• Journal of KIISE:Information Networking
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• v.36 no.3
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• pp.243-250
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• 2009

Channel diversity is exploited to increase multiuser diversity gains in IEEE 802.11 WLANs. To this end, we propose an opportunistic channel switching method and evaluate this with different number of stations, number of channels, switching latency, and the average channel condition of stations.

• Journal of Communications and Networks
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• v.16 no.1
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• pp.56-66
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• 2014

We propose a novel opportunistic access scheme for cognitive radios in an interweave cognitive system, that considers the channel gain as well as the predicted idle channel probability (primary user occupancy: Busy/idle). In contrast to previous work where a cognitive user vacates a channel only when that channel becomes busy, the proposed scheme requires the cognitive user to switch to the channel with the next highest idle probability if the current channel's gain is below a certain threshold. We derive the threshold values that maximize the long term throughput for various primary user transition probabilities and cognitive user's relative movement.

• Journal of Communications and Networks
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• v.11 no.2
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• pp.104-114
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• 2009

In this paper, a technique is proposed that enables secondary users to evaluate channel availability in cognitive radio networks. Here, secondary users estimate the utilization of channels via predicting the traffic pattern of primary user, and select a proper channel for radio transmission. The proposed technique reduces the channel switching rate of secondary users (the rate of switching from one channel to another) and the interference on primary users, while maintaining a reasonable call blocking rate of secondary users.