CN1773901A - Minimum transmitting power adaptive modulating method based on service quality requirement - Google Patents

Abstract

An adaptive modulation method of minimum emission power based on service quality requirement includes giving out closed solution of system minimum emission power problem under channel information feedback condition, carrying out discretization treatment to closed solution and adjusting modulation order of sub channel till current modulation order sun of all sub channels is equal to object transmission rate, confirming that modulation order and emission power of each sub channel at this point is optimum, then finalizing distribution of bit and power.

Description

Minimum emissive power adaptive modulation method based on QoS requirement

Technical field

The present invention relates to a kind of minimum emissive power adaptive modulation method, can make multi-input multi-output system reach the desired service quality of user with total transmitting power of minimum based on QoS requirement.Belong to wireless communication technology field.

Background technology

In recent years, for the capacity that utilizes multi-input multi-ouput channel to provide as far as possible fully, adaptive modulation technology is considered to one of the most effective means always.It can select the bit and the power allocation scheme of transmitter adaptively according to channel state variations.At present, prevailing in this respect scheme all is by under the prerequisite of given total transmitting power, realizes in the mode of maximized system capacity.The advantage of this class scheme is to guarantee that system realizes transfer of data with big as far as possible speed under current channel condition.

The Radio Link required service quality that reaches, particularly target bit and the target rate of delivering a letter is often determined by the type of service of transmitting yet in actual applications.For this situation, carry out the maximized Adaptive Modulation multi-input multi-output system of the transmission rate underaction that just seems based on given transmitting power, and may cause the waste of transmitting power or the actual performance of system not to reach the needed index of service.So according to the needs of transport service, the multi-input multi-output system that minimizes transmitting power of customization modulation in real time and power configuration parameter will have more attraction.Compare with aforementioned prioritization scheme, this adaptive modulation scheme that minimizes transmitting power has significant advantage:

1, concerning single terminal, can be under the situation that satisfies active user's needs, with minimum emissive power work, significant for saving the terminal energy consumption and prolonging continuous working period.

2, from the angle of whole network, when having the phase mutual interference between each Radio Link in the network, the adaptive modulation scheme that minimizes transmitting power based on user's request not only can reduce each interference among links, and the parameter on subnetwork upper strata can be introduced directly in the middle of the physical layer design, make the cross-layer optimizing of wireless network become possibility.

At present, also be in the starting stage for the research that minimizes the transmitting power algorithm that is applicable to multi-input multi-output system, direct use discretization method only has been discussed in the existing research document has been carried out global optimizing (H.Zhuang, L.Dai, S.Zhou, and Y.Yao, " Low Complexity Per-Antenna Rate and PowerControl Approach for Closed-Loop V-BLAST " IEEE Trans.Commun., vol.51, pp.1783-1787, Nov.2003).The discretization method of this recurrence can not provide the closed solutions that minimizes the transmitting power algorithm, and its computing complexity is higher, and the practical application meeting is caused adverse effect.

Summary of the invention

The objective of the invention is at the deficiencies in the prior art, a kind of minimum emissive power adaptive modulation method based on QoS requirement is proposed, not only can provide many input majorities and go out to minimize in the system total emission power theory problem optimal solution, and can make system have lower computational complexity in the process of seeking best power, Bit Allocation in Discrete scheme.

For realizing this purpose, method of the present invention has at first provided under perfect feedback of channel information condition, multi-input multi-output system minimizes the closed solutions of transmitting power problem, and then this closed solutions is carried out discretization handle, if the order of modulation sum after all subchannel discretizations is not equal to target transmission speed, then further the order of modulation of subchannel is adjusted.Adjusting hour hands carries out respectively less than the situation of target transmission speed greater than reaching sub-channel modulation exponent number sum, current order of modulation sum until all subchannels equals target transmission speed, this moment, the order of modulation and the transmitting power of each subchannel were the best, finished bit and power division.

Method of the present invention specifically comprises the steps:

1, the channel information matrix zero defect of multi-input multi-output system is not had feeds back to transmitting terminal tardily, and respectively this channel information matrix is carried out singular value decomposition in the sending and receiving end, to obtain the weighting matrix of transceiver, and then multi-input multi-ouput channel is divided into a plurality of parallel mutually orthogonal subchannels, the number of subchannel is identical with channel information order of matrix number.

2, set identical target bit for each subchannel, this target bit equals the target bit of whole system, sets up the explicit relation model between the total transmitting power of multi-input multi-output system and target transmission speed and the target bit then.

3, suppose that the order of modulation of each subchannel can be all over any value of getting in the real number field, then according to the relational model of total transmitting power and target transmission speed and target bit, adopt method of Lagrange multipliers, calculate multi-input multi-output system under perfect channel feedback condition, can make the theoretical closed solutions of the Bit Allocation in Discrete scheme of the total transmitting power minimum of system.

4, the order of modulation of each subchannel that will be obtained by closed solutions rounds, and carry out discretization and handle, to the minus subchannel of all order of modulation, get its order of modulation and equal zero, to the subchannel of all order of modulation, get its order of modulation and equal target transmission speed greater than target transmission speed; If the order of modulation sum after all subchannel discretizations equals target transmission speed, this moment, the order of modulation and the transmitting power of each subchannel were the best, finished bit and power division; Otherwise adjust the order of modulation of subchannel.

5, when adjusting the order of modulation of subchannel, for the order of modulation sum of current all subchannels situation greater than target transmission speed, theoretical closed solutions with each subchannel deducts its current order of modulation, try to achieve the difference between the two, the subchannel of selecting then to have minimal difference makes its order of modulation subtract one, repeat, equal target transmission speed, finish bit and power division until the current order of modulation sum of all subchannels; For the order of modulation sum of current all subchannels situation less than target transmission speed, then deduct its corresponding theory closed solutions with the current order of modulation of each subchannel, try to achieve the difference between the two, the subchannel that selection has minimal difference makes its order of modulation add one, repeat, current order of modulation sum until all subchannels equals target transmission speed, finishes bit and power division.

The present invention is by above step, not only can provide many input majorities and go out to minimize in the system total emission power theory problem optimal solution, and can make the process of system looks best power, Bit Allocation in Discrete scheme have lower computational complexity, significant to the cross-layer optimizing of realizing wireless communication system.

Description of drawings

Fig. 1 is the theory diagram of the suitable Adaptive Modulation multi-input multi-output system that minimizes transmitting power of the inventive method.

Fig. 2 be the inventive method under different configuration condition, the actual performance of BER in 2 * 2 and 4 * 4 multi-input multi-output system.Wherein target bit is taken from set { 10 ^-410 ^-310 ^-210 ^-1, target transmission speed is taken from set, and { 5 10 15}, unit are bit/sampling point.

Fig. 3 be the inventive method under above configuration condition, required total transmitting power.

Embodiment

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

Provided the structured flowchart that minimizes transmission power adaptation modulation multi-input multi-output system in Fig. 1, at transmitting terminal, the source bit stream is assigned on each antenna branch through Bit Allocation in Discrete, forms by modulation and emission weighting then to transmit; At receiving terminal, received signal is multiplexing by separating mediation after receiving weighting, finally obtains receiving bit stream.At such system, the step that application the present invention carries out Adaptive Modulation is as follows:

1, divide subchannel:

For multi-input multi-output system as shown in Figure 1, its signal transmitting and receiving model is as follows:

r＝Hs+n (1)

Wherein, r represents that received signal, s represent to transmit, H represents that actual channel transmission matrix, n represent white Gaussian noise.At first, the channel information matrix H of multi-input multi-output system is fed back to transmitting terminal, and, try to achieve the weighting matrix U of receiving-transmitting sides respectively by H being carried out singular value decomposition in the sending and receiving end ^HAnd V:

$H=U\·\mathrm{diag}(\sqrt{{\mathrm{\λ}}_1}\·\·\·\sqrt{{\mathrm{\λ}}_k})\·V^H----\left(2\right)$

Then by receiving and transmitting signal is weighted:

s＝Vx，y＝U ^Hr. (3)

Multi-input multi-ouput channel is divided into k parallel mutually orthogonal subchannel, and sets up the mode of these subchannels:

$y=\mathrm{diag}(\sqrt{{\mathrm{\λ}}_1}\·\·\·\sqrt{{\mathrm{\λ}}_k})x+U^{H}n----\left(4\right)$

Wherein, the number k of subchannel equals the order of channel information matrix H.

2, setting each subchannel all has identical target bit, and this target bit just equals the target bit Ber of whole system _Tgt:

Ber _i＝Ber _tgt (5)

When using quadrature amplitude modulation, can obtain the order of modulation b of each subchannel as the modulation system of each subchannel _i, transmitted power P _iWith target bit Ber _TgtBetween approximation relation model (S.T.Chungand A.J.Goldsmith, " Degree of freedom in adaptive modulation:Aunifiedview, " IEEE Trans.Commun., vol.49, no.9, pp.1561-1571, Sept.2001):

$P_i=-\frac{{\mathrm{\σ}}_n^2\·(2^{b_i}-1)\·\ln \left(5\mathrm{Be}{r}_{\mathrm{tgt}}\right)}{{1.6\mathrm{\λ}}_i}----\left(6\right)$

Then this moment, can set up the explicit relation model between the total transmitting power of multi-input multi-output system and target transmission speed and the target bit;

$P_{\mathrm{ttl}}=\underset{i=l}{\overset{k}{\mathrm{\Σ}}}{P}_i=-\underset{i=l}{\overset{k}{\mathrm{\Σ}}}\frac{{\mathrm{\σ}}_n^2\·(2^{b_i}-1)\·\ln \left(5\mathrm{Be}{r}_{\mathrm{tgt}}\right)}{1.6{\mathrm{\λ}}_i}----\left(7\right)$

3, suppose that further the sub-channel modulation exponent number can then according to (7), satisfy target transmission speed R all over any value of getting in the real number field _TgtWith target bit Ber _TgtMulti-input multi-output system minimize the problem with equality constraint that the transmitting power problem can be expressed as:

${\left\{b_i\right\}}^{\mathrm{opt}}=\arg \underset{b_i}{\min }-\underset{i=1}{\overset{k}{\mathrm{\Σ}}}\frac{{\mathrm{\σ}}^2\·(2^{b_i}-1)\·\ln \left(5\mathrm{Be}{r}_{\mathrm{tgt}}\right)}{1.6{\mathrm{\λ}}_i},----\left(8a\right)$

$\underset{i=1}{\overset{k}{\mathrm{\Σ}}}{b}_i=R_{\mathrm{tgt}},b_i\∈R.----\left(8b\right)$

Use method of Lagrange multipliers and find the solution (8) formula, can obtain the closed solutions of the best order of modulation of each subchannel:

$b_i^{\mathrm{opt}}=\frac{1}{k}{\log }_2(2^{R_{\mathrm{tgt}}}\·\underset{i=1}{\overset{k}{\mathrm{\Π}}}{A}_i)-{\log }_2\left(A_i\right)----\left(9\right)$

Wherein $A_i=\frac{-{\mathrm{\σ}}^2\ln \left(5\mathrm{Be}{r}_{\mathrm{tgt}}\right)}{1.6{\mathrm{\λ}}_i}.$

4, at first the theoretical best order of modulation of subchannel is rounded:

Order of modulation after will rounding then adjust to the closed interval [0, R _Tgt] in, if promptly Then order

If

Then order At last the result after rounding is adjudicated, if Then Be adaptable optimum bit allocative decision, algorithm finishes; Otherwise execution in step 5), the sub-channel modulation exponent number is adjusted.

5, to the adjustment of sub-channel modulation exponent number:

If

Then calculate the gap vector

Find out the wherein subchannel of difference minimum, promptly $j=\arg \underset{i}{\min }\left(\mathrm{dif}{f}_i\right),i=1,...,k,$ Make the order of modulation of this subchannel subtract 1, promptly Then, adjusted order of modulation is judged, if

Then repeat, until Algorithm finishes.

Be adaptable optimum bit allocative decision.If

Then calculate the gap vector Find out the wherein subchannel of difference minimum, promptly $j=\arg \underset{i}{\min }\left(\mathrm{dif}{f}_i\right),i=1,...,k,$ Make the order of modulation of this subchannel add 1, promptly Adjusted order of modulation is judged, if

Then repeat, until Algorithm finishes. Be adaptable optimum bit allocative decision.

For performance of the present invention is described, embodiments of the invention are applied to method respectively in 2 * 2 and 4 * 4 the multi-input multi-ouput channel environment.In all emulation experiments, all use quadrature amplitude modulation as modulation system; And with target bits transmission rate R _TgtBe set to 5,10 respectively, 15 bits/sampling point, target bit Ber _TgtThen be selected from set { 10 ^-410 ^-310 ^-210 ^-1; The power setting of background noise is ${\mathrm{\σ}}_n^2=1.$

Fig. 3 has provided the difference of the present invention between following actual bit error rate of all typical environment (configuration) and target bit.As can be seen, no matter how system parameters is selected, method of the present invention can both be controlled at the actual bit error rate of system near the change curve of target bit effectively from emulation.

Then provided these two multi-input multi-output systems required transmission gross power under different QoS requires among Fig. 4, therefrom as can be seen, along with the increasing of number of antennas, the decline of target bit and reducing of target transmission speed, method of the present invention all can make the total emission power of system significantly reduce.This simulation result has proved that from another angle the present invention is in the validity aspect the total emission power control.

Claims (1)

1, a kind of minimum emissive power adaptive modulation method based on QoS requirement is characterized in that comprising the steps:

1) the channel information matrix zero defect of multi-input multi-output system is not had feeds back to transmitting terminal tardily, and respectively this channel information matrix is carried out singular value decomposition in the sending and receiving end, to obtain the weighting matrix of transceiver, and then multi-input multi-ouput channel is divided into a plurality of parallel mutually orthogonal subchannels, the number of subchannel is identical with channel information order of matrix number;

2) set identical target bit for each subchannel, this target bit equals the target bit of whole system, sets up the explicit relation model between the total transmitting power of multi-input multi-output system and target transmission speed and the target bit then;

3) suppose that the order of modulation of each subchannel can be all over any value of getting in the real number field, then according to the relational model of total transmitting power and target transmission speed and bit error rate, adopt method of Lagrange multipliers, calculate multi-input multi-output system under perfect channel feedback condition, can make the theoretical closed solutions of the Bit Allocation in Discrete scheme of the total transmitting power minimum of system;

4) order of modulation of each subchannel that will be obtained by closed solutions rounds, and carry out discretization and handle, to the minus subchannel of all order of modulation, get its order of modulation and equal zero, to the subchannel of all order of modulation, get its order of modulation and equal target transmission speed greater than target transmission speed; If the order of modulation sum after all subchannel discretizations equals target transmission speed, this moment, the order of modulation and the transmitting power of each subchannel were the best, finished bit and power division; Otherwise adjust the order of modulation of subchannel;

5) when adjusting the order of modulation of subchannel, for the order of modulation sum of current all subchannels situation greater than target transmission speed, theoretical closed solutions with each subchannel deducts its current order of modulation, try to achieve the difference between the two, the subchannel of selecting then to have minimal difference makes its order of modulation subtract one, repeat, equal target transmission speed, finish bit and power division until the current order of modulation sum of all subchannels; For the order of modulation sum of current all subchannels situation less than target transmission speed, then deduct its corresponding theory closed solutions with the current order of modulation of each subchannel, try to achieve the difference between the two, the subchannel that selection has minimal difference makes its order of modulation add one, repeat, current order of modulation sum until all subchannels equals target transmission speed, finishes bit and power division.

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