CN105591680A - Antenna selection method based on orthogonal space-time block coding in vehicle communication - Google Patents

Abstract

The invention discloses an antenna selection method based on orthogonal space-time block coding in vehicle communication in order to mainly solve the problem of high complexity of the conventional antenna selection method. According to the technical scheme, the method includes: orthogonal space-time block coding of pilot signals of two communication vehicles is performed; the pilot signal powers of the two communication vehicles are calculated; a relay vehicle selects the best antenna according to the pilot signal powers of the two communication vehicles; channel gains from the two communication vehicles to the best antenna of the relay vehicle are estimated, and the amplification gain of the relay vehicle is obtained; and the antenna selected by the relay vehicle amplifies information sent by the two communication vehicles via the amplification gain, and information interaction is completed. The method is advantageous in that the estimation of the channel state information of links and the calculation of the end-to-end signal to noise ratio are not needed, the complexity is low, and the method can be applied to bidirectional relay vehicle communication systems with feedback time delay and channel estimation errors.

Description

Antenna selecting method based on Orthogonal Space-Time Block Code in vehicle-carrying communication

Technical field

The invention belongs to wireless communication technology field, related in particular to a kind of relay antenna system of selection, can be used for bi-directional relayingVehicular communication system.

Background technology

Along with the development of radio communication and the people continuous demand to high-quality life, radio communication has penetrated into people's lifeEach corner. In order to improve the communication quality of power system capacity and Radio Link, people have introduced multiple-input and multiple-output MIMO skillArt. The Space-Time Codes STBC that adopts suitable coding and form in conjunction with many antenna arrays technology can improve the performance of system.In numerous codings, the Orthogonal Space-Time Block Code OSTBC that the people such as Tarokh propose has transmitting terminal does not need to know channel shapeState information, receiving terminal can adopt the features such as the linear maximum-likelihood decoding scheme of low complex degree. The people such as SungSikNam existDocument " Outageperformanceoforthogonalspace – timeblockcodedamplify-and-forwardtwo-wayRelaynetworks ", inCommunications, IET, has studied in the communication of point-to-point AF bi-directional relaying checking in 2015Source node application Orthogonal Space-Time Block Code OSTBC can improve the performance of system.

Because the cost cost high and antenna of rf chain is relatively low, in actual scene, if equipment is carried out to a day line options,The antenna of good communication quality is connected to limited rf chain, and the communication performance that can effectively improve system can reduce again expenseThis. Antenna Selection Technology is simplified mimo system hardware configuration, has reduced the complexity of multiaerial system. For MIMOBilateral relay network, the people such as G.Amarasuriya proposed to maximize the poorest end-to-end signal to noise ratio max-min of two source nodes andMaximize two source nodes and antenna selecting method speed max-sum, but these two methods all need to estimate the letter of each linkChannel state information, has increased the complexity of system. The people such as MingDing have proposed a kind of based on greedy lowest mean square in 2010The antenna selecting method of error criterion, the shortcoming of the method is that feedback information volume is large, computation complexity is high. M.Eslamifar etc.People has proposed max-max method, and relaying is selected two respectively and the best antenna of channel gain between two source nodes, the methodShortcoming be when channel gain between the antenna of selecting and one of them source node is preferably time, can not ensure and another source node between believeRoad gain is also best, may be even the poorest, may cause like this performance of system sharply to worsen.

Nowadays,, along with the sharply increase of user in car, in-vehicle wireless communication has been subjected to great concern. At in-vehicle wireless communicationIn, in order to improve communication quality, between vehicle, conventionally need to communicate by relaying, relaying can be divided into fixed relay and movementRelaying, fixed relay is generally base station, roadside or focus, and mobile relay is generally nearby vehicle. Ata, the people such as SerdarOzgurAt document " RelayantennaselectionforV2VcommunicationsusingPLNCoverca scadedfadingChannels ", IWCMC, has studied the two cars of single antenna in IEEE2015, auxiliary at the relay vehicle of antenna more thanHelp down and complete information interaction, relay vehicle is selected a best antenna amplification according to traditional signal to noise ratio max-min criterion and is turnedPhotos and sending messages, because the method needs the channel condition information of all links in estimating system, has therefore increased the complexity of system.

At present, for the research of communicating by letter between vehicle in vehicle-carrying communication, mainly concentrate on multiple potential relay vehicles, selectThe transmitting scene that wherein best relay vehicle communicates, seldom has document by orthogonal Space Time Coding OSTBC technology and many daysLine options technology combines to be studied.

Summary of the invention

The object of the invention is to the deficiency for above-mentioned prior art, propose in a kind of vehicle-carrying communication based on orthogonal space time groupThe antenna selecting method of coding, to avoid the estimation to channel condition information CSI, improves way moving relaying Vehicular communication systemPerformance.

For achieving the above object, technical scheme of the present invention comprises as follows:

(1) pilot signal of the first communication vehicle A and second communication vehicle B is carried out respectively to Orthogonal Space-Time Block Code,Arrive the pilot signal X after coding₁And X₂；

(2) the pilot signal power P of calculating the first communication vehicle A and second communication vehicle B_A,kAnd P_B,k；

(3) relay vehicle R is according to the pilot signal power P of two communication vehicles_A,kAnd P_B,kSelect antenna, to all antennasThe pilot signal power of upper reception is minimized, and draws alternative pilot signal power set Φ, pilot signal in this set ΦProminent antenna, is the best antenna k of selection^*：

$k^{*}=\arg \underset{k\∈S_{ant}}{max}\min \{P_{A,k},P_{B,k}\},$

Wherein k ∈ [1, L], L is the antenna number of relay vehicle R, S_antFor all alternative antennas of relay vehicle R;

(4) estimate that the first communication vehicle A and second communication vehicle B divide the k that is clipped to relay vehicle R^*Letter between root antennaRoad gainWithObtain the gain amplifier G of relay vehicle R;

(5) relay vehicle R is by best antenna k^*The information that two communication vehicles are sent forwards after amplifying G times,Complete bi-directional relaying transmitting procedure.

The present invention compared with prior art has the following advantages:

The first, the inventive method is compared with traditional optimal antenna system of selection, and relay vehicle only need to be according to the pilot tone letter receivingNumber power carries out a day line options, and needn't estimate the channel between two communication vehicles and relay vehicle. Due to typical caseChannel estimation method be usually directed to matrix pseudoinverse, iteration and ask the complicated mathematical operations such as mean square error, and only calculate received powerRelate to the mean value computing of mould value square, therefore the inventive method has significantly reduced the computation complexity of relay vehicle.

The second, the inventive method is compared with traditional optimal antenna system of selection, and relay vehicle does not need to calculate end-to-end signal to noise ratio,And traditional optimal antenna system of selection needs relay vehicle to calculate end-to-end signal to noise ratio according to the channel estimation value obtaining, due toIn practical communication system, can there is the non-ideal factor such as channel estimation errors and feedback delay, and relate to while calculating end-to-end signal to noise ratioAnd to multiplication and the division arithmetic negative effect that can amplify above-mentioned non-ideal factor, cause a day probability for line options mistake to increaseAdd, therefore the inventive method is more suitable for practical communication system.

Brief description of the drawings

Fig. 1 is the Vehicular communication system illustraton of model that the present invention uses;

Fig. 2 is realization flow figure of the present invention;

Fig. 3 is the system break probability comparison diagram that uses the inventive method and traditional best practice.

Detailed description of the invention

Below in conjunction with accompanying drawing, the specific embodiment of the present invention and effect are further described.

With reference to Fig. 1, the way moving relaying Vehicular communication system that the present invention adopts, it comprises that a relay vehicle R and two are logicalLetter, i.e. the first communication vehicle A and second communication vehicle B, the sky of this first communication vehicle A and second communication vehicle B configurationLine number is respectively M and N, and the antenna number of relay vehicle R configuration is L, and all under half-duplex mode, works. The first communicationVehicle A and second communication vehicle B utilize relay vehicle R to carry out information interaction, and wherein, the agreement that relaying R adopts is to amplifyRetransmission protocol, selects a best antenna to carry out communication to relay vehicle R.

With reference to Fig. 2, the step that the present invention carries out day line options according to Fig. 1 Vehicular communication system is as follows:

Step 1, encodes to the pilot signal of two communication vehicles respectively.

In common coding, space-time grid coding must carry out decoding with Viterbi decoding algorithm, and its decoding complexity is high,And be not suitable for the two-forty information transmission system; Although demixing time space is simple in structure, it does not provide emission diversity gainAnd decoding need to be known channel condition information; Because not only having transmitting terminal, Orthogonal Space-Time Block Code do not need to know channel shapeState information, the feature that can adopt the linear maximum likelihood of low complex degree to carry out decoding at receiving terminal, and can obtain and maximumReceive identical diversity gain than merging, so this example adopts Orthogonal Space-Time Block Code to encode to pilot signal, its stepSuddenly be:

(1a) the first communication vehicle A is to pilot signal x₁Carry out Orthogonal Space-Time Block Code, obtain the pilot signal X after coding₁，Wherein X₁∈C^M×T，C^M×TThe complex matrix that represents M × T, M is the antenna number of the first communication vehicle A, T is what sendSymbol period;

(1b) second communication vehicle B is to pilot signal x₂Carry out Orthogonal Space-Time Block Code, obtain the pilot signal after coding X₂, wherein X₂∈C^N×T，C^N×TThe complex matrix that represents N × T, N is the antenna number of second communication vehicle B.

Step 2, obtains respectively the pilot signal power P of two communication vehicles_A,kAnd P_B,k。

(2a) obtain the pilot signal power P of the first communication vehicle A_A,k：

(2a1) the first communication vehicle A sends the pilot signal X after oneself encoding to relay vehicle R in T symbol period₁，The k root antenna reception of relay vehicle R is from the pilot signal y of the first communication vehicle A_A,k, wherein T >=2;

(2a2) by this pilot signal y_A,kWith its conjugate transposeMultiply each other, obtain T the pilot signal power in symbol periodSequence;

(2a3) these sequences that (2a2) obtained are averaged, and obtain the pilot signal power P of the first communication vehicle A_A,k，And this result is preserved, wherein k ∈ [1, L], L is the antenna number of relay vehicle R.

(2b) obtain the pilot signal power P of second communication vehicle B_B,k：

(2b1) second communication vehicle B sends the pilot signal X after oneself encoding to relay vehicle R in T symbol period₂，The k root antenna reception of relay vehicle R is y from the pilot signal of second communication vehicle B_B,k；

(2b2) by this pilot signal y_B,kWith its conjugate transposeMultiply each other, obtain T the pilot signal power in symbol periodSequence;

(2b3) these sequences that (2b2) obtained are averaged, and obtain the pilot signal power P of second communication vehicle B_B,k，And this result is preserved.

Step 3, relay vehicle R is according to the pilot signal power P of two communication vehicles_A,kAnd P_B,kSelect best antenna k^*。

(4a) relay vehicle R minimizes to the pilot signal power receiving on all antennas, selects alternative pilot signal meritRate set Φ;

(4b) from alternative set Φ, select the prominent antenna of pilot frequency information, be best antenna k^*：

$k^{*}=\arg \underset{k\∈S_{ant}}{max}\min \{P_{A,k}^R,P_{B,k}^R\},$

Wherein S_antFor all alternative antennas of relay vehicle R.

Step 4, estimates that two communication vehicles are to relay vehicle R k^*Channel gain between root antenna.

This step pass through existing accomplished in many ways, for example method of estimation based on reference signal, blind estimating method and halfBlind estimating methods etc., the relay vehicle R of this example adopts the method for estimation based on reference signal to estimate respectively the first communication vehicle AWith second communication vehicle B to relay vehicle R k^*Channel gain between root antennaWithIts step is as follows:

(4a) in the useful data sending at the first communication vehicle A, insert known frequency pilot sign, obtain this pilot frequency locations placeChannel estimation results;

(4b) utilize the channel estimation results at pilot frequency locations place, obtain the first communication vehicle A to relay vehicle R by interpolation methodK^*Channel gain between root antenna

(4c) in the useful data sending at second communication vehicle B, insert known frequency pilot sign, obtain this pilot frequency locations placeChannel estimation results;

(4d) utilize the channel estimation results at pilot frequency locations place, obtain second communication vehicle B to relay vehicle R by interpolation methodK^*Channel gain between root antennaComplete channel estimating.

Step 5, relay vehicle R is by best antenna k^*Assistance completes bi-directional relaying transmitting procedure.

The k of relay vehicle R^*The information that root antenna is sent two communication vehicles is amplified doubly rear forwarding of G, completes bi-directional relayingTransmission, gain amplifier G adopts fixed gain G_aOr variable gain G_f, be expressed as:

$G_a=\sqrt{\frac{{P_t}^R}{{P_t}^A\left|\right|H_{A,k^{*}}|{|}^2+{P_t}^B|\left|H_{B,k^{*}}\right|{|}^2+N_0}},$

$G_f=\sqrt{\frac{{P_t}^R}{{P_t}^{A}E\left\{\right|\left|H_{A,k^{*}}\right|{|}^2\}+{P_t}^{B}E\{\left|\right|H_{B,k^{*}}\left|{|}^2\right\}+N_0}},$

WhereinWithBe respectively the transmitted power of the first communication vehicle A, second communication vehicle B and relay vehicle R, N₀For the variance of white complex gaussian noise, || ||²For two norm squared of matrix, E{} represents to average.

In Vehicular communication system, because car speed is too fast, the channel between each link can produce real-time change, should not adopt solidFixed gain, so the employing of this example is variable gain.

Effect of the present invention can be described further by following emulation:

1) simulated conditions:

Be 1 by the range normalization between two communication vehicle A, B, suppose the distance between the first communication vehicle A and relay vehicle RFrom d_A=0.6, the distance d between second communication vehicle B and relay vehicle R_B＝1-d_A=0.4. Suppose two communication trucksThe equal Rayleigh distributed of channel gain between A, B and a relaying R, path loss index α=3, the white Gaussian in systemNoise power N₀=1, target transmission speed threshold value R_th=1bit/s/Hz, the signal to noise ratio of system is SNR, the total work of systemRate γ=SNR*N₀, the transmitted power that defines two communication vehicle A, B and relay vehicle R is respectively P_t ^A＝4γ/8、P_t ^B=2 γ/8 and P_t ^R=2 γ/8, the antenna number of two communication vehicle A, B and relay vehicle R is respectively M=2, N=2And L=3, the channel estimation error factor is ρ_e，ρ_e=1 represents not exist channel estimation error, day line options moment and dataThe coefficient correlation of transmission time channel is ρ_d，ρ_d=1 represents not have feedback delay, respectively to { ρ_e,ρ_dGet 1,1},{ 0.99,1} is with { 0.99,0.95} has done emulation;

2) emulation content and result:

Under above-mentioned simulated conditions, use the inventive method and traditional best practice, respectively to bi-directional relaying Vehicular communication systemOutage probability carries out emulation comparison, and result as shown in Figure 3. The signal to noise ratio snr that in Fig. 3, abscissa is system, unit is dB,Ordinate is the outage probability of system.

As seen from Figure 3, in the time not there is not feedback delay and channel estimation error, the system break probability of the inventive methodCan approach the system break probability of traditional best practice; In the time that feedback delay and channel estimation error exist, the inventive method beSystem Outage probability of distributed antenna is better than the system break probability of traditional best practice; Be it can also be seen that by Fig. 3, along with feedback delay and letterThe increase of road misjudgment, the gap of the system break probability performance of the system break probability of traditional best practice and the inventive methodAlso increasing.

Claims (6)

1. the antenna selecting method based on Orthogonal Space-Time Block Code in vehicle-carrying communication, comprising:

(1) pilot signal of the first communication vehicle A and second communication vehicle B is carried out respectively to Orthogonal Space-Time Block Code, obtain the pilot signal X after coding₁And X₂；

(2) the pilot signal power P of calculating the first communication vehicle A and second communication vehicle B_A,kAnd P_B,k；

(3) relay vehicle R is according to the pilot signal power P of two communication vehicles_A,kAnd P_B,kSelect antenna, the pilot signal power receiving on all antennas is minimized, draw alternative pilot signal power set Φ, antenna corresponding to maximum pilot signal power in this set Φ, is the best antenna k of selection^*：

Wherein k ∈ [1, L], L is the antenna number of relay vehicle R, S_antFor all alternative antennas of relay vehicle R;

(4) estimate that the first communication vehicle A and second communication vehicle B divide the k that is clipped to relay vehicle R^*Channel gain between root antennaWithObtain the gain amplifier G of relay vehicle R;

(5) relay vehicle R is by best antenna k^*The information that two communication vehicles are sent forwards after amplifying G times, completes bi-directional relaying transmitting procedure.

2. the antenna selecting method based on Orthogonal Space-Time Block Code in vehicle-carrying communication according to claim 1, wherein in step (1), the pilot signal of the first communication vehicle A and second communication vehicle B is carried out respectively to Orthogonal Space-Time Block Code, step is as follows:

(1a) the first communication vehicle A is by pilot signal x₁Carry out Orthogonal Space-Time Block Code, obtain the pilot signal X after coding₁, wherein X₁∈C^M×T，C^M×TThe complex matrix that represents M × T, M is the antenna number of the first communication vehicle A, T is the symbol period sending;

(1b) second communication vehicle B is by pilot signal x₂Carry out Orthogonal Space-Time Block Code, obtain the pilot signal X after coding₂, wherein X₂∈C^N×T，C^N×TThe complex matrix that represents N × T, N is the antenna number of second communication vehicle B.

3. the antenna selecting method based on Orthogonal Space-Time Block Code in vehicle-carrying communication according to claim 1, wherein calculates the first communication vehicle A pilot signal power P in step (2)_A,k, step is as follows:

(2a) the first communication vehicle A sends the pilot signal X after oneself encoding to relay vehicle R in T symbol period₁, the k root antenna reception of relay vehicle R is y from the pilot signal of the first communication vehicle A_A,k; By this pilot signal y_A,kWith its conjugate transposeMultiply each other, obtain T the pilot signal power sequence in symbol period;

(2b) these sequences that (2a) obtained are averaged and are obtained the pilot signal power P of the first communication vehicle A_A,k, and preserve, wherein k ∈ [1, L], L is the antenna number of relay vehicle R.

4. the antenna selecting method based on Orthogonal Space-Time Block Code in vehicle-carrying communication according to claim 1, wherein calculates second communication vehicle B pilot signal power P in step (2)_B,k, step is as follows:

(2c) second communication vehicle B sends the pilot signal X after oneself encoding to relay vehicle R in T symbol period₂, the k root antenna reception of relay vehicle R is y from the pilot signal of second communication vehicle B_B,k; By this pilot signal y_B,kWith its conjugate transposeMultiply each other, obtain T the pilot signal power sequence in symbol period,

(2d) these sequences that (2c) obtained are averaged and are obtained the pilot signal power P of second communication vehicle B_B,k, and preserve, wherein k ∈ [1, L], L is the antenna number of relay vehicle R.

5. the antenna selecting method based on Orthogonal Space-Time Block Code in vehicle-carrying communication according to claim 1, wherein estimates in step (4) that the first communication vehicle A and second communication vehicle B are to relay vehicle R k^*Channel gain between root antennaWithIts step is as follows:

(4a) in the useful data sending at the first communication vehicle A, insert known frequency pilot sign, obtain the channel estimation results at this pilot frequency symbol position place;

(4b) utilize the channel estimation results at pilot frequency locations place, obtain the first communication vehicle A to relay vehicle R k by interpolation method^*Channel gain between root antenna

(4c) in the useful data sending at second communication vehicle B, insert known frequency pilot sign, obtain the channel estimation results at this pilot frequency symbol position place;

(4d) utilize the channel estimation results at pilot frequency locations place, obtain second communication vehicle B to relay vehicle R k by interpolation method^*Channel gain between root antennaComplete channel estimating.

6. the antenna selecting method based on Orthogonal Space-Time Block Code in vehicle-carrying communication according to claim 1, the wherein gain amplifier G of step (4) relay vehicle R, adopts fixed gain G_aOr variable gain G_f, be expressed as:

Wherein P_t ^A、P_t ^BAnd P_t ^RBe respectively the transmitted power of the first communication vehicle A, second communication vehicle B and relay vehicle R, N₀For the variance of white complex gaussian noise, || ||²For two norm squared of matrix, E{} represents to average.