Optimal Centralized Dynamic-Time-Division-Duplex

The study of optimal properties of centralized dynamic-time-division-duplex (D-TDD) employed at a wireless network consisting of multiple nodes is a highly challenging and partially understood problem in the literature. In this paper, we develop an optimal centralized D-TDD scheme for a wireless network comprised of K full-duplex nodes impaired by self-interference and additive white Gaussian noise. As a special case, we also propose the optimal centralized D-TDD scheme when part or all nodes in the wireless network are half-duplex. Thereby, we derive the optimal adaptive scheduling of the reception, transmission, simultaneous reception and transmission, and silence at every node in the network in each time slot such that the rate region of the network is maximized. The performance of the optimal centralized D-TDD can serve as an upper-bound to any other TDD scheme, which is useful in qualifying the relative performance of TDD schemes. The numerical results show that the proposed centralized D-TDD scheme achieves significant rate gains over existing centralized D-TDD schemes.

I. Introduction

Time-division duplex (TDD) is a communication protocol where the receptions and transmissions to and from the network nodes are allocated to non-overlapping time slots in the same frequency band. TDD has wide use in 3G, 4G, and 5G and allows for an easy and scalable control over the flow of uplink and downlink traffic at the nodes. Typically, it is achieved by changing the portion of time slots allocated to reception and transmission at the nodes [2], [3].