An Efficient Quasi-dynamic Fractional Frequency Reuse Scheme For LTE System

System capacity is always a key indicator of the performance of a wireless communication system. The co-channel networking scheme with reuse factor 1 could make maximum use of the scarcely available radio resource and increase system capacity. However, in this case, strong interference coming from either the neighboring cell or neighboring sector would immensely deteriorate the serving quality of the cell-edge users. In this regard, interference randomization, interference cancellation and Fractional Frequency Reuse (FFR) are all popular solutions. However, FFR enjoys much higher gain compared with interference randomization and has much lower cost and complexity compared with interference cancellation. Thus, FFR is an efficient and effective solution to boost both the system capacity and cell-edge users'serving quality for the next-generation wireless communication system, and has been adopted by both LTE and WIMAX standards bodies. Therefore, FFR is our focus in the thesis.FFR could be classified into three categories:static FFR, dynamic FFR and quasi-dynamic FFR. Among them, dynamic FFR suffers much higher cost and complexity, while the performance of static FFR is far from optimum. Quasi-dynamic FFR has its gain-cost tradeoff advantage, and receives great attention to enhance the performance of static FFR. In the thesis, a new quasi-dynamic FFR algorithm is put forward for LTE system. Its key ideas are:(1) from the system optimization point of view, each user should have certain best suitable reuse pattern; (2) the reuse pattern with reuse factor 1 is close to optimal solution for center users who enjoy high SINR, thus research focus should be on the edge-users; (3) refining the reuse pattern of cell-edge users according to their different major interferers could improve their SINR without changing the reuse factor; (4) interference avoidance is applied for the protected users to improve their SINR considerably; (5) inter-reuse pattern-handover algorithm is designed to ensure each user choose their best suitable reuse pattern. Analysis shows that major overhead of this.scheme comes from the determination of the type of edge users.Simulation is done at an LTE system-level simulator. It is shown that the proposed scheme has considerably improved both the cell average spectrum efficiency and cell-edge users'spectrum efficiency, and the number of protected users is significantly reduced. Additionally, simulation result shows that the proposed scheme is quite suitable for suburban macro-cell scenario as well as rural macro-cell scenario with desirable gains.