Dynamic time division duplex and time slot allocation strategy for multimedia traffic in wireless applications

This thesis deals with dynamic time division duplex (D-TDD) operation and time slot allocation (TSA) strategy for dynamic traffic pattern in fixed wireless applications.; We develop an analytic model of signal-to-interference ratio (SIR) distribution in D-TDD systems. Using the analytic model, we show that the probability density function (PDF) of SIR distribution in D-TDD system has two peaks, while that in conventional static time division duplex (S-TDD) systems has one peak. From the investigation of PDF, we show how the strong co-channel interference severely degrades the performance of SIR outage probability in D-TDD systems, when omni-directional antennas are employed at base station (BS) sites and subscriber (SC) sites. Also, we estimate the spatial resolution in terms of antenna beamwidth to obtain the target outage probability, when a spatial filter is employed at BSs. Numerical results show that 3.4-degree beamwidth is required to obtain an outage probability of 1% at the threshold SIR value of 17 dB.; To suppress the effect of strong co-channel interference in D-TDD systems, we develop a time slot allocation strategy (TSA), exploiting spatially distributed SCs' location over the cell coverage, combined with cost effective sector antenna layouts. We propose two TSA algorithms: the MaxMin {lcub}SIR{rcub} and the Max {lcub}SIR{rcub} algorithms. Our simulation shows that the performance of D-TDD system employing TSA, combined with 15 sector antennas, is comparable that employing adaptive array antennas with 26 sensing elements.; Finally, we compare the spectral efficiency of TDD systems for various frame-loading conditions. In the analysis, we consider two types of modulation schemes: fixed modulation and adaptive modulation. Fixed modulation is suitable for the delay-sensitive traffic, while adaptive modulation is proper for the delay-tolerant traffic, since the transmission rate in delay-tolerant traffic can be reduced and the data bits can be buffered, until the channel quality is improved. In fixed modulation system, it is observed that the spectral efficiency of D-TDD systems can be improved significantly by employing TSA strategy. For instance, as much as 9 times higher spectral efficiency is obtained by employing TSA strategy, when the traffic is highly dynamic and the frame is fully loaded. Meanwhile, in adaptive modulation system, the spectral efficiency of D-TDD systems does not improve significantly by employing TSA strategy. (Abstract shortened by UMI.)...