WO2023130726A1 - 一种基于互质阵列的非对称大规模mimo信道估计方法 - Google Patents
一种基于互质阵列的非对称大规模mimo信道估计方法 Download PDFInfo
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- 238000003491 array Methods 0.000 claims description 10
- 238000012545 processing Methods 0.000 claims description 5
- 238000005457 optimization Methods 0.000 claims description 4
- 230000008707 rearrangement Effects 0.000 claims description 4
- 238000012216 screening Methods 0.000 claims description 4
- 230000009466 transformation Effects 0.000 claims description 4
- 238000012935 Averaging Methods 0.000 claims description 3
- 230000008602 contraction Effects 0.000 claims description 3
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/0413—MIMO systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0204—Channel estimation of multiple channels
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/022—Channel estimation of frequency response
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/024—Channel estimation channel estimation algorithms
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
Definitions
- the invention relates to an asymmetric massive MIMO (Multiple Input Multiple Output, MIMO) channel estimation method based on a coprime array, belonging to the technical field of wireless communication.
- MIMO Multiple Input Multiple Output
- the technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide an asymmetric large-scale channel estimation method based on a coprime array in broadband multi-frequency point communication, which avoids the problems caused by the different numbers of antennas in the uplink and downlink arrays.
- the difference in angular resolution capability effectively ensures the reliability and accuracy of the reconstructed downlink channel information.
- the present invention provides an asymmetric massive MIMO channel estimation method based on a coprime array, comprising the following steps:
- the system includes a base station equipped with ultra-large-scale antennas and K users with single antennas; the number of base station antennas is M, and all antennas of the base station have transmission radio frequency chains Only N (N ⁇ M, K ⁇ N) receiving radio frequency links can be connected to N antennas for uplink receiving signals, and users and base stations use Q frequency points for communication.
- N N ⁇ M, K ⁇ N
- the base station receives and estimates the uplink channel information of some antennas, transforms it into the frequency domain and performs screening and rearrangement to construct a virtual linear uniform array;
- the present invention designs a partial-antenna channel estimation method based on a coprime array under an asymmetric transceiver architecture, using partial antennas to effectively and reliably restore the channel information of the complete array to overcome the rate loss caused by the difference between the uplink and downlink channels.
- the communication system proposed by the present invention first determine the number of antennas enabled in the uplink and downlink and the location of the specific activated antenna in the uplink according to the nested coprime array; then the pilot signals received on the activated part of the uplink antenna Fourier transform, which separates the frequency domain channel information of each frequency point in the frequency domain, and performs autocorrelation processing on the frequency domain signals of each frequency point, extracts virtual array element signals, screens, and rearranges them to form a virtual linear array Uniform array; then stretch the virtual array information on all frequency points into a vector, construct an observation matrix, and obtain the solution vector according to the iterative formula of the ADMM (Alternating Direction Method of Multipliers, ADMM) optimization framework, sort the solution vector and select the path , get the direction of arrival, reconstruct the uplink array manifold according to the direction of arrival, and obtain the path gain by least squares; finally, reconstruct the complete downlink array according to the previously estimated direction of arrival and path gain.
- ADMM Alternating Direction Method of Multipliers
- the present invention uses a coprime array to avoid asymmetry in channel information and resolution caused by different numbers of antennas in the uplink and downlink arrays, and the channel information estimated in the uplink can be directly used for downlink precoding in time-division duplex mode, effectively ensuring The communication rate of the asymmetric transceiver architecture is improved.
- the downlink array uses all antennas to send signals to maximize the communication rate; the uplink only uses some of the antennas activated according to the coprime array arrangement to receive signals, so as to reduce the pressure on uplink signal reception and decoding.
- the specific operation is as follows:
- the receiving and transmitting radio frequency chains of M antennas are designed separately, and there are M transmitting radio frequency links and N receiving radio frequency chains.
- S102 Select the uplink receiving antenna according to the coprime array, and connect the receiving radio frequency chain.
- the interval d between the antennas is ⁇ min /2, where ⁇ min is the wavelength corresponding to the subcarrier with the highest frequency in each frequency point.
- the interval d between the antennas is ⁇ min /2, where ⁇ min is the wavelength corresponding to the subcarrier with the highest frequency in each frequency point.
- the base station receives and estimates the uplink channel information of some antennas, transforms it into the frequency domain and performs screening and rearrangement, and constructs a virtual linear uniform array, which specifically includes the following steps:
- the column vector y i whose length is M is the frequency domain signal at the i-th frequency point
- [ ⁇ ] T means to take the transpose
- the specific selection method is as follows:
- the antenna numbers are recorded as 0, 1, 2,..., M-1, and the antenna array numbers activated in the uplink are recorded as a set of length N ⁇ p 1 ,p 2 ,...,p N ⁇ , arrange this set into an N ⁇ N matrix T c by column:
- Each element in the autocorrelation matrix R q is related to One-to-one correspondence among elements, that is, the element [R q ] i, j in row i, column j in R q is the element at position [R tab ] i, j in the virtual array.
- step S3 the group least absolute shrinkage selection operator based on compressed sensing is used to construct an estimation problem, and the problem is solved under the ADMM optimization framework, thereby estimating the direction of arrival, which specifically includes the following steps:
- a i,1 is the steering vector of the first frequency point on the i grid point
- a i,Q is the steering vector of the Qth frequency point on the i grid point
- a i,q is the steering vector of the qth frequency point on the i-th grid point
- the length of e 1 is M
- j is the imaginary number unit
- i is the order of grid points
- i is the order of grid points
- ⁇ q is the wavelength corresponding to the q-th frequency point
- ADMM Alternating Direction Method of Multipliers
- the column vector of length Q(w+1) is the target variable to be solved, representing the energy of each frequency point on each estimated grid point
- x 1 is The subvector composed of (1-1)Q+1 to 1Q elements
- x w+1 is The subvector composed of (w+1-1)Q+1 to w+1Qth elements
- x i is The subvector composed of (i-1)Q+1th to iQth elements
- z 1 is The subvector composed of (1-1)Q+1 to 1Q elements
- z w+1 is The subvector composed of (w+1-1)Q+1 to w+1Qth elements
- z i is A subvector composed of (i-1)Q+1 to iQth elements
- auxiliary variables ⁇ t is the penalty coefficient
- 2 means to take the 2-norm of the target vector.
- the k+1 iteration formula of the above problem is:
- I is the identity matrix, is the auxiliary variable
- u 1 is The subvector composed of (1-1)Q+1 to 1Q elements
- u w+1 is The subvector composed of (w+1-1)Q+1 to w+1Qth elements
- u i is The subvector composed of (i-1)Q+1 to iQth elements of , u i is defined like x i , the superscript ( ) (k) indicates the variable value of the kth iteration
- ⁇ is the iteration step size
- Indicates to take the real part of the complex number is the vector produced by the k+1th iteration
- the subvector composed of (i-1)Q+1th to iQth elements of , the convergence condition is:
- ⁇ is the convergence threshold, which is a small constant greater than 0;
- step S303 calculates the energy distribution vector on each estimated grid point (spatial direction) And for the vector
- the elements in are sorted, and the sorted for select middle front elements such that:
- ⁇ is the path restoration threshold , and it satisfies 0 ⁇ 1,
- ⁇ is the path restoration threshold , and it satisfies 0 ⁇ 1,
- ⁇ is the path restoration threshold , and it satisfies 0 ⁇ 1,
- the corresponding subscripts in form a set Indicates that the first selected element in the above formula is in in the original order, Indicates that the second selected element in the above formula is in in the original order, Indicates that the first selected elements in in the original order, Indicates that the lth selected element in the above formula is in The original order in , in the space
- the direction of arrival of a path is written in vector form as:
- step S4 the uplink partial array manifold matrix is reconstructed according to the estimated direction of arrival, and the path gain is estimated according to the observed instantaneous information in the frequency domain, which specifically includes the following steps:
- p 1 , p 2 , p n , p N are the order corresponding to the selected antenna in the uplink array, p n ⁇ 0,1,2,...,M-1 ⁇ , i ⁇ L;
- step S4 according to the path gain estimated in S402 and the direction of arrival estimated in S303, the complete uplink channel is reconstructed and symmetric to the downlink channel, and the specific operation is as follows:
- the present invention proposes a downlink channel estimation method based on a coprime array under asymmetric massive MIMO (Multi-Input Multi-Output, MIMO).
- MIMO Multi-Input Multi-Output
- MIMO Multi-Input Multi-Output
- the invention solves the problem that the recovered uplink channel cannot be directly used for downlink channel precoding by utilizing the feature of high angular resolution of the coprime array.
- the present invention effectively utilizes part of the antennas to estimate the complete downlink channel in the asymmetric architecture, and has obvious improvements in reducing uplink receiving pressure and improving channel recovery accuracy.
- the present invention adopts the above technical scheme and has the following technical effects:
- the present invention makes full use of the sparse multipath characteristics of high-frequency signals in space under the asymmetric transceiver architecture, transforms the original channel estimation problem into a parameter estimation problem, and utilizes the group minimum absolute contraction selection operator in ADMM (Alternating Direction Method of Multipliers, ADMM) optimization framework to quickly and accurately estimate the direction of arrival, while achieving the overall channel estimation accuracy, it also ensures the sparse characteristics of the channel model and prevents errors caused by subsequent overfitting.
- ADMM Alternating Direction Method of Multipliers
- the present invention introduces a coprime array into the uplink array of an asymmetric structure, which effectively eliminates the difference in the resolution capability of the uplink and downlink arrays, ensures the accuracy of channel reconstruction and the effectiveness of channel information available for downlink precoding, thereby improving system transfer rate.
- Fig. 1 is a flowchart of the present invention.
- Fig. 2 is a schematic diagram of selection of uplink receiving antennas in the present invention.
- This embodiment proposes an asymmetric massive MIMO channel estimation method based on a coprime array, as shown in FIG. 1 , including the following steps:
- the system includes a base station equipped with ultra-large-scale antennas (the number of antennas is M) and K users with single antennas. All antennas of the base station have transmitting radio frequency links, and only N (N ⁇ M, K ⁇ N) receiving radio frequency links can be connected to N antennas for uplink receiving signals, and users communicate with the base station using Q frequency points.
- the interval d between the antennas is ⁇ min /2, where ⁇ min is the wavelength corresponding to the subcarrier with the highest frequency in each frequency point.
- the base station receives and estimates the uplink channel information of some antennas, transforms it into the frequency domain and performs screening and rearrangement to construct a virtual linear uniform array. Include the following steps:
- the antenna numbers are recorded as 0, 1, 2,..., M-1, and the antenna array numbers activated in the uplink are recorded as a set of length N ⁇ p 1 ,p 2 ,...,p N ⁇ , arrange this set into an N ⁇ N matrix T c by column:
- Each element in the autocorrelation matrix R q is related to One-to-one correspondence among elements, that is, the element [R q ] i, j in row i, column j in R q is the element at position [R tab ] i, j in the virtual array.
- the column vector y i whose length is M is the frequency domain signal at the i-th frequency point
- [ ⁇ ] T means to take the transpose
- a i,1 is the steering vector of the first frequency point on the i grid point
- a i,Q is the steering vector of the Qth frequency point on the i grid point
- a i,q is the steering vector of the qth frequency point on the i-th grid point
- the length of e 1 is M
- j is the imaginary number unit
- i is the order of grid points
- i is the order of grid points
- ⁇ q is the wavelength corresponding to the q-th frequency point
- ADMM Alternating Direction Method of Multipliers
- the column vector of length Q(w+1) is the target variable to be solved, representing the energy of each frequency point on each estimated grid point
- x 1 is The subvector composed of (1-1)Q+1 to 1Q elements
- x w+1 is The subvector composed of (w+1-1)Q+1 to w+1Qth elements
- x i is The subvector composed of (i-1)Q+1th to iQth elements
- z 1 is The subvector composed of (1-1)Q+1 to 1Q elements
- z w+1 is The subvector composed of (w+1-1)Q+1 to w+1Qth elements
- z i is A subvector composed of (i-1)Q+1 to iQth elements
- auxiliary variables ⁇ t is the penalty coefficient
- 2 means to take the 2-norm of the target vector.
- the k+1 iteration formula of the above problem is:
- I is the identity matrix, is the auxiliary variable
- u 1 is The subvector composed of (1-1)Q+1 to 1Q elements
- u w+1 is The subvector composed of (w+1-1)Q+1 to w+1Qth elements
- u i is The subvector composed of (i-1)Q+1 to iQth elements of , u i is defined like x i , the superscript ( ) (k) indicates the variable value of the kth iteration
- ⁇ is the iteration step size
- Indicates to take the real part of the complex number is the vector produced by the k+1th iteration
- the subvector composed of (i-1)Q+1th to iQth elements of , the convergence condition is:
- ⁇ is the convergence threshold, which is a small constant greater than 0;
- step S303 calculates the energy distribution vector on each estimated grid point (spatial direction) And for the vector
- the elements in are sorted, and the sorted for select middle front elements such that:
- ⁇ is the path restoration threshold , and it satisfies 0 ⁇ 1,
- ⁇ is the path restoration threshold , and it satisfies 0 ⁇ 1,
- ⁇ is the path restoration threshold , and it satisfies 0 ⁇ 1,
- the corresponding subscripts in form a set Indicates that the first selected element in the above formula is in in the original order, Indicates that the second selected element in the above formula is in in the original order, Indicates that the first selected elements in in the original order, Indicates that the lth selected element in the above formula is in The original order in , in the space
- the direction of arrival of a path is written in vector form as:
- p 1 , p 2 , p n , p N are the order corresponding to the selected antenna in the uplink array, p n ⁇ 0,1,2,...,M-1 ⁇ , i ⁇ L;
- step S4 according to the path gain estimated in S402 and the direction of arrival estimated in S303, the complete uplink channel is reconstructed and symmetric to the downlink channel, and the specific operation is as follows:
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Abstract
本发明在非对称大规模MIMO下提出了一种基于互质阵列的下行信道估计方法。首先,构建基于互质阵列的上下行非对称收发系统模型,并关注阵列宽带信号带来的频域方向偏移;其次,进行上行接收估计出上行信道,并由此恢复路径数,到达角,路径增益等信道参数;最后,利用上行信道恢复出的信道参数重建下行信道;对于宽带信号还可以利用不同频点上的群稀疏特性提高信道估计精度。本发明利用互质阵列角度分辨率高的特点,解决了恢复出的上行信道无法直接用于下行信道预编码的问题。本发明在非对称架构中有效地利用部分天线估计完整的下行信道,在降低上行链路接收压力和提高信道恢复准确性方面具有明显改善。
Description
本发明涉及一种基于互质阵列的非对称大规模MIMO(Multiple Input Multiple Output,MIMO)信道估计方法,属于无线通信技术领域。
据了解,在广泛部署第五代移动通信系统中,大规模MIMO技术得到了进一步应用与拓展,显示了MIMO阵列在速率,频谱效率以及可靠性方面的优越性能。为满足不断增长的速率和可靠性需求,人们希望进一步扩大MIMO阵列的规模,但随之而来的硬件成本,数据处理负担以及功耗要求限制了全数字大规模MIMO技术的进一步发展。尽管已经有许多文献提出了各种替代方案,如混合波束赋形,低精度数模/模数转换器,天线选择等技术,但这些技术都不可避免地牺牲了部分通信性能,这在对速率要求越来越高的多样化网络业务中是令人难以接收的。为了在保证用户体验的同时,尽可能降低基站的成本,近期有学者提出了一种新型的全数字非对称收发架构。这种架构的非对称性体现在上下行收发过程的差异,即通过解耦发送与接收的射频链路,允许上行仅用部分天线进行接收,下行全部天线都可用于发送信号。这种设计理念的初衷源于上下行通信需求的不同。下行通信中速率是影响用户体验的最直观指标,然而上行的数据吞吐量相比下行要小很多。为此上行仅需部分天线即可满足基站信息搜集的需求。这种设计方式由于上下行阵列天线数目不同容易带来角度分辨能力的差异,会导致下行信道信息不可靠、不准确。
发明内容
本发明所要解决的技术问题是,克服现有技术的不足而提供一种宽带多频点通信中的基于互质阵列的非对称大规模信道估计方法,避免了上下行阵列由于天线数目不同带来的角度分辨能力差异,有效地保证了重建出的下行信道信息可靠性与准确性。
本发明提供一种基于互质阵列的非对称大规模MIMO信道估计方法,包括以下步骤:
S1、构建基于互质阵列的上下行非对称大规模MIMO系统,该系统包括一个配有超大规模天线的基站和K个单天线的用户;基站天线数为M,基站所有天线都有发送射频链路,只有N(N<<M,K≤N)根接收射频链路可连接到N根天线用于上行接收信号,用户与基站用Q个频点进行通信。数目关系为:M=mn+1,N=m+n-1,其中m<n,且m,n互质;按照互质阵列的方式选取上行接收天线,连接接收射频链;
S2、基站方接收并估计得到部分天线的上行信道信息,将其变换到频域并进行筛选重排后,构造虚拟线性均匀阵列;
S3、利用空间稀疏特性构造基于压缩感知的群最小绝对收缩选择算子,估计来波方向;
S4、根据估计出的来波方向重构部分阵列流形矩阵,并根据后续观测到的频域瞬时信息估计路径增益;
S5、依据估计出的路径增益,来波方向重构完整的上行信道,根据互易性将其对称至下行信道。
本发明在非对称收发架构下设计一种基于互质阵列的部分天线信道估计方法,使用部分天线来有效且可靠地恢复完整阵列信道信息,用于克服上下行信道差异性带来的速率损失。本发明在提出的通信系统中,首先按照嵌套互质阵列的方式确定上下行各自启用的 天线数目以及上行具体激活的天线所在位置;然后将被激活的部分上行天线上接收的导频信号进行傅里叶变换,在频域上将各个频点的频域信道信息分离开来,并对各个频点的频域信号做自相关处理,提取虚拟阵元信号、筛选、重排后形成虚拟线性均匀阵列;接着将所有频点上的虚拟阵列信息拉伸成向量,构造观测矩阵,按照ADMM(Alternating Direction Method of Multipliers,ADMM)优化框架的迭代公式求得解向量,对解向量排序选取路径后,得到来波方向,依据来波方向重构上行阵列流形,用最小二乘求得路径增益;最后依据先前估计出来的来波方向和路径增益重建完整的下行阵列。本发明利用互质阵列避免了上下行阵列由于天线数不同导致的信道信息和分辨率上的非对称性,上行估计出的信道信息在时分双工模式下可以直接用于下行预编码,有效保证了非对称收发架构的通信速率。
本发明进一步优化的技术方案如下所示:
所述步骤S1中,下行阵列使用所有天线发送信号,以最大化通信速率;上行仅使用部分按照互质阵列排布方式激活的天线接收信号,以减少上行信号接收与解码压力。具体操作如下:
S101、M根天线的接收和发送射频链分开设计电路,有M条发送射频链路和N条接收射频链,数目关系为:M=mn+1,N=m+n-1,其中m<n,且m,n互质。
S102、根据互质阵列的方式选取上行接收天线,连接接收射频链,具体选取方式为:选中起始的连续n根,第2n+1根,第3n+1根,…,直至第mn+1根,共计N=m+n-1根。天线之间间隔d为λ
min/2,其中λ
min是各个频点中频率最大的子载波对应的波长。
所述步骤S1中,选取上行接收天线的具体方式为:选中起始的 连续n根,第2n+1根,第3n+1根,…,直至第mn+1根,共计N=m+n-1根天线(m,n分别是互质的两个数,用于设计非对称阵列上下行天线的个数)。天线之间的间隔d为λ
min/2,其中λ
min是各个频点中频率最大的子载波所对应的波长。
所述步骤S2中,基站方接收并估计得到部分天线的上行信道信息,将其变换到频域并进行筛选重排后,构造虚拟线性均匀阵列,具体包括以下步骤:
S201、在连续的P个符号时间内,对上行阵列收到的P组Q个离散时域信号分别进行Q点FFT(Fast Fourier Transform,FFT)变换,得到P组Q个频点上的频域信号,记N×1的列向量x
p,q为第p组信号中第q个频点对应的频域信号;
S202、对每个频点的P个频域信号进行自相关处理,得到Q个N×N的自相关矩阵:
在R
q中将重复位置的阵元进行分类(上三角对应负滞后部分,故舍去)、平均后,按照顺序将其排列成长为M×1的列向量y
q,[·]
H表示共轭转置,[·]
T表示转置;
S203、将所有频点上的虚拟阵列信号排成一个QM的列向量:
其中,长为M的列向量y
i是第i个频点上的频域信号,[·]
T表示取转置。
所述步骤S202中,具体选取方式如下:
将完整的阵列从一端开始,天线序号记为0,1,2,…,M-1,其中上行激活的天线阵列序号记为一个长为N的集合{p
1,p
2,…,p
N},将此集 合按列排出一个N×N的矩阵T
c:
所述步骤S3中,利用基于压缩感知的群最小绝对收缩选择算子构造估计问题,在ADMM优化框架下求解该问题,从而估计来波方向,具体包括以下步骤:
S301、在预先设定的入射角区间[θ
l,θ
r]上构造QM×Q(w+1)的观测矩阵
θ
l,θ
r分别是左角度边界和右角度边界,并满足0≤θ
l<θ
r≤π,这两个边界值可以通过DFT(Discrete Fourier Transform,DFT)等角度域检测手段获得;若不进行检测则θ
l=0,θ
r=π。w是在估计区间[θ
l,θ
r]上划分的格点个数,w越大估计结果越精确,但复杂度也提示,QM×Q的子矩阵A
i是第i个格点上的观测矩阵,
是用于估计噪声的矩阵,各子观测矩阵按如下方式生成:
其中省略号位置全部为0,a
i,1是第1个频点在第i个格点上的导向矢量,a
i,Q是第Q个频点在第i个格点上的导向矢量,a
i,q是第q个频点在第i个格点上的导向矢量,且:
e
1=[1,0,…,0]
T,
S302、依据压缩感知理论在ADMM(Alternating Direction Method of Multipliers,ADMM)框架下写出L21范数约束的线性回归问题:
其中,长度为Q(w+1)的列向量
是待求解的目标变量,代表着各个频点在各个估计格点上的能量大小,x
1是
的第(1-1)Q+1到第1Q个元素组成的子向量,x
w+1是
的第(w+1-1)Q+1到第w+1Q个元素组成的子向量,x
i是
的第(i-1)Q+1到第iQ个元素组成的子向量,z
1是
的第(1-1)Q+1到第1Q个元素组成的子向量,z
w+1是
的第(w+1-1)Q+1到第w+1Q个元素组成的子向量,z
i是
的第(i-1)Q+1到第iQ个元素组成的子向量,辅助变量
λ
t是惩罚系数,||·||
2表示取目标向量的2范数。上述问题的第k+1次迭代公式为:
其中,I是单位矩阵,
是辅助变量,u
1是
的第(1-1)Q+1到第1Q个元素组成的子向量,u
w+1是
的第(w+1-1)Q+1到第w+1Q个元素组成的子向量,u
i是
的第(i-1)Q+1到第iQ个元素组成 的子向量,u
i定义类似x
i,上标(·)
(k)表示第k次迭代的变量值,ρ是迭代步长,可取定值,
表示取复数的实数部分,
是第k+1次迭代产生的向量
的第(i-1)Q+1到第iQ个元素组成的子向量,收敛条件为:
其中,η是路径恢复门限,且满足0<η<1,||·||
1表示取目标向量的1范数,[·]
i表示向量的第i个元素,记恢复出的
个元素在向量
中对应的下标构成集合
表示上式中第1个被选出的元素在
中的原始顺序,
表示上式中第2个被选出的元素在
中的原始顺序,
表示上式中第
个被选出的元素在
中的原始顺序,
表示上式中第l个被选出的元素在
中的原始顺序,空间中
条路径的来波方向写成向量形式为:
所述步骤S4中,根据估计出的来波方向重构上行部分阵列流形矩阵,并根据观测到的频域瞬时信息估计路径增益,具体包括以下步骤:
p
1,p
2,p
n,p
N都是上行阵列中被选中的天线对应的次序,p
n∈{0,1,2,…,M-1},i∈L;
所述步骤S4中,依据S402中估计出的路径增益,S303中估计出的来波方向重构完整的上行信道并将其对称至下行信道,具体操作如下:
重建所有天线上M×1的完整信道:
总之,本发明在非对称大规模MIMO(Multi-Input Multi-Output,MIMO)下提出了一种基于互质阵列的下行信道估计方法。首先,构建基于互质阵列的上下行非对称收发系统模型,并关注阵列宽带信号带来的频域方向偏移;其次,进行上行接收估计出上行信道,并由此恢复路径数,到达角,路径增益等信道参数;最后,利用上行信道恢复出的信道参数重建下行信道;对于宽带信号还可以利用不同频点上的群稀疏特性提高信道估计精度。本发明利用互质阵列角度分辨率高的特点,解决了恢复出的上行信道无法直接用于下行信道预编码的问题。本发明在非对称架构中有效地利用部分天线估计完整的下行信道,在降低上行链路接收压力和提高信道恢复准确性方面具有明显改善。
本发明采用以上技术方案与现有技术相比,具有以下技术效果:
(1)本发明在非对称收发架构下充分利用了高频信号在空间中的稀疏多径特性,将原本的信道估计问题转化为参数估计问题,利用群最小绝对收缩选择算子在ADMM(Alternating Direction Method of Multipliers,ADMM)优化框架下快速准确地估计来波方向,在达到 整体信道估计精度的同时,还确保了信道模型的稀疏特性,防止后续过拟合带来的误差。
(2)本发明在非对称架构的上行阵列中引入互质阵列,有效地消除了上下行阵列的分辨能力差异,确保了重建信道的准确性和下行预编码可用信道信息的有效性,从而提升系统的传输速率。
图1为本发明的流程图。
图2为本发明中上行接收天线的选取示意图。
下面结合附图对本发明的技术方案做进一步的详细说明:本实施例在以本发明技术方案为前提下进行实施,给出了详细的实施方式和具体的操作过程,但本发明的保护权限不限于下述的实施例。
本实施例提出了一种基于互质阵列的非对称大规模MIMO信道估计方法,如图1所示,包括以下步骤:
S1、构建基于互质阵列的上下行非对称大规模MIMO系统,该系统包括一个配有超大规模天线(天线数为M)的基站和K个单天线的用户。基站所有天线都有发送射频链路,只有N(N<<M,K≤N)根接收射频链路可连接到N根天线用于上行接收信号,用户与基站用Q个频点进行通信。数目关系为:M=mn+1,N=m+n-1,其中m<n,且m,n互质。按照互质阵列的方式选取上行接收天线,连接接收射频链,具体选取方式为:选中起始的连续n根,第2n+1根,第3n+1根,…,直至第mn+1根,共计N=m+n-1根天线(m,n分别是互质的两个数,用于设计非对称阵列上下行天线的个数)。天线之间的间隔d为λ
min/2,其中λ
min是各个频点中频率最大的子载波所对应的波长。
S2、基站方接收并估计得到部分天线的上行信道信息,将其变换 到频域并进行筛选重排后,构造虚拟线性均匀阵列。包括以下步骤:
S201、在连续的P个符号时间内,对上行阵列收到的P组Q个离散时域信号分别进行Q点FFT(Fast Fourier Transform,FFT)变换,得到P组Q个频点上的频域信号。记N×1的列向量x
p,q为第p组信号中第q个频点对应的频域信号。
S202、对每个频点的P个频域信号进行自相关处理,得到Q个N×N的自相关矩阵:
在R
q中将重复位置的阵元进行分类(上三角对应负滞后部分,故舍去)、平均后,按照顺序将其排列成长为M×1的列向量y
q,[·]
H表示共轭转置,[·]
T表示转置。具体选取方式如下:
将完整的阵列从一端开始,天线序号记为0,1,2,…,M-1,其中上行激活的天线阵列序号记为一个长为N的集合{p
1,p
2,…,p
N},将此集合按列排出一个N×N的矩阵T
c:
S203、将所有频点上的虚拟阵列信号排成一个QM的列向量:
其中,长为M的列向量y
i是第i个频点上的频域信号,[·]
T表示取转置。
S3、利用空间稀疏特性构造基于压缩感知的群最小绝对收缩选 择算子,估计来波方向。包括以下步骤:
S301、在预先设定的入射角区间[θ
l,θ
r]上构造QM×Q(w+1)的观测矩阵
θ
l,θ
r分别是左角度边界和右角度边界,并满足0≤θ
l<θ
r≤π,这两个边界值可以通过DFT(Discrete Fourier Transform,DFT)等角度域检测手段获得;若不进行检测则θ
l=0,θ
r=π。w是在估计区间[θ
l,θ
r]上划分的格点个数,w越大估计结果越精确,但复杂度也提示,QM×Q的子矩阵A
i是第i个格点上的观测矩阵,
是用于估计噪声的矩阵,各子观测矩阵按如下方式生成:
其中省略号位置全部为0,a
i,1是第1个频点在第i个格点上的导向矢量,a
i,Q是第Q个频点在第i个格点上的导向矢量,a
i,q是第q个频点在第i个格点上的导向矢量,且:
e
1=[1,0,…,0]
T,
S302、依据压缩感知理论在ADMM(Alternating Direction Method of Multipliers,ADMM)框架下写出L21范数约束的线性回归问题:
其中,长度为Q(w+1)的列向量
是待求解的目标变 量,代表着各个频点在各个估计格点上的能量大小,x
1是
的第(1-1)Q+1到第1Q个元素组成的子向量,x
w+1是
的第(w+1-1)Q+1到第w+1Q个元素组成的子向量,x
i是
的第(i-1)Q+1到第iQ个元素组成的子向量,z
1是
的第(1-1)Q+1到第1Q个元素组成的子向量,z
w+1是
的第(w+1-1)Q+1到第w+1Q个元素组成的子向量,z
i是
的第(i-1)Q+1到第iQ个元素组成的子向量,辅助变量
λ
t是惩罚系数,||·||
2表示取目标向量的2范数。上述问题的第k+1次迭代公式为:
其中,I是单位矩阵,
是辅助变量,u
1是
的第(1-1)Q+1到第1Q个元素组成的子向量,u
w+1是
的第(w+1-1)Q+1到第w+1Q个元素组成的子向量,u
i是
的第(i-1)Q+1到第iQ个元素组成的子向量,u
i定义类似x
i,上标(·)
(k)表示第k次迭代的变量值,ρ是迭代步长,可取定值,
表示取复数的实数部分,
是第k+1次迭代产生的向量
的第(i-1)Q+1到第iQ个元素组成的子向量,收敛条件为:
其中,η是路径恢复门限,且满足0<η<1,||·||
1表示取目标向量的1范数,[·]
i表示向量的第i个元素,记恢复出的
个元素在向量
中对应的下标构成集合
表示上式中第1个被选出的元素在
中的原始顺序,
表示上式中第2个被选出的元素在
中的原始顺序,
表示上式中第
个被选出的元素在
中的原始顺序,
表示上式中第l个被选出的元素在
中的原始顺序,空间中
条路径的来波方向写成向量形式为:
S4、根据估计出的来波方向重构部分阵列流形矩阵,并根据后续观测到的频域瞬时信息估计路径增益。包括以下步骤:
p
1,p
2,p
n,p
N都是上行阵列中被选中的天线对应的次序, p
n∈{0,1,2,…,M-1},i∈L;
S5、依据估计出的路径增益,来波方向重构完整的上行信道,根据互易性将其对称至下行信道。具体操作如下:
所述步骤S4中,依据S402中估计出的路径增益,S303中估计出的来波方向重构完整的上行信道并将其对称至下行信道,具体操作如下:
重建所有天线上M×1的完整信道:
以上所述,仅为本发明中的具体实施方式,但本发明的保护范围并不局限于此,任何熟悉该技术的人在本发明所揭露的技术范围内,可理解想到的变换或替换,都应涵盖在本发明的包含范围之内,因此,本发明的保护范围应该以权利要求书的保护范围为准。
Claims (7)
- 一种基于互质阵列的非对称大规模MIMO信道估计方法,其特征在于,包括以下步骤:S1、构建基于互质阵列的上下行非对称大规模MIMO系统,该系统包括一个配有超大规模天线的基站和K个单天线的用户;基站天线数为M,基站所有天线都有发送射频链路,只有N根接收射频链路可连接到N根天线用于上行接收信号,用户与基站用Q个频点进行通信,数目关系为:M=mn+1,N=m+n-1,其中m<n,且m,n互质;按照互质阵列的方式选取上行接收天线,连接接收射频链;S2、基站方接收并估计得到部分天线的上行信道信息,将其变换到频域并进行筛选重排后,构造虚拟线性均匀阵列;S3、利用空间稀疏特性构造基于压缩感知的群最小绝对收缩选择算子,估计来波方向;S4、根据估计出的来波方向重构部分阵列流形矩阵,并根据后续观测到的频域瞬时信息估计路径增益;S5、依据估计出的路径增益,来波方向重构完整的上行信道,根据互易性将其对称至下行信道。
- 根据权利要求1所述一种基于互质阵列的非对称大规模MIMO信道估计方法,其特征在于,所述步骤S1中,选取上行接收天线的具体方式为:选中起始的连续n根,第2n+1根,第3n+1根,…,直至第mn+1根,共计N=m+n-1根天线;天线之间的间隔d为λ min/2, 其中λ min是各个频点中频率最大的子载波所对应的波长。
- 根据权利要求2所述一种基于互质阵列的非对称大规模MIMO信道估计方法,其特征在于,所述步骤S2中,基站方接收并估计得到部分天线的上行信道信息,将其变换到频域并进行筛选重排后,构造虚拟线性均匀阵列,具体包括以下步骤:S201、在连续的P个符号时间内,对上行阵列收到的P组Q个离散时域信号分别进行Q点FFT变换,得到P组Q个频点上的频域信号,记N×1的列向量x p,q为第p组信号中第q个频点对应的频域信号;S202、对每个频点的P个频域信号进行自相关处理,得到Q个N×N的自相关矩阵:在R q中将重复位置的阵元进行分类、平均后,按照顺序将其排列成长为M×1的列向量y q;S203、将所有频点上的虚拟阵列信号排成一个QM的列向量:其中,长为M的列向量y i是第i个频点上的频域信号。
- 根据权利要求4所述一种基于互质阵列的非对称大规模MIMO信道估计方法,其特征在于,所述步骤S3中,利用基于压缩感知的群最小绝对收缩选择算子构造估计问题,在ADMM优化框架下求解该问题,从而估计来波方向,具体包括以下步骤:S301、在预先设定的入射角区间[θ l,θ r]上构造QM×Q(w+1)的观测矩阵 θ l,θ r分别是左角度边界和右角度边界,并满足0≤θ l<θ r≤π,w是在估计区间[θ l,θ r]上划分的格点个数,QM×Q的子矩阵A i是第i个格点上的观测矩阵, 是用于估计噪声的矩阵,各子观测矩阵按如下方式生成:a i,q是第q个频点在第i个格点上的导向矢量,且:e 1=[1,0,...,0] T,S302、依据压缩感知理论在ADMM框架下写出L21范数约束的线性回归问题:其中,长度为Q(w+1)的列向量 是待求解的目标变量,代表着各个频点在各个估计格点上的能量大小,x i是 的第(i-1)Q+1到第iQ个元素组成的子向量,z i是 的第(i-1)Q+1到第iQ个元素组成的子向量,辅助变量 λ t是惩罚系数,上述问题的第k+1次迭代公式为:
- 根据权利要求5所述一种基于互质阵列的非对称大规模MIMO信道估计方法,其特征在于,所述步骤S4中,根据估计出的来波方向重构上行部分阵列流形矩阵,并根据观测到的频域瞬时信息估计路径增益,具体包括以下步骤:p n是上行阵列中被选中的天线对应的次序,p n∈{0,1,2,...,M-1},i∈L;
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