Abstract
In cognitive radio systems, secondary users can utilize multiple dispersed bands that are not used by primary users. In this paper, time delay estimation of signals that occupy multiple dispersed bands is studied. First, theoretical limits on time delay estimation are reviewed. Then, two-step time delay estimators that provide trade-offs between computational complexity and performance are investigated. In addition, asymptotic optimality properties of the two-step time delay estimators are discussed. Finally, simulation results are presented to explain the theoretical results.
Highlights
Cognitive radio is a promising approach to implement intelligent wireless communications systems [1,2,3,4,5,6,7,8]
This study considers diversity combining for time-delay estimation, where the diversity results from the dispersed spectrum utilization of the cognitive radio system
Simulations are performed in order to evaluate the performance of the proposed time-delay estimators and compare them with each other and against the Cramer-Rao lower bound (CRLB)
Summary
Cognitive radio is a promising approach to implement intelligent wireless communications systems [1,2,3,4,5,6,7,8]. Cognitive radios can be perceived as more capable versions of software defined radios in the sense that they have sensing, awareness, learning, adaptation, goal driven autonomous operation, and reconfigurability features [9, 10]. In order to facilitate such opportunistic spectrum utilization, it is important that cognitive radio devices are aware of their positions, and monitor the environment continuously. These location and environmental awareness features of cognitive radios have been studied extensively in the literature [10, 13,14,15,16,17,18,19]. [18] introduces the concept of a topology engine for cognitive
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