On peak versus average interference power constraints for protecting primary users in cognitive radio networks

• Published in: IEEE transactions on wireless communications Vol. 8; no. 4; pp. 2112 - 2120
• Main Author: Zhang, Rui
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.04.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Bandwidth; Channel capacity; Channels; Chromium; Cognitive radio; Equipments and installations; Exact sciences and technology; Fading; fading channel capacity; Interference; Interference constraints; interference diversity; interference temperature; Links; Protection; Radio; Radio networks; Radio transmitters; Radiocommunication specific techniques; Radiocommunications; Radiorelay links; Receivers; Relays; Resultants; spectrum sharing; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); Wireless communication; Fading channels; Fading; Channel capacity; Outage; Wireless telecommunication; interference diversity; Radio link; Ergodicity; Cognitive radio; Flexibility; interference temperature; Deterministic approach; Peak power; fading channel capacity; Radio communication; Software radio; spectrum sharing
• DOI: 10.1109/TWC.2009.080714
• ISSN: 1536-1276

This paper considers spectrum sharing for wireless communication between a cognitive radio (CR) link and a primary radio (PR) link. It is assumed that the CR protects the PR transmission by applying the so-called ldquointerference-temperaturerdquo constraint, whereby the CR is allowed to transmit regardless of the PR's on/off status provided that the resultant interference power level at the PR receiver is kept below some predefined threshold. For the fading PR and CR channels, the interference-power constraint at the PR receiver is usually one of the following two types: one is to regulate the average interference power (AIP) over all different fading states, while the other is to limit the peak interference power (PIP) at each fading state. From the CR's perspective, given the same average and peak power threshold, the AIP constraint is more favorable than the PIP counterpart because of its more flexibility for dynamically allocating transmit powers over different fading states. On the contrary, from the perspective of protecting the PR, the more restrictive PIP constraint appears at a first glance to be a better option than the AIP. Some surprisingly, this paper shows that in terms of various forms of capacity limits achievable for the PR fading channel, e.g., the ergodic and outage capacities, the AIP constraint is also superior over the PIP. This result is based upon an interesting interference diversity phenomenon, where randomized interference powers over the fading states in the AIP case are more advantageous over deterministic ones in the PIP case for minimizing the resultant PR capacity losses. Therefore, the AIP constraint results in larger fading channel capacities than the PIP for both the CR and PR transmissions.