CN105490721A - Estimate-forward method of full-duplex transportation cooperative-communication network - Google Patents

Abstract

The present invention provides an estimate-forward method of a full-duplex transportation cooperative-communication network. The estimate-forward method comprises the following steps: step one, a transportation cooperative-communication network consisting of multiple nodes is established, wherein each node can serve as a relay node for resisting a source node to transmit a signal to a destination node; step two, after the relay nodes receive the transmitted signal, the relay nodes use an Unconstrained minimum mean square error estimation algorithm to obtain estimated soft information of the transmitted signal; step three, transmitting powers on the relay nodes are normalized; step four, the relay nodes transmit the soft information obtained in step two to the destination node; and step five, after receiving forwarding information, the destination node uses a Generalized sphere detection algorithm signal for detecting the signal. According to the estimate-forward method of the present invention, the relay nodes forward a simple estimation value of the received signal to the destination node, thereby obtaining the performance superior to the amplify-forward and decode-forward method, and greatly reducing the bit error ratio of a receiving terminal.

Description

A kind of estimation retransmission method of full duplex traffic cooperative communication network

Technical field

The present invention relates to the signal processing technology field of wireless communication field, particularly, relate to a kind of estimation retransmission method of full duplex traffic cooperative communication network.

Background technology

Cooperative communication network is the cordless communication network of extensively research application at present, and collaboration communication has raising throughput, strengthens transmission reliability and expands the advantage of transmission range.Cooperative communication network lists relevant communication standards in, such as LTE-A and IEEE802.16j standard.Collaboration communication key technology is introduced to increase wireless network coverage and to improve information transfer efficiency and reliability in intelligent transportation communication network, thus realize the high speed reliable delivery of traffic signals in intelligent transportation communication network, ensure traffic safety, improve traffic transportation efficiency, alleviate traffic congestion, improve the road network traffic capacity, reduce energy resource consumption.

Collaborative network transmission means has half-duplex transmission and full duplex transmission two kinds of modes.In half-duplex transmission mode, first stage, source node transmits a signal to via node; Second stage, via node process also forwards the signal that receives to destination node; This process is one-way communication.To complete the Signal transmissions of destination node to source node, then need two extra stages just can complete.And in full duplex transmission mode, only need two stages just can complete information interaction before source node and destination node.Two terminal nodes transmit a signal to via node simultaneously, and via node sends to Correspondent Node after carrying out certain process to the received signal; Each receiving node can the transmission information of removal from Received signal strength itself, thus decoding draws the information from Correspondent Node.Full duplex transmission improves the validity of frequency spectrum effectively, and traffic rate is approximately the twice of half-duplex operation.

Junction network (half-or full-duplex) has two kinds of traditional retransmission methods: amplification forwarding (Amplify-and-Forward, AF) and decoding forward (Decode-and-Forward, DF).

Amplification forwarding realizes the simplest a kind of collaboration protocols.Under such an arrangement, via node just simply amplifies and forwards the signal from source node received.In amplification forwarding process, the noise comprised in Received signal strength is also exaggerated.

It is the collaboration protocols more complicated than amplification forwarding that decoding forwards, and object forwards first remove noise decoding on via node after again, thus suppresses the noise enlarge-effect in amplification forwarding agreement.But the shortcoming of decoding retransmission method is once via node decoding error, can lead to errors and propagate into destination node.

Summary of the invention

In order to solve the problems referred to above of amplification forwarding and decoding forwarding existence, the invention provides a kind of estimation retransmission method of full duplex traffic cooperative communication network, its concrete technical scheme is as follows: a kind of estimation retransmission method of full duplex traffic cooperative communication network, and it comprises the following steps:

Step one, set up and form traffic cooperative communication network by multinode, each node all can be used as relay node cooperation source node transmission of signal to destination node;

After step 2, via node receive and send signal, via node adopts Unconstrained least-mean-square error algorithm to obtain the estimation Soft Inform ation sending signal;

Step 3, the transmitted power on via node to be normalized;

The Soft Inform ation obtained in step 2 is sent to destination node by step 4, via node;

After step 5, destination node receive forwarding information, adopt the spherical detection algorithm detection signal of Generalized.In multiple antennas detection technique, spherical detection algorithm is widely studied and applied because of the feature of its high-performance low complex degree.Spherical detection methods is carrying out in signal detection process, first tree structure is modeled as according to reception antenna number (being assumed to be M), root node is M element in the signal vector needing to detect, the leaf node of every one deck is the constellation point in modulation set, and every layer of every root antenna of expression sends all possible element of signal.Spherical detection methods from the root node of described tree structure, launches every one deck and tests to corresponding node, if the weighting function of this node is greater than predefined threshold value, then delete all branches and the child node thereof of this node and the generation of this node, until find leaf node after upgrading described predefined threshold value, return last layer again and continue search, finally obtain the detection signal with minimal weight function.

When reception antenna number is more than or equal to number of transmit antennas, traditional spherical detection algorithm directly can be adopted.But the system receiving terminal of introduction of the present invention is similar to the multiaerial system that reception antenna number is less than number of transmit antennas, need could use traditional spherical detection algorithm, i.e. the spherical detection algorithm of Generalized by certain mathematical operation conversion.Specific algorithm process repeats no more in the present invention.

Further, the traffic cooperative communication network described in step one is single antenna traffic cooperative communication network or multiple antennas traffic cooperative communication network.

Wherein, in step 2, the detailed process obtaining the estimation Soft Inform ation sending signal is:

Corresponding two the terminal node T of certain via node R ₁and T ₂; First time slot, two terminal node T ₁and T ₂send signal x simultaneously ₁and x ₂to via node, the signal r that via node receives is expressed as:

r＝H ₁x ₁+G ₁x ₂+n(1)

Here, H ₁and G ₁represent T respectively ₁with and T ₂and between multiple antennas or single antenna channel, n is interchannel noise.

Second time slot, via node to receive from the signal of two terminal nodes carry out process and transmission processing after signal to Correspondent Node; Via node signal process function G (r) represents, destination node T ₁and T ₂the signal received can be expressed as:

y ₁＝H ₂G(r)+n ₁(2)

y ₂＝G ₂G(r)+n ₂

Here, H ₂and G ₂represent R and T respectively ₁and R and T ₂between multiple antennas or single antenna channel, n ₁and n ₂for the noise of respective channels;

Via node adopts Unconstrained Minimum Mean Squared Error estimation, obtains the estimation Soft Inform ation sending signal:

$\begin{array}{c}\hat{r}=E(H_1{x}_1+G_1{x}_2|r)\\ =\frac{\mathrm{\Σ}(H_1{x}_1+G_1{x}_2)\exp (-\frac{\left|\right||r-H_1{x}_1-G_1{x}_2|{|}^2}{{\mathrm{\σ}}^2})}{\mathrm{\Σ}\exp (-\frac{\left|\right||r-H_1{x}_1-G_1{x}_2|{|}^2}{{\mathrm{\σ}}^2})}\end{array}---\left(3\right)$

Wherein σ ²for noise variance.

The estimation retransmission method of a kind of full duplex traffic cooperative communication network provided by the present invention, has the following advantages:

The present invention proposes a kind of retransmission method being different from amplification forwarding and decoding and forwarding.

In amplification forwarding, be directly transmitted to destination node through amplifying after via node receives signal, but be also exaggerated noise while amplifying signal, cause performance loss;

And when using decoding pass-through mode, via node first decoding detects and obtains signal, then be transmitted to destination node, the method performance is better than the former, but once decoding error, then can lead to errors propagation.

Instant invention overcomes the drawback that amplification forwarding and decoding forward, via node by forwarding a simple method of estimation value of Received signal strength to destination node, thus obtains the performance being better than amplification forwarding and decoding retransmission method, and the receiving terminal error rate reduces greatly.

Accompanying drawing explanation

Fig. 1 is full duplex traffic cooperative communication network system diagram.

Fig. 2 is that the pass-through mode of full duplex traffic cooperative communication network compares schematic diagram.

Fig. 3 is the full duplex traffic cooperative communication network model with a via node.

Embodiment

Below in conjunction with accompanying drawing and embodiments of the invention, the estimation retransmission method to a kind of full duplex traffic cooperative communication network of the present invention is described in further detail.

A kind of estimation retransmission method of full duplex traffic cooperative communication network comprises the following steps:

Step one, set up and form traffic cooperative communication network by multinode, each node all can be used as relay node cooperation source node transmission of signal to destination node;

After step 2, via node receive and send signal, via node adopts Unconstrained least-mean-square error algorithm to obtain the estimation Soft Inform ation sending signal;

Step 3, the transmitted power on via node to be normalized;

The Soft Inform ation obtained in step 2 is sent to destination node by step 4, via node;

After step 5, destination node receive forwarding information, adopt the spherical detection algorithm detection signal of Generalized.

In multiple antennas detection technique, spherical detection algorithm is widely studied and applied because of the feature of its high-performance low complex degree.Spherical detection methods is carrying out in signal detection process, first tree structure is modeled as according to reception antenna number (being assumed to be M), root node is M element in the signal vector needing to detect, the leaf node of every one deck is the constellation point in modulation set, and every layer of every root antenna of expression sends all possible element of signal.Spherical detection methods from the root node of described tree structure, launches every one deck and tests to corresponding node, if the weighting function of this node is greater than predefined threshold value, then delete all branches and the child node thereof of this node and the generation of this node, until find leaf node after upgrading described predefined threshold value, return last layer again and continue search, finally obtain the detection signal with minimal weight function.

When reception antenna number is more than or equal to number of transmit antennas, traditional spherical detection algorithm directly can be adopted.But the system receiving terminal of introduction of the present invention is similar to the multiaerial system that reception antenna number is less than number of transmit antennas, need could use traditional spherical detection algorithm, i.e. the spherical detection algorithm of Generalized by certain mathematical operation conversion.Specific algorithm process repeats no more in the present invention.

Embodiment 1:

As shown in Figure 1, in full duplex traffic cooperative communication network system, suppose have two the vehicle-mounted nodes of terminal, multiple via nodes.Two terminal nodes are by these via node exchange messages.

Below to only have the situation of a via node to be described in network, as shown in Figure 2.Suppose there are two terminal node (T ₁and T ₂), respectively there is N _t1>=1 and root N _t2>=1 antenna; Via node R represents to have N _r>=1 antenna.Two terminal nodes are by via node exchange message.First time slot, two terminal node T ₁and T ₂send signal x simultaneously ₁and x ₂to via node, then the signal r that via node receives can be expressed as:

r＝H ₁x ₁+G ₁x ₂+n⑴

Here, H ₁and G ₁represent T respectively ₁with R and T ₂and multiple antennas between R or single antenna channel, n is interchannel noise.

Second time slot, via node receives the signal from two terminal nodes, to signal carry out process and transmission processing after signal to Correspondent Node.Via node signal process function G (r) represents, and the transmitting power of suppose relay node is P _r, then send signal power need meet power limitation condition E [|| G (r) || ²]=P _r.Therefore, destination node T ₁and T ₂the signal received can be expressed as:

y ₁＝H ₂G(r)+n ₁(2)

y ₂＝G ₂G(r)+n ₂

Here, H ₂and G ₂represent R and T respectively ₁and R and T ₂between multiple antennas or single antenna channel, n ₁and n ₂for the noise of respective channels.

With reference to Fig. 3, below different pass-through modes is described.

1. amplification forwarding

Amplification forwarding is one of retransmission method the most basic in cooperative communication network, and via node is transmitted to destination node after only needing simply to amplify the signal received.Relay process function can be expressed as:

$G_{AF}\left(r\right)=\mathrm{\α}r=\sqrt{\frac{P_r}{E\[\left|\right|r|{|}^2\]}}r---\left(3\right)$

In the method, via node does not need to detect decoding process, and complexity is low, is easy to realize.But major defect is owing to being also exaggerated noise amplification forwarding signal while, thus causes performance loss.

2. decoding forwards

The performance of decoding retransmission protocol in high s/n ratio situation is obviously better than amplification forwarding.The method detects first to the received signal, afterwards detection signal is transmitted to destination node.Via node can adopt maximum likelihood detection method to detect signal, but in order to reduce process complexity, the present invention adopts Generalized spherical detection methods to obtain (herein by T ₂regard destination node as).Therefore, relay process function representation is:

$G_{DF}\left(r\right)=\sqrt{\frac{P_r}{E\[\left|\right|{\hat{x}}_1|{|}^2\]}}{\hat{x}}_1---\left(4\right)$

But the shortcoming that decoding forwards is once detect decoding error, the situation that especially communication environment signal to noise ratio is low, will lead to errors and propagate to destination node.

3. estimate to forward

The present invention proposes a kind of to estimate to forward (EF) agreement, can fully utilize the advantage of AF and DF, thus obtains the performance that entirety is better than above two kinds of protocol forward schemes.

EF contains the Soft Inform ation of uncertain information to destination node by forwarding, thus improves the reliability of forwarding information.This Soft Inform ation is estimated to obtain by being MMSE to received signal, that is:

$\begin{array}{c}\hat{r}=E(H_1{x}_1+G_1{x}_2|r)\\ =\frac{\mathrm{\Σ}(H_1{x}_1+G_1{x}_2)\exp (-\frac{\left|\right||r-H_1{x}_1-G_1{x}_2|{|}^2}{{\mathrm{\σ}}^2})}{\mathrm{\Σ}\exp (-\frac{\left|\right||r-H_1{x}_1-G_1{x}_2|{|}^2}{{\mathrm{\σ}}^2})}\end{array}---\left(5\right)$

Here, σ ²for noise variance.

Generally speaking, because the effect of traffic collaborative network via node is very crucial, especially for the transmitting-receiving node without horizon communication.The signal processing technology of via node is particularly important, and the reliability of forward signal directly affects the transmission quality of traffic signals.In addition, due to property complicated and changeable and the mobility of traffic channel, signal is disturbed with channel fading impact serious, more highlights the importance of via node forward signal in traffic cooperative communication network.

Consider traditional amplification forwarding and decoding retransmission protocol shortcoming separately, the present invention proposes to adopt and estimates that retransmission technique obtains the systematic function being better than above two kinds of retransmission methods.Via node receives the information from source node, carries out Unconstrained Minimum Mean Squared Error estimation to it, adjusts transmitting power coefficient afterwards and is transmitted to destination node.

Above-described specific embodiment; object of the present invention, technical scheme and beneficial effect are further described; be understood that; the foregoing is only specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any amendment made, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (3)

1. an estimation retransmission method for full duplex traffic cooperative communication network, it is characterized in that, it comprises the following steps:

Step one, set up and form traffic cooperative communication network by multinode, each node all can be used as via node and assists source node transmission of signal to destination node;

After step 2, via node receive and send signal, via node adopts Unconstrained least-mean-square error algorithm to obtain the estimation Soft Inform ation sending signal;

Step 3, the transmitted power on via node to be normalized;

The Soft Inform ation obtained in step 2 is sent to destination node by step 4, via node;

After step 5, destination node receive forwarding information, adopt the spherical detection algorithm detection signal of Generalized.

2. the estimation retransmission technique of full duplex traffic cooperative communication network according to claim 1, is characterized in that, the traffic cooperative communication network described in step one is single antenna traffic cooperative communication network or multiple antennas traffic cooperative communication network.

3. the estimation retransmission technique of full duplex traffic cooperative communication network according to claim 1, is characterized in that, in step 2, the detailed process obtaining the estimation Soft Inform ation sending signal is:

Corresponding two the terminal node T of certain via node R ₁and T ₂; First time slot, two terminal node T ₁and T ₂simultaneously

Send signal x ₁and x ₂to via node, the signal r that via node receives is expressed as:

r＝H ₁x ₁+G ₁x ₂+n(1)

Here, H ₁and G ₁represent T respectively ₁with R and T ₂and multiple antennas between R or single antenna channel, n is interchannel noise.

Second time slot, via node to receive from the signal of two terminal nodes carry out process and transmission processing after signal to Correspondent Node; Via node signal process function G (r) represents, destination node T ₁and T ₂the signal received can be expressed as:

$\begin{array}{c}{y}_1=H_{2}G\left(r\right)+n_1\\ y_2=H_{2}G\left(r\right)+n_2\end{array}---\left(2\right)$

Here, H ₂and G ₂represent R and T respectively ₁and R and T ₂between multiple antennas or single antenna channel, n ₁and n ₂for the noise of respective channels;

Via node adopts Unconstrained Minimum Mean Squared Error estimation, obtains the estimation Soft Inform ation sending signal:

$\begin{array}{c}\hat{r}=E(H_1{x}_1+G_1{x}_2|r)\\ =\frac{\mathrm{\Σ}(H_1{x}_1+G_1{x}_2)\exp (-\frac{\left|\right||r-H_1{x}_1-G_1{x}_2|{|}^2}{{\mathrm{\σ}}^2})}{\mathrm{\Σ}\exp (-\frac{\left|\right||r-H_1{x}_1-G_1{x}_2|{|}^2}{{\mathrm{\σ}}^2})}\end{array}---\left(3\right)$

Wherein σ ²for noise variance.