CN101557630A - Method for selecting cooperative nodes in wireless communication network - Google Patents

Abstract

The invention discloses a method for selecting cooperative nodes in a wireless communication network, which can effectively improve cooperative diversity performance as well as the transmission capacity and reliability of the wireless communication system and ensure the requirement of the quality of service (QoS) of users. The method comprises the following steps: (1) an information source S sends relay requests to nodes around; (2) if the nodes are in leisure, a response signal is sent, and if no leisure node exists, the step (1) is continued; (3) if only one leisure node exists, the operation is switched into the step (6), and an AF or DF cooperative mode is directly adopted; (4) if a plurality of leisure nodes exist, the information source S calculates the distance L between the information source S and the leisure nodes according to the strength of a utilization signal, time difference, angle or GPS information, and then the leisure nodes send information to a target terminal, calculate the distance D between the leisure nodes and the target terminal according to the signal strength, the time difference, the angle or the GPS information and feed back the distance to the information source S; (5) the leisure node with the minimum product of the distance L and the distance D is selected as an optimum relay node; and (6) finally the system adopts the AF or DF cooperative mode.

Description

Method for selecting cooperative nodes in a kind of cordless communication network

Technical field:

The present invention relates to method for selecting cooperative nodes in the cordless communication network, belong to wireless communication technology field.

Background technology:

Along with the development of cordless communication network technology, various wireless communication technologys occur in succession, and this just makes available frequency spectrum resource day hasten towards saturation.Yet people are still improving constantly the requirement of wireless communication system, and the wireless communication technology that a kind of transmission rate is higher, cost is lower, power is littler, antijamming capability is stronger appears in expectation.Yet, need carry out diversity at transmitting terminal usually in order to improve the performance of wireless network communications system.And the transmit diversity in the radio communication generally need use many antennas at transmitting terminal, but many wireless devices have only single antenna usually because of being subjected to the restriction of size or hardware complexity.For this reason, the expert has proposed a kind of new solution---communication for coordination.This method is used the travelling carriage that has an antenna, can share other mobile subscribers' antenna in multi-user environment, can produce many virtual transmitting antennas like this, and then obtain corresponding diversity gain, improves the performance of wireless network communications system.

Communication for coordination is a kind of novel diversity technique in the wireless network, and it can improve throughput, reduce transmitted power and to anti-fading.Because it has distributed nature, can make network become quite simple, and can make a single aerial system have the advantage of many antennas.Compare with non-communication for coordination simultaneously, the collaborative user can increase data rate and reduce sensitivity to channel variation.The collaborative data rate that increases can be converted into the transmitted power that reduces the user, that is to say, compare with non-collaborative system, the gross power that the user in the cooperative system needs with equivalent data rates transmission data the time has reduced, and therefore can prolong the life-span of battery of mobile terminal.

The basic thought of communication for coordination is that each portable terminal in the system all has one or more affiliates, has a responsibility between the affiliate helping its partner to transmit information in the own information of transmission.Like this, each terminal has not only been utilized oneself but also has utilized affiliate's space channel in the process of transmission information, thereby has obtained certain space diversity gain.Describe the basic thought of communication for coordination in detail at this.As Fig. 1.

Terminal S and R send information to D and M respectively, show that two terminals in the wireless network terminal are with their message transmission to two destination.For example, in cellular network, S and R are portable terminals, and D and M are same equipment, the expression destination.Why radio communication can support collaboration diversity, is the broadcast characteristic because of wireless medium, and in principle, the signal that is sent out can be received by any other terminal and handle.Like this, except the signal independent transmission being arrived destination separately, S and R can also monitor transmission separately mutually, thus their information of joint transmission.So just can realize communication for coordination.

An extreme case is exactly the wireless relay channel, and this moment, D and M were same equipment, and transmission terminal R can contribute the information of its all resources (as power and bandwidth etc.) transmission S.In this case, S is exactly an information source, and D plays the part of relaying, Here it is famous trunk channel.Here in fact we be exactly this trunk channel that adopts, and do not help each other.This mode provides diversity, because even the channel quality between S and D is very poor, information also may successfully be transmitted by R.Equally, S also can be used as the information that relaying transmits R, thereby becomes another kind of wireless relay channel.According to the collaborative strategy of relaying, it is simple amplification message signal both, also can decipher recompile then, sends to destination again.These two strategies are exactly to amplify forward pass AF (amplify-forward) and decoding forward pass DF (decode-forward), and they also can be used for cooperative diversity system.

At this AF and DF are described in detail.

The basic principle of AF is: the AF strategy is the analog junction strategy usually again, and relaying amplifies earlier to received signal, then retransmits, and it also is a kind of strategy that still has noise amplification characteristics based on duplication code.The x ' that transmits at via node place ₂Be y in the phase I ₂Amplification after institute's picked up signal, i.e. x ' ₂=β y ₂=β (h ₂₁x ₁+ n ₂₁).Under the constraint that waits transmitting power, amplification coefficient is $\mathrm{\&beta;}=\frac{1}{\sqrt{{\left|h_{21}\right|}^2+{{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="A20091001998100072.png,A20091001998100073.png"\; state="\{\{state\}\}">n</figure-callout>}}}^2}},$ H wherein ₂₁Be the characteristic of channel, σ _n ²It is the noise power of channel.In the second stage, only the received signal of destination node is y ' under the strategy of repeat transmitted signal ₃=h ₃₂X ' ₂+ n ₃₂The received signal vector of destination node in two stages is $\left[\begin{array}{c}{y}_3\\ {\mathrm{<figure-callout\; id="3"\; label="y"\; filenames="A20091001998100072.png,A20091001998100073.png"\; state="\{\{state\}\}">y</figure-callout>}}_3^{\&prime;}\end{array}\right]=\left[\begin{array}{c}{h}_{31}\\ {\mathrm{\&beta;h}}_{21}{h}_{32}\end{array}\right]x_1+\left[\begin{array}{c}{n}_{31}\\ {\mathrm{\&beta;h}}_{32}{n}_{21}+n_{32}\end{array}\right].$ In destination node, normally adopt high specific to merge (MRC) and draw information.The following Fig. 2 of its key diagram, 1 the representative be information source, 2 the representative be via node, 3 the representative be destination.x ₁The information of indicating to transmit, y ₂Be through the relaying received signal after the channel 1-2.x ₂The signal after via node amplifies of expression.h _IjWhat represent is the characteristic of channel of j to i.n _IjWhat represent is the channel noise power of j to i.y ₃What represent is that destination directly receives the information from information source.Y ' ₃What represent is that destination receives from relayed information.

The basic principle of DF: the DF strategy digital junction strategy that is otherwise known as usually, it is divided into fixing and adaptive version again.Here consider mainly that the relaying place adopts the design of simple duplication code, the x ' that transmits at its via node place ₂Be the x that transmits ₁Estimation.Under basic DF strategy, node 1 was broadcasted to node 2,3 in the collaborative phase I, at collaborative second stage node 2 x ' that transmits ₂The signal that (be need before node 2 emission to decipher, signal processing such as recodification) and node 3 merge from two paths.Under the hypothesis in front, the received signal of node 2 and node 3 is respectively y in the phase I ₂=h ₂₁x ₁+ n ₂₁And y ₃=h ₃₁x ₁+ n ₃₁, node 3 received signals are y in the second stage ₃=h ₃₂X ' ₂+ n ₃₂At via node place correct decoding (is its x ' that transmits ₂Equal x ₂) time, the received signal vector of destination node in two stages is $\left[\begin{array}{c}{y}_3\\ {\mathrm{<figure-callout\; id="3"\; label="y"\; filenames="A20091001998100072.png,A20091001998100073.png"\; state="\{\{state\}\}">y</figure-callout>}}_3^{\&prime;}\end{array}\right]=\left[\begin{array}{c}{h}_{31}\\ h_{32}\end{array}\right]x_1+\left[\begin{array}{c}{n}_{31}\\ n_{32}\end{array}\right].$ In destination node, utilize high specific to merge (MRC) and draw information.The destination node that makes this diversity Merge Scenarios has realized the received signal to noise ratio addition of two independent channels.But only its is just transmitted to destination under the correct condition of codeword decoding when the relaying node is launched information source in the DF strategy, and otherwise via node will stop emission.Figure is as accompanying drawing 3, wherein x ₁The information that the information source of indicating will send, x ' ₂Be the information after via node is recoded through decoding.h _IjWhat represent is the characteristic of channel of j to i.n _IjWhat represent is the channel noise power of j to i.y ₃What represent is that destination directly receives the information from information source.Y ' ₃What represent is that destination receives from relayed information.

The collaborative strategy of above-mentioned two kinds of relayings introducing we can be called be that two kinds of common trunking scheme: AF are non-regenerative relaying; DF is a regenerative repeating.Owing in wireless network, utilize relaying to transmit and to improve system transmission capacity and reliability effectively.Therefore how many in recent years scholars select the problem of via node in research.The communication mode of each node as shown in Figure 4 in wireless network.Information source is that various possible message conversion are become raw electrical signal.By transmitting apparatus primary signal is finished certain conversion then, carrying out the selection problem of optimal relay node this moment.Chosen optimal relay node, the signal channel that comes out through transmitting apparatus sends to destination and optimal relay node simultaneously.The cooperative mode of taking this moment can be to amplify forward pass (AF), decoding forward pass (DF) and coding cooperation modes such as (CC).At receiving terminal, signal is deciphered the process of demodulation, then multiple signals is carried out high specific and merges or equal gain combining.Recover corresponding information at last.In wireless network, the number of relaying can extend to a plurality of, forms distributed aerial array.Make the relaying contract network bring into play its maximum utility and be unable to do without relay management and distribution.The research of relay management mainly concentrates on two aspects: relay selection and power division.Relay selection is meant how select one or several relaying to be used for auxiliary transmission in numerous relayings.The selection strategy of via node is mainly based on following several category informations at present: physical distance, path loss and instantaneous channel status.Choose reasonable can improve problems such as error rate of system performance.A kind of selection mode of via node has here been proposed according to physical distance and path loss.

Summary of the invention:

The objective of the invention is to be method for selecting cooperative nodes in the cordless communication network that a kind of feasible low complex degree is provided based on collaborative wireless network, can improve the collaboration diversity performance effectively, thereby improve wireless communication system transmission capacity and reliability, ensure user's qos requirement.

For achieving the above object, the present invention adopts following technical scheme:

Method for selecting cooperative nodes in a kind of cordless communication network, the product L*D that in contiguous all idle node, selects the distance D of the distance L of information source and idle node and idle node and destination be that node of minimum as optimal relay node, concrete steps are:

1) information source becomes raw electrical signal with various possible message conversion;

2) raw electrical signal carries out conversion through transmitting apparatus;

3) carry out the selection (concrete steps are as follows) of optimal relay node this moment:

1. information source S towards periphery node send relay request;

If 2. node free time then send answer signal; If there is not idle node, then continue step 1.;

3. iff an idle node, then change step 4) over to, directly take AF or DF cooperative mode;

4. if there are a plurality of idle node, information source S can go out distance L with these idle node according to signal strength signal intensity, time difference, angle or GPS information calculations; Idle node sends message to destination then, the same distance D that goes out between the two according to signal strength signal intensity, time difference, angle or GPS information calculations, and this distance fed back to information source S;

5. select to make the optimal relay node of that idle node of distance L and D product minimum as us;

4) chosen after the optimal relay node, the cooperative mode according to system adopts AF or DF carries out communication for coordination;

5) each road signal is deciphered demodulation through receiving terminal;

6) utilize maximum each the road signal of comparison that merges to merge then, recover corresponding information;

Described cooperative mode is AF cooperative mode or DF cooperative mode.

The cooperative mode that the present invention realizes on wireless communication network system.Key is the problem of how selecting for via node: the product (L*D) of the distance D of the distance L of selection information source and relaying and relaying and destination is the optimal relay node of that idle relay node of minimum as us in contiguous all via nodes.

The invention has the beneficial effects as follows: make full use of the spatial domain resource, avoided the collision of other via node simultaneously.Thereby improve channel capacity, the transmission quality of system, the reduction error rate of radio communication significantly.

Description of drawings:

Fig. 1 is the schematic diagram of cooperative mode;

The key diagram of the collaborative tactful AF of Fig. 2 relaying;

The key diagram of the collaborative tactful DF of Fig. 3 relaying;

The part flow chart of the communication for coordination that Fig. 4 carries out on wireless communication system;

The particular flow sheet of Fig. 5 relay selection of the present invention.

Wherein, 1. information source, 2. via node, 3. destination,

Embodiment:

Contrasting the present invention below in conjunction with accompanying drawing and embodiment is described further.

Among Fig. 5, method for selecting cooperative nodes in a kind of cordless communication network:

The product L*D that in contiguous all idle node, selects the distance D of the distance L of information source and idle node and idle node and destination be that node of minimum as optimal relay node, concrete steps are:

1) information source S node transmission towards periphery relay request;

2) if node free time then send answer signal; If there is not idle node, then continue step 1);

3) iff an idle node, then change step 6) over to, directly take the cooperative mode of AF or DF;

4) if there are a plurality of idle node, information source S can be according to the distance L that connects signal strength signal intensity, time difference, angle or GPS information calculations and these idle node; Idle node sends message to destination then, the same distance D that goes out between the two according to signal strength signal intensity, time difference, angle or GPS information calculations, and this distance fed back to information source S;

5) select to make that idle node of distance L and D product minimum as optimal relay node;

6) adopt AF or DF mode to carry out communication for coordination according to system at last.

Described cooperative mode is AF cooperative mode or DF cooperative mode.

Claims (2)

1. method for selecting cooperative nodes in the cordless communication network, it is characterized in that, the product L*D that in contiguous all idle node, selects the distance D of the distance L of information source and idle node and idle node and destination be that node of minimum as optimal relay node, concrete steps are:

1) information source S node transmission towards periphery relay request;

2) if node free time then send answer signal; If there is not idle node, then continue step 1);

3) iff an idle node, then change step 6) over to, directly take AF or the communication of DF cooperative mode;

4) if there are a plurality of idle node, information source S can be according to the distance L of signal strength signal intensity, time difference, angle or GPS information calculations and these idle node; Idle node sends message to destination then, the same distance D that goes out between the two according to signal strength signal intensity, time difference, angle or GPS information calculations, and this distance fed back to information source S;

5) select to make that idle node of distance L and D product minimum as optimal relay node;

6) final system adopts AF or the communication for coordination of DF mode.

2. method for selecting cooperative nodes in the cordless communication network as claimed in claim 1 is characterized in that, described cooperative mode is AF cooperative mode or DF cooperative mode.

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