Abstract
In this paper, the performance of multichannel transmission in cognitive radio is studied. Both QoS constraints and interference limitations are considered. The activities of the primary users (PU)s are initially detected by cognitive users (CU)s who perform sensing process over multiple channels. They transmit in a single channel at variable power and rates depending on the channel sensing decisions and the fading environment. The cognitive operation is modeled as a state transition model in which all possible scenarios are studied. The QoS constraint of the cognitive users is investigated through statistical analysis. Analytical form for the effective capacity of the cognitive radio channel is found. Optimal power allocation and optimal channel selection criterion are obtained. Impact of several parameters on the transmission performance, as channel sensing parameters, number of available channels, fading and other, are identified through numerical example.
Highlights
Much interest in cognitive radio systems is raised due to their ability to utilize the available spectrum much more effectively
Challenges in providing QoS assurances increase due to the fact that cognitive users should operate under constraints on the interference levels that they produce to primary users
The effective capacity of cognitive radio channels is studied where the cognitive radio detects the activity of the primary users in a multichannel case, and it performs data transmission in one of these channels using both rate and power adaptation that depends on the channel conditions and the activity of the primary users
Summary
Much interest in cognitive radio systems is raised due to their ability to utilize the available spectrum much more effectively. These interference constraints lead to variations in transmit power levels and channel accesses. This discontinuing in accessing the channels due to the activity of primary users make it difficult for the cognitive users to satisfy their own QoS requirement. The authors in [1] proposed a QoS constrained power and rate allocation scheme for spectrum sharing systems in which it was guaranteed a minimumrate to the primary user for a certain percentage of time.
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