Degrees of freedom in adaptive modulation: a unified view

We examine adaptive modulation schemes for flat-fading channels where the data rate, transmit power, and instantaneous BER are varied to maximize spectral efficiency, subject to an average power and BER constraint. Both continuous-rate and discrete-rate adaptation are considered, as well as average and instantaneous BER constraints. We find the general form of power, BER and data rate adaptation that maximizes spectral efficiency for a large class of modulation techniques and fading distributions. The optimal adaptation of these parameters is to increase the power and data rate and decrease the BER as the channel quality improves. Surprisingly, little spectral efficiency is lost when the power or rate is constrained to be constant. Hence, the spectral efficiency of adaptive modulation is relatively insensitive to which degrees of freedom are adapted.

[1]  Shlomo Shamai,et al.  On the capacity of some channels with channel state information , 1999, IEEE Trans. Inf. Theory.

[2]  Norihiko Morinaga,et al.  Adaptive modulation system with variable coding rate concatenated code for high quality multi-media communication systems , 1996, Proceedings of Vehicular Technology Conference - VTC.

[3]  Pil Lee.  Computation of the Bit Error Rate of Coherent M-ary PSK with Gray Code Bit Mapping , 1986, IEEE Trans. Commun..

[4]  Andrea J. Goldsmith,et al.  Variable-rate variable-power MQAM for fading channels , 1997, IEEE Trans. Commun..

[5]  Dennis Goeckel,et al.  On power adaptation in adaptive signaling systems , 2000, IEEE Trans. Commun..

[6]  A. Goldsmith,et al.  Variable-rate variable-power MQAM for fading channels , 1996, Proceedings of Vehicular Technology Conference - VTC.

[7]  William H. Press,et al.  Numerical Recipes in C, 2nd Edition , 1992 .

[8]  W. T. Webb,et al.  Variable rate QAM for mobile radio , 1995, IEEE Trans. Commun..

[9]  Dennis L. Goeckel,et al.  Robust adaptive coded modulation for time-varying channels with delayed feedback , 1997 .

[10]  Andrea J. Goldsmith,et al.  Effect of average power estimation error on adaptive MQAM modulation , 1997, Proceedings of ICC'97 - International Conference on Communications.

[11]  Andrea J. Goldsmith,et al.  Adaptive coded modulation for fading channels , 1997, Proceedings of ICC'97 - International Conference on Communications.

[12]  J. Cavers,et al.  Variable-Rate Transmission for Rayleigh Fading Channels , 1972, IEEE Trans. Commun..

[13]  Dennis Goeckel,et al.  Adaptive coding for time-varying channels using outdated fading estimates , 1999, IEEE Trans. Commun..

[14]  William H. Press,et al.  Numerical recipes in C , 2002 .

[15]  Stephen Wolfram,et al.  The Mathematica Book , 1996 .

[16]  N. Morinaga,et al.  Symbol rate and modulation level controlled adaptive modulation/TDMA/TDD for personal communication systems , 1995, 1995 IEEE 45th Vehicular Technology Conference. Countdown to the Wireless Twenty-First Century.

[17]  Pravin Varaiya,et al.  Capacity of fading channels with channel side information , 1997, IEEE Trans. Inf. Theory.

[18]  Andrea J. Goldsmith,et al.  Adaptive coded modulation for fading channels , 1998, IEEE Trans. Commun..

[19]  John G. Proakis,et al.  Digital Communications , 1983 .

[20]  Giuseppe Caire,et al.  Optimum power control over fading channels , 1999, IEEE Trans. Inf. Theory.