Dynamic UL/DL Mode Selection and Resource Allocation in Multi-Cell MIMO TDD Systems

This paper considers joint uplink/downlink mode selection and resource allocation problem in multi-cell systems for flexible TDD frame structures. To combat the difficult interference characteristics of such systems, a dynamic mode selection and resource allocation scheme is derived using Lyapunov optimization. The result is a cross-layer optimization scheme, where a long-term time-average utility function of flow rates and interference penalty is optimized by solving a series of instantaneous subproblems. The proposed dynamic algorithm provides a solution for the UL/DL mode selection and resource allocation, guided by the accumulating network layer queues and virtual queues. Furthermore, a heuristic method is considered to decouple the difficult power constraint in the resource allocation subproblem.