Effect of traffic channel configuration on the orthogonal frequency division multiple access downlink performance

This paper studies traffic channel design tradeoffs for downlink orthogonal frequency division multiple access (OFDMA) systems. For fixed and portable users where the propagation channels are quasistatic, we show that the aggregated rate can be maximized by exploiting "multiuser diversity" through intelligent channel allocation. In this case, the traffic channel should be configured so that its corresponding achievable data rate has the highest variance among users. The capacity upper and lower bounds are derived to quantify the impact of different traffic channel configurations. For mobile services where multiuser diversity cannot be efficiently exploited due to the signaling overhead, we show that the system outage capacity is maximized when the traffic channels are configured with maximum frequency diversity. Using the results presented, designers of OFDMA system can determine the optimum traffic channel configuration based on the types of services supported by the network.