Abstract
This paper investigates a new multiple access system for broadband indoor wireless communications based on sectored antennas. Unlike previous sectored antenna indoor systems, this system incorporates the capability of reusing spectrum in different antenna sectors of the base station. It is shown that portable terminals located in different sectors of the indoor microcell may transmit/receive simultaneous data packets on the same frequency if their mutual interference is below a threshold level (or capture threshold) that guarantees an acceptable packet error rate. However, this requires careful scheduling of packet transmissions in order to avoid transmitting packets that would jam each other during the same time slot. When trying to transmit more than two packets per time slot, the optimum scheduling problem, the one that maximizes the number of packets transmitted per frame, is in the NP-complete class of problems, so it can not be solved in real time. Therefore, a sub-optimum algorithm named First Fit Algorighm is proposed for the frame scheduling problem. The problem is investigated experimentally for a sectorization level of ten (using ten antenna sectors in the base station). A statistical model of multipath propagation is used to extend the results to other levels of sectorization. The proposed system can significantly increase capacity when compared with systems that can transmit a single data packet per time slot. For example, while previous systems can transmit only one packet at a time, the proposed system can transmit on average close to three packets per time slot when operating with a capture threshold of 10 dB and ten antenna sectors in a closed indoor location with internal walls of concrete blocks.
Highlights
Sectored Antennas have been used for some time in mobile cellular systems as a means of reducing interference and con sequently increasing system capacity
In [3], a new multiple-access scheme is proposed to achieve in-cell frequency reuse by allowing simultaneous transmissions over different antenna sectors. This new Revista da Sociedade Brasileira de Telecomunicac;6es Volume 12, numero 2, dezembro 1997 multiple-access scheme requires a multi-port sectored an tenna system as the one illustrated in Figure l-b, which rep resents the same set of antennas as in Figure I-a but with a switch matrix capable of simultaneously selecting two anten nas and connecting each to a desired port that is connected to a transceiver
In the up-link case, the base station receives, through an tenna sector 5, the signal transmitted by P j at an average power level of 0 dBm and interference of -100 dBm from the reflected signal transmitted by P2, yielding an Signal-to-Interference Ra tio (SIR) of 100 dB for the P j transmitted signal
Summary
Sectored Antennas have been used for some time in mobile cellular systems as a means of reducing interference and con sequently increasing system capacity. In [3], a new multiple-access scheme is proposed to achieve in-cell frequency reuse by allowing simultaneous transmissions over different antenna sectors. This new Revista da Sociedade Brasileira de Telecomunicac;6es Volume 12, numero 2, dezembro 1997 multiple-access scheme requires a multi-port sectored an tenna system as the one illustrated in Figure l-b, which rep resents the same set of antennas as in Figure I-a but with a switch matrix capable of simultaneously selecting two anten nas and connecting each to a desired port that is connected to a transceiver. In this paper we use statistical modeling of indoor multipath propagation in order to investigate the per formance of the multiple access proposed in [3] when operat ing with different levels of sectorization
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
