Research On Adaptive Resource Allocation Algorithm For Multi-service OFDM System

Many researchers studied the resource allocation problem of multi-service OFDM system. They all allot resource to real-time service first, and then allot residual resource to non-real-time service. Thus, real-time service will preempt sub-carriers and reduce transmission rate. So, the resource allocation algorithm of multi-service IEEE802.16 OFDM system is researched in this paper. IEEE802.16 OFDM system can support wide band wireless multi-service access. Its features are that the data transfer rate is higher and the ability of anti multi-path is stronger, so it has the good application prospect. The adaptive allocation algorithm can be adopted to raise the frequency spectrum efficiency and satisfy the user quality of service. An adaptive resource allocation algorithm based on the IEEE802.16 OFDM system is proposed by this paper. Firstly, each subcarrier chooses one user of which intermediate value is biggest. Then the bit load algorithm of the single user can be introduced to determine the bit and power of each subcarrier. Finally the resources adjustment should be adopted according to the service priority. The simulation results show that transmission rate is higher than compared algorithm.In addition, all traditional resource allocation algorithms are realized on the physical layer, and the data of every user must be enough. In fact, the channel condition and the data requirement are changing. If the user's data buffer has not enough data, the waste of resource will be produced. The joint MAC-PHY layer resource allocation algorithm can improve this problem. The joint MAC-PHY layer resource allocation algorithm is studied in this paper. The triangle module operator is designed simply. In addition, its complexity is very low, and it has the strong timeliness. So it can be adopted by the scheduling process of the joint MAC-PHY layer resource allocation algorithm to coordinate the time delay with the fairness of rate. In this paper, the service model of multi-service OFDM system is analyzed briefly first. Then the membership functions of time delay and fairness of rate are established. According to this analysis, the MAC layer scheduling algorithm based on triangle module operator is proposed, and the PHY layer allocation algorithm is also designed. The simulation results of packet loss ratio, average waiting delay and rate show that this algorithm can meet the requirement of time delay and fairness of rate delay, raise the spectrum efficiency and improve the user quality of service.