Adaptive Modulation in Spectrum-Sharing Channels Under Delay Quality-of-Service Constraints

• Published in: IEEE transactions on vehicular technology 2011-03, Vol.60 (3), p.901-911
• Main Authors: Musavian, L, Aissa, S, Lambotharan, S
• Format: Article
• Language: English
• Subjects: Adaptive modulation; Allocations; Applied sciences; Channels; Delay; delay quality-of-service (QoS) constraint; effective capacity; Electrical engineering. Electrical power engineering; Electrical power engineering; Exact sciences and technology; Fading; fading channels; Information, signal and communications theory; Interference; Links; Modulation; Modulation, demodulation; Operation, maintenance, reliability; Operation. Load control. Reliability; Optimization; Power networks and lines; Quadrature amplitude modulation; Quality of service; Receivers; Resource management; service-outage constraint; Signal and communications theory; spectrum sharing; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); Transmitters
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2010.2097282

We propose a variable-rate variable-power M -level quadrature amplitude modulation (MQAM) scheme employed under delay quality-of-service (QoS) constraints over spectrum-sharing channels. An underlay cognitive radio system, with one primary user and a secondary user, with constraints on interference leakage imposed by the primary receiver is considered. The transmission parameters of the secondary user are set optimally such that the successful communications for the primary user in terms of a minimum rate to be supported is satisfied, irrespective of co-existence with the secondary user. We obtain interference constraints that, when satisfied by the secondary users, is sufficient to satisfy the service outage requirement of the primary user. We further study the performance of the secondary user's link employing an adaptive MQAM scheme when, on top of the aforementioned interference constraint, the secondary user is also required to satisfy a statistical delay QoS constraint. Considering two modulation schemes, i.e., continuous MQAM and discrete MQAM with restricted constellations, we obtain the effective capacity of the secondary user's link and derive the optimum power allocation that maximizes the effective capacity of the secondary user.