A Nano-Cellular Local Area Network Using Near-Field RF Coupling
This paper describes a new type of wireless LAN based on near-field RF coupling. The system exploits the rapid spatial decay of field strength within the near-field to provide high isolation between adjacent cells. We believe that this Nano-Cellular system offers unique advantages for mobile computing in an indoor environment. At the operating frequency of 5.3 MHz, the cell size is approximately that of a single office. Small cells offer several benefits, including the possibility of channel re-use and the ability to provide information about user location. Despite the low operating frequency, the available bit rate of 250kbps is sufficient for many practical applications. The radio wavelength of 60m is sufficiently long to eliminate standing wave problems which often plague indoor UHF and microwave systems. The transceiver uses very little power, and has a simple, low-cost design.
The operational theory of the near-field radio is presented, together with detailed measurements of signal strength and packet reception in an indoor environment. The choice of operating frequency is explained as a tradeoff among cell size, bandwidth and FCC limitations. Details of the radio hardware are given, including modulation techniques and antenna optimization. The characteristics of indoor RF noise sources are described, along with the implications for the placement of base stations. Measured results are presented for several geometries where packet loss can result from contention among devices.
Efficient, fair channel allocation among multiple clients is provided by a new Media Access Control protocol that takes advantage of the high adjacent-cell isolation provided by near-field coupling. This protocol is described, and detailed measurements are presented for several configurations.
KeywordsData Packet Receive Signal Strength Medium Access Control Protocol Packet Reception Loop Antenna
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