Title :
Quantization loss in convolutional decoding
Author :
Onyszchuk, I.M. ; Cheung, K.-M. ; Collins, O.
Author_Institution :
Jet Propulsion Lab., Pasadena, CA, USA
fDate :
2/1/1993 12:00:00 AM
Abstract :
The loss in quantizing coded symbols in the additive white Gaussian noise (AWGN) channel with binary phase-shift keying (BPSK) or quadrature phase-shift keying (QPSK) modulation is discussed. A quantization scheme and branch metric calculation method are presented. For the uniformly quantized AWGN channel, cutoff rate is used to determine the step size and the smallest number of quantization bits needed for a given bit-signal-to-noise ratio (Eb/N0) loss. A nine-level quantizer is presented, along with 3-b branch metrics for a rate-1/2 code, which causes an Eb/N0 loss of only 0.14 dB. These results also apply to soft-decision decoding of block codes. A tight upper bound is derived for the range of path metrics in a Viterbi decoder. The calculations are verified by simulations of several convolutional codes, including the memory-14, rate-1/4 or -1/6 codes used by the big Viterbi decoders at JPL
Keywords :
convolutional codes; decoding; phase shift keying; telecommunication channels; white noise; 0.14 dB; AWGN channel; BPSK; Eb/N0 loss; QPSK; Viterbi decoder; additive white Gaussian noise; binary phase-shift keying; bit-signal-to-noise ratio; block codes; branch metric calculation; convolutional codes; convolutional decoding; cutoff rate; nine-level quantizer; quadrature phase-shift keying; quantisation loss; soft-decision decoding; step size; tight upper bound; AWGN; Additive white noise; Binary phase shift keying; Convolutional codes; Decoding; Phase modulation; Phase shift keying; Quadrature phase shift keying; Quantization; Viterbi algorithm;
Journal_Title :
Communications, IEEE Transactions on
