown in the next section.

[0209] Performance Evaluation

[0210] The performance of the disclosed QO SRS design is evaluated and compared with traditional solutions in the following system scenarios:

[0211] Consider a single-cell system at 3.5 GHz carrier frequency with a bandwidth of N=2304 consecutive subcarriers and an SCS of 30 kHz.

[0212] The BS is equipped with a uniform rectangular antenna array with 4 rows and 8 columns (i.e., 32 BS antennas), with the spacing between adjacent columns and rows being half a wavelength, and each UE is assumed to have a single antenna.

[0213] The channel between each UE and the BS is generated according to the CDL-C model in 3GPP TS 38.901 V15.0.0 “Channel Model Study for 0.5 GHz to 100 GHz Frequency”, assuming an expected delay spread of 300 ns (corresponding to a CIR length of 180 samples), while considering random angle of arrival / departure (AoA / AoD) rotation and uniform distribution in [-9

[0214] 9] samples. The UE speed is set to 30 km / h and each UE has an arbitrary moving direction in the 2-D plane to model the channel aging on the OFDM symbols.

[0215] Assume that a slot mode of “DDDSU” is used to coordinate UL / DL transmission, where “D”, “U” and “S” represent DL slot, UL slot and special slot respectively, each slot contains 14 consecutive OFDM symbols, and SRS transmission is allowed only in the last OFDM symbol of the “S” slot, i.e., the minimum SRS period is 2.5 ms, corresponding to 5 slots, each of which is 0.5 ms long.

[0216] • Since UL power control compensates for the path loss of different UEs, the SRS power received from different UEs is assumed to be the same at the BS to achieve the same sounding accuracy.

[0217] Simulate DL data transmission of only one target UE, assuming that the UE side has perfect knowledge of the channel, i.e., no scheduling and no interference from data streams of other UEs. The UE uses QPSK modulation and MCS defined by rate R=1 / 2 LDPC code for data transmission on each DL OFDM symbol. Assume that the DL SNR is the same as the UL SNR.

[0218] The disclosed QO SRS and conventional SRS schemes are employed to generate SRS on the same frequency resource allocation in the following manner to make a fair comparison between the two:

[0219] NR SRS (baseline scheme): Considering the maximum channel delay and timing error in the above system settings, we use the frequency resource allocation based on comb 2 and the The Rel-16NR SRS of SRS is used as a reference, and the total generated ZCZ length is

[0220] Therefore, conventional matched filtering and window-based channel estimation are used at the receiver, with a window length equal to

[0221] D=min{D ZCZ ,L max}=198.

[0222] Traditional solution 2: Consider frequency resource allocation based on comb 2 and each comb The Rel-16NR SRS with equidistant phase rotation has a total ZCZ length of Therefore, conventional matched filtering and window-based channel estimation are used at the receiver, with a window length equal to

[0223] Traditional solution 3: By setting δ = 8, t=288, and A=4 subcarriers in each gPRB are allocated to every other subcarrier in each interlaced subband, and the frequency resource allocation is selected to be the same as comb 2. A total of 8Q SRS are generated by generating the modulation sequence as follows: The modulation sequence is generated by element-wise multiplication of a periodically repeated short sequence and a long sequence, where the long sequence is selected to be the same as the periodically extended ZC sequence used for Rel-16 NR SRS, that is, a(u)=a r (u), the short sequences are chosen as the columns of a 4×4 DFT matrix covered by a subset-specific covering sequence of length A=4, i.e. For one subset, the cover sequence is selected as a sequence of all "1"s with a length of 4, and for the other Q-1 subsets, a ZC sequence of length 5 with different root indices and punctured to a length of A = 4 is selected. The A time domain SRSs generated in the qth SRS subset are further cyclically shifted by the same number of samples, so that the total generated QA SRS has a length of Therefore, conventional matched filtering and window-based channel estimation are used at the receiver, with a window length equal to

[0224] QO SRS: By setting t = 288, and A = 4 subcarriers in each gPRB are allocated to every other subcarrier in each interleaved subband. The frequency resource allocation is chosen to be the same as comb 2. A total of 8Q SRS are generated by generating the modulation sequence as follows: We choose the short and long sequences to be the same as the equidistant phase-rotated and periodically extended ZC sequences used for Rel-16 NR SRS, i.e. And for the first subset and the periodically extended ZC sequence whose length is the largest prime number not greater than B, select the full "1" intermediate sequence of length B, and for the other

[0225] Q-1 subsets, with different root indices selected. CS-based channel estimation is adopted at the receiver.

[0226] It should be noted that the SRS generated by all the above SRS schemes can be sent on the part of the frequency band where the channel needs to be estimated, that is, these SRS can be implemented together with the Rel-17 partial SRS in the traditional scheme 1 to achieve better performance than the pure partial SRS scheme. Therefore, this paper does not include the performance of the traditional scheme 1, that is, the Rel-17 partial SRS.

[0227] We consider using different SRS schemes to achieve SRS capacity enhancement of Q = 2 times, 4 times, and 8 times, and assume that there are E = 8Q UEs in the cell. Using the reference Rel-16 SRS, up to 8 concurrent SRSs can be supported in one OFDM symbol, so the SRS period is set to 2.5Qms. All other schemes can support 8Q concurrent SRSs in one OFDM symbol, so they can have an SRS period of 2.5ms. Figures 8a to 8c The periodic autocorrelation / cross-correlation functions of the disclosed QO SRS are shown for different values ​​of Q. It can be seen that the length of the LCZ of all generated QO SRS is t=288. When Q=2, 4, and 8, the magnitudes of the non-zero cross-correlations within the LCZ are approximately 0.06, 0.11, and 0.16, respectively, which are slightly higher than the corresponding expected values. 0.833 and 0.118.

[0228] Figures 9a to 9c The BLER performance achieved by different SRS schemes at different SRS capacity enhancement factors Q is shown. For convenience, we also include the BLER performance achieved by perfect DL CSI (labeled as “Perfect DL CSI”) (where DL precoding is designed based on perfect DL CSI), and the BLER performance achieved by a single Rel-16 NR SRS transmission at a minimum SRS period of 2.5ms (labeled as “Reference E=1, 2.5ms”), where the SRS is only affected by minimal channel aging issues and noise at the receiver and is not interfered by other SRS. Figures 9a to 9c We can see that the disclosed QO SRS scheme outperforms all other SRS schemes, and the performance gain is more significant when the number of SRS capacity enhancement Q is large. This is because the QO SRS scheme, in addition to alleviating the channel aging problem by supporting a short SRS period with SRS capacity enhancement, also effectively solves the inter-SRS interference problem by utilizing the low correlation characteristics of the SRS generated by the channel estimation based on the CS principle, while other SRS schemes still have the inter-SRS interference problem, especially when the number of SRS capacity enhancement Q is large.

[0229] appendix

[0230] Based on equation (22), we can express the received signal vector Y using equation (23):

[0231]

[0232] Among them, W q,n L×L max The matrix whose entry in the (iA+l)th row and l′th column is given by the following equation:

[0233]

[0234] By further defining W = (W 0,0 W 0,1 … W 0,A-1 W 1,0 … W Q-1,A-1 )and We can express (A1) in a more compact form as shown in Equation (24).

[0235] For any two columns of matrix W, for example, the submatrix W q,n , The l1th column and submatrix W q′ , n′ , In the l2th column of , we get:

[0236]

[0237] By substituting the periodic autocorrelation / cross-correlation characteristics of the SRS generated in equations (15) to (21) into equation (A3), we can obtain equation (25).

[0238] The network access node in this article may also be represented as an access point (AP) or BS, for example, a radio BS (RBS), which may be called a transmitter, "gNB", "gNodeB", "eNB", "eNodeB", "NodeB" or "B node" in some networks, depending on the standards, technologies and terminology used. Based on the transmission power and cell size, the network access node may have different categories or types, such as macro eNodeB, home eNodeB or mini base station. The network access node may also be a station (STA), that is, any device including a media access control (MAC) and physical layer (PHY) interface to a wireless medium (WM) that complies with IEEE802.11. The network access node can be used to communicate in the following: 3GPP-related long term evolution (LTE), advanced LTE, fifth generation (5G) wireless systems, such as NR and its evolutions, and IEEE-related Wi-Fi, worldwide interoperability for microwave access (WiMAX) and its evolutions.

[0239] The client device in this article can be represented as a user device, UE, mobile station, Internet of Things (IoT) device, sensor device, wireless terminal and / or mobile terminal, capable of wireless communication in a wireless communication system (sometimes also referred to as a cellular wireless system). UE can be referred to as a mobile phone, cellular phone, tablet computer or laptop computer with wireless capabilities. For example, the UE in this context can be a portable, pocket storage, handheld, computer-based or vehicle-mounted mobile device that can communicate voice and / or data with another communication entity (such as another receiver or server) through RAN. UE can also be STA, which is any device that includes a MAC and PHY interface to WM that complies with IEEE 802.11. UE can be used to communicate in the following: 3GPP-related LTE, Advanced LTE, 5G wireless systems, such as NR and its evolution, and IEEE-related Wi-Fi, WiMAX and its evolution.

[0240] In addition, any method according to an embodiment of the present invention can be implemented in a computer program with a code component, and the code module causes the processing component to perform the steps of the method when the processing component is run. The computer program is included in the computer-readable medium of the computer program product. The computer-readable medium can basically include any memory, for example, the ROM, PROM, EPROM, flash memory, EEPROM or hard disk drive mentioned above.

[0241] In addition, it should be appreciated that the first communication device 100 and the second communication device 300 include necessary communication capabilities in the form of, for example, functions, modules, units, elements, etc., for performing or implementing embodiments of the present invention. Examples of other such components, units, elements and functions are: processors, memories, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selection units, switches, interleavers, deinterleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiving units, transmitting units, DSPs, TCM encoders, TCM decoders, power supply units, power supply feeds, communication interfaces, communication protocols, etc., which are appropriately arranged together to perform the scheme.

[0242] Therefore, the processor of the first communication device 100 and the second communication device 300 may include, for example, one or more instances of a CPU, a processing unit, a processing circuit, a processor, an ASIC, a microprocessor, or other processing logic that can interpret and execute instructions. Therefore, the expression "processor" may refer to a processing circuit including a plurality of processing circuits, for example, any, some or all of the above-mentioned processing circuits. The processing circuit system may also perform data processing functions for inputting, outputting and processing data, including data buffering and device control functions, such as call processing control, user interface control, etc.

[0243] Finally, it should be understood that the present invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

1. A first communication device (100), characterized in that: Used for: Acquire a reference signal (510), wherein the reference signal (510) is based on a modulation sequence in a set of QA modulation sequences of length L≥1, the set of QA modulation sequences includes Q modulation sequence subsets, Q≥1, each modulation sequence subset includes A modulation sequences, A≥1, wherein a correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset satisfies a first correlation criterion; a correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets satisfies a second correlation criterion; the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset is lower than the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets; The reference signal is transmitted (510).

2. The first communication device (100) according to claim 1, characterized in that The first correlation criterion defines that a reference signal based on a modulation sequence in a subset of modulation sequences is orthogonal to consecutive cyclically shifted versions of another reference signal based on another modulation sequence in the same subset of modulation sequences.

3. The first communication device (100) according to claim 1 or 2, characterized in that: The second correlation criterion defines that the cross-correlation between a reference signal based on a modulation sequence in a modulation sequence subset and a plurality of consecutive cyclically shifted versions of another reference signal based on another modulation sequence in a different modulation sequence subset is lower than a predetermined threshold.

4. The first communication device (100) according to any one of the preceding claims, characterized in that: At least one modulation sequence in the set of QA modulation sequences is based on a first sequence in a first sequence set with a length of A, a second sequence in a second sequence set with a length of B≥1, and a third sequence with a length of L, wherein the first sequence set includes Q first sequence subsets, each first sequence subset includes A constant envelope sequences, wherein all A constant envelope sequences are mutually orthogonal; the second sequence set includes Q constant envelope sequences, wherein the correlation between any two second sequences in the Q constant envelope sequences satisfies a third correlation criterion; and the third sequence is a constant envelope sequence.

5. The first communication device (100) according to claim 4, characterized in that The modulation sequences in the set of QA modulation sequences are based on element-by-element multiplication of the periodic repetition of the first sequence, the periodic repetition of the second sequence, and the third sequence.

6. The first communication device (100) according to claim 4 or 5, characterized in that: The first sequence in each first sequence subset is a column of an A×A constant envelope orthogonal matrix, or an element-by-element multiplication of a column of an A×A constant envelope orthogonal matrix and a covering sequence, wherein the A×A constant envelope orthogonal matrix is ​​any one of the following: an A×A discrete Fourier transform DFT matrix, an A×A Hadamard matrix, a column of length A and including a Zadoff-Chronotype matrix. u , an A×A matrix of different cyclic shift versions of a constant amplitude zero autocorrelation CAZAC sequence of a ZC sequence, or an A×A matrix of different cyclic shift versions of a modulated CAZAC (mCAZAC) sequence with a length of A; the covering sequence is a constant envelope sequence with a length of A, which is the same for all the first sequences in each first sequence subset, and can be the same or different for different first sequence subsets.

7. The first communication device (100) according to any one of claims 4 to 6, characterized in that: The second sequence is common to all modulation sequences in the same modulation sequence subset, and is different for modulation sequences in different modulation sequence subsets, wherein the length B of the second sequence is an integer, and the integer is a multiple of A and a factor of L; the second sequence is any one of the following: an all-"1" sequence of length B, a CAZAC / mCAZAC sequence of length B, a CAZAC / mCAZAC sequence of length less than B and periodically extended to length B, or a CAZAC / mCAZAC sequence of length greater than B and truncated to length B.

8. The first communication device (100) according to any one of claims 4 to 7, characterized in that: The length B of the second sequence is predefined; or The first communication device (100) is used to receive a control signal (520) indicating the length B of the second sequence, wherein the length B of the second sequence is a length of The bit string indicates that the operator Returns the smallest integer not less than x, N B is the number of integers in the set of integers that are multiples of A and factors of L; or is the number of integers in a predefined subset of the set of integers that are multiples of A and factors of L.

9. The first communication device (100) according to any one of claims 4 to 8, characterized in that: The third correlation criterion defines that the cross-correlation between all cyclic shifted versions of a second sequence in the second sequence set and another second sequence in the second sequence set is lower than a predetermined threshold.

10. The first communication device (100) according to any one of claims 4 to 9, characterized in that: The third sequence is any one of the following: a CAZAC / mCAZAC sequence with a length of L, a CAZAC / mCAZAC sequence with a length less than L and periodically extended to a length of L, or a CAZAC / mCAZAC sequence with a length greater than L and truncated to a length of L.

11. The first communication device (100) according to any one of the preceding claims, characterized in that: Used for: The reference signal (510) is transmitted by mapping the modulation sequence onto a set of L subcarriers among NNN consecutive subcarriers, N≥L, wherein the N consecutive subcarriers are divided into t subbands including an equal number of consecutive subcarriers; the set of L subcarriers includes A subcarriers from each subband, and positions of the A subcarriers in each subband are the same for all the t subbands.

12. The first communication device (100) according to any one of the preceding claims, characterized in that: The value of Q is predefined; or The first communication device (100) is configured to receive a control signal (520) indicating a value of Q.

13. The first communication device (100) according to any one of the preceding claims, characterized in that: The first communication device (100) is used to receive a control signal (520) indicating an identifier of the modulation sequence, wherein the identifier of the modulation sequence is indicated in the following manner: include A single bit string of bits, where N group is the number of reference signal groups defined in the communication system (500); or The lengths are and wherein the first bit string indicates a reference signal group index, and the second bit string indicates an index of a modulation sequence in a set of modulation sequences associated with the reference signal group index; or The lengths are and The invention provides three bit strings, wherein the first bit string indicates a reference signal group index, the second bit string indicates an index of a modulation sequence subset in a set of modulation sequences associated with the reference signal group index, and the third bit string indicates an index of a modulation sequence in the modulation sequence subset.

14. A second communication device (300), characterized in that: Used for: Receive a reference signal (510): Obtain a modulation sequence from a set of QA modulation sequences of length L≥1, wherein the set of QA modulation sequences includes Q modulation sequence subsets, Q≥1, each modulation sequence subset includes A modulation sequences, A≥1, wherein the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset satisfies a first correlation standard; the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets satisfies a second correlation standard; the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset is lower than the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets; A wireless channel (530) is estimated based on the received reference signal (510) and the modulation sequence.

15. The second communication device (300) according to claim 14, characterized in that: The first correlation criterion defines that a reference signal based on a modulation sequence in a subset of modulation sequences is orthogonal to consecutive cyclically shifted versions of another reference signal based on another modulation sequence in the same subset of modulation sequences.

16. The second communication device (300) according to claim 14 or 15, characterized in that: The second correlation criterion defines that the cross-correlation between a reference signal based on a modulation sequence in a modulation sequence subset and a plurality of consecutive cyclically shifted versions of another reference signal based on another modulation sequence in a different modulation sequence subset is lower than a predetermined threshold.

17. The second communication device (300) according to any one of claims 14 to 16, characterized in that: At least one modulation sequence in the set of QA modulation sequences is based on a first sequence in a first sequence set with a length of A, a second sequence in a second sequence set with a length of B≥1, and a third sequence with a length of L, wherein the first sequence set includes Q first sequence subsets, each first sequence subset includes A constant envelope sequences, wherein all A constant envelope sequences are mutually orthogonal; the second sequence set includes Q constant envelope sequences, wherein the correlation between any two second sequences in the Q constant envelope sequences satisfies a third correlation criterion; and the third sequence is a constant envelope sequence.

18. The second communication device (300) according to claim 17, characterized in that: The modulation sequences in the set of QA modulation sequences are based on element-by-element multiplication of the periodic repetition of the first sequence, the periodic repetition of the second sequence, and the third sequence.

19. The second communication device (300) according to claim 17 or 18, characterized in that: The first sequence in each first sequence subset is a column of an A×A constant envelope orthogonal matrix, or an element-by-element multiplication of the columns of the A×A constant envelope orthogonal matrix and a cover sequence, wherein the A×A constant envelope orthogonal matrix is ​​any one of the following: an A×ADFT matrix, an A×A Hadamard matrix, an A×A matrix whose columns are different cyclic shift versions of a CAZAC sequence with a length of A and including a ZC sequence, or an A×A matrix whose columns are different cyclic shift versions of an mCAZAC sequence with a length of A; the cover sequence is a constant envelope sequence with a length of A, which is the same for all the first sequences in each first sequence subset, and may be the same or different for different first sequence subsets.

20. The second communication device (300) according to any one of claims 17 to 19, characterized in that: The second sequence is common to all modulation sequences in the same modulation sequence subset, and is different for modulation sequences in different modulation sequence subsets, wherein the length B of the second sequence is an integer, and the integer is a multiple of A and a factor of L; the second sequence is any one of the following: an all-"1" sequence of length B, a CAZAC / mCAZAC sequence of length B, a CAZAC / mCAZAC sequence of length less than B and periodically extended to length B, or a CAZAC / mCAZAC sequence of length greater than B and truncated to length B.

21. The second communication device (300) according to any one of claims 17 to 20, characterized in that: The length B of the second sequence is predefined; or The second communication device (300) is used to send a control signal (520) indicating the length B of the second sequence, wherein the length B of the second sequence is a length of The bit string indicates that N B is the number of integers in the set of integers that are multiples of A and factors of L; or is the number of integers in a predefined subset of the set of integers that are multiples of A and factors of L.

22. The second communication device (300) according to any one of claims 17 to 21, characterized in that: The third correlation criterion defines that the cross-correlation between all cyclic shifted versions of a second sequence in the second sequence set and another second sequence in the second sequence set is lower than a predetermined threshold.

23. The second communication device (300) according to any one of claims 17 to 22, characterized in that: The third sequence is any one of the following: a CAZAC / mCAZAC sequence with a length of L, a CAZAC / mCAZAC sequence with a length less than L and periodically extended to a length of L, or a CAZAC / mCAZAC sequence with a length greater than L and truncated to a length of L. m CAZAC sequence.

24. The second communication device (300) according to any one of claims 14 to 23, characterized in that: Used for: The reference signal (510) is received on a set of L subcarriers out of NNN consecutive subcarriers, NNN≥L, wherein the NNN consecutive subcarriers are divided into t subbands including an equal number of consecutive subcarriers; the set of L subcarriers includes A subcarriers from each subband, and the positions of the A subcarriers in each subband are the same for all the t subbands.

25. The second communication device (300) according to any one of claims 14 to 24, characterized in that: The value of Q is predefined; or The second communication device (100) is configured to send a control signal (520) indicating a value of Q.

26. The second communication device (300) according to any one of claims 14 to 25, characterized in that: The second communication device (300) is used to send a control signal (520) indicating an identifier of the modulation sequence, wherein the identifier of the modulation sequence is indicated in the following manner: include A single bit string of bits, where N group is the number of reference signal groups defined in the communication system (500); or The lengths are and wherein the first bit string indicates a reference signal group index, and the second bit string indicates an index of a modulation sequence in a set of modulation sequences associated with the reference signal group index; or The lengths are and The invention provides three bit strings, wherein the first bit string indicates a reference signal group index, the second bit string indicates an index of a modulation sequence subset in a set of modulation sequences associated with the reference signal group index, and the third bit string indicates an index of a modulation sequence in the modulation sequence subset.

27. A method (200) for a first communication device (100), characterized in that: The method (200) comprises: Acquire (202) a reference signal (510), wherein the reference signal (510) is based on a modulation sequence in a set of QA modulation sequences of length L≥1, the set of QA modulation sequences includes Q modulation sequence subsets, Q≥1, each modulation sequence subset includes A modulation sequences, A≥1, wherein a correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset satisfies a first correlation criterion; a correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets satisfies a second correlation criterion; and the correlation between any two reference signals in the same modulation sequence subset is lower than the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets; The reference signal (510) is sent (204).

28. A method (400) for a second communication device (300), characterized in that: The method (400) comprises: receiving (402) a reference signal (510); Obtaining (404) a modulation sequence from a set of Q4 modulation sequences of length L≥1, wherein the set of Q4 modulation sequences includes Q modulation sequence subsets, Q≥1, each modulation sequence subset includes A modulation sequences, A≥1, wherein a correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset satisfies a first correlation criterion; a correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets satisfies a second correlation criterion; and the correlation between any two reference signals based on any two modulation sequences in the same modulation sequence subset is lower than the correlation between any two reference signals based on any two modulation sequences in corresponding any two different modulation sequence subsets; A wireless channel (530) is estimated (406) based on the received reference signal (510) and the modulation sequence.

29. A computer program having a program code, characterized in that When the computer program is run on a computer, the program code is used to execute the method according to claim 27 or 28.

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