Quantitative Comparison of Agile Modulation Techniques for Cognitive Radio Transceivers

Rajbanshi, Rakesh; Chen, Qi; Wyglinski, Alexander M.; Minden, Gary J.; Evans, Joseph

doi:10.1109/ccnc.2007.230

Cited by 50 publications

(30 citation statements)

References 9 publications

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“…In a CR network, interference between MC-CDMA based secondary users and primary users can be avoided by using the subcarrier deactivation technique, similar to Non-Contiguous OFDM (NC-OFDM) and such schemes are called Non-Contiguous MC-CDMA (NC-MC-CDMA). Rajbanshi et al [47] investigated the performance of NC-OFDM and NC-MC-CDMA techniques for CR transceivers and made the following conclusions. With respect to PAPR, NC-OFDM exhibits the same problem as the conventional OFDM, while in MC-CDMA PAPR is reduced through frequency domain spreading.…”

Section: Mc-cdmamentioning

confidence: 99%

Multicarrier Spread Spectrum Modulation Schemes and Efficient FFT Algorithms for Cognitive Radio Systems

Sundararajan

Govindaswamy

2014

Electronics

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Spread spectrum (SS) and multicarrier modulation (MCM) techniques are recognized as potential candidates for the design of underlay and interweave cognitive radio (CR) systems, respectively. Direct Sequence Code Division Multiple Access (DS-CDMA) is a spread spectrum technique generally used in underlay CR systems. Orthogonal Frequency Division Multiplexing (OFDM) is the basic MCM technique, primarily used in interweave CR systems. There are other MCM schemes derived from OFDM technique, like Non-Contiguous OFDM, Spread OFDM, and OFDM-OQAM, which are more suitable for CR systems. Multicarrier Spread Spectrum Modulation (MCSSM) schemes like MC-CDMA, MC-DS-CDMA and SS-MC-CDMA, combine DS-CDMA and OFDM techniques in order to improve the CR system performance and adaptability. This article gives a detailed survey of the various spread spectrum and multicarrier modulation schemes proposed in the literature. Fast Fourier Transform (FFT) plays a vital role in all the multicarrier modulation techniques. The FFT part of the modem can be used for spectrum sensing. The performance of the FFT operator plays a crucial role in the overall performance of the system. Since the cognitive radio is an adaptive system, the FFT operator must also be adaptive for various input/output values, in order to save energy and time taken for execution. This article also includes the various efficient FFT algorithms proposed in the literature, which are suitable for CR systems.

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Section: Mc-cdmamentioning

confidence: 99%

Multicarrier Spread Spectrum Modulation Schemes and Efficient FFT Algorithms for Cognitive Radio Systems

Sundararajan

Govindaswamy

2014

Electronics

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“…The logical channel is treated as if it were a single channel whose capacity is equal to the sum of all licensed channels merged into it. This can be done by using the OFDM technique with selective allocation of subcarriers to the channels to be utilized [12], [13], [14]. In this way, more than one (possibly nonadjacent) channel in the logical channel can be simultaneously utilized by a single SU.…”

Section: Opportunity-usage Modelmentioning

confidence: 99%

“…This can be done by the Orthogonal Frequency Division Multiplexing (OFDM) technique with adaptive and selective allocation of OFDM subcarriers to utilize any subset of N licensed channels at the same time [12], [13], [14]. Note that equipping each SU with more than one antenna might cause severe interference among its antennas, thus degrading the SU's performance [15].…”

Section: Network Topologymentioning

confidence: 99%

Efficient Discovery of Spectrum Opportunities with MAC-Layer Sensing in Cognitive Radio Networks

Kim

Shin

2008

IEEE Trans. on Mobile Comput.

676

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Abstract-Sensing/monitoring of spectrum-availability has been identified as a key requirement for dynamic spectrum allocation in cognitive radio networks (CRNs). An important issue associated with MAC-layer sensing in CRNs is how often to sense the availability of licensed channels and in which order to sense those channels. To resolve this issue, we address 1) how to maximize the discovery of spectrum opportunities by sensing-period adaptation and 2) how to minimize the delay in finding an available channel. Specifically, we develop a sensing-period optimization mechanism and an optimal channel-sequencing algorithm, as well as an environmentadaptive channel-usage pattern estimation method. Our simulation results demonstrate the efficacy of the proposed schemes and its significant performance improvement over nonoptimal schemes. The sensing-period optimization discovers more than 98 percent of the analytical maximum of discoverable spectrum-opportunities, regardless of the number of channels sensed. For the scenarios tested, the proposed scheme is shown to discover up to 22 percent more opportunities than nonoptimal schemes, which may become even greater with a proper choice of initial sensing periods. The idle-channel discovery delay with the optimal channel-sequencing technique ranges from 0.08 to 0.35 seconds under the tested scenarios, which is much faster than nonoptimal schemes. Moreover, our estimation method is shown to track time-varying channel-parameters accurately.

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“…We assume that the pool of idle channels is treated as one logical channel, whose capacity is equal to m Á C bandwidth-units. This can be realized by the Orthogonal Frequency Division Multiplexing (OFDM) techniques with adaptive and selective allocation of OFDM subcarriers, like Noncontiguous OFDM (NC-OFDM) proposed in [19].…”

Section: Channel Modelmentioning

confidence: 99%

Admission and Eviction Control of Cognitive Radio Users at Wi-Fi 2.0 Hotspots

Kim

Shin

2012

IEEE Trans. on Mobile Comput.

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Abstract-Cognitive radio (CR)-based Wi-Fi 2.0 hotspots are introduced as an attractive application of dynamic spectrum access (DSA), at which a wireless service provider (WSP) leases licensed channels via secondary market and offers Internet access to CRenabled customers by opportunistically utilizing the leased spectrum. The CR users access the channels only when they are temporarily unoccupied by their legacy users, and pay a usage charge according to the WSP's pricing policy. In this paper, we study the profit maximization problem of a WSP by deriving the (sub)optimal control of admission (at CR user arrivals) and eviction (upon return of the legacy users) of CR users. We formulate the problem as a semi-Markov decision process (SMDP) with two quality-ofservice (QoS) constraints on arrival-blocking and service-dropping probabilities, which is solved by the linear programming techniques. Using an extensive numerical analysis, we show that the derived policy achieves up to 22.5-44 percent more profit than simple complete-sharing algorithms in the tested scenarios. In addition, we evaluate the impact of the number of leased channels and pricing on the achieved profit, and study the tradeoffs between the two QoS constraints.

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Quantitative Comparison of Agile Modulation Techniques for Cognitive Radio Transceivers

Cited by 50 publications

References 9 publications

Multicarrier Spread Spectrum Modulation Schemes and Efficient FFT Algorithms for Cognitive Radio Systems

Multicarrier Spread Spectrum Modulation Schemes and Efficient FFT Algorithms for Cognitive Radio Systems

Efficient Discovery of Spectrum Opportunities with MAC-Layer Sensing in Cognitive Radio Networks

Admission and Eviction Control of Cognitive Radio Users at Wi-Fi 2.0 Hotspots

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