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<p>The performance of a communication system having almost the same spectral efficiency as a trellis coded modulation  (TCM) system with r = 2/3 convolutional encoding and 8-ary phase-shift keying (8-PSK) modulation is investigated. TCM is  a common solution to the problem of adding forward error correction (FEC) coding without an attendant increase in channel  bandwidth. The primary drawback to TCM is that the achievable coding gain is limited by the maximum practical number of  states in the convolutional encoder. The alternative system considered uses (63, 37) Reed-Solomon (RS) encoding. The six-bit  symbols at the output of the Reed-Solomon encoder undergo serial-to-parallel conversion to two three-bit symbols, which are  then independently transmitted on the in-phase (I) and quadrature (Q) component of the carrier using 8-ary biorthogonal keying  (8-BOK). This system has a null-to-null bandwidth of 0.993Rb, which is 0.7% smaller than TCM with r = 2/3 convolutional  encoding and 8-PSK modulation. The two waveforms are compared for the relatively benign case where additive white  Gaussian noise (AWGN) is the only noise present as well as when pulse-noise interference (PNI) is present. It was found that  both systems have almost the same performance in AWGN, but with PNI the alternative system has better performance.
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<br>Subjects: Error-correcting codes (Information theory); Reed-Solomon codes; Digital communications</div>
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Marques, Mario Rui Monteiro</div>
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