CN110176977A - High-order QAM soft decision method in OFDM data chain based on AGC - Google Patents

High-order QAM soft decision method in OFDM data chain based on AGC Download PDF

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CN110176977A
CN110176977A CN201910417717.9A CN201910417717A CN110176977A CN 110176977 A CN110176977 A CN 110176977A CN 201910417717 A CN201910417717 A CN 201910417717A CN 110176977 A CN110176977 A CN 110176977A
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agc
soft
signal
inform ation
indicate
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CN110176977B (en
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闫朝星
罗翔
王先朋
付林罡
李辉
李响
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Aerospace Long March Launch Vehicle Technology Co Ltd
Beijing Institute of Telemetry Technology
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Aerospace Long March Launch Vehicle Technology Co Ltd
Beijing Institute of Telemetry Technology
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0045—Arrangements at the receiver end
    • H04L1/0054—Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/52—TPC using AGC [Automatic Gain Control] circuits or amplifiers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/38—Demodulator circuits; Receiver circuits

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Artificial Intelligence (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)

Abstract

The invention discloses the high-order QAM soft decision methods based on AGC in a kind of OFDM data chain, first estimation OFDM frame frequency domain pilot signal rp(k) signal power PSWith noise power PN, and to received business datum signal rd(k) automatic growth control processing is carried out, z is obtainedd(k)；Then by zd(k) soft-decision demapping is carried out, corresponding Soft Inform ation is obtained, is used for subsequent decoding.The present invention accurately estimates the signal power of frequency-region signal in OFDM receiver by pilot frequency carrier wave or virtual subcarrier, setting receives the target power value of signal AGC accordingly, then to the Soft Inform ation for receiving signal and calculating quantization after adjust gain, and the quantization format of Soft Inform ation is associated with AGC target power value, to promote the accuracy of Soft Inform ation with lower computation complexity.

Description

High-order QAM soft decision method in OFDM data chain based on AGC
Technical field
The present invention relates to the high-order QAM soft decision methods based on AGC in a kind of OFDM data chain, belong to digital wireless communication Transmission technique field.
Background technique
In aircraft data catenary system, with airborne mission payload capability improving, Ground-to-Air Data Link needs to provide high speed Business data transmission.Meanwhile there are biggish multi-path jammings for earth-to-space link, and communication system is needed to interfere with resistance to frequency selective Ability.Therefore, aircraft data link is frequently with orthogonal frequency division multiplexing (OFDM) technology, high order quadrature amplitude modulation (QAM) and height It imitates channel error correction encoding such as Turbo code or LDPC code and realizes high-speed transfer and anti-interference ability.But in OFDM data chain receiver Middle high-order QAM modulation, which needs accurate soft-decision to calculate likelihood information, just can guarantee decoding performance.
Document " improved 16QAM soft decision demodulation algorithm [J] modern electronic technology in ofdm system, 2012,35 (3): 119-122. " improves the signal noise ratio level of signal totality in equilibrium using channel information, and soft-decision result is made to include more More channel information, to improve the performance of Soft decision decoding.Document " quickly generates QAM bit confidence coefficient soft-decision metrics Algorithm [J] electronics and information journal, 2009,31 (4): 985-988. " is by introducing QAM soft-decision degree for bit confidence coefficient The complexity of calculating is reduced in the calculating of amount." Soft Inform ation of shortwave number crossing signal extracts and frequency-domain equalization technology research, west Peace 2014. " square shaped 16QAM signal of University of Electronic Science and Technology and non-square 16APSK signal are simplified.Document " Look-up table based low complexity LLR calculation for high-order amplitude phase shift keying signals[J].IEICE Transactions on Communications,2012,E95(B(9)): 2936-2938. " also simplify 16APSK signal Soft Inform ation calculation method.
But above-mentioned document spininess is analyzed algorithm itself, simplified and is improved, and is not directed in practical receiver and has Body realizes that technology is comprehensively considered, with optimization demodulation and decoding performance.
Summary of the invention
Technical problem solved by the present invention is overcome the shortage of prior art, provide in a kind of OFDM data chain based on AGC's Soft Inform ation is calculated and is combined with AGC by high-order QAM soft decision method, promotes the accurate of Soft Inform ation with lower computation complexity Degree.
Technical solution of the invention are as follows:
High-order QAM soft decision method in OFDM data chain based on AGC, includes the following steps:
Step 1: estimation OFDM frame frequency domain pilot signal rp(k) signal power PSWith noise power PN, and to received Business datum signal rd(k) automatic growth control processing is carried out, z is obtainedd(k)；
Step 2: by zd(k) soft-decision demapping is carried out, corresponding Soft Inform ation is obtained, is used for subsequent decoding.
In the step 1, P is estimatedSMethod it is as follows:
According to following formula, pilot signal r is utilizedp(k) signal power estimation P is obtainedS:
NpFor pilot signal rp(k) length, xp(k) pilot signal that transmitting terminal is sent is indicated.
In the step 1, noise power:
In the step 1, as virtual number of sub carrier wave Nu>=pilot signal rp(k) length NpWhen, it is carried using virtual subnet Wave ru(k) noise power estimation P is obtainedN:
In the step 1, as virtual number of sub carrier wave Nu>=pilot signal rp(k) length NpWhen,
Wherein NdCalculate the signal number for receiving total power signal.
In the step 1, z is obtained by the following methodd(k):
It will quantify format < Ld,Li,Lf> rd(k) AGC gain is carried out to adjust to obtain quantization format < Ld,Li,Lf> zd(k):
Wherein, Ld=Li+Lf+ 1 indicates signed number according to rd(k) quantization bit wide, LiIndicate integer-bit bit wide, LfIndicate small Numerical digit bit wide；η is gain adjustment factor, η=P0/PS, P0For the target power value of AGC；Target power value P0Corresponding one virtual Constellation point, real part, imaginary part are set asAnd have
In the step 2, when the signal that transmitting terminal is sent is 16QAM, to zd(k) soft-decision demapping is carried out, is obtained The corresponding Soft Inform ation of 4 bits b1, b2, b3, b4, specific implementation are as follows:
Utilize zd(k) quantization format < L is calculatedd,Li,Lf> Soft Inform ation:
Lb1(k)=Re { zd(k)}
Lb3(k)=Im { zd(k)}
Wherein, if the real part of 16QAM modulation constellation points, imaginary part coordinate be a, 3a, thenIndicate constellation Point median, | | | | indicate floor operation；Ld=Li+Lf+ 1 indicates signed number according to rd(k) quantization bit wide, LiIndicate integer Position bit wide, LfIndicate decimal place bit wide.
To Lb1(k)、Lb2(k)、Lb3(k)、Lb4(k) cut position obtains the Soft Inform ation for decoding, which is Nd= Ni+Nf+ 1, quantization format is < Nd,Ni,Nf>, NiIndicate Soft Inform ation integer-bit bit wide, NfIndicate Soft Inform ation decimal place bit wide.
In the step 2, when the signal that transmitting terminal is sent is 64QAM, to zd(k) soft-decision demapping is carried out, is obtained The corresponding Soft Inform ation of 6 bits b1, b2, b3, b4, b5, b6, specific implementation are as follows:
Utilize zd(k) quantization format < L is calculatedd,Li,Lf> Soft Inform ation:
Lb1(k)=Re { zd(k)}
Lb4(k)=Im { zd(k)}
Wherein, Ld=Li+Lf+ 1 indicates signed number according to rd(k) quantization bit wide, LiIndicate integer-bit bit wide, LfIndicate small Numerical digit bit wide.
To Lb1(k)、Lb2(k)、Lb3(k)、Lb4(k)、Lb5(k)、Lb6(k) cut position obtains the Soft Inform ation for decoding, this is soft Information bit wide is Nd=Ni+Nf+ 1, quantization format is < Nd,Ni,Nf>, NiIndicate Soft Inform ation integer-bit bit wide, NfIndicate that Soft Inform ation is small Numerical digit bit wide.
The advantages of the present invention over the prior art are that:
(1) Soft Inform ation is calculated and is tied with AGC phase by the high-order QAM soft decision method based on AGC in OFDM data chain of the present invention Soft Inform ation accuracy in computation, target power value P can be improved in conjunction0For 2 power, gain adjustment factor can be reduced and calculate complexity Degree.
(2) the high-order QAM soft decision method based on AGC in OFDM data chain of the present invention, using pilot tone or virtually in AGC The algorithm that sub-carrier signal calculates signal power estimation is not influenced by OFDM receiver carrier synchronization；
(3) the high-order QAM soft decision method based on AGC is suitable for high-order QAM modulation, likelihood in OFDM data chain of the present invention Information quantization format combines constellation point feature, has implementation complexity low, the small feature of performance loss.
Detailed description of the invention
Fig. 1 is the high-order QAM soft decision method block diagram based on AGC in OFDM data chain of the present invention；
Fig. 2 is the schematic diagram that the present invention uses 16QAM and 64QAM mapping mode, wherein (a) is 16QAM mapping mode, It (b) is 64QAM mapping mode；
Fig. 3 is the high-order QAM soft decision method AGC signal constellation point based on AGC in OFDM data chain of the present invention；
Fig. 4 is the statistical distribution of the high-order QAM soft decision method calculating LLR in OFDM data chain of the present invention based on AGC；
Fig. 5 is the LDPC decoding performance of the high-order QAM soft decision method based on AGC in OFDM data chain of the present invention.
Specific embodiment
The present invention will be further explained below with reference to the attached drawings.
High-order QAM soft decision method in OFDM data chain of the present invention based on AGC, mainly includes the following steps:
Step (1), estimation OFDM frame frequency domain pilot signal rp(k) signal power PSWith noise power PN, and to reception Business datum signal rd(k) carry out automatic growth control (AGC) processing, obtains zd(k)。
Frequency-domain OFDM frame is by length NpQPSK modulated pilots signal rp(k) with length NrM-QAM modulate traffic data letter Number rd(k) it forms, frequently with 4QAM or high order modulation 16QAM and 64QAM etc..OFDM frame length is Ns=Nu+Nr+Np, NuIt is virtual Number of sub carrier wave.
First with pilot signal rp(k) signal power estimation P is obtainedS,
Noise power
Or work as Nu≥NpThe virtual subcarrier r of Shi Liyongu(k) noise power estimation P is obtainedN,
Wherein | | absolute value, x are asked in expressionp(k) pilot signal that originator is sent is indicated.
Then the target power value P of AGC is set0, and acquire gain adjustment factor η=P0/PS, lattice will be quantified in the implementation Formula < Ld,Li,Lf> rd(k) AGC gain is carried out to adjust to obtain quantization format < Ld,Li,Lf> zd(k):
Wherein, Ld=Li+Lf+ 1 indicates signed number according to rd(k) quantization bit wide, LiIndicate integer-bit bit wide, LfIndicate small Numerical digit bit wide.
Set target power value P0A corresponding dummy constellation point, real part, imaginary part are set asAnd haveAt this point, Dynamic geneP need to only be changed during realizationSInteger-bit and decimal bit length Degree.
Step (2), the z by gain adjustment for obtaining step (1)d(k) soft-decision demapping is carried out, is corresponded to Soft Inform ation.
When the signal that transmitting terminal is sent is 16QAM, to zd(k) carry out soft-decision demapping, obtain 4 bit b1, b2, The corresponding Soft Inform ation of b3, b4, specific implementation are as follows:
Utilize zd(k) quantization format < L is calculatedd,Li,Lf> Soft Inform ation:
Lb1(k)=Re { zd(k)}
Lb3(k)=Im { zd(k)}
Wherein, if the real part of 16QAM modulation constellation points, imaginary part coordinate be a, 3a, thenIndicate constellation Point median, | | | | indicate floor operation；Ld=Li+Lf+ 1 indicates signed number according to rd(k) quantization bit wide, LiIndicate integer Position bit wide, LfIndicate decimal place bit wide.
To Lb1(k)、Lb2(k)、Lb3(k)、Lb4(k) cut position obtains the Soft Inform ation for decoding, which is Nd= Ni+Nf+ 1, quantization format is < Nd,Ni,Nf>, NiIndicate Soft Inform ation integer-bit bit wide, NfIndicate Soft Inform ation decimal place bit wide.
When the signal that transmitting terminal is sent is 64QAM, to zd(k) carry out soft-decision demapping, obtain 6 bit b1, b2, The corresponding Soft Inform ation of b3, b4, b5, b6, specific implementation are as follows:
Utilize zd(k) quantization format < L is calculatedd,Li,Lf> Soft Inform ation:
Lb1(k)=Re { zd(k)}
Lb4(k)=Im { zd(k)}
Then, to Lb1(k)、Lb2(k)、Lb3(k)、Lb4(k)、Lb5(k)、Lb6(k) cut position obtains the Soft Inform ation for decoding, The Soft Inform ation bit wide is Nd=Ni+Nf+ 1, quantization format is < Nd,Ni,Nf>, NiIndicate Soft Inform ation integer-bit bit wide, NfIndicate soft letter Cease decimal place bit wide.
General desirable quantization format is<6,2,3>.
Fig. 1 be OFDM data chain in the high-order QAM soft decision method block diagram based on AGC, by frequency domain synchronization with it is balanced after Ofdm signal extracts pilot tone and business datum, carries out signal power estimation and controls with AGC gain, it is (soft to sentence then to calculate Soft Inform ation Certainly likelihood information), finally give ldpc decoder.
Fig. 2 show the 16QAM mapping mode schematic diagram of frequency domain use.
Below with one embodiment to the performance of the high-order QAM soft decision method based on AGC in OFDM data chain of the present invention Simulation result is analyzed.
It is<9 that Fig. 3, which show quantization format, 3,5>when business datum constellation point at 20dB, set echo signal power is P0=22×5+1=2048.
The quantization format that Fig. 4 show Soft Inform ation is<6,2,3>when, the statistics of the ofdm signal of a frame signal-to-noise ratio 7.5dB Distribution situation, it is seen that signal amplitude is substantially≤20.
Fig. 5 show the performance after being decoded using the LDPC code of code length 4000, code efficiency 1/2, from simulation result Analysis is it is found that in BER=3 × 10-5When, theoretical simulation 7.2dB, the method for the present invention is about 7.5dB, therefore soft-decision side of the present invention Method after quantization performance than simulation performance lose about 0.3dB.
The present invention accurately estimates the signal function of frequency-region signal in OFDM receiver by pilot frequency carrier wave or virtual subcarrier Rate, setting receives the target power value of signal AGC accordingly, then to the Soft Inform ation for receiving signal and calculating quantization after adjust gain (likelihood information), and the quantization format of Soft Inform ation is associated with AGC target power value, to be mentioned with lower computation complexity Rise the accuracy of Soft Inform ation.
Unspecified part of the present invention belongs to techniques well known.

Claims (10)

  1. High-order QAM soft decision method in 1.OFDM data-link based on AGC, it is characterised in that include the following steps:
    Step 1: estimation OFDM frame frequency domain pilot signal rp(k) signal power PSWith noise power PN, and to received business Data-signal rd(k) automatic growth control processing is carried out, z is obtainedd(k)；
    Step 2: by zd(k) soft-decision demapping is carried out, corresponding Soft Inform ation is obtained, is used for subsequent decoding.
  2. 2. the high-order QAM soft decision method in OFDM data chain according to claim 1 based on AGC, it is characterised in that: institute It states in step 1, estimates PSMethod it is as follows:
    According to following formula, pilot signal r is utilizedp(k) signal power estimation P is obtainedS:
    NpFor pilot signal rp(k) length, xp(k) pilot signal that transmitting terminal is sent is indicated.
  3. 3. the high-order QAM soft decision method in OFDM data chain according to claim 2 based on AGC, it is characterised in that: institute It states in step 1, noise power:
  4. 4. the high-order QAM soft decision method in OFDM data chain according to claim 1 based on AGC, it is characterised in that: institute It states in step 1, as virtual number of sub carrier wave Nu>=pilot signal rp(k) length NpWhen, utilize virtual subcarrier ru(k) it obtains Noise power estimation PN:
  5. 5. the high-order QAM soft decision method in OFDM data chain according to claim 4 based on AGC, it is characterised in that: institute It states in step 1, as virtual number of sub carrier wave Nu>=pilot signal rp(k) length NpWhen,
    Wherein NdCalculate the signal number for receiving total power signal.
  6. 6. the high-order QAM soft decision method in OFDM data chain according to claim 1 based on AGC, it is characterised in that: institute It states in step 1, obtains z by the following methodd(k):
    It will quantify format < Ld,Li,Lf> rd(k) AGC gain is carried out to adjust to obtain quantization format < Ld,Li,Lf> zd(k):
    Wherein, Ld=Li+Lf+ 1 indicates signed number according to rd(k) quantization bit wide, LiIndicate integer-bit bit wide, LfIndicate decimal place Bit wide；η is gain adjustment factor, η=P0/PS, P0For the target power value of AGC；Target power value P0A corresponding dummy constellation Point, real part, imaginary part are set asAnd have
  7. 7. the high-order QAM soft decision method in OFDM data chain according to claim 1 based on AGC, it is characterised in that: institute It states in step 2, when the signal that transmitting terminal is sent is 16QAM, to zd(k) carry out soft-decision demapping, obtain 4 bit b1, The corresponding Soft Inform ation of b2, b3, b4, specific implementation are as follows:
    Utilize zd(k) quantization format < L is calculatedd,Li,Lf> Soft Inform ation:
    Lb1(k)=Re { zd(k)}
    Lb3(k)=Im { zd(k)}
    Wherein, if the real part of 16QAM modulation constellation points, imaginary part coordinate be a, 3a, thenIt indicates in constellation point Between be worth, | | | | indicate floor operation；Ld=Li+Lf+ 1 indicates signed number according to rd(k) quantization bit wide, LiIndicate integer-bit position Width, LfIndicate decimal place bit wide.
  8. 8. the high-order QAM soft decision method in OFDM data chain according to claim 7 based on AGC, it is characterised in that: right Lb1(k)、Lb2(k)、Lb3(k)、Lb4(k) cut position obtains the Soft Inform ation for decoding, which is Nd=Ni+Nf+ 1, amount Changing format is < Nd,Ni,Nf>, NiIndicate Soft Inform ation integer-bit bit wide, NfIndicate Soft Inform ation decimal place bit wide.
  9. 9. the high-order QAM soft decision method in OFDM data chain according to claim 1 based on AGC, it is characterised in that: institute It states in step 2, when the signal that transmitting terminal is sent is 64QAM, to zd(k) carry out soft-decision demapping, obtain 6 bit b1, The corresponding Soft Inform ation of b2, b3, b4, b5, b6, specific implementation are as follows:
    Utilize zd(k) quantization format < L is calculatedd,Li,Lf> Soft Inform ation:
    Lb1(k)=Re { zd(k)}
    Lb4(k)=Im { zd(k)}
    Wherein, Ld=Li+Lf+ 1 indicates signed number according to rd(k) quantization bit wide, LiIndicate integer-bit bit wide, LfIndicate decimal place Bit wide.
  10. 10. the high-order QAM soft decision method in OFDM data chain according to claim 9 based on AGC, it is characterised in that: To Lb1(k)、Lb2(k)、Lb3(k)、Lb4(k)、Lb5(k)、Lb6(k) cut position obtains the Soft Inform ation for decoding, the Soft Inform ation bit wide For Nd=Ni+Nf+ 1, quantization format is < Nd,Ni,Nf>, NiIndicate Soft Inform ation integer-bit bit wide, NfIndicate Soft Inform ation decimal place position It is wide.
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