A Flexible 5G Wide Area Solution for TDD with Asymmetric Link Operation

A flexible multi-service 5G wide area (WA) solution for time division duplex (TDD) operation is outlined in this article. In particular, the associated frame design is in focus. Given the fundamental tradeoffs between capacity, coverage, latency, and reliability, a flexible solution that allows optimization on a per-link basis is proposed. The solution encompasses the possibility to schedule users with different transmission time intervals to best match their service requirements and radio conditions. Due to the large downlink/uplink transmission power imbalance for each link, asymmetric link operation is proposed, where users operate with different minimum transmission times for the two link directions. This is achieved by using a highly flexible asynchronous hybrid automatic repeat request (HARQ) scheme, as well as a novel solution with in-resource control channel signaling for the scheduling grants. Performance results for the proposed 5G WA TDD solution show clear benefits over current LTE, for example, reduced latency and more scalable control overhead to better support users with different QoS requirements.