CN105162505A - Self-adapting precoding method of cellular network downlink based on interference alignment - Google Patents

Abstract

The invention discloses a self-adapting precoding method of a cellular network downlink based on interference alignment. The self-adapting precoding method is based on a bandwidth feedback design of user service demand, a uniform design of channel state information, offline search and storage of a base station cooperative mode, mode match of a service request, a cascaded precoding design and a transmitting power control scheme and the like. In the self-adapting precoding method disclosed by the invention, a novel composite channel is adopted in the channel state information (CSI) feedback design, and compared with the prior art, a half of bandwidth is saved. The method can be used for meeting a variety of rates necessary for users under different service types via less transmitting power in a double-cellular cell full frequency reuse scene.

Description

Based on the cellular network down link self adaption method for precoding of interference alignment

Technical field

The present invention relates to a kind of cellular network down link self adaption method for precoding based on interference alignment, belong to cellular communication system base station physical layer precoding technique field.

Background technology

In recent years, along with the continuous growth of high-speed radiocommunication business, the mobile communication system of a new generation needs to use wider frequency band to provide speed to reach the radio communication service of up to a hundred million for user, and the shortage of frequency spectrum resource is day by day remarkable.The capacity that the partial frequency multiplexing technology that traditional cellular network adopts can reach is very limited.Although can adopt the method reducing radius of society, as microcellulor, the technology such as Pico cell further are improved, but bring new problem.Such as, due to the reduced radius of community, between co-frequency cell, interference problem (ICI) becomes increasingly conspicuous.This controls to propose very large challenge for power.At present along with the evolution of network from 4G to 5G, capacity required every year can be double, within 10 years, improves 1000 times, adopt current technology to be unapproachable.

Be at present adopt with frequently multiplexing for the common recognition of follow-on network in the world, therefore new interference coordination technique is its important content.Traditional interference control technology comprises avoiding of interference, Interference Cancellation etc.Interference avoid requiring prior perception disturb time, the information such as frequency, then channel is carried out orthogonal distribute that realization disturbs avoiding.Ideally can realize the channel utilization of 1 times like this, if but the expense of the links such as consideration perception detection, usually do not reach far away.Interference cancellation techniques is usually used in Multiuser Detection, is first detected by most high reject signal, balances out after then rebuilding from total signal, then detects other strong signal successively.The process complexity of this process is high, and time delay is also larger.

Recent international there is a kind of new interference coordination technique, interference alignment (IA).The core concept of this technology is the co-design that each side participating in coordinating carries out encoding and decoding, reaches the object of the capacity of raising system.For the situation of K to user M antenna, often couple of user can both realize the channel capacity of half.Therefore the progressive capacity of whole system is KM/2.This method has shocked industry.Initial interference alignment techniques, gradually also starts to propose different implementations to user model for K recently in cellular network.

Although IA technology has started studiedly to be applied in cellular network, not yet someone has studied the IA coding and decoding scheme of the bandwidth self-adaption based on user feedback.In the application such as mobile Internet, the business important feature based on data is that bandwidth is different, as simple instant chat only may need less bandwidth, the bandwidth that Video Applications then will be larger.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of cellular network down link self adaption method for precoding based on interference alignment, mobile subscriber is proposed first according to the feature of different business, can feed back its bandwidth needed or speed, base station side realizes the dynamic assignment of bandwidth when carrying out disturbing alignment (IA) cooperative coding.The method can the different business bandwidth request of the multiple mobile subscriber of sweetly disposition, and less transmitting power can be utilized to realize cooperative base station well carry out the multiplexing communication of full rate.

The present invention is for solving the problems of the technologies described above by the following technical solutions:

The invention provides a kind of cellular network down link self adaption method for precoding based on interference alignment, for the cooperation Dual base stations that full rate is multiplexing, it is characterized in that, comprise following concrete steps:

Step 1, self capacity requirement is fed back to corresponding base station by all users in the user area of Dual base stations;

Step 2, each base station, according to the user capacity demand received, distributes the degree of freedom based on interference alignment techniques to each user in respective user area;

Step 3, adopts the power gating matrix Λ of zero forcing algorithm design base station _a, to meet the capacity requirement of all users, be specially:

${\mathrm{\Λ}}_a={\mathrm{\σ}}_n\left(\begin{array}{ccc}\sqrt{2^{c_d^1/d_1}-1}{I}_{d_1}& & \\ & ...& \\ & & \sqrt{2^{c_d^{K_{\mathrm{\α}}}/d_{K_{\mathrm{\α}}}}-1}{I}_{d_{K_{\mathrm{\α}}}}\end{array}\right)$

Wherein, σ _nfor noise power mean-square value, for the capacity requirement of i-th user in the user area that this base station is corresponding, d _ifor the degree of freedom of i-th user in the user area that this base station is corresponding, i=1,2 ..., K _α, K _afor the number of users in the user area that this base station is corresponding, I _kfor k rank unit matrix,

Step 4, base station adopts pre-coding matrix to carry out precoding transmissions to downlink data, and pre-coding matrix is formed by first order encoder matrix and second level encoder matrix cascade, wherein:

First order encoder matrix P _afor d before the unitary matrice P on N rank _arow, d _afor the degree of freedom sum of users all in the user area that this base station is corresponding, N is base station subchannels number;

Second level encoder matrix is:

$B_a={\left[\begin{array}{c}{V}_1{G}_{b1}^{-1}{H}_{a1}{P}_a\\ V_2{G}_{b2}^{-1}{H}_{a2}{P}_a\\ ...\\ V_{K_a}{G}_{{\mathrm{bK}}_a}^{-1}{H}_{{\mathrm{aK}}_a}{P}_a\end{array}\right]}^{-1}$

In formula, for matrix P from d _b+ 1 to d _b+ d _ithe submatrix that row are formed, d _bfor the degree of freedom sum of users all in the user area that cooperative base station is corresponding, T represents transposition; G _bifor the interference channel of i-th cooperative base station that user receives in the user area that this base station is corresponding, for G _biinverse matrix, H _aifor the direct channel that i-th user in this user area receives.

As further prioritization scheme of the present invention, the unitary matrice P on N rank is obtained by singular value decomposition.

As further prioritization scheme of the present invention, when the transmitting power of base station is limited, design power controlling elements are constant to realize transmitting power, are specially:

Power control factor wherein, P ₀transmitting power for base station is limited the conjugate transpose of value, H representing matrix.

As further prioritization scheme of the present invention, at receiving terminal, design receives AF panel matrix to recover data, is specially:

The AF panel matrix of i-th user is: wherein, the conjugate transpose of H representing matrix.

As further prioritization scheme of the present invention, user side adopts 2 bits of encoded to base station feedback self capacity requirement.

The present invention adopts above technical scheme compared with prior art, there is following technique effect: compared with the present invention disturbs alignment scheme with other fixed allocation, this method has the following advantages: (1), when reaching identical capacity, transmitting power reduces greatly; (2) multiple interference alignment pattern is applied, better with the matching degree of user's request; (3) design of channel feedback is ingenious, decreases the feedback quantity of half; (4) feedback error is insensitive, immediately has error also can eliminate presence of intercell interference completely.

Accompanying drawing explanation

Fig. 1 is method flow diagram of the present invention.

Fig. 2 is cooperative base station model.

Fig. 3 disturbs the Capacity Ratio of alignment scheme comparatively with classics.

Fig. 4 disturbs the transmitting power of alignment scheme to compare with classics.

Embodiment

Below in conjunction with accompanying drawing, technical scheme of the present invention is described in further detail:

A kind of cellular network down link self adaption method for precoding based on interference alignment of the present invention, concrete steps as shown in Figure 1, repeat no more herein.

For the base station of two as shown in Figure 2 (A and B) cooperation, consider N number of subchannel, and the downlink cellular link that frequency is entirely multiplexing.Wherein, A respective user region, base station A, B respective user region, base station B.

1) user feedback design

One, user bandwidth demand feedback design

User, according to different Business Natures, feeds back different rate requirement.The speed of different size, feedback after coding.Such as, if the speed grade needed is 10,20,40,80kbps, then can adopt 2 bits of encoded, namely each user will carry out the bandwidth of informing base station oneself needs by 2 bit feedback.

Two, subscriber channel information feed back design

The interference that each user in the A of user area will be subject to from base station B, i.e. interregional interference.For the user in the B of user area, be also like this.For the user of i-th in the A of user area, its direct channel is H _ai, the interference channel that to be also N rank matrix come from base station B is G _bi.Be different from general system, the channel condition information that the present invention proposes to feed back is wherein, for G _biinverse matrix.This Feedback Design can save the backward channel expense of half compared with all feeding back with by two matrixes.

2) the cooperation scheme of base station

One, the degree of freedom off-line search of base station

Cooperative base station system calculates the available degree of freedom according to available resources (number of channels, the number of users etc. in every user area) and preserves.These calculating do not need to carry out at every turn, can off line complete.

Two, pattern matching

After receiving the business demand of mobile subscriber, following for employing criterion is carried out dispatching distribution by base station, namely mates with the permission pattern of interference alignment, is in fact similar to and asks inner product.The business demand of each user is arranged in a vector, and the pattern of the preservation of requirement vector and previous step is carried out relevant matches, and the result of coupling is the degree of freedom that each user is assigned to.Suppose that the degree of freedom that a jth user is assigned to is designated as d _j.

3) Precoding Design

The coding scheme design of base station is tandem type, is namely made up of first order encoder matrix and second level encoder matrix cascade.Wherein, the object of first order encoder matrix eliminates interregional interference, and the object of second level encoder matrix eliminates inter-user interference in one's respective area.

First, find the unitary matrice P on N rank, this obtains by singular value decomposition.

For base station A, first order encoder matrix P _afor d before the unitary matrice P on N rank _arow, d _afor the degree of freedom sum of users all in the A of user area, N is base station subchannels number;

Second level encoder matrix is:

$B_a={\left[\begin{array}{c}{V}_1{G}_{b1}^{-1}{H}_{a1}{P}_a\\ V_2{G}_{b2}^{-1}{H}_{a2}{P}_a\\ ...\\ V_{K_a}{G}_{{\mathrm{bK}}_a}^{-1}{H}_{{\mathrm{aK}}_a}{P}_a\end{array}\right]}^{-1}$

In formula, for matrix P from d _b+ 1 to d _b+ d _ithe submatrix that row are formed, d _bfor the degree of freedom sum of users all in the B of user area, T represents transposition; G _bifor the interference channel of the cooperative base station B that i-th user in the A of user area receives, for G _biinverse matrix, H _aifor the direct channel that i-th user in the A of user area receives.

In like manner for base station B, first order encoder matrix P _bfor d before the unitary matrice P on N rank _brow, d _bfor the degree of freedom sum of users all in the B of user area;

Second level encoder matrix $B_b={\left[\begin{array}{c}{V}_1{G}_{a1}^{-1}{H}_{b1}{P}_b\\ V_2{G}_{a2}^{-1}{H}_{b2}{P}_b\\ ...\\ V_{K_b}{G}_{{\mathrm{aK}}_b}^{-1}{H}_{{\mathrm{bK}}_b}{P}_b\end{array}\right]}^{-1},V_i=P_{*;d_A+1:d_A+d_j}^T,j=1,2,\mathrm{...}{K}_b,$ K _bfor the number of users in the B of user area, P _{*; M:n}for the submatrix that row are formed from m to n of matrix P; G _aifor the interference channel of the cooperative base station A that a jth user in the B of user area receives, for G _aiinverse matrix, H _bifor the direct channel that a jth user in the B of user area receives.

4) scheduling of user capacity

For meeting the capacity requirement of all users, adopt the power gating matrix Λ of zero forcing algorithm design base station _a, be specially:

$A_a={\mathrm{\σ}}_n\left(\begin{array}{ccc}\sqrt{2^{c_d^1/d_1}-1}{I}_{d_1}& & \\ & ...& \\ & & \sqrt{2^{c_d^{K_{\mathrm{\α}}}/d_{K_{\mathrm{\α}}}}-1}{I}_{d_{K_{\mathrm{\α}}}}\end{array}\right)$

Wherein, σ _nfor noise power mean-square value, for the capacity requirement of i-th user in the user area that this base station is corresponding, d _ifor the degree of freedom of i-th user in the user area that this base station is corresponding, i=1,2 ..., K _α, K _afor the number of users in the user area that this base station is corresponding, I _kfor k rank unit matrix,

When the transmitting power of base station is limited, design power controlling elements are constant to realize transmitting power, are specially:

Power control factor wherein, P ₀transmitting power for base station is limited the conjugate transpose of value, H representing matrix.

5) AF panel of receiving terminal

Eliminate the interference between interregional interference and user area intra domain user veritably, need to complete at mobile station side.We devise and receive AF panel matrix to realize this target.At receiving terminal, design receives AF panel matrix, to recover data, is specially:

In the A of user area, the AF panel matrix of i-th user is: wherein, the conjugate transpose of H representing matrix.

Below by concrete simulation result, technical scheme of the present invention is further elaborated:

For analyzing the performance of the cellular system down link self adaption pre-coding scheme that the present invention is based on interference alignment, we disturb alignment algorithm to contrast with classics in simulations: one) meeting under identical capacity requirement with classical interference alignment schemes, the contrast of transmitting power; Two) under transmit power limited condition, the comparison of the final capacity accounting realized.

Simulated conditions is as follows: suppose that the capacity of the user feedback in user area is four grades, according to 2 bit feedback: 5,10,15,20bps.Available subchannels number is 32, and it is the Poisson distribution of 5 that intra-cell users number obeys average.The variance of channel Gaussian noise is 10 ^-3.

As shown in Figures 3 and 4, obviously, compared with disturbing alignment algorithm with classics, the solution of the present invention all has larger advantage to simulation result in transmitting power and capacity.Fig. 3 is the distribution function contrast of the transmitting power of two schemes.Notice that the solution of the present invention is when equal probabilities, transmitting power to be alignd low more than 10dB than classical interference.Fig. 4 is under simulating transmitter power limited situation, the ratio of the final capacity of realization and the capacity of user's request.Be only the condition of 6dB in transmitting power under, the capacity accounting about 93% that the present invention realizes, and the method for classics only achieves the capacity less than 25%.

The above; be only the embodiment in the present invention; but protection scope of the present invention is not limited thereto; any people being familiar with this technology is in the technical scope disclosed by the present invention; the conversion or replacement expected can be understood; all should be encompassed in and of the present inventionly comprise within scope, therefore, protection scope of the present invention should be as the criterion with the protection range of claims.

Claims (5)

1., based on the cellular network down link self adaption method for precoding of interference alignment, for the cooperation Dual base stations that full rate is multiplexing, it is characterized in that, comprise following concrete steps:

Step 1, self capacity requirement is fed back to corresponding base station by all users in the user area of Dual base stations;

Step 2, each base station, according to the user capacity demand received, distributes the degree of freedom based on interference alignment techniques to each user in respective user area;

Step 3, adopts the power gating matrix Λ of zero forcing algorithm design base station _a, to meet the capacity requirement of all users, be specially:

${\mathrm{\Λ}}_a={\mathrm{\σ}}_n\left(\begin{array}{ccc}\sqrt{2^{c_d^1/d_1}-1}{I}_{d_1}& & \\ & ...& \\ & & \sqrt{2^{c_d^{K_{\mathrm{\α}}}/d_{K_{\mathrm{\α}}}}-1}{I}_{d_{K_{\mathrm{\α}}}}\end{array}\right)$

Wherein, σ _nfor noise power mean-square value, for the capacity requirement of i-th user in the user area that this base station is corresponding, d _ifor the degree of freedom of i-th user in the user area that this base station is corresponding, i=1,2 ..., K _α, K _afor the number of users in the user area that this base station is corresponding, I _kfor k rank unit matrix, k=d ₁..., d _{k α};

Step 4, base station adopts pre-coding matrix to carry out precoding transmissions to downlink data, and pre-coding matrix is formed by first order encoder matrix and second level encoder matrix cascade, wherein:

First order encoder matrix P _afor d before the unitary matrice P on N rank _arow, d _afor the degree of freedom sum of users all in the user area that this base station is corresponding, N is base station subchannels number;

Second level encoder matrix is:

$B_a={\left[\begin{array}{c}{V}_1{G}_{b1}^{-1}{H}_{a1}{P}_a\\ V_2{G}_{b2}^{-1}{H}_{a2}{P}_a\\ ...\\ V_{K_a}{G}_{{\mathrm{bK}}_a}^{-1}{H}_{{\mathrm{aK}}_a}{P}_a\end{array}\right]}^{-1}$

In formula, for matrix P from d _b+ 1 to d _b+ d _ithe submatrix that row are formed, d _bfor the degree of freedom sum of users all in the user area that cooperative base station is corresponding, T represents transposition; G _bifor the interference channel of i-th cooperative base station that user receives in the user area that this base station is corresponding, for G _biinverse matrix, H _aifor the direct channel that i-th user in this user area receives.

2. the cellular network down link self adaption method for precoding based on interference alignment according to claim 1, it is characterized in that, the unitary matrice P on N rank is obtained by singular value decomposition.

3. the cellular network down link self adaption method for precoding based on interference alignment according to claim 1, it is characterized in that, when the transmitting power of base station is limited, design power controlling elements are constant to realize transmitting power, are specially:

Power control factor wherein, P ₀transmitting power for base station is limited the conjugate transpose of value, H representing matrix.

4. the cellular network down link self adaption method for precoding based on interference alignment according to claim 1, is characterized in that, at receiving terminal, design receives AF panel matrix to recover data, is specially:

The AF panel matrix of i-th user is: wherein, the conjugate transpose of H representing matrix.

5. the cellular network down link self adaption method for precoding based on interference alignment according to claim 1, it is characterized in that, user side adopts 2 bits of encoded to base station feedback self capacity requirement.