On the Gain of Data Rate Control in OFDMA Systems

Unlike single carrier systems, the primitive allocation unit in OFDMA systems is a sub-channel that is a collection of pre-arranged sub-carriers, and these sub-channels can be divided into two groups depending on the sub-carrier locations-diversity sub-channel and AMC sub-channel. The former consists of scattered sub-carriers over entire band while the latter consists of clustered sub-carriers on specific frequency band. For the case of AMC sub-channels, we can achieve link level SNR gain due to the reduced channel selectivity as well as system level multi-user scheduling gain due to the increased degree of freedom in selecting frequency bands. This paper investigates the performance difference between these two sub-channel types, specifically in terms of average throughputs, cell edge data rate and service outage probability.