On Ergodic Capacity of Spectrum-Sharing Systems in Fading Channels

Xiang CHEN
Shidong ZHOU

IEICE TRANSACTIONS on Communications   Vol.E92-B    No.5    pp.1904-1907
Publication Date: 2009/05/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E92.B.1904
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Wireless Communication Technologies
ergodic capacity,  opportunistic spectrum access,  received power constraint,  spectrum-sharing,  

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In spectrum-sharing systems where the secondary user (SU) opportunistically accesses the primary user (PU)'s licensed channel, the SU should satisfy both the transmit power constraint of the SU transmitter and the received power constraint at the PU receiver. This letter studies the ergodic capacity of spectrum-sharing systems in fading channels. The ergodic capacity expression along with the optimal power allocation scheme is derived considering both the average transmit and received power constraints. The capacity function in terms of the two power constraints is found to be divided into transmit power limited region, received power limited region and dual limited region. Numerical results in Rayleigh fading channels are presented to verify our analysis.