CN101790218B - Distributed relay selection method and device - Google Patents

Abstract

The invention relates to a distributed relay selection method, wherein a relay node participating in cooperative transmission is selected at least from one relay node, and a selection flow comprises the steps that: each relay node respectively estimates the channel state information of a forward link and a backward link of per se; each relay node calculates per se channel quality according to thechannel state information and compares the channel quality obtained from the calculation with a judging threshold; when the channel quality is larger than the threshold value, the relay node is confirmed to participate in the cooperative transmission and sets the timing internal of a per se timer to be a universal time value, wherein the universal time value is smaller than a preset time value; or else, the relay node is confirmed not to participate in the cooperative transmission and sets the timing interval of the per se timer to be a time value larger than the preset time value. The invention also relates to a relay selection device. The invention is suitable for the relay selection in a multi-relay wireless cooperative transmission network, and through distributed selection means, theinvention can effectively reduce the complexity in the process of the relay selection while not lowering the system performance, thereby improving the integral system performance.

Description

Distributed relay system of selection and device

Technical field

The present invention relates to many relayings cooperation transmission technology, relate in particular to a kind of distributed relay system of selection and relay selection device.

Background technology

Along with development of wireless communication devices, the cooperation transmission technology has obtained using widely, can provide data service more reliable, more at a high speed in bigger cell coverage area.At third generation partner program (3rd Generation Partnership Project, abbreviation 3GPP) Long Term Evolution (the Long Term Evolution Advance that starts, abbreviation LTE-A) in the research, cooperation transmission (Cooperative Communication) technology has obtained widely discussing, and as one of alternative technique of next generation mobile communication.

When cooperative transmission system comprised a plurality of via node, because that the via node number in the network changes often is unknowable, this bring difficulty can for cooperation transmission criterion reasonable in design.Simultaneously, because the existence of many via nodes makes it is not that each via node can both improve transmission performance.Therefore select one or several wherein optimum via node to participate in cooperation transmission, can reduce all via nodes and all participate in the complexity issue that cooperates and bring, keep high collaboration diversity gain simultaneously.

In present cooperative transmission system, adopt the centralized relay selection method powerful main controlled node that needs to attach troops to a unit in the network, this main controlled node that is chosen in of relaying is finished, and this main controlled node is informed the corresponding state of each via node by feedback.This mode not only needs main controlled node to obtain complete channel condition information, needs feedback channel that selection result is informed each via node simultaneously, thereby has increased the complexity that system realizes.

Summary of the invention

The objective of the invention is to propose a kind of distributed relay system of selection and device, can in each via node, finish the process of relay selection, and the selection of via node no longer is to select single node, and all satisfy relayings of selecting to require can participate in cooperation transmission.

For achieving the above object, the invention provides a kind of distributed relay system of selection, select to participate in the via node of cooperation transmission at least one via node, described selection flow process comprises:

Each via node in described at least one via node is estimated the forward link and the channel condition information of back to link of self respectively;

Each via node calculates the channel quality of self according to described channel condition information, and channel quality and the decision threshold that calculates compared;

If described channel quality is greater than threshold value, then described via node is determined to participate in cooperation transmission, and the fixed time interval that the timer of self is set is value unified time, and be worth less than the Preset Time value described unified time; Otherwise described via node is determined not participate in cooperation transmission, and the fixed time interval that the timer of self is set is the time value greater than the Preset Time value.

For achieving the above object, the invention provides a kind of relay selection device, be arranged in the via node, comprising:

The channel status estimation module is for the forward link of estimating described via node self respectively and the channel condition information of back to link;

The channel quality computing module is for the channel quality that calculates described via node self according to described channel condition information;

The thresholding comparison module, the channel quality and the decision threshold that are used for calculating compare;

Fixed time interval arranges module, be used for when judging described channel quality greater than threshold value, determine that then described via node participates in cooperation transmission, and the fixed time interval that the timer of described via node self is set is value unified time, be worth less than the Preset Time value described unified time; Otherwise determine that described via node does not participate in cooperation transmission, and the fixed time interval that the timer of described via node self is set is the time value greater than the Preset Time value.

Based on technique scheme, the present invention is applicable to the relay selection of many relay wireless cooperation transmission network, by distributed selection approach, and can be when not reducing systematic function, effectively reduce the complexity of relay selection process, thereby improve the entire system performance.

Description of drawings

Accompanying drawing described herein is used to provide further understanding of the present invention, constitutes the application's a part, and illustrative examples of the present invention and explanation thereof are used for explaining the present invention, do not constitute improper restriction of the present invention.In the accompanying drawings:

Fig. 1 is the application scenarios schematic diagram of distributed relay system of selection embodiment of the present invention.

Fig. 2 is the schematic flow sheet of an embodiment of distributed relay system of selection of the present invention.

Fig. 3 is the schematic flow sheet of another embodiment of distributed relay system of selection of the present invention.

Fig. 4 is the structural representation of an embodiment of distributed relay choice device of the present invention.

Embodiment

Below by drawings and Examples, technical scheme of the present invention is described in further detail.

Consider the complexity that centralized relay selection method can the increase system realizes, the present invention meets at each via node with the process of relay selection and finishes in wireless many relayings cooperation transmission network, so just need in network, not dispose powerful main controlled node, and the message transmission between processing main controlled node and other via node, carry out adaptive selection by each via node according to self channel condition information, reduced the complexity that system realizes.

The application scenarios of this distributed relay system of selection can be as shown in Figure 1, and S is source node in Fig. 1, and D is destination node, and R is via node, through after the relay selection,

Identify selecteed via node,

Represent non-selected via node.Source node sends to destination node by selecteed via node with information.

As shown in Figure 2, be the schematic flow sheet of an embodiment of distributed relay system of selection of the present invention.In the present embodiment, need participate in the via node of cooperation transmission from least one trunk node selection, this distributed relay selects flow process to comprise:

Each via node in step 101, described at least one via node is estimated forward link and the back channel condition information to link of self respectively;

Step 102, each via node calculate the channel quality of self according to described channel condition information, and channel quality and the decision threshold that calculates compared;

If the described channel quality of step 103 is greater than threshold value, then execution in step 104, otherwise execution in step 105;

Step 104, described via node are determined to participate in cooperation transmission, and the fixed time interval that the timer of self is set is value unified time, and be worth less than the Preset Time value described unified time;

Step 105, described via node are determined not participate in cooperation transmission, and the fixed time interval that the timer of self is set is the time value greater than the Preset Time value.

In the present embodiment, each via node all needs to estimate separately the forward link and the channel condition information of back to link of self, and assess, judging whether to meet the condition that participates in cooperation transmission, this condition is as foundation with the value of relatively channel quality and decision threshold.

Each via node is set the timer of self according to judged result, if participation cooperation transmission, then set short unified fixed time interval, because all carrying out data when timer expiry, transmits each via node, so just can make each via node that participates in cooperation transmission carry out data in the same time early transmits, and the via node that does not participate in cooperation transmission is set at long fixed time interval, when behind this sign off, the timer of all via nodes all can be reset in zero clearing, thereby the via node that does not participate in cooperation transmission can not carry out data to be transmitted, thereby guarantees can not interfere with the cooperation transmission process.

When each via node carries out the estimation of channel condition information, can be sent the pilot signal (with pilot frequency sequence as pilot signal) of quadrature by source node S and destination node D respectively, assist via node to obtain corresponding channel condition information, the channel condition information of each via node forward link can directly calculate in this process, then the channel condition information to link can not directly obtain, can utilize the up-downgoing reciprocity of TDD cooperative transmission system in the present invention, think that the channel condition information that via node arrives destination node can replace with the channel condition information of destination node to via node.

In the present embodiment, the calculating of decision threshold is relevant with the via node position with the type of service of transmission, can judge the requirement of system signal noise ratio according to type of service, and according to via node position introducing relaying coefficient correlation, this relaying coefficient correlation and signal to noise ratio are formed this default decision threshold jointly.

Below by a specific embodiment distributed relay system of selection of the present invention is described, as shown in Figure 3, be the schematic flow sheet of another embodiment of distributed relay system of selection of the present invention.For simplicity, all the suppose relay node can obtain corresponding channel condition information according to the existing channel algorithm for estimating in the following discussion, but the personnel with common communications technical background will be appreciated that, any effective channel estimation method all can be used for the method, so this hypothesis should not play improper restriction to this patent right.

Suppose to comprise in the collaborative network source node (S), a destination node (D) and K via node (R).The signal that source node sends is x.Like this, the reception signal at each via node place is

$y_i=\sqrt{P_s}{h}_{s,i}x+n_i,i=1,\·\·\·,K---\left(1\right)$

Wherein, P _sBe the transmitted power of source node, h _{S, i}Be that source node is to the channel condition information of via node, n _iIt is the additive white Gaussian noise at via node place.If there be m node selected, then the reception signal at destination node place can be expressed as

$y_d=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\frac{\sqrt{P_s}\sqrt{P_i}{h}_{s,i}{h}_{i,d}s}{\sqrt{P_s{\left|h_{s,i}\right|}^2+N_0}}+\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\frac{\sqrt{P_i}{h}_{i,d}{n}_i}{\sqrt{P_s{\left|h_{s,i}\right|}^2+N_0}}+n_d---\left(2\right)$

Wherein, P _iBe the transmitted power of via node, h _{I, d}Be the channel condition information that via node arrives destination node, n _dBe the additive white Gaussian noise at destination node place, N ₀Be the additive white Gaussian noise variance.

The step of the embodiment of the invention is as follows:

Step 201, source node and destination node send the pilot signal of quadrature respectively.

Each via node R of step 202, a K via node carries out channel estimating to the pilot signal that listens to, and estimates that source node is to via node (the channel condition information h of S → R) _{S, i}With via node to destination node (the channel condition information h of R → D) _{I, d}, wherein obtain S to the channel condition information h of i R by via node R by the pilot signal of monitoring S → R _{S, i}, obtain D to the channel condition information h of i R by via node R by the pilot signal of monitoring D → R _{D, i}, the up-downgoing reciprocity of recycling TDD cooperative transmission system obtains the channel condition information h of R → D _{I, d}, this formula is h _{I, d}=h _{D, i}

Step 203, calculate the value of decision threshold, comprising two parts: the error rate BER that need be satisfied by the type of service of transmission obtains the signal to noise ratio snr value; Those skilled in the art selects relaying coefficient correlation Cor flexibly according to the via node position.Be without loss of generality, suppose BER and SNR corresponding relation can by

$\mathrm{BER}=Q\left\{\sqrt{2\·\mathrm{SNR}}\right\}---\left(3\right)$

Wherein, $Q\left(x\right)=\underset{x}{\overset{+\&infin;}{\&Integral;}}\frac{1}{\sqrt{2\mathrm{\&pi;}}}\exp (-\frac{{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HSA00000008529900032.png"\; state="\{\{state\}\}">y</figure-callout>}}^2}{2})\mathrm{dy},$ Their corresponding relation can be tabled look-up and be tried to achieve.The computing formula of last decision threshold can be defined as

Th＝Cor×SNR (4)

Step 204, each via node calculate channel quality respectively according to the channel quality function, namely

$q_i\left(i\right)=\frac{P_s{\left|h_{s,i}\right|}^2\&times;P_r{\left|h_{i,d}\right|}^2}{P_s{\left|h_{s,i}\right|}^2+P_r{\left|h_{i,d}\right|}^2+1}---\left(5\right)$

Q wherein _i(i) be the channel quality of i via node R.

Step 205, each via node compare channel quality and the decision threshold that calculates, and the node that participates in cooperation transmission should satisfy

$m^{*}=\underset{m\&Element;\{1,...,K\}}{\arg }(q_i>\mathrm{Th})---\left(6\right)$

Step 206, according to judged result, determine whether each via node participates in cooperation transmission, and then the fixed time interval of timer be set for each via node.

$t_i=\left\{\begin{array}{cc}T,& q_i>\mathrm{Th}\\ T+T_{\mathrm{frame}}\&CenterDot;\frac{\mathrm{Th}}{q\left(i\right)},& q_i\&le;\mathrm{Th}\end{array}\right.---\left(7\right)$

Here T is the time value (being a constant) of systematic unity, T _FrameIt is the time of frame transmission.For the via node that participates in cooperation transmission, fixed time interval is set as unified time value T, this time value T＜T _FrameFor the via node that does not participate in cooperation transmission, fixed time interval is set to

This value is greater than T _Frame

Step 207: each via node starts timer, carry out countdown, at first the via node of countdown end (during timer expiry) begins to transmit data, because the fixed time interval of the via node of participation cooperation transmission is shorter, and be set to unified time, therefore can transmit prior to other the via node data of carrying out simultaneously, via nodes all behind this sign off are all reset to the timer zero clearing of self.And therefore the via node that has neither part nor lot in cooperation transmission, all can't be transmitted data, thereby avoid the communication process of via node to cause confusion owing to the time that is provided with greater than a frame before this sign off, brought interference for normal cooperation transmission.

The present invention selects via node to participate in cooperation transmission by adopting distributed relay selection method, on the basis that does not influence systematic function, greatly reduces the complexity that selection course realizes.And can select one or more via nodes flexibly, take full advantage of the via node that distributes in the system, thereby effectively raise the reliability of system.

One of ordinary skill in the art will appreciate that: all or part of step that realizes said method embodiment can be finished by the relevant hardware of program command, aforesaid program can be stored in the computer read/write memory medium, this program is carried out the step that comprises said method embodiment when carrying out; And aforesaid storage medium comprises: various media that can be program code stored such as ROM, RAM, magnetic disc or CD.

Fig. 4 is the structural representation of an embodiment of distributed relay choice device of the present invention.In the present embodiment, the relay selection device can be arranged at and carry out distributed relay selection in all via nodes, and this relay selection device comprises: channel status estimation module 1, channel quality computing module 2, thresholding comparison module 3 and fixed time interval arrange module 4.Wherein channel status estimation module 1 is used for estimating respectively the forward link and the channel condition information of back to link of described via node self.Channel quality computing module 2 is used for calculating according to described channel condition information the channel quality of described via node self.Channel quality and decision threshold that thresholding comparison module 3 is used for calculating compare.Fixed time interval arranges module 4 and is used for when judging described channel quality greater than threshold value, determine that then described via node participates in cooperation transmission, and the fixed time interval that the timer of described via node self is set is value unified time, and described unified time, value was less than the Preset Time value; Otherwise determine that described via node does not participate in cooperation transmission, and the fixed time interval that the timer of described via node self is set is the time value greater than the Preset Time value.

Should be noted that at last: above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit; Although with reference to preferred embodiment the present invention is had been described in detail, those of ordinary skill in the field are to be understood that: still can make amendment or the part technical characterictic is equal to replacement the specific embodiment of the present invention; And not breaking away from the spirit of technical solution of the present invention, it all should be encompassed in the middle of the technical scheme scope that the present invention asks for protection.

Claims (9)

1. distributed relay system of selection, selection participates in the via node of cooperation transmission at least one via node, and described selection flow process comprises:

Each via node in described at least one via node is estimated the forward link and the channel condition information of back to link of self respectively;

Each via node calculates the channel quality of self according to described channel condition information, and channel quality and the decision threshold that calculates compared;

If described channel quality is greater than threshold value, then described via node is determined to participate in cooperation transmission, and the fixed time interval that the timer of self is set is value unified time, and be worth less than the Preset Time value described unified time; Otherwise described via node is determined not participate in cooperation transmission, and the fixed time interval that the timer of self is set is the time value greater than the Preset Time value;

Wherein, described decision threshold is relevant with the via node position with the type of service of transmission, and the step of calculating described decision threshold comprises:

Judge the requirement of system signal noise ratio according to the type of service of described transmission, and introduce the relaying coefficient correlation according to described via node position, requirement and the relaying coefficient correlation according to described signal to noise ratio obtains decision threshold then.

2. according to the described distributed relay system of selection of claim l, each via node of wherein said at least one via node estimates that respectively the forward link of self and the operation of back to the channel condition information of link are specially:

Source node S and destination node D send the pilot signal of quadrature respectively;

Each via node R of K via node carries out channel estimating to the pilot signal that listens to, and estimates that source node is to the channel condition information h of via node _{S, i}And via node is to the channel condition information h of destination node _{I, d}

3. distributed relay system of selection according to claim 2, wherein said via node is to the channel condition information h of destination node _{I, d}Reciprocity formula h by the TDD cooperative transmission system _{I, d}=h _{D, i}Obtain, wherein channel condition information _{D, i}Obtain by the pilot signal of monitoring destination node to via node.

4. distributed relay system of selection according to claim 1, the computing formula of wherein said decision threshold is Th=Cor * SNR, wherein relaying coefficient correlation Cor is obtained by described via node position, and signal to noise ratio snr is by the corresponding relation of error rate BER and signal to noise ratio snr $\mathrm{BER}=Q\left(\sqrt{2\&CenterDot;\mathrm{SNR}}\right)$ Calculate, wherein $Q\left(x\right)=\underset{x}{\overset{+\&infin;}{\&Integral;}}\frac{1}{\sqrt{2\mathrm{\&pi;}}}\exp (-\frac{y^2}{2})\mathrm{dy}.$

5. distributed relay system of selection according to claim 3, the computing formula of wherein said channel quality is:

$q_i\left(i\right)=\frac{P_s{\left|h_{s,i}\right|}^2\&times;P_r{\left|h_{i,d}\right|}^2}{P_s{\left|h_{s,i}\right|}^2+P_r{\left|h_{i,d}\right|}^2+1},$

Q wherein _i(i) be the channel quality of i via node R, P _sBe the transmitted power of source node S, P _rTransmitting power for via node.

6. distributed relay system of selection according to claim 1, wherein said Preset Time value is the transmission time of a frame.

7. distributed relay system of selection according to claim 6, wherein after each via node arranges the fixed time interval of timer of self, start timer, and transmit data during the Chi timer expiry, described at least one via node behind this sign off all the timer zero clearing to self reset.

8. distributed relay system of selection according to claim 7 wherein arranges the fixed time interval of timer according to following formula for each via node, and this formula is:

$t_i=\left\{\begin{array}{cc}T,& q_i\left(i\right)>\mathrm{Th}\\ T+T_{\mathrm{frame}}\&CenterDot;\frac{\mathrm{Th}}{q_i\left(i\right)},& q_i\left(i\right)\&le;\mathrm{Th}\end{array}\right.$

Wherein T is value unified time, T _FrameBe the transmission time of a frame, Th is decision threshold, q _i(i) be the trunk channel quality of i via node R.

9. a relay selection device is arranged in the via node, comprising:

The channel status estimation module is for the forward link of estimating described via node self respectively and the channel condition information of back to link;

The channel quality computing module is for the channel quality that calculates described via node self according to described channel condition information;

The thresholding comparison module, the channel quality and the decision threshold that are used for calculating compare;

Fixed time interval arranges module, be used for when judging described channel quality greater than threshold value, determine that then described via node participates in cooperation transmission, and the fixed time interval that the timer of described via node self is set is value unified time, be worth less than the Preset Time value described unified time; Otherwise determine that described via node does not participate in cooperation transmission, and the fixed time interval that the timer of described via node self is set is the time value greater than the Preset Time value;

Wherein, described decision threshold is relevant with the via node position with the type of service of transmission, and the step of calculating described decision threshold comprises:

Judge the requirement of system signal noise ratio according to the type of service of described transmission, and introduce the relaying coefficient correlation according to described via node position, requirement and the relaying coefficient correlation according to described signal to noise ratio obtains decision threshold then.

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