Propagation and bit error ratio measurements for a microcellular system

Abstract

Propagation measurements are provided for highway and city centre microcells. Measurements along various motorways were taken with base station (BS) antennas at 10 m elevations. Pseudo-random binary sequences (PRBS) were transmitted via non-coherent FSK at 905 MHz. Low radiated power (16 mW into an 18-element Yagi) was used, and the signal level and bit error ratio (BER) were recorded by a mobile station (MS). The microcell length was found to be a function of the received field strength and, therefore, the BER. It was found that the cell lengths varied between 1 to 2 km for a BER of 10−3 or better. Although the PDF of the received signal was Rician the microcell length was determined using the more pessimistic Rayleigh PDF. Two and three microcell clusters were considered. An inverse fourth power law was observed, and the received signal power in the microcell varied linearly with radiated power. For power levels of only 1 μW, error free transmission was found to occur over a cell length of 400 m.Detailed measurements in the Harley Street area in Central London enabled us to study how signals propagate in a nearly rectilinear grid pattern of roads. A theoretical model was established that provided signal levels that were close to those measured. Experiments were performed with the base station at junctions, roundabouts and at major city arteries. The inverse fourth power loss characteristics occurred, and the radiation distribution was found to be relatively insensitive to antenna type as the street pattern was the dominant factor.