CN104702328A - Cognition MIMO system user scheduling method based on interference alignment - Google Patents

Abstract

A cognition MIMO system user scheduling method based on interference alignment comprises the steps that 1. an authorization user, a cognition user and a base station obtain needed channel information; 2. the authorization user, the base station and the cognition user carry out singular value decomposition on H0, and H0 represents a channel matrix between the cognition user and the base station; 3. the cognition user determines the number m0 of space component channels according to channel conditions, the information is reported to the base station, the cognition user monitors the using condition m0 of the component channels of the authorization user, a non-normalized precoding matrix Pi of the cognition user and the norm || Pi || thereof are computed, and || Pi || is sent to the base station; 4. the base station compares || Pi ||, and a cognition user number xi is obtained; 5. the authorization user constructs a precoding matrix P0, and the base station sends activation signals to the cognition user which needs to be scheduled; 6. the cognition user which receives the activation signals carries out unitization on each line of Pxi, and P'xi is obtained; and 7. the authorization user and the activated cognition user are subjected to P0 and P'xi preprocessing respectively, and signals are sent to the base station.

Description

A kind of cognitive mimo system user scheduling method based on interference alignment

[technical field]

The present invention relates to a kind of cognitive mimo system user scheduling method based on interference alignment.

[background technology]

Along with the fast development of wireless communication system, radio spectrum resources is as a kind of non-renewable resources, and its rare characteristic is obvious all the more.Fixing spectrum allocation may policy result in the frequency spectrum resource that can license to new application, and there is a serious shortage in the supply, significantly limit the development of radio communication.Now, people start emphasis to come from seeking new idle frequency spectrum resource transfers to the raising availability of frequency spectrum.Cognitive radio (Cognitive radio), as a kind of technology improving the availability of frequency spectrum, becomes the focus of research.The transmission of cognitive user do not affect authorized user transmission or to the interference of authorized user transmission lower than certain thresholding time, this technology allows cognitive user dynamic access authorized user frequency spectrum.

Along with going deep into of research, people start the possibility of attempting excavating communication from multiple dimension, and spatial domain resource is one of them importance.Multiple-input and multiple-output (Multi-inputmulti-output, MIMO) technology is a disruptive technology of wireless communication field in recent years, and this technology can make spatial domain resource be fully used.Cognitive radio technology combines with MIMO technology and studies by researcher, transmits by cognitive signal and authorization signal being placed in mutually orthogonal subspace, thus ensure that mandate business and cognitive business is noiseless in spatial domain coexists.Interference alignment (Interference alignment) technology is just based on a kind of modular design of above-mentioned thought.

In the correlative study occurred in recent years, PERLAZA S M, DEBBAH M, LASAULCE S, CHAUFRAY J-M.Opportunistic Interference Alignmentin MIMO Interference Channel [A] .Proceedings of IEEE 19thInternational Symposium on Personal, Indoor and Mobile RadioCommunications [C], Cannes, France, the system that 2008.1-5 mono-literary composition is studied is only containing a pair cognitive transceiver, do not consider many cognitive user scene, AMIR M, EL-KEYI A, NAFIE M.Constrained Interference Alignment and the Spatial Degreesof Freedom of MIMO Cognitive Network [J] .IEEE Transaction onInformation Theory, 2011, 57 (5): although the cognitive system that 2994-3004 mono-literary composition is studied comprises multipair transceiver, but scene is more suitable for distributed network.For the cell mobile communication systems of center type, base station, simultaneously to multiple Terminal for service, therefore, necessitates to the research of cognitive MIMO application in downlink broadcast communication and uplink multi-address access.Document KRIKIDIS I.A SVD-Based Location Coding for Cognitive Radio inMIMO Uplink Channels [J] .IEEE Communications Letters, 2010,14 (10): the 912-914 thoughts of aliging based on interference, have studied the ascending communication system be made up of a base station, an authorized user and a cognitive user, this research still comes with some shortcomings, as do not studied more general many cognitive user scene; Require too high to the cognitive ability of cognitive user, in frequency domain perception, can not only also want the using state etc. of aware space subchannel.

[summary of the invention]

The object of the present invention is to provide a kind of cognitive mimo system user scheduling method based on interference alignment, it comprises the steps:

(1) authorized user and base station obtain the channel matrix between authorized user and base station respectively, and cognitive user obtains the channel matrix between authorized user and base station, between cognitive user and base station, wherein H ₀for representing channel matrix, the H between authorized user and base station _irepresent the channel matrix between cognitive user and base station;

(2) authorized user, base station and cognitive user all do singular value decomposition to the channel matrix between authorized user and base station;

(3) authorized user determines the number of the spatial sub-channel used according to channel status, and circulates a notice of to base station by the number of the spatial sub-channel of described use, and cognitive user is monitored authorized user spatial sub-channel and used number m ₀, calculate not normalized pre-coding matrix P separately _i, then calculate described pre-coding matrix P _inorm, and the norm calculated is sent to base station;

(4) norm received is compared in base station, obtains the cognitive user numbering ξ that should dispatch;

(5) authorized user constructs pre-coding matrix P ₀, activation signal is sent to the cognitive user that should dispatch by base station;

(6) the pre-coding matrix P of cognitive user to the cognitive user of numbering ξ of activation signal is received _ξoften row carry out unitization and obtain activating cognitive user normalized pre-coding matrix P ' _ξ;

(7) authorized user and activation cognitive user are respectively through P ₀with P ' _ξpreliminary treatment, send signal to base station, base station carries out accepting filter obtaining signal.

On the basis of technique scheme, described step (2) comprising:

Authorized user, base station and cognitive user are all to H ₀do singular value decomposition, namely

$H_0=U_0{\mathrm{\Λ}}_0{V}_0^H,---\left(1\right)$

Wherein () ^Ηrepresent conjugate transpose, U ₀and V ₀row reflect the space characteristics that corresponding system channel is equivalent to decoupling subchannel, Λ ₀be the elements in a main diagonal be nonnegative real number, all the other elements are the matrix of zero entirely, and the transmission gain of the corresponding decoupling subchannel of the element representation of its leading diagonal, descending, namely n _rfor base station end antenna number.

On the basis of technique scheme, in described step (3), calculate not normalized pre-coding matrix P separately _icomputational methods be,

$P_i={\left(H_i\right)}^{-1}{\hat{U}}_0.---\left(2\right)$

On the basis of technique scheme, described step (6) comprise receive activation signal cognitive user to its pre-coding matrix P _ξin often row carry out unitization,

${\stackrel{\‾}{p}}_{\mathrm{\ξ},j}=\frac{p_{\mathrm{\ξ},j}}{\left|\right|p_{\mathrm{\ξ},j}\left|\right|},j=\mathrm{1,2},...N_R-m_0,---\left(3\right)$

$P_{\mathrm{\ξ}}^{\′}=[{\stackrel{\‾}{p}}_{\mathrm{\ξ},1},{\stackrel{\‾}{p}}_{\mathrm{\ξ},2},...{\stackrel{\‾}{p}}_{\mathrm{\ξ},N_R-m_0}],---\left(4\right)$

Obtain P ' _ξ, wherein represent the precoding vector obtained through normalized formula (3) Suo Shi, P ' _ξrepresent and activate the normalized pre-coding matrix of cognitive user.

Compared with prior art, contemplated by the invention the sight of many cognitive user, and the method for solving of pre-coding matrix is reasonably devised based on interference alignment thought, achieve mandate business and the noiseless of cognitive business coexists, and rational scheduling has been carried out to cognitive user, significantly improve cognitive communications systematic function.

[accompanying drawing explanation]

Fig. 1 is the system model of uplink communication of the present invention;

Fig. 2 is that pre-coding matrix of the present invention solves the particular flow sheet with user scheduling;

Fig. 3 is cognitive user number K=4 of the present invention, antenna number time the simulation curve figure that changes with signal to noise ratio snr of system average throughput;

Fig. 4 is cognitive user number K=2 of the present invention, 4,8,12,16, the simulation curve figure that during antenna number N=4, system average throughput changes with SNR.

[embodiment]

Below in conjunction with specific embodiment, the present invention is described in detail.

With reference to Fig. 1, the present invention studies the uplink communication that mandate business coexists with cognitive business, and cognitive and authoring system all adopts MIMO technology.This system comprises a base station, an authorized user and multiple cognitive user.For easy, all do not draw multiple antennas in cognitive and authoring system sending and receiving end.Antenna for base station number is N _r, authorized user antenna number is N _t0, cognitive user antenna number is N _ti(i=1,2 ... K), i represents i-th cognitive user, 1≤i≤K.In the drawings, authorization data transmission indicated by the solid line, cognitive transfer of data represented by dashed line, and the symbol that every bar line marks represents corresponding channel matrix.

With reference to Fig. 2, the cognitive mimo system pre-coding matrix based on interference alignment of the present invention's design solves and user scheduling method, specifically comprises the steps:

(1) PU obtains channel information H ₀, BS obtains channel information H ₀, CU _i(i=1,2 ... K) obtain channel information H ₀, H _i.Wherein H ₀, H _irepresent PU and BS, CU respectively _iwith the channel matrix of BS;

(2) PU, BS and CU _i(i=1,2 ... K) all to H ₀do singular value decomposition, namely

$H_0=U_0{\mathrm{\Λ}}_0{V}_0^H,$

Wherein () ^Ηrepresent conjugate transpose, U ₀and V ₀row reflect the space characteristics that corresponding system channel is equivalent to decoupling subchannel, Λ ₀be the elements in a main diagonal be nonnegative real number, all the other elements are the matrix of zero entirely, and the transmission gain of the corresponding decoupling subchannel of the element representation of its leading diagonal, descending, namely n _rfor BS holds antenna number;

(3) PU determines the number m of the spatial sub-channel used according to channel status ₀, and by this communication to BS.CU _i(i=1,2 ... K) monitor authorized user spatial sub-channel use number m ₀, calculate not normalized pre-coding matrix P separately _i,

$P_i={\left(H_i\right)}^{-1}{\hat{U}}_0,$

Calculate its norm again || P _i||, and will || P _i|| send to BS;

(4) BS compares || P _i||, calculate the cognitive user numbering ξ that should dispatch,

$\mathrm{\ξ}=\underset{1\≤i\≤K}{\arg }\min \left|\right|P_i\left|\right|=\underset{1\≤i\≤K}{\arg \min }\left|\right|{\left(H_i\right)}^{-1}{\hat{U}}_0\left|\right|;$

(5) PU constructs pre-coding matrix P ₀, activation signal is sent to CU by BS _ξ;

(6) cognitive user of activation signal is received to its pre-coding matrix P _ξin often row carry out unitization,

${\stackrel{\‾}{p}}_{\mathrm{\ξ},j}=\frac{p_{\mathrm{\ξ},j}}{\left|\right|p_{\mathrm{\ξ},j}\left|\right|},j=\mathrm{1,2},...N_R-m_0,$

$P_{\mathrm{\ξ}}^{\′}=[{\stackrel{\‾}{p}}_{\mathrm{\ξ},1},{\stackrel{\‾}{p}}_{\mathrm{\ξ},2},...{\stackrel{\‾}{p}}_{\mathrm{\ξ},N_R-m_0}],$

Obtain P ' _ξ, wherein represent the precoding vector obtained through normalized, P ' _ξrepresent and activate the normalized pre-coding matrix of cognitive user;

(7) authorized user and activation cognitive user are respectively through P ₀with P ' _ξpreliminary treatment, sends signal to base station, and base station utilizes the signal that carrying out accepts filter obtains as shown in the formula:

$\begin{array}{c}\stackrel{\‾}{y}=\left[\begin{array}{c}\tilde{y}\\ \hat{y}\end{array}\right]=U_0^H{H}_0{P}_0{x}_0+U_0^H{H}_{\mathrm{\ξ}}{P}_{\mathrm{\ξ}}^{\′}{x}_{\mathrm{\ξ}}+U_0^{H}n\\ ={\widetilde{\mathrm{\Λ}}}_0{x}_0+\left[\begin{array}{c}{0}_{m_0}\\ {\hat{U}}_0^H{H}_{\mathrm{\ξ}}{P}_{\mathrm{\ξ}}^{\′}{x}_{\mathrm{\ξ}}\end{array}\right]+U_0^{H}n\end{array},$

Wherein with be respectively the signal of authorized user and the transmission of activation cognitive user, order ${\mathrm{\Λ}}_0=\left[\begin{array}{cc}{\widetilde{\mathrm{\Λ}}}_0& {\widehat{\mathrm{\Λ}}}_0\end{array}\right],$ with nonzero element represent respectively authorized user and activate cognitive user use subchannel gains, order $U_0=\left[\begin{array}{cc}{\tilde{U}}_0& {\hat{U}}_0\end{array}\right],$ with each row represent authorized user respectively and activate the space characteristics of subchannel that cognitive user uses, x ₀and x _ξrepresent the symbolic vector that authorized user and activation cognitive user send respectively, n represents additive white Gaussian noise, and the variance of noise component(s) is represent m ₀× m ₀zero gust.

[emulation experiment]

Effect of the present invention, further illustrates by following emulation:

Simulated conditions: antenna number N _r=N _t0=N _ti=N (i=1,2 ... K), the transmitting power of cognitive user and authorized user is P _t.

Fig. 3 provides cognitive user number K=4, antenna number N=2, and 4,6,8, the simulation curve figure that system average throughput changes with signal to noise ratio snr, and compare with the reference method of the user scheduling not considering cognitive user transmission performance difference.Authoring system throughput formula is as follows

$\tilde{R}=\mathrm{lb}\left\{\det \right[I_N+\frac{P_T{\widetilde{\mathrm{\Λ}}}_0{\widetilde{\mathrm{\Λ}}}_0^H}{m_0{\mathrm{\σ}}_n^2{I}_N}\left]\right\}=\underset{l=1}{\overset{m_0}{\mathrm{\Σ}}}\mathrm{lb}\{1+\frac{P_T{\mathrm{\λ}}_l^2}{m_0{\mathrm{\σ}}_n^2}\}---\left(7\right)$

Cognitive system throughput formula is as follows

$\hat{R}=\mathrm{lb}\left\{\det \right[I_N+\frac{P_T\left(U_0^H{H}_{\mathrm{\ξ}}{P}_{\mathrm{\ξ}}^{\′}\right){\left(U_0^H{H}_{\mathrm{\ξ}}{P}_{\mathrm{\ξ}}^{\′}\right)}^H}{(N-m_0){\mathrm{\σ}}_n^2{I}_N}\left]\right\}---\left(8\right)$

I _nrepresent N × N unit matrix, H _ξrepresent the channel matrix activated between cognitive user ξ and base station, the logarithm that it is the end with 2 that lb () represents, determinant of a matrix is asked in det () expression.

As can be seen from the figure, for authoring system, throughput increases with the increase of SNR.For cognitive system, at low SNR place, throughput is low.Along with the increase of SNR, cognitive system throughput improves gradually.When SNR increases to a certain degree, declining appears in cognitive system throughput.Because method therefor of the present invention utilizes the difference of different cognitive users transmission performance to realize scheduling, reference method carries out indifference process to all cognitive communications channels, adopts random schedule mode.Therefore method throughput of the present invention is obviously better than reference method.

Fig. 4 gives cognitive user number K=2, and 4,8,12,16, antenna number N=4, the simulation curve figure that system average throughput changes with SNR, and compare with the reference method of the user scheduling not considering cognitive user transmission performance difference.As can be seen from the figure, the throughput of method of the present invention is better than reference method, and makes moderate progress along with the increase performance of cognitive user number.

Should be understood that, for those of ordinary skills, can be improved according to the above description or convert, and all these improve and convert the protection range that all should belong to claims of the present invention.

Claims (4)

1., based on a cognitive mimo system user scheduling method for interference alignment, it is characterized in that: it comprises the steps:

(1) authorized user and base station obtain the channel matrix between authorized user and base station respectively, and cognitive user obtains the channel matrix between authorized user and base station, between cognitive user and base station, wherein H ₀for representing channel matrix, the H between authorized user and base station _irepresent the channel matrix between cognitive user and base station;

(2) authorized user, base station and cognitive user all do singular value decomposition to the channel matrix between authorized user and base station;

(3) authorized user determines the number of the spatial sub-channel used according to channel status, and circulates a notice of to base station by the number of the spatial sub-channel of described use, and cognitive user is monitored authorized user spatial sub-channel and used number m ₀, calculate not normalized pre-coding matrix P separately _i, then calculate described pre-coding matrix P _inorm || P _i||, and the norm calculated is sent to base station;

(4) norm received is compared in base station, obtains the cognitive user numbering ξ that should dispatch, wherein list show the space characteristics of subchannel activating cognitive user and use,

(5) authorized user constructs pre-coding matrix P ₀, activation signal is sent to the cognitive user that should dispatch by base station;

(6) the pre-coding matrix P of cognitive user to the cognitive user of numbering ξ of activation signal is received _ξoften row carry out unitization and obtain activating cognitive user normalized pre-coding matrix P ' _ξ;

(7) authorized user and activation cognitive user are respectively through P ₀with P ' _ξpreliminary treatment, send signal to base station, base station carries out accepting filter obtaining signal.

2. a kind of based on disturbing the cognitive mimo system user scheduling method alignd as claimed in claim 1, it is characterized in that, described step (2) comprising:

Authorized user, base station and cognitive user are all to H ₀do singular value decomposition, namely

Wherein () ^Ηrepresent conjugate transpose, U ₀and V ₀row reflect the space characteristics that corresponding system channel is equivalent to decoupling subchannel, Λ ₀be the elements in a main diagonal be nonnegative real number, all the other elements are the matrix of zero entirely, and the transmission gain of the corresponding decoupling subchannel of the element representation of its leading diagonal, descending, namely n _rfor base station end antenna number.

3. a kind of based on disturbing the cognitive mimo system user scheduling method alignd as claimed in claim 1, it is characterized in that: in described step (3), calculate not normalized pre-coding matrix P separately _icomputational methods be,

。

4. as claimed in claim 1 a kind of based on interference alignment cognitive mimo system user scheduling method, it is characterized in that: described step (6) comprise receive activation signal cognitive user to its pre-coding matrix P _ξin often row carry out unitization,

Obtain P ' _ξ, wherein represent the precoding vector obtained through normalized formula (3) Suo Shi, P ' _ξrepresent and activate the normalized pre-coding matrix of cognitive user.