Interference Avoidance Based On Game Theory For Downlink Of OFDM System

With the wide application of OFDM systems,3G network have already stepped into people’s life, the research and development of 4G has also been made great progress. So the inter-carrier interference (ICI), which is inherent in OFDM systems, becomes the focus of research. Currently main methods of ICI suppression are 3 kinds:Frequency domain equalization, this method can effectively eliminate the signal distortion caused by ICI. Disadvantages are compute complex and realize difficult.Time domain equalization, this method can suppress the ICI caused by the Doppler frequency. By using this method, the designed filter is effective to suppress the ICI. Unfortunately, it needs to know channel’s information. Moreover, it needs to calculate the inverse matrix, the complex operation.ICI self-cancellation, this method does not need to pay extra spending, but it greatly reduces bandwidth and efficiency of the system.Based on the detailed analysis of the cause of subcarrier inter-carrier interference, we give proofs, simulations and verifications of the ICI suppression caused by phase noise. Game theory possesses the advantage of global optimization. This advantage is especially remarkable in the case of a variety of influence factors existence, so this paper chooses non-cooperative game theory to optimize the transmission power of the base stations. In the optimization we take into account the subcarrier inter-carrier interference caused by phase noise, the cost of the power choice and so on. The optimization will be operated until every user cannot change its parameters to make itself performance better, called the Nash equilibrium of the game theory. The proposed ICI suppression algorithm introduces the price mechanism and designs the cost function. The cost function considers not only the user’s power, but also the network environment, namely the subcarrier interference between different users. This makes the whole system more justice, and improves the efficiency of the system.Finally the OFDM power allocation software is designed. The software can get users random distribution, base station distribution, the distance between users and the base station, system throughput, the relationship between the distance and the throughput mentioned above, the system utility function and ICI variation and so on. From the results of the software, when the inter-carrier interference is larger, the user power varies smaller and vise verse. It reduces the channel overlap between users, thus suppresses the inter-carrier interference.