Short-Range Low-VHF Channel Characterization in Cluttered Environments

The lower VHF band has potential for low power, short range communications, as well as for geolocation applications, in both indoor and urban environments. Most prior work at low VHF focuses on longer range path loss modeling, often with one node elevated. In this paper we study indoor/outdoor near-ground scenarios through experiments and electromagnetic wave propagation simulations. These include the effects of indoor penetration through walls and obstacles as well as indoor/outdoor cases, for both line-of-sight (LoS) and non-LoS (NLoS), at ranges up to 200 meters. Mounting our receiver on a robotic platform enabled the collection of thousands of measurements over an extended indoor/outdoor test area. We measure the channel transfer function, employing bandpass waveform sampling, with pulse and tone probe signals. Based on statistical tests, we show that the measured channels have a nearly ideal scalar attenuation and delay transfer function, with minimal phase distortion, and little to no evidence of multipath propagation. Compared with higher VHF and above, the measured short range VHF channels do not exhibit small scale fading, which simplifies communications receiver signal processing, and enables phasebased geolocation techniques.