Research On Resource Allocation Technology In Multiuser OFDM System

The development of the communication technology of the wireless networksmakes people more convenient. Especially the rapidly development of mobilecommunication makes people feel the wireless network communication technologypowerful. The frequency band, which is one of the most important resources incommunication network became less and less. Consequently, how to allocate theresources effectively to meet people various business traffic demands is a problem ofcommunication wireless networks that calls for immediate solution. As a kind ofmulti-carriers, OFDM is a modulation technology with Anti-interference ability, and itcan save lots of frequency bands. Because of this, studying on the resource allocationproblem for Multiuser OFDM system is particularly crucial.Firstly, the OFDM system and its basic principle are researched seriously.IFFT/FFT of OFDM system is explained in detail; the Inter Symbol Interference will bereduced, if the Guard Interval inserts among OFDM symbols; the Inter-CarrierInterference will be reduced, if Cyclic Prefix inserts in front of the OFDM symbols andthe power of OFDM symbols is better. Communication channel is one of the mostimportant parts of OFDM system, the multipath fading channel and it’s characteristicare introduced seriously. At the same time, advantages and disadvantages of OFDMsystem are analyzed in this paper.Secondly, resource allocation for OFDM system is researched, including dynamicresource allocation and adaptive resource allocation technology. Meanwhile,simulations of the classical algorithms, including Water-filling algorithm andHughes-Hartogs gradient algorithm are completed by MATLAB. These algorithms areapplied to adaptive resource allocation of single user. Lagrangian Relaxation Algorithmand Two-Step subcarrier allocation algorithm are used for adaptive resource allocationof Multiuser. Based on those four algorithms, advantages and disadvantages areanalyzed.Finally, Margin Adaptive and Rate Adaptive these two resource allocation rules arediscussed. Linear algorithm and Genetic Algorithm are studied emphatically, based onthose two rules. Their complexity, performance, etc are showed by MATLABsimulation. A new optimization algorithm-Branch and Bound, which is used for the resourceallocation, is focused on and it explains its basic idea, designing process, etc. The mostimportant task is establishing the model to make it to be used in resource allocation ofMultiuser OFDM system, and comparing the performance, complexity with Linearalgorithm and Genetic Algorithm then giving its convergence features through theMATLAB simulation. The simulation results show that Branch and Bound optimizationalgorithm has better convergent features, lower complexity and better performance.Then taking user’s quality and equity into consideration, the Branch and Boundoptimization algorithm with the ratio fairness are put forward.This combining algorithmensures users’ fairness and satisfies their requirement of performance. All abovementioned can be proved by the MATLAB simulation.