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Further Results on Selection Combining of Binary NCFSK Signals in Rayleigh Fading Channels

Annavajjala, R and Chockalingam, A and Milstein, LB (2004) Further Results on Selection Combining of Binary NCFSK Signals in Rayleigh Fading Channels. In: IEEE Transactions On Communications, 52 (6). pp. 939-952.

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Official URL: http://ieeexplore.ieee.org/iel5/26/29006/01306619....


In this paper, we provide an analytical performance comparison of various selection combining (SC) schemes for binary noncoherent frequency-shift keying (NCFSK) signals operating on independent and nonidentically distributed (i.n.d.) Rayleigh fading channels. With this motivation, we first derive the receiver structure for the optimum SC scheme, which combines one out of the available L diversity branches so as to minimize the probability of bit error. We show that the optimum SC scheme chooses the diversity branch having the largest magnitude of the logarithm of the a posteriori probability ratio (LAPPR) of the transmitted information bit. We also show that: 1) the optimum noncoherent diversity receiver, for binary NCFSK signals, is equivalent to combining the LAPPRs of all the diversity branches; 2) the SC scheme proposed by Neasmith and Beaulieu is a special case of the optimum SC scheme for independent and identically distributed (i.i.d.) Rayleigh fading; and 3) for i.n.d. fading with dual diversity (i.e., L = 2), the performance of the optimum SC scheme is the same as that of the optimum noncoherent diversity receiver, whereas the Neasmith and Beaulieu SC scheme gives the performance of the suboptimum equal gain combining receiver. Bit-error rate (BER) results show that, at 10(-4) BER, for i.i.d. Rayleigh fading, the proposed optimum SC scheme performs better than the existing SC schemes by 0.5-0.9 dB for L = 3 and by 0.8-1.5 dB for L = 5, and performs within 0.3 dB of the optimum noncoherent diversity receiver for L = 3, 5, and for i.n.d. Rayleigh fading with L = 5, the optimum SC scheme gives an additional gain of about 2.0 dB over the Pierce SC scheme. Further, for i.i.d. Rayleigh fading, we derive the bit-error probability expression for a (3, L) selection scheme which combines three branches whose LAPPR magnitudes are the largest among the available L branches Numerical results for this (3, L) selection scheme show that for L = 5 at a BER of 10-4, combining the three branches with the largest LAPPR magnitudes yields almost the full performance of the optimum noncoherent diversity receiver, whereas, for L = 7 it is just about 0.2 dB away from the latter.

Item Type: Journal Article
Publication: IEEE Transactions On Communications
Publisher: IEEE
Additional Information: Copyright of this article belongs to IEEE "YEAR IEEE. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Raman Research Institute's's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org. By choosing to view this document, you agree to all provisions of the copyright laws protecting it."
Keywords: Fading channels;noncoherent frequency-shift keying (NCFSK);optimum combining;selection diversity.
Department/Centre: Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited: 19 Dec 2008 04:08
Last Modified: 19 Dec 2008 04:08
URI: http://eprints.iisc.ac.in/id/eprint/16967

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