CN104113399A - Multi-user user selection method based on matrix condition number in multiple input multiple output (MIMO) system - Google Patents

Abstract

The invention relates to a multi-user user selection method based on a matrix condition number in a multiple input multiple output (MIMO) system. The method includes the following steps that S1 precoding is conducted on an original symbol in a precoding matrix to obtain a transmission symbol; S2 a transmitting end receives information channel vector fed back by a user and improves an algorithm by utilizing semi-orthogonality based on the matrix condition number to conduct user selection, each iteration selects a user index, the user index meets the condition that the norm squared value of the information channel vector F is the largest or the matrix condition number is the smallest to obtain the user set with best performance to form a radio frequency link and transmit the transmission symbol. Compared with the prior art, the method has the advantages of transmitting end equipower distribution, limited dynamic change range and capability in hardware pressure reduction. The method is better than the traditional algorithm and capable of selecting the users with orthogonality and reducing interference between the users.

Description

User choosing method based on matrix conditional number in multi-user MIMO system

Technical field

The multi-user installation dispatching technique field that the present invention relates to wireless communication field, especially relates to the user choosing method based on matrix conditional number in a kind of multi-user MIMO system.

Background technology

Nowadays, MIMO (Multiple-Input Multiple-Output, multiple-input and multiple-output) technology used in increasing wireless communication system, in: 3GPP Long Term Evolution (LTE), 4G or even up-to-date 5G cellulor network.In multiuser MIMO broadcast channel, the base station and k the mobile subscriber (User1...UserK) with multiple receive antenna that possess m transmit antennas (m antennas) communicate, as shown in Figure 1, base station user selects after (User Selection), signal forms (ZFBF) or Zero-Force DPC (ZFDPC) coding through broken zero wave beam, carry out transfer of data by transmitting antenna and reception antenna, user is again by passing through feedback channel (Feedback) to the important channel condition information of base-station transmission (CSI), comprise channel directional information (CDI) and channel quality information (CQI), this system can obtain multi-user diversity gain.Comparing Single User MIMO, there are some intrinsic problems in multiuser MIMO.Transmitting data room to multiple users, because the data of space business's different user are superimposed, the multi-user interference of generation is larger to system and capacity impact.Precoding technique be transmitting terminal before transmitted signal, according to known user's channel condition information, the each user's that will transmit information is carried out to preliminary treatment, the receiver that makes each user is by processing simply the information that can obtain oneself.According to existing research, dpc techniques (DPC) is optimum precoding mode, can under same case, obtain best total rate capacities, and total rate capacities is to weigh the important parameter of a multi-user MIMO system performance, it can estimate the validity of transmitting.But dirty paper code is difficult to be used because the Code And Decode of its high complexity operates in real system.

In multi-user MIMO system, precoding technique can effectively be eliminated multi-user interference, if but the user's that base station is served simultaneously channel relevancy too conference have a strong impact on total rate capacities of system, reasonably user selects to improve total rate capacities of system, can also take into account user's fairness.Therefore, the scheme of some suboptimums is suggested and reduces complexity, as broken zero wave beam forms (ZFBF) and broken zero dirty paper code (ZDPC).Empty point of multiple access scheme can obtain best total rate capacities by selecting suitable weight vectors to avoid the interference of each user's projection as ZFBF and ZFDPC.At present, base station is by obtaining best total rate capacities in conjunction with user's selection algorithm and ZFBF or ZFDPC scheme, be that user selects module can determine selected user's sequence number, and ZFBF or ZFDPC module can select suitable weight to carry out match user, reduce the interference between user as far as possible.But, many times in situation, the selection of weight is difficult to, the people such as Yoo have studied the user's selection algorithm under ZFBF, semi-orthogonal user selection algorithm (SUS) has been proposed, its principle as shown in Figure 2, it can obtain reasonable performance by simple user's selection algorithm, and consider user's fairness, and SUS is more classical user's selection algorithm, in order further to reduce algorithm complex, reasonably to carry out user's selection, reduce the interference between user as far as possible, need to improve SUS algorithm.

Summary of the invention

Object of the present invention is exactly to provide the user choosing method based on matrix conditional number in a kind of multi-user MIMO system in order to overcome the defect that above-mentioned prior art exists, based on a new pre-coding matrix, transmission data are carried out to precoding, improve semi-orthogonal user selection algorithm simultaneously, thereby improve systematic function.

Object of the present invention can be achieved through the following technical solutions:

A user choosing method based on matrix conditional number in multi-user MIMO system, comprises the following steps:

Step S1: establish m transmitting antenna of base station transmitting terminal configuration, receive user and configure single antenna, reception antenna is k, based on pre-coding matrix, original symbol is carried out to precoding processing, obtains transmission symbol;

Described precoding processing concrete steps are:

101: make pre-coding matrix be:

$\hat{H}=h_{\mathrm{iid}}{R}_{\mathrm{Tx}}^{\frac{1}{2}}---\left(1\right)$

Wherein, h _iidthe matrix and the obedience average that are a k × m are that zero variance is 1 independent same distribution, R _txthe matrix of a k × k, and each element r _ijrepresent the relation between antenna: i and j represent the sequence number of antenna, d _ijrepresent the distance between two antennas, λ is the wavelength of subcarrier, J ₀() is zero Bessel function;

102: obtain transmission symbol based on pre-coding matrix, the signal y that user receives is:

$y=\mathrm{Hx}+n=H\left({\hat{H}}^{-1}s\right)+n=\left(H{\hat{H}}^{-1}\right)s+n=\mathrm{\Λs}+n---\left(2\right)$

Wherein, H is channel matrix, s is the original symbol sending, and Λ is that a diagonal matrix and diagonal element are channel gain α, and n is white Gaussian noise;

Step S2: transmitting terminal receives the channel vector h of user feedback _k, the semi-orthogonal user of utilization based on matrix conditional number selects to improve algorithm and carries out user's selection, forms radio frequency link, and sends transmission symbol;

The described semi-orthogonal user based on matrix conditional number selects to improve algorithm concrete steps and is:

201: establish for the user of iterations i selects set, initialization user selects set k is user all in system, the user S set=φ being selected, and φ is empty set;

202: the user index π (i) of selective channel vector F norm squared value maximum, that is:

Wherein g (h _k) be the CQI of feedback, and

203: whether the conditional number of the user's that judgement is selected channel vector satisfies condition:

$\mathrm{cond}\left(\begin{array}{c}\left[\begin{array}{c}{h}_{\mathrm{\&pi;}\left(1\right)}\\ h_{\mathrm{\&pi;}\left(2\right)}\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ h_{\mathrm{\&pi;}\left(i\right)}\end{array}\right]\end{array}\right)<n---\left(4\right)$

Wherein, h _{π (i)}be the channel vector of user index π (i), n is the threshold value of defined terms number, n > 1, if satisfied condition, and S ← S ∪ π (i) so, otherwise, need to again select π (i), that is:

204: user's number of establishing in user's S set is p, if p < is m, upgrade user's set that is:

Wherein, to quantize channel directional information afterwards, and ∈ is semi-orthogonal user's threshold value, and iterations upgrades: i=i+1, and execution step 202, if p=m, S set is selected full m user, and algorithm finishes, and S is the best user's set of performance;

Described semi-orthogonal user's threshold value ∈ value is

Compared with prior art, the present invention has the following advantages:

1) the present invention has designed a pre-coding matrix, and new pre-coding matrix can be simplified the signal of reception, and the constant power of realizing transmitting terminal distributes, and reduces the hardware complexity of base station end transmitting antenna, reduces the pressure of transmitting antenna.

2) the present invention proposes an improvement algorithm of selecting based on semi-orthogonal user, the advantage that improved algorithm not only can utilize semi-orthogonal user to select, also can utilize the advantage of conditional number, thereby can select the user of the orthogonality having had, reduce the interference between user.By simulating, verifying, total rate capacities can exceed traditional algorithm.

Brief description of the drawings

Fig. 1 is the multi-user MIMO system schematic diagram of single antenna;

Fig. 2 is the principle schematic of semi-orthogonal user selection algorithm;

Fig. 3 is schematic flow sheet of the present invention;

Fig. 4 is that Performance Ratio traditional and that improve algorithm is compared with schematic diagram.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.

As shown in Figure 1, a multi-user's mimo system, base station transmitting terminal has m transmitting antenna, and mobile reception user configures single antenna, and reception antenna is k.At transmitting terminal, channel condition information (CSI) is completely known in base station, comprise channel directional information (CDI) and channel quality information (CQI), wherein, the CDI using quantizes, and CQI comprises channel phase or Signal to Interference plus Noise Ratio (SINR), carry out mimo system to carry out selecting based on the user of matrix conditional number, comprise the following steps:

Step S1: based on pre-coding matrix, former transmission symbol is carried out to precoding processing, obtain transmission symbol;

Precoding processing concrete steps are:

101: make pre-coding matrix be:

$\hat{H}=h_{\mathrm{iid}}{R}_{\mathrm{Tx}}^{\frac{1}{2}}---\left(1\right)$

Wherein, h _iidthe matrix and the obedience average that are a k × m are that zero variance is 1 independent same distribution, R _txthe matrix of a k × k, and each element r _ijrepresent the relation between antenna: i and j represent the sequence number of antenna, d _ijrepresent the distance between two antennas, λ is the wavelength of subcarrier, J ₀() is zero Bessel function;

102: obtain transmission symbol based on pre-coding matrix, the signal y that user receives is:

$y=\mathrm{Hx}+n=H\left({\hat{H}}^{-1}s\right)+n=\left(H{\hat{H}}^{-1}\right)s+n=\mathrm{\&Lambda;s}+n---\left(2\right)$

Wherein, H is channel matrix, s is the original symbol sending, and Λ is that a diagonal matrix and diagonal element are channel gain α, and α can determine according to actual channel condition, _nit is white Gaussian noise.

Step S2: transmitting terminal receives the channel vector h of user feedback _k, the semi-orthogonal user of utilization based on matrix conditional number selects to improve algorithm and carries out user's selection, obtains the best user's set of performance, forms radio frequency link, and sends transmission symbol.The principle of semi-orthogonal selection algorithm as shown in Figure 2;

As shown in Figure 3, the semi-orthogonal user based on matrix conditional number selects to improve algorithm concrete steps and is:

201: establish for the user of iterations i selects set, initialization user selects set k is user all in system, the user S set=φ being selected, and φ is empty set;

202: the user index π (i) of selective channel vector F norm squared value maximum, that is:

Wherein g (h _k) be the CQI of feedback, and

203: whether the conditional number of the user's that judgement is selected channel vector satisfies condition:

$\mathrm{cond}\left(\begin{array}{c}\left[\begin{array}{c}{h}_{\mathrm{\&pi;}\left(1\right)}\\ h_{\mathrm{\&pi;}\left(2\right)}\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ h_{\mathrm{\&pi;}\left(i\right)}\end{array}\right]\end{array}\right)<n---\left(4\right)$

Wherein, h _{π (i)}be the channel vector of user index π (i), n is the threshold value of defined terms number, n > 1, and the smaller the better, if satisfied condition, S ← S ∪ π (i) so, otherwise, need to again select π (i), that is:

204: user's number of establishing in user's S set is p, if p < is m, upgrade user's set that is:

Wherein, to quantize channel directional information afterwards, and ∈ is semi-orthogonal user's threshold value, and iterations upgrades: i=i+1, and execution step 202, if p=m, S set is selected full m user, and algorithm finishes, and S is the best user's set of performance.

By emulation comparison, we find that arranging of ∈ and n has a great impact total rate capacities.In general, when time, can obtain best total rate capacities.In addition, the value setting of n should be weighed the relation of orthogonality and total rate capacities, and in the time that conditional number is little, the orthogonality between each user is relatively good, but finds the user who satisfies condition more difficult, thereby affects total rate capacities, and vice versa.

As shown in Figure 4, the semi-orthogonal that is 5 to traditional semi-orthogonal selection algorithm and conditional number selects the performance of improving algorithm to compare, and can find out that algorithm of the present invention improves total rate capacities of whole system.

The above, be only preferred embodiments of the present invention, and the interest field that the present invention advocates is not limited to this.The present invention also has other various embodiments; in the situation that not deviating from spirit of the present invention and essence thereof; those skilled in the art can make according to the present invention various corresponding changes and distortion, but these changes and distortion all should belong to the protection range of the appended claim of the present invention.

Claims (4)

1. the user choosing method based on matrix conditional number in multi-user MIMO system, is characterized in that, comprises the following steps:

Step S1: establish m transmitting antenna of base station transmitting terminal configuration, receive user and configure single antenna, reception antenna is k, based on pre-coding matrix, original symbol is carried out to precoding processing, obtains transmission symbol;

Step S2: transmitting terminal receives the channel vector h of user feedback _k, the semi-orthogonal user of utilization based on matrix conditional number selects to improve algorithm and carries out user's selection, selects the best user's set of performance, forms radio frequency link, and sends transmission symbol.

2. the user choosing method based on matrix conditional number in a kind of multi-user MIMO system according to claim 1, is characterized in that, described precoding processing concrete steps are:

101: make pre-coding matrix be:

$\hat{H}=h_{\mathrm{iid}}{R}_{\mathrm{Tx}}^{\frac{1}{2}}---\left(1\right)$

Wherein, h _iidthe matrix and the obedience average that are a k × m are that zero variance is 1 independent same distribution, can produce at random R _txthe matrix of a k × k, and each element r _ijrepresent the relation between antenna: i and j represent the sequence number of antenna, d _ijrepresent the distance between two antennas, λ is the wavelength of subcarrier, J ₀() is zero Bessel function;

102: obtain transmission symbol based on pre-coding matrix, the signal y that user receives is:

$y=\mathrm{Hx}+n=H\left({\hat{H}}^{-1}s\right)+n=\left(H{\hat{H}}^{-1}\right)s+n=\mathrm{\&Lambda;s}+n---\left(2\right)$

Wherein, H is channel matrix, s is the original symbol sending, and Λ is that a diagonal matrix and diagonal element are channel gain α, and n is white Gaussian noise.

3. the user choosing method based on matrix conditional number in a kind of multi-user MIMO system according to claim 1, is characterized in that, the described semi-orthogonal user based on matrix conditional number selects to improve algorithm concrete steps and is:

201: establish for the user of iterations i selects set, initialization user selects set k is user all in system, the user S set=φ being selected, and φ is empty set;

202: the user index π (i) of selective channel vector F norm squared value maximum, that is:

Wherein g (h _k) be the CQI of feedback, and

203: whether the conditional number of the user's that judgement is selected channel vector satisfies condition:

$\mathrm{cond}\left(\begin{array}{c}\left[\begin{array}{c}{h}_{\mathrm{\&pi;}\left(1\right)}\\ h_{\mathrm{\&pi;}\left(2\right)}\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ h_{\mathrm{\&pi;}\left(i\right)}\end{array}\right]\end{array}\right)<n---\left(4\right)$

Wherein, h _{π (i)}be the channel vector of user index π (i), n is the threshold value of defined terms number, n > 1, if satisfied condition, and S ← S ∪ π (i) so, otherwise, need to again select π (i), that is:

204: user's number of establishing in user's S set is p, if p < is m, upgrade user's set that is:

Wherein, to quantize channel directional information afterwards, and ∈ is semi-orthogonal user's threshold value, and iterations upgrades: i=i+1, and execution step 202, if p=m, S set is selected full m user, and algorithm finishes, and S is the best user's set of performance.

4. the user choosing method based on matrix conditional number in a kind of multi-user MIMO system according to claim 3, is characterized in that, described semi-orthogonal user's threshold value ∈ value is