Research On Frequency Reuse Techniques Of Futrue Mobile Communication Systems

Orthogonal frequency division multiple access (OFDMA) technology is one of key technologies in the3GPP LTE and subsequent technical standards. It can effectively suppress intra-cell interference because of the orthogonality of subcarriers. However, it also brings severe inter-cell interference as the bandwidth is reuse in each cell. In order to solve the problem, inter-cell interference coordination is applied in3GPP LTE. Frequency reuse is one way of interference coordination.On the basis of the future mobile communications, we investigate the frequency reuse technique. The thesis mainly focuses on the research of downlink frequency reuse schemes, including capacity maximization, energy efficiency analysis, etc. We also propose some optimization method and performance analysis of frequency reuse systems. The main research contents are summarized as follows:With demanded user Quality of Service constraints, we aim at maximizing the maximizing the downlink cell capacity and try to obtain the optimal fractional frequency reuse zone partitioning. We transform the maximum data rate of each user into a convex problem and obtain a low order function of the reuse radius. The results show the accuracy of the method. It can also be applied in the generally frequency reuse schemes, including soft fractional frequency reuse.With the explosive development of high-speed wireless communications service, energy consumption of the wireless devices including the base stations is increasing. Energy consumption of mobile communications is getting more attention from academic circles. Therefore, how to guarantee the users’quality of service and obtain the energy-efficient frequency reuse scheme is a new issue raised by the energy-efficient wireless communication network. Based on Dinkelbach’s theory and Karush-Kuhn-Tucker (KKT) conditions, we theoretically figure out the energy-efficienct fractional frequency reuse and soft frequency reuse schemes along with energy-efficient power control algorithms. The optimal frequency reuse factors are also given.Soft fractional frequency reuse (SFFR) is one of the Inter-cell interference coordination schemes. The frequency reuse fator of SFFR is much closer to one than FFR and SFR. The paper proposes a fuzzy set theory based generic mathematical model for deriving various SFFR schemes. The derived schemes are evaluated using various parameters such as average throughput, spectral and power efficiency. The simulation analysis provided in the paper discovers an optimal SFFR scheme. The optimal scheme, which frequency reuse factor is1.35, improves the power efficiency by staggering57%as compared to FR=3.