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Spectrum access by an unlicensed secondary user (SU) in a cognitive radio network (CRN) is challenging due to the dynamic nature of spectrum availability and possibility of collisions with the primary user (PU). SU uses a scheme where SU's packets are interleaved with periodic sensing to detect PU's return. To utilize spectrum efficiently, this paper proposes an opportunistic spectrum approach with...
In multichannel cognitive radio networks (CRN), the sequence of sensing order is essential to determine the efficiency of detecting an idle channel and the effective time for spectrum access. Current works on the optimal channel sensing order have to know priori knowledge such as the channel idle probabilities, channel gains and achievable rates of different channels, which dynamically evolve and...
Cognitive Radio (CR) is an approach for efficient spectrum utilization by the secondary user. But as the channel quality degrades due to environmental effects such as fading or the primary users' reaccess of the channel, the secondary user has to vacate the channel. After that secondary user has to start restoration by searching and sensing other channels. Restoration is done with an objective of...
The partially observed Markov decision process (POMDP) is very important in cognitive radio network. We can formulate the opportunistic spectrum access in the framework of POMDP. However, no attention was paid to the algorithm in the presence of unknown environment. For the rapidly changing cognitive network with unknown environment, we firstly establish the channel state model based on MLA and prove...
In this paper, an Opportunity Spectrum Access (OSA) strategy for multiuser was proposed. Assuming each CR user only can sense one channel at a time due to hardware restraints. And they only can sense one time during a slot time. The idle probability of each channel is predicted by the POMDP framework. If all CR users use the same OSA strategy with deterministic POMDP framework, collision will happen...
Opportunistic spectrum access is an important issue in cognitive radio systems. In this paper, we propose a distributed opportunistic spectrum access scheme based on sequential channel-sensing in decentralized CRN (cognitive radio network). Different from the traditional spectrum sensing scheme, the scheme proposed allows a secondary users to sense many channels one by one sequentially in a slot....
In this paper, designing channel sensing policies for cognitive radio networks is discussed. A discrete-time semi- Markov channel model is first introduced, which facilitates the analysis on more general channel occupancy behaviors and possible asynchronism among primary and secondary users. Based on the characteristics of the channels at the stationary state, multiple channel sensing policies have...
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