Dynamic time-division-duplex wireless local loop

There are many benefits in using time-division-duplex (TDD) instead of frequency division duplex (FDD) schemes in fixed wireless cellular systems. To name a few channel reciprocity for a single carrier frequency used on both up and down-link will allow easy access to channel state information, reduced complexity of RF design, much higher flexibility in handling dynamic traffic, simpler frequency plan, etc. However, there exists a serious limiting factor in using dynamic-TDD (D-TDD) in cellular systems. This is due to a steady interference on an up-link in any cell caused by down-link transmissions in other cells. Simulation results show in D-TDD cellular systems, performance is unacceptable, when an omni-directional antenna is used at base stations. Simulation results also suggest great potential for smart antennas in achieving substantial performance improvement in fixed D-TDD bandwidth-on-demand wireless systems