Spatial spectrum holes for cognitive radio with relay-assisted directional transmission

• Published in: IEEE transactions on wireless communications Vol. 8; no. 10; pp. 5270 - 5279
• Main Authors: Guodong Zhao, Jun Ma, Li, G.Y., Tao Wu, Young Kwon, Soong, A., Chenyang Yang
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-10-2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Band spectra; Chromium; Cognitive radio; Communications technology; Detection; Detectors; directional transmission; Exact sciences and technology; Fading; Interference; Links; Radio; Radio transmitters; Radiocommunication specific techniques; Radiocommunications; Receivers; relay; Relays; Self-propagating synthesis; Spectrum allocation; spectrum hole; Telecommunications; Telecommunications and information theory; Transmitters; Transmitters. Receivers; Vehicle dynamics; Wireless communication; Wireless communications; Performance evaluation; directional transmission; Relay; spectrum hole; Transmitter; Cognitive radio; Cognitive system; Software radio
• ISSN: 1536-1276; 1558-2248
• DOI: 10.1109/TWC.2009.081541

Spectrum hole (SH) is defined as a spectrum band that can be utilized by unlicensed users, which is a basic resource for cognitive radio (CR) systems. Most of existing contributions detect SHs by sensing whether a primary signal is present or absent and then try to access them so that the CR and primary users use the spectrum band either at different time slots or in different geographic regions. In this paper, we propose a novel scheme with relays or directional relays for CR users to exploit new spectrum opportunity, called spatial SH. It can provide higher spectrum efficiency by coexistence of primary and CR users at the same region, time, and spectrum band. In particular, when the spectrum opportunity of a direct link from a CR transmitter to a CR receiver does not appear, our scheme may still establish the communication through indirect links, i.e., other CR users act as relay stations to assist the communication by using other spatial domains. Furthermore, we analyze the successful communication probabilities of CR users and demonstrate that the spectrum efficiency can be considerably improved by our scheme.