Fundamental limits on time delay estimation in dispersed spectrum cognitive radio systems

IEEE Trans. Wireless Commun.

et al. 2011

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Abstract-Theoretical limits on time-of-arrival (equivalently, range) estimation are derived for multicarrier systems in the presence of interference. Specifically, closed-form expressions are obtained for Cramer-Rao bounds (CRBs) in various scenarios. In addition, based on CRB expressions, an optimal power allocation (or, spectrum shaping) strategy is proposed. This strategy considers the constraints not only from the sensed interference level but also from the regulatory emission mask. Numerical results are presented to illustrate the improvements achievable with the optimal power allocation scheme, and a maximum likelihood time-of-arrival estimation algorithm is studied to assess the effects of the proposed approach in practical estimators.Index Terms-Ranging, time-of-arrival (TOA) estimation, interference, orthogonal frequency division multiplexing (OFDM), Cramer-Rao bound (CRB), cognitive radio.

mentioning

confidence: 99%

Range Estimation in Multicarrier Systems in the Presence of Interference: Performance Limits and Optimal Signal Design

Karisan¹,

Dardari

IEEE Trans. Wireless Commun.

et al. 2011

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“…1. For instance, in a cognitive radio system, primary users are the main owners of the spectrum, and secondary users can utilize the frequency bands of the primary users when they are available [23]- [25], [37], [38]. In such a case, the available bands in the spectrum can be considered as the channels in Fig.…”

Section: Problem Formulationmentioning

confidence: 99%

“…Then, by substituting the constraints in (38)- (40) into the objective function and specifying the search space, the optimization problem in (35) can be obtained.…”

Section: B Solution Of Optimal Channel Switching Problemmentioning

confidence: 99%

Optimal Channel Switching Strategy for Average Capacity Maximization

Sezer

İnaltekin

2015

IEEE Trans. Commun.

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Abstract-In this study, an optimal channel switching strategy is proposed for average capacity maximization in the presence of average and peak power constraints. Necessary and sufficient conditions are derived to determine when the proposed optimal channel switching strategy can or cannot outperform the optimal single channel strategy, which performs no channel switching. Also, it is obtained that the optimal channel switching strategy can be realized by channel switching between, at most, two different channels. In addition, a low-complexity optimization problem is derived to obtain the optimal channel switching strategy. Furthermore, based on some necessary conditions that need to be satisfied by the optimal channel switching solution, an alternative approach is proposed for calculating the optimal channel switching strategy. Numerical examples are provided to exemplify the derived theoretical results and to provide intuitive explanations.

“…1 is a cognitive radio system, in which secondary users can utilize multiple available frequency bands in the spectrum [20,21]. In such a scenario, optimal channel switching investigated in this study can be employed in order to maximize the average capacity of secondary users.…”

Section: Optimal Channel Switchingmentioning

confidence: 99%

Optimal channel switching for average capacity maximization

Sezer

2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

İnaltekin

2014

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Optimal channel switching is proposed for average capacity maximization in the presence of average and peak power constraints. A necessary and sufficient condition is derived in order to determine when the proposed optimal channel switching approach can or cannot outperform the optimal single channel approach, which performs no channel switching. Also, it is stated that the optimal channel switching solution can be realized by channel switching between at most two different channels. In addition, a low-complexity optimization problem is derived in order to obtain the optimal channel switching solution. Numerical examples are provided to exemplify the derived theoretical results.