Asymmetry balancing in OFDMA-TDD cellular networks

The purpose of this paper is to compare two interference avoidance techniques for time division duplex (TDD) wireless networks, viz.: a novel technique termed asymmetry balancing and the known zone division (ZD) principle. Both asymmetry balancing and ZD strive to reduce the same-entity interference (mobile station (MS)-to-MS and base station (BS)-to-BS) that occurs during crossed slots, i.e. slots which are simultaneously used for uplink (UL) in one cell and for downlink (DL) in a neighbouring cell. Asymmetry balancing eliminates crossed slots by synchronising the TDD switching point (SP) among cells. Cell-specific asymmetry demands are still maintained through cooperation among the entities in the network. ZD, on the other hand, reduces same-entity interference by decreasing transmission range. This study demonstrates that asymmetry balancing achieves more than 100% higher spectral efficiencies than ZD for the considered scenarios.