Real and complex analysis, 3rd ed.
Real and complex analysis, 3rd ed.
Primal-dual interior-point methods
Primal-dual interior-point methods
IEEE Spectrum
NeXt generation/dynamic spectrum access/cognitive radio wireless networks: a survey
Computer Networks: The International Journal of Computer and Telecommunications Networking
Wireless Communications
Channel models for ultrawideband personal area networks
IEEE Wireless Communications
Cognitive Multiple Access Via Cooperation: Protocol Design and Performance Analysis
IEEE Transactions on Information Theory
Recent advances on TD-SCDMA in China
IEEE Communications Magazine
The evolution path of 4G networks: FDD or TDD?
IEEE Communications Magazine
Spectrum sensing in cognitive radio networks: requirements, challenges and design trade-offs
IEEE Communications Magazine
Cognitive radio: brain-empowered wireless communications
IEEE Journal on Selected Areas in Communications
Multiple signal waveforms adaptation in cognitive ultra-wideband radio evolution
IEEE Journal on Selected Areas in Communications - Part 1
A tutorial on decomposition methods for network utility maximization
IEEE Journal on Selected Areas in Communications
Spectrum sensing: A distributed approach for cognitive terminals
IEEE Journal on Selected Areas in Communications
Potential bargaining for resource allocation in cognitive relay transmission
Journal of Network and Computer Applications
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In this paper, we consider a relay-assisted wideband cognitive-radio (CR) system under the assumption that the frequency band chosen by the CR relay network for unlicensed spectrum usage overlaps with one or more bands dedicated to primary (e.g., licensed) narrowband links. Our objective is to optimize the performance of the CR system while limiting the interference in direction of the primary receivers, without requiring any adaptation of the transmitted signal spectra at the cognitive nodes. To this end, we study appropriate transmit power allocation (TPA) strategies among the cognitive relays. We first investigate the optimal centralized (OC) TPA solution and show that it can be formulated as a linear program. Since the OC-TPA solution requires a considerable amount of information exchange between the cognitive nodes, we develop two distributed TPA schemes, namely (i) a fully decentralized (FD) TPA scheme and (ii) a distributed feedback-assisted (DFA) TPA scheme. The FD-TPA scheme aims at maximizing the output signal-to-interference-plus-noise ratio (SINR) at the destination node of the CR network according to a best-effort strategy. It requires neither feedback information from the destination node nor an exchange of channel state information between the cognitive relays. The DFA-TPA scheme, on the other hand, utilizes feedback information from the destination node, in order to achieve a pre-defined target output SINR value, while minimizing the overall transmit power spent by the relays. Analytical and simulation-based performance results illustrate that notable performance improvements compared to non-cooperative transmission (i.e., without relay assistance) are achieved by the proposed schemes, especially when more than two hops are considered. In particular, the proposed distributed TPA schemes typically perform close to the OC-TPA solution.