An Operation Scheme for T Hroughput Maximization and Fairness in CDMA Cellular Systems with AMC

In this paper, the throughput maximization and fairness problems in the downlink of a sectored CDMA cellular system with AMC techniques are studied. We focus on maximizing the data rate for users on the cell border. An optimum data transmission with power control allocates the maximum allowable rate to only one user with the highest SINR. However, this throughput maximization rate allocation strategy causes high unfairness. On the other hand, if more service time or slots are assigned to the lower SINR users for fairness, system throughput will be decreased. Thus, we propose the operation of the system in a four time interval duty cycle that increases system throughput and fairness at the same time. In the first interval, users close to the base stations are served, one at a time in every sector. In the rest of the time intervals, for users close to the cell border, an On-Off Synchronous sectored operation is achieved. In this operation only one sector of each cell is allowed to transmit per each interval to only one user. Optimum durations of the time intervals are obtained. The results show that the average data rate at the cell border is increased 75% and the average data rate over the sector area is increased 9.7% relative to the traditional one-by-one transmission in each sector.