Distributed DL/UL Asymmetry Synchronization for Adaptive-Tdd Wireless Access Networks
Kostas Ntagkounakis, P.I. Dallas, Bayan S. Sharif, Gregory S. Yovanof · 2006
Adaptive time division duplex (ATDD) systems have the ability to efficiently utilize the radio spectrum and achieve higher capacity, when the traffic conditions are time-varying within a cell or diverse among different cells. However, severe co-channel interference conditions can occur when the movable TDD boundary is not synchronized amongst all frames in the base stations, compromising the spectral efficiency and the system's robust operation. To reduce the interference outage probability, a distributed boundary synchronization (DBS) scheme is proposed that dynamically synchronizes the TDD boundaries amongst neighbouring sectors, thus avoiding sector-to-sector interference, whilst preserving the ATDD efficiency. Results show that DBS achieves an 8 dB improvement in the uplink SIR for the same interference outage, and a 27.5-60% increase in terms of capacity, subject to traffic asymmetry conditions. More importantly the proposed DBS scheme requires only simple modifications in the system