CN104184689B - The blind interference alignment method of SISO systems - Google Patents

The blind interference alignment method of SISO systems Download PDF

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CN104184689B
CN104184689B CN201410404642.8A CN201410404642A CN104184689B CN 104184689 B CN104184689 B CN 104184689B CN 201410404642 A CN201410404642 A CN 201410404642A CN 104184689 B CN104184689 B CN 104184689B
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interference
channel
information
interference alignment
blind
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CN104184689A (en
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李强
王平
吴彩凤
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University of Electronic Science and Technology of China
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University of Electronic Science and Technology of China
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Abstract

The invention discloses a kind of blind interference alignment method of SISO system interferences channel.First with the design of asymmetric complex signal, add the dimension of signal space, efficiently solve single antenna restricted problem, then receiving terminal realizes that interference is completely eliminated using channel information and precoding vector information design wave filter, and demonstrate transmitting terminal design precoding vectors need not know channel information, so as to realize blind interference alignment.In addition, present invention demonstrates that the degree of freedom in system of K user's interference channel reaches K/2, this is also the upper limit of degree of freedom in system when known to transmitting end channel status information simultaneously.Blind interference alignment method proposed by the present invention, can effectively solve the problems, such as in real system that signal space dimension is not high enough and perfect channel condition information obtains difficult, and effectively eliminate system interference, improve handling capacity.

Description

The blind interference alignment method of SISO systems
Technical field
The invention belongs to mobile communication technology field, and in particular to one kind can effectively improve interference network capacity, will disturb The method being completely eliminated.
Background technology
With the fast development of radio communication, terminal user's quantity of wireless network steeply rises, and is communicated along with influence The principal element of quality is interference and Capacity.In a wireless communication system, useful signal in communication process by dry The influence disturbed declines the communication quality of system.In order to improve power system capacity, interference eliminates or suppresses to disturb non-as one Often important research topic.
Interference alignment (Interference Alignment, IA) technology can effectively improve the capacity of interference network, improve Wired and throughput of wireless networks limitation problem in traditional approach, its core concept be interference signal is compressed to it is as small as possible In interference space, useful signal is transmitted under the conditions of glitch-free to reserve more spaces.In the ideal case, such as global letter Road information, unlimited resolution ratio and bandwidth, high signal intensity and delay etc., it is free that interference alignment can provide optimal channel Degree.
However, in single-input single-output (Single-Input Single-Output, SISO) system, interference pair is realized Face the problem of signal space dimension is not high enough together.Therefore, increase signal space dimension is effective core for realizing interference alignment One of technology.Syed A.Jafar,Blind Interference Alignment,IEEE Journal of Selected Topics in Signal Processing,Vol.6,NO.3,June2012,pp.216-227.Ye Tian,Aylin Yener,Guiding Blind Transmitters:Relay-aided Interference Alignment for the X channel,IEEE International Symposium on Information Theory Proceedings,2012, The two documents of pp.1513-1517 show that by sign extended or relaying auxiliary signal space dimension can be effectively increased, real Now interference alignment, but these methods reduce the utilization rate of resource, and have certain requirement to channel status.
In practical communication system, transmitting terminal obtains perfect channel condition information (channel state information At transmitters, CSIT) it is extremely difficult.In order to weaken its limitation, Tiangao Gou, Chenwei Wang, and Syed A.Jafar.,Aiming Perfectly in the Dark-Blind Interference Alignment Through Staggered Antenna Switching,IEEE Trans.Sinal Processing,Vol.59,NO.6, June2011,pp.2734-2744.Qing F.Zhou,Q.T.Zhang On Blind Interference Alignment over Homogeneous Block Fading Channels,IEEE Communications Letters,Vol.16, NO.9, September2012, pp.1432-1435, existing document, which is mentioned, realizes blind interference alignment, but is using above-mentioned blind interference , it is necessary to which receiving terminal takes some special shapes during alignment, realization interference alignment, complexity are switched over by traveling through all patterns Height, and the blind interference alignment in SISO systems can not be realized.
The content of the invention
The present invention is in order to solve the deficiencies in the prior art, there is provided a kind of blind interference alignment side of SISO systems Method, comprise the following steps that：
S1, virtual multi-antenna channel model is established, be specially：Single antenna is configured in all nodes, is sent in transmitting terminal multiple Signal data, user i reception signal areTo ensure to disturb aligned signal space, profit It is related to asymmetric complex signal, user i reception signal can be rewritten asIts In, yi=[Re { yi} Im{yi}]T, ni=[Re { ni} Im{ni}]T, ()TThe transposition of vector is represented, Re { } represents complex signal Real part, Im { } represent the imaginary part of complex signal, and channel coefficients are defined as Hij=| hij|J(θij),θij=∠ hij, transmitting terminal i signal is xi=visi, wherein, vi∈R2×1It is precoding vector, | |vi||2≤ P is that each base station power limits, siIt is scalar data；
S2, interference processing is carried out to receiving terminal, be specially：If the precoding vectors v of transmitting terminali=[cos αi sinαi]T, The filter vector of receiving terminal is ui=[cos φi -sinφi], receiving terminal i reception signal isReceiving terminal uses filter vector uiHandled, so as to Interference is handled
S3, by non trivial solution analytical proof transmitting terminal design precoding vectors need not know channel information；
Interference is completely eliminated for S4, acquisition least interference equation, wherein, least interference equation isθj, j ∈ 1,2 ... and .K } represent channel information, αjRepresent precoding vector Information, φiExpression receiving terminal i filter vector information, j ∈ 1,2 ... .K }；
S5, carry out blind interference alignment：If αj, j ∈ 1,2 ... and .K } it is variable, precoding vector can be believed according to channel status Breath changes, and because each equation has a K variable, a total of 2K variable in K equation, solution is much organized so as to exist.Institute There is the optimal solution found out in solution and maximize SINR, complexity can be higher.If αj, j ∈ 1,2 ... and .K } it is to immobilize, i.e. Precoding vector is not influenceed by channel condition information.Therefore, transmitting terminal can predefine it in Unknown Channel information and prelist Code vector, receiving terminal and transmitting terminal can be communicated by predefined precoding vector.That is, transmitting terminal is not knowing channel Non-zero precoding vector is determined in the case of state, realizes blind interference alignment.Therefore, there was only a variable in an equation, often Individual equation has solution, and interference is completely eliminated, so as to obtain the disturbance equation of system： Solve its equation, it is assumed that Then disturbance equation can be simplified to λ cos (φi)-βsin(φi)=0, so as to right Non trivial solution is analyzed, and is rationally designed and is received end filter.That is, receiving terminal can pass through channel information and precoding vector information Its interference is completely eliminated in design ZF filter vector.It is unrelated with channel condition information because precoding vector is fixed, realize blind Interference alignment.
S6：Degree of freedom in system is obtained according to the definition of the free degree, is specially：The definition of the free degree： Wherein, R(i)(ρ) represents speed of the user i obtained by SNR ρ, unit bps/Hz.It can be carried out for each user completely dry Disturb elimination, it is not necessary to which sign extended or relaying auxiliary, whole system can reach the K/2 frees degree, while be also that transmitting terminal is complete The free degree upper limit of channel condition information is known, so as to be also the free degree upper limit of blind transmitting terminal
The beneficial effects of the invention are as follows：
The present invention proposes a kind of blind interference alignment method of SISO system interferences channel.Utilize setting for asymmetric complex signal Meter, virtual multi-antenna system model is established, increase signal space dimension, effectively solve single antenna restricted problem.Then receiving terminal Realize that interference is completely eliminated using channel information and precoding vector information design wave filter, and analytical proof transmitting terminal design Precoding vectors need not know channel information, so as to realize the blind interference alignment of SISO systems.In addition, the present invention demonstrates K The degree of freedom in system of user's interference channel reaches K/2, while degree of freedom in system when being also transmitting terminal known channel state information The upper limit.Blind interference alignment method proposed by the present invention, it is not high enough and complete can effectively to solve signal space dimension in real system U.S. channel condition information obtains the problem of difficult, and effectively eliminates system interference, improves handling capacity.
Brief description of the drawings
Fig. 1 is the system model schematic diagram that the present invention uses.
Embodiment
With reference to embodiment and accompanying drawing, technical scheme is described in detail.
In the present invention, the data of transmission are complex signals.The data of transmission flow through the design of asymmetric complex signal, channel mould Type may be considered virtual multi-antenna system, solve single antenna restricted problem.If receiving terminal targeted customer i reception signal represents Into:
To ensure the signal space of interference alignment, using the design of asymmetric complex signal, signal is rewritable to be：
Wherein：yi=[Re { yi} Im{yi}]T, xi=[Re { xi} Im{xi}]T, ni=[Re { ni} Im{ni}]T, ()TTable Show the transposition of vector, xiRepresent user i transmission signal.Re { } represents the real part of complex signal, and Im { } represents complex signal Imaginary part.Channel coefficients are defined as:
Hij=| hij|J(θij) (3)
Wherein：HijRepresent channel interference informations of the interference user j to targeted customer i.
That is, J (θ) can be defined asθij=∠ hij.Therefore, channel model may be considered Virtual multi-antenna system, wherein, transmitting terminal and receiving terminal configure two antennas.So as to which increase exceptional space, which is used to disturb, to align. Designing user i transmission signal is xi=visi, wherein, vi∈R2×1It is precoding vector, | | vi||2≤ P is each base station power Limitation, siIt is scalar data.
Assuming that the precoding vectors v of signali=[cos αi sinαi]T, ui=[cos φi -sinφi] be receiving terminal filter Ripple device vector, so as to which the targeted customer i of receiving terminal reception signal can be expressed as
Receiving terminal uses filter vector u for targeted customer iiHandled, so as to which the signal after handling is expressed as
All interference are disturbed or eliminate to reduce to greatest extent, i.e. distracter elimination or minimum by formula (5), therefore, Need to meet
Wherein, θj, j ∈ 1,2 ... and .K } represent channel information, αj, j ∈ 1,2 ... and .K } represent that interference user j's is pre- Code vector information, φiThe targeted customer i of receiving terminal filter vector information is represented, the situation analysis of the solution of formula (6) is such as Under：
If precoding vector can change according to channel condition information, i.e. interference user j precoding vector information αj,j ∈ 1,2 ... and .K } it is variable.Therefore, precoding vector is relevant with channel condition information.Because each equation has K variable, K A total of 2K variable in individual equation, solved so as to many groups be present.Because channel phase information and precoding vector information It is scalar data, so only real solution can meet to require.If without real solution, minimum interference solution can be looked for.If Many real solutions, i.e. interference can be completely eliminated in receiving terminal, and the optimal solution for maximizing SINR, but complexity are found out in all solutions Compare high.
If αj, j ∈ 1,2 ... and .K } it is to immobilize, i.e. and precoding vector is not influenceed by channel condition information.Cause This, transmitting terminal can predefine its precoding vector in Unknown Channel information, and receiving terminal and transmitting terminal can be by predefined Precoding vector communicated.To sum up, transmitting terminal determines non-zero precoding vector in the case where not knowing channel status, real Existing blind interference alignment.According to there was only a variable in (6) equatioies of formula, each equation has solution.If it is complex roots, can only Minimum interference solution is found out, otherwise, in the case of blind interference alignment, interference can be completely eliminated.
Discussion more than, to reduce complexity, it is assumed that αj, j ∈ 1,2 ... and .K } it is to immobilize, blind transmitting terminal The precoding of non-zero is determined in the case of unknown channel state.Receiving terminal is carried out to targeted customer i using filter vector Interference eliminates, i.e. formula (6) is expressed as
Assuming that
Then equation (7) can simplify to obtain
λcos(φi)-βsin(φi)=0 (8)
Non trivial solution is analyzed as follows：
If 1) λ=0, β=0, then φiIt can be arbitrary value；
If 2) λ ≠ 0, β=0, thenK=0,1,2 ...；
If 3) λ=0, β ≠ 0, then φi=k π, k=0,1,2 ...；
If 4) λ ≠ 0, β ≠ 0, then
From the above analysis, there is filter vector information φ in above formulaiReal solution, i.e. receiving terminal for target use Its interference can be completely eliminated by designing the ZF filter vector related to channel information and precoding vector information in family i.By Fixed in precoding vector, unrelated with channel condition information, therefore, blind transmitting terminal design precoding vector realizes blind interference pair Together.
On the other hand, the receiving terminal targeted customer i free degree is defined as：
Wherein, R(i)(ρ) represents speed of the targeted customer i obtained by SNR ρ, unit bps/Hz.For each target User can carry out completely interfering with elimination, it is not necessary to which sign extended or relaying auxiliary, whole system can reach the K/2 frees degree, together When be also the fully known channel condition information of transmitting terminal the free degree upper limit, so as to and blind transmitting terminal the free degree upper limit.
In the interference alignment schemes of the present invention, the design to the signal of reception by asymmetric complex signal, expand without symbol Exhibition increases extra signal space, and then the interference signal of targeted customer is eliminated by the design of wave filter, completes dry Disturb alignment.
The present invention adds the dimension of signal space, efficiently solves list first with the design of asymmetric complex signal Antenna restricted problem, then receiving terminal using channel information and precoding vector information design wave filter realize interference disappear completely Remove, and demonstrate transmitting terminal design precoding vectors to know channel information, so as to realize blind interference alignment.In addition, this hair Clear proof understands that the degree of freedom in system of K user's interference channel reaches K/2, when this is also known to transmitting end channel status information simultaneously The upper limit of degree of freedom in system.Blind interference alignment method proposed by the present invention, can effectively solve signal space in real system and tie up Spend not high enough and perfect channel condition information and obtain the problem of difficult, and effectively eliminate system interference, improve handling capacity.

Claims (3)

  1. The blind interference alignment method of 1.SISO systems, it is characterised in that comprise the following steps：
    S1, virtual multi-antenna channel model is established, be specially：
    Single antenna is configured in all nodes, sends letter in reply number in transmitting terminal, user i reception signal isTo ensure to disturb aligned signal space, designed using asymmetric complex signal, user i's Reception signal can be rewritten asWherein, yi=[Re { yi} Im{yi}]T, ni=[Re {ni} Im{ni}]T, ()TThe transposition of vector is represented, Re { } represents the real part of complex signal, and Im { } represents the imaginary number of complex signal Part, channel coefficients are defined as Hij=| hij|J(θij),θij=∠ hij, transmitting terminal i signal For xi=visi, wherein, vi∈R2×1It is precoding vector, | | vi||2≤ P is that each base station power limits, siIt is scalar data；
    S2, interference processing is carried out to receiving terminal, be specially：If the precoding vectors v of transmitting terminali=[cos αi sinαi]T, receive The filter vector at end is ui=[cos φi -sinφi], receiving terminal i reception signal isReceiving terminal uses filter vector uiHandled, so as to Interference is handledWherein, αiRepresent hair Penetrate end end i filter vector information, φiRepresent receiving terminal i filter vector information；
    S3, by non trivial solution analytical proof transmitting terminal design precoding vectors need not know channel information；
    Interference is completely eliminated for S4, acquisition least interference equation；
    S5, carry out blind interference alignment；
    S6, degree of freedom in system obtained according to the definition of the free degree, wherein, the definition of the free degree isR(i)(ρ) Represent speed of the user i obtained by SNR ρ, unit bps/Hz.
  2. 2. the blind interference alignment method of SISO systems according to claim 1, it is characterised in that：Least interference side described in S4 Cheng WeiWherein, θj, j ∈ 1,2 ... and .K } represent channel information, αjRepresent Precoding vector information, φiExpression receiving terminal i filter vector information, j ∈ 1,2 ... .K }.
  3. 3. the blind interference alignment method of SISO systems according to claim 1, it is characterised in that：Blind interference alignment described in S4 Specially：Transmitting terminal determines non-zero precoding vector in the case where not knowing channel status, realizes blind interference alignment, therefore, There was only a variable in one equation, each equation has solution, interference is completely eliminated, so as to obtain the disturbance equation of system：Solve equation, it is assumed that Then disturbance equation can be simplified to λ cos (φi)-βsin(φi)=0, so as to equation Solution is analyzed, and is rationally designed and is received end filter, i.e. receiving terminal can be designed by channel information and precoding vector information compels Its interference is completely eliminated in zero filter vector.
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CN108476183B (en) * 2015-10-26 2020-12-01 华为技术有限公司 Receiver and precoding system using asymmetric incomplete channel knowledge
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