Joint dynamic switching point configuration and resource allocation in TDD‐OFDMA networks: optimal formulation and suboptimal solution

Abstract

With the large increase in data services with asymmetric traffic loads, the time division duplexing (TDD) mode of operation of the next generation cellular wireless standards has gained an increasing interest from both cellular network operators and the research community. However, the introduction of TDD has raised several critical design requirements. Among others, the introduced flexibility in splitting resources between the uplink and downlink directions makes of the uplink/downlink switching point configuration a major design problem, especially that it is directly connected to other design aspects such as resource allocation and interference mitigation. In this paper, we formulate joint switching point configuration and resource allocation in TDD systems as an optimization problem with the objective of minimising the total interference under traffic load and other network constraints. The problem is then reformulated by linearizing some of the nonlinear terms. Because of the persistent difficulty of the problem, we propose a three-stage suboptimal algorithm. The algorithm clusters the cells in a given network into different groups depending on the susceptibility of cells to interfere on each other with emphasis on base station-base station and mobile station-mobile station interference. Switching point configuration using standardised long term evolution (LTE) frame structures and multicell resource allocation utilising uplink and downlink interference indicators are subsequently performed independently. Simulation results show the merits of the proposed approach compared with traditional techniques by offering attractive trade-offs between interference mitigation and traffic adaptation.