Adaptive throughput optimization in downlink wireless ofdm system

Abstract

This paper presents a scheduling scheme for packet transmission in OFDM wireless system with adaptive techniques. The concept of efficient transmission capacity is introduced to make scheduling decisions based on channel conditions. We present a mathematical technique for determining the optimum transmission rate, packet size, Forward Error Correction and constellation size in wireless system that have multi-carriers for OFDM modulation in downlink transmission. 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. 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. Finally, we give a characterization of the optimal parameter values as functions of received SNR Simulation results are given to demonstrate efficiency of the scheme.