Concept Of Cognitive Radio Research Articles

A Survey: A Cognitive Radio for Wireless Communication

As we know that for communication we require radio spectrum resources. And our spectrum is naturally limited resources. We can’t create resources but we can reuse the available resources. As earlier spectrum allocation done based on Fixed Spectrum Allocation (FSA). Due to this our spectrum is underutilized and result in spectrum scarcity. Now a days as the rapid growth of wireless technology, government regularity like FCC having a problem to satisfied the user demand. To solve this problem cognitive radio is the resent trends to over utilize the available spectrum. Cognitive radio utilizes the dynamic spectrum allocation to utilize the available spectrum resources. This paper surveys the concept of cognitive radio, overview, different sensing techniques, standard and recent advancement in research technology.

Blind Opportunistic Interference Alignment in MIMO Cognitive Radio Systems

Opportunistic interference alignment (OIA) is a technique that enables the multiple-input multiple-output (MIMO) secondary user (SU) to exploit the inherent spatial spectrum holes of the MIMO primary user's (PU) communication link while the PU transmissions remain interference free, thus generalizing the concept of interweave cognitive radio (CR) systems. A typical characteristic of an interweave technique is that, in general, no interaction between the PU and the SU systems is assumed, thus rendering infeasible, in many cases, the channel state information (CSI) requirements of the existing OIA techniques. The goal of the present paper is to propose a MIMO SU transceiver system that applies an OIA technique in a manner completely oblivious to the PU system so that both the alignment technique and the corresponding CSI estimation scheme require no interaction with the PU system. To this end, at first, a new improved OIA technique is proposed. The resulting technique requires CSI that can be estimated blindly at the SU ends and achieves better performance in several cases as it aligns the PU and SU signals to orthogonal sub-spaces at both the PU and the SU receivers. Then, a novel blind CSI estimation scheme is developed for the new OIA technique. The exact theoretical ergodic capacity of the new OIA technique is derived for the perfect CSI case. Some insightful theoretical results are also derived for the imperfect CSI case which, to the best of our knowledge, are some of the first ones in the OIA/IA literature. The performance of the proposed schemes is verified via extensive simulations.

Sub-Nyquist Sampling for Power Spectrum Sensing in Cognitive Radios: A Unified Approach

In light of the ever-increasing demand for new spectral bands and the underutilization of those already allocated, the concept of Cognitive Radio (CR) has emerged. Opportunistic users could exploit temporarily vacant bands after detecting the absence of activity of their owners. One of the crucial tasks in the CR cycle is therefore spectrum sensing and detection which has to be precise and efficient. Yet, CRs typically deal with wideband signals whose Nyquist rates are very high. In this paper, we propose to reconstruct the power spectrum of such signals from sub-Nyquist samples, rather than the signal itself as done in previous work, in order to perform detection. We consider both sparse and non sparse signals as well as blind and non blind detection in the sparse case. For each one of those scenarii, we derive the minimal sampling rate allowing perfect reconstruction of the signal's power spectrum in a noise-free environment and provide power spectrum recovery techniques that achieve those rates. The analysis is performed for two different signal models considered in the literature, which we refer to as the analog and digital models, and shows that both lead to similar results. Simulations demonstrate power spectrum recovery at the minimal rate in noise-free settings and show the impact of several parameters on the detector performance, including signal-to-noise ratio (SNR), sensing time and sampling rate.

Interference Minimization Using Cognitive Spectrum Decision for LED-ID Network

LED-ID (Light Emitting Diode-Identification) network is envisioned to be the next generation indoor wireless communication medium by which simultaneously high speed data transmission, identification, and illumination are possible. In spite of being extremely promising, it suffers from much impairment. Signals having different propagation paths can suffer from delays, and phase shifts which will eventually result interference. The probability of interference is also increased when communication links are established between a tag and several readers. Therefore it is necessary to reduce the interference in LED-ID network to ensure quality of service. It is possible to avoid interference by knowing the information about readers prior to assign the available spectrum. In this paper, we have proposed dynamic spectrum decision using cognitive radio concept. The simulation results justify that the proposed scheme is better than the conventional scheme.

Artificial Intelligence Based Model for Channel Status Prediction: A New Spectrum Sensing Technique for Cognitive Radio

The recent phenomena of tremendous growth in wireless communication application urge increasing need of radio spectrum, albeit it being a precious but natural resource. The recent technology under development to overview the situation is the concept of Cognitive Radio (CR). Recently the Artificial Intelligence (AI) tools are being considered for the topic. AI is the core of the cognitive engine that examines the external and internal environment parameters that leads to some postulations for QoS improvement. In this article, we propose a new Artificial Neural Network (ANN) model for detection of a spectrum hole. The model is trained with some pertinent features over a channel like SNR, channel capacity, bandwidth efficiency etc. The channel capacity status could be identified in a quantized index form . Some simulation results are presented.

On combating the half-duplex constraint in modern cooperative networks: protocols and techniques

A key issue that characterizes cooperative wireless networks is the half-duplex constraint (HDC), which refers to the inability of current modems to receive and transmit data in the same frequency at the same time. This hardware limitation results in inefficient use of system resources (bandwidth loss) as it requires dedicated bandwidth allocation for relay transmissions. Methods to overcome the HDC have been studied intensively in the literature of cooperative networks in recent years, and several approaches have been proposed. In this article we highlight four different techniques which combat the HDC by using existing technology. The first approach is non-orthogonal protocols, which allow the source to be active during relay transmissions. The second approach is the overlap of several relaying transmissions in order to mimic an ideal full-duplex operation. The third solution is the two-way relay channel where two sources exchange data via the assistance of a shared relay. Finally, the fourth approach incorporates cooperation on the level and uses the cognitive radio concept to enable relay transmissions during silent periods of source terminals. These techniques summarize some of the most significant HDC solutions that cover both the physical and network layers.

Cognitive radio networks: a practical perspective [Guest Editorial

Contemporary wireless systems must meet increased bandwidth requirements due to the persistent trend for higher multimedia data rates. Increased bandwidth may be achieved by developing efficient strategies for spectrum management. The cognitive radio (CR) concept proposes to push the dynamic spectrum access and efficient resource allocation beyond its traditional limits, by introducing spectrum sharing, coexistence, and cooperation among heterogeneous wireless networks. Although this approach has been recognized worldwide by standardization bodies, challenges and open issues still exist for its implementation in the real world.

Performance Evaluation of Multimedia Traffic Transmission Under Binomial and Poissonian Primary Traffics in Cognitive Radio Networks

Cognitive Radio is an enabling agile technology for communication and channels sharing in multimedia and wireless networks. The authors consider multimedia traffic transmission over Cognitive Radio (CR) networks using a progressive source coding associated to fountain codes. For a Cognitive Radio infrastructure where the spectrum is owned by Primary Users (PUs) that have Binomial and/or Poissonian traffics, Secondary Users (SUs) are allowed to share these spectral resources using the Opportunistic Spectrum Sharing feature of the Cognitive Radio concept. The objective of this paper lies in characterizing the reliability and as a result evaluating the performance of the secondary multimedia service provision under both primary traffic types in lossy Cognitive Radio environments. The authors have conducted a general analysis for many still open issues in Cognitive Radio and tackle three critical factors responsible for secondary service disruption: primary traffic interruptions, concurrent access to shared frequency bands leading to collisions and subchannels characteristics. Numerical simulations, in view of the average Spectral Efficiency, examine the performance of the multimedia transmission under the primary interruptions caused by the Binomial and the Poissonian primary applications and consider also the dynamics between the competing secondary peers in addition to subchannels fading and noise.

Non‐cooperative power control and spectrum allocation in cognitive radio networks: a game theoretic perspective

ABSTRACTThe invention of cognitive radio (CR) concept aims to overcome the spectral scarcity issues of emerging radio systems by exploiting under‐utilization of licensed spectrum. Determining how to allocate unused frequency bands among CR is one of the most important problems in CR networks. Because different CRs may have different quality‐of‐service requirements, they may have different objectives. In voice communication, high‐speed transmission is the most important factor; hence, voice radios always try to maximize their transmission rate. However, in data communication, the most important factor is the bit error rate. The data radios always try to maximize their signal‐to‐interference‐plus‐noise ratio (SINR). In this paper, two non‐cooperative games named interference minimization game and capacity maximization game, which reflect the target of data radios and voice radios, respectively, are proposed. From the simulations, after these games are applied, the average SINRs of all players at each channel are improved. The average SINR of players in each channel after applying the capacity maximization game is smaller than that after applying the interference minimization game. However, in comparison with that after applying the interference minimization game, the average capacity of players after applying capacity maximization approach is larger. Copyright © 2012 John Wiley & Sons, Ltd.

Cognitive Scout Node for Communication in Disaster Scenarios

The cognitive radio (CR) concept has appeared as a promising technology to cope with the spectrum scarcity caused by increased spectrum demand due to the emergence of new applications. CR can be an appropriate mean to establish self-organization and situation awareness at the radio interface, which is highly desired to manage unexpected situations that may happen in a disaster scenario. The scout node proposed in this paper is an extended concept based on a powerful CR node in a heterogeneous nodes environment which takes a leading role for highly flexible, fast, and robust establishment of cooperative wireless links in a disaster situation. This node should have two components: one is a passive sensor unit that collects and stores the technical knowledge about the electromagnetic environment in a data processing unit so-called “radio environment map” in the form of a dynamically updated database, and other is an active transceiver unit which can automatically be configured either as a secondary node for opportunistic communication or as a cooperative base station or access point for primary network in emergency communications. Scout solution can be viable by taking advantage of the technologies used by existing radio surveillance systems in the context of CR.

Hybrid Experiential-Heuristic Cognitive Radio Engine Architecture and Implementation

The concept of cognitive radio (CR) focuses on devices that can sense their environment, adapt configuration parameters, and learn from past behaviors. Architectures tend towards simplified decision-making algorithms inspired by human cognition. Initial works defined cognitive engines (CEs) founded on heuristics, such as genetic algorithms (GAs), and case-based reasoning (CBR) experiential learning algorithms. This hybrid architecture enables both long-term learning, faster decisions based on past experience, and capability to still adapt to new environments. This paper details an autonomous implementation of a hybrid CBR-GA CE architecture on a universal serial radio peripheral (USRP) software-defined radio focused on link adaptation. Details include overall process flow, case base structure/retrieval method, estimation approach within the GA, and hardware-software lessons learned. Unique solutions to realizing the concept include mechanisms for combining vector distance and past fitness into an aggregate quantification of similarity. Over-the-air performance under several interference conditions is measured using signal-to-noise ratio, packet error rate, spectral efficiency, and throughput as observable metrics. Results indicate that the CE is successfully able to autonomously change transmit power, modulation/coding, and packet size to maintain the link while a non-cognitive approach loses connectivity. Solutions to existing shortcomings are proposed for improving case-base searching and performance estimation methods.

Analysis of the M/M/N/N Queue with Two Types of Arrival Process: Applications to Future Mobile Radio Systems

The queueing system considered is essentially a M/M/N/N queue where two types of users compete for the N resources. The users may have different arrival and service rates and are denoted as primary or secondary users. The primary users have priority access to the resources, and three levels of priority are considered: perfect priority, partial priority, and no priority. This system models the recently developed cognitive radio concept, a methodology that has been proposed for future mobile radio systems. In this context, the primary users have certain rights to use the resources, whereas the secondary users must make opportunistic use of the resources without impacting too much on the performance of the primary users. For all priority settings, the mean number of primary and secondary users is derived as are the blocking probabilities for both users. When no priority is given to the primary user, the system collapses to a truncated form of two independent M/M/∞ queues. The product form solution for this special case is known, and, here, these results are given in a novel, compact form. In the case of nonzero priority, the dropping probability for the secondary users is also derived.

A continuous-time Markov chain model and analysis for cognitive radio networks

Cognitive radio concept has been widely researched to improve the spectrum usage efficiency. Appropriate modelling of the spectrum occupancy by both licensed and unlicensed users is necessary to do clear system analysis in a cognitive framework. In this paper, a continuous-time Markov chain model is developed to better describe the radio spectrum usage. The state space vector and the transition rate matrix that completely describe the system are obtained; a steady-state analysis is performed and the stationary state probability (SSP) vector is derived. In addition, we take into account the inaccuracy of the existing spectrum sensing model (missed opportunities), and derive an improved expression for the maximum throughput of secondary users as a function of the primary user traffic parameters and the achieved opportunity ratio (AOR). The optimum sensing period that maximises AOR is also analytically obtained. The proposed model and the derived expressions were examined through numerical analysis and compared with the existing models. This model is very general and applicable to systems with N secondary users in the vicinity of the primary user.

Cognitive Radio Bandwidth Sharing Scheme Based on the Two-way Matching Game

Bandwidth is an extremely valuable and scarce resource, and may become congested to accommodate diverse services in wireless communications. To enhance the efficiency of bandwidth usage, the concept of cognitive radio has emerged as a new design paradigm. In this paper, a new bandwidth sharing algorithm is developed for cognitive radio networks. Under dynamically changing network environments, we formulate the bandwidth sharing problem as a two-way matching game model. In addition, modified game theory is adopted to reach a near Pareto optimal solution while avoiding bandwidth inefficiency. This approach can make the system more responsive to the current network situation. With a simulation study, it is demonstrated that the proposed scheme approximates an optimized solution under widely diverse traffic load intensities.

Capacity of hybrid cognitive network with outage constraints

The concept of cognitive radio is to exploit efficiently the spectrum resources by allowing the coexistence of the primary and secondary users in the same bandwidth without interfering the performance of primary users. Three coexisting models (overlay, underlay and interleave) were presented in recent literature. In this study, the authors propose a hybrid cognitive network model with overlay and underlay models, whereby a primary link leases its fractions of transmission time to the secondary users for their cooperation (i.e. these nodes form as a virtual multiple input multiple output (VMIMO) group) under the outage constraints of the primary and secondary systems. A new cooperative protocol between primary and secondary users is presented. The authors attempt to achieve the maximum transmission capacity of the secondary users under the primary and secondary outage constraints, which depend on the secondary density in the cognitive network. This study gives the upper bound density of the secondary transmitters that are modelled as a homogeneous marked Poisson point process. The maximum density is achieved by computing an optimal set of system parameters such as power control factor of the secondary user and the dirty paper coding (DPC) parameter. Simulation results illustrate that the maximum secondary density obtained using VMIMO is superior to that obtained by direct primary transmission.

A Carrier Recovery Loop for Cognitive Radio Applications

The increasing demands for wireless communication, especially in consumer electronics applications, result in substantially and continuously increasing reliability and quality of service (QoS) requirements. This trend creates a need to introduce intelligent functionalities in the wireless devices, which leads to the concept of cognitive radio (CR) technology. In some CR applications such as dynamic spectrum access (DSA), the CR terminal should be able to modify its transmission parameters in order to communicate with an efficient utilization of the spectrum resource. In such a case, the CR terminal would be capable of reconfiguring itself with minimum supplementary information to achieve best performance. In this paper we propose a blind carrier recovery loop with respect to the modulation scheme suited to CR applications. Unlike conventional solutions which use a separate modulation identification device before performing carrier recovery, the introduced loop employs a hierarchical symbol decision to achieve phase lock, and then the S-curve and the variance of a decision directed phase error detector are used to extract an information about the modulation scheme of the incoming signal. After the phase lock with the hierarchical decision, the constellation used in the received signal is detected, and then the true decisions are used to drive the recovery loop. Results obtained with different digital linear modulations (8-PSK, 16-QAM 16-APSK, 64-QAM) indicate that the introduced loop is capable of achieving a real-time modulation scheme detection as well as keeping phase lock for adaptive modulation scheme transmissions.

A Cooperative Spectrum Sensing Technique with Dynamic Frequency Boundary Detection and Information-Entropy-Fusion for Primary User Detection

The invention of cognitive radio concept is aimed to overcome the spectral scarcity issues of emerging radio systems by exploiting under-utilization of licensed spectrum. As the cognitive users (secondary users) are only allowed to use a licensed spectrum in the absence of its rightful owner, the ability to accurately sense the presence of the rightful owners (primary users) is highly essential. The traditional way of having individual secondary users perform their own spectrum sensing is vulnerable to the presence of noise and shadowing of propagation channel. Cooperative spectrum sensing emerges as an attractive alternative that exploits the inherent geospatial diversity of multiple cognitive radios to enhance the robustness of sensing accuracy. Two specific issues in cooperative spectrum sensing are discussed in this paper. The first issue is on dynamic detection of primary user’s bands. A dynamic band clustering (DBC) algorithm that uses K-means clustering technique is proposed in this paper. The proposed algorithm reduces the number of erroneous narrow subbands resulting from spurious noise. This in turn minimizes the number of subbands to be detected and hence the overall sensing time. The second issue is on reducing the overheads required to facilitate fusion center operation. A novel entropy-based maximal ratio combining for decision-fusion center is also proposed in this paper. Based on extensive simulation studies, the proposed fusion technique is shown to be comparable to conventional information-fusion techniques. The performance offered by the proposed technique is achieved with significant reduction in the bandwidth overheads.

Cognitive radio: Ten years of experimentation and development

The year 2009 marked the 10th anniversary of Mitola and Maguire Jr. introducing the concept of cognitive radio. This prompted an outpouring of research work related to CR, including the publication of more than 30 special issue scientific journals and more than 60 dedicated conferences and workshops. Although the theoretical research is blooming, with many interesting results presented, hardware and system development for CR is progressing at a slower pace. We provide synopses of the commonly used platforms and testbeds, examine what has been achieved in the last decade of experimentation and trials relating to CR, and draw several perhaps surprising conclusions. This analysis will enable the research community to focus on the key technologies to enable CR in the future.

Cognitive Radio Concept and Challenges in Dynamic Spectrum Access for the Future Generation Wireless Communication Systems

Recently, the Dynamic Spectrum Access (DSA) techniques are proposed to solve the problem of spectrum scarcity and help to use the limited spectrum resource as effectively as possible. The current o...

Advances in cognitive radio networks: A survey

With the rapid deployment of new wireless devices and applications, the last decade has witnessed a growing demand for wireless radio spectrum. However, the fixed spectrum assignment policy becomes a bottleneck for more efficient spectrum utilization, under which a great portion of the licensed spectrum is severely under-utilized. The inefficient usage of the limited spectrum resources urges the spectrum regulatory bodies to review their policy and start to seek for innovative communication technology that can exploit the wireless spectrum in a more intelligent and flexible way. The concept of cognitive radio is proposed to address the issue of spectrum efficiency and has been receiving an increasing attention in recent years, since it equips wireless users the capability to optimally adapt their operating parameters according to the interactions with the surrounding radio environment. There have been many significant developments in the past few years on cognitive radios. This paper surveys recent advances in research related to cognitive radios. The fundamentals of cognitive radio technology, architecture of a cognitive radio network and its applications are first introduced. The existing works in spectrum sensing are reviewed, and important issues in dynamic spectrum allocation and sharing are investigated in detail.