CN110445737A - OFDM peak-to-average power ratio based on two stages index modulation reduces method and system - Google Patents
OFDM peak-to-average power ratio based on two stages index modulation reduces method and system Download PDFInfo
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- CN110445737A CN110445737A CN201910613902.5A CN201910613902A CN110445737A CN 110445737 A CN110445737 A CN 110445737A CN 201910613902 A CN201910613902 A CN 201910613902A CN 110445737 A CN110445737 A CN 110445737A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2614—Peak power aspects
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
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Abstract
The invention discloses a kind of, and the OFDM peak-to-average power ratio based on two stages index modulation reduces method and system.In the first stage in index modulation, portion subcarriers activation is used for transmission data according to index bit information by each ofdm signal subframe, in second stage index modulation, according to more index bit information, selected section subcarrier is activated and is transmitted data again from first stage unactivated subcarrier, the main purpose of second stage index modulation is to reduce the peak-to-average power ratio of two stages index modulation ofdm system and improve spectrum efficiency, while a kind of searching algorithm for being simply to reduce peak-to-average power ratio is used.Receiving end uses Maximum Likelihood Detection, will comprehensively consider index pattern and mapping signal carries out detection and the recovery of bit information.The method and system proposed can effectively reduce the peak-to-average power ratio performance of two stages index modulation OFDM, and the spectrum efficiency of system, power efficiency and performance of BER all make moderate progress.
Description
Technical field
The present invention relates to wireless communication technology fields, and in particular to a kind of orthogonal frequency division multiplexing based on two stages index modulation
Method and system is reduced with (OFDM) peak-to-average power ratio (PAPR).
Background technique
In wireless communication field, due to the excellent of high spectrum utilization, effective anti-multipath and mitigating frequency-selective fading
Point, the OFDM technology based on index modulation are widely studied and are applied, even for the 5th generation (5G) mobile communication
It is that an advantageous technology is candidate.Index modulation OFDM technology can effectively improve band system band utilization rate and send end signal
Power efficiency, it is other since an ofdm signal based on index modulation only has portion subcarriers to be activated for transmitting information
Subcarrier is 0, and more sends bit information and lie in index information, that is, utilizes the bit information determinant sent
The active style of carrier wave.In order to further increase the spectrum efficiency of system, bimodulus index modulation OFDM technology is suggested, uses
For two kinds of planispheres for mapping data, the activation subcarrier elected by index information realizes mapping process with planisphere A,
And remaining subcarrier realizes mapping process with planisphere B, the signaling point in two kinds of planispheres here is mutually disjoint.
However, the ofdm system based on index modulation inherits the excessively high disadvantage of conventional OFDM systems PAPR, high PAPR is wanted
The very big range of linearity will be had by seeking the power amplifier of system transmitting terminal, and the ofdm signal to avoid transmission is more than maximum line
Distorted signals caused by property range, and the range of linearity cost for increasing power amplifier is excessively high.Some common ofdm systems
It includes chopping techniques, Choose for user, partial transmission sequence and virtual sequence insertion technology etc. that PAPR, which reduces method,.One kind is suitable for
PAPR reduction method based on index modulation ofdm system has to be developed.
Summary of the invention
The technical problem to be solved in the present invention is that reducing the PAPR of index modulation ofdm system, improving tradition index tune
The band efficiency of ofdm system processed, the power efficiency for improving bimodulus index modulation ofdm system and raising index modulation OFDM system
The performance of BER of system provides a kind of OFDM based on two stages index modulation and its PAPR reduction method and system.
The one aspect for the technical issues of solving according to the present invention, a kind of equal function in the peak OFDM based on two stages index modulation
Rate includes the following steps: than reduction method
(1) serioparallel exchange and bit groupings: binary sequence to be sent is passed through into serioparallel exchange, serial bit number
Parallel data stream is changed into according to circulation, wherein every p bit is one group of subframe for being input to a frame ofdm signal, a frame packet here
Ofdm signal containing N number of subcarrier is divided into G=N/n subframe, Gg=[Xg,1Xg,2…Xg,n] g-th of subframe of expression, 1≤g≤
G, n are the subcarrier number that each subframe includes, and X indicates the subcarrier in a frame ofdm signal.
(2) first stage index modulation: by the preceding p in step (1) in every group of p bit1A bit inputs first stage rope
Draw selector, selects the subcarrier activated in each subframe of ofdm signal, i.e. p1A bit determines GgThe activation sample of sub-carriers
Formula, then by the p in step (1) in every group of p bit2A bit input mapper A is mapped.
(3) second stage index modulation: by the p in step (1) in every group of p bit3A bit input second stage index
Selector, the G from step (2)gIn select subcarrier to be activated again in unactivated subcarrier, then will be every in step (1)
P in group p bit4A bit input mapper B is mapped.
(4) frequency domain ofdm signal generates, according to the sub-carrier activation pattern in step (2) and (3), by every group of p of step (1)
P in bit2+p4A bit is mapped on corresponding activation subcarrier by mapper A and mapper B.
(5) when the frequency domain ofdm signal that step (4) obtains being transformed by the inverse discrete fourier transform (IDFT) of N point
Domain.
(6) time domain OFDM signal obtained step (5) inputs peak-to-average power ratio comparator, finds the by searching algorithm
The optimal combination of second order segment signal mapping, minimizes PAPR.
(7) time domain OFDM signal for the minimum PAPR for obtaining step (6) is by parallel-serial conversion plus cyclic prefix, number
Channel is sent into after mould conversion and upconversion process to be transmitted.
(8) in receiving end, received ofdm signal is subjected to down coversion, analog-to-digital conversion, removes cyclic prefix and serioparallel exchange
Processing.
(9) output signal of step (8) is subjected to discrete Fourier transform (DFT), time domain OFDM signal is transformed into frequency
Domain.
(10) output signal of step (9) Maximum Likelihood Detection, solution index and demapping is carried out to handle, revert to two into
Information processed.
(11) output signal of step (10) is subjected to parallel-serial conversion, obtains originally transmitted binary sequence.
Further, in the OFDM peak-to-average power ratio reduction method of the invention based on two stages index modulation, step (1)
In a frame ofdm signal each subframe in include bit number p=p1+p2+p3+p4, wherein preceding p1A bit and p3A bit point
It is not input to first stage selector and second stage selector, for selecting each subframe neutron of ofdm signal to carry
The active style of wave, p2A bit and p4A bit is separately input to mapper A and mapper B and maps for signal, p1、p2、p3
And p4Corresponding bit information is arranged successively.
Further, in the OFDM peak-to-average power ratio reduction method of the invention based on two stages index modulation, step (2)
First stage index modulation, be to select k subcarrier from n subcarrier of each subframe, be used for mapped bits information, institute
With:
p2=klog2MA
In formulaIt indicates stage function, i.e., is rounded downwards, C (n, k) indicates binomial coefficient, i.e., takes the combination of k from n
Number, while meeting k < n, MAIndicate the size of the planisphere used in mapper A.By p1The index information that a bit information determines
For IA=[IA,1IA,2…IA,k], by p2The signal that a bit information determines is SA=[S (IA,1)S(IA,2)…S(IA,k)]。
Further, in the OFDM peak-to-average power ratio reduction method of the invention based on two stages index modulation, step (3)
Second stage index modulation, be to select a subcarrier of k ' again in the n-k subcarriers not being activated in step (2) to be used for
Mapped bits information, so:
p4=k'log2(MB/u)
M in formulaBIndicate the size of the planisphere used in mapper B, every u signaling point indicates same in planisphere B
Bit information is randomly selected when mapping for the first time for reducing the PAPR of system.Signaling point in planisphere B and planisphere A
It mutually disjoints, while meeting k+k ' < n, guarantee with the presence of 0 carrier wave, that is, unactivated subcarrier, to improve the power effect of system
Rate.By p3The index information I that a bit information determinesB=[IB,1IB,2…IB,k’], by p4The signal S that a bit information determinesB=
[S(IB,1)S(IB,2)…S(IB,k’)]。
Further, in the OFDM peak-to-average power ratio reduction method of the invention based on two stages index modulation, step (4)
Frequency domain ofdm signal generator is according to the sub-carrier activation pattern in step (2) and (3), by the S in step (2) and (3)AWith
SBCorresponding activation subcarrier I is mapped to by mapper A and mapper BAAnd IBOn.
Further, in the OFDM peak-to-average power ratio reduction method of the invention based on two stages index modulation, step (5)
The time domain OFDM signal of output can indicate are as follows:
xT=[x0 x1 ... xN-1]=IDFT { XT}=IDFT { [X0 X1 ... XN-1]}
IDFT { } indicates inverse discrete fourier transform operation, X in formulaT=[X0X1…XN-1] indicate the frequency-domain OFDM sent letter
Number, including signaling point and 0 carrier wave from planisphere A and planisphere B.
Further, in the OFDM peak-to-average power ratio reduction method of the invention based on two stages index modulation, step (6)
It is that the time domain OFDM signal PAPR sent minimizes process, includes the following steps:
(61) initial PAPR value papr is calculated, variable i=1, ii=1, g=1 are set；
(62) S is usedi,g(IB,ii) instead of the signal on original corresponding subcarrier, then new PAPR value is recalculated, if
PAPR is reduced, and uses Si,g(IB,ii) the original signaling point of replacement, and new PAPR value is assigned to papr, otherwise signaling point is constant, Si,g
(IB,ii) each subframe is represented in second stage index modulation by one of mapper B optional signal mapped；
(63) i=i+1, return step (62), until i=u terminates, 1≤i≤u indicates swashing for each subframe of second stage
The optional signal index of mapped on subcarrier living；
(64) ii=ii+1, return step (62), until ii=k ' terminates, 1≤ii≤k ' indicates the every height of second stage
The activation sub-carrier indices of frame；
(65) g=g+1, return step (62), until g=G terminates, 1≤g≤G indicates the subframe rope of a frame ofdm signal
Draw.
Further, in the OFDM peak-to-average power ratio reduction method of the invention based on two stages index modulation, step
(61) calculation formula of PAPR value in are as follows:
Expectation is asked in E { } expression in formula, and max { } indicates maximizing.
Further, in the OFDM peak-to-average power ratio reduction method of the invention based on two stages index modulation, step
(10) Maximum Likelihood Detection is used in, according to step (2) and step (3), detection process will comprehensively consider every frame ofdm signal
The signal of frame all possible sub-carrier activation pattern and mapping, specific detection process can indicate are as follows:
X in formulaRIndicate that received subcarrier in frequency domain signal, H indicate that the channel fading coefficient of frequency domain, subscript g indicate each
G-th of subframe of ofdm signal,The index information of each subframe in receiving end and the estimated value of mapping signal are respectively indicated,
Further according to the index information and signal of detection, solution index and demapping are carried out by look-up table, restore binary message.
Further, in the OFDM peak-to-average power ratio reduction method of the invention based on two stages index modulation, pass through step
Suddenly the index modulation process in two stages of (1) to step (7), the OFDM band efficiency of proposition may be expressed as:
L in formulaCPIndicate the length of the cyclic prefix of addition, G indicates the number of sub-frames of each ofdm signal.
The another aspect for the technical issues of solving according to the present invention additionally provides a kind of based on two stages index modulation
OFDM peak-to-average power ratio reduces system, and the module and function for mainly including are described as follows:
Transmitting terminal serioparallel exchange and bit groupings module, for binary sequence to be sent to be passed through serioparallel exchange,
Serial bit data flow is converted into parallel data stream, wherein every p bit is one group of son for being input to a frame ofdm signal
Frame, a frame includes that the ofdm signal of N number of subcarrier is divided into G=N/n subframe, G hereg=[Xg,1Xg,2…Xg,n] indicate g
A subframe, 1≤g≤G, n are the subcarrier number that each subframe includes, and X indicates the subcarrier in a frame ofdm signal.
First stage selector module, for according to the preceding p in every group of p bit1A bit selection ofdm signal
Sub-carrier activation pattern in each subframe.
Mapper A module, for passing through A mapper for the p in every group of p bit2A bit map is to the letter in planisphere A
Number point.
Second stage selector module, for according to the p in every group of p bit3A bit is from first stage every height
The active style of subcarrier is selected in the unactivated subcarrier of frame again.
Mapper B module, for passing through B mapper for the p in every group of p bit4A bit map is to the letter in planisphere B
Number point, the signaling point in planisphere B mutually disjoint with the signaling point in planisphere A.
Frequency domain ofdm signal maker module, for indexing the activation elected according to first stage index and second stage
Subcarrier is mapped to signal on the activation subcarrier of ofdm signal by mapper A and mapper B respectively.
N point IDFT module, for the frequency domain ofdm signal obtained by two stages index modulation to be turned by IDFT module
Change to time domain.
Peak-to-average power ratio comparator module, for making OFDM by searching algorithm Choose for user device B mapped signaling point
The PAPR of signal is minimized.
Transmitting terminal parallel-serial conversion plus cyclic prefix, digital-to-analogue conversion and up-converter module, the time domain for being generated to transmitting terminal
Ofdm signal carries out parallel-serial conversion, addition cyclic prefix, digital signal to analog signal conversion and upconversion process.
Receiving end down coversion, removes cyclic prefix and serioparallel exchange module at analog-to-digital conversion, for the time domain OFDM received
Signal carries out down coversion, analog signal to digital signal is converted, removal cyclic prefix and serioparallel exchange are handled.
N point DFT block, for the time domain OFDM signal received to be transformed into frequency domain.
Maximum Likelihood Detection, solution index and De-mapping module, for comprehensively considering every frame OFDM using Maximum Likelihood Detection
The signal of all possible sub-carrier activation pattern and mapping in signal subframe searches for all possible situation to detect sub- load
Wave active style and each activation subcarrier mapped signal, then binary system letter is restored by solution index and demapping processing
Breath.
Receiving end parallel serial conversion module, the binary message for that will restore carry out parallel-serial conversion, restore originally transmitted
Binary sequence.
The OFDM peak-to-average power ratio that the invention proposes a kind of based on two stages index modulation reduces method and system, the
One stage is consistent with traditional index modulation OFDM, by the index modulation of second stage, is found using searching algorithm optimal
Signal mapping, minimizes the PAPR value for sending ofdm signal, while increasing transmitted bit information, the index including second stage
Bit and signal bit, to improve the spectral frequencies of system under conditions of not changing ofdm signal subcarrier number.Together
When, whole sub-carrier activations of each subframe of ofdm signal are not used for transmission data in second stage, but remain one
A little carrier wave is 0, sends ofdm signal power efficiency to improve.
Detailed description of the invention
Fig. 1 is that the present invention is based on the OFDM peak-to-average power ratios of two stages index modulation to reduce system transmitting terminal block diagram.
Fig. 2 is that the present invention is based on the OFDM peak-to-average power ratios of two stages index modulation to reduce system receiving terminal block diagram.
Fig. 3 is planisphere A and planisphere B in the embodiment of the present invention.
Fig. 4 is that the two stages index modulation OFDM peak-to-average power ratio of the embodiment of the present invention reduces system performance of BER song
Line schematic diagram.
Fig. 5 is that the two stages index modulation OFDM peak-to-average power ratio of the embodiment of the present invention reduces the performance curve of system PAPR
Schematic diagram.
Specific embodiment
In order to there are more clear understanding and understanding to the technical features, objects and effects of the invention, it is detailed now to compare attached drawing
Describe bright a specific embodiment of the invention in detail.
Fig. 1 and Fig. 2 are please referred to, Fig. 1 show the peak the OFDM equal power proposed by the present invention based on two stages index modulation
Than reducing system transmitting terminal block diagram, including serioparallel exchange and bit groupings module, first stage selector module, second-order
Segment index selector module, mapper A module, mapper B module, frequency domain ofdm signal maker module, N point IDFT module,
Peak-to-average power ratio comparator module, parallel-serial conversion plus cyclic prefix, digital-to-analogue conversion and up-converter module.Fig. 2 show the present invention
The OFDM peak-to-average power ratio based on two stages index modulation proposed reduces system receiving terminal block diagram, including down coversion, modulus turn
It changes, remove cyclic prefix and serioparallel exchange module, N point DFT block, Maximum Likelihood Detection, solution index and De-mapping module, and go here and there and turn
Change the mold block.
The sub-carrier number of an ofdm signal is set as N, the frequency domain ofdm signal of such a transmission can be expressed as XT
=[X0 X1 … XN-1], each ofdm signal subcarrier is divided into G=N/n subgroup, each subgroup i.e. ofdm signal
Frame, n are the sub-carrier number that each subframe includes, and each ofdm signal subframe carries p=p1+p2+p3+p4The information of a bit, p1、
p2、p3And p4Corresponding bit information is arranged successively, and each ofdm signal includes m=pG bit information, p altogether here1、p2、
p3And p4It is positive integer.
In the OFDM peak-to-average power ratio reduction method of the invention based on two stages index modulation, comprising the following steps:
(1) serioparallel exchange and bit groupings: binary sequence to be sent is passed through into serioparallel exchange, serial bit number
Parallel data stream is changed into according to circulation, wherein every p bit is one group of subframe for being input to ofdm signal, a frame ofdm signal quilt
It is divided into G subframe, Gg=[Xg,1 Xg,2 … Xg,n] (1≤g≤G) indicate ofdm signal g-th of subframe, X indicate a frame
Subcarrier in ofdm signal, n are the sub-carrier number that subframe includes.For p bit information for including in each subframe, wherein
Preceding p1A bit and p3A bit is separately input to first stage selector and second stage selector, for selecting
The active style of each subframe sub-carriers of ofdm signal, p2A bit and p4A bit is separately input to mapper A and mapper
B is mapped for signal.
(2) first stage index modulation: by the preceding p in step (1) in every group of p bit1A bit inputs first stage rope
Draw selector, selects the subcarrier activated in each subframe of ofdm signal, i.e. p1A bit determines GgThe activation sample of sub-carriers
Formula, the sub-carrier indices I being activatedAIt indicates, then by p in step (1) in every group of p bit2A bit inputs mapper A
It is mapped, the signal S for mappingATo indicate.First stage index modulation is from n subcarrier of each subframe
K subcarrier is selected, mapped bits information, p are used for1And p2It may be calculated:
p2=k log2MA
In formulaIt indicates stage function, i.e., is rounded downwards, C (n, k) indicates binomial coefficient, i.e., takes the combination of k from n
Number, while meeting k < n, MAIndicate the size of the planisphere used in mapper A, mapper A can use BPSK constellation here
Figure, QPSK planisphere etc..By p1The index information that a bit information determines is IA=[IA,1IA,2…IA,k], by p2A bit information
The signal of decision is SA=[S (IA,1)S(IA,2)…S(IA,k)].Work as n=4, k=1, p1When=2, swash in index bit and subframe
The corresponding relationship of subcarrier living can be indicated by table 1.
Table 1
| Index bit | Index | Subframe |
| 0 0 | 1 | [SA 0 0 0] |
| 0 1 | 2 | [0 SA 0 0] |
| 1 0 | 3 | [0 0 SA 0] |
| 1 1 | 4 | [0 0 0 SA] |
(3) second stage index modulation: by the p in step (1) in every group of p bit3A bit input second stage index
Selector, the G from step (2)gIn select subcarrier to be activated again in unactivated subcarrier, the subcarrier rope being activated
Quote IBIt indicates, then by p in step (1) in every group of p bit4A bit input mapper B is mapped, for mapping
Signal SBTo indicate.Second stage index modulation is selected again in-k subcarriers not being activated of n in step (2)
A subcarrier of k ' is used for mapped bits information, p3And p4It may be calculated:
p4=k'log2(MB/u)
M in formulaBIndicate the size of the planisphere used in mapper B, every u signaling point indicates same in planisphere B
Bit information is randomly selected when mapping for the first time for reducing the PAPR of system.Signaling point in planisphere B and planisphere A
It mutually disjoints, while meeting k+k ' < n, guarantee with the presence of 0 carrier wave, that is, unactivated subcarrier, to improve the power effect of system
Rate.By p3The index information I that a bit information determinesB=[IB,1IB,2…IB,k’], by p4The signal S that a bit information determinesB=
[S(IB,1)S(IB,2)…S(IB,k’)].Mapper B can be using QPSK planisphere, 8PSK planisphere etc., in order not to reduce system
Spectrum efficiency and reduce PAPR, the size of planisphere B can be greater than planisphere A.In the first stage on the basis of index modulation,
Work as k '=1, p3When=1, index bit activates the corresponding relationship of subcarrier that can be indicated by table 2 with subframe.
Table 2
If carrying out data mapping using QPSK planisphere in mapper B, signaling point (d, d) and (- d ,-d) are represented
Same bit information, (- d, d) and (d ,-d) represent same bit information, and the PAPR for index modulation ofdm system drops
It is low, as shown in figure 3, wherein hollow signal indicates that planisphere A, solid signal indicate planisphere B.
(4) frequency domain ofdm signal generates, and frequency domain ofdm signal generator is swashed according to the subcarrier in step (2) and (3)
Pattern living, by the S in step (2) and (3)AAnd SBCorresponding activation subcarrier I is mapped to by mapper A and mapper BAWith
IBOn.
(5) when the frequency domain ofdm signal that step (4) obtains being transformed by the inverse discrete fourier transform (IDFT) of N point
The time domain OFDM signal in domain, output can indicate are as follows:
xT=[x0 x1 ... xN-1]=IDFT { XT}=IDFT { [X0 X1 ... XN-1]}
IDFT { } indicates inverse discrete fourier transform operation, X in formulaTIncluding the signaling point from planisphere A and planisphere B
With 0 carrier wave.
(6) time domain OFDM signal obtained step (5) inputs peak-to-average power ratio comparator, finds the by searching algorithm
The optimal combination of second order segment signal mapping, minimizes PAPR.The PAPR for sending ofdm signal minimizes process, including walks as follows
It is rapid:
(61) initial PAPR value papr, calculation formula are calculated are as follows:
Expectation is asked in E { } expression in formula, and max { } indicates maximizing, sets variable i=1, ii=1, g=1；
(62) S is usedi,g(IB,ii) instead of the signal on original corresponding subcarrier, then new PAPR value is recalculated, if
PAPR is reduced, and uses Si,g(IB,ii) the original signaling point of replacement, and new PAPR value is assigned to papr, otherwise signaling point is constant, Si,g
(IB,ii) each subframe is represented in second stage index modulation by one of mapper B optional signal mapped；
(63) i=i+1, return step (62), until i=u terminates, 1≤i≤u indicates swashing for each subframe of second stage
The optional signal index of mapped on subcarrier living；
(64) ii=ii+1, return step (62), until ii=k ' terminates, 1≤ii≤k ' indicates the every height of second stage
The activation sub-carrier indices of frame；
(65) g=g+1, return step (62), until g=G terminates, 1≤g≤G indicates the subframe rope of a frame ofdm signal
Draw.
(7) by step (6) obtain minimum PAPR time domain OFDM signal by parallel-serial conversion, addition cyclic prefix,
Channel is sent into after digital-to-analogue conversion and upconversion process to be transmitted.Pass through the index tune in two stages of step (1) to step (7)
The OFDM band efficiency of process processed, proposition may be expressed as:
L in formulaCPIndicate the length of the cyclic prefix of addition, G indicates the number of sub-frames of each ofdm signal.
(8) in receiving end, received ofdm signal is subjected to down coversion, analog-to-digital conversion, removal cyclic prefix and string and is turned
Change processing.
(9) output signal of step (8) is subjected to discrete Fourier transform (DFT), time domain OFDM signal is transformed into frequency
Domain.
(10) output signal of step (9) Maximum Likelihood Detection, solution index and demapping is carried out to handle, revert to two into
Information processed.According to step (2) and step (3), Maximum Likelihood Detection process will comprehensively consider that every frame ofdm signal subframe is all can
The sub-carrier activation pattern of energy and the signal of mapping, specific detection process can indicate are as follows:
X in formulaRIndicate that received subcarrier in frequency domain signal, H indicate that the channel fading coefficient of frequency domain, subscript g indicate each
G-th of subframe of ofdm signal,Respectively indicate the estimation of the index information and mapping signal of each subframe in receiving end
Value carries out solution index and demapping by look-up table, restores binary message further according to the index information and signal of detection.
(11) output signal of step (10) is subjected to parallel-serial conversion, obtains originally transmitted binary sequence.
Embodiment:
Design parameter scheme: the sub-carrier number N=128 of an ofdm signal, the number of sub-frames G=of each ofdm signal
32, the sub-carrier number n=4 in each subframe, the subcarrier number k=1 that the first stage is activated, the son that second stage is activated
Variable number k '=1, mapper A use BPSK planisphere, i.e. MA=2, mapper B use QPSK planisphere, i.e. MB=4, u=2
Mean to take two signaling points in QPSK planisphere on diagonal line to represent same bit information, as shown in figure 3, for passing through
The distance that searching algorithm reduces adjacent signaling point in the PAPR, planisphere B and planisphere A of ofdm signal is d, the length of cyclic prefix
Spend LCP=16.In the case where not considering that PAPR is reduced, each subframe may include 6 bit informations, and the spectrum efficiency of system can
1.3333 bps/hertz are calculated to obtain, in the case where considering that PAPR is reduced, each subframe includes 5 bit informations, system
Spectrum efficiency can calculate to obtain 1.1111 bps/hertz.Channel uses frequency selectivity Rayleigh fading channel, and wherein Rayleigh is believed
The channel impulse response length in road is 10.
Simulation result is as shown in Figure 4 and Figure 5, and Fig. 4 horizontal axis indicates signal-to-noise ratio, i.e. the every bit power of signal than noise power,
The longitudinal axis is bit error rate.In order to prove advantage of the invention, under the conditions of identical spectrum efficiency, Fig. 4 also provides traditional rope
Draw the simulation result of modulation OFDM and bimodulus index modulation OFDM, the sub-carrier number of each subframe is 4, traditional index modulation
Ofdm system carries out signal mapping using 16QAM, has k=1 subcarrier to be activated in each subframe；In bimodulus index modulation
In ofdm system, Mode A uses BPSK planisphere, Mode B use with the mutually perpendicular BPSK planisphere of A, signal power is big
Signal in Mode A, wherein k=2 subcarrier Mode A maps data, other two subcarrier maps number using Mode B
According to.It is proposed by the invention based on two stages index modulation it can be seen from simulation result under the conditions of identical spectrum efficiency
The performance of BER of ofdm system be better than traditional ofdm system based on index modulation.Considering PAPR reduction algorithm
In the case where, the OFDM peak-to-average power ratio of two stages index modulation proposed by the present invention, which reduces system, can also provide preferably accidentally ratio
Special rate performance, but the spectrum efficiency of system has a little decline, but PAPR performance can improve about compared with classical ofdm system
5dB。
Compared with prior art, the present invention has the following effects that gain: in terms of peak-to-average power ratio reduction, the present invention is proposed
OFDM peak-to-average power ratio based on two stages index modulation reduce system and can effectively improve system PAPR performance；Improving frequency
In terms of band utilization rate, the OFDM peak-to-average power ratio proposed by the present invention based on two stages index modulation reduces system, in the first rank
Section is consistent with traditional index modulation OFDM, increases transmitted bit information, including second by the index modulation of second stage
The index bit and signal bit in stage, to improve the frequency of system under conditions of not changing ofdm signal subcarrier number
Spectral frequency, while reaching by searching algorithm the function of improvement system PAPR；In terms of the transmission power efficiency of transmitting terminal, this hair
The OFDM peak-to-average power ratio based on two stages index modulation of bright proposition reduces system, every not by ofdm signal in second stage
All activation is used for transmission data to unactivated subcarrier to a subframe in the first stage, but retaining some subcarriers is 0, with biography
The bimodulus index modulation OFDM technology of system is compared, and the power efficiency for sending ofdm signal can be improved.Meanwhile in spectrum efficiency phase
With under conditions of, or (using a little reduction spectrum efficiency as cost) in the case where consideration PAPR reduction, system proposed by the present invention
More traditional index modulation OFDM and bimodulus index modulation ofdm system has better performance of BER.
The embodiment of the present invention is described with above attached drawing, but the invention is not limited to above-mentioned specific
Embodiment, the above mentioned embodiment is only schematical, rather than restrictive, those skilled in the art
Under the inspiration of the present invention, without breaking away from the scope protected by the purposes and claims of the present invention, it can also make very much
Form, all of these belong to the protection of the present invention.
Claims (10)
1. a kind of OFDM peak-to-average power ratio based on two stages index modulation reduces method, which is characterized in that comprise the following steps:
(1) serioparallel exchange and bit groupings: binary sequence to be sent is passed through into serioparallel exchange, serial bit data flow
It is converted into parallel data stream, wherein every p bit is one group of subframe for being input to a frame ofdm signal, a frame includes N here
The ofdm signal of a subcarrier is divided into G=N/n subframe, Gg=[Xg,1 Xg,2 … Xg,n] g-th of subframe of expression, 1≤g≤
G, n are the subcarrier number that each subframe includes, and X indicates the subcarrier in a frame ofdm signal；
(2) first stage index modulation: by the preceding p in step (1) in every group of p bit1A bit inputs first stage index selection
Device selects the subcarrier activated in each subframe of ofdm signal, i.e. p1A bit determines GgThe active style of sub-carriers, then
By the p in step (1) in every group of p bit2A bit input mapper A is mapped；
(3) second stage index modulation: by the p in step (1) in every group of p bit3A bit inputs second stage index selection
Device, the G from step (2)gIn select subcarrier to be activated again in unactivated subcarrier, then by every group of p ratio in step (1)
P in spy4A bit input mapper B is mapped；
(4) frequency domain ofdm signal generates, according to the sub-carrier activation pattern in step (2) and (3), by every group of p bit of step (1)
In p2+p4A bit is mapped on corresponding activation subcarrier by mapper A and mapper B；
(5) frequency domain ofdm signal that step (4) obtains is transformed into time domain by the inverse discrete fourier transform of N point；
(6) time domain OFDM signal for obtaining step (5) inputs peak-to-average power ratio comparator, finds second-order by searching algorithm
The optimal combination of segment signal mapping, minimizes PAPR；
(7) time domain OFDM signal for the minimum PAPR that step (6) obtains is turned by parallel-serial conversion plus cyclic prefix, digital-to-analogue
It changes and is transmitted with feeding channel after upconversion process；
(8) in receiving end, received ofdm signal is subjected to down coversion, analog-to-digital conversion, cyclic prefix and serioparallel exchange is gone to handle；
(9) output signal of step (8) is subjected to discrete Fourier transform, time domain OFDM signal is transformed into frequency domain；
(10) output signal of step (9) is carried out Maximum Likelihood Detection, solution index and demapping to handle, reverts to binary system letter
Breath；
(11) output signal of step (10) is subjected to parallel-serial conversion, obtains originally transmitted binary sequence.
2. the OFDM peak-to-average power ratio according to claim 1 based on two stages index modulation reduces method, feature exists
In the bit number p=p for including in each subframe of a frame ofdm signal in step (1)1+p2+p3+p4, wherein preceding p1A bit and
p3A bit is separately input to first stage selector and second stage selector, for selecting ofdm signal each
The active style of subframe sub-carriers, p2A bit and p4A bit is separately input to mapper A and mapper B is reflected for signal
It penetrates, p1、p2、p3And p4Corresponding bit information is arranged successively.
3. the OFDM peak-to-average power ratio according to claim 1 based on two stages index modulation reduces method, feature exists
In the first stage index modulation of step (2) is to select k subcarrier from n subcarrier of each subframe, for mapping
Bit information, so:
p2=k log2 MA
In formulaIt indicates stage function, i.e., is rounded downwards, C (n, k) indicates binomial coefficient, i.e., takes the number of combinations of k from n, together
When meet k < n, MAThe size for indicating the planisphere used in mapper A, by p1The index information that a bit information determines is IA=
[IA,1 IA,2 … IA,k], by p2The signal that a bit information determines is SA=[S (IA,1) S(IA,2) … S(IA,k)]。
4. the OFDM peak-to-average power ratio according to claim 1 based on two stages index modulation reduces method, feature exists
It is that select k ' again in-k subcarriers not being activated of n in step (2) a in, the second stage index modulation of step (3)
Subcarrier is used for mapped bits information, so:
p4=k'log2(MB/u)
M in formulaBIndicate the size of the planisphere used in mapper B, every u signaling point indicates same bit letter in planisphere B
Breath is randomly selected when mapping for the first time for reducing the PAPR of system, the mutual not phase of the signaling point in planisphere B and planisphere A
It hands over, while meeting k+k ' < n, guarantee with the presence of 0 carrier wave, that is, unactivated subcarrier, to improve the power efficiency of system, by p3
The index information I that a bit information determinesB=[IB,1 IB,2 … IB,k’], by p4The signal S that a bit information determinesB=[S
(IB,1) S(IB,2) … S(IB,k’)]。
5. the OFDM peak-to-average power ratio according to claim 1 based on two stages index modulation reduces method, feature exists
In, step (4) frequency domain ofdm signal generator be according to the sub-carrier activation pattern in step (2) and (3), by step (2) and
(3) S inAAnd SBCorresponding activation subcarrier I is mapped to by mapper A and mapper BAAnd IBOn.
6. the OFDM peak-to-average power ratio according to claim 1 based on two stages index modulation reduces method, feature exists
In the time domain OFDM signal of step (5) output are as follows:
xT=[x0 x1 ... xN-1]=IDFT { XT}=IDFT { [X0 X1 ... XN-1]}
IDFT { } indicates inverse discrete fourier transform operation, X in formulaT=[X0 X1 … XN-1] indicate the frequency-domain OFDM sent letter
Number, including signaling point and 0 carrier wave from planisphere A and planisphere B.
7. OFDM peak-to-average power ratio according to claim 1 reduces method, which is characterized in that step (6) is to send OFDM
The PAPR of signal minimizes process, includes the following steps:
(61) initial PAPR value papr is calculated, variable i=1, ii=1, g=1, the calculation formula of PAPR value are set are as follows:
Expectation is asked in E { } expression in formula, and max { } indicates maximizing；
(62) S is usedi,g(IB,ii) instead of the signal on original corresponding subcarrier, then new PAPR value is recalculated, if PAPR drops
It is low, use Si,g(IB,ii) the original signaling point of replacement, and new PAPR value is assigned to papr, otherwise signaling point is constant, Si,g(IB,ii) represent
Each subframe passes through one of mapper B optional signal mapped in second stage index modulation；
(63) i=i+1, return step (62), until i=u terminates, 1≤i≤u indicates activation of each subframe of second stage
The optional signal index of mapped on carrier wave；
(64) ii=ii+1, return step (62), until ii=k ' terminates, 1≤ii≤k ' indicates each subframe of second stage
Activate sub-carrier indices；
(65) g=g+1, return step (62), until g=G terminates, 1≤g≤G indicates the subframe index of a frame ofdm signal.
8. the OFDM peak-to-average power ratio according to claim 1 based on two stages index modulation reduces method, feature exists
In using Maximum Likelihood Detection in step (10), according to step (2) and step (3), detection process will comprehensively consider every frame OFDM
The signal of signal subframe all possible sub-carrier activation pattern and mapping, specific detection process indicate are as follows:
X in formulaRIndicate that received subcarrier in frequency domain signal, H indicate that the channel fading coefficient of frequency domain, subscript g indicate each OFDM letter
Number g-th of subframe,The index information of each subframe in receiving end and the estimated value of mapping signal are respectively indicated, further according to
The index information and signal of detection carry out solution index and demapping by look-up table, restore binary message.
9. the OFDM peak-to-average power ratio according to claim 1 based on two stages index modulation reduces method, feature exists
In, pass through step (1) to step (7) two stages index modulation process, the OFDM band efficiency of proposition are as follows:
L in formulaCPIndicate the length of the cyclic prefix of addition, G indicates the number of sub-frames of each ofdm signal.
10. a kind of OFDM peak-to-average power ratio based on two stages index modulation reduces system, which is characterized in that comprising such as lower die
Block:
Transmitting terminal serioparallel exchange and bit groupings module, for binary sequence to be sent to be passed through serioparallel exchange, serial
Bit data flow be converted into parallel data stream, wherein every p bit is one group of subframe for being input to a frame ofdm signal, this
In a frame include N number of subcarrier ofdm signal be divided into G=N/n subframe, Gg=[Xg,1 Xg,2 … Xg,n] indicate g-th
Subframe, 1≤g≤G, n are the subcarrier number that each subframe includes, and X indicates the subcarrier in a frame ofdm signal；
First stage selector module, for according to the preceding p in every group of p bit1Every height of a bit selection ofdm signal
Sub-carrier activation pattern in frame；
Mapper A module, for passing through A mapper for the p in every group of p bit2A bit map is to the signaling point in planisphere A；
Second stage selector module, for according to the p in every group of p bit3A bit does not swash from first stage each subframe
The active style of subcarrier is selected in subcarrier living again；
Mapper B module, for passing through B mapper for the p in every group of p bit4A bit map to the signaling point in planisphere B,
Signaling point in planisphere B mutually disjoints with the signaling point in planisphere A；
Frequency domain ofdm signal maker module, activation for being elected according to first stage index and second stage index carry
Wave is mapped to signal on the activation subcarrier of ofdm signal by mapper A and mapper B respectively；
N point IDFT module, for the frequency domain ofdm signal obtained by two stages index modulation to be transformed by IDFT module
Time domain；
Peak-to-average power ratio comparator module, for making ofdm signal by searching algorithm Choose for user device B mapped signaling point
PAPR minimize；
Transmitting terminal parallel-serial conversion plus cyclic prefix, digital-to-analogue conversion and up-converter module, the time domain OFDM for being generated to transmitting terminal
Signal carries out parallel-serial conversion, addition cyclic prefix, digital signal to analog signal conversion and upconversion process；
Receiving end down coversion, removes cyclic prefix and serioparallel exchange module at analog-to-digital conversion, for the time domain OFDM signal received
Carry out down coversion, analog signal to digital signal is converted, removal cyclic prefix and serioparallel exchange are handled；
N point DFT block, for the time domain OFDM signal received to be transformed into frequency domain；
Maximum Likelihood Detection, solution index and De-mapping module, for comprehensively considering every frame ofdm signal using Maximum Likelihood Detection
The signal of all possible sub-carrier activation pattern and mapping in subframe searches for all possible situation to detect subcarrier and swash
Pattern living and each activation subcarrier mapped signal, then binary message is restored by solution index and demapping processing；
Receiving end parallel serial conversion module, binary message for that will restore carry out parallel-serial conversion, restore originally transmitted two into
Sequence processed.
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