Determining of Threshold Levels of Burst by Burst AQAM/CDMA in Slow Rayleigh Fading Environments

Authors: F. Nejadebrahimi, M. ArdebiliPour

Abstract:

In this paper, we are going to determine the threshold levels of adaptive modulation in a burst by burst CDMA system by a suboptimum method so that the above method attempts to increase the average bit per symbol (BPS) rate of transceiver system by switching between the different modulation modes in variable channel condition. In this method, we choose the minimum values of average bit error rate (BER) and maximum values of average BPS on different values of average channel signal to noise ratio (SNR) and then calculate the relative threshold levels of them, so that when the instantaneous SNR increases, a higher order modulation be employed for increasing throughput and vise-versa when the instantaneous SNR decreases, a lower order modulation be employed for improvement of BER. In transmission step, by this adaptive modulation method, in according to comparison between obtained estimation of pilot symbols and a set of above suboptimum threshold levels, above system chooses one of states no transmission, BPSK, 4QAM and square 16QAM for modulation of data. The expected channel in this paper is a slow Rayleigh fading.

Keywords: AQAM, burst, BER, BPS, CDMA, threshold.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1076950

References:

[1] L. Hanzo, C. H. Wong, M. S Yee, John, "Adaptive Wireless Transceivers", Wiley & Sons, Ch.12, 2002.
[2] P. Cherriman, E. L. Kuan, and L .Hanzo, "Burst-by-Burst Adaptive Joint-Detection CDMA/H.263 Based Video Telephony", IEEE Transactions on Circuits and Systems for Video Technology Vol.12, No.5, May 2002.
[3] B. J. Choi, M. Munster, L. Yang and L. Hanzo, "Performance of Rake Receiver Assisted Adaptive Modulation Based CDMA over Frequency Selective Slow Rayleigh Fading Channels", Electronics Letters, Vol. 37, No. 4, February 2001.
[4] R. Steele and W. T. Webb, "Variable rate QAM for data transmission over Rayleigh fading channels," in Proc. IEEE Wireless'91, Calgary, Alberta, Canada, pp. 1-14, 1991.
[5] J.M. Torrance and L. Hanzo. , "Performance Upper Bound Of Adaptive QAM In Slow Rayleigh Fading Environments", ISPACS- 96 Singapore, PP 1653-1657, 26-28 Nov. 1996.