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In this paper we investigate opportunistic spectrum access in cognitive radio networks when a decode and forward relay is employed. To better exploit the white space in primary networks, we propose two cognitive spectrum access approaches based on white space modeling, referred to as successive sensing based spectrum access and simultaneous sensing based spectrum access. We further study the optimal...
Cognitive radios (CR) and cooperative communications represent new paradigms that both can effectively improve the spectrum efficiency of future wireless networks. In this paper, we investigate the problem of cooperative relay in CR networks for further improved network performance. The objective is to provide an analysis for the comparison of two representative cooperative relay strategies, decode...
Cognitive radio technology can improve spectrum efficiency by allowing potential secondary users (SUs) to use licensed spectrum when primary users (PUs) are absent. How to share and allocate the unoccupied spectrum among SUs directly affects spectrum utilization. Relay-assisted transmitting in cognitive radio networks (CRN) is an effective technology to improve spectrum utilization and increase transmitting...
This work evaluates opportunistic relaying in the presence of thermal noise as well as interference, when channel sensing is conducted reactively, in slow fading environments. The studied scenario employs a single gateway that provides access towards several destinations with weak links and exploits a network of intermediate relays. In sharp contrast to prior art, no inter-relay channel state information...
When both a high-priority and a low-priority system share a common frequency band, the low-priority station must sense the presence of the high-priority system, and if required, postpone its transmission or reduce its transmit power to avoid possible interference. To compensate, transmission opportunities of the low-priority system should be ensured as much as possible. Using a transmission scheme...
In this paper, we investigate the outage probability of a wireless two relay (diamond relay) network which consists of a source, a destination and two network clusters. Each cluster is defined by a number of cognitive nodes (unlicensed) and a primary node (licensed). The cognitive nodes relay the source information by employing opportunistic spectrum access. We consider amplify-and-forward (AF) relaying...
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