CN103259758A - OFDM communication system and method based on companding - Google Patents

OFDM communication system and method based on companding Download PDF

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CN103259758A
CN103259758A CN2013102003917A CN201310200391A CN103259758A CN 103259758 A CN103259758 A CN 103259758A CN 2013102003917 A CN2013102003917 A CN 2013102003917A CN 201310200391 A CN201310200391 A CN 201310200391A CN 103259758 A CN103259758 A CN 103259758A
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time
transform
ofdm
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CN103259758B (en
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王毅
汪千栋
陈前斌
杨运春
甄珊
刘超
唐瀚
王香瑜
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Chongqing University of Post and Telecommunications
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Abstract

The invention provides an OFDM communication system and method based on companding. A bit stream input into a transmitting device forms OFDM signals after base band mapping and IFFT, and after companding and transformation are carried out on the OFDM signals, parallel-serial conversion is carried out on the OFDM signals and then the OFDM signals enter a power amplifier, and the amplified signals are mapped to a transmitting unit to be transmitted; a receiving device carries out serial-parallel conversion on received time-domain signals, the first time of FFT is carried out on the time-domain signals, the time-domain signals is transformed into frequency domain signals, channel information is obtained through channel estimation, channel equalization is carried out on the received frequency domain signals, the equalized signals are converted into a time domain through the IFFT, expanding transformation is carried out on the equalized signals, then the equalized signals are sent to an FFT module for demodulation and decoding, and finally the needed bit stream is obtained through the base band mapping. The OFDM communication system based on the companding can effectively solve the problem that constellation diagrams of a traditional companding OFDM communication system are scattered in a multipath channel, can effectively reduce an EVM value, and lowers the error rate.

Description

A kind of ofdm communication system and method based on the compression expansion
Technical field
The present invention relates to communication technical field, relate in particular to a kind of OFDM(orthogonal frequency division multiplexed) communication system and the method for technology.
Background technology
The appearance of OFDM (OFDM) technology has well solved the frequency selective fading of wireless channel, thinks one of core technology of the 4th third-generation mobile communication 4G.One of topmost shortcoming of ofdm system is to have bigger peak-to-average force ratio (PAPR), and it directly affects operating cost and the efficient of whole system.When the dynamic range that exceeds power amplifier when signal can not be put into by linearity, will cause serious distorted signals, destroy the orthogonality between each subcarrier. cause inband signaling distortion and out of band spectrum disperse.
At present. the method that many kinds reduce the ofdm signal peak-to-average force ratio has been proposed. comprise amplitude limit (clipping) method, partial transmission sequence (PTS) method, select mapping (SLM) method, (Interleaving) method that interweaves, coding (coding) method, companding (companding) method, expanding constellation space (ActiveConstellation) method etc.These methods are all with different costs, for the peak-to-average force ratio that reduces ofdm signal provides effective solution.For example, PTS method and SLM method can increase system complexity, produce redundant information; Margining amplitude technique and companding method can cause the frequency spectrum distortion; Compiling method has reduced the rate of information throughput etc.
Be illustrated in figure 1 as the structural representation of existing ofdm communication system.In the existing ofdm communication system structure, the receiving end signal flow process is: receive signal and at first carry out transform expansion, then transform to frequency domain by the FFT module.Such method obtains preferable performance under additive white Gaussian noise channel.But under multipath channel, because the signal that receives is the time-delay stack that sends each footpath of signal, traditional transform expansion algorithm will cause the serious distortion of signal, reduce the whole system receptivity.The present invention proposes new signal flow and processing method to solve the planisphere diffusion problem that companding method causes under the multipath channel environment.
Summary of the invention
The present invention is directed to the above-mentioned defective of prior art, propose a kind of ofdm communication system and method, compress the planisphere diffusion problem under the multipath channel environment that extended method causes in order to solve existing ofdm communication system,
The technical scheme that the present invention solves the problems of the technologies described above is, a kind of ofdm communication system based on the compression expansion is proposed, it is characterized in that, comprise: wired or wireless communication channel, dispensing device and receiving system, described dispensing device comprises the compressed transform module that suppresses the ofdm signal peak-to-average force ratio, the compressed transform module carries out sending to receiving system by the wired or wireless communication channel behind the compressed transform to signal, and receiving system restores the transmitting terminal ofdm signal according to the compressed signal that receives.
Described receiving system comprises for the first time FFT unit, channel equalization unit, IFFT unit, transform expansion unit, FFT unit for the second time, parallel serial conversion unit and decoding unit; The FFT unit carries out FFT conversion acquisition first time frequency-region signal to the compressed signal that receives for the first time, and the channel equalization that channel equalization unit is done on the frequency domain this frequency-region signal is sent into the IFFT unit; The signal of IFFT unit after to channel equalization carries out the IFFT treatment conversion to time domain, the transform expansion unit carries out transform expansion to the time-domain signal by the IFFT conversion and sends into FFT unit for the second time, with this time-domain signal through the second time FFT unit be transformed to frequency-region signal, send into parallel serial conversion unit, conversion is done and gone here and there to parallel serial conversion unit to logical this frequency-region signal, sends into decoding unit and decipher the acquisition ofdm signal.The compressed transform module is to the time domain sequences { x of ofdm signal in the dispensing device nCalculate, draw ofdm signal at the average amplitude v of time domain, determine companding coefficient μ, call formula:
Figure BDA00003251092700021
Ofdm signal is carried out compressed transform, and the signal that obtains behind the compressed transform is S (n), and wherein v is ofdm signal x nAverage amplitude.The transform expansion unit is to time-domain signal in the receiving system
Figure BDA00003251092700022
Carry out transform expansion, according to formula:
Figure BDA00003251092700023
Signal y (n) after the acquisition transform expansion, wherein, μ is the compressed coefficient, v is that ofdm signal is at the average amplitude of time domain.
The present invention also proposes a kind of ofdm communication method based on the compression expansion, dispensing device carries out compressed transform to signal and sends to receiving system by the wired or wireless communication channel, and receiving system receives the laggard line translation of compressed signal and handles the ofdm signal that restores transmitting terminal; Described receiving system carries out conversion process and comprises, in the receiving system for the first time the FFT unit compressed signal that receives carried out FFT conversion acquisition first time frequency-region signal send into channel equalization unit, channel equalization unit is done channel equalization on the frequency domain to this frequency-region signal; The IFFT unit will carry out IFFT by the signal after the channel equalization unit and be transformed into time domain, the transform expansion unit is to carrying out transform expansion by the time-domain signal behind the IFFT unit, the FFT conversion obtains second frequency-region signal to do for the second time by the signal after the transform expansion in the FFT unit for the second time, conversion is done and gone here and there to parallel serial conversion unit to second frequency-region signal, sends into decoding unit and decipher.
Ofdm communication system provided by the invention, carry out the FFT conversion to received signal at receiving terminal, after finishing the channel equalization on the frequency domain, signal after the channel equalization is converted to time-domain signal by IFFT fall transform expansion, signal after the transform expansion is sent into the FFT module, obtain final bit stream information finally by base band demodulating and decoding.Can effectively reduce because the compression expansion algorithm planisphere diffusion problem that multipath channel causes can reduce the error rate, improve system reliability.
The present invention also has the following advantages:
(a) do not change the transmitting terminal signal processing;
(b) receiving terminal preferentially carries out FFT conversion, equilibrium and IFFT conversion, has effectively eliminated the influence of multipath effect to signal;
(c) method of the present invention's proposition is unfixing for the mode of companding transform, therefore can adopt flexible and changeable companding algorithm to come signal is compressed and expands, and leads compression algorithm and not only be confined to traditional μ of the present invention;
Description of drawings
Fig. 1 is the structural representation of existing ofdm communication system;
The structural representation of the ofdm communication system that Fig. 2 provides for the embodiment of the invention.
Embodiment
The present invention proposes a kind of ofdm communication system based on the compression expansion, comprise: wired or wireless communication channel, dispensing device and receiving system, described dispensing device comprises the compressed transform module that suppresses the ofdm signal peak-to-average force ratio, and dispensing device sends signal to receiving system; Described receiving system restores the signal of transmitting terminal according to the signal that receives.
Described receiving system comprises for the first time FFT unit, channel equalization unit, IFFT unit, transform expansion unit, FFT unit for the second time, parallel serial conversion unit and decoding unit; For the first time FFT unit signal that receiving system is received carries out the FFT conversion first time, and channel equalization unit is to doing the channel equalization on the frequency domain by the frequency-region signal behind the first time FFT unit; Described IFFT unit is transformed into time domain to carrying out IFFT by the signal after the channel equalization unit; The transform expansion unit is handled carry out transform expansion by the signal behind the IFFT unit; The FFT unit is to doing FFT conversion for the second time by the signal behind the transform expansion unit for the second time; Described parallel serial conversion unit is to doing and go here and there conversion by the frequency-region signal behind the second time FFT unit; Described decoding unit is to deciphering by the signal behind the parallel serial conversion unit.
Below in conjunction with the accompanying drawing in the embodiment of the invention, the technical scheme in the embodiment of the invention is clearly and completely described, obviously, described embodiment only is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills belong to the scope of protection of the invention not making the every other embodiment that obtains under the creative work prerequisite.
The embodiment of the invention provides a kind of ofdm communication system based on the compression expansion, and Fig. 2 is the structural representation of this system, and this system can comprise: dispensing device 21, receiving system 22 and communication channel 23.Wherein, dispensing device 21 comprises: coding unit 211, modulating unit 212, string and converting unit 213, IFFT unit 214, compressed transform unit 215, receiving system 22 comprises FFT unit 221 for the first time, channel equalization unit 222, IFFT unit 223, transform expansion unit 224, the second time, the FFT unit 225, parallel serial conversion unit 226, demodulating unit 227, decoding unit 228.
In the present embodiment, transmitting terminal is finished the signal transmission according to existing ofdm signal production process based on compression PAPR inhibition method.
(1) 211 pairs of incoming bit streams of coding unit are encoded;
(2) signal behind 212 pairs of codings of modulating unit is modulated, and adopts quarternary phase-shift keying (QPSK) (QPSK) modulation here, obtains serial modulation signal X S
(3) string and the 213 couples of X in unit SGo here and there and change, obtain parallel modulation signal X k, wherein, k=0,1 ..., N-1, N represent the subcarrier number of ofdm signal;
(4) 214 couples of X in IFFT unit kCarry out the IFFT conversion, obtain time-domain signal x n, wherein, n=0,1 ..., N-1;
(5) compressed transform unit 215 is again to the time domain sequences { x of ofdm signal nCalculate, draw ofdm signal at the average amplitude v of time domain; According to the requirement of ofdm system, determine companding coefficient μ; Ofdm signal is carried out compressed transform, and the signal that obtains behind the companding transform is S (n), and its companding transform mode can adopt μ to lead compression, can adopt as the lower compression formula and compress:
S ( n ) = C { x n } = vx n 1 n ( 1 + u ) | x n | 1 n ( 1 + u v | x n | )
Wherein v is ofdm signal x nAverage amplitude, μ is the compressed coefficient; Compressed signal S (n) carried out and go here and there conversion and send into power amplifier, the high-power signal that amplifier is produced is transmitted into radio circuit to carry out signal and sends.Also can adopt other modes well known to those skilled in the art that signal is compressed.
Adopt the method for reseptance of the present invention's proposition at receiving terminal.
(1) time-domain signal that receives of receiving terminal is
Figure BDA00003251092700042
By FFT unit 221 first time, will
Figure BDA00003251092700043
Convert frequency-region signal to
Figure BDA00003251092700044
K=0,1 ..., N-1, N are the subcarrier number of ofdm signal;
(2) channel equalization unit is 222 pairs
Figure BDA00003251092700045
Do channel equalization, obtain the signal after the equilibrium treatment
(3) 223 pairs of signals in IFFT unit
Figure BDA00003251092700047
Carry out the IFFT conversion, obtain time-domain signal
Figure BDA00003251092700048
(4) 224 pairs of transform expansion unit obtain time-domain signal
Figure BDA00003251092700049
Carry out transform expansion, its transformation for mula is as follows:
y ( n ) = C - 1 { y n E } = vy n E u | y n E | { exp [ | y n E | 1 n ( 1 + u ) v ] - 1 }
Wherein For time-domain signal, v is
Figure BDA000032510927000412
Average amplitude, μ is the compressed coefficient;
(5) the signal y (n) after 225 pairs of transform expansions in FFT unit for the second time carries out the FFT conversion, obtains frequency domain sequence;
(6) and 226 pairs of sequences of string location carry out and go here and there conversion, separate the QPSK modulation by demodulating unit 227 then, last decoding unit 228 recovers transmitting terminal data bit flow (ofdm signal) by the information after the demodulation is deciphered.
By the existing ofdm communication system that proposes based on ofdm communication system and the present invention of compression expansion of comparative analysis, can find that the present invention can improve planisphere diffusion problem under the multi-path environment, and implementation procedure is simple.
To the above-mentioned explanation of the disclosed embodiments, make this area professional and technical personnel can realize or use the present invention.Multiple modification to these embodiment will be apparent concerning those skilled in the art, and defined General Principle can realize under the situation that does not break away from the spirit or scope of the present invention in other embodiments herein.Therefore, the present invention will can not be restricted to these embodiment shown in this article.

Claims (7)

1. ofdm communication system based on compression expansion, it is characterized in that, comprise: wired or wireless communication channel, dispensing device and receiving system, described dispensing device comprises the compressed transform module that suppresses the ofdm signal peak-to-average force ratio, the compressed transform module carries out sending to receiving system by the wired or wireless communication channel behind the compressed transform to signal, and receiving system restores the transmitting terminal ofdm signal according to the compressed signal that receives.
2. system according to claim 1 is characterized in that, described receiving system comprises for the first time FFT unit, channel equalization unit, IFFT unit, transform expansion unit, FFT unit for the second time, parallel serial conversion unit and decoding unit; The FFT unit carries out FFT conversion acquisition first time frequency-region signal to the compressed signal that receives for the first time, and the channel equalization that channel equalization unit is done on the frequency domain this frequency-region signal is sent into the IFFT unit; The signal of IFFT unit after to channel equalization carries out the IFFT treatment conversion to time domain, the transform expansion unit carries out transform expansion to the time-domain signal by the IFFT conversion and sends into FFT unit for the second time, with this time-domain signal through the second time FFT unit be transformed to frequency-region signal, send into parallel serial conversion unit, conversion is done and gone here and there to parallel serial conversion unit to logical this frequency-region signal, sends into decoding unit and decipher the acquisition ofdm signal.
3. system according to claim 1 is characterized in that, in the dispensing device compressed transform module to the time domain sequences of ofdm signal xn} calculates, and draws ofdm signal at the average amplitude v of time domain, determines companding coefficient μ, calls formula:
Figure FDA00003251092600011
Ofdm signal is carried out compressed transform, and the signal that obtains behind the compressed transform is S (n), and wherein v is ofdm signal x nAverage amplitude.
4. system according to claim 2 is characterized in that, the transform expansion unit is to time-domain signal in the receiving system
Figure FDA00003251092600012
Carry out transform expansion, according to formula:
Figure FDA00003251092600013
Signal y (n) after the acquisition transform expansion, wherein, μ is the compressed coefficient, v is that ofdm signal is at the average amplitude of time domain.
5. ofdm communication method based on compression expansion, it is characterized in that, dispensing device carries out compressed transform to signal and sends to receiving system by the wired or wireless communication channel, and receiving system receives the laggard line translation of compressed signal and handles the ofdm signal that restores transmitting terminal; Described receiving system carries out conversion process and comprises, in the receiving system for the first time the FFT unit compressed signal that receives carried out FFT conversion acquisition first time frequency-region signal send into channel equalization unit, channel equalization unit is done channel equalization on the frequency domain to this frequency-region signal; The IFFT unit will carry out IFFT by the signal after the channel equalization unit and be transformed into time domain, the transform expansion unit is to carrying out transform expansion by the time-domain signal behind the IFFT unit, the FFT conversion obtains second frequency-region signal to do for the second time by the signal after the transform expansion in the FFT unit for the second time, conversion is done and gone here and there to parallel serial conversion unit to second frequency-region signal, sends into decoding unit and decipher.
6. method according to claim 5 is characterized in that, the compressed transform unit is to the time domain sequences { x of ofdm signal in the dispensing device nCalculate, draw ofdm signal at the average amplitude v of time domain, determine companding coefficient μ, call formula: Ofdm signal is carried out compressed transform, and the signal that obtains behind the companding transform is S (n), and wherein v is ofdm signal x nAverage amplitude.
7. method according to claim 5 is characterized in that, the transform expansion unit is to obtaining time-domain signal
Figure FDA00003251092600022
Carry out transform expansion, according to formula:
Figure FDA00003251092600023
Signal y (n) after the acquisition transform expansion, wherein, μ is the compressed coefficient, v is that ofdm signal is at the average amplitude of time domain.
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Cited By (4)

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Publication number Priority date Publication date Assignee Title
CN103944853A (en) * 2014-04-24 2014-07-23 广东顺德中山大学卡内基梅隆大学国际联合研究院 Quasi-lossless compression method based on corrected OFDM sub-carriers
CN105306403A (en) * 2015-10-28 2016-02-03 西安邮电大学 Method and system for reducing peak-to-average ratio of transmitting signal of OFDM system
WO2022100584A1 (en) * 2020-11-10 2022-05-19 展讯半导体(成都)有限公司 Twice fft and ifft method, and related product
CN114826301A (en) * 2022-06-29 2022-07-29 天津七一二通信广播股份有限公司 Wide-band receiving equipment and receiving method with large dynamic range

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CN101478521A (en) * 2009-01-20 2009-07-08 华南理工大学 Peak cutting method for adaptive in-band processing
CN102325118A (en) * 2011-09-19 2012-01-18 西安电子科技大学 OFDM signal peak-to-average ratio inhibition method based on hyperbolic companding and combined amplitude limit

Patent Citations (4)

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Publication number Priority date Publication date Assignee Title
CN1392690A (en) * 2002-08-01 2003-01-22 上海交通大学 Amplitude compressino and expansion control method for peak-to-average ratio of orthogonal frequency division multi-plexing communication system
US20080247474A1 (en) * 2005-05-02 2008-10-09 Hak Seong Kim Apparatus and Method For Receiving Signals in Multi-Carrier Multi-Carrier Multiple Access Systems
CN101478521A (en) * 2009-01-20 2009-07-08 华南理工大学 Peak cutting method for adaptive in-band processing
CN102325118A (en) * 2011-09-19 2012-01-18 西安电子科技大学 OFDM signal peak-to-average ratio inhibition method based on hyperbolic companding and combined amplitude limit

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103944853A (en) * 2014-04-24 2014-07-23 广东顺德中山大学卡内基梅隆大学国际联合研究院 Quasi-lossless compression method based on corrected OFDM sub-carriers
CN105306403A (en) * 2015-10-28 2016-02-03 西安邮电大学 Method and system for reducing peak-to-average ratio of transmitting signal of OFDM system
WO2022100584A1 (en) * 2020-11-10 2022-05-19 展讯半导体(成都)有限公司 Twice fft and ifft method, and related product
CN114826301A (en) * 2022-06-29 2022-07-29 天津七一二通信广播股份有限公司 Wide-band receiving equipment and receiving method with large dynamic range
CN114826301B (en) * 2022-06-29 2022-10-21 天津七一二通信广播股份有限公司 Wide-band receiving equipment and receiving method with large dynamic range

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