Byungjoo Lee

Efficient Utilization of Available Channels in Dynamic Spectrum Access Networks

In case of dynamic spectrum access networks, how to efficiently utilize the dynamically available bandwidth is very important to enhance the performance of the networks. In this paper, we propose an Error Adaptive MAC protocol which adaptively changes its transmission mode according to the channel status. Using the cognitive radio technology, additional channels are assumed to be randomly available for data transmission. When the channel error rate is relatively high, those additional channels are utilized for error recovery; otherwise, the extra channels can be used to increase the throughput if the wireless medium is stable and reliable. We formulate an analytical model to study the dynamics of our adaptive MAC protocol, and using simulation, show our proposed method can significantly enhance the throughput of dynamic spectrum access networks.

An adaptive MAC protocol for efficient utilization of available spectrum bandwidth

Cognitive Radio has been proposed as a promising technology to solve todays spectrum scarcity problem. Most part of frequency spectrum is already allocated for existing wireless systems. Cognitive radio technology has aroused peoples interest in utilizing unused spectrum of the legacy systems. Due to the stochastic behavior or the available channels in cognitive radio networks, it has been a matter of primary concern how to effectively use the randomly available spectrum resources. In this paper, we propose an error-adaptive MAC protocol which enhances throughput of cognitive radio networks, by switching between error-recovery mode and dual-transmit mode according to the channel status. When the link status is not good, additional channels acquired from the legacy network are used for the frame error recovery. On the other hand, in case the wireless medium is stable and reliable, the extra channels can be used to increase the throughput of cognitive devices. The simulation results also show that, by adaptively changing the transmission modes, one can significantly enhance the throughput of cognitive radio networks.