Showing papers on "Forward error correction published in 1986"
TL;DR: This work considers trellis-coding techniques for improving the reliability of digital transmission over noisy partial-response channels by using convolutional codes designed for maximum free Hamming distance in conjunction with a precoder to obtain essentially equivalent codes.
Abstract: We consider trellis-coding techniques for improving the reliability of digital transmission over noisy partial-response channels. Such channels are commonly encountered in digital communication systems, and also play a role in devices for data recording. Concentrating on the channels with characteristics (1 \mp D) , we study methods to obtain codes which increase free Euclidean distance between permitted sequences of channel outputs and avoid the occurrence of unlimited runs of identical outputs at the expense of some loss in data rate. One technique employs the concept of set partitioning. The other is based on using convolutional codes designed for maximum free Hamming distance in conjunction with a precoder. Both methods lead to essentially equivalent codes.
164 citations
TL;DR: A variety of constant-weight block codes of increasing length are presented, including a code of length 16 that is being implemented for a very high-speed, ultra-reliable, ring data network.
Abstract: This paper discusses the possibilities of using certain constant-weight block codes in optical data links and in optical ring networks. The codes that appear to be particulary attractive have exactly as many 1s as 0s in each code word, so there is no penalty for ac coupling. Codes can be simple, such as the Manchester code. Or they may be more complicated and support control channel signaling, error detection, and forward error correction. This paper bridges the gap that sometimes exists between the mathematically “ideal” block codes and the typical requirements of particular applications. It presents a variety of constant-weight codes of increasing length, including a code of length 16 that is being implemented for a very high-speed, ultra-reliable, ring data network.
27 citations
Patent•
16 Jul 1986TL;DR: In this paper, the fixed stuffing information is replaced with forward error correction (FEC) information, whereby FEC is effected without any increase in transmission speed, and an FEC decoder acts in a self-framing manner to synchronize itself to the FEC information blocks of the respective data stream.
Abstract: In a high-speed fiber-optic transmission system, data streams are synchronized using fixed stuffing before being multiplexed for transmission. The fixed stuffing information is replaced with forward error correction (FEC) information, whereby FEC is effected without any increase in transmission speed. FEC information blocks of each data stream can be synchronized to the frame timing of the transmission system, or they can be relatively unsynchronized. In the latter case, an FEC decoder acts in a self-framing manner to synchronize itself to the FEC information blocks of the respective data stream.
18 citations
TL;DR: A combined modulation/error correcting trellis code suitable for magnetic recording and its implications for modulation and error correcting are presented.
Abstract: In this paper we present a combined modulation/error correcting trellis code suitable for magnetic recording. This R = 4/8, (b,l) =
16 citations
Patent•
10 Sep 1986
TL;DR: In this paper, the error syndrome bit of the error corrector is used in establishing phase and timing synchronization by causing the receiver to try all possible combinations of phase, and to lock onto the combination which produces a minimum of error syndrome bits.
Abstract: Error multiplication in the differential decoder and descrambler of V.22 bis modems is avoided by replacing the differential coding with forward error correction and single symbol coding. The error syndrome bit of the error corrector is used in establishing phase and timing synchronization by causing the receiver to try all possible combinations of phase and timing, and to lock onto the combination which produces a minimum of error syndrome bits. The descrambler receives the error-free corrected bit stream, whereby the descrambler's inherent error multiplication becomes moot.
14 citations
20 May 1986
TL;DR: Overall, the results indicate that by using ARQ, a reliable telegraphy service via satellite can be established not only in open areas but also in cities.
Abstract: The fading behaviour of the land mobile satellite channel has been recorded in different environments. The recordings are used as a basis for the simulation of data transmission schemes with ARQ. The influence of the main system parameters on the throughput of data transmission schemes with automatic repeat request (ARQ) is evaluated and discussed. There exist optimum values for the code rate of the data blocks, for the signalling rate, and for the data blocklength. Compared to ARQ schemes with pure error detection hybrid ARQ schemes with error correction are superior with respect to achieveable information rate and are able to work at lower link power. Overall, the results indicate that by using ARQ, a reliable telegraphy service via satellite can be established not only in open areas but also in cities.
11 citations
01 Oct 1986
TL;DR: In this article, a Reed-Solomon error correction codec was developed and integrated into a satellite TDMA system, where the coding overhead was only about 6%, and a dramatic error rate improvement was achieved for channel error rates less than 5×10-4.
Abstract: In a recent experimental project, a long, high rate Reed-Solomon error correction codec was developed and integrated into a satellite TDMA system. Although the coding overhead was only about 6%, a dramatic error rate improvement was achieved for channel error rates less than 5×10-4. This paper describes the design and implementation of the codec, its integration into a TDMA format, and the results of the experimental testing.
10 citations
TL;DR: In this paper, an effective method for combatting this phenomenon in TDMA systems is described, based on the application of additional FEC coding protection on a dynamic basis to faded traffic terminals.
Abstract: A major concern in satellite communications systems operating at frequencies above 10 GHz (e.g. Ku band) is the performance degradation caused by rain fading. In this paper, an effective method for combatting this phenomenon in TDMA systems is described. This method is based on the application of additional FEC coding protection on a dynamic basis to faded traffic terminals. Selective (adaptive) forward error correction (S-FEC) coding permits the fixed fade margins used by the network earth-stations to be substantially reduced, while a desired outage probability is maintained. This paper deals primarily with the implementation of the monitoring and control subsystems required in a practical S-FEC network.
7 citations
04 Apr 1986
TL;DR: It is shown how the Viterbi algorithm and the Fast Fourier Transform can be described in terms of the same graph topology and different algebraic kernels, and the modularity of this approach allows the decoding of large constraint length codes with multi-chip VLSI systems operating at different degrees of parallelism.
Abstract: It is shown how the Viterbi algorithm and the Fast Fourier Transform can be described in terms ofthe same graph topology and different algebraic kernels. This similarity is exploited to show how a net- work of 2" processors, interconnected as an n- dimensional cube and with no shared memory, can beefficiently used to implement a concurrent Viterbi algorithm. The modularity of this approach allowsthe decoding of large constraint length codes with multi -chip VLSI systems operating at different degrees of parallelism. The interprocessor communication overhead is minimized by using the trace -back method, which completely avoids any survivor exchange or any global memory operation. Resultsare presented on the efficiency achieved for codes with constraint length up to 15 on a general purposehypercube computer, and comparisons are made with other parallel architectures. 1. Introduction Convolutional codes, combined with the Viterbi decoding algorithm 1, are among the most power-ful techniques to reduce the effect of random errors in digital communication systems.
6 citations
15 May 1986
TL;DR: The alternative detection strategies for optical communication with pulse position modulation (PPM) are analyzed and compared both for systems with and without error correcting codes, as well as if no error encoding is used.
Abstract: The alternative detection strategies for optical communication with pulse position modulation (PPM) are analyzed and compared both for systems with and without error correcting codes. If no error encoding is used, the detection alternatives include the threshold and maximum count M-ary strategies, as well as a method of bit decoding on parallel binary channels. M-ary maximum count offers the best performance as it is a maximum-a-posteriori (MAP) strategy, but threshold may be much easier to implement at high data rates. For the particular choice of metric analyzed, the binary scheme is competitive only for low values of PPM word size. For PPM communication with error correcting codes, the decoder has the additional option for hard or soft decisioning. Each of the unencoded detection schemes can interface directly with a hard decision decoder. The hard decision coding performance can be characterized in terms of input/output bit error probability for a given code. Coding gain is defined to reflect the optical power savings by incorporating the code, and example hard decision coding gains are evaluated for M-ary Reed-Solomon and binary BCH codes with an APD receiver. Soft decision decoder performance is dependent on both the input error and erasure probabilities from the channel. Soft decisions strategies offer additional coding gain, and the performance of rate 1/2 Reed-Solomon codes is compared for A-Max and threshold soft decision strategies with an APD receiver.
6 citations
01 Oct 1986
TL;DR: A new modem for Frequency Division Multiple Access (FDMA) satellite communications is presented, which utilizes a number of unique implementation approaches that result in exceptional performance and flexibility with low cost and power consumption.
Abstract: A new modem for Frequency Division Multiple Access (FDMA) satellite communications is presented The modem utilizes a number of unique implementation approaches that result in exceptional performance and flexibility with low cost and power consumption Very close channel spacings allowed by the modem result in greater bandwidth efficiency, and integral forward error correction (FEC) coding provides low bit error rates (BER) even in systems limited in satellite power
20 May 1986
TL;DR: This paper presents some of such analyses with reference to a 900 MHz band mobile radio system in urban environment, using a narrowband modulation technique of the class 12PM3, with frequency discriminator detection.
Abstract: In digital mobile radio systems the transmission errors caused by multipath fading are bursty Therefore, to design and evaluate the performance of forward error-correction (FEC) techniques, the statistical characteristics of the error patterns must be analyzed This paper presents some of such analyses with reference to a 900 MHz band mobile radio system in urban environment, using a narrowband modulation technique of the class 12PM3, with frequency discriminator detection The regeneration is performed by either a simple hard decision technique or a maximum likelihood sequence estimation (MLSE) technique The transmission error statistics are presented according to two different definitions
01 Oct 1986
TL;DR: A new approach to mitigate the effects of interference is derived that modifies conventional interleaving, detects and deletes burst errors, and corrects random errors.
Abstract: Based on the fact that performance of random error correction decoding is insensitive to code symbols erased before its decoding process, a new approach to mitigate the effects of interference is derived. This approach consists of three basic functions: it modifies conventional interleaving, it detects and deletes burst errors, and it corrects random errors. Therefore, this approach minimizes effects of jamming, antenna switching, and nuclear fading. We shall first describe a tactic of integrating coding and interleaving. Then, derivation and application of a special rate-1/4 convolutional code are illustrated. Finally, some preliminary computer simulation results on a rate-1/2 code are utilized to verify the effectiveness of the proposed technique.
01 Oct 1986
TL;DR: It is shown that a combination of Time Division Duplexing, frequency hopping, forward error correction coding, CPFSK modulation, and synchronized transmission will provide a non-interfering solution.
Abstract: Tactial Multichannel Communication Systems of the 1990's will require the use of secure spread spectrum techniques. The use of ECCM techniques entails that the communication system be designed from a network point of view, to insure non-interfering operation. Spread spectrum transmission is examined in light of interference reduction techniques both from a network and a co-location point of view. It is shown that a combination of Time Division Duplexing, frequency hopping, forward error correction coding, CPFSK modulation, and synchronized transmission will provide a non-interfering solution. The use of automated frequency management, hosted on a personal computer, enhances the performance of this system especially when the frequency allocation is limited or the network topology is not a mesh. This work was performed on an internal research project for the Canadian Marconi Company.