CN102202382A - Relay selection method for reducing transmitting power - Google Patents

Abstract

The invention discloses a relay selection method for reducing transmitting power. The method comprises the following specific steps: a source node firstly sends a RTS (request to send) message; a relay point received the RTS message carries out a channel estimation according to the information and obtains channel status information between the source node and the relay point; each relay point sends a CTS (clear to send) message to the control source node; when the control source node receives the CTS message, the control source node selects a relay for transmitting the information to each source node according to the content of the CTS message through using the designed algorithm; then the control source node informs each source node of the selected result in message mode; the relay receives the RTC message and then responses the CTC message; and after the source node receives the CTC message, the source node formally sends a message through collaborating with the relay node. The selection method provided by the invention is relatively simple and can reduce the transmitting power of the system to a great extent.

Description

A kind of relay selection method that reduces transmitting power

Technical field

The present invention relates to wireless communication field, be specially a kind of relay selection method that can reduce transmitting power.This method is used for radio communication, solves how to select repeater, can reduce the strategy that transmitting power is carried out the signal transmission.

Background technology

The use of digital repeater is general day by day in the radio communication at present, and it can enlarge the area coverage of new generation of wireless communication system, improves communication quality.Usually, can lay a plurality of repeaters dispersedly around a base station.Present wireless network uses all repeaters in coverage to participate in transmitting mostly, but because the randomness of wireless channel is not the forwarding that each repeater all is necessary to participate in signal.Simultaneously, the digital repeater in the cordless communication network needs power supply power supply, and the part repeater is owing to lay the position and limit and can only lean on powered battery.Therefore, under the prerequisite that guarantees proper communication, reduce the quantity and the transmitting power of repeater, positive effect with energy savings.

In the scope of applicant's retrieval, following document is related to the present invention, is suitable for doing background technology of the present invention:

[1] Qu Chunhe etc. according to Mathematical Modeling and bit error rate formula, has proposed a kind of partner node selection algorithm in its " at the distributed partner node selection algorithm of decoding forward collaboration diversity " (referring to " Chinese journal of computers ", in April, 2010) literary composition.This algorithm can be with minimum control protocol expense in distributed wireless network environment, and message ground selects optimum partner node to participate in transmitting message one by one.Moreover, this algorithm can also be adjusted selected partner node along with the change dynamics ground of channel status, so channel status is had adaptive ability.What but this method did not have taking into account system integral body carries out control problem to power, is therefore saving energy, is reducing aspect the radiation defective to some extent.

[2] favour Marsha etc. is in its " a kind of distributed power of multi-source collaborative network distributes and the relay selection algorithm " (referring to " electronics and information journal " in October, 2010) literary composition, at multi-source-many relayings amplification forward collaboration communication network, proposed a kind of distributed power and distributed and the relay selection algorithm.This algorithm independently is chosen as the via node of its forwarding information by source node, and introduces timer, has avoided the distributed relay selection conflict that causes by competitive way.This method is only applicable to have in the wireless network that amplifies forward relay, and universality is undesirable.

[3] Yang Ke etc. is in its " combined optimization of collaboration communication relay selection and power division " (referring to " system emulation journal " in December, 2010) literary composition, require to propose a kind of scheme of selecting via node according to the destination node signal to noise ratio, and derived on this basis based on the source node and the via node optimal power allocation method of signal to noise ratio.Experimental result shows that the optimal power allocation scheme of employing source node more helps improving the power efficiency of system.This method is only applicable to amplify to transmit in the wireless network equally, does not have a universality.

[4] Wang Wenyi etc. is in its " based on the power division of many relayings cooperation diversity system of decoding-forwarding " (referring to " electronics and information journal " in March, 2008) literary composition, with the minimization system outage probability is target, has considered the power division problem of many relayings cooperation diversity system of decoding-forwarding.This system is under the environment of the non-selective channel of slow fading frequency, and according to instantaneous channel condition information, whether decision cooperates, and selects which via node to carry out relaying, and carries out power division between the via node of source node and selection.But this system model is the conventional model of single source node-many via nodes-single destination node, but in actual applications, general more than one of source node, the conventional model applicability is restricted.

Summary of the invention

At the deficiencies in the prior art, the technical problem that quasi-solution of the present invention is determined is that a kind of relay selection method that reduces transmitting power is provided.This method have when guaranteeing proper communication, reduce transmitting power, algorithm complex low, have certain adaptive ability, can be according to the characteristics such as variation real time altering selection strategy of channel status.

The technical scheme that the present invention solve the technical problem is to design a kind of relay selection method that reduces transmitting power, these method employing following steps:

Source node at first sends a RTS message, and this message comprises frequency pilot sign and source node ID; The via node that receives RTS message carries out channel estimating according to this message, obtain and this source node between channel condition information; Each via node sends a CTS message to the Controlling Source node, and this message comprises frequency pilot sign, relaying self ID, source node ID and corresponding channel condition information; The Controlling Source node receives CTS message, picks out relaying into each source node forwarding information according to the content of CTS message by algorithm hereinafter described; The Controlling Source node result that will select informs each source node with the form of message afterwards; Source node is to sending RTC message with the via node that self carries out collaboration communication, and this message comprises source node ID and selected destination node ID; Relaying is replied CTC message after receiving RTC message, and this CTC message comprises self ID and source node ID; Source node is received after the CTC message, begins formally to send message by the cooperation of via node.

Compared with prior art, relay selection method advantage of the present invention is that algorithm is simple relatively, has certain adaptive ability, and can reduce system emission power largely; In actual applications, not only can avoid because the communication delay that brings of algorithm complex height, and can reduce transmitting power, energy savings is a kind of relay selection method with communication efficiency and transmitting power complex optimum.

Description of drawings

Fig. 1 reduces the entire system structural representation of a kind of embodiment of relay selection method of transmitting power for the present invention;

Fig. 2 reduces the flow chart of a kind of embodiment key algorithm of relay selection method of transmitting power for the present invention;

When a kind of embodiment of relay selection method that Fig. 3 reduces transmitting power for the present invention carries out 10 tests, three kinds of system's gross power comparison diagrams that algorithm is required;

When a kind of embodiment of relay selection method that Fig. 4 reduces transmitting power for the present invention carries out 10 tests, the power gain comparison diagram of two kinds of relative optimal algorithms of algorithm;

A kind of embodiment of relay selection method that Fig. 5 reduces transmitting power for the present invention when the source node number changes, three kinds of system's gross power comparison diagrams that algorithm is required;

A kind of embodiment of relay selection method that Fig. 6 reduces transmitting power for the present invention when the source node number changes, the power gain comparison diagram of two kinds of relative optimal algorithms of algorithm;

Fig. 7 reduces a kind of embodiment of relay selection method of transmitting power when interrupting the probability variation for the present invention, three kinds of system's gross power comparison diagrams that algorithm is required;

Fig. 8 reduces a kind of embodiment of relay selection method of transmitting power when interrupting the probability variation for the present invention, the power gain comparison diagram of two kinds of relative optimal algorithms of algorithm.

Embodiment

Further narrate the present invention below in conjunction with embodiment and accompanying drawing thereof:

The relay selection method of the reduction transmitting power of the present invention's design is (hereinafter to be referred as method, referring to Fig. 1-8), general thought is: after the relaying received signal, channel condition information between source node and the via node is estimated, then this information is sent to source node, select which relaying to participate in transmitting by source node again.

The overall system model of the inventive method is the wireless communication system (referring to Fig. 1) of a multiple source node-a plurality of via nodes-single destination node.If: S ₁S _iS _MBe M source node, one of them is that (the Controlling Source node also has the function of transmission information to the Controlling Source node, increases controlled function than common source node; In Fig. 1, represent, i.e. S with thick line _i, to distinguish it); R ₁R _jR _NFor cloth is placed on each source node N via node on every side; D is a destination node.N via node assisted the source node forwarding information.

The technical problem to be solved in the present invention is to pick out the forwarding that M via node participates in signal from N via node, rather than makes all via nodes all participate in forwarding work.The inventive method overall procedure is as follows:

1. send RTS (Ready to Send) message at M the peripherad via node of source node;

2. after via node receives RTS message, carry out channel estimating, obtain and the respective sources node between channel condition information;

3. via node is replied a CTS (Clear to Send) message to the Controlling Source node, and channel condition information is informed the Controlling Source node;

4. the Controlling Source node is picked out collaboration relay node according to channel condition information;

5. the Controlling Source node is selecting the result of via node to send to each source node for each source node;

6. source node sends the cooperation of RTC (Ready to Cooperate) message request to the via node of selecting;

7. via node is replied CTC (Clear to Cooperate) message to source node, agrees to participate in cooperation;

8. source node formally sends information by selected via node.

The concrete steps of the inventive method are as follows: source node at first sends a RTS message, and this message comprises frequency pilot sign and source node ID; The via node that receives RTS message carries out channel estimating according to this message, obtain and this source node between channel condition information; Each via node sends a CTS message to the Controlling Source node, and this message comprises frequency pilot sign, relaying self ID, source node ID and corresponding channel condition information; The Controlling Source node receives CTS message, selects relaying into each source node forwarding information according to the content of CTS message by algorithm hereinafter described; The Controlling Source node result that will select informs each source node with the form of message afterwards; Source node is to sending RTC message with the via node that self carries out collaboration communication, and this message comprises source node ID and selected destination node ID; Relaying is replied CTC message after receiving RTC message, and this CTC message comprises self ID and source node ID; Source node is received after the CTC message, begins formally to send message by the cooperation of via node.

Core content of the present invention is a kind of algorithm of relay selection.Described algorithm is realized at the source node place, based on estimation and the calculating of repeater to channel condition information.Described algorithm comprises (1) formula and (2) formula, and (1) formula is for launching power expression under the prerequisite that guarantees the designing requirement outage probability: promptly

$P=\sqrt{\frac{A(2+B)+A\sqrt{B^2+8B}}{2\mathrm{\ϵ}}}(1+\frac{2B}{B+\sqrt{B^2+8B}})---\left(1\right)$

Wherein,

P is total transmitting power, SNR _{T arg et}Be signal to noise ratio, Be the additive white Gaussian noise variance,

For with S _iAnd R _jBetween the relevant channel fading variance of random variable of distance.

Needed system emission power in the time of can being obtained each source node and carried out collaboration communication with each via node respectively by (1) formula carries out permutation and combination with all nodes, and M * N kind result will be arranged, and it can be write as the form of matrix, i.e. power matrix; (2) formula is this power matrix:

$\left(\begin{array}{ccccc}{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="HDA0000065553100000021.png,HDA0000065553100000031.png"\; state="\{\{state\}\}">P</figure-callout>}}_{\mathrm{1,1}}& {\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="HDA0000065553100000021.png,HDA0000065553100000031.png"\; state="\{\{state\}\}">\; <figure-callout\; id="2"\; label="P"\; filenames="HDA0000065553100000031.png,HDA0000065553100000032.png"\; state="\{\{state\}\}">P</figure-callout>\; </figure-callout>}}_{\mathrm{1,2}}& \mathrm{\&Lambda;}& {\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="HDA0000065553100000021.png,HDA0000065553100000031.png"\; state="\{\{state\}\}">P</figure-callout>}}_{1,N-1}& {\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="HDA0000065553100000021.png,HDA0000065553100000031.png"\; state="\{\{state\}\}">P</figure-callout>}}_{1,\mathrm{<figure-callout\; id="2"\; label="N\; P"\; filenames="HDA0000065553100000031.png,HDA0000065553100000032.png"\; state="\{\{state\}\}">N</figure-callout>}}& \\ P_{}{}_{\mathrm{2,1}}& {\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="HDA0000065553100000031.png,HDA0000065553100000032.png"\; state="\{\{state\}\}">\; <figure-callout\; id="2"\; label="P"\; filenames="HDA0000065553100000031.png,HDA0000065553100000032.png"\; state="\{\{state\}\}">P</figure-callout>\; </figure-callout>}}_{\mathrm{2,2}}& \mathrm{\&Lambda;}& {\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="HDA0000065553100000031.png,HDA0000065553100000032.png"\; state="\{\{state\}\}">P</figure-callout>}}_{2,N-1}& {\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="HDA0000065553100000031.png,HDA0000065553100000032.png"\; state="\{\{state\}\}">P</figure-callout>}}_{2,N}\\ \mathrm{\&Lambda;}& \mathrm{\&Lambda;}& \mathrm{\&Lambda;}& \mathrm{\&Lambda;}& \mathrm{\&Lambda;}\\ P_{M-\mathrm{1,1}}& P_{M-\mathrm{1,2}}& \mathrm{\&Lambda;}& P_{M-1,N-1}& P_{M-1,N}\\ P_{M,1}& P_{M,1}& \mathrm{\&Lambda;}& P_{M,1}& P_{M,1}\end{array}\right)---\left(2\right)$

Each element P in the power matrix _{M, n}Required total transmitting power when representing m source node to select n relaying as cooperative node.

The present invention seeks to and therefore from power matrix, to select the numeric ratio smaller elements exactly and to get final product by selecting to obtain a relaying that can make the power minimum.According to actual conditions and the hypothesis made at this problem, can obtain following two constraintss of selecting repeaters in power matrix: 1. must to find a relaying be its forwarding information to each source node; 2. each repeater can only be a source node forwarding information simultaneously.The respective sense of above-mentioned two constraintss in power matrix is: 1. an element (minimum or less) must be found out in each provisional capital; 2. can only there be an element selected in each row.

The general thought of invention and the flow chart following (referring to Fig. 2) of this algorithm:

(1) M the peripherad via node of source node sends RTS (Ready to Send) message;

(2) after via node receives RTS message, carry out channel estimating, obtain and the respective sources node between channel condition information;

(3) via node is replied a CTS (Clear to Send) message to the Controlling Source node, and channel condition information is informed the Controlling Source node;

(4) the Controlling Source node calculates power matrix P according to channel condition information, and cycle-index K is set;

(5) select delegation to carry out selection operation at random, therefrom select an element of numerical value minimum;

(6) delete the row and column of choosing the element place in the previous step;

(7) (5) (6) two steps are carried out in circulation, are empty up to power matrix P;

(8) (the K value is big more, and resulting result is good more, and complexity also can be high more simultaneously (5) (6) (7) step to be repeated K time.The value of K will be taken into account the source node number, generally gets 10 and gets final product) cycling, select wherein the numerical value minimum once, with eliminate that randomness brings than large deviation.

(9) the Controlling Source node is selecting the result of via node to send to each source node for each source node;

(10) source node sends RTC (Ready to Cooperate) message to the via node of selecting, and request participates in cooperation;

(11) via node is replied CTC (Clear to Cooperate) message to source node, agrees to participate in cooperation;

(12) source node formally sends information by selected via node.

The inventive method uses MATLAB to carry out emulation experiment, and the gained result is referring to Fig. 3-8.This experiment (selects relaying to carry out the method that information is transmitted random choice method respectively at random, prior art), comparison method (being the inventive method mentioned above) and three kinds of algorithms of exhaustive search algorithm (Zui You method in theory) carry out performance relatively at random, be without loss of generality.

Suppose α=2, SNR _{T arg et}=10dB,

Fig. 3 and Fig. 4 are when carrying out 10 tests, the comparison diagram of three kinds of algorithms required system gross power in each test.Wherein, the longitudinal axis unit of Fig. 3 is W, the visual representation system power, and the longitudinal axis unit of Fig. 4 is dB, the power gain of two kinds of relative optimal algorithms of algorithm of expression.In the test, suppose that outage probability is 10 ^-1, the source node number is 4, the relaying number is 16.By Fig. 3,4 as seen, because random choice method has randomness, each power demand has bigger difference, and magnitude of power is bigger.The method of the invention is compared with random choice method at power controlling party mask bigger advantage, and is more or less the same with theoretical optimum exhaustive search algorithm.

Fig. 5 and Fig. 6 are under the situation that the source node number changes, the system power comparison diagram that needs respectively when using three kinds of algorithms.Wherein, the longitudinal axis unit of Fig. 5 is W, the visual representation system power, and the longitudinal axis unit of Fig. 6 is dB, the power gain of two kinds of relative optimal algorithms of algorithm of expression.Suppose that outage probability is 10 ^-1, source node number from 1 to 9 changes 16 of via nodes.As seen from Figure 4, along with the increase of source node number, the total transmitting power of system is in rising trend.When the source node number was no more than 8 (1-8), the effect of comparison method on power-saving was apparent in view at random in the present invention.

Fig. 7 is under different outage probability constraintss the performance comparison diagram of three kinds of algorithms with Fig. 8.Wherein, the longitudinal axis unit of Fig. 7 is W, the visual representation system power, and the longitudinal axis unit of Fig. 8 is dB, the power gain of two kinds of relative optimal algorithms of algorithm of expression.Suppose that the source node number is fixed as 4, the relaying number is 16, and the system break probability is from 10 ^-6To 10 ^-1Between change.Probability is less when interrupting, and the required gross power of system is bigger when promptly reliability of communication system being had relatively high expectations.Compare with random choice method, comparison method hour has certain advantage at outage probability at random.

Claims (2)

1. relay selection method that reduces transmitting power, these system of selection concrete steps are as follows: source node at first sends a RTS message, and this message comprises frequency pilot sign and source node ID; The via node that receives RTS message carries out channel estimating according to this message, obtain and this source node between channel condition information; Each via node sends a CTS message to the Controlling Source node, and this message comprises frequency pilot sign, relaying self ID, source node ID and corresponding channel condition information; The Controlling Source node receives CTS message, picks out relaying into each source node forwarding information according to the content of CTS message by algorithm hereinafter described; The Controlling Source node result that will select informs each source node with the form of message afterwards; Source node is to sending RTC message with the via node that self carries out collaboration communication, and this message comprises source node ID and selected destination node ID; Relaying is replied CTC message after receiving RTC message, and this CTC message comprises self ID and source node ID; Source node is received after the CTC message, begins formally to send message by the cooperation of via node;

Described algorithm comprises (1) formula and (2) formula, and (1) formula is the transmitting power under the prerequisite that guarantees the designing requirement outage probability: promptly

$P=\sqrt{\frac{A(2+B)+A\sqrt{B^2+8B}}{2\mathrm{\&epsiv;}}}(1+\frac{2B}{B+\sqrt{B^2+8B}})---\left(1\right)$

Wherein,

P is total transmitting power, SNR _{T arg et}Be signal to noise ratio,

Be the additive white Gaussian noise variance, For with S _iAnd R _jBetween the relevant channel fading variance of random variable of distance;

(2) formula is a power matrix:

$\left(\begin{array}{ccccc}{P}_{\mathrm{1,1}}& P_{\mathrm{1,2}}& \mathrm{\&Lambda;}& P_{1,N-1}& P_{1,N}\\ P_{\mathrm{2,1}}& P_{\mathrm{2,2}}& \mathrm{\&Lambda;}& P_{2,N-1}& P_{2,N}\\ \mathrm{\&Lambda;}& \mathrm{\&Lambda;}& \mathrm{\&Lambda;}& \mathrm{\&Lambda;}& \mathrm{\&Lambda;}\\ P_{M-\mathrm{1,1}}& P_{M-\mathrm{1,2}}& \mathrm{\&Lambda;}& P_{M-1,N-1}& P_{M-1,N}\\ P_{M,1}& P_{M,1}& \mathrm{\&Lambda;}& P_{M,1}& P_{M,1}\end{array}\right)---\left(2\right)$

Each element P in the power matrix _{M, n}Required total transmitting power when representing m source node to select n relaying as cooperative node; Select the constraints of repeater to be in power matrix: 1. must to find a relaying be its forwarding information to each source node; 2. each repeater can only be a source node forwarding information simultaneously.

2. the relay selection method of reduction transmitting power according to claim 1 is characterized in that described outage probability is 10 ^-1, the source node number is 4-8, the relaying number is 16.

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