Interweave Cognitive Radio System Research Articles

Benefits of Improper Gaussian Signaling in Interweave Cognitive Radio With Full and Partial CSI

In this paper, we investigate the impact of using improper Gaussian signaling (IGS) scheme on the interweave cognitive radio (CR) paradigm when the cognitive user has access to full or partial channel-state-information (CSI). Throughout this work, we analyze the performance of both the primary user (PU) and secondary user (SU) in terms of instantaneous achievable rate and outage probability, for given sensing and detection capabilities. Then, we optimize the IGS scheme for full and partial CSI scenarios to maximize the achievable rate of the SU while maintaining a minimum quality-of-service (QoS) requirement for the PU. Meanwhile, we derive the corresponding feasibility conditions for the interweave cognitive radio system operation. IGS based systems are proven to provide notable gain over the conventional proper Gaussian signaling, which is considered our benchmark scheme. The IGS scheme is observed to be further beneficial at low SU detection capabilities, strong interference from the cognitive user to the licensed user, and low gain of the PU direct link.

Cognitive radio-based solutions for spectrum scarcity in Palestine

In this paper, we study the feasibility of implementing cognitive radio (CR) secondary network either on the primary Palestinian second generation (2G) global system for mobile communication (GSM) network or on the ultra-high frequency (UHF) television (TV) band. Particularly, we propose solutions for spectrum scarcity based on the three CR paradigms, namely: interweave CR, underlay CR, and overlay CR. In the first solution, an interweave CR system is suggested to efficiently utilise the so-called TV white spaces in the UHF TV band allocated for Palestine. In the second solution, an underlay CR system based on code division multiple access (CDMA) is introduced to underlay the primary GSM system. In the third solution, an overlay CR system is proposed based on orthogonal frequency division multiplexing (OFDM) to share the same spectrum band with the primary GSM system. It is confirmed that the proposed solutions can solve the spectrum scarcity and limit the interference levels, and consequently improve system capacity.

A New Interweave Cognitive Radio Scheme for Out-Band Energy Harvesting Systems

In this paper, a new interweave cognitive radio (CR) transmission scheme is analytically presented for energy harvesting (EH)-enabled transmitting nodes. The EH is performed via a dedicated power beacon (PB) base station through wireless power transfer, which harvests energy to both primary and secondary systems. The out-band mode-of-operation between PB and the two heterogeneous systems is considered, i.e., data communication and EH are realized at different frequency bands and asymmetric (non-equal) time durations. The performance of the new interweave CR system is studied under independent and not necessarily identically distributed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\kappa -\mu $ </tex-math></inline-formula> shadowed faded channels. Representative numerical and simulation results corroborate the effectiveness of the proposed scheme and presented analysis, while some useful engineering insights are provided.

Diversity-Multiplexing Tradeoff in an Interweave Multiuser Cognitive Radio System

In an interweave cognitive radio system, the spectrum sensing performance affects the rate and reliability of data transmission. In wireless communications, the tradeoff between the reliability and data rate can be evaluated by diversity-multiplexing tradeoff (DMT) analysis. In this paper, through the analysis of the error probability at the secondary receiver, we derive the DMT for the multiple-access channel and user-selection schemes in an interweave multiuser cognitive radio system considering the spectrum sensing effect on the rate and reliability. We show that the DMT of the system can be improved by cooperative spectrum sensing. Simulations also approve our analytical results.

Joint Sensing and Reception Design of SIMO Hybrid Cognitive Radio Systems

In this paper, the problem of joint design of spectrum sensing (SS) and receive beamforming, with reference to a cognitive radio (CR) system, is considered. The aim of the proposed design is the maximization of the achievable average uplink rate of a secondary user, subject to an outage-based quality-of-service constraint for primary communication. A hybrid CR system approach is studied, according to which the system either operates as an interweave (i.e., opportunistic) or as an underlay (i.e., spectrum sharing) CR system, based on SS results. A realistic channel state information framework is assumed, according to which the direct channel links are known by the multiple antenna receivers, while merely statistical (covariance) information is available for the interference links. A new closed-form approximation is derived for the outage probability of primary communication, and the problem of rate-optimal selection of SS parameters and receive beamformers is addressed for hybrid, interweave, and underlay CR systems. It is proved that our proposed system design outperforms both underlay and interweave CR systems for a range of system scenarios.

Cognitive Radios Exploiting Gray Spaces via Compressed Sensing

AbstractWe suggest an interweave cognitive radio system with a

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

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.

An opportunistic channel access scheme for interweave cognitive radio systems

We propose a novel opportunistic access scheme for cognitive radios in an interweave cognitive system, that considers the channel gain as well as the predicted idle channel probability (primary user occupancy: Busy/idle). In contrast to previous work where a cognitive user vacates a channel only when that channel becomes busy, the proposed scheme requires the cognitive user to switch to the channel with the next highest idle probability if the current channel's gain is below a certain threshold. We derive the threshold values that maximize the long term throughput for various primary user transition probabilities and cognitive user's relative movement.

Distributed Exploitation of Spectrum and Channel State Information for Channel Reservation and Selection in Interweave Cognitive Radio Networks

A channel-and-sensing-aware channel access (CSCA) policy is proposed for multi-channel interweave cognitive radio systems, where multiple secondary users (SUs) are competing for transmission to a common access point. The proposed CSCA policy consists of two key elements: (i) a decentralized channel selection policy that allows each SU to utilize knowledge of both the spectrum occupancy information and its local channel state information to make local channel access decisions and (ii) a channel reservation policy that allows each SU to compete for use of its selected channel by emitting short reservation packets at the beginning of each frame. In the reservation period, a channel-aware splitting algorithm is utilized to resolve collision among SUs that are competing for the same channel. The splitting procedure is optimized with respect to SUs' channel selection policy and ensures that the SU with the best channel quality prevails when collision is resolved. The CSCA policy is derived with the goal of maximizing the SU's throughput subject to a constraint on the probability of collision with primary users (PUs). To satisfy the collision probability constraint, a minimum channel gain threshold is set on each channel to limit the probability that the channel is accessed by SUs. An iterative algorithm is proposed to optimize the parameters in the channel selection and reservation policies, and a low-complexity policy is devised for use in systems with large numbers of channels. The proposed CSCA policies allow SUs to exploit optimally the tradeoff between spectrum availability and channel quality.