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FORWARD ERROR CORRECTION FOR AN ATMOSPHERIC NOISE CHANNEL

IEEE TRANSACTIONS ON COMMUNICATIONS 1992年第5期40卷 863-872页

作者： OLSON, KE ENGE, PK WORCESTER POLYTECH INST DEPT ELECT ENGNWORCESTERMA 01609

Atmospheric noise is caused by lightning and dominates other natural radio noise sources below 30 MHz. A wide-band atmospheric noise process appears as low-power Gaussian background process with bursts of high-power impulses. The impulses are due to nearby lightning and cause the first-order density of atmospheric noise to have longer tails than the Gaussian distribution. They also tend to occur in groups which means that the atmospheric noise channel has memory. Digital radio systems which operate on the atmospheric noise channel can use hard decisions to desensitize the receiver to the bursts, and forward error correction to recover those symbols which are received incorrectly. If these systems use a high degree of interleaving, then the channel can be modelled as a binary symmetric channel. However, many radio systems which operate below 30 MHz must minimize data delay and therefore interleaving depth must be chosen carefully. This paper uses two Markov chains to model the memory of the atmospheric noise channel. It derives the transition probabilities for these chains from atmospheric noise error processes which were recorded at 306 kHz. Then, it uses the models to estimate the probability of codeword error, and compares these estimates to codeword error rates which are obtained directly from the recorded error processes. These comparisons are made for the Golay code with a variety of bit interleaving depths, and for a Reed-Solomon code with a variety of symbol interleaving depths. Both Markov channel models predict the actual performance of the codes with much greater accuracy than the binary symmetric channel. This paper also includes some results for binary convolutional codes.

关键词： Forward error correction PERFORMANCE CODES Reed-Solomon codes error correction codeword atmospherics Golay codes convolutional coding TRANSITION PROBABILITIES

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ERROR PROBABILITIES OF FAST FREQUENCY-HOPPED MFSK WITH NOISE-NORMALIZATION COMBINING IN A FADING CHANNEL WITH PARTIAL-BAND INTERFERENCE

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IEEE TRANSACTIONS ON COMMUNICATIONS 1992年第2期40卷 404-412页

作者： ROBERTSON, RC HA, TT Department of Electrical and Computer Engineering Code EC/RC Naval Postgraduate School Monterrey CA USA

An error probability analysis is performed for an Mary orthogonal frequency-shift keying (MFSK) communication system employing fast frequency-hopped (FFH) spread spectrum waveforms transmitted over a frequency-nonselective, slowly fading channel with partial-band interference. Diversity is obtained using multiple hops per data bit. A procedure referred to as noise-normalization combining is employed by the system receiver to minimize partial-band interference effects. Each diversity reception is assumed to fade independently according to a Rician process. The partial-band interference is modeled as a Gaussian process. Thermal noise is also included in the analysis. Forward error correction coding is applied using convolutional codes and Reed-Solomon codes. Diversity is found to dramatically reduce the degradation of the noise-normalization receiver caused by partial-band interference regardless of the strength of the direct signal component. In addition, diversity offers significant performance improvement when channel fading is strong. Further significant performance improvement is obtained for higher modulation orders (M > 2). Uncoded receiver performance with a diversity of four is roughly comparable to coded receiver performance with no diversity for ratios of bit energy-to-interference noise density in the range between roughly 12 and 22 dB. Substantial improvements in receiver performance are obtained by combining diversity, higher modulation orders, and coding.

关键词： Receivers performance boost Frequency hopping convolutional coding Error probability Fading channels frequency shift keying

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A MODEL FOR LOCAL MOBILE RADIO-COMMUNICATIONS WITH CORRECT PACKET CAPTURE

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IEEE TRANSACTIONS ON COMMUNICATIONS 1992年第4期40卷 847-854页

作者： ROBERTSON, RC HA, TT Department of Electrical and Computer Engineering Naval Postgraduate School Monterrey CA USA

An analysis of the performance of a local/mobile radio communications system utilizing the slotted ALOHA multiple random access protocol is presented in this paper. The probability of correct packet capture is evaluated for a local/mobile packet radio system using ideal coherent binary phase-shift keying (BPSK) modulation. Both the near/far effect and the effect of Rayleigh fading on the probability of correct packet capture are taken into account, but the effect of thermal noise is neglected since the interference due to competing packets is dominant in practical systems. The probability of correct packet reception is evaluated for a system using spatial diversity. In addition, the effect on system performance of either convolutional coding with hard decision Viterbi decoding or binary linear block coding with hard decision decoding is evaluated. The pseudo-Bayesian algorithm that has been developed to stabilize a packet system based on the slotted ALOHA protocol at maximum channel throughput is found to be adaptable to the local/mobile operating environment. For the slotted ALOHA system considered in this paper, it is possible to obtain channel throughputs as high as 0.66 provided a spatial diversity of around ten can be implemented.

关键词： Radiocommunication hard-decision decoding Slotted ALOHA Thermal noise Rayleigh fading Throughput spatial diversity Viterbi decoding System performance Packet convolutional coding

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USE OF RESIDUAL REDUNDANCY IN THE DESIGN OF JOINT SOURCE CHANNEL CODERS

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IEEE TRANSACTIONS ON COMMUNICATIONS 1991年第6期39卷 838-846页

作者： SAYOOD, K BORKENHAGEN, JC AT&T BELL LABS MURRAY HILL NJ 07974 USA

The need to transmit large amounts of data over a band-limited channel has led to the development of various data compression schemes. Many of these schemes function by attempting to remove redundancy from the data stream. An unwanted side-effect of this approach is to make the information transfer process more vulnerable to channel noise. Efforts at protecting against errors involve the reinsertion of redundancy and an increase in bandwidth requirements. We present a technique for providing error protection without the additional overhead required for channel coding. We start from the premise that, during source coder design, for the sake of simplicity or due to imperfect knowledge, assumptions have to be made about the source which are often incorrect. This results in residual redundancy at the output of the source coder. The residual redundancy can then be used to provide error protection in much the same way as the insertion of redundancy in convolutional coding provides error protection. In this paper we develop an approach for utilizing this redundancy. To show the validity of this approach, we apply it to image coding using DPCM, and obtain substantial performance gains, both in terms of objective as well as subjective measures.

关键词： redundancy differential pulse code modulation image coding Writers convolutional coding ENCODER error protection RESIDUAL PREMISES Channel coding Sake

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OPTIMAL INTERLEAVING SCHEME FOR convolutional coding

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ELECTRONICS LETTERS 1989年第22期25卷 1517-1518页

作者： DUNSCOMBE, E PIPER, FC Dept. of Math. R. Holloway & Bedford New Coll. Egham UK

An optimal scheme is given for interleaving using an n*m array when the maximum length burst of errors is greater than m. It involves transmitting the rows of the array in a specified (nonsequential) order, but introd... 详细信息

关键词： burst errors coding errors convolutional coding encoding error correction codes interleaving scheme optimal scheme

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THE PERFORMANCE OF RATE-COMPATIBLE PUNCTURED convolutional-CODES FOR DIGITAL MOBILE RADIO

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IEEE TRANSACTIONS ON COMMUNICATIONS 1990年第7期38卷 966-980页

作者： HAGENAUER, J SESHADRI, N SUNDBERG, CEW AT&T BELL LABS MURRAY HILLNJ 07974

The unequal error protection capabilities of convolutional codes belonging to the family of rate-compatible punctured convolutional codes (RCPC codes) are studied. The performance of these codes is analyzed and simulated for the first fading Rice and Rayleigh channels with differentially coherent four-phase modulation (4-DPSK). To mitigate the effect of fading, interleavers are designed for these unequal error protection codes, with the interleaving performed over one or two blocks of 256 channel bits. These codes are decoded by means of the Viterbi algorithm using both soft symbol decisions and channel state information. For reference, the performance of these codes on a Gaussian channel with coherent binary phase-shift keying (2-CPSK) is presented. A number of examples are provided to show that it is possible to accommodate widely different error protection levels within short information blocks. Unequal error protection codes for a subband speech coder are studied in detail. A detailed study of the effect of the code and channel parameters such as the encoder memory, the code rate, interleaver depth, fading bandwidth, and the contrasting performance of hard and soft decisions on the received symbols is provided.

关键词： fading color error protection inequalities Codes Viterbi algorithm protection level Gaussian channels Channel state information convolutional coding soft decision

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convolutionalLY CODED FREQUENCY-HOPPING COMMUNICATIONS WITH NONIDEAL INTERLEAVING

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 1990年第5期8卷 823-836页

作者： LAUFER, S REICHMAN, A TEL AVIV UNIV DEPT ELECTR SYSTIL-69978 TEL AVIVISRAEL

The interleaving span of coded frequency-hopped (FH) systems is often constrained to be smaller than the decoder memory length, i.e. nonideal interleaving is performed. An upper bound on the performance of a Viterbi decoder of a convolutional code with nonideal interleaving is presented. A soft decision diversity combining technique is introduced, and the performance of combined convolutional and diversity coding subject to worst-case partial band noise jamming is investigated. Optimization of the FH system performance subject to constraints of allowed delay and synthesizer settling time provides the best combination of interleaving span and hopping rate. The FH system considered employs M-ary frequency-shift key (MFSK) modulation and noncoherent demodulation with 2-b soft decision based on Viterbi's ratio-threshold technique.

关键词： soft decision Viterbi decoders noncoherent demodulation Frequency hopping convolutional coding frequency shift keying

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ON THE PERFORMANCE OF RATE 1/2 convolutional-CODES WITH QPSK ON RICIAN FADING CHANNELS

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 1990年第2期39卷 161-170页

作者： CHEN, YL WEI, CH Institute of Electronics National Chiao Tung University Hsinchu Taiwan

Consideration is given to the bit error probability performance of rate 1/2 convolutional codes in conjunction with quaternary phase shift keying (QPSK) modulation and maximum-likelihood Viterbi decoding on fully interleaved Rician fading channels. Applying the generating function union bounding approach, an asymptotically tight analytic upper bound on the bit error probability performance is developed under the assumption of using the Viterbi decoder with perfect fading amplitude measurement. Bit error probability performance of constraint length K=3-7 codes with QPSK is numerically evaluated using the developed bound. Tightness of the bound is examined by means of computer simulation. The influence of perfect amplitude measurement on the performance of the Viterbi decoder is observed. A performance comparison with rate 1/2 codes with binary phase shift keying (BPSK) is provided.

关键词： Viterbi decoders Binary phase shift keying Quadrature phase shift keying bit error probability convolutional coding Computer Simulation Rician fading channels Performance appraisal

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THE USE OF INTERLEAVING FOR REDUCING NOISY REFERENCE LOSS IN TRELLIS-CODED MODULATION SYSTEMS

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IEEE TRANSACTIONS ON COMMUNICATIONS 1990年第8期38卷 1190-1198页

作者： DIVSALAR, D SIMON, MK Jet Propulsion Laboratory California Institute of Technology Pasadena CA USA

The use of interleaving/deinterleaving in trellis-coded modulation systems to reduce the SNR loss due to imperfect carrier demodulation references is demonstrated. Both the discrete carrier (phase-locked loop) and the suppressed carrier (Costas loop) cases are considered, and the differences between the two are clearly demonstrated by numerical results. The special case of convolutional codes is also treated and illustrated with an example of practical interest.

关键词： trellis coded modulation carrier suppression Costas loop convolutional coding

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COMBINED CODED MULTI-H CPFSK SIGNALING

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IEEE TRANSACTIONS ON COMMUNICATIONS 1990年第10期38卷 1708-1715页

作者： FONSEKA, JP DAVIS, GR ARIZONA STATE UNIV DEPT ELECT ENGNTEMPEAZ 85287

A continuous-phase frequency-shift-keying (CPFSK) signaling technique is suggested that combines convolutional encoding and multi-h signaling. In contrast to regular multi-h signaling, this technique changes the modulation index in a preselected pattern in order to maximize the minimum Euclidean distance. A rate-1/2 convolutional encoder along with a 2-h quaternary CPFSK modulator which uses two fixed modulation indexes is considered. Minimum Euclidean distances are calculated corresponding to the best encoder/mapper combinations for different modulation index patterns at attractive pairs of modulation indexes. Numerical results obtained for encoder memory lengths of one and two are used to illustrate that the minimum Euclidean distance of coded CPFSK signals can be significantly increased by combining with multi-h signaling. Modulation index patterns which perform significantly better than regular multi-h signals are determined. An error event analysis over the additive-white-Gaussian noise channel is carried out to investigate the actual error rate performance and to verify the theoretical results.

关键词： Euclidean distance convolutional coding frequency shift keying

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