CN103812613A - Iterative detection device of low density parity code spread spectrum continuous phase modulation system - Google Patents
Iterative detection device of low density parity code spread spectrum continuous phase modulation system Download PDFInfo
- Publication number
- CN103812613A CN103812613A CN201410061828.8A CN201410061828A CN103812613A CN 103812613 A CN103812613 A CN 103812613A CN 201410061828 A CN201410061828 A CN 201410061828A CN 103812613 A CN103812613 A CN 103812613A
- Authority
- CN
- China
- Prior art keywords
- cpm
- spread spectrum
- module
- soft
- bit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Landscapes
- Error Detection And Correction (AREA)
- Detection And Prevention Of Errors In Transmission (AREA)
Abstract
The invention belongs to the field of signal detection, in particular to an iterative detection device of a low density parity code spread spectrum continuous phase modulation system for a low density parity code continuous phase modulation system based on spread spectrum. The iterative detection device of the low density parity code spread spectrum continuous phase modulation system comprises a receiving antenna, a CPM (Critical Path Method) demodulator, a CPM soft input and soft output module, a despreading mapper, a random interleaver, a weighting processing module, an LDPC (Low Density Parity Code) soft input soft output module, a derandom interleaver, a spreading mapper, an auxiliary hard decision module, a switching circuit and a bit decision device. The iterative detection device of the low density parity code spread spectrum continuous phase modulation system introduces a spread spectrum technology into an LDPC-CPM system to further improve the reliability and capacity of resisting disturbance of the system, effectively improves the performance of the system based on spread spectrum, and introduces the auxiliary hard decision module so as to enable the iteration process to timely stop after less iterative times and reduce the average number of iterations to further improve the real-time performance of the system.
Description
Technical field
The invention belongs to input field, be specifically related to a kind of low-density checksum (Low Density Parity Check Code based on spread spectrum, LDPC) the iterative detection device of the low density parity check code spread spectrum continuous phase modulation system of code Continuous Phase Modulation (Continuous Phase Modulation, CPM) system.
Background technology
Reliability and validity are two principal elements that communication system must be considered, wireless communication system must be considered spectrum efficiency and power efficiency, adopts advanced coding techniques and efficient modulation technique to combine and can make power utilization and the availability of frequency spectrum reach good balance point.The conventional method of traditional communication code and the separate design of modulation has critical defect: the chnnel coding take increase redundancy as main design idea is with the improve of error-correcting performance, and redundancy increases considerably, and has reduced effective information transmission rate.
Irregular low-density checksum (Low-Density Parity-Check, LDPC) code is the chnnel coding that approaches Shannon limit most found so far, is better than optimum Turbo code, and performance is apart from only poor 0.0045dB of Shannon limit.The LDPC(QC-LDPC of irregular quasi-cyclic) code, its check matrix has accurate circulation and lower triangular structure simultaneously, has overcome the high shortcoming of random LDPC code complexity.Continuous Phase Modulation (Continuous Phase Modulation, CPM) be the modulation technique of a class constant-envelope, there is efficient frequency band and power utilization, be particularly suitable for using the satellite communication system of nonlinear power amplifier, be considered to main candidate's modulation scheme of Future Multimedia satellite communication.LDPC-CPM combined coding modulation system can make system between the availability of frequency spectrum and power utilization, reach a best binding site.
The decoding concept of Turbo is rapidly developed at wireless communication field in recent years, the real breakthrough discovery of Turbo is not its coding form, but based on soft inputting and soft output SISO(Soft Input Soft Output) the iterative decoding method of component code decoding algorithm.Along with developing rapidly of telecommunications, the foundation of various types of communication net, make limited frequency resource more crowded, interference is each other even more serious, spread spectrum communication system has very strong interference free performance, its multiple access ability, maintain secrecy, also extremely people's the concern of function such as anti-multipath, be widely used in military communication and commercial communication.If apply the thought of Turbo iterative detection in spread spectrum system, can obviously improve reliability and the interference free performance of system.
In " a kind of Turbo cdma system of the CPM of application band spectrum modulation " that " electronic letters, vol " delivered, in this system, avoid demodulation in traditional Receiver Design, decoding to design separately the shortcoming of drop-out amount, this system can further improve the reliability of system, but aspect how despread-and-demodulation device mechanism is realized, do not having detailed explanation, and the real-time of system is poor.A literary composition has proposed employing CPM demodulator and LDPC decoding adopts Joint iteration detection technique in " based on the design of Turbo iterative algorithm LDPCC-CPM system receiver " that " Shenzhen University's journal " delivered, make CPM demodulator and ldpc decoder form a soft inputting and soft output module, can effectively improve the reliability of system, but this kind of not research aspect interference free performance of system.If LDPC-CPM system applies, in spread spectrum communication system, and is applied to the thought of Turbo iterative detection in system, in significantly promoting reliability and anti-interference, can there is the good availability of frequency spectrum like this.
The present invention encodes LDPC with CPM modulated applications in spread spectrum system, adopts Turbo iteration mechanism by organic to demodulation, despreading and decoding combination, and in system, adopts dynamic stopping criterion to reduce mean iterative number of time, improves the real-time of system.
Summary of the invention
The present invention proposes a kind of reliability and antijamming capability that can improve system, and can reduce mean iterative number of time, improves the iterative detection device of a kind of parity check code spread spectrum continuous phase modulation system of the real-time of system.
The object of the invention is to be achieved through the following technical solutions:
A kind of iterative detection device of parity check code spread spectrum continuous phase modulation system, comprise reception antenna, CPM demodulator, CPM soft inputting and soft output module, despreading mapper, separate random interleaver, weighting processing module, LDPC code soft inputting and soft output module, random interleaver, spread spectrum mapper, auxiliary hard decision module, switching circuit and bit decision device, reception antenna receives the CPM modulation signal that polluted by Gaussian channel, delivered to CPM demodulator and carried out demodulation, CPM demodulator output inner code word deliver to CPM soft inputting and soft output module and as an input by bit priori probability information sequence, CPM soft inputting and soft output module simultaneously by the outer code word of LDPC code soft inputting and soft output module output by bit probabilities information sequence through weighting processing module, after random interleaver and spread spectrum mapper as another input, internal information word after the output of CPM soft inputting and soft output module is upgraded is by bit probabilities information sequence, internal information word passes through despreading mapper in turn by bit probabilities information sequence, separate after random interleaver and weighting processing module and to deliver to LDPC code soft inputting and soft output module as outer code word by bit priori probability information sequence, the external information word of LDPC code soft inputting and soft output module output is delivered to auxiliary hard decision module by bit probabilities information sequence, auxiliary hard decision module is from iteration for the second time, the hard decision by bit rate probabilistic information sequence to adjacent twice iteration China and foreign countries information word compares, if the one n time consistent with the hard decision of the n-1 time, stop iterative detection overall process trigger switch circuit, the external information word of the n time iteration is delivered to bit decision device by bit probabilities information sequence simultaneously and carry out hard decision output.
Beneficial effect of the present invention is:
1. spread spectrum is incorporated in LDPC-CPM system, can further improves reliability and the antijamming capability of this system;
2. introduce spread spectrum/despreading mapper and can set up the iterative detection mechanism based on external information exchange, effectively improve the performance of the LDPC-CPM system based on spread spectrum;
3. introduce auxiliary hard decision module and can make iterative process stop in time under less iterations, reduce mean iterative number of time, improve the real-time of system.
Accompanying drawing explanation
Fig. 1 is and the corresponding transmitter principle figure of the present invention;
Fig. 2 is and the corresponding LDPC-CPM spread spectrum of the present invention iterative detection mechanism block diagram;
Fig. 3 has spread spectrum and the LDPC-CPM iteration system BER comparison without spread spectrum, and iterations is the 8th time.
Embodiment
Below in conjunction with accompanying drawing and example, the invention will be further described:
The transmitter corresponding with the present invention is made up of LDPC encoder (1), random interleaver (2), direct sequence spread spectrum (3), CPM modulator (4), transmitting antenna (7), as shown in Figure 1.Information sequence is input to CPM modulator (4) after LDPC encoder (1), random interleaver (2), direct sequence spread spectrum (3), wherein, CPM modulator (4) is decomposed into continuous phase encoder (Continuous Phase Encoder, CPE) (5) and memoryless modulator MM(Memoryless Modulator, MM) (6).CPE(5) input message is carried out after continuous phase coding as MM(6) input, MM(6) select a suitable waveform to be sent to Gaussian channel by antenna (7).The principal character of this transmitter is as follows:
1.LDPC encoder (1) adopts QC-LDPC(Quasi-cyclic LDPC) code, its check matrix adopts lower triangular structure, and coding adopts iteration encryption algorithm;
2. random interleaver (2) adopts pseudo random interleaving pattern;
3. in direct sequence spread spectrum (3), adopt the walsh code that spreading code word length is 16.
4.CPM modulator (4) adopts binary system, and modulation index h is 1/2, and base band pulse waveform g (t) adopts rectangular pulse shaping function (REC), and its memory span L is 1 code-element period, and now CPM is minimum shift keying (MSK).
The present invention is made up of reception antenna (8), CPM demodulator (9), CPM soft inputting and soft output module (CPM-SISO) (10), despreading mapper (11), solution random interleaver (12), weighting processing module (13), LDPC code soft inputting and soft output module (LDPC-SISO) (14), random interleaver (2), spread spectrum mapper (15), auxiliary hard decision module (16), switching circuit (17) and bit decision device (18), as shown in Figure 2.
Reception antenna (8) receives the CPM modulation signal that polluted by Gaussian channel, and delivered to CPM demodulator (9) and carried out demodulation, demodulator (9) output inner code word deliver to CPM-SISO module (10) and as one of them input by bit priori probability information sequence, module (10) simultaneously by the outer code word of LDPC-SISO module (14) output by bit probabilities information sequence through weighting processing module (13), after random interleaver (2) and spread spectrum mapper (15) as its another input, internal information word after module (10) output is upgraded is by bit probabilities information sequence, this sequence is through despreading mapper (11), after separating random interleaver (12) and weighting processing module (13), deliver to LDPC-SISO module (14) as outer code word by bit priori probability information sequence, the external information word of this module output is delivered to auxiliary hard decision module (16) by bit probabilities information sequence, this module is from iteration for the second time, the hard decision by bit rate probabilistic information sequence to adjacent twice iteration China and foreign countries information word compares, if the one n time consistent with the hard decision of the n-1 time, stop iterative detection overall process trigger switch circuit (17), the external information word of this iteration is delivered to bit decision device (18) by bit probabilities information sequence simultaneously and carry out hard decision output.
The principal character of this checkout gear is as follows:
First the spread spectrum internal information word of 1.CPM-SISO module (10) output delivers to despreading mapper (11) by bit probabilities information sequence, the despreading internal information word of despreading mapper (11) output is delivered to LDPC-SISO module (14) by bit probabilities information sequence through separating random interleaver (12) and weighting processing module (13), as the outer code word of inputting by bit probabilities information sequence.The outer code word of LDPC-SISO module (14) output is delivered to CPM-SISO module (10) by bit probabilities information sequence through weighting processing module (13), random interleaver (2) and spread spectrum mapper (15), as the internal information word of inputting by bit probabilities information sequence.
2. from iterative detection for the second time, the external information word of LDPC-SISO module (14) output is delivered to auxiliary hard decision module (16) by bit probabilities information sequence, this module compares the hard decision by bit rate probabilistic information sequence of adjacent twice iteration China and foreign countries information word, if the one n time consistent with the hard decision of the n-1 time, stop iterative detection overall process and carry out Hard decision decoding; If the hard decision of the n time and the n-1 time is inconsistent, carry out next iteration detection.
Fig. 1 is the transmitter principle figure corresponding with the present invention, is made up of continuous phase encoder (5) and memoryless modulator (6) CPM modulator (4).Each symbol in Fig. 1 is defined as follows:
U
o: information sequence to be sent;
C
o: the codeword sequence that LDPC encoder 1 is exported;
A
o: spread spectrum codeword sequence;
U
i: the output sequence after spread spectrum;
X
n: the output sequence of continuous phase encoder CPE5;
C
i: the output sequence of memoryless modulator 6.
Fig. 2 be the present invention in Gaussian channel an embodiment, based on receiver of the present invention by reception antenna (8), CPM demodulator (9), CPM soft inputting and soft output module (CPM-SISO) (10), despreading mapper (11), separate random interleaver (12), weighting processing module (13), LDPC code soft inputting and soft output module (LDPC-SISO) (14), random interleaver (2), spread spectrum mapper (15), auxiliary hard decision module (16), switching circuit (17) and bit decision device (18) formation.From typically the iterative receiver based on external information exchange is different, the present invention introduces and application despreading mapper (11), spread spectrum mapper (15) and auxiliary hard decision module (16).Each symbol in Fig. 2 is defined as follows:
R (t): the CPM modulation signal that polluted by Gaussian channel receiving on reception antenna (8);
P
i(C
i; In): CPM demodulator (9) output inner code word by bit priori probability information sequence;
P
i(U
i; In): the output sequence of LDPC-SISO module (14) after weighting processing module (13), random interleaver (2), spread spectrum mapper (15);
P
i(U
i; Out): the internal information word after CPM-SISO module (10) output is upgraded is by bit probabilities information sequence;
P
i(C
i; Out): the inner code word after CPM-SISO module (10) output is upgraded, by bit probabilities information sequence, is not used in iterative process;
P
o(C
o; In): the outer code word of input of LDPC-SISO module (14) is by bit priori probability information sequence;
P
o(U
o; In): the input external information word of LDPC-SISO module (14) is by bit priori probability information sequence, and this sequence meets even probability distribution feature;
P
o(C
o; Out): the outer code word after LDPC-SISO module (14) output is upgraded is by bit probabilities information sequence;
P
o(U
o; Out): the external information word after LDPC-SISO module (14) output is upgraded is by bit probabilities information sequence;
D: the output sequence of bit decision device.
Suppose that information sequence length to be sent is N, the code check of LDPC code is R
d, the length of spread spectrum code word is L
c, the output sequence L after LDPC encoder and direct sequence spread spectrum
sp=(N × L
c)/R
d.At receiving terminal, the spread spectrum internal information word of CPM-SISO module (10) output is by bit probabilities sequence P
i(U
i; In), suppose that the probability sequence that in this sequence, all bits are " 1 " is
the probability sequence that in this sequence, all bits are " 1 " is
by sequence P
i(U
i; In) deliver to despreading mapper (11) and complete corresponding despreading and probability mapping.
Suppose information sequence U
ofor { U
1, U
2... U
i..., U
n, wherein U
i∈ [0,1], the output codons sequence after LDPC encoder (1) is C
o,
wherein C
i∈ [1,1].Frequency expansion sequence
if when random interleaver (2) output bit is " 1 ", the codeword sequence after spread spectrum
if when random interleaver (2) output bit is " 1 ", the codeword sequence after spread spectrum
Definition
The signal processing of despreading mapper (11) is as follows:
The object of separating expanding map is to be L by length
spp
i(U
i; In) to be reduced to length be N/R to sequence mapping
dcode word probability sequence
wherein Q
ifor the definition of probability of bit " 1 " is
in like manner Q
ifor the definition of probability of bit " 1 " is
for the inner code word by CPM-SISO module (10) output is by bit probabilities information sequence ((i-1) × L
sP+ m) individual be E
1 mcode word probability.In like manner,
for the inner code word by CPM-SISO module (10) output is by bit probabilities information sequence ((i-1) × L
sP+ m) be individually
code word probability.Q
ifor the normalization probability of bit " 1 " is
?
In like manner, Q
ifor the normalization probability of bit " 1 " is
?
Separate the inner code word input as weighting processing module (13) through solution random interleaver (12) by bit probabilities information sequence after expanding map, in module (13), getting α and β is weight coefficient, α=0.8 in this module, β=0.01.Suppose { the P that is input as of this module
in(x
i), i=1,2..., N/R
d, the output { P of this module
out(y
i), i=1,2..., N/R
dmeet equation (3),
P
out(y
i)=exp ((α * log
ep
in(x
i)) .*exp (β * log
ep
in(x
i))) equation (3)
Wherein .* represents point multiplication operation.
The outer code word of LDPC-SISO module (14) output is by bit probabilities information sequence through weighting processing module (13) and random interleaver (2), and the probability sequence of random interleaver (2) output is
wherein W
ifor the definition of probability of bit " 1 " is W
i 1, W
ifor the definition of probability of bit " 1 " is
The signal processing of spread spectrum mapper (15) is as follows:
Definition
for the output probability sequence of spread spectrum mapper (15),
be defined as output ((the k-1) × L of spread spectrum mapper (15)
c+ m) individual code word is
probability, represent that the k of spread spectrum mapper (15) is input as the spread spectrum mapping probability sequence of the code word of bit " 1 ", in like manner,
be defined as output ((the k-1) × L of spread spectrum mapper (15)
c+ m) individual code word is
probability, represent that the k of spread spectrum mapper (15) is input as the spread spectrum mapping probability sequence of the code word of bit " 1 ".?
Fig. 3 has spread spectrum and the LDPC-CPM iteration system BER comparison (iterations is the 8th time) without spread spectrum, and choosing check matrix dimension is 768 × 1536, the QC-LDPC code of code check 1/2, and degree is distributed as λ (x)=0.2308x+0.4615x
2+ 0.3077x
7.As can be seen from Figure 3, there is the LDPC-CPM iteration system of spread spectrum can increase substantially without the LDPC-CPM iteration system reliability of spread spectrum.
Claims (1)
1. the iterative detection device of a parity check code spread spectrum continuous phase modulation system, comprise reception antenna, CPM demodulator, CPM soft inputting and soft output module, despreading mapper, separate random interleaver, weighting processing module, LDPC code soft inputting and soft output module, random interleaver, spread spectrum mapper, auxiliary hard decision module, switching circuit and bit decision device, it is characterized in that: reception antenna receives the CPM modulation signal that polluted by Gaussian channel, delivered to CPM demodulator and carried out demodulation, CPM demodulator output inner code word deliver to CPM soft inputting and soft output module and as an input by bit priori probability information sequence, CPM soft inputting and soft output module simultaneously by the outer code word of LDPC code soft inputting and soft output module output by bit probabilities information sequence through weighting processing module, after random interleaver and spread spectrum mapper as another input, internal information word after the output of CPM soft inputting and soft output module is upgraded is by bit probabilities information sequence, internal information word passes through despreading mapper in turn by bit probabilities information sequence, separate after random interleaver and weighting processing module and to deliver to LDPC code soft inputting and soft output module as outer code word by bit priori probability information sequence, the external information word of LDPC code soft inputting and soft output module output is delivered to auxiliary hard decision module by bit probabilities information sequence, auxiliary hard decision module is from iteration for the second time, the hard decision by bit rate probabilistic information sequence to adjacent twice iteration China and foreign countries information word compares, if the one n time consistent with the hard decision of the n-1 time, stop iterative detection overall process trigger switch circuit, the external information word of the n time iteration is delivered to bit decision device by bit probabilities information sequence simultaneously and carry out hard decision output.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410061828.8A CN103812613B (en) | 2014-02-24 | 2014-02-24 | A kind of parity check code spreads the iterative detection device of continuous phase modulation system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410061828.8A CN103812613B (en) | 2014-02-24 | 2014-02-24 | A kind of parity check code spreads the iterative detection device of continuous phase modulation system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN103812613A true CN103812613A (en) | 2014-05-21 |
| CN103812613B CN103812613B (en) | 2017-07-11 |
Family
ID=50708868
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201410061828.8A Active CN103812613B (en) | 2014-02-24 | 2014-02-24 | A kind of parity check code spreads the iterative detection device of continuous phase modulation system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN103812613B (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20100284444A1 (en) * | 2009-05-06 | 2010-11-11 | Ismail Lakkis | Method and apparatus for packet acquisition |
| CN102710367A (en) * | 2012-04-16 | 2012-10-03 | 哈尔滨工程大学 | Adaptive iterative receiver in low-density parity check code and continuous phase modulation system |
| CN103490845A (en) * | 2013-09-16 | 2014-01-01 | 哈尔滨工程大学 | Improved Logistic-Map chaos spreading sequence generation device and method based on weighting |
-
2014
- 2014-02-24 CN CN201410061828.8A patent/CN103812613B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20100284444A1 (en) * | 2009-05-06 | 2010-11-11 | Ismail Lakkis | Method and apparatus for packet acquisition |
| CN102710367A (en) * | 2012-04-16 | 2012-10-03 | 哈尔滨工程大学 | Adaptive iterative receiver in low-density parity check code and continuous phase modulation system |
| CN103490845A (en) * | 2013-09-16 | 2014-01-01 | 哈尔滨工程大学 | Improved Logistic-Map chaos spreading sequence generation device and method based on weighting |
Also Published As
| Publication number | Publication date |
|---|---|
| CN103812613B (en) | 2017-07-11 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP3217662B1 (en) | Rate matching method and apparatus for polar code, and wireless communication device | |
| KR20190116816A (en) | Apparatus and method for encoding and decoding unsing polar code in wireless communication system | |
| CN106209302B (en) | Data transmission processing method and device | |
| Hong et al. | Performance analysis and optimisation for edge connection of JSCC system based on double protograph LDPC codes | |
| Hoeher et al. | Interleave-division multiple access from a multiuser theory point of view | |
| Roth et al. | A comparison of physical layers for low power wide area networks | |
| Guo et al. | Jointly optimized design of distributed Reed–Solomon codes by proper selection in relay | |
| Pan et al. | Joint iterative detection and decoding receiver for polar coded SCMA system | |
| Bao et al. | Design of efficient joint eIRA-coded MSK modulation systems for space communications | |
| Ejaz et al. | Multi-level construction of polar codes for half-duplex wireless coded-cooperative networks | |
| CN101753261B (en) | Coder, decoder and coding and decoding methods | |
| Jin et al. | Cascading polar coding and LT coding for radar and sonar networks | |
| CN107612559B (en) | Generation method based on the duplicate polynary polarization code of multiplying property | |
| CN101753153A (en) | Turbo code encoder, decoder, encoding method and decoding method | |
| CN103812613A (en) | Iterative detection device of low density parity code spread spectrum continuous phase modulation system | |
| Abidi et al. | Performances analysis of polar codes decoding algorithms over polar-coded scma system | |
| Che et al. | Low-complexity LDPC coded BICM-ID with orthogonal modulations | |
| Yi | Improving security of 5G networks with multiplicative masking method for LDPC codes | |
| Paolini et al. | Improved low-density parity-check codes for burst erasure channels | |
| Farhan et al. | Enhancement of code division multiple access system performance using raptor codes | |
| Qiu et al. | Irregular repeat-accumulate lattice network codes for two-way relay channels | |
| Abidi et al. | A novel detection and decoding receiver for Polar-Coded SCMA system | |
| Rajagopal et al. | Design of SPA decoder for CDMA applications | |
| Dizdar et al. | An uplink non-orthogonal multiple access method based on frozen bit patterns of polar codes | |
| Mosleh et al. | Reduce the Resources Utilization of LDPC Decoder Based on Min-Sum Decoder for Spread Spectrum Applications |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |