CN101868018B - Method for allocating low-bit feedback user frequencies of MIMO - Google Patents

Abstract

The invention discloses a low-bit feedback user power distribution method for MIMO. Firstly, numbers reflecting priority levels of power distribution are defined for user antennas, and all number arrangements of each antenna are obtained through permutation and combination. The base station sends test signals, and the user assigns antenna numbers to each antenna according to the principle that the greater the signal-to-noise ratio, the higher the priority, and feeds back the number information to the base station along with the maximum and minimum values of the signal-to-noise ratio, and the base station calculates the signal-to-noise ratio. value, and use this to select users and make the first power allocation. Finally, the base station allocates power to each antenna for the second time according to the criterion that the higher the priority of the antenna number is, the higher the antenna allocation power is based on the feedback number information. . The present invention overcomes the defect that the traditional user sub-channel estimation requires too much feedback information, can effectively estimate the basic state of all sub-channels of the user under the condition of reducing the amount of feedback information, perform reasonable user power allocation, improve transmission performance, and improve data transmission throughput.

Description

A Low Bit Feedback User Power Allocation Method for MIMO

technical field

The invention relates to the field of multiple-input multiple-output (MIMO) communication, in particular to a low bit feedback user power allocation method for MIMO.

Background technique

In the MIMO communication system, it configures multiple antenna units at both ends of the transceiver, and through time-space joint processing technology, the multipath propagation that is usually considered harmful in wireless propagation is transformed into multipath delay extension that is beneficial to users, thereby Increased transfer rate.

However, in the MIMO system, the Dirty Paper Coding (DPC) transmission scheme, which can theoretically achieve the optimal capacity, has very low practicability due to its high encoding and decoding complexity and strict requirements on channel information accuracy. Subsequent researchers have also conducted research on suboptimal transmission schemes with lower complexity, and zero-forcing beamforming technology (ZFBF), according to research, such as A.Goldsmith et al. "On the optimality of multiantennabroadcast scheduling using zero-forcing beamforming", IEEEJournal on Selected Area of Comm., Vol.24, No.3, March 2006, can approach the upper limit of throughput in MIMO systems with relatively low processing complexity when the number of users is large. However, this method requires all users to feed back all antenna sub-channel information in each time slot for reasonable user selection and power allocation. This will bring a lot of feedback overhead to the users, and due to the large number of users, the complexity of selecting a user set by the base station is very high.

Contents of the invention

The purpose of the present invention is to provide a low-bit feedback user power allocation method for MIMO, which reduces the number of bits that users need to feed back, shortens the time for the base station to select a transmission user set, improves transmission performance, and improves data transmission throughput.

A low bit feedback user power allocation method for MIMO, specifically:

(1) Each user determines its own antenna number set:

(1.1) Customize n different antenna numbers, which should reflect the priority level of antenna power allocation, and n is the number of antennas for this user;

(1.2) Arrange and combine n antenna numbers to obtain the antenna number set A _user ={a _i , i=1, 2..., 2·n! }, the j-th element of the i-th arrangement a _i is the number of the j-th antenna;

(2) The base station stores the antenna number sets of all users;

(3) The base station sends test signals to all antennas of all users;

(4) Each user receives the test signal and operates as follows:

(4.1) The larger the signal-to-noise ratio of the received signal, the higher the priority of the antenna power allocation to each antenna is given the number defined in step (1.1);

(4.2) the sequence number z of the numbering result obtained in the query step (4.1) in the user's antenna numbering set;

(4.3) Feedback serial number z, maximum signal-to-noise ratio _{Su_max} and minimum signal-to-noise ratio _{Su_min} to the base station;

(5) The feedback from the base station to each user is processed in the following manner:

(5.1) Calculate the median value of SNR S _{u_aver} = (S _{u_max} + S _{u_min} )/2;

(5.2) If the median SNR value _{Su_aver} is greater than the threshold value S _thresh , allocate power P _u to the user, and enter step (5.3), otherwise, do not allocate power to the user, and end;

(5.3) The base station searches for the antenna number arrangement a _z in the user's antenna number set, and allocates the power P _u to each antenna according to the principle that the higher the priority of the antenna number, the higher the power allocated to the antenna.

Compared with the prior art, the present invention has the advantages that: in D.A.Gore et al. "Transmitselection in spatial multiplexing systems", IEEE Comm.Letters, Vol.6, No.11, Nov.2002, all sub-channels are analyzed The signal-to-noise ratio is a random variable that obeys the Chisquared distributed, and the signal-to-noise ratio of the channel is a key factor that affects channel information. This provides a theoretical basis for rationally designing feedback schemes and simplifying scheduling processing methods. The present invention determines the range of channel state information (CSI) of each subchannel of the user by sorting the SNRs of all subchannels at the user end; the end user end only feeds back the maximum value, minimum value and antenna arrangement number of all subchannel SNRs, It greatly reduces the amount of information that needs to be fed back by the user end, and reduces the feedback overhead; while the base station only needs to calculate the median value of the SNR of all sub-channels fed back by each user to obtain the basic information of the user's channel state, thus reducing the cost of the base station. The terminal selects the complexity of the transmission user, and reasonably allocates power; at the same time, the secondary allocation is performed according to the user's antenna sequence number, which can further improve the overall performance of the user on the basis of ensuring the basic performance of the user, and also ensure the power of the subchannel. Assignment flexibility.

Description of drawings

Fig. 1 is a flow chart of the method of the present invention;

Fig. 2 is a schematic diagram of the ratio between the number of bits that need to be fed back by using the present invention and the number of bits that need to be fed back to the SNR of all user sub-channels in the traditional way when the maximum number of user antennas is 3 to 10.

Detailed ways

The present invention will be further described in detail below in conjunction with specific implementation examples.

This implementation example adopts a downlink multi-user MIMO system with K=20 users. The base station configures M=12 antennas, and the user configures 3 to 5 antennas. Assuming that after precoding processing, the user antenna will be decomposed into independent sub-channels, and each sub-channel obeys the chi-square distribution.

(1) Each user determines the set of antenna numbers:

Taking the user with 4 antennas as an example, define the four antenna numbers as 1, 2, 3, and 4, among which 1 means that the priority of antenna power allocation is the lowest, 2 is higher than 1, 3 is higher than 2, and 4 has the highest priority . User antenna arrangement set A _user = {a ₁ , a ₂ , ..., a ₄₈ }, a ₁ = (1, 2, 3, 4), a ₂ = (1, 2, 4, 3), ..., i-th The jth element of an array a _i is the number of the jth antenna, i=1, 2...,48.

(2) The base station stores the antenna number sets of all users;

(3) The base station sends test signals to all antennas of all users;

(4) Each user receives the test signal and operates as follows:

The user sorts the antennas from large to small according to the SNR of the signal received by each antenna. Assuming that the user has 4 antennas, the SNR received by the first antenna to the fourth antenna is {10dB, 8dB, 11dB, 3dB} , assign numbers to the first to fourth antennas according to the principle that the greater the signal-to-noise ratio of the received signal, the higher the priority of antenna power allocation, and then assign numbers to get {3, 2, 4, 1}. The user first searches the antenna arrangement set, and obtains that the antenna arrangement number corresponding to the number {3, 2, 4, 1} is 140. And record the maximum value 11dB and the minimum value 3dB of the user sub-channel SNR. The user sends the maximum value of SNR 11dB, the minimum value of 3dB and the antenna arrangement number 140 to the base station.

(5) The base station performs user selection and power allocation for the first time.

Take step (4) as an example:

(5.1) The base station performs median processing according to the maximum value and minimum value of the SNR fed back by the user, namely $S_{u\_\mathrm{aver}}=(11\mathrm{dB}+3\mathrm{dB})/2=\sqrt{11.3}\mathrm{dB}\≈5.7\mathrm{dB}.$

(5.2) The base station selects the user according to the user's median value _{Su_aver} = 5.7dB, if the median value is greater than the threshold value (generally 3-5dB), the user is selected, and the base station communicates with the selected user.

When the base station communicates with these selected users, it must first allocate power to the users, and the water injection algorithm can be used (that is, the power is allocated according to the size of the _{Su_aver} of the user, the allocation power is small if the _{Su_aver} is small, and the allocation power is large if the _{Su_aver} is large) To maximize the user channel capacity. The user with _{Su_aver} =5.7dB is allocated power of 1 mW.

(6) The base station performs the second power allocation according to the antenna arrangement number of the selected user

Also take step (4) as an example for illustration:

(6.1) The base station searches for the corresponding antenna arrangement number a ₁₄₀ in the antenna number set of the selected user.

其中，k_i为根据用户天线排列序号a_i查到的第i根天线对应的数字编号。实例中，n＝4，P_u＝1mW，按照这样的分配策略，用户的四根天线分配到得功率分别为 $\{1\mathrm{mW}\·\frac{3}{3+2+4+1},1\mathrm{mW}\·\frac{2}{3+2+4+1},1\mathrm{mW}\·\frac{4}{3+2+4+1},1\mathrm{mW}\·\frac{1}{3+2+4+1}\},$ 即{0.3mW，0.2mW，0.4mW，0.1mW}。该量化方式充分体现出将第一次分配的用户功率按照天线编号体现的优先级越高，对该天线分配的功率越高的准则分配给各天线，具体分配方式不局限于此，只要满足此原则的任何方式均可。(6.2) Perform subchannel user power quantization according to the number of user antennas, and the quantization method is:

Wherein, _ki is the number corresponding to the i-th antenna found according to the serial number a _i of the user's antenna arrangement. In the example, n=4, P _u =1mW, according to this allocation strategy, the power allocated to the four antennas of the user is $\{1\mathrm{mW}\&Center\; Dot;\frac{3}{3+2+4+1},1\mathrm{mW}\&Center\; Dot;\frac{2}{3+2+4+1},1\mathrm{mW}\·\frac{4}{3+2+4+1},1\mathrm{mW}\&Center\; Dot;\frac{1}{3+2+4+1}\},$ That is {0.3mW, 0.2mW, 0.4mW, 0.1mW}. This quantization method fully reflects that the user power allocated for the first time is allocated to each antenna according to the principle that the higher the priority reflected by the antenna number, the higher the power allocated to the antenna is. The specific allocation method is not limited to this, as long as this is satisfied Any method in principle is acceptable.

When a selected user has more than 3 antennas, the number of bits that need to be fed back by this feedback method will be less than the number of bits that need to be fed back the SNR of all antenna sub-channels of the user. And the ratio of the number of bits fed back by this method to the number of bits fed back by the original method will decrease as the number of user antennas increases. Fig. 2 shows that when the number of user antennas increases from 3 to 10, the changes in the ratio of the number of bits that need to be fed back by the two methods.

The defined numbering form is not limited to the numerical form in the example, and any other form such as letters can be used. The key point is to clarify the priority relationship of each numbering.

Claims (1)

1. A low bit feedback user power allocation method for MIMO, specifically: (1) Each user determines its own antenna number set: (1.1) Customize n different antenna numbers, which should reflect the priority level of antenna power allocation, and n is the number of antennas for this user; (1.2) Arrange and combine n antenna numbers to obtain the antenna number set A _user ={a _i , i=1, 2..., 2·n! }, the j-th element of the i-th arrangement a _i is the number of the j-th antenna; (2) The base station stores the antenna number sets of all users; (3) The base station sends test signals to all antennas of all users; (4) Each user receives the test signal and operates as follows: (4.1) assign the number defined in step (1.1) to each antenna according to the greater the signal-to-noise ratio of the received signal, the higher the priority of the antenna power allocation; (4.2) the sequence number z of the numbering result obtained in the query step (4.1) in the user's antenna numbering set; (4.3) Feedback the serial number z, the maximum signal-to-noise ratio _{Su_max} and the minimum signal-to-noise ratio _{Su_min} of the signal received by the antenna to the base station; (5) The feedback from the base station to each user is processed in the following manner: (5.1) Calculate the median value of SNR S _{u_aver} = (S _{u_max} + S _{u_min} )/2; (5.2) If the median SNR value _{Su_aver} is greater than the threshold value S _thresh , allocate power P _u to the user, and enter step (5.3), otherwise, do not allocate power to the user, and end; (5.3) The base station searches for the antenna number arrangement a _z in the user's antenna number set, and allocates the power P _u to each antenna according to the principle that the higher the priority of the antenna number, the higher the power allocated to the antenna.

Images