Cognitive Radio Operation under Directional Primary Interference and Practical Path Loss Models

Kentaro NISHIMORI  Rocco DI TARANTO  Hiroyuki YOMO  Petar POPOVSKI  

IEICE TRANSACTIONS on Communications   Vol.E94-B   No.5   pp.1243-1253
Publication Date: 2011/05/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E94.B.1243
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Antenna and Propagation Technologies Contributing to Diversification of Wireless Technologies)
Category: Radio System
cognitive radio,  spatial opportunity,  directional antenna,  heterogeneous propagation path loss conditions,  target CIR,  antenna height,  

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This paper discusses the possibility of deploying a short-range cognitive radio (secondary communication system) within the service area of a primary system. Although the secondary system interferes with the primary system, there are certain locations in the service area of the primary system where the cognitive radio can reuse the frequency of the primary system without causing harmful interference to it and being disturbed by the primary system. These locations are referred to as having a spatial opportunity for communications in the secondary system, since it can reuse the frequency of the primary system. Simulation results indicate that the antenna gain, beamwidth, and propagation path loss greatly affect the spatial opportunity of frequency reuse for the secondary users. The results show that spatial spectrum reuse can be significantly increased when the primary system users are equipped with directional antennas. An important component in this study is the heterogeneous path loss model, i.e., the path loss model within the primary system is different from the model used to calculate the interference between the primary and the secondary systems. Our results show that the propagation models corresponding to the actual antenna heights in the primary/secondary system can largely impact the possibilities for spectrum reuse by the cognitive radios.