Research On Dynamical Resource Allocation Algorithms For OFDM Systems

Orthogonal Frequency Division Multiplexing(OFDM)is a promising technique with high spectral efficiency. It divides wireless channel into N orthogonal subchannels, then converts high speed serial bits stream to parallel and transmit through lower speed subchannels. So it can support high speed data service, and hasstrong capacity of combating with multipath interference. Simultaneously, OFDM can dynamically allocate system resources (such as bit, power, etc.) according to subchannel's fading and multipath delay characteristics, and every subcarrier can carry on self-adaptation modulation. Thus, it has much strong flexibility, and can not only improve the utilization efficiency of system resources, but also meet user's different capacity demands.The dynamic resource allocation for OFDM systems mainly includes adaptive power allocation, adaptive sub-channel allocation and adaptive bit loading. At first,the paper introduced the theory of OFDM systems, and made analysis and comparison for the algorithms of power allocation, bit allocation and self-adaptation modulation. Then we make sub-optimal algorithms ourselves and compare their complexities and performance with the optimal algorithm by the simulation. We can find that these algorithms have lower complexity than the optimal algorithm with the close performance at the same time. At last through comparing the advantages and disadvantages of these algorithms ,we have discuss the expansion of the algorthm , s application.