Capacity and power allocation for spectrum-sharing communications in fading channels

• Published in: IEEE transactions on wireless communications Vol. 8; no. 1; pp. 148 - 156
• Main Authors: Musavian, L., Aissa, S.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.01.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Allocations; Applied sciences; AWGN; Channel capacity; Channels; Cognitive radio; ergodic capacity; Ergodic processes; Exact sciences and technology; Exact solutions; Fading; fading channels; Frequency; Interference; Licenses; minimum-rate capacity; Organization, operation and development plans; outage capacity; peak and average received-power constraints; Radio; Radio spectrum management; Radiocommunication specific techniques; Radiocommunications; Rayleigh channels; Receivers; Spectrum allocation; spectrum sharing; Studies; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); Wireless communication; Wireless networks; minimum-rate capacity; Resource allocation; Power allocation; Implementation; ergodic capacity; Optimal planning; Peak power; Radio spectrum; spectrum sharing; Fading channels; Channel capacity; Outage; outage capacity; Frequency allocation; Transmission channel; Theoretical study; Ergodicity; Cognitive radio; S band; peak and average received-power constraints; Numerical simulation; Metric; Rayleigh fading; Resource management; Software radio; Power spectrum
• ISSN: 1536-1276; 1558-2248
• DOI: 10.1109/T-WC.2009.070265

This paper investigates the fundamental capacity limits of opportunistic spectrum-sharing channels in fading environments. The concept of opportunistic spectrum access is motivated by the frontier technology of cognitive radio which offers a tremendous potential to improve the utilization of the radio spectrum by implementing efficient sharing of the licensed spectrum. In this spectrum-sharing technology, a secondary user may utilize the primary user's licensed band as long as its interference to the primary receiver remains below a tolerable level. Herein, we consider that the secondary user's transmission has to adhere to limitations on the ensuing received power at the primary's receiver, and investigate the capacity gains offered by this spectrum-sharing approach in a Rayleigh fading environment. Specifically, we derive the fading channel capacity of a secondary user subject to both average and peak received-power constraints at the primary's receiver. In particular, considering flat Rayleigh fading, we derive the capacity and optimum power allocation scheme for three different capacity notions, namely, ergodic, outage, and minimum-rate, and provide closed-form expressions for these capacity metrics. Numerical simulations are conducted to corroborate our theoretical results.