Abstract:Abstract This chapter presents both tutorial information and practical design data on the application of forward error correction (FEC) techniques. FEC may only be used with digital circuits. Forward ...Abstract This chapter presents both tutorial information and practical design data on the application of forward error correction (FEC) techniques. FEC may only be used with digital circuits. Forward error correction can be used to improve bit error performance on a marginal circuit or to lower E b / N 0 requirements without impacting error performance on other digital circuits. The armed forces of the world were probably the first to put FEC to work. It now has universal acceptance in the commercial world. Where good bit error performance is crucial, one can expect to find FEC applied. This is particularly true on digital compression schemes such as motion picture experts group (MPEG). It is finding growing acceptance in the cellular/personal communication services (PCS) world and on line‐of‐sight (LOS) microwave and high‐frequency (HF) radio circuits. Coding gain is defined as the difference between required E b / N 0 for an objective target bit error rate (BER) between a certain coded system and the same system without coding. A radio system “gain” is traditionally achieved by increasing transmitter power, improving receiver sensitivity, applying diversity, and increasing antenna aperture. Now on digital systems, coding gain derived from FEC is still another method to achieve gain, usually at a fairly reasonable price, by the addition of a personal computer (PC) board at each end of a link. Coding gains of 2–5 (or more) dB are common. To improve coding gain still further, tandem coding can be employed. This is also called concatenated coding, where there is an inner code and an outer code. On one application, the outer code was a convolutional code with a coding gain of 5 dB, and the inner code was a Reed–Solomon block code with a coding gain of 2 dB. The net coding gain in this case was 7 dB. Conventional wisdom agrees that the redundancy added for FEC requires an appropriate bandwidth expansion. When trellis‐coded modulation (TCM) is used, this is not the case. TCM is particularly attractive on digital LOS microwave circuits, where conservation of bandwidth is so important.Read More
Publication Year: 2002
Publication Date: 2002-01-15
Language: en
Type: other
Indexed In: ['crossref']
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