Predicting impact of multi-paths on phase change in map-based vehicular ad hoc networks
2014
Dynamic Spectrum Access, which through its ability to adapt the operating frequency of a radio, is widely believed to be
a solution to the limited spectrum problem. Mobile Ad Hoc Networks (MANETs) can extend high capacity mobile
communications over large areas where fixed and tethered-mobile systems are not available. In one use case with high
potential impact cognitive radio employs spectrum sensing to facilitate identification of allocated frequencies not
currently accessed by their primary users. Primary users own the rights to radiate at a specific frequency and geographic
location, secondary users opportunistically attempt to radiate at a specific frequency when the primary user is not using
it. We quantify optimal signal detection in map based cognitive radio networks with multiple rapidly varying phase
changes and multiple orthogonal signals. Doppler shift occurs due to reflection, scattering, and rapid vehicle movement.
Path propagation as well as vehicle movement produces either constructive or destructive interference with the incident
wave. Our signal detection algorithms can assist the Doppler spread compensation algorithm by deciding how many
phase changes in signals are present in a selected band of interest. Additionally we can populate a spatial radio
environment map (REM) database with known information that can be leveraged in an ad hoc network to facilitate
Dynamic Spectrum Access. We show how topography can help predict the impact of multi-paths on phase change, as
well as about the prediction from dense traffic areas. Utilization of high resolution geospatial data layers in RF
propagation analysis is directly applicable.
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