CN102624665B - Method for reducing peak to average power ratio (PAPR) of multi-carrier communication signals - Google Patents
Method for reducing peak to average power ratio (PAPR) of multi-carrier communication signals Download PDFInfo
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Abstract
A method for reducing a peak to average power ratio (PAPR) of multi-carrier communication signals belongs to the technical field of communication utilizing the multi-carrier communication signals and particularly relates to wireless multi-carrier communication which is combined with a low density parity check (LDPC) code to reduce the PAPR of the multi-carrier communication signals. The method includes firstly, proposing an LDPC code of a special structure and a reversible subset LDPC (NS-LDPC) code; then proposing a method to subject a reversible subset of the NS-LDPC code to reverse operating so that the PAPR of the multi-carrier communication signals can be effectively reduced. According to the method for reducing the PAPR of the multi-carrier communication signals, the PAPR of the multi-carrier communication signals can be effectively reduced, and bit error ratio performance and a data transfer rate of a system can hardly be affected.
Description
Technical field
The invention belongs to communication technical field, relate in particular to wireless multi-carrier communications, as wireless OFDM (OFDM) communication, be specifically related to a kind of method that reduces multi-carrier communications signals PAPR, the method is by being used the subset LDPC that can reverse, be NS-LDPC code, realize the function of its reduction multi-carrier communications signals PAPR.
Background technology
Multi-carrier communication technology, especially OFDM (OFDM) communication technology has been widely used in radio communication.A remarkable shortcoming of multi-carrier communication is that multi-carrier communications signals has higher peak value and average power ratio, is called for short peak-to-average power ratio (PAPR).Higher PAPR requires the modules such as communication system intermediate power amplifier, digital to analog converter to have larger linear dynamic range, otherwise can cause inband signaling distortion and out of band spectrum to be revealed, and causes ofdm system performance to decline to a great extent.At present, the method for reduction multi-carrier communications signals PAPR mainly comprises:
(1) cut ripple method (Clipping and Filtering), see L.Wang and C.Tellambura, " A simplified clipping and filtering technique for PAR reduction in OFDM systems; " IEEE Signal Processing Letters, vol.12, no.6, pp.453-456, Jun.2005, cut the peak signal that first ripple method exceed predetermined threshold value to amplitude in ofdm signal and shear, then by filter filtering out-of-band radiation.The method can directly effectively reduce the PAPR of ofdm signal, but cut the inband distortion that ripple method causes, cannot eliminate, and this can cause error rate of system to increase.
(2) partial transmission sequence (Partial Transmit Sequence), see L.J.Cimini, Jr.and N.R.Sollenberger, " Peak-to-average power ratio reduction of an OFDM signal using partial transmit sequences, " IEEE Communications Letters, vol.4, no.3, pp.86-88, Mar.2000, the basic thought of partial transmission sequence method is that process is encoded, data block after mapping becomes several disjoint sub-blocks according to certain regular partition, then each sub-block is multiplied by suitable phase rotation coefficient and reduces PAPR.It is remarkable that the method reduces PAPR effect; and signal is not produced to distortion; but receiving terminal only could correctly recover data when known phase information; in order to guarantee that receiving terminal can obtain correct phase information; need increase extra bit to phase information protects; and then sending to receiving terminal as side information, this can cause system data transfer rate to reduce.
(3) coding method (Coding scheme), see M.Sabbaghian, Y.Kwak, B.Smida, and V.Tarokh, " Near Shannon limit and low peak to average power ratio turbo block coded OFDM, " IEEE Trans, Commun., vol.59, no.8, pp.2042-2045, Aug.2011, the method is for the ofdm system that adopts Turbo block code (TBC) coding, specific implementation is that the frequency domain components code of Turbo block code adopts the Reed-Muller code with excellent PAPR performance, time domain component code adopts the low-density parity check code (LDPC) with excellent error-correcting performance, the method can obtain good error-correcting performance when reducing PAPR, but along with the increase of code length, PAPR reduces deleterious, and bit error rate performance with under similarity condition, adopt separately more than LDPC code carries out still losing 1dB compared with error correction.
In sum, the shortcoming of the method for current reduction multi-carrier communications signals PAPR comprises: error rate of system increases or system data transfer rate declines, and the present invention proposes for overcoming the above problems exactly.
Summary of the invention
For multi-carrier communications signals because high PAPR, thereby cause communication system intermediate power amplifier linear dynamic range to be had relatively high expectations or transmitted signal distortion, and the method for existing reduction multi-carrier communications signals PAPR exists degradation shortcoming under error rate of system increase or system data transfer rate, the present invention proposes a kind of method that reduces multi-carrier communications signals PAPR, the method can, the in the situation that of loss system performance (comprising error rate of system and system data transfer rate) hardly, significantly reduce multi-carrier signal PAPR.
A kind of method that reduces multi-carrier communications signals PAPR provided by the invention, it is characterized in that, the method utilizes NS-LDPC code to reduce multi-carrier communications signals PAPR, and NS-LDPC code is a kind of LDPC code with at least one subset of can reversing, and these can reverse between subset less than occuring simultaneously;
The described subset of reversing is defined as the set of some coded-bits of LDPC code, the set of corresponding variable node on the corresponding Tanner figure of this set, and meeting each check-node has even number of edges to be connected with each subset of reversing, and comprises that 0 limit connects; And having a bit in the coded-bit set of each subset of reversing is phase bits, phase bits is fixed as 0 when coding.
The NS-LDPC code that the present invention proposes is a kind of LDPC code with special construction, it has the individual subset of reversing of M (M >=1), and to any NS-LDPC code word, one or more all bits of can inverted rotor set pair answering reverse simultaneously, the new code word forming, remains a legal-code of this NS-LDPC code.Thereby for the multi-carrier communications systems that adopts NS-LDPC code, transmitting terminal, by the subset of can reversing is carried out to reverse turn operation independently, can change the code word transmission of selecting to have minimum PAPR in code word in 2M kind, can effectively reduce like this multi-carrier signal PAPR.On the one hand, NS-LDPC belongs to the one of LDPC code, and it has the error-correcting performance consistent with general LDPC code; On the other hand, can inverted rotor concentrate and remain with 1 bit and indicate corresponding reversed subset whether reversion has occurred as phase bits, by decoding, can recover this phase bits, and then recovery information bit, thereby do not need transmitted sideband information, can not cause because of transmitted sideband information that system data transfer rate declines.The method that the employing NS-LDPC code that the present invention proposes reduces multi-carrier communications signals PAPR can significantly reduce multi-carrier signal PAPR in the situation that of loss system performance hardly, can be applicable to adopt the various communication systems of multi-transceiver technology.
Accompanying drawing explanation
Fig. 1 is the Tanner figure of LDPC code;
Fig. 2 is the transmitter block diagram that application NS-LDPC code reduces multi-carrier signal PAPR;
Embodiment
In order to make object of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein, only in order to explain the present invention, is not intended to limit the present invention.
As shown in Figure 1, LDPC code can represent with Tanner figure, and in figure, the node of top is variable node, and corresponding coded-bit, comprises information bit and check bit, and the node of below is check-node, and the connection between variable node and check-node is called limit.
NS-LDPC code is a kind of LDPC code, but has the structure of following uniqueness:
(1) NS-LDPC has at least one subset of can reversing, and these can reverse between subset less than occuring simultaneously.The described subset of reversing is defined as the set (set of relevant variable node in corresponding Tanner figure) of some coded-bits of LDPC code, and meeting each check-node has even number of edges to be connected (comprising that 0 limit connects) with each subset of reversing.
(2) in the coded-bit set of each subset of reversing, having a bit is phase bits, and phase bits is fixed as 0 when coding.
Because each check-node has even number of edges to be connected with each subset of reversing in the Tanner figure of NS-LDPC code correspondence, NS-LDPC code has the character of following uniqueness: to any code word, one or more all bits of can inverted rotor set pair answering reverse simultaneously, the new code word forming, remains a legal-code of this NS-LDPC code.Described reversion refers to bit 0 is become to bit 1, or bit 1 is become to bit 0.
Because each, can inverted rotor concentrate that to have a bit be phase bits, and be fixed as 0 when coding, so phase bits can be used to indicate reversed subset corresponding in NS-LDPC code, whether reversion has occurred.If certain the reversed subset in NS-LDPC code has been carried out to reverse turn operation, its corresponding phase bits becomes 1; If certain the reversed subset in NS-LDPC code is not carried out to reverse turn operation, corresponding phase bits is still 0.The phase bits that can utilize decoding to obtain at receiving terminal judges whether the reversed subset of its correspondence reversion has occurred, thereby correctly recovers information bit.
As shown in Figure 2, the present invention proposes NS-LDPC to comprise following process for reducing the method for multi-carrier communications systems PAPR:
(1) NS-LDPC coding step:
According to predefined M value, structure has the Tanner figure of the NS-LDPC code correspondence of M the subset of can reversing, meeting each check-node has even number of edges to be connected with each subset of reversing, the Tanner figure obtaining according to structure, input information bits is encoded and obtained coded-bit set V, and wherein coded-bit set V comprises M the subset { V that can reverse
1, V
2..., V
mand 1 subset V that can not reverse
0, and each can inverted rotor concentrated phase bits all be fixed as 0 when coding, claims that code word is now original code word.Described M is for being more than or equal to 1, and is less than or equal to the positive integer of code length, and the effect of the larger reduction of M value PAPR is better, but implementation complexity also can correspondingly increase, and can set suitable M value according to actual demand.
(2) phase place initialization step:
Whether each subset of reversing is reversed and is referred to as phase place, and phase place is that 0 expression is nonreversible, and phase place is 1 expression reversion.Owing to comprising M the subset of can reversing in NS-LDPC code, therefore need M phase place.
When phase place initialization, first produce M phase place and be 0 phase combination, using this as current phase combination;
By changing the one or more phase values in phase combination, altogether can produce 2
mplant different phase combination.
(3) reverse turn operation step:
According to current phase combination, respectively each subset of reversing in NS-LDPC code is carried out to reverse turn operation independently, claim that through the code word of reverse turn operation be variation code word.Obviously, to binary system LDPC code, reverse turn operation is equivalent to and can the concentrated bit phase place corresponding with this subset of inverted rotor carries out XOR.The subset of can not reversing V
0in bit do not participate in reverse turn operation.
(4) multi-carrier modulation step:
Successively to the current variation code word obtaining interweave, sign map, multi-carrier modulation, obtained like this multi-carrier signal;
(5) calculate PAPR value the record of current phase combination multi-carrier signal.
(6) whether the sum of the phase combination that judgement has produced equals 2
m, if so, enter step (7), otherwise, change arbitrarily the one or more phase values in current phase combination, with form one with all not identical phase combination of all phase combination that produce, as new current phase combination, then go to step (3);
(7) relatively record 2
mplant the PAPR value of phase combination multi-carrier signal, select the phase combination of multi-carrier signal PAPR minimum is combined as optimum angle, and claim the lower corresponding variation code word of optimum angle combination for transmission code word.Send that code word is final through interweaving, after sign map, multi-carrier modulation to be sent through antenna.
Example:
Embodiment is a multicarrier system that has 1024 subcarriers, and wherein sign map mode adopts BPSK mapping mode, is about to bit 0 and is mapped as symbol+1, and bit 1 is mapped as to symbol-1.The each multicarrier symbol of this system can transmit 1024 coded-bits.The time-domain signal of each multicarrier symbol is obtained by the bpsk signal stack on these 1024 subcarriers, has very high PAPR.
In embodiment, transmitting terminal adopts a NS-LDPC code that code length is 1024, and obviously sending this yard of code word needs 1024 BPSK symbols.This code comprises M=3 subset: the V that can reverse
1, V
2and V
3, the phase bits node of their correspondences is designated as b
1, b
2and b
3.Each subset of reversing comprises 256 coded-bits.Outside the subset of can reversing, also have 256 bits, the subset of can not reversing, these bits are not participate in reverse turn operation.
(1) structure has the Tanner figure of the NS-LDPC code correspondence of 3 subsets of can reversing, and the Tanner obtaining according to structure figure, encodes and obtain coded-bit set V input information bits, and code length is 1024, and it comprises 3 subset: V that can reverse
1, V
2, V
3, and 1 subset V that can not reverse
0.Phase place initialization step:
(2) whether each subset of reversing is reversed and is referred to as phase place, and phase place is that 0 expression is nonreversible, and phase place is 1 expression reversion.Owing to comprising 3 subsets of can reversing in NS-LDPC code in embodiment, therefore need 3 phase places.
When phase place initialization, first produce 3 phase places and be 0 phase combination, using this as current phase combination;
By changing the one or more phase values in phase combination, altogether can produce 2
3=8 kinds of different phase combination.
(3) the current phase combination of foundation is respectively to the subset V that can reverse in NS-LDPC code
1, V
2and V
3carry out independently reverse turn operation, claim that through the code word of reverse turn operation be variation code word.Obviously, to binary system LDPC code, reverse turn operation is equivalent to and can the concentrated bit phase place corresponding with this subset of inverted rotor carries out XOR.The subset of can not reversing V
0in bit do not participate in reverse turn operation.
(4) successively to the current variation code word obtaining interweave, sign map, multi-carrier modulation, obtained like this multi-carrier signal;
(5) calculate PAPR value the record of current phase combination multi-carrier signal.
(6) whether the sum of the phase combination that judgement has produced equals 8, if, enter step (7), otherwise, change arbitrarily the one or more phase values in current phase combination, with form one with all not identical phase combination of all phase combination that produce, as new current phase combination, then go to step (3);
(7) the PAPR value of 8 kinds of phase combination multi-carrier signals that relatively record, selects the phase combination of multi-carrier signal PAPR minimum is combined as optimum angle, and claims the lower corresponding variation code word of optimum angle combination for sending code word.Send that code word is final through interweaving, after sign map, multi-carrier modulation to be sent through antenna.
The above; only for preferably embodiment of the present invention, but protection scope of the present invention is not limited to this, is anyly familiar with in technical scope that those skilled in the art disclose in the present invention; the variation that can expect easily or replacement, within all should being encompassed in protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.
Claims (1)
1. one kind is reduced the method for multi-carrier communications signals PAPR, it is characterized in that, the method utilizes NS-LDPC code to reduce multi-carrier communications signals PAPR, and NS-LDPC code is a kind of LDPC code with at least one subset of can reversing, and these can reverse between subset less than occuring simultaneously;
The described subset of reversing is defined as the set of some coded-bits of LDPC code, the set of corresponding variable node on the corresponding Tanner figure of this set, and meeting each check-node has even number of edges to be connected with each subset of reversing, and comprises that 0 limit connects; And having a bit in the coded-bit set of each subset of reversing is phase bits, phase bits is fixed as 0 when coding;
The method specifically comprises the steps:
(1) NS-LDPC coding step:
According to predefined M value, structure has the Tanner figure of the NS-LDPC code correspondence of M the subset of can reversing, meeting each check-node has even number of edges to be connected with each subset of reversing, the Tanner figure obtaining according to structure, input information bits is encoded and obtained coded-bit set V, and wherein coded-bit set V comprises M the subset { V that can reverse
1, V
2..., V
mand 1 subset V that can not reverse
0, and each can inverted rotor concentrated phase bits all be fixed as 0 when coding, claims that code word is now original code word; Described M is for being more than or equal to 1, and is less than or equal to the positive integer of code length;
(2) phase place initialization step:
Whether each subset of reversing is reversed and is referred to as phase place, and phase place is that 0 expression is nonreversible, and phase place is 1 expression reversion; When phase place initialization, first produce M phase place and be 0 phase combination, using this as current phase combination;
(3) reverse turn operation step:
According to current phase combination, respectively each subset of reversing in NS-LDPC code is carried out to reverse turn operation independently, claim that through the code word of reverse turn operation be variation code word;
(4) multi-carrier modulation step:
Successively to the current variation code word obtaining interweave, sign map, multi-carrier modulation, obtain a multi-carrier signal;
(5) calculate PAPR value the record of current phase combination multi-carrier signal;
(6) whether the sum of the phase combination that judgement has produced equals 2
m, if so, enter step (7), otherwise, change arbitrarily the one or more phase values in current phase combination, with form one with all not identical phase combination of all phase combination that produce, as new current phase combination, then go to step (3);
(7) relatively record 2
mplant the PAPR value of phase combination multi-carrier signal, select the phase combination of multi-carrier signal PAPR minimum is combined as optimum angle, and claim the lower corresponding variation code word of optimum angle combination for transmission code word; Send that code word is final through interweaving, after sign map, multi-carrier modulation to be sent through antenna.
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| CN105743835B (en) * | 2016-04-18 | 2018-12-07 | 华中科技大学 | A method of reducing OFDMA system signal peak-to-average power power ratio |
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| CN102238129A (en) * | 2011-08-02 | 2011-11-09 | 韩山师范学院 | Signal modulation and demodulation method capable of reducing peak to average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signal |
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| CN102238129A (en) * | 2011-08-02 | 2011-11-09 | 韩山师范学院 | Signal modulation and demodulation method capable of reducing peak to average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signal |
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