Efficient resource allocation scheme based on mobile speed and traffic type in OFDM systems

Abstract

The orthogonal frequency division multiplexing (OFDM) has been widely recognized as the useful means to increase the capacity of the wireless high speed communication systems and satisfy the quality of service (Qos) requirements of traffics. Nonetheless, the overhead in transmitting the results of resource allocation and the efficient scheduling method for multiple types of traffic have rarely been considered. In OFDM systems, subcarriers are allocated to users with the same subcarrier and bit allocation period (SBAP). The base station informs users of their allocated subcarriers and the number of bit assigned to each subcarriers. This subcarrier and bit assignment information (SBAI) increases the transmission overhead in downlink. In addition, to satisfy the Qos requirements of multiple types of traffic, different scheduling policy is required according to the types of traffic. An optimum SBAP is proposed based on the mobile speed for OFDM systems when mobile speed is constant. The SBAP of each user is determined such that the overall throughput including SBAI can be maximized. The performances of the proposed SBAP are obtained and compared when users have different mobile speeds. Simulation results show that the proposed scheme outperforms other resource allocation schemes by reducing the transmission overhead of SBAI. For time-varying mobile speed, an adaptive subcarrier reallocation period is proposed for VoIP packet in OFDMA system. The adaptive subcarrier reallocation scheme change the subcarrier allocation period (SAP) based on the variation of mobile speed. Simulation results show that the proposed scheme adaptively reduces the subcarrier assignment signaling in changing mobile speed, and increase VoIP capacity in IEEE 802.16e systems. For subcarrier allocation of mixed traffic types, the efficient scheduler suitable for multiple types of traffic is proposed. To efficiently allocate resource to multiple types of traffics and obtain more mul...