SHAN Xiao-hong (单晓红), ZHU Xiu-shan (朱秀珊), GUO Yin-jing (郭银景), LIU Zhi-wen (刘治文)
(College of Information and Electrical Engineering, Shandong University of Science and Technology, Qingdao 266510, China)
Abstract:An analysis process is described for adaptive quadrature amplitude modulation (AQAM) of constant-power constant-symbol-rate over frequency-selective Rayleigh fading channels with inter symbol interference (ISI) and Gaussian noise. The delay spread resistance of the AQAM scheme is put forward by studying its average throughput and average bit-error-rate (BER), both of which can be expressed as functions of two variables, the ratio of root mean square (RMS) delay spread to symbol period and the ratio of average symbol energy to noise. Average throughput reacts regularly to the latter, whereas it does not react to the former. The AQAM scheme is highly superior in the delay spread resistance in comparison with the fixed modulation modes. Gains of the AQAM scheme over the fixed modes become more significant as the delay spread becomes severer or the average throughput decreases.
Key words:time delay spread; adaptive modulation; adaptive quadrature amplitude modulation (AQAM)
CLD number: TN929.5 Document code: A
Article ID: 1674-8042(2012)02-0152-05 doi: 10.3969/j.issn.1674-8042.2012.02.011
References
[1] Falahati S, Svensson A, Ekman T, et al. Adaptive modulation systems for predicted wireless channels. IEEE Trans.on Communication, 2004, 52(2):307-316.
[2] Choi B J, Munster M, Yang L L, et al. Performance of rake receiver assisted adaptive-modulation based CDMA over frequency selective slow Rayleigh fading channels. Electronics Letters, 2001, 37(4):247-249.
[3] Kim J, Kim I, Ro S, et al. Effects of multipath diversity on adaptive QAM in frequency selective Rayleigh fading channels. IEEE Communications Letters, 2002,6(9): 364-366.
[4] Choi B, Hanzo L. Optimum mode-switching-assisted constant-power single- and multicarrier adaptive modulation. IEEE Trans. on Vehicular Technology, 2003,52(3):536-560.
[5] Fung V, Rappaport T S, Thoma B. Bit error simulation for /4 DQPSK mobile radio communications using Two-Ray and measurement-based impulse response models. IEEE Journal of Selection Areas Communication, 1993,11(3):393-405.
[6] Chuang J C-I. The effects of time delay spread on portable radio communications channels with digital modulation. IEEE Journal of Selection Areas Communications, 1987, 5(5): 879-889.
[7] Ue T, Sampei S, Morinaga N. Symbol rate and modulation level controlled adaptive modulation system with TDMA/TDD for high bit rate transmission in high delay spread environments. Electronics Letters, 1996, 32(4): 304-305.
[8] Rappaport T S. Wireless communications principles and practice, Prentice-Hall, 1996.
[9] Glance B, Greenstein L J. Frequency-selective fading effects in digital mobile radio with diversity combining. IEEE Trans. on Communications. 1983,31(9): 1085-1094.
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