Impact of Signaling Constraints on the MAC Level Performance of OFDMA Systems

Frequency adaptive scheduling in OFDMA systems requires accurate channel state information at the transmitter. In this paper we investigate the performance degradation in the downlink of a WiMAX based OFDMA system under the assumption of signaling constraints in the uplink. The active mobile terminals are not allowed to transmit the channel state information of all available subchannels to the associated base station but only a subset which is defined by a maximum number of subchannels. The impact of this constraint on the system behavior is discussed with the help of simulative performance evaluations. These are mainly focused on the interaction between physical layer and medium access control and therefore provide specific insight into the characteristics of broadband OFDMA systems.