We integrate the two models of Cognitive Radio (CR), namely, the conventional Sense-and-Scavenge (SS) Model and Symbiotic Cooperative Relaying (SCR). The resultant scheme, called SS-SCR, improves the efficiency of spectrum usage and reliability of the transmission links. SS-SCR is enabled by a suitable cross-layer optimization problem in a multihop multichannel CR network. Its performance is compared for different PU activity patterns with those schemes which consider SS and SCR separately and perform disjoint resource allocation. Simulation results depict the effectiveness of the proposed SS-SCR scheme. We also indicate the usefulness of cloud computing for a practical deployment of the scheme. 1. Introduction 1.1. Cognitive Radio/Dynamic Spectrum Access The emerging Cognitive Radio (CR) technology is an attempt to alleviate the inefficient utilization of the spectrum, created by the current Command-and-Control spectrum access policy. It temporarily allows unused portions of the spectrum (spectrum holes or white-spaces), owned by the licensed users, known as primary users (PUs), to be accessed by unlicensed users, known as secondary users (SUs), without causing intrusive interference to the former’s communication [1]. This is the Sense-and-Scavenge (SS) Model of conventional CR. A CR node is characterized by an adaptive, multi-dimensionally aware, autonomous radio system empowered by advanced intelligent functionality, which interacts with its operating environment and learns from its experiences to reason, plan, and decide future actions to meet various needs [2]. In the SS model of CR, the temporal PU activity patterns have a significant influence on the opportunities for the SUs. The source traffic for the PU alternates between ON (busy) and OFF (idle) periods. The ON/OFF activity is characterized by suitable statistical models, for predictive estimation of the patterns. Exponential [3–6] and log-normal [3–5] distributions are popularly used in the literature to model the ON (and OFF) times of the PU activity. Measurements have also revealed that successive ON and OFF periods are independent, though in some cases long-term correlations exist [4]. 1.2. Symbiotic Cooperative Relaying An interesting paradigm that has surfaced in the research surrounding CR is a symbiotic architecture, which improves the efficiency of spectrum usage and reliability of the transmission links [7–12]. According to this model, which we refer to as Symbiotic Cooperative Relaying (SCR), the PU seeks to enhance its own communication by leveraging other users in its vicinity,
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