CN102271119A - Differential Relay Cooperative Communication Method Using Quadrature Amplitude Modulation - Google Patents

Abstract

The invention provides a method for realizing differential relay cooperative communication by adopting quadrature amplitude modulation, and mainly aims to solve the problem of relatively lower bit error rate performance under high-order modulation in the prior art. The method is implemented by the following steps that: (1) signal to noise ratios of relay links are compared, and a relay node with the highest signal to noise ratio is selected from a plurality of relay nodes as an optimal relay node; (2) a source node performs constellation mapping and differential modulation on transmitted information, and transmits a differential modulation output signal to a destination node and the optimal relay node; (3) the optimal relay node performs differential demodulation and the differential modulation on a received signal, and forwards the differential modulation output signal to the destination node; and (4) the destination node performs the differential demodulation on the transmitted signal of the source node and the transmitted signal of the optimal relay node, performs maximal ratio combining on the differential demodulation output signal and performs inverse constellation mapping on a maximal ratio combining output signal to obtain signal source information. By the method, the bit error rate performance of a cooperative communication system can be improved.

Description

Adopt the difference relaying collaboration communication method of quadrature amplitude modulation

Technical field

The invention belongs to the communications field, relate to a kind of difference relaying collaboration communication method that adopts quadrature amplitude modulation QAM, can be used for improving the bit error rate performance of many relayings of difference cooperation communication system.

Background technology

Multiple-input and multiple-output MIMO technology can make full use of space resources, under the situation that does not increase system bandwidth and transmitted power, can resist the decline of wireless channel effectively, thereby improves the availability of frequency spectrum of communication system.Yet at some actual application scenarioss, such as the up link of cellular system, wireless self-organization network and wireless sensor network, portable terminal or network node are subjected to own vol, and the restriction of complexity and power consumption is difficult to direct using MIMO technique.So a kind of new space diversity reception to communicate-cooperative diversity technique arises at the historic moment.Thereby its basic principle is a plurality of terminals or the node that participate in collaboration communication comes shared link resource acquisition space diversity gain each other by forming a kind of virtual mimo system.Cooperative diversity technique has been broken through the restriction of traditional MIMO technology to terminal equipment, provides new approaches for it moves towards practicability.

Research about cooperative diversity technique at first all mainly concentrates under the situation of single via node.Along with going deep into of research, adopt the cooperation transmission scheme of many via nodes to receive increasing concern.This scheme can increase the diversity gain of collaboration communication widely, thereby can satisfy higher QoS requirement.In many relayings cooperation communication system, source node and via node distribute orthogonal sub-channels according to the mode of time-division or frequency division, and all via nodes all participate in cooperation transmission.Though this scheme can obtain the diversity gain exponent number that is directly proportional with the via node number, the spectrum efficiency of having sacrificed system simultaneously.

At the lower problem of the spectrum efficiency of many relayings cooperation communication system, the researcher has proposed the relay selection scheme, promptly according to the channel quality of repeated link, only selects the via node an of the best to participate in cooperation transmission at every turn.Studies have shown that the scheme that all participates in cooperation transmission with all via node is compared, the relay selection scheme is in the spectrum efficiency that guarantees to obtain can promote significantly under the prerequisite of identical diversity gain exponent number collaboration communication.In addition, what existing relay selection scheme mostly adopted is relevant modulation, and this just requires via node and destination node will know complete channel condition information, yet this is the big and relatively more difficult thing of an expense for cooperation communication system.

For fear of estimating channel condition information, the researcher has proposed collaboration communication scheme that differential modulation and relay selection are combined again.At present, what this scheme mostly adopted is the differential modulation of constant amplitude, such as differential phase keying (DPSK) PSK.Utilize difference PSK, receiving node no longer needs to obtain channel condition information, gets final product correct decoding, thereby has realized a kind of compromise of cooperation communication system on complexity and performance.Yet, when order of modulation when higher, the bit error rate performance of difference PSK is poor, thereby causes such scheme not to be suitable for the situation of high speed data transfer.

Summary of the invention

The objective of the invention is to overcome the deficiency of prior art, propose a kind of difference relaying collaboration communication method that adopts QAM, to improve the bit error rate performance of cooperation communication system when higher in order of modulation.

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

(1) according to network planning requirement, for source node S is distributed N _RIndividual via node R _j, j=1,2, L N _R

(2) compare N _RThe signal to noise ratio of individual repeated link is selected a via node R with maximum signal to noise ratio _JParticipate in collaboration communication;

(3) source node S is at first carried out constellation mapping and differential modulation to information source information, and the output signal with differential modulation is sent to destination node D and best via node R then _J

(4) Zui Jia via node R _JCarry out differential ference spiral and differential modulation at first to received signal, secondly the output signal with differential modulation is forwarded to destination node D;

(5) destination node D is at first to the transmission signal and the optimal relay node R of source node S _JThe transmission signal carry out differential ference spiral respectively, secondly the output signal of differential ference spiral is carried out high specific and merges, the output signal that high specific is merged is carried out the constellation inverse mapping at last, obtains information source information.

The present invention is owing to unite and adopted differential modulation and relay selection technology, not only makes receiving node not needing to estimate to get final product correct decoding under the situation of channel condition information, also guaranteed that cooperation communication system can obtain the full-diversity gain simultaneously.When order of modulation is higher, because qam constellation has the minimum range bigger than PSK constellation, therefore the method for the present invention's proposition can obtain than the higher snr gain of existing method that adopts difference PSK, thereby improved the bit error rate performance of cooperation communication system, more be applicable to the situation of high speed data transfer simultaneously.

Description of drawings

Fig. 1 is the channel model figure of existing difference relaying collaboration communication method;

Fig. 2 is the flow chart that the present invention realizes;

Fig. 3 is the bit error rate performance emulation comparison diagram of the present invention and existing difference relaying collaboration communication method.

Embodiment

Below in conjunction with accompanying drawing embodiments of the invention are elaborated: present embodiment is being to implement under the prerequisite with the inventive method, provided detailed execution mode and concrete operating procedure, but protection scope of the present invention is not limited to following embodiment.

The channel model of the difference relaying collaboration communication method that the present invention adopts as shown in Figure 1, wherein S is a source node, D is a destination node, R _jBe via node, j=1,2, L N _R, N wherein _RTotal number of expression via node.All communication nodes all adopt single antenna and are operated in TDD mode.

With reference to Fig. 2, performing step of the present invention is as follows:

Step 1 according to network planning requirement, is selected N arbitrarily from the nearest node of distance source node S _RIndividual node R _j, j=1,2, L N _R, as the via node of source node S, consider the implementation complexity of cooperation communication system, when near the via node number the source node S is many, select 4～8 via nodes.

Step 2, relatively N _RThe signal to noise ratio of individual repeated link is selected a via node R with maximum signal to noise ratio _JParticipate in collaboration communication.

2a) estimate that source node S is to via node R _jThe link signal to noise ratio J=1,2, L, N _R

2b) estimate via node R _jLink signal to noise ratio to destination node D

J=1,2, L, N _R

2c) utilize the parameter of above-mentioned estimation

With

Calculate the signal to noise ratio of repeated link

J=1,2, L, N _R

2d) the signal to noise ratio of comparison repeated link

Selection has the via node R of maximum signal to noise ratio _JParticipate in collaboration communication.

Step 3, source node S is carried out constellation mapping and differential modulation to information source information.

3a) according to the planisphere of QAM, source node S is mapped to source symbol s with information source information _{S, n}, wherein, the discrete time subscript of n 〉=1 representation signal;

3b) the initialization output signal of setting differential modulation is x _{S, 0}=1, calculate differential modulation signal: x _{S, n}=s _{S, n}x _{S, n-1}/ a _{S, n-1}, wherein, a _{S, n-1}=| x _{S, n-1}| be the power normalization coefficient.

Step 4, source node S is sent to destination node D and best via node R simultaneously with the output signal of differential modulation _J

Step 5, best via node R _JTransmission signal to source node S carries out differential ference spiral.

5a) estimate that source node S is to optimal relay node R _JChannel power: Y wherein _{SR, n}Expression optimal relay node R _JReceived signal, L represents the estimation range of channel power;

5b) utilize described y _{SR, n}And μ ' _{SR, n}Estimate that source node S is to optimal relay node R _JThe power normalization coefficient: $a_{\mathrm{SR},n}^{\′}=\left|y_{\mathrm{SR},n}\right|/\sqrt{{\mathrm{\μ}}_{\mathrm{SR},n}^{\′}};$

5c) utilize described μ ' _{SR, n}And a ' _{SR, n}, the output signal of calculating differential ference spiral:

Wherein * represents the conjugate operation of plural number.

Step 6, optimal relay node R _JThe differential ference spiral signal is carried out differential modulation again: the initialization output signal of setting differential modulation is x _{R, 0}=1, the output signal of calculating differential modulation: x _{R, n}=s _{R, n}x _{R, n-1}/ a _{R, n-1}, wherein, a _{T, n-1}=| x _{R, n-1}| be the power normalization coefficient.

Step 7, optimal relay node R _JThe output signal of differential modulation is forwarded to destination node D.

Step 8, destination node D carries out differential ference spiral to the transmission signal of source node S.

8a) estimate the channel power of source node S to destination node D:

Y wherein _{SD, n}The received signal of expression destination node D, L represents the estimation range of channel power;

8b) utilize described y _{SD, n}And μ ' _{SD, n}Estimate the power normalization coefficient of source node S to destination node D: $a_{\mathrm{SD},n}^{\′}=\left|y_{\mathrm{SD},n}\right|/\sqrt{{\mathrm{\μ}}_{\mathrm{SD},n}^{\′}};$

8c) utilize described μ ' _{SD, n}And a ' _{SD, n}, the output signal of calculating differential ference spiral:

Wherein * represents the conjugate operation of plural number.

Step 9, destination node D is to optimal relay node R _JThe transmission signal carry out differential ference spiral.

9a) estimate optimal relay node R _JChannel power to destination node D:

Y wherein _{RD, n}The received signal of expression destination node D, L represents the estimation range of channel power;

9b) utilize described y _{RD, n}And μ ' _{RD, n}, estimate optimal relay node R _JPower normalization coefficient to destination node D: $a_{\mathrm{RD},n}^{\′}=\left|y_{\mathrm{RD},n}\right|/\sqrt{{\mathrm{\μ}}_{\mathrm{RD},n}^{\′}};$

9c) utilize described μ ' _{RD, n}And a ' _{RD, n}, the output signal of calculating differential ference spiral:

Wherein * represents the conjugate operation of plural number.

Step 10, destination node D is to the differential ference spiral output signal s ' of step 8 _{SD, n}Differential ference spiral output signal s ' with step 9 _{RD, n}Carrying out high specific merges.

10a) calculate the high specific merging parameter g of source node S respectively to destination node D _{SD, n}With optimal relay node R _JHigh specific to destination node D merges parameter g _{RD, n}:

$g_{\mathrm{SD},n}={\mathrm{\μ}}_{\mathrm{SD},n}^{\′}{\mathrm{\γ}}_{\mathrm{RD}}^J/({\mathrm{\μ}}_{\mathrm{SD},n}^{\′}{\mathrm{\γ}}_{\mathrm{RD}}^J+{\mathrm{\μ}}_{\mathrm{RD},n}^{\′J}{\mathrm{\γ}}_{\mathrm{eq}}^J),$

$g_{\mathrm{RD},n}={\mathrm{\μ}}_{\mathrm{RD},n}^{\′J}{\mathrm{\γ}}_{\mathrm{eq}}^J/({\mathrm{\μ}}_{\mathrm{SD},n}^{\′}{\mathrm{\γ}}_{\mathrm{RD}}^J+{\mathrm{\μ}}_{\mathrm{RD},n}^{\′J}{\mathrm{\γ}}_{\mathrm{eq}}^J),$

μ wherein _{SD, n}The expression source node S is to the estimation of the channel power of destination node D, μ ' _{RD, n}Expression optimal relay node R _JArrive the estimation of the channel power of destination node D,

Expression optimal relay node R _JArrive the estimation of the signal to noise ratio of destination node D,

The estimation of the signal to noise ratio of expression best relay link;

10b) utilize described g _{SD, n}And g _{RD, n}, calculate the output signal that high specific merges: s ' _{S, n}=g _{SD, n}S ' _{SD, n}+ g _{RD, n}S ' _{RD, n}, s ' wherein _{RD, n}The expression source node S is to the differential ference spiral output signal of destination node D, s ' _{RD, n}Expression optimal relay node R _JDifferential ference spiral output signal to destination node D.

Step 11, the output signal s ' that destination node D merges high specific _{S, n}Carry out the constellation inverse mapping, obtain information source information.

Advantage of the present invention can be by following emulation further instruction:

1) simulated conditions:

The data frame length of supposing sending node is 200, and character rate is 100kHz, and carrier frequency is 1.9GHz, and internodal relative moving speed is 1.8km/h, and then corresponding normalization Doppler frequency shift is f _dT _s=10 ^-4.5, f wherein _dThe expression Doppler frequency shift, T _sThe expression symbol period.

The via node number that is assumed to be the source node S distribution is 4, i.e. N _R=4; Source node S and best via node R _JTransmitted power equate and all be P; Best via node R _JWith the noise of destination node D be that additive white Gaussian noise and average equal zero, variance is N ₀

2) emulation content and result:

Utilize computer that collaboration communication method and the existing error sign ratio of the collaboration communication method of difference PSK that adopts that the present invention proposes carried out emulation relatively.Simulation result as shown in Figure 3, wherein parameter L is represented the estimation range of channel power among the present invention, signal to noise ratio is defined as P/N ₀

From Fig. 3 as seen, equal 10 when error sign ratio ^-4And order of modulation equals 16,32 and respectively at 64 o'clock, and the collaboration communication method that adopts the present invention to propose adopts the snr gain of the collaboration communication method of difference PSK to be respectively 1.2dB, 2.3dB and 3.1dB with respect to tradition.

Claims (7)

1. a difference relaying collaboration communication method that adopts quadrature amplitude modulation comprises the steps:

(1) according to network planning requirement, for source node S is distributed N _RIndividual via node R _j, j=1,2, L N _R

(2) compare N _RThe signal to noise ratio of individual repeated link is selected a via node R with maximum signal to noise ratio _JParticipate in collaboration communication;

(3) source node S is at first carried out constellation mapping and differential modulation to information source information, and the output signal with differential modulation is sent to destination node D and optimal relay node R then _J

(4) optimal relay node R _JCarry out differential ference spiral and differential modulation at first to received signal, secondly the output signal with differential modulation is forwarded to destination node D;

(5) destination node D is at first to the transmission signal and the optimal relay node R of source node S _JThe transmission signal carry out differential ference spiral respectively, secondly the output signal of differential ference spiral is carried out high specific and merges, the output signal that high specific is merged is carried out the constellation inverse mapping at last, obtains information source information.

2. collaboration communication method according to claim 1, wherein step (2) is described from N _RSelect an optimal relay node R in the individual via node _JParticipate in collaboration communication, carry out as follows:

(2a) estimate that source node S is to via node R _jThe link signal to noise ratio

J=1,2, L, N _R

(2b) estimate via node R _jLink signal to noise ratio to destination node D

J=1,2, L, N _R

(2c) utilize described

With

Calculate the signal to noise ratio of repeated link

J=1,2, L, N _R

(2d) signal to noise ratio of comparison repeated link

Selection has the via node R of maximum signal to noise ratio _JParticipate in collaboration communication.

3. collaboration communication method according to claim 1, wherein the described source node S of step (3) is carried out constellation mapping and differential modulation to information source information, carries out as follows:

(3a) according to the planisphere of quadrature amplitude modulation, source node S is mapped to source symbol s with information source information _{S, n}, wherein, the discrete time subscript of n 〉=1 representation signal;

(3b) the initialization output signal of setting differential modulation is x _{S, 0}=1, utilize following formula to calculate differential modulation signal: x _{S, n}=s _{S, n}x _{S, n-1}/ a _{S, n-1}, wherein, a _{S, n-1}=| x _{S, n-1}| be the power normalization coefficient.

4. collaboration communication method according to claim 1, the wherein related optimal relay node R of step (4) _JCarry out differential ference spiral to received signal, carry out as follows:

(4a) estimate that source node S is to optimal relay node R _JChannel power:

Y wherein _{SR, n}Expression optimal relay node R _JReceived signal, L represents the estimation range of channel power;

(4b) utilize described y _{SR, n}And μ ' _{SR, n}, estimate that source node S is to optimal relay node R _JThe power normalization coefficient: $a_{\mathrm{SR},n}^{\′}=\left|y_{\mathrm{SR},n}\right|/\sqrt{{\mathrm{\μ}}_{\mathrm{SR},n}^{\′}};$

(4c) utilize described μ ' _{SR, n}And a ' _{SR, n}, the output signal of calculating differential ference spiral:

Wherein * represents the conjugate operation of plural number.

5. collaboration communication method according to claim 1, wherein the related destination node D of step (5) carries out differential ference spiral to the transmission signal of source node S, carries out as follows:

(5a) estimate the channel power of source node S to destination node D: Y wherein _{SD, n}The received signal of expression destination node D, L represents the estimation range of channel power;

(5b) utilize described y _{SD, n}And μ ' _{SD, n}, estimate the power normalization coefficient of source node S to destination node D: $a_{\mathrm{SD},n}^{\′}=\left|y_{\mathrm{SD},n}\right|/\sqrt{{\mathrm{\μ}}_{\mathrm{SD},n}^{\′}};$

(5c) utilize described μ ' _{SD, n}And a ' _{SD, n}, the output signal of calculating differential ference spiral:

Wherein * represents the conjugate operation of plural number.

6. collaboration communication method according to claim 1, wherein the related destination node D of step (5) is to optimal relay node R _JThe transmission signal carry out differential ference spiral, carry out as follows:

(6a) estimate optimal relay node R _JChannel power to destination node D:

Y wherein _{RD, n}The received signal of expression destination node D, L represents the estimation range of channel power;

(6b) utilize described y _{RD, n}And μ ' _{RD, n}Estimate optimal relay node R _JPower normalization coefficient to destination node D: $a_{\mathrm{RD},n}^{\′}=\left|y_{\mathrm{RD},n}\right|/\sqrt{{\mathrm{\μ}}_{\mathrm{RD},n}^{\′}};$

(6c) utilize described μ ' _{RD, n}And a ' _{RD, n}, the output signal of calculating differential ference spiral:

Wherein * represents the conjugate operation of plural number.

7. collaboration communication method according to claim 1, wherein the high specific of the described destination node D of step (5) merges, and realizes according to following steps:

(7a) calculate the high specific merging parameter g of source node S respectively to destination node D _{SD, n}With optimal relay node R _JHigh specific to destination node D merges parameter g _{RD, n}:

$g_{\mathrm{SD},n}={\mathrm{\μ}}_{\mathrm{SD},n}^{\′}{\mathrm{\γ}}_{\mathrm{RD}}^J/({\mathrm{\μ}}_{\mathrm{SD},n}^{\′}{\mathrm{\γ}}_{\mathrm{RD}}^J+{\mathrm{\μ}}_{\mathrm{RD},n}^{\′J}{\mathrm{\γ}}_{\mathrm{eq}}^J),$

$g_{\mathrm{RD},n}={\mathrm{\μ}}_{\mathrm{RD},n}^{\′J}{\mathrm{\γ}}_{\mathrm{eq}}^J/({\mathrm{\μ}}_{\mathrm{SD},n}^{\′}{\mathrm{\γ}}_{\mathrm{RD}}^J+{\mathrm{\μ}}_{\mathrm{RD},n}^{\′J}{\mathrm{\γ}}_{\mathrm{eq}}^J),$

μ ' wherein _{SD, n}The expression source node S is to the estimation of the channel power of destination node D; μ ' _{RD, n}Expression optimal relay node R _JArrive the estimation of the channel power of destination node D;

Expression optimal relay node R _JArrive the estimation of the signal to noise ratio of destination node D;

The estimation of the signal to noise ratio of expression best relay link;

(7b) utilize described g _{SD, n}And g _{RD, n}, calculate the output signal that high specific merges: s ' _{S, n}=g _{SD, n}S ' _{SD, n}+ g _{RD, n}S ' _{SD, n}, s ' wherein _{SD, n}The expression source node S is to the differential ference spiral output signal of destination node D, s ' _{RD, n}Expression optimal relay node R _JDifferential ference spiral output signal to destination node D.

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