Experimental tests of coverage and handoff for a low-power TDMA wireless access system

Experimental results for a low-power TDMA wireless access system are presented. Experimental equipment consisting of two radio ports mounted on traffic lights and two radio port controllers located in a central office were interconnected using HDSL transceivers and copper loop facilities. Portables communicated with the radio ports using a low-delay 2 millisecond TDMA frame structure with 10 time-slots and QPSK burst modulation at 500 kbps as specified in Bellcore's Technical Advisory on wireless access. The operating frequencies were between 2.1 and 2.2 GHz. A portable controlled automatic link transfer algorithm was tested between the two radio ports. The results show that the use of diversity antennas in the portable permits the use of signal strength hysteresis values as low as 5 dB without excessive "ping-ponging". Radio port coverage, characterized in terms of word error rate and subjective voice quality, was substantially "canyon-oriented", which is consistent with propagation measurements at 2 GHz with radio port antennas located below the roofs. Significant in-building coverage into street-side businesses was demonstrated.<
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