ISSN:0737-2884    

DOI:10.1002/sat.4600070302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0737-2884    

DOI:10.1002/sat.4600070303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractSpread‐spectrum techniques such as frequency hopping (FH) have been used to reduce the vulnerability of satellite communications to jamming. In such a system, error correcting (EC) codes play an essential role. Thus a knowledge of the performance of various EC codes is necessary in order to choose an EC code and related system parameters in the design of an anti‐jam system, this paper examines the performance of various types of error correcting codes under worst case partial band noise jamming and worst case multitone jamming using fast frequency‐hopped, non‐coherentM‐ary frequency‐shift keying (NCMFSK) with optimum diversity. A comprehensive study including convolutional codes, binary and non‐binary block codes and concatenated codes has been conducted. This paper presents bit error rate (BER) performances of various error correcting codes. New candidate codes with superior anti‐jam performance

ISSN:0737-2884    

DOI:10.1002/sat.4600070304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractForward error correction (FEC) has become a general requirement for digital satellite communications. The dominant technology is the use of convolutional codes with Viterbi decoding. At MPR (Microtel Pacific Research), a single‐chip VLSI implementation of a convolutional encoder and Viterbi decoder for constraint length 7 has been completed recently. In the design and application of the FEC chip, several practical issues had to be addressed. These include the determination of the maximum variation in path metric, generation of a convolutional encoded sequence with maximum number of transitions for symbol timing recovery, use of a unique word to detect the phase ambiguity, use of a sliding window data quality monitor to resolve an ambiguous state, etc. This paper presents our solutions to these problems. Although specific results are given for the standard constraint‐length 7 code, the methods used to obtain these results are general and can be applied to other codes. Features and implementation of the VLSI FEC chip are also discus

ISSN:0737-2884    

DOI:10.1002/sat.4600070305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe deployment of channel coding and interleaving to enhance the bit‐error performance of a satellite mobile radio channel is addressed for speech and data transmissions. Different convolutional codes (CC) using Viterbi decoding with soft decision are examined with inter‐block interleaving. Reed‐Solomon (RS) codes with Berlekamp‐Massey hard decision decoding or soft decision trellis decoding combined with block interleaving are also investigated. A concatenated arrangement employing RS and CC coding as the outer and inner coders, respectively, is used for transmissions via minimum shift keying (MSK) over Gaussian and Rayleigh fading channels. For an interblock interleaving period of 2880 bits, a concatenated arrangement of an RS(48,36). over the Galois field GF(256) and punctured PCC(3,1,7) yielding an overall coding rate of 1/2, provides a coding gain of 42dB for a BER of 10−6, and an uncorrectable error detection probability

ISSN:0737-2884    

DOI:10.1002/sat.4600070306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractDigital satellite communication systems use coherent quaternary PSK (QPSK) as the preferred modulation scheme. In recent years, however, the search for bandwidth and power‐efficient digital modulation methods has become an active research area. In this paper the performances of combined coding and modulation schemes employing multilevel signal alphabets are considered, in the framework of a system model which reasonably approximates the INTELSAT SCPC system. The main goal of the research was to investigate whether the efficiency of coded modulation schemes and their savings in transmitted power could be maintained in a system environment dominated by interference more than by the additive white Gaussian noise. A second goal was to compare the performance of signals with constant envelope, such as multilevel PSK, with that of signals allowing variations in amplitude, such as multilevel PSK, with that of signals allowing variations in amplitude, such as multilevel QAM. In the paper, we propose a channel model which is reasonably close to the real system, and a method for performance evaluation leading to an estimate of the asymptotic power gain of the modulation systems. The channel model and the method are applied to the analysis of coded 16‐ and 32‐ PSK an

ISSN:0737-2884    

DOI:10.1002/sat.4600070307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractWe introduce the concept of weighted‐output decoding, which enables us to perform many successive decodings without information loss. The design of a coding system for the additive white Gaussian channel can thus be viewed as a means for combining many simple codes. We illustrate this concept by the example of parity‐check codes which are combined according to Elias' iterated product. Examination of the performance thus obtained leads us to criticize the conventional minimal distance criterion and to propose as a criterion a proximity measure of the weight distribution of the code with respect to the binomial one. According to this point of view, the iterated product of parity‐check codes appears as a means of decimation of the set ofn

ISSN:0737-2884    

DOI:10.1002/sat.4600070308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractIn this paper, the performance of some efficient ARQ schemes which make use of repeated transmissions of the same data block and compound detection are analysed. The repeated transmission of the same data block involves repeated transmission of each symbol of the data block. At the receiving end, compound detection formed of a soft detection jointly with a classical hard detection is performed by using all the received copies of the same symbol. The throughput efficiencies for the proposed ARQ schemes are analytically derived in closed form and optimized with respect to the number of copies to be transmitted for each data block. It will be shown that the optimized ARQ schemes proposed in this paper achieve better performance than classical ARQ schemes, in particular under high error rate conditions.

ISSN:0737-2884    

DOI:10.1002/sat.4600070309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractWith the advent of the open systems interconnection philosophy, interworking between satellite and ground‐based data networks is rapidly becoming important. X.25 LAPB/HDLC is an important standard in this field. It defines a connection between two data switching nodes. This paper examines how a low capacity (∼kb/s) anti‐jam (A/J) satellite circuit may carry a X.25 LAPB/HDLC data link.It has been shown that use of an unmodified A/J modem employing convolutional coding gives a particularly poor performance in the presence of jamming. A study of the properties which govern the performance of a packet link has led to some recommendations for a special ‘packet mode’ for anti‐jam modems and to some suggested extensions to the data link protocol. These recommendations have been implemented in a simulator and this has revealed a performance far superior to an unmodified system. The recommendations are being implemented in a trials system, developed at the University of Aberdeen, for R

ISSN:0737-2884    

DOI:10.1002/sat.4600070310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractA study of reduced complexity concatenated coding schemes, for commercial digital satellite systems with low‐cost earth terminals, is reported. The study explored trade‐offs between coding gain, overall rate and decoder complexity, and compared concatenated schemes with single codes. It concentrated on short block and constraint length inner codes, with soft decision decoding, concatenated with a range of Reed‐Solomon outer codes. The dimension of the inner code was matched to the outer code symbol size, and appropriate interleaving between the inner and outer codes was used. Very useful coding gains were achieved with relatively high‐rate, low‐complexity schemes. For example, concatenating the soft decision decoded (9,8) single parity check inner code with the CCSDS recommended standard Reed‐Solomon outer code gives a coding gain of 4.8dB at a bit error probability of 10−5, with an overall

ISSN:0737-2884    

DOI:10.1002/sat.4600070311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY