Antenna-sector time-division multiple access for broadband indoorwireless systems

摘要

This paper investigates a hybrid space-time-division multiplenaccess (S-TDMA) for broadband indoor wireless systems using sectorednantennas. It is shown that portables which are located in differentnsectors of an indoor microcell may be able to reuse the same frequencynand the same time slot. However, this requires careful scheduling ofnpacket transmissions in order to avoid transmitting packets that wouldnjam each other during the same time slot. It is proposed that thenscheduling be performed in the base station, i.e., a central controlnarchitecture. The optimum scheduling algorithm, the one that maximizesnthe number of packets transmitted per frame, may be in the NP-completenclass of problems, so it cannot be solved in real time. Therefore, ansuboptimum algorithm, called the first fit algorithm (FFA), is proposednfor frame scheduling. It was found that the capacity gain achieved bynthe FFA is dependent on the capture threshold, which is defined as thenminimum signal-to-interference ratio required in order to achieve angiven packet error rate goal. The capture threshold depends on thenmodulation and coding schemes. This paper investigates the performancenof the FFA operating with multicarrier trellis-coded modulation. Annalternative multicarrier modulation is analyzed, and the FFA performancenis investigated when operating with the alternative and with thenconventional multicarrier through computer simulations based on measuredndata which were obtained with a sectorization level of ten (using tennantenna sectors in the base station). The simulations have shown thatnthe FFA can provide a large capacity gain when operating withnmulticarrier trellis-coded modulation and using differential detection.nFor example, while previous schemes can transmit only one packet at antime, the proposed scheme can transmit, on average, more than fournpackets per time slot in an open indoor location, or close to threenpackets per time slot in a closed indoor location with internal walls ofnconcrete blocks