Search Results (1 - 1 of 1 Results)

Sort By  
Sort Dir
Results per page  

Yoon, Suk-UnDynamic Radio Resource Allocation in Wireless Sensor and Cognitive Radio Networks
Master of Science, The Ohio State University, 2009, Electrical and Computer Engineering

In wireless networks, it is required to change an operating frequency as part of the radio resource management due to strong interference or system requirements of accessing radio resources. In this thesis, we propose two radio resource management schemes in wireless sensor networks and cognitive radio networks. In the proposed schemes, sensor networks switch to a new channel when they detect strong interference and a secondary user in cognitive radio networks moves to a new spectrum when it detects or predicts the presence of a primary user.

In the first part of the thesis, we propose a channel hopping scheme which can be used for interfered wireless networks. With the additive functionality of a channel hopping mechanism on the sensor network stack, we aim to avoid the interference from other sensor nodes and wireless technologies on ISM band as well as avoid narrow-band jamming. For simple and reliable channel hopping, we introduce an Adaptive Channel Hopping scheme, a spectrum environment aware channel hopping scheme, for interference robust wireless sensor networks. When the channel status becomes suboptimal to communicate, the adaptive channel hopping lets the sensors switch to a new clean channel. To generate channel selection/scanning orders which minimize channel hopping latency, we use two parameters which are link quality indicator (LQI) and channel weighting. The proposed adaptive channel hopping scheme is evaluated through simulations. Simulation results indicate that the proposed scheme significantly reduces the channel hopping latency and selects the best quality channel.

In the second part of the thesis, we propose a novel approach to spectrum management in cognitive radio networks. To support flexible use of spectrum, cognitive radio networks employ spectrum mobility management schemes, including spectrum handoff, which refers to the switching of the operating spectrum due to changes in licensed (primary) user activity. Spectrum handoff inevitably results in temporary disruption of communication for the unlicensed (secondary) user operating in a licensed band opportunistically. Minimization of secondary user service disruption is an important objective of spectrum handoff schemes. In this thesis, we introduce a new type of spectrum handoff called Voluntary Spectrum Handoff assisted by a primary user spectrum usage estimation scheme. The two mechanisms proposed under voluntary spectrum handoff method estimate opportune times to initiate unforced spectrum handoff events to facilitate setup and signaling of alternative channels without having communication disruption, which occurs when a secondary user is forced out of an operating spectrum due to primary user activity. To estimate primary user spectrum usage, channel usage information is continuously updated with a fixed spectrum sensing window and a variable history window. Proposed voluntary spectrum handoff and primary usage estimation schemes are evaluated through extensive simulations. Simulation results indicate that the proposed schemes significantly reduce the communication disruption duration due to handoffs.


Eylem Ekici (Advisor); Bradley Clymer, D. (Committee Member)




Channel Hopping; Wireless Sensor Networks; Spectrum Handoff; Cognitive Radio Networks