Inter-cell Interference Cooperation Algorithm Based On Soft Frequency Reuse In LTE System

With the traffic requirement of wide bandwidth,fast data rate,high quality and low delay,3GPP advanced the next communication system-Long Term Evolution Project.LTE uses OFDM technology and it suppresses interference within the cell well,but the inter-cell interference(ICI)caused by the same frequency network still exists and affects especially the cell edge user(CEU)performance.Suppressing ICI is one of the key ways to improve LTE system performance.Inter-cell interference coordination(ICIC)in LTE has become the focus of research,which can reduce ICI and improve the cell-edge performance effectively.Firstly,the background and development of ICIC are introduced.Then,the basic theoretical knowledge of LTE system is summarized.Then,the basic knowledge of ICIC in LTE system is discussed,and several typical ICIC schemes are introduced.The emphasis is on the schemes of different frequency reuse style Fractional Frequency Reuse(FFR),Soft Frequency Reuse(SFR)and Adaptive Frequency Reuse(AFFR).Aiming at the shortage of the traditional fixed power factor in ICIC scheme,an improvement is made based on the SFR scheme,and proposes the power factor updating algorithm.The proposed algorithm firstly establishes the optimization model of the system and prove the uniqueness of the solution.Then,the optimal power factor is solved by the Newton iterative method,and the power factor updating algorithm is derived.By dynamically adjusting the transmit power,thus maximizing the system throughput.The effectiveness of the proposed algorithm is verified by simulations.Semi-static schemes improved the cell-edge performance but limit the overall system performance.To resolve these shortcomings,a modified semi-static inter-cell interference coordination(M-ICIC)scheme was proposed.The frequency resource allocation model of the scheme is given firstly.In the frequency allocation of SFR scheme,the bandwidth is increased and the resource allocation can be adjusted with the load change.Based on this,the reuse resource avoidance algorithm based on high interference indicator(HII)is used to suppress the interference caused by reuse of resources among the cells.Based on the path loss,a closed loop power control method was applied when setting transmit power of cell-center users,and the power is adjusted according to the overload indication(0I)message in real time.Simulation results showed that,compared with SFR the efficient ICIC scheme can improve the cell-edge and overall system performance.