CN101640928B - OFDM signal transmitting power division method - Google Patents
OFDM signal transmitting power division method Download PDFInfo
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- CN101640928B CN101640928B CN2009100419512A CN200910041951A CN101640928B CN 101640928 B CN101640928 B CN 101640928B CN 2009100419512 A CN2009100419512 A CN 2009100419512A CN 200910041951 A CN200910041951 A CN 200910041951A CN 101640928 B CN101640928 B CN 101640928B
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Abstract
The present invention aims at providing an OFDM signal transmitting power division method which is capable of following real-time change of a time-varying channel and low in power consumption. The provided OFDM signal transmitting power division method is divided in to a preset stage and a real-time stage. In the preset stage, Pbit-H<2>a correspondence under optimal power division is obtained by estimation. In the real-time stage, the Pbit-H<2>a correspondence is utilized, corresponding Pbit is rapidly obtained according to R required by system and instant H<2>a, further total initial transmitting power is determined, initial power is allocated to each sub channel according to ratio of square of gain of each sub channel, and greedy algorithm is adopted on the basis.
Description
Technical field
The present invention relates to ofdm signal transmit power allocations method.
Background technology
The OFDM technology is divided into some flat fading subchannels to frequency selective fading channels, and the subcarrier on each subchannel can independently be selected modulation coding mode, and modulation coding mode has BPSK, QPSK, 16QAM and 64QAM etc.The many more modulation coding modes of contained bit number in the one-period, the transmitting power of consumption (being called for short power down) is just big more.The characteristics of the Adaptive Modulation and Coding of OFDM (AMC=Adaptive Modulation and Coding) technology are to adjust modulation coding mode according to the time variation of wireless channel, its target is to require under (promptly requiring the error rate of each subchannel all must not be higher than the threshold value that sets) given prerequisite in the error rate of system, reach the transmission rate maximization under given power, perhaps the minimum power under given transmission rate.Under the prerequisite that the error rate of system requires and the target emission rate (calling R in the following text) of system requirements is given, optimum minimum power algorithm is the greedy algorithm that begins iteration from zero bit.So-called greedy algorithm is meant; Relatively in one-period, increase an emission bit on each subcarrier and need the extra transmitting power that increases, seek the subcarrier of the transmitting power minimum that is increased then, this just increases an emission bit on this subcarrier, correspondingly the error rate according to system requires to use instead more powerful modulation coding mode, distribute next emission bit then,, till the total bit number that distributes reaches target bit.
If greedy algorithm is that then the Bit Allocation in Discrete of its final each subcarrier that forms is compared with the Bit Allocation in Discrete that other algorithm forms, and needs the transmitting power minimum that consumes with the initial condition of zero bit as each subcarrier.But the shortcoming of this algorithm also is conspicuous, is exactly that operand is big especially, causes its arithmetic speed not catch up with the real-time change of time varying channel far away, does not therefore use in needs carry out the wireless channel of real-time Transmission at present.
Present stage domestic and international application the most widely the AMC selection algorithm be signal to noise ratio (SNR, Signal Noise Ratio) thresholding diagnostic method, it has used the notion of SNR threshold judgement.Coordinate system as Fig. 1, abscissa is received signal to noise ratio (Eb/N0), ordinate is the error rate (BER), and seven curves in the coordinate system are represented the characteristic curve of seven kinds of different modulation coding modes (indicating in Fig. 1 upper right corner) under the white Gaussian noise channel condition respectively.To each subchannel, with the product of the signal to noise ratio of its distribution that obtained and its channel gain as its received signal to noise ratio (Eb/N0), select the modulation coding mode that the error rate that satisfies system under this received signal to noise ratio condition requires the characteristic curve representative of (promptly being lower than the error rate threshold value of default), come transmitted bit information with selected modulation coding mode.This algorithm can guarantee that the error rate can reach the requirement of system, and amount of calculation is significantly smaller than above-mentioned greedy algorithm, be adapted at using in the time varying channel, but it does not provide a kind of power division mode of comparatively saving power, just simply power averaging is assigned in each subchannel, this will cause the power on the plurality of sub channel wherein unnecessarily to be slatterned.
Summary of the invention
Goal of the invention
The present invention is intended to provide a kind of real-time change and the less ofdm signal transmit power allocations method of power consumption that can catch up with time varying channel.
The major parameter of ofdm signal transmit power allocations method comprises the target emission rate R of system requirements, the instant channel gain of system and the error rate threshold value of default, wherein the error rate of system requires relative fixed, and promptly the error rate threshold value of default remained unchanged in a very long time; The R of system requirements changes relatively more frequently according to real-time needs; The instant channel gain of system then is to change constantly.Thinking of the present invention is, as long as the error rate of system requires to determine, just obtain respectively under a plurality of definite R average every bit transmitting power (calling Pbit in the following text) with the greedy algorithm of macrooperation amount optimum and curve fit earlier and (call H in the following text with each subchannel gains mean-square value
2A) corresponding relation; By the time the R one of system requirements determines, just can be according to R and instant H
2The rapid approximate evaluation of a goes out near the optimum power allocative decision, begins to adopt greedy algorithm from this near the optimum power allocative decision then, only needs this moment smaller calculation just to draw more near the optimum power allocative decision.
Technical scheme
For addressing the above problem, provide ofdm signal transmit power allocations method, it is characterized in that, comprise
Preset stage---given plural R and plural H
2A; To each R: under the error rate of system requires, to each given H
2The power division that a adopts greedy algorithm to adjust each subchannel draws the optimum Pbit under this R; Estimate Pbit～H under each given R with curve fit then
2The a corresponding relation;
Real time phase comprises the steps 10,20,30,40,50---
---step 10: according to the Pbit～H that in presetting step, draws
2The a corresponding relation draws each given R and descends and the real-time H of system
2The Pbit of a correspondence estimates this H with curve fit then
2Pbit under a～R corresponding relation, and then draw the Pbit corresponding with the R of system requirements,
---step 20: with the R of system requirements, Pbit that step 10 draws and OFDM symbol time three's product as total Initial Trans,
---step 30: total Initial Trans that step 20 is drawn according to each subchannel gains square ratio distribute initial power for each subchannel,
---step 40: to each subchannel, with its at the product of the power of distribution that step 30 is obtained and its channel gain as its received signal to noise ratio, the modulation coding mode under the error rate that adopts SNR thresholding determining method to be chosen at system requires,
---step 50:, under the error rate of system requires, adopt greedy algorithm to adjust the rate-allocation of each subchannel from the R of each subchannel at the selected modulation coding mode of step 40 and this modulation coding mode;
Wherein, R represents emission rate, and Pbit represents average every bit transmitting power, H
2A represents each subchannel gains mean-square value.
Beneficial effect
Above-mentioned ofdm signal transmit power allocations method is divided into preset stage and real time phase.As long as the error rate of system requires to determine, just can enter preset stage, estimate to draw the Pbit～H under optimal power allocation
2The a corresponding relation.Arrive real time phase, utilized this Pbit～H
2The a corresponding relation is according to the R of system requirements and instant H
2A obtains corresponding Pbit rapidly, and then definite total Initial Trans is also given each subchannel reasonable distribution initial power and select for use corresponding modulation coding mode as the initial modulation coded system, this initial modulation coding mode is quite near optimum modulation coding mode so, adopt greedy algorithm on this basis, need not a large amount of calculating and just can draw one rapidly more near the optimum power allocative decision.
As long as it is constant that the error rate of system requires, the implementation phase that next just can enter constantly immediately and need not to experience again preset stage.The present invention is arranged in preset stage to a large amount of calculating and finishes, and has alleviated the computational burden of real time phase greatly, makes it can catch up with the real-time change of time varying channel.
Preferably, adopt Pbit～H2a corresponding relation under the given R of experience curve formula Pbit=a lg (H2a)+b match in preset stage; Wherein as unit, a, b are undetermined coefficient to Pbit with decibel.
Preferably, the Pbit～R corresponding relation under the given H2a of step 10 employing experience curve formula Pbit=c R+d match; Wherein as unit, c, d are undetermined coefficient to Pbit with decibel.
Preferably, be 5 in the number of the given R of preset stage, both guaranteed suitable accuracy, can not consume too much resource again.
Description of drawings
Fig. 1 is the error rate-received signal to noise ratio characteristic curve diagram of various modulation coding modes.
Fig. 2 is a Pbit～H under definite R
2The schematic diagram of a curve fit each point.
Fig. 3 is the Pbit～H under a plurality of definite R
2A matched curve figure.
Fig. 4 is a definite H
2The schematic diagram of the Pbit under a～R curve fit each point.
Embodiment
The major parameter of ofdm signal transmit power allocations method comprises the R of system requirements, the instant channel gain of system and the error rate threshold value of default, wherein the error rate requires relative fixed, and promptly the error rate threshold value of default remained unchanged in a very long time; The R of system requirements changes relatively more frequently according to real-time needs; The instant channel gain of system then is to change constantly.Therefore, the present invention is divided into preset stage and real time phase with ofdm signal emission rate distribution method.
As long as the error rate of system requires to determine, just can enter preset stage.The given R that goes ahead of the rest in preset stage is then under the restriction that the error rate of system requires, to a definite H
2A just can calculate the approaching Pbit of several numerical value by enough greedy algorithms, thereby at Pbit～H
2Mark corresponding point in a coordinate system; Respectively to a plurality of definite H
2A carries out same computing, just can be at Pbit～H
2Mark abundant point in a coordinate system, use these points of curve fit then, estimate the Pbit～H under this R approx
2The a corresponding relation is as Fig. 2.Given a plurality of R carries out same computing and match, just can estimate the Pbit～H under each given R
2The a corresponding relation, as shown in Figure 3, for the real time phase utilization.Through repeatedly practice, draw the Pbit～H under the R that determines
2A corresponding relation experience curve formula Pbit=alg (H
2A)+and b, wherein as unit, a, b are undetermined coefficient to Pbit with decibel.The user only need draw H
2Minimum two points that a is different just can be determined the undetermined coefficient of empirical equation to simulate the Pbit～H under definite R
2The a corresponding relation.
Wherein, though different subchannel gains situations, its H
2A may be identical, but at H
2The Pbit numerical value that adopts greedy algorithm to draw under identical this multiple situation of a is more or less the same, and is very little to the influence of curve fit.
At real time phase, at first detect and determine this H constantly
2A is this H
2A makes up Pbit～R coordinate system, utilizes several curves among Fig. 3 to draw this H
2The Pbit that a is corresponding with each R just can mark a plurality of points in this Pbit～R coordinate system, use these points of curve fit then, estimates this H approx
2Pbit under a～R corresponding relation, as shown in Figure 4.This Pbit of R substitution～R corresponding relation with this moment system requirements just can draw its corresponding Pbit.Through repeatedly practice, draw the H that is determining
2Pbit under a～R corresponding relation experience curve formula Pbit=cR+d, wherein as unit, c, d are undetermined coefficient to Pbit with decibel.The user only need draw different minimum two points of R, just can determine the undetermined coefficient of this experience curve formula (straight line formula), simulates definite H
2Pbit under a～R corresponding relation.
The R of system requirements, the Pbit that is drawn and OFDM symbol time three multiplied each other draws total Initial Trans, by each subchannel gains square ratio distribute to each subcarrier, adopt SNR thresholding determining method to choose suitable modulation coding mode then.Begin to adopt greedy algorithm to adjust the modulation coding mode of each subcarrier from this modulation coding mode and speed thereof again, final allocative decision is in close proximity to the optimal distributing scheme that greedy algorithm draws.
Claims (4)
1.OFDM signal transmitting power division method is characterized in that, comprises
Preset stage---given plural R and plural H
2A; To each R: under the error rate of system requires, to each given H
2The power division that a adopts greedy algorithm to adjust each subchannel draws the optimum Pbit under this R; Estimate Pbit～H under each given R with curve fit then
2The a corresponding relation;
Real time phase comprises the steps 10,20,30,40,50---
---step 10: according to the Pbit～H that in presetting step, draws
2The a corresponding relation draws each given R and descends and the real-time H of system
2The Pbit of a correspondence estimates this H with curve fit then
2Pbit under a～R corresponding relation, and then draw the Pbit corresponding with the R of system requirements,
---step 20: with the R of system requirements, Pbit that step 10 draws and OFDM symbol time three's product as total Initial Trans,
---step 30: total Initial Trans that step 20 is drawn according to each subchannel gains square ratio distribute initial power for each subchannel,
---step 40: to each subchannel, with its at the product of the power of distribution that step 30 is obtained and its channel gain as its received signal to noise ratio, the modulation coding mode under the error rate that adopts SNR thresholding determining method to be chosen at system requires,
---step 50:, under the error rate of system requires, adopt greedy algorithm to adjust the rate-allocation of each subchannel from the R of each subchannel at the selected modulation coding mode of step 40 and this modulation coding mode;
Wherein, R represents emission rate, and Pbit represents average every bit transmitting power, H
2A represents each subchannel gains mean-square value.
2. according to the ofdm signal transmit power allocations method of claim 1, adopt experience curve formula Pbit=a lg (H in preset stage
2A)+Pbit～H under the given R of b match
2The a corresponding relation; Wherein as unit, a, b are undetermined coefficient to Pbit with decibel.
3. according to the ofdm signal transmit power allocations method of claim 1 or 2, adopt the given H of experience curve formula Pbit=c R+d match in step 10
2Pbit under a～R corresponding relation; Wherein as unit, c, d are undetermined coefficient to Pbit with decibel.
4. according to the ofdm signal transmit power allocations method of claim 1, be 5 in the number of the given R of preset stage.
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| CN101902812A (en) * | 2010-05-19 | 2010-12-01 | 景略半导体(上海)有限公司 | A kind of adaptive subcarrier transmitting power distribution system and method |
| CN102694617B (en) | 2011-03-22 | 2015-08-19 | 华为技术有限公司 | A kind of methods, devices and systems of data code modulation |
| CN108833341B (en) * | 2018-04-26 | 2020-08-18 | 西安交通大学 | Physical layer secure transmission method based on subcarrier sorting and XOR operation in OFDM system |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1722719A (en) * | 2005-01-07 | 2006-01-18 | 北京邮电大学 | A method of bit and power distribution for adaptive modulation of OFDM system |
| KR20080083658A (en) * | 2005-12-12 | 2008-09-18 | 모토로라 인코포레이티드 | Method and apparatus for cooperative diversity reception of wireless communication signals |
| CN101359939A (en) * | 2007-08-03 | 2009-02-04 | 华为技术有限公司 | Reverse power control method, apparatus and system in orthogonal frequency division multiplexing multiple access system |
| CN101478517A (en) * | 2008-09-22 | 2009-07-08 | 北京邮电大学 | OFDM system dynamic bit loading method based on ordering |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1722719A (en) * | 2005-01-07 | 2006-01-18 | 北京邮电大学 | A method of bit and power distribution for adaptive modulation of OFDM system |
| KR20080083658A (en) * | 2005-12-12 | 2008-09-18 | 모토로라 인코포레이티드 | Method and apparatus for cooperative diversity reception of wireless communication signals |
| CN101359939A (en) * | 2007-08-03 | 2009-02-04 | 华为技术有限公司 | Reverse power control method, apparatus and system in orthogonal frequency division multiplexing multiple access system |
| CN101478517A (en) * | 2008-09-22 | 2009-07-08 | 北京邮电大学 | OFDM system dynamic bit loading method based on ordering |
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