The Research On The Intercell Interference Coordination For Downlink OFDMA Wireless Cellular Networks

To support high-speed wireless multimedia applications for the next generation wireless cellular networks, such as long term evolution (LTE), orthogonal frequency division multiplexing access (OFDMA) is proposed as a promising multiple access scheme. In OFDMA cellular networks, intra-cell interference within a single cell is mostly eliminated due to the orthogonality of subcarriers. However, serious inter-cell interference (ICI) occurs when the frequency reuse factor equals to one in each cell, resulting in limiting the system capacity, and substantially degrading the performance of cell edge users (CEUs).In this thesis, we propose some inter-cell interference coordination schemes to suppress ICI in OFDMA cellular networks.First, we propose a dynamic fractional frequency reuse (DFFR) scheme, which is based on interference avoidance request (IAR) mechanism, to suppress the inter-cell interference (ICI) for downlink OFDMA cellular networks. The key idea of the proposed scheme is that base stations (BSs) exchange IAR messages among each other, and then dynamically control the transmit power according to their received IAR messages. For the elastic data traffic, we combine the IAR mechanism with proportional fairness (PF) scheduling algorithm, to achieve a good trade-off between the total cell throughput and the cell edge user (CEU) throughput. Extensive system level simulations show that the proposed DFFR scheme outperforms some reference frequency reuse schemes in terms of the total cell throughput, the CEU throughput, and the fairness among users. Furthermore, one of attractive advantages is that the proposed DFFR scheme requires no centralized controller and the exchanged information among BSs is minimized.Second, we consider the weighted sum throughput maximization (WSTM) problem to suppress ICI for downlink OFDMA cellular networks. The WSTM problem is a nonconvex combinatorial problem, and difficult to tackle in practice. Thus, we present and discuss three low-complexity suboptimal algorithms, which solve the WSTM problem via joint user scheduling and power control (USPC) among a set of coordinating cells. Extensive system level simulations show that all the proposed algorithms have close weighted sum throughput (WST) performances to that of exhaustive search (ES). Furthermore, the proposed distributed iterative (DI) algorithm, which enjoys both distributed operation and fast convergence, is the most attractive one in practical systems.