Characterization and Modeling of Wireless Channels for Vehicular Emergency Communications in Urban Scenarios

To accurately characterize wireless channel properties of very high frequency (VHF) communication systems in urban vehicular emergency scenarios and enhance the design of vehicular emergency VHF networks, field measurements were conducted at 240 MHz in typical urban environments in Changsha City, Hunan Province. Accounting for the dynamic diversity of vehicular emergency operations, satellite imagery and panoramic recordings classified propagation environments into quasi-line-of-sight (QLOS) and non-line-of-sight (NLOS) zones. Markov chain-based channel models were established using multipath parameters extracted via the space-alternating generalized expectation-maximization (SAGE) algorithm. Analyses of root-mean-square delay spread (RMS-DS) and stationarity time revealed significant non-stationarity in VHF channels for vehicular emergencies. Compared to QLOS zones, NLOS regions obstructed by high-rise buildings exhibited larger RMS-DS values (indicating dispersed multipath), reduced stationarity durations, lower K-factor and heightened susceptibility to frequency-selective fading.