Throughput Optimization Using Adaptive Techniques

We present a mathematical framework for maximization of single user throughput in a wireless channel using the symbol rate, the packet length, and the constellation size of MQAM modulation as optimization variables. The throughput is defined as the number of bits per second correctly received. Trade-offs between the throughput and the operation range are observed, and equations are derived for the optimal choice of the design variables. These parameters are SNR dependent and can be adapted dynamically in response to the mobility of a wireless data terminal. We also look at the joint optimization problem involving all the design parameters together. We find, however, that not all of the three parameters need to be adapted simultaneously: in the high SNR region the maximum throughput is obtained by adapting the packet length and the constellation size together, while in the low SNR region it is achieved by adapting the symbol rate so that the received SNR per symbol stays at some preferred value. We also examine the performance of adaptive FEC in the low SNR region. Finally, we give a characterization of the optimal triplet of parameter values as functions of received SNR in both AWGN and Rayleigh fading channels with some restrictions on the design parameters.