Channel Measurement, Characterization, and Modeling for Wireless Local Loops

Abstract

The aim of the work presented in this paper wasto produce measurement-based wideband channel models forwireless local loops (WLL). The paper describes thefield measurements, the resulting channelcharacteristics, and the channel models based on the results.The impulse response measurements were performed at 1.28GHz in three different environments, namely urban,suburban high-rise, and suburban small house. At each site several rooms were selected, and ineach room a burst of impulse responses was recorded atseveral transmitter antenna positions. A long-termrecording was also performed in one location at each site. The multipath characteristics of theurban and suburban high-rise environments are verysimilar, with rms delay spreads of below 280 ns at 90%of positions. The suburban small-house environment can be expected to show less severe multipathpropagation. In general the multipath characteristicscan vary significantly even within a single room. Also,the long-term variation of the channel characteristics is significant. The results were combined intosix channel models, each with a different delay powerspectrum. The amplitude fading for all these ischaracterized by a Rician distribution with the Rician factor varying between 3 and 18 dB, thelevel-crossing rate between 0.1 and 0.51/s, and the fadedurations between 0.25 and 20 s.