Inter Cell Interference Management For WiMAX System

WiMAX(Worldwide Interoperability for Microwave Access)is a wireless broad-band access technology based on IEEE 802.16e protocol. It can be well implemented in fixed or mobile circumstances, satisfying different QoS requirements in multi-services, such as data, voice, video, etc. Because of the features of mobile, wide-band, and IP-base, WiMAX is rapidly developed in recent years, and becomes a hotspot in wireless wide-band access technologies.OFDM system assures the orthogonality of subcarriers in the one cell, but do not promise the orthogonality of subcarriers in the all cells. Therefore, subcarriers face serious interference from the subcarriers of the adjacent cells in the same frequency. Inter-cell interference may substantially degrade the performance and capacity of the system. This paper focuses on how to reduce the inter-cell interference for WiMAX system .The origin of inter-cell interference is introduced firstly. And an analysis of several inter-cell interference mitigation strategies that can be used in the new telecommunication systems is provided. After comparison, Fractional Frequency Reuse (FFR) scheme is proposed to manage the inter-cell interference in downlink. A detailed analysis of FFR's principle, technical problems and solutions is provided in the paper. Then, a static downlink FFR scheme is designed for WiMAX system and evaluated through simulations.In the proposed FFR scheme, the whole spectrum is divided into several sub-sets. The users in the centre of the cell can use the all the bandwidth and should be serviced with low transmit power; the users at the edge of the cell should use the frequency resources which assure the orthogonality between the adjacent cells. And edge users should be serviced with high transmit power to ensure the stability of the connection and capacity. The simulation results show that the static downlink FFR scheme can reduce the inter-cell interference, and improve the performance of the edge users.