Cell Range Extension Techniques for Wide-Area Ubiquitous Network

Abstract

This paper describes a newly developed wireless access system for the wide area ubiquitous network (WAUN), a large cell-based public sensor network. It introduces two key technologies to achieve WAUN with wide area coverage. The first is a digitalized radio over optical fiber (DROF) subsystem that allows cost-effective commercial packet based networks to transfer wireless RF signals among distributed access points. The second is a frequency offset transmitter diversity scheme that achieves suboptimal diversity gain without rate loss, regardless of the number of antennas, by using intentional and orderly frequency offset. Finally, we have devoloped a prototype system that implements the proposed techniques and confirm the feasibility of wide area coverage, i.e., cell radius of 3.5 km, through field trials.Keywords-sensor network, wide area ubiquitous network, digitized radio over fiver, frequency offset diversity

Wireless Relay Technologies for Monitoring Underground Infrastructures

“…To address this problem, we have developed a tech-nology that suppresses the fluctuation of the reception level by transmitting radio waves from multiple antennas simultaneously with slightly different frequencies [7]. This makes it possible to forcibly change the phase relationship of arrival waves at the fixed reception point.…”