A combined resource management and admission control scheme for optimizing uplink performance of M-WiMAX systems

Abstract

According to the AMC (Adaptive Modulation-Coding) mechanism of the M(obile)-WiMAX, the amount of data per modulation symbol depends on the perceived Signal-to-Noise Ratio, while, based on the OFDMA (Orthogonal Frequency Division Multiple Access) technique, each communication entails multiple concurrent transmissions. Therefore, in the uplink case, where each terminal has a maximum power limitation, the assignment of additional subcarriers does not always correspond to a proportional datarate increment, since the power dispersion over a larger set of symbols can cause the transition to a lower AMC level. In this framework, the present paper introduces a novel RRM (Radio Resource Management) algorithm that dynamically alters the number of subcarriers to be allocated to each connection so as to achieve spectrum saving via augmenting the bits per symbol ratio. Furthermore, in order to mitigate the extensive fluctuations imposed by the novel RRM scheme, an adequate minimum-complexity CAC (Connection Admission Control) scheme is proposed, which succeeds in accurately estimating the bandwidth requirements of the active flows by incorporating theoretical calculations along with a sampling process. It is proven analytically as well as through simulations that the new combined RRM-CAC strategy increases substantially the system capacity, without violating the Quality-of-Service guarantees.