CN100574171C - MIMO ofdm system emitting antenna selecting and self-adaptive modulation method - Google Patents

Abstract

The invention discloses emitting antenna selecting and self-adaptive modulation method in a kind of multi-input multi-output orthogonal frequency division multiplexing system, at first estimate the bit error rate of each subcarrier under all modulation systems and all combination of antennas, if the average error bit rate of each combination of antennas on all subcarriers under the high modulation rank is lower than target bit, all subcarriers all adopt the highest level modulation system so, and one group of minimum transmitting antenna of selection number of antennas, if minimum all greater than target bit in each bit error rate under the lowest modulation rank, then do not do any selection, otherwise in the bit error rate of initial estimation, select less than the highest bit error rate of peak value bit error rate and modulation levels as alternative, utilize each alternative Bit Error Rate Computation average error bit rate, according to the comparison of average error bit rate and target bit, determine the selection of antenna and modulation system.The present invention has realized the selection and the Adaptive Modulation of transmitting antenna.

Description

MIMO ofdm system emitting antenna selecting and self-adaptive modulation method

Technical field

The present invention relates to OFDM (OFDM) wireless communication system of a kind of multiple-input and multiple-output (MIMO), relate in particular to a kind of emitting antenna selecting and self-adaptive modulation method in space diversity MIMO ofdm system.

Background technology

Along with development of wireless communication devices, the user has proposed higher requirement for large-capacity data emission and fast data transmission, therefore, need effectively utilize the wireless communication system resource, improves the performance and the efficient of wireless communication system.Yet in the mobile communication system in future, multipath fading and bandwidth efficiency will be to hinder the major technique factor that communication system is greatly developed.How overcoming this two big difficulty, is the core of next generation wireless communication research.Multicarrier treatment technology based on OFDM (OFDM) can be by being converted into flat channel with the frequency selectivity multidiameter fading channel in frequency domain, thereby reduced the influence of multipath fading, and multiple-input and multiple-output (MIMO) technology can increase the spectrum utilization efficiency of system under the condition that does not increase system bandwidth, so OFDM and MIMO technology will become the core of physical layer process in the next generation wireless communication system.Further, the MIMO ofdm system that MIMO and OFDM technology are combined just can make full use of Radio Resource in time domain, frequency domain and spatial domain, and reaches stronger reliability and very high transmission rate by diversity.

In the MIMO ofdm system, base station and user side have all disposed many antennas, each transmitting antenna and every reception antenna just can be corresponding to channels, like this, in the mimo system operating process, because the characteristic changeable of wireless channel, make that each channel in the mimo system is not to obtain higher signal noise ratio (SNR), so, in order to obtain higher reliability and reduction hardware cost, we wish only to utilize the channel status good channel.It line options is a kind of technology of low-cost low complex degree, and it is selected an antenna subset, thereby obtain certain gain according to certain strategy from many transmit antennas or reception antenna.Its theoretical foundation is, in the mimo system of space diversity, the information of all antennas emissions is identical, in order to make the diversity gain maximization, can utilize best several of channel status in all transmitting antennas, transmits from these several antennas.

In spatial diversity system, can recently carry out a day line options according to the noise of maximization receiving terminal, just will from many antennas, select decline minimum several, perhaps several of fading factor amplitude maximum; Also can carry out a day line options based on the minimized criterion of channel average error bit rate.At the Chinese patent CN 1578192 (publication number) of on July 8th, 2004 application, the open date is just to have described a kind of emitting antenna selecting method according to first kind of criterion on 02 09th, 2005 " transmission diversity apparatus in the mobile communication system and the method ".Receiver calculates the signal to noise ratio (snr) of the forward channel relevant with every transmit antennas to carry out the BLAST decoding from the received signal of many reception antennas, to determine the channel characteristics of the forward channel of every transmit antennas correspondence in many transmit antennas.And with this channel status feature as the selection feedback information of transmitting antenna to transmitter, by transmitter according to this Information Selection state preferably transmitting antenna come the transmitting business signal.But, do not illustrate in this patent and judge the foundation of selecting several transmit antennas.At IEEE International Conference on Communications 2002, announce the paper that is entitled as " Statistical MIMO Antenna Sub-Set Selection with Space-Time Coding " that Gore D and Paulraj A write on the first volume 641～645 page numbers of ICC 2002, in this piece paper, described a kind of antenna selecting method that minimizes criterion based on the channel average error bit rate.But this method is just at mimo system, and the hypothesis mimo channel has the characteristics of flat fading, is not suitable for the MIMO ofdm system with frequency selective fading channels characteristic.

Therefore, in the MIMO ofdm system, how to make system transmissions bit error rate minimum, hardware cost is minimum simultaneously, so that make full use of finite wireless resources, becomes the essential problem that solves.

Summary of the invention

Technical problem to be solved by this invention is to provide emitting antenna selecting and the self-adaptive modulation method in a kind of multi-input multi-output orthogonal frequency division multiplexing system, in having the MIMO ofdm system of frequency selective fading channels characteristic, realize the selection and the Adaptive Modulation of transmitting antenna.

For solving the problems of the technologies described above, the invention provides emitting antenna selecting and self-adaptive modulation method in a kind of multi-input multi-output orthogonal frequency division multiplexing system, comprise the steps:

(1),, estimates the bit error rate of all emitting antenna combination under high modulation rank at each subcarrier according to the signal to noise ratio of received signal;

(2), calculate under the high modulation rank every kind of transmission antenna group and be combined in average error bit rate on all subcarriers according to described each bit error rate of step (1);

(3) in described each average error bit rate of determining step (2) maximum bit error rate whether less than target bit, if judged result is for being, then all subcarriers are all adopted the modulation system of highest level, and select one group of minimum transmitting antenna of number of transmit antennas, as final transmission means.

If the judged result of described step (3) then further comprises the steps: for not

(4) according to the signal to noise ratio of received signal,, estimate the bit error rate of all emitting antenna combination under the lowest modulation rank at each subcarrier;

(5) in described all bit error rates of determining step (4) minimum bit error rate whether greater than target bit, if judged result is for being then all subcarriers not to be done any emitting antenna selecting and modulation system selection.

If the judged result of described step (5) then further comprises the steps: for not

(6) according to the signal to noise ratio of received signal,, obtain the bit error rate of all emitting antenna combination under all modulation levels at each subcarrier;

(7), determine the initial spike bit error rate at each subcarrier;

(8) in described all bit error rates of step (6), at each subcarrier, select one less than when the highest bit error rate of previous peaks bit error rate, corresponding modulation levels as alternative bit error rate;

(9), calculate the average error bit rate in the whole bandwidth according to each alternative bit error rate of selecting in the step (8) at each subcarrier;

(10) whether the described average error bit rate of determining step (9) is less than target bit;

(11) if the judged result of step (10) for not, then reduces to re-execute step (8), (9), (10), (11) when the previous peaks bit error rate, until the average error bit rate of calculating less than target bit;

(12) this is calculated first, decide less than the current alternative bit error rate of each subcarrier of the average error bit rate correspondence of target bit, and the modulation system and the emitting antenna combination of described current each alternative bit error rate correspondence of deciding is chosen as final transmission means.

Wherein, if the judged result of described step (10) is for being then further to comprise the steps:

(11A) increase, re-execute step (8), (9), (10), (11A), be not less than target bit until the average error bit rate of calculating when the previous peaks bit error rate;

(12A) will calculate for the last time, decide less than the current alternative bit error rate of each subcarrier of the average error bit rate correspondence of target bit, and the modulation system and the emitting antenna combination of described current each alternative bit error rate correspondence of deciding is chosen as final transmission means.

Wherein, if the judged result of described step (10) is for being then to can further include following steps:

(11B) increase, re-execute step (8), (9), (10), (11B), be not less than target bit until the average error bit rate of calculating when the previous peaks bit error rate;

(12B) reduce to re-execute step (8), (9), (10), (11) when the previous peaks bit error rate;

(13) this is calculated once more, decide less than the current alternative bit error rate of each subcarrier of the average error bit rate correspondence of target bit, and the modulation system and the emitting antenna combination of described current each alternative bit error rate correspondence of deciding is chosen as final transmission means.

Wherein, in the described step (3),, then select wherein that group transmitting antenna of average error bit rate minimum if there are many group transmitting antennas all to satisfy the minimum requirement of number of transmit antennas.

Wherein, step (6) can comprise:

(6-1),, estimate the bit error rate of all emitting antenna combination under all modulation levels except that the highest and lowest modulation rank at each subcarrier according to the signal to noise ratio of received signal;

(6-2) bit error rate that step (6-1) is calculated and described step (1) are united with the bit error rate that step (4) calculates, and obtain the bit error rate of all emitting antenna combination under all modulation levels.

Wherein, in the described step (8), if there are a plurality of bit error rates all to satisfy less than when the previous peaks bit error rate, and the corresponding the highest requirement of modulation levels, then therefrom select that minimum bit error rate of corresponding number of transmit antennas as alternative bit error rate again.

Wherein, in the described step (8), if there are a plurality of bit error rates all to satisfy less than when previous peaks bit error rate, corresponding high, the most corresponding minimum requirement of number of transmit antennas of modulation levels, then again from that bit error rate of wherein selecting the bit error rate minimum as alternative bit error rate.

The present invention also provides emitting antenna selecting and the self-adaptive modulation method in a kind of multi-input multi-output orthogonal frequency division multiplexing system, comprises the steps:

(1) according to the signal to noise ratio of received signal,, estimates the bit error rate of all emitting antenna combination under all modulation levels at each subcarrier;

(2), calculate under the high modulation rank every kind of transmission antenna group and be combined in average error bit rate on all subcarriers according to described each bit error rate of step (1);

(3) in described each average error bit rate of determining step (2) maximum bit error rate whether less than target bit, if judged result is for being, then all subcarriers are all adopted the modulation system of highest level, and select one group of minimum transmitting antenna of number of transmit antennas, as final transmission means.

If the judged result of described step (3) then further comprises the steps: for not

(4),, calculate the bit error rate of all emitting antenna combination under the lowest modulation rank at each subcarrier according to described each bit error rate of step (1);

(5) in described all bit error rates of determining step (4) minimum bit error rate whether greater than target bit, if judged result is for being then all subcarriers not to be done any emitting antenna selecting and modulation system selection.

If the judged result of described step (5) then further comprises the steps: for not

(6), determine the initial spike bit error rate at each subcarrier;

(7) in described all bit error rates of step (1), at each subcarrier, select one less than when the highest bit error rate of previous peaks bit error rate, corresponding modulation levels as alternative bit error rate;

(8), calculate the average error bit rate in the whole bandwidth according to each alternative bit error rate of selecting in the step (7) at each subcarrier;

(9) whether the described average error bit rate of determining step (8) is less than target bit;

(10) if the judged result of step (9) for not, then reduces to re-execute step (7), (8), (9), (10) when the previous peaks bit error rate, until the average error bit rate of calculating less than target bit;

(11) this is calculated first, decide less than the current alternative bit error rate of each subcarrier of the average error bit rate correspondence of target bit, and the modulation system and the emitting antenna combination of described current each alternative bit error rate correspondence of deciding is chosen as final transmission means.

Wherein, if the judged result of described step (9) is for being then further to comprise the steps:

(10A) increase, re-execute step (7), (8), (9), (10A), be not less than target bit until the average error bit rate of calculating when the previous peaks bit error rate;

(11A) will calculate for the last time, decide less than the current alternative bit error rate of each subcarrier of the average error bit rate correspondence of target bit, and the modulation system and the emitting antenna combination of described current each alternative bit error rate correspondence of deciding is chosen as final transmission means.

Wherein, if the judged result of described step (9) is for being then to can further include following steps:

(10B) increase, re-execute step (7), (8), (9), (10B), be not less than target bit until the average error bit rate of calculating when the previous peaks bit error rate;

(11B) reduce to re-execute step (7), (8), (9), (10) when the previous peaks bit error rate;

(12) this is calculated once more, decide less than the current alternative bit error rate of each subcarrier of the average error bit rate correspondence of target bit, and the modulation system and the emitting antenna combination of described current each alternative bit error rate correspondence of deciding is chosen as final transmission means.

Wherein, in the described step (3),, then select wherein that group transmitting antenna of average error bit rate minimum if there are many group transmitting antennas all to satisfy the minimum requirement of number of transmit antennas.

Wherein, in the described step (7), if there are a plurality of bit error rates all to satisfy less than when the previous peaks bit error rate, and the corresponding the highest requirement of modulation levels, then therefrom select that minimum bit error rate of corresponding number of transmit antennas as alternative bit error rate again.

Wherein, in the described step (7), if there are a plurality of bit error rates all to satisfy less than when previous peaks bit error rate, corresponding high, the most corresponding minimum requirement of number of transmit antennas of modulation levels, then again from that bit error rate of wherein selecting the bit error rate minimum as alternative bit error rate.

Method according to emitting antenna selecting of the present invention and Adaptive Modulation, emitting antenna selecting in the mimo system and the Adaptive Modulation in the ofdm system merged into one realize, be lower than under target bit and the unlimited decision rule in system's average error bit rate near target bit, realized that maximization of system transmissions bit number and number of transmit antennas are minimized, improved the frequency domain and the spatial domain efficiency of resource of MIMO OFDM wireless communication system.And antenna selecting method of the present invention utilizes the average error bit rate information of system, needs are selected the total number of transmitting antenna definite process, select the deterministic process of which transmit antennas to get in touch naturally together, and described method makes full use of the characteristic that the OFDM technology overcomes frequency selective fading, makes the method for the invention can apply to the MIMO ofdm system.

Description of drawings

Fig. 1 is according to the described schematic flow sheet of realizing emitting antenna selecting and Adaptive Modulation in the MIMO ofdm system of embodiments of the invention.

Fig. 2 is according to the described method flow schematic diagram of determining the initial spike bit error rate in realizing emitting antenna selecting and Adaptive Modulation process of embodiments of the invention.

Embodiment

In multiple-input and multiple-output (MIMO) and OFDM (OFDM) system, it line options and Adaptive Modulation are to improve two technology of systematic function, wherein Adaptive Modulation is exactly according to the channel variation on each subcarrier, select suitable modulation system for each subcarrier, the channel status performance index here can be signal to noise ratio (snr)s.In ofdm system,, make the information rate maximization of whole OFDM system if given transmitting power and bit error rate restrictive condition always can be the suitable modulation system of each subcarrier allocation according to channel condition information so adaptively.And a day line options is exactly all to have disposed in the mimo system of many antennas at transmitting terminal and receiving terminal, selects a subclass and realize transmitting and receiving function from numerous transmitting antennas or reception antenna.Diversity and spatial reuse because the processing mode of MIMO is had living space, a day line options have emitting antenna selecting, reception antenna to select and transmit receive antenna is selected, and the present invention is mainly concerned with the emitting antenna selecting in the spatial diversity system.

The purpose of sky line options of the present invention and self-adaptive modulation method is: in the MIMO ofdm system, under the prerequisite of certain bit error rate restriction, for each subcarrier is selected suitable modulation system and is the suitable emitting antenna combination of system's selection, make the maximization of transmitted bit number, the number of transmit antennas of system minimize, satisfy system's average error bit rate simultaneously and be lower than and be infinitely close to target bit, thereby improve the level of resources utilization of MIMO ofdm system.

To achieve these goals, the present invention proposes a kind of method that realizes emitting antenna selecting and Adaptive Modulation of uniting in the MIMO ofdm system, Fig. 1 has provided the flow chart according to the method for the invention.Below with N _T=4 transmit antennas, N _R=4 reception antennas are the use that example describes this method, and its operating process is as follows:

Step 101: according to the signal to noise ratio of all subcarrier respective channels, calculate all possible antenna configurations situation and the bit error rate under might modulation system, wherein, the modulation system that system adopts can but to be not limited to be BPSK, QPSK, 16QAM, 64QAM, for for simplicity, we distinguish index of reference m=0,1,2,3,4 represent.At N _TUnder=4 the situation, we are designated as 1,2,3,4 respectively with the call number of its antenna, for convenience, all transmission antenna group are share a S set to be described (because just carry out emitting antenna selecting, therefore when describing combination of antennas, just at transmitting antenna), that is:

S={ (1), (2), (3), (4), (1,2), (1,3), (1,4), (2,3), (2,4), (3,4), (1,2,3), (1,2,4), (2,3,4), (1,2,3,4) }, these 14 kinds combination difference index of reference q=1,2 ..., 14 represent.Wherein q=1 represents just to utilize the 1st transmit antennas to launch, and is described as (1) in set; Q=5 represents that system just selects for use the 1st, 2 antenna to launch, and is described as (1,2) in set; The rest may be inferred for the implication of other combinations.Like this, the modulation system that each subcarrier may be supported has 4 kinds, and possible antenna configurations mode has 14 kinds, if system assignment is given a user C subcarrier, then need to calculate 4 * 14 * C bit error rate altogether, need to store after these bit error rate estimations are finished.

Describe the method for estimation of bit error rate below in detail.Suppose that the bit number that c subcarrier distributes is b under m kind modulation system _{M, c}, according to above-mentioned hypothesis, b for modulation system _M.c{ 0,1,2,4, any among the 6} corresponds respectively to not modulation systems such as allocation bit, BPSK, QPSK, 16QAM, 64QAM to possible value for set.Make P _{K, m, c}Represent c subcarrier in modulation system m, q kind emitting antenna combination k transmitting antenna at signal to noise ratio γ _cOn bit error rate, wherein, the number of transmit antennas in the q kind emitting antenna combination is K, the respective antenna call number is designated as k=1,2 ..., K.Because the frequency selective fading characteristic causes the signal to noise ratio on each subcarrier of system different, the signal to noise ratio of each subcarrier correspondence is estimated according to formula (1) and (2).Wherein, H _{C, n, k}(ω) expression n (n=1,2 ..., N _R) root reception antenna and k (k=1,2 ..., K) between the transmit antennas at the frequency domain impulse response of c subcarrier lower channel, π _cBe the transmitting power of distributing on the respective sub, α _{C, n}Represent the weighted factor on c subcarrier on each reception antenna, and σ _v ²The expression average noise power.Bit error rate under the BPSK modulation system can estimate according to formula (3), and the bit error rate of QPSK, 16QAM, 64QAM correspondence can estimate according to formula (4),

${\mathrm{\γ}}_c=\frac{{\mathrm{\π}}_c/K\·{\left|f(\mathrm{\α},\mathrm{\ω})\right|}^2}{({\mathrm{\α}}_{c,1}^2+{\mathrm{\α}}_{c,2}^2+{\mathrm{\α}}_{c,3}^2+\·\·\·+{\mathrm{\α}}_{c,N_R}^2)\·{\mathrm{\σ}}_v^2}$

f(α，ω)＝α _c，1·{H _c，1，1(ω)+H _c，1，2(ω)+…+H _c，1，K(ω)}

+α _c，2·{H _c，2，1(ω)+H _c，2，2(ω)+…+H _c，2，K(ω)}

(2)

+…

$+{\mathrm{\α}}_{c,N_R}\·\{H_{c,N_R,1}\left(\mathrm{\ω}\right)+H_{c,N_R,2}\left(\mathrm{\ω}\right)+\·\·\·+H_{c,N_R,K}\left(\mathrm{\ω}\right)\}$

$P_{k,1,c}\left({\mathrm{\γ}}_c\right)=Q\left(\sqrt{2{\mathrm{\γ}}_c}\right)---\left(3\right)$

$P_{k,m,c}\left({\mathrm{\γ}}_c\right)=4(1-\frac{1}{\sqrt{M_m}})\·Q\left(\frac{3{\mathrm{\γ}}_c}{M_m-1}\right)\·[1-(1-\frac{1}{\sqrt{M_m}})\·Q\left(\frac{3{\mathrm{\γ}}_c}{M_m-1}\right)]---\left(4\right)$

In formula (4), m=2, in the time of 3,4, M _mValue is 4,16,64 respectively.In addition, Q (x) represents integral function, and it defines shown in formula (5),

$Q\left(x\right)=\frac{1}{\sqrt{2\mathrm{\π}}}{\∫}_x^{+\∞}\exp \{-\frac{t^2}{2}\}\mathrm{dt}---\left(5\right)$

Step 102:, estimate that all (14 kinds) transmission antenna group are combined in the average error bit rate on all subcarriers at the 64QAM modulation system.

Step 103: judge the size between all average error bit rate and the target bit.If the maximum bit error rate in all bit error rates is also littler than target bit, then enter step 104, all subcarriers all are set to the 64QAM modulation system, select the minimum the sort of combination of antennas of bit error rate minimum and number of transmit antennas as final transmitting antenna configuration simultaneously, withdraw from the option program of modulation system and transmitting antenna then.Otherwise change step 105 over to.

Step 105: at the BPSK modulation system, all subcarriers that calculate in the determining step 101 are in minimum bit error rate under all possible combination of antennas and the size between the target bit, if the minimum bit error rate of all subcarriers under all possible combination of antennas that calculates in the step 101 is greater than target bit, show that then channel condition is too abominable at this moment, to such an extent as to can't transmit any information, therefore change step 106 over to, do not carry out the selection of any modulation system and transmitting antenna, directly withdraw from emitting antenna selecting and Adaptive Modulation program, otherwise change step 107 over to.

Should be noted that, above-mentioned steps 101-106, be first kind of execution mode of the present invention, the present invention also provides another kind of execution mode, that is: in step 101, only estimate each bit error rate under the high modulation rank mode, calculate average error bit rate under the high modulation rank in step 102 then, step 103 then, it is identical that action is carried out in 104 judgement, then before step 105, estimate each bit error rate under the lowest modulation rank mode again, and then execution and step 105,106 identical judgement actions, then, after step 105 is judged as not, calculate the bit error rate of all emitting antenna combination under all the other modulation levels that remove under the highest and the lowest modulation rank mode again, again with this result with calculated the highest, each bit error rate associating under the lowest modulation rank, just can obtain with first kind of execution mode under the estimated whole results that come out of step 101.

That is to say, under this execution mode, be not at the very start the bit error rate of all combination of antennas under all modulation levels all to be calculated, but substep calculates, when needs use the average error bit rate of some modulation levels, calculate the bit error rate under these rank modulation systems again, can further improve computational efficiency.

But no matter use above-mentioned any execution mode, following step all is identical.

Step 107: in all bit error rates that step 101 is calculated,, select that modulation levels is the highest at each subcarrier, under the number of transmit antennas combination of minimum less than the peak value bit error rate

Bit error rate, be denoted by ρ _{K, m, c}, in step 108, estimate the average error bit rate of MIMO ofdm system then according to formula (6) , b wherein _{M, c}Represent the transmitted bit number of c subcarrier under m kind modulation system.

$\stackrel{\‾}{P}=\left(\underset{c=1}{\overset{C}{\mathrm{\Σ}}}{b}_{m,c}{\mathrm{\ρ}}_{k,m,c}\right)/\underset{c=1}{\overset{C}{\mathrm{\Σ}}}{b}_{m,c}---\left(6\right)$

Step 109: judge average error bit rate And the size between the target bit, if average error bit rate Greater than target bit P _T, then change step 110 over to; Otherwise change step 111 over to.

Step 110: with the peak value bit error rate

Reduce a fixing value ξ, promptly $\hat{P}=\hat{P}-\mathrm{\ξ},$ Change step 112 and step 113,114 then over to, carry out respectively and step 107,108,109 similar operations, its purpose is to find the combination of one group of modulation system and subcarrier by adjusting the size of peak value bit error rate, makes average error bit rate just be lower than target bit P _TIf the average error bit rate of calculating in the step 113 is lower than target bit P _T, then entering step 115, the modulation system and the corresponding emitting antenna combination thereof that will be used to calculate this average error bit rate are transmitted, thereby withdraw from Adaptive Modulation and emitting antenna selecting process.If the average error bit rate of calculating in the step 113 is still greater than target bit P _T, then change step 110 over to, continue to carry out aforesaid operations.

Step 111: the peak value bit error rate is increased a fixing value ξ, promptly $\hat{P}=\hat{P}+\mathrm{\ξ},$ Change step 107 then over to, continue the operation of execution in step 107,108,109, just surpassed target bit P up to average error bit rate _TChange step 110 then over to, the operation of execution in step 112,113,114 is given that group for change and is made average error bit rate be about to surpass target bit P _TModulation system and corresponding transmitting antenna mode make up, the modulation system and the corresponding emitting antenna combination thereof that will be used to calculate this average error bit rate are transmitted, thereby withdraw from Adaptive Modulation and emitting antenna selecting process.

Method shown in Figure 1, its convergence rate depends on the peak value bit error rate strongly And the selection of ξ, the purpose of choosing the initial spike bit error rate is exactly by adjusting the peak value bit error rate, realizing that average error bit rate and target bit are infinitely approaching.General ξ is 5～10% of a target bit.Provide the initial spike bit error rate below

Calculation procedure, its corresponding flow process as shown in Figure 2:

Step 201: calculate the bit error rate P of all subcarriers under various emitting antenna combination and modulation system _{K, m, c}, certainly, can directly utilize the result of calculation in the step 101 here.

Step 202: at each subcarrier, at corresponding bit error rate P _{K, m, c}Less than target bit P _TCondition under, find out wherein maximum bit error rate and corresponding modulation system thereof, this bit error rate note is made α _{K, m, c}In step 203, according to same principle, at bit error rate P _{K, m, c}Greater than target bit P _TCondition under, find out wherein minimum bit error rate and corresponding modulation system thereof, this bit error rate note is made β _{K, m, c}

Step 204: all α that in step 202, find out _{K, m, c}In, with the β of a minimum identical modulation system of usefulness and subcarrier correspondence wherein _{K, m, c}Replace, and in step 205 according to formula (7), calculate average error bit rate

:

${\stackrel{\‾}{P}}_{\mathrm{\α}}=\left(\underset{c=1}{\overset{C}{\mathrm{\Σ}}}{b}_{m,c}{\mathrm{\α}}_{k,m,c}\right)/\underset{c=1}{\overset{C}{\mathrm{\Σ}}}{b}_{m,c}---\left(7\right)$

Step 206: compare average error bit rate

With target bit P _TMagnitude relationship, if average error bit rate less than target bit, then changes in the step 204, the α that all are remaining _{K, m, c}In the β of a minimum identical modulation system of usefulness and subcarrier correspondence _{K, m, c}Replace; Otherwise change step 207 over to.

Step 207: at all α _{K, m, c}(it comprises the α that is not replaced in the preceding step _{K, m, c}And the β that replaces _{K, m, c}, certainly, later β replaces _{K, m, c}Still be expressed as α _{K, m, c}) in, with size and maximum α _{K, m, c}α at the same order of magnitude _{K, m, c}The call number of corresponding subcarrier is included in the S set.

Step 208: use formula 8, utilize all α in this set _{K, m, c}Calculate the difference DELTA P of bit error rate, and store.

$\mathrm{\ΔP}=\underset{c\∈S}{\mathrm{\Σ}}{b}_{m,c}(P_T-{\mathrm{\α}}_{k,m,c})---\left(8\right)$

Step 209: with β _{K, m, c}Arrange according to incremental order, and begin stack from small to large, seek a maximum integer G, make formula 9 set up:

$\mathrm{\ΔP}\≥\underset{g=0}{\overset{G}{\mathrm{\Σ}}}{b}_{m,c}({\mathrm{\β}}_{k,m,c}-P_T)---\left(9\right)$

Step 210: under 0＜G＜C condition, β _{K, m, c}Corresponding bit error rate is exactly the initial spike bit error rate that is adopted

According to the method described in the present invention, under the certain prerequisite of the target bit of MIMO ofdm system, space diversity emitting antenna selecting and Adaptive Modulation are merged, by adjusting the peak value bit error rate, make infinitely approaching between average error bit rate and the target bit, and then realized Adaptive Modulation and emitting antenna selecting process in the MIMO ofdm system, satisfied and transmitted information maximization and the minimum purpose of number of transmit antennas.Certainly; embodiment provided by the invention is just for the method that realizes Adaptive Modulation in ofdm system that provides according to content of the present invention at large is provided; thereby all be exemplary execution mode; it can not be regarded as for restriction of the present invention; and every conspicuous modification within aim of the present invention is also due within protection scope of the present invention.

Claims (21)

1, emitting antenna selecting and the self-adaptive modulation method in a kind of multi-input multi-output orthogonal frequency division multiplexing system, at each subcarrier, adaptive emitting antenna combination and the corresponding modulation system thereof selected is characterized in that, comprises the steps:

(1),, estimates the bit error rate of all emitting antenna combination under high modulation rank at each subcarrier according to the signal to noise ratio of received signal;

(2), calculate under the high modulation rank every kind of transmission antenna group and be combined in average error bit rate on all subcarriers according to described each bit error rate of step (1);

(3) in described each average error bit rate of determining step (2) maximum bit error rate whether less than target bit, if judged result is for being, then all subcarriers are all adopted the modulation system of highest level, and select one group of minimum transmitting antenna of number of transmit antennas, as final transmission means.

2, the method for claim 1 is characterized in that, if the judged result of described step (3) then further comprises the steps: for not

(4) according to the signal to noise ratio of received signal,, estimate the bit error rate of all emitting antenna combination under the lowest modulation rank at each subcarrier;

(5) in described all bit error rates of determining step (4) minimum bit error rate whether greater than target bit, if judged result is for being then all subcarriers not to be done any emitting antenna selecting and modulation system selection.

3, method as claimed in claim 2 is characterized in that, if the judged result of described step (5) then further comprises the steps: for not

(6) according to the signal to noise ratio of received signal,, obtain the bit error rate of all emitting antenna combination under all modulation levels at each subcarrier;

(7), determine the initial spike bit error rate at each subcarrier;

(8) in described all bit error rates of step (6), at each subcarrier, select one less than when the highest bit error rate of previous peaks bit error rate, corresponding modulation levels as alternative bit error rate;

(9), calculate the average error bit rate in the whole bandwidth according to each alternative bit error rate of selecting in the step (8) at each subcarrier;

(10) whether the described average error bit rate of determining step (9) is less than target bit;

(11) if the judged result of step (10) for not, then reduces to re-execute step (8), (9), (10), (11) when the previous peaks bit error rate, until the average error bit rate of calculating less than target bit;

(12) this is calculated first, decide less than the current alternative bit error rate of each subcarrier of the average error bit rate correspondence of target bit, and the modulation system and the emitting antenna combination of described current each alternative bit error rate correspondence of deciding is chosen as final transmission means.

4, method as claimed in claim 3 is characterized in that, if the judged result of described step (10) is for being then further to comprise the steps:

(11A) increase, re-execute step (8), (9), (10), (11A), be not less than target bit until the average error bit rate of calculating when the previous peaks bit error rate;

(12A) will calculate for the last time, decide less than the current alternative bit error rate of each subcarrier of the average error bit rate correspondence of target bit, and the modulation system and the emitting antenna combination of described current each alternative bit error rate correspondence of deciding is chosen as final transmission means.

5, method as claimed in claim 3 is characterized in that, if the judged result of described step (10) is for being then further to comprise the steps:

(11B) increase, re-execute step (8), (9), (10), (11B), be not less than target bit until the average error bit rate of calculating when the previous peaks bit error rate;

(12B) reduce to re-execute step (8), (9), (10), (11) when the previous peaks bit error rate;

(13) this is calculated once more, decide less than the current alternative bit error rate of each subcarrier of the average error bit rate correspondence of target bit, and the modulation system and the emitting antenna combination of described current each alternative bit error rate correspondence of deciding is chosen as final transmission means.

6, the method for claim 1 is characterized in that, in the described step (3), if there are many group transmitting antennas all to satisfy the minimum requirement of number of transmit antennas, then selects wherein that group transmitting antenna of average error bit rate minimum.

7, method as claimed in claim 3 is characterized in that, step (6) comprising:

(6-1),, estimate the bit error rate of all emitting antenna combination under all modulation levels except that the highest and lowest modulation rank at each subcarrier according to the signal to noise ratio of received signal;

(6-2) bit error rate that step (6-1) is calculated and described step (1) are united with the bit error rate that step (4) calculates, and obtain the bit error rate of all emitting antenna combination under all modulation levels.

8, method as claimed in claim 3 is characterized in that, in the described step (8), if there are a plurality of bit error rates all to satisfy less than working as the previous peaks errored bit

And the corresponding the highest requirement of modulation levels then therefrom selects that minimum bit error rate of corresponding number of transmit antennas as alternative bit error rate again.

9, method as claimed in claim 8, it is characterized in that, in the described step (8), if there are a plurality of bit error rates all to satisfy less than when previous peaks bit error rate, corresponding high, the most corresponding minimum requirement of number of transmit antennas of modulation levels, then again from that bit error rate of wherein selecting the bit error rate minimum as alternative bit error rate.

10, method as claimed in claim 3 is characterized in that, in the described step (7), determines the step of initial spike bit error rate, comprising:

(701), obtain the bit error rate P of all emitting antenna combination under all modulation levels at each subcarrier _{K, m, c}

(702) at each subcarrier, at corresponding bit error rate P _{K, m, c}Less than target bit P _TCondition under, find out wherein maximum bit error rate and corresponding modulation system thereof, this bit error rate note is made α _{K, m, c}

(703) at each subcarrier, at bit error rate P _{K, m, c}Greater than target bit P _TCondition under, find out wherein minimum bit error rate and corresponding modulation system thereof, this bit error rate note is made β _{K, m, c}

(704) all α that in step (702), find out _{K, m, c}In, with the β of a minimum identical modulation system of usefulness and subcarrier correspondence wherein _{K, m, c}Replace;

(705) utilize formula:

${\stackrel{\‾}{P}}_{\mathrm{\α}}=\left(\underset{c=1}{\overset{C}{\mathrm{\Σ}}}{b}_{m,c}{\mathrm{\α}}_{k,m,c}\right)/\underset{c=1}{\overset{C}{\mathrm{\Σ}}}{b}_{m,c}$

Calculate average error bit rate

, wherein C is the sub-carrier number that system assignment is given a user;

(706) judge average error bit rate

Whether less than target bit P _TIf judged result is then returned step (704) for being, will remain α _{K, m, c}In the β of a minimum identical modulation system of usefulness and subcarrier correspondence _{K, m, c}Replace, repeated execution of steps (705), (706) are not until judged result;

(707) if the judged result of step (706) is not, then at all α _{K, m, c}In, with size and maximum α _{K, m, c}α at the same order of magnitude _{K, m, c}Corresponding sub-carrier indices number concentrates in the S set, and uses formula:

$\mathrm{\ΔP}=\underset{c\∈S}{\mathrm{\Σ}}{b}_{m,c}(P_T-{\mathrm{\α}}_{k,m,c})$

Calculate the difference DELTA P of bit error rate, and store, wherein b _{M, c}Represent the transmitted bit number of c subcarrier under m kind modulation system;

(708) with β _{K, m, c}Arrange according to incremental order, and begin stack from small to large, seek a maximum integer G, make formula:

$\mathrm{\ΔP}\≥\underset{g=0}{\overset{G}{\mathrm{\Σ}}}{b}_{m,c}({\mathrm{\β}}_{k,m,c}-P_T)$

Set up, then under 0＜G＜C condition, β _{K, m, c}Corresponding bit error rate is exactly the initial spike bit error rate that is adopted

As claim 3,4 or 5 described methods, it is characterized in that 11, the described amplitude of variation that reduces to work as the previous peaks bit error rate or increase when the previous peaks bit error rate is 5～10% of a target bit.

12, emitting antenna selecting and the self-adaptive modulation method in a kind of multi-input multi-output orthogonal frequency division multiplexing system, at each subcarrier, adaptive emitting antenna combination and the corresponding modulation system thereof selected is characterized in that, comprises the steps:

(1) according to the signal to noise ratio of received signal,, estimates the bit error rate of all emitting antenna combination under all modulation levels at each subcarrier;

(2), calculate under the high modulation rank every kind of transmission antenna group and be combined in average error bit rate on all subcarriers according to described each bit error rate of step (1);

(3) in described each average error bit rate of determining step (2) maximum bit error rate whether less than target bit, if judged result is for being, then all subcarriers are all adopted the modulation system of highest level, and select one group of minimum transmitting antenna of number of transmit antennas, as final transmission means.

13, method as claimed in claim 12 is characterized in that, if the judged result of described step (3) then further comprises the steps: for not

(4),, calculate the bit error rate of all emitting antenna combination under the lowest modulation rank at each subcarrier according to described each bit error rate of step (1);

(5) in described all bit error rates of determining step (4) minimum bit error rate whether greater than target bit, if judged result is for being then all subcarriers not to be done any emitting antenna selecting and modulation system selection.

14, method as claimed in claim 13 is characterized in that, if the judged result of described step (5) then further comprises the steps: for not

(6), determine the initial spike bit error rate at each subcarrier;

(7) in described all bit error rates of step (1), at each subcarrier, select one less than when the highest bit error rate of previous peaks bit error rate, corresponding modulation levels as alternative bit error rate;

(8), calculate the average error bit rate in the whole bandwidth according to each alternative bit error rate of selecting in the step (7) at each subcarrier;

(9) whether the described average error bit rate of determining step (8) is less than target bit;

(10) if the judged result of step (9) for not, then reduces to re-execute step (7), (8), (9), (10) when the previous peaks bit error rate, until the average error bit rate of calculating less than target bit;

(11) this is calculated first, decide less than the current alternative bit error rate of each subcarrier of the average error bit rate correspondence of target bit, and the modulation system and the emitting antenna combination of described current each alternative bit error rate correspondence of deciding is chosen as final transmission means.

15, method as claimed in claim 14 is characterized in that, if the judged result of described step (9) is for being then further to comprise the steps:

(10A) increase, re-execute step (7), (8), (9), (10A), be not less than target bit until the average error bit rate of calculating when the previous peaks bit error rate;

(11A) will calculate for the last time, decide less than the current alternative bit error rate of each subcarrier of the average error bit rate correspondence of target bit, and the modulation system and the emitting antenna combination of described current each alternative bit error rate correspondence of deciding is chosen as final transmission means.

16, method as claimed in claim 14 is characterized in that, if the judged result of described step (9) is for being then further to comprise the steps:

(10B) increase, re-execute step (7), (8), (9), (10B), be not less than target bit until the average error bit rate of calculating when the previous peaks bit error rate;

(11B) reduce to re-execute step (7), (8), (9), (10) when the previous peaks bit error rate;

(12) this is calculated once more, decide less than the current alternative bit error rate of each subcarrier of the average error bit rate correspondence of target bit, and the modulation system and the emitting antenna combination of described current each alternative bit error rate correspondence of deciding is chosen as final transmission means.

17, method as claimed in claim 12 is characterized in that, in the described step (3), if there are many group transmitting antennas all to satisfy the minimum requirement of number of transmit antennas, then selects wherein that group transmitting antenna of average error bit rate minimum.

18, method as claimed in claim 14 is characterized in that, in the described step (7), if there are a plurality of bit error rates all to satisfy less than working as the previous peaks errored bit

And the corresponding the highest requirement of modulation levels then therefrom selects that minimum bit error rate of corresponding number of transmit antennas as alternative bit error rate again.

19, method as claimed in claim 18, it is characterized in that, in the described step (7), if there are a plurality of bit error rates all to satisfy less than when previous peaks bit error rate, corresponding high, the most corresponding minimum requirement of number of transmit antennas of modulation levels, then again from that bit error rate of wherein selecting the bit error rate minimum as alternative bit error rate.

20, method as claimed in claim 14 is characterized in that, in the described step (6), determines the step of initial spike bit error rate, comprising:

At each subcarrier, obtain the bit error rate P of all emitting antenna combination under all modulation levels _{K, m, c}

At each subcarrier, at corresponding bit error rate P _{K, m, c}Less than target bit P _TCondition under, find out wherein maximum bit error rate and corresponding modulation system thereof, this bit error rate note is made α _{K, m, c}

At each subcarrier, at bit error rate P _{K, m, c}Greater than target bit P _TCondition under, find out wherein minimum bit error rate and corresponding modulation system thereof, this bit error rate note is made β _{K, m, c}

All α that in step (702), find out _{K, m, c}In, with the β of a minimum identical modulation system of usefulness and subcarrier correspondence wherein _{K, m, c}Replace;

Utilize formula:

${\stackrel{\‾}{P}}_{\mathrm{\α}}=\left(\underset{c=1}{\overset{C}{\mathrm{\Σ}}}{b}_{m,c}{\mathrm{\α}}_{k,m,c}\right)/\underset{c=1}{\overset{C}{\mathrm{\Σ}}}{b}_{m,c}$

Calculate average error bit rate P _α, wherein C is the sub-carrier number that system assignment is given a user;

Judge average error bit rate P _αWhether less than target bit P _TIf judged result is then returned step (704) for being, will remain α _{K, m, c}In the β of a minimum identical modulation system of usefulness and subcarrier correspondence _{K, m, c}Replace, repeated execution of steps (705), (706) are not until judged result;

If the judged result of step (706) is for not, then at all α _{K, m, c}In, with size and maximum α _{K, m, c}α at the same order of magnitude _{K, m, c}Concentrate in the set, the call number of its respective sub is included in the S set, and uses formula:

$\mathrm{\ΔP}=\underset{c\∈S}{\mathrm{\Σ}}{b}_{m,c}(P_T-{\mathrm{\α}}_{k,m,c})$

Calculate the difference DELTA P of bit error rate, and store, wherein b _{M, c}Represent the transmitted bit number of c subcarrier under m kind modulation system;

With β _{K, m, c}Arrange according to incremental order, and begin stack from small to large, seek a maximum integer G, make formula:

$\mathrm{\ΔP}\≥\underset{g=0}{\overset{G}{\mathrm{\Σ}}}{b}_{m,c}({\mathrm{\β}}_{k,m,c}-P_T)$

Set up, then under 0＜G＜C condition, β _{K, m, c}Corresponding bit error rate is exactly the initial spike bit error rate that is adopted

As claim 14,15 or 16 described methods, it is characterized in that 21, the described amplitude of variation that reduces to work as the previous peaks bit error rate or increase when the previous peaks bit error rate is 5～10% of a target bit.

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