Average Transmit Power Constraint Research Articles

Channel capacity and error exponents of variable rate adaptive channel coding for Rayleigh fading channels

We have evaluated the information theoretical performance of variable rate adaptive channel coding for Rayleigh fading channels. The channel states are detected at the receiver and fed back to the transmitter by means of a noiseless feedback link. Based on the channel state informations, the transmitter can adjust the channel coding scheme accordingly. Coherent channel and arbitrary channel symbols with a fixed average transmitted power constraint are assumed. The channel capacity and the error exponent are evaluated and the optimal rate control rules are found for Rayleigh fading channels with feedback of channel states. It is shown that the variable rate scheme can only increase the channel error exponent. The effects of additional practical constraints and finite feedback delays are also considered. Finally, we compare the performance of the variable rate adaptive channel coding in high bandwidth-expansion systems (CDMA) and high bandwidth-efficiency systems (TDMA).

Rate and power adaptation in code division multipleaccess communications

The authors compare the average information rates attained by adapting the transmit power and the information rate in code division multiple access communication systems, subject to identical average transmit power constraints.

Joint optimization of transmitter and receiver filters in digital PAM systems with a Viterbi detector

Joint optimization of transmitter and receiver filters in a pulse-amplitude modulation (PALM) system with an arbitrary but fixed Viterbi detector is considered. Optimization is performed under an average transmitted power constraint with respect to a new criterion called the effective mean-square error (EMSE). It is shown that the optimization problem is convex. A necessary and sufficient condition for optimality is derived, and a method for optimization is proposed. Numerical results are obtained for a channel with coaxial cable characteristics.