Flexible duplex in FDD spectrum

Abstract

In this paper, flexible frequency division duplex (FDD) and time division duplex (TDD) schemes are considered in FDD spectrum. With FDD spectrum, there is a paired uplink (UL) carrier with each downlink (DL) carrier, each carrier with the same bandwidth. Because equal resources are provisioned for the DL and UL, FDD spectrum is not well suited for asymmetric DL/UL traffic. While the FDD UL-paired carrier typically supports only UL traffic, flexible duplexing allows DL traffic to additionally be served in instances when the DL traffic exceeds the UL traffic. The challenge in such cases is to overcome the base station to base station interference that arises, particularly because base stations typically operate at higher powers and employ higher gain antennas than mobile stations. If ignored, this interference may overwhelm the power received for UL transmissions at neighboring base stations and impact UL performance. In this paper, we investigate flexible duplexing paired with power control and network-based interference cancellation to provide DL and UL resources that are matched to the ratio of their respective traffic, with minimal impact to the scaled UL throughput.