Adaptive Resource Allocation Algorithm For Multiuser OFDM System Based On Qos

1. InstructionOrthogonal frequency division multiplexing (OFDM) is a high efficiency modulation technique for removing interference, which can make full use of spectrum resource and remove multi-path delay spread efficiently. Its appearance creates a new way for finding new spectrum resource and improving frequency utilization ratio in mobile communication. Allocating information bits and transmit power adaptively to the users based on their channel gains is one of advantages for separating a real channel into several subchannels in OFDM system.Two classes of resource allocation schemes exist: fixed resource allocation and dynamic resource allocation. A fixed resource allocation scheme is not optimal because the scheme is fixed regardless of the current channel condition. On the other hand, dynamic resource allocation allocates a dimension adaptively to the users based on their channel gains. Due to the time-varying nature of the wireless channel, dynamic resource allocation makes full use of the multi-user diversity to achieve higher performance.Next generation wireless communication system is supposed to support the following types of services: basic and enhanced voice services, low data rate services, medium data rate services, high data rate services, multimedia services, and so on. The primary goal of the next generation wireless communication system is to satisfy users'request of high quality-of-service (QoS) because that heterogeneous services require different grade of quality-of-services (QoS). Due to the different services, different quality of services and the instantaneous channel information of the subchannel, it can dynamically allocate data bits and transmit power to optimize system performance, and to improve spectrum efficiency, make full use of the channel resources, so that the multi-user OFDM system can be a robust system with guaranteed QoS. That is far meaning and realistic.2. The improved adaptive resource allocation algorithm based on QoSIn order to satisfy users'request of high quality-of-service (QoS) and reduce the complexity of allocation algorithm, an adaptive resource allocation algorithm was proposed for multi-user OFDM system based on QoS. In this algorithm, VIP users and normal users separation based on the requirement of the data rate and bit error rate was conducted in which different power allocation algorithm was adopted to make MU-OFDM system be a quality service guaranteed system.In the algorithm, subcarrier and power allocation are carried out sequentially and a subcarrier allocation method based on QoS was derived. In the power allocation algorithm, VIP users adopt optimal power allocation algorithm with proportional fairness, which can guarantee proportional fairness among VIP users and satisfy the requirement of the users'data rate; normal users adopt suboptimal power allocation algorithm, which is known as equal power allocation algorithm, to reduce the overall algorithm complexity. The algorithm make MU-OFDM system be a quality of service guaranteed system for which can make sure that each VIP user achieve a required data rate and reduce the overall algorithm complexity.3. Simulation and conclusionIn this paper, VIP users and normal users separation was conducted in which different power allocation algorithm was adopted to combine the strongpoint of Shen Algorithm and Equal Algorithm into an adaptive resource allocation method with excellent performance and low complexity. Simulation results demonstrate that the proposed algorithm can ensure the performance for both VIP users and normal users, and can reduce the overall algorithm complexity.