Media Access Protocols for use with Smart Array Antennas to Enable Wireless Multimedia Applications
Support of multimedia connectivity, packet access and bandwidth upon demand are essential features of future global communication networks. The core wireline network has evolved towards providing these broadband services. The increasing demand for mobile information access as well as the opportunity to deliver residential broadband service via wireless local loop necessitate the extension of these services to the wireless domain. Combating the time-varying impairments typical of a wireless channel is essential for extending the broadband wireline capability to wireless access systems. Usage of an adaptive array of spatially diverse antenna elements at each base station of a wireless network provides immunity to the effects of multipath fading and co-channel interference, thereby enabling high speed radio access. In this paper we describe three media access control (MAC) protocols which enable the deployment of such an array at the base station. These MAC protocols, by using polling, invoke a pilot tone from each remote user as needed, to allow the base station to continuously adjust the weighting co-efficients of its array antenna, thereby ensuring reliable communication. The advantages/limitations of each of the protocols are examined under various conditions. While the first media access protocol works efficiently in pedestrian oriented systems, it is unsuitable for providing service to vehicular remote users. The latter two MAC protocols facilitate the effective sharing of the high speed radio channel among a plurality of fixed point, pedestrian and remote users in fast moving vehicles, and achieve utilization efficiencies of over 90% for typical system parameters.
KeywordsMedium Access Control Array Antenna Medium Access Control Protocol Remote User Polling Segment
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