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, which mainly solves the problem of high complexity of the existing antenna selection method. The technical solution includes: performing orthogonal space-time block coding on the pilot signals of two communicating vehicles; calculating the pilot signal power of the two communicating vehicles; and selecting the best pilot signal power of the two communicating vehicles by the relay vehicle. Antenna: Estimate the channel gain between the two communication vehicles and the best antenna of the relay vehicle to obtain the amplification gain of the relay vehicle; the antenna selected by the relay vehicle amplifies the information sent by the two communication vehicles through the amplification gain Forward and complete information exchange. The present invention has the advantages of low complexity without estimating the channel state information of the link and calculating the end-to-end signal-to-noise ratio, and can be used in a two-way relay vehicle communication system with feedback time delay and channel estimation error.

Description

An Antenna Selection Method Based on Orthogonal Space-Time Block Coding in Vehicular Communications

technical field

The invention belongs to the technical field of wireless communication, and in particular relates to a method for selecting a relay antenna, which can be used in a two-way relay vehicle communication system.

Background technique

With the development of wireless communication and people's continuous demand for high-quality life, wireless communication has penetrated into every corner of people's life. In order to improve the system capacity and the communication quality of the wireless link, people have introduced the multiple-input multiple-output MIMO technology. The performance of the system can be improved by adopting appropriate coding and combining the space-time coding technology STBC formed by multi-antenna array technology. Among many codes, the Orthogonal Space-Time Block Code OSTBC proposed by Tarokh et al. has the characteristics that the sender does not need to know the channel state information, and the receiver can adopt a low-complexity linear maximum likelihood decoding scheme. SungSikNam et al studied in point-to-point AF two-way relay communication in the literature "Outage performance of forthogonal space–time block code damplify-and-forward two-way relay networks", inCommunications, IET, 2015, and verified that the source node application of orthogonal space-time block code OSTBC can improve system performance.

Due to the high cost of the radio frequency chain and the relatively low cost of the antenna, in actual scenarios, if the antenna is selected for the device and the antenna with good communication quality is connected to the limited radio frequency chain, it can effectively improve the communication performance of the system and can Reduce overhead costs. The antenna selection technology simplifies the hardware structure of the MIMO system and reduces the complexity of the multi-antenna system. For the MIMO two-way relay network, G.Amarasuriya et al. proposed an antenna selection method that maximizes the worst end-to-end signal-to-noise ratio max-min of the two source nodes and maximizes the sum rate max-sum of the two source nodes, but this Both methods need to estimate the channel state information of each link, which increases the complexity of the system. MingDing et al. proposed an antenna selection method based on the greedy minimum mean square error criterion in 2010. The disadvantage of this method is that the amount of feedback information is large and the calculation complexity is high. M. Eslamifar et al. proposed the max-max method, that is, the relay selects two antennas with the best channel gain between the two source nodes respectively. The disadvantage of this method is that when the channel gain between the selected antenna and one of the source nodes is the best When it is good, it cannot be guaranteed that the channel gain with another source node is also the best, and may even be the worst, which may lead to a sharp deterioration in the performance of the system.

Nowadays, with the rapid increase of in-vehicle users, in-vehicle wireless communication has received great attention. In vehicular wireless communication, in order to improve communication quality, vehicles usually need to communicate with relays. Relays can be divided into fixed relays and mobile relays. Fixed relays are usually roadside base stations or hot spots, and mobile relays are usually for surrounding vehicles. Ata, SerdarOzgur et al. studied two vehicles with a single antenna in the literature "RelayantennaselectionforV2VcommunicationsusingPLNCovercascadedfadingchannels", IWCMC, IEEE2015, and completed information interaction with the assistance of a multi-antenna relay vehicle. The relay vehicle is based on the traditional signal-to-noise ratio max The -min criterion selects the best antenna to amplify the forwarding information. Since this method needs to estimate the channel state information of all links in the system, it increases the complexity of the system.

At present, the research on communication between vehicles in vehicular communication mainly focuses on the transmission scenario of selecting the best relay vehicle for communication among multiple potential relay vehicles. There are few literatures that combine OSTBC technology and multi-antenna selection technology combined for research.

Contents of the invention

The purpose of the present invention is to address the deficiencies of the above-mentioned prior art, and propose a method for selecting antennas based on orthogonal space-time block coding in vehicle communication, so as to avoid the estimation of channel state information CSI and improve the performance of the two-way mobile relay vehicle communication system. performance.

To achieve the above object, technical solutions of the present invention include as follows:

(1) Carry out orthogonal space-time block coding to the pilot signals of the first communication vehicle A and the second communication vehicle B respectively, obtain coded pilot signals X ₁ and X ₂ ;

(2) calculate the pilot signal power P _{A of the first communication vehicle A and the second communication vehicle B, k} and P _{B, k} ;

(3) The relay vehicle R selects the antenna according to the pilot signal power P _A,k and P _B,k of the two communication vehicles, that is, finds the minimum value of the pilot signal power received on all antennas, and obtains the alternative pilot signal Frequency signal power set Φ, the antenna with the largest pilot signal power in this set Φ is the best antenna k ^* selected:

${\mathrm{<span\; class="notranslate">\; k</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; arg</span>}\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Element;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; t</span>}}}{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; x</span>}}\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; ,</span>$

where k∈[1,L], L is the number of antennas of the relay vehicle R, and S _ant is all the optional antennas of the relay vehicle R;

(4) Estimate the channel gain between the first communication vehicle A and the second communication vehicle B to the k ^* th antenna of the relay vehicle R respectively and Obtain the amplification gain G of the relay vehicle R;

(5) The relay vehicle R amplifies the information sent by the two communication vehicles by G times through the best antenna k ^* and then forwards it to complete the two-way relay transmission process.

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

First, compared with the traditional optimal antenna selection method, the relay vehicle only needs to select the antenna according to the power of the received pilot signal, instead of the channel between the two communication vehicles and the relay vehicle. estimate. Since the typical channel estimation algorithm usually involves complex mathematical operations such as matrix pseudo-inverse and iterative mean square error calculation, while the calculation of received power only involves the average value operation of the square of the modulus value, the method of the present invention significantly reduces the computational complexity of the relay vehicle Spend.

Second, compared with the traditional optimal antenna selection method, the relay vehicle does not need to calculate the end-to-end signal-to-noise ratio, while the traditional optimal antenna selection method requires the relay vehicle to calculate End-to-end signal-to-noise ratio, due to non-ideal factors such as channel estimation error and feedback delay in the actual communication system, the multiplication and division operations involved in calculating the end-to-end signal-to-noise ratio will amplify the above-mentioned non-ideal factors Negative effects lead to greatly increased probability of wrong antenna selection, so the method of the present invention is more suitable for practical communication systems.

Description of drawings

Fig. 1 is the vehicle communication system model figure that the present invention uses;

Fig. 2 is the realization flowchart of the present invention;

Fig. 3 is a comparison chart of system outage probability using the method of the present invention and the traditional optimal method.

detailed description

The specific implementation and effects of the present invention will be further described below in conjunction with the accompanying drawings.

With reference to Fig. 1, the two-way mobile relay vehicular communication system that the present invention adopts, it comprises a relay vehicle R and two communication, namely the first communication vehicle A and the second communication vehicle B, this first communication vehicle A and the second communication vehicle The number of antennas configured by communication vehicle B is M and N respectively, and the number of antennas configured by relay vehicle R is L, and both work in half-duplex mode. The first communication vehicle A and the second communication vehicle B use the relay vehicle R to perform information exchange, wherein the protocol adopted by the relay R is an amplification and forwarding protocol, and the best antenna is selected for the relay vehicle R to transmit information.

With reference to Fig. 2, the step that the present invention carries out antenna selection according to Fig. 1 vehicular communication system is as follows:

Step 1, respectively encode the pilot signals of the two communicating vehicles.

In common coding, space-time lattice coding must be decoded with Viterbi decoding algorithm, which has high decoding complexity and is not suitable for high-speed information transmission systems; although layered space-time coding has a simple structure, it does not Provides transmit diversity gain and needs to know the channel state information for decoding; because the orthogonal space-time block coding not only has the characteristics that the sending end does not need to know the channel state information, but also can use low-complexity linear maximum likelihood for decoding at the receiving end. Moreover, the same diversity gain as the maximum ratio combined reception can be obtained, so this example adopts orthogonal space-time block coding to encode the pilot signal, and the steps are as follows:

(1a) The first communication vehicle A performs orthogonal space-time block coding on the pilot signal x ₁ to obtain the coded pilot signal X ₁ , where X ₁ ∈ C M ^×T , C ^M×T represents M×T Complex matrix, M is the number of antennas of the first communication vehicle A, and T is the symbol period for sending;

(1b) The second communication vehicle B performs orthogonal space-time block coding on the pilot signal x ₂ to obtain the coded pilot signal X ₂ , where X ₂ ∈ C N ^×T , C ^N×T means N×T A complex matrix, N is the number of antennas of the second communication vehicle B.

Step 2, obtain the pilot signal powers P _A,k and P _B,k of the two communicating vehicles respectively.

(2a) Obtain the pilot signal power P _A,k of the first communication vehicle A:

(2a1) The first communication vehicle A sends its encoded pilot signal X ₁ to the relay vehicle R within T symbol periods, and the kth antenna of the relay vehicle R receives the pilot signal y from the first communication vehicle A _A,k , where T≥2;

(2a2) Transpose the pilot signal y _A,k to its conjugate Multiply to obtain the pilot signal power sequence in T symbol periods;

(2a3) Take the average value of these sequences obtained in (2a2), obtain the pilot signal power PA _,k of the first communication vehicle A, and save the result, where k∈[1,L], L is the relay The number of antennas of the vehicle R.

(2b) Obtain the pilot signal power P _B,k of the second communication vehicle B:

(2b1) The second communication vehicle B sends its encoded pilot signal X ₂ to the relay vehicle R within T symbol periods, and the kth antenna of the relay vehicle R receives the pilot signal from the second communication vehicle B as y _B,k ;

(2b2) Transpose the pilot signal y _B,k with its conjugate Multiply to obtain the pilot signal power sequence in T symbol periods;

(2b3) Average the sequences obtained in (2b2) to obtain the pilot signal power P _B,k of the second communication vehicle B, and save the result.

Step 3, the relay vehicle R selects the best antenna k ^* according to the pilot signal powers P _A,k and P _B,k of the two communicating vehicles.

(4a) The relay vehicle R calculates the minimum value of the pilot signal power received on all antennas, and selects an alternative pilot signal power set Φ;

(4b) Select the antenna with the largest pilot information power from the candidate set Φ, which is the best antenna k ^* :

${\mathrm{<span\; class="notranslate">\; k</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; arg</span>}\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Element;</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; t</span>}}}{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; x</span>}}\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; ,</span>$

Among them, S _ant is all optional antennas of the relay vehicle R.

Step 4. Estimate the channel gain between the two communication vehicles and the k ^* th antenna of the relay vehicle R.

This step can be realized by various existing methods, such as estimation method based on reference signal, blind estimation method and semi-blind estimation method, etc. The relay vehicle R in this example uses the estimation method based on reference signal to estimate the first communication Channel gain between vehicle A and the second communicating vehicle B to the k ^* th antenna of relay vehicle R and The steps are as follows:

(4a) inserting a known pilot symbol into the useful data sent by the first communication vehicle A to obtain a channel estimation result at the pilot position;

(4b) Using the channel estimation result at the pilot position, the channel gain between the first communication vehicle A and the k ^* th antenna of the relay vehicle R is obtained by interpolation

(4c) inserting a known pilot symbol into the useful data sent by the second communication vehicle B to obtain a channel estimation result at the pilot position;

(4d) Using the channel estimation result at the pilot position, the channel gain between the second communication vehicle B and the k ^* th antenna of the relay vehicle R is obtained by interpolation Complete channel estimation.

Step 5, the relay vehicle R assists in completing the two-way relay transmission process through the best antenna k ^* .

The k ^* th antenna of the relay vehicle R amplifies the information sent by the two communication vehicles by G times and then forwards it to complete the two-way relay transmission. The amplification gain G adopts a fixed gain G _a or a variable gain G _f , which are expressed as:

${\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; =</span>\sqrt{\frac{{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}^{\mathrm{<span\; class="notranslate">\; R</span>}}}{{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}^{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; k</span>}}^{<span\; class="notranslate">\; *</span>}}<span\; class="notranslate">\; |</span>{<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}^{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; k</span>}}^{<span\; class="notranslate">\; *</span>}}<span\; class="notranslate">\; |</span>{<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}}<span\; class="notranslate">\; ,</span>$

${\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; =</span>\sqrt{\frac{{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}^{\mathrm{<span\; class="notranslate">\; R</span>}}}{{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}^{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; \{</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; k</span>}}^{<span\; class="notranslate">\; *</span>}}<span\; class="notranslate">\; |</span>{<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}^{\mathrm{<span\; class="notranslate">\; B</span>}}\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; \{</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; k</span>}}^{<span\; class="notranslate">\; *</span>}}<span\; class="notranslate">\; |</span>{<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}}<span\; class="notranslate">\; ,</span>$

in and are the transmission powers of the first communication vehicle A, the second communication vehicle B and the relay vehicle R respectively, N ₀ is the variance of complex white Gaussian noise, ||·|| ² is the two-norm square of the matrix, E{ } Indicates the mean value.

In the vehicle communication system, because the vehicle speed is too fast, the channel between each link will change in real time, it is not suitable to use fixed gain, so this example uses variable gain.

Effect of the present invention can be further illustrated by following simulation:

1) Simulation conditions:

Normalize the distance between the two communication vehicles A and B to 1, assuming that the distance d _A between the first communication vehicle A and the relay vehicle R = 0.6, then the distance between the second communication vehicle B and the relay vehicle R d _B =1-d _A =0.4. Assume that the channel gains between the two communication vehicles A, B and the relay vehicle R all obey the Rayleigh distribution, the path loss index α=3, the Gaussian white noise power N ₀ in the system =1, and the target transmission rate threshold R _th =1bit /s/Hz, the signal-to-noise ratio of the system is SNR, the total power of the system γ=SNR*N ₀ , and the transmission power of two communication vehicles A, B and relay vehicle R is defined as P _t ^A =4γ/8, P _t ^B ＝2γ/8 and P _t ^R ＝2γ/8, the number of antennas of two communication vehicles A, B and relay vehicle R are M=2, N=2 and L=3 respectively, and the channel estimation error factor is ρ _e , ρ _e = 1 means that there is no channel estimation error, the correlation coefficient between the antenna selection time and the data transmission time channel is ρ _d , ρ _d = 1 means that there is no feedback delay, and respectively take {ρ _e , ρ _d } {1,1}, {0.99,1} and {0.99,0.95} were simulated;

2) Simulation content and results:

Under the above simulation conditions, the method of the present invention and the traditional optimal method are used to simulate and compare the outage probability of the two-way relay vehicular communication system, and the results are shown in FIG. 3 . The abscissa in Fig. 3 is the signal-to-noise ratio SNR of the system, the unit is dB, and the ordinate is the outage probability of the system.

As can be seen from Figure 3, when there is no feedback time delay and channel estimation error, the system outage probability performance of the method of the present invention approaches the system outage probability of the traditional optimal method; when feedback time delay and channel estimation error exist, the present invention The system outage probability performance of method is better than the system outage probability of traditional optimal method; Can also find out by Fig. 3, along with the increase of feedback delay and channel estimation error, the system outage probability of traditional optimal method and the method of the present invention The gap in system outage probability performance is also 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.