Utilization Of Radio Spectrum Research Articles

A novel approach to spectrum management in cognitive radio networks using agent coalition formation

Cognitive radio CR is a novel technology which uses an open spectrum allocation technique to make more efficient utilisation of the wireless radio spectrum and reduces the bottleneck on the frequency bands. In this paper, we develop a novel approach for spectrum allocation using a multiagent system method based on coalition that enables secondary user devices to work cooperatively with their neighbouring primary user devices. The fundamental aspect of our solution is the deployment of an agent on each device and these agents are grouped into coalitions where the powerful node is selected to be a leader. The leader of secondary user's coalition organises the allocation requests based on their priorities using scheduling heuristics while the leader of primary user's coalition handles the proposals for spectrum sharing. The simulation results confirm the intelligent management and the good performance of our approach.

Spectrum sensing challenges: blind sensing and sensing optimization

By any measure, wireless communications is one of the most evolving fields in engineering. This, in return, has imposed many challenges, especially in handling the hunger for higher data rates in the next generation wireless networks. Among these challenges is how to provide the needed resources in terms of the electromagnetic radio spectrum for these networks. In this regard, cognitive radio (CR) based on dynamic spectrum access (DSA) has been attracting huge attention as a promising solution for more efficient utilization of the available radio spectrum. DSA is based on finding and opportunistically accessing the free-of-use portions of spectrum. To facilitate DSA, spectrum sensing can be used. However, spectrum sensing faces many challenges in different aspects. Such aspects include blind sensing and sensing optimization, which are both to a great extent measurement challenges. We discuss different contributions in addressing these two challenges in this article.

Power and Contention Control Scheme: As a Good Candidate for Interference Modeling in Cognitive Radio Network

Due to the ever growing need for spectrum, the cognitive radio (CR) has been proposed to improve the radio spectrum utilization. In this scenario, the secondary users (SU) are permitted to share spectrum with the licensed primary users (SU) with a strict condition that they do not cause harmful interference to the cognitive network. In this work, we have proposed an interference model for cognitive radio network that utilizes power or contention control interference management schemes. We derived the probability density function (PDF) with the power control scheme, where the power of transmission of the CR transmitter is guided by the power control law and also with contention control scheme that has a fixed transmission power for all CR transmitter controlled by a contention control protocol. This protocol makes a decision on which CR transmitter can transmit at any point in time. In this work, we have shown that power and contention control schemes are good candidates for interference modeling in cognitive radio system. The impact of the unknown location of the primary receiver on the resulting interference generated by the CR transmitters was investigated and the results shows that the challenges of the hidden primary receivers lead to higher CR-primary interference in respect to higher mean and variance. Finally, the presented results show power control and the contention control scheme are good candidates in reducing the interference generated by the cognitive radio network.

Learning System for Proactive Pre-emptive Unified Spectrum Handoff (PRO-PUSH) in Cognitive Radio Mobile Ad Hoc Networks

The aim of this study is to introduce a conceptual framework for the new approach Intelligent Proactive Pre-emptive Unified Spectrum Handoff (IP PRO-PUSH) algorithm is presented, which is a highly potential intelligent technology to intelligently address the spectrum scarcity challenges in Cognitive Radio Mobile Ad hoc Networks (CR-MANETs). The fact that spectrum is a limited natural resource poses technology challenge to ensure the available frequency is used efficiently and able to cope with new services which definitely requires more bandwidth in the future. However, over the past years, traditional approaches to spectrum management have been challenged by new insights into actual use of spectrum. In order to improve the utilization of the overall radio spectrum, the Cognitive Radio (CR) is a useful solution to this low utilization of the radio spectrum. The variation in spectrum band is called spectrum mobility. The objective of the current study is to investigate the Intelligent-Based (IB) cognitive radio learning for IP Pro-PUSH and local routing based on spectrum mobility in mobile Cognitive Radio Ad hoc Networks (CR-MANET) along with a conceptual framework and its connections.

Cross-layer Video Streaming Mechanism over Cognitive Radio Ad hoc Information Centric Networks

With the increasing number of the wireless and mobile networks, the way that people use the Internet has changed substantively. Wireless multimedia services, such as wireless video streaming, mobile video game, and mobile voice over IP, will become the main applications of the future wireless Internet. To accommodate the growing volume of wireless data traffic and multimedia services, cognitive radio (CR) and Information-Centric Network (ICN) have been proposed to maximize the utilization of wireless spectrum and improve the network performance. Although CR and ICN have high potential significance for the future wireless Internet, few studies have been conducted on collaborative operations of CR and ICN. Due to the lack of infrastructure support in multi-hop ad hoc CR networks, the problem is more challenging for video streaming services. In this paper, we propose a Cross-layer Video Streaming Mechanism (CLISM) for Cognitive Radio Ad Hoc Information Centric Networks (CRAH-ICNs). The CLISM included two distributed schemes which are designed for the forwarding nodes and receiving nodes in CRAH-ICNs. With the cross-layer approach, the CLISM is able to self-adapt the variation of the link conditions without the central network controller. Experimental results demonstrate that the proposed CLISM efficiently adjust video transmission policy under various network conditions.

Cognitive Radio Ad-Hoc Network Architectures: A Survey

Combating the growing necessity of radio spectrum, which is a limited natural resource, proper utilization of the radio spectrum is a must. Cognitive radio network (CRN) plays a vibrant role to solve this spectrum scarcity problem. Cognitive radio uses an open spectrum allocation technique to make more efficient utilization of the wireless radio spectrum and reduces the bottleneck on the frequency bands. Thus, accessible spectrum information is required for communication in CRN, which can be acquired by using spectrum database or by spectrum sensing. In addition, a robust architecture with appropriate communication protocol is preconditioned in the deployment of CRN. The state of the art of cognitive radio ad-hoc network architecture is surveyed in this paper, where the paper specifies the formation mechanisms and performance evaluations of the studied architectures. The reviewed papers have addressed some vital issues for the concrete deployment of cognitive radio ad-hoc network; however, there remain some issues that need to be addressed. Thus, this paper conveys a thorough and abstract understanding of cognitive radio ad-hoc network architecture, and also points out some open research issues in this area.

A Survey on Dynamic Spectrum Access via Cognitive Radio: Taxonomy, Requirements, and Benefits

Conventionally, interference protection among radio spectrum users is guaranteed through a policy of spectrum licensing that provides exclusive access to licensed users. However, as it is becoming extremely difficult to satisfy the growing demand for radio spectrum with this conventional policy, a flexible policy that can improve radio spectrum access and utilization without causing interference amongst users has recently gained increasing interest. In this context, this paper presents a comprehensive survey on flexible radio spectrum management with full focus on a cognitive radio technology application for dynamic spectrum access. The study approach involves analytical evaluation of the performance of the current fixed radio spectrum allocation policy examining both technical and economic perspectives. The result of which shows that the current fixed radio spectrum management policy is too rigid, inefficient and out-dated and needed to be replaced with a flexible radio spectrum management policy. Based on this analytical result, an in-depth survey on innovative technology and standards for a dynamic spectrum management model that can enhance an increase in spectral utilization and coexistence of multiple radios with adequate interference free communication was carried out. The paper also discusses the interrelationship between technologies, business and policies for cognitive radio standardization for seamless wireless communication. In addition, the paper presents both the technical and economic benefits of the dynamic radio spectrum management model over the current fixed radio spectrum allocation policy. The paper was finally concluded recommending the commercial adoption of dynamic spectrum access worldwide keeping in mind all the benefits of the dynamic spectrum access model and standards in place to ensure interference free communication in a cognitive radio environment.

QoS-Driven Power Allocation Under Peak and Average Interference Constraints in Cognitive Radio Networks

Efficient radio spectrum utilization can be improved using cognitive radio technology. In this work, we consider a spectrum underlay cognitive radio system operating in a fading environment. We propose an efficient power control scheme that maximizes the effective capacity of the secondary user, provisioning quality of service while on the same time the communication of the primary user is guaranteed through interference constraints. The specific power allocation scheme uses a policy in which the outage events of the primary user are exploited leading to a significant increase of the secondary user's effective capacity. Moreover, the interference of the primary link to the secondary is taken into account so as to study a more realistic scenario. In order to safeguard primary user's communication, two types of restrictions are considered: the traditional interference power constraint and the proposed inverse signal to interference plus noise ratio constraint. Different scenarios depending on the nature of the constraints (peak/average) are studied and their impact on the performance of the primary and secondary users is investigated. The superiority of the proposed schemes is demonstrated through their comparison with two reference power control schemes. Finally, numerical calculations, validated with simulation results, confirm the theoretical analysis and evaluate the performance of the proposed scheme for all the different scenarios.

Heterogeneous next‐generation wireless network interference model—and its applications

ABSTRACTNext‐generation wireless systems facilitating better utilisation of the scarce radio spectrum have emerged as a response to inefficient and rigid spectrum assignment policies. These are comprised of intelligent radio nodes that opportunistically operate in the radio spectrum of existing primary systems, yet unwanted interference at the primary receivers is unavoidable. In order to design efficient next‐generation systems and to minimise the adverse effect of their interference, it is necessary to realise how the resulting interference impacts the performance of the primary systems. In this work, a generalised framework for the interference analysis of such a next‐generation system is presented where the next‐generation transmitters may transmit randomly with different transmit powers. The analysis is built around a model developed for the statistical representation of the interference at the primary receivers, which is then used to evaluate various performance measures of the primary system. Applications of the derived interference model in designing the next‐generation network system parameters are also demonstrated. Such approach provides a unified and generalised framework, the use of which allows a wide range of performance metrics can be evaluated. Findings of the analytical performance analyses are confirmed through extensive computer‐based Monte‐Carlo simulations. Copyright © 2014 John Wiley & Sons, Ltd.

Specification of a Convergent Referential Platform for the New Generation of Wireless Networks

Worldwide, dozens of initiatives are under way to redesign the Internet, aiming to better meet information society needs in the next decades. These efforts are collectively called “future Internet” research. Meanwhile, in the scope of wireless digital communication systems, the research advances to increase radiofrequency spectrum utilization, as well as to create platforms that facilitate migration to new technologies and protocols. The new generation wireless terminals should learn from the radio environment, selecting the best communication channels available and avoiding interference with licensed users. These terminals are called “cognitive radio”. In this paper, technologies from both fronts are integrated to create a reference model where the cognitive radio is merged with the wireless terminal requirements of the future Internet. The paper presents and analyzes the previous work related to the proposed reference model, qualitatively comparing several efforts with this one, in order to determine the benefits of the adopted synergistic approach.Worldwide, dozens of initiatives are under way to redesign the Internet, aiming to better meet information society needs in the next decades. These efforts are collectively called “future Internet” research. Meanwhile, in the scope of wireless digital communication systems, the research advances to increase radiofrequency spectrum utilization, as well as to create platforms that facilitate migration to new technologies and protocols. The new generation wireless terminals should learn from the radio environment, selecting the best communication channels available and avoiding interference with licensed users. These terminals are called “cognitive radio”. In this paper, technologies from both fronts are integrated to create a reference model where the cognitive radio is merged with the wireless terminal requirements of the future Internet. The paper presents and analyzes the previous work related to the proposed reference model, qualitatively comparing several efforts with this one, in order to determine the benefits of the adopted synergistic approach.

Ergodic and outage capacity maximization of cognitive radio networks in cooperative relay environment using optimal power allocation

Cognitive radio solves the problem of scarcity of radio spectrum to a great extent in that it allows unlicensed users to coexist with licensed users. It allows effective utilization of radio spectrum by offering radio cells the ability of radio sensing and dynamic spectrum sharing. The throughput of spectrum sharing cognitive radio can be maximized by performing data transmission and spectrum sensing at the same time. Cooperative communications and networking allow distributed terminals in a wireless network. The main problem with cognitive radio is to sense the presence of primary users over a wide range of spectrum. Cooperative spectrum sensing is used here to detect those users more reliably. It is investigated whether cooperative communication for spectrum in cognitive radio enhances the efficiency of spectrum sharing. The maximum power that can be adapted by the secondary user without causing significant interference to a primary user is investigated. An algorithm is proposed for the same. Closed-form expression for ergodic throughput is derived for the systems and is compared with the conventional cognitive radio system. An expression for the outage capacity of the system is also derived for average transmit and interference power constraints under truncated channel information with fixed rate technique.

Performance Analysis of IEEE 802.22 WRAN over Rayleigh fading channel with & without convolution coding

The spectrum available for the wireless services is limited; the increased demand of wireless application has put a lot of constraints on the utilization of available radio spectrum. For the efficient spectrum utilization for wireless application IEEE 802.22 standard wireless regional area network (WRAN)) is developed, which is based on cognitive radio technique that senses the free available spectrum. In this work we are evaluating the performance of WRAN over physical layer by using QPSK modulation over Rayleigh fading channel and obtaining the bit error rate (BER) curves. Further we are reducing the BER for a lesser value of signal to noise ratio (SNR) so that the BER performance of the system is improved.

Systematic comparison of performance of different Adaptive beam forming Algorithms for Smart Antenna systems

Smart antenna is the most efficient leading innovation for maximum capacity and improved quality and coverage. Efficient utilization of limited radio frequency spectrum is only possible to use smart/adaptive antenna system. Smart antenna radiates not only narrow beam towards desired users exploiting signal processing capability but also places null towards interferers, thus optimizing the signal quality and enhancing capacity. Smart antennas exploit space diversity to help provide high data rates, increased channel capacity, and improved quality of service. A systematic comparison of the performance of different Adaptive Algorithms for beam forming for Smart Antenna System has been extensively studied in this research work. Simulation results revealed that training sequence algorithms like Recursive Least Squares (RLS) and Least Mean Squares (LMS) are best for beam forming (to form main lobes) towards desired user but they have limitations towards interference rejection. While Constant Modulus Algorithm (CMA) has satisfactory response towards beam forming and it gives better outcome for interference rejection, but Bit Error Rate (BER) is maximum in case of single antenna element in CMA. The effect of changing step size for LMS algorithm has also been studied. Index Terms: Adaptive antenna systems, Constant modulus algorithm, Least mean squares, Smart antenna.

Spectrally encoded code‐division multiple access for cognitive radio networks

Recent studies have revealed that spectrum congestion is due to the inefficient usage of spectrum against the availability. Cognitive radio is viewed as an approach for improving the utilisation of radio spectrum. The spectrally encoded (spread-time) code-division multiple access (SE-CDMA) technique (which is regarded as the dual of spread spectrum CDMA) is considered and its performance in cognitive radio networks is studied. In cognitive network spectrum, overlay and underlay techniques are employed to enable the primary and secondary users to coexist while improving the overall spectrum efficiency. It is shown that SE-CDMA provides considerable flexibility to design overlay and underlay waveforms that are scenario-dependent. The performance of SE-CDMA method is evaluated in additive white Gaussian noise and fading channels in terms of both primary and secondary users. Moreover, its performance is compared with cognitive radio using soft-decision spectrally modulated spectrally encoded waveforms. The results indicate the efficiency of SE-CDMA.

Market mechanisms for cooperative spectrum trading with incomplete network information

Wireless spectrum is very valuable but currently heavily under-utilized. Cooperative spectrum trading encourages primary licensed users and secondary unlicensed users to exchange money or resources to achieve a win-win situation, and can significantly increase the utilization of wireless spectrum. In this article, we discuss various market mechanisms that facilitate cooperative spectrum trading with incomplete network information. We introduce mechanisms including pricing, bargaining, contract, and auction, and demonstrate the applicability using a concrete example of resource-exchange cooperative spectrum trading. We also outline various open issues in this emerging interdisciplinary research area.

A local joint fast handoff scheme in cognitive wireless mesh networks

ABSTRACTA cognitive wireless mesh (CogMesh) network can provide network access for users (mesh clients) while holding the open spectrum‐sharing feature. It combines the advantages of both cognitive radio networks and wireless mesh networks: high utilization of the scarce radio spectrum, ease of deployment, maintenance, and low cost. However, the unstable radio environment incurs more handoffs in CogMesh than other wireless networks. Therefore, seamless handoff and a lightweight re‐authentication process are required to achieve a high quality of real‐time applications and low network load caused by re‐authentication. In this paper, we introduce a local joint fast handoff scheme based on proxy signature, which is suitable for CogMesh scenarios. After the mutual authentication between a mesh client and a mesh router, a session tunnel key is derived and shared between them to protect their sessions. Because the proxy signature is used, the IEEE 802.1x authentication architecture remains the same, and there is no need for the authentication server to be involved in the handoff procedure, the re‐authentication delay has been reduced, and the load of CogMesh and the authentication server are lower. Copyright © 2013 John Wiley & Sons, Ltd.

Least Mean Square (LMS) for Smart Antenna

The demand for increased capacity in wireless communication networks has motivated recent research activities toward wireless systems that exploit the concept of smart antenna and space selectivity. Efficient utilization of limited radio frequency spectrum is only possible to use smart/adaptive antenna system. Smart antenna radiates not only narrow beam towards desired users exploiting signal processing capability but also places null towards interferers, thus optimizing the signal quality and enhancing capacity. We analysis the performance of adaptive (LMS) algorithm for smart antenna systems which is very important for smart antenna design. The SA incorporates this algorithm in coded form which calculates complex weights according to the signal environment. The performance of LMS algorithm is compared on the basis of normalized array factor and Mean Square Error (MSE) for SA systems. It is observed that an LMS algorithm is converging after 50 iteration.

Radio Planning and Field Trial Measurement of a Deployed 4G WiMAX Network in an Urban Sub-Saharan African Environment

Worldwide Interoperability for Microwave Access (WiMAX) technology has gained growing interest due to its applications and advantages. It is fast emerging as a last-mile problem solution for broadband access technology. This paper presents operation scenarios for the deployment of a Fourth Generation (4G) WiMAX system in a typical sub-Saharan African environment. This has been specified based on real world conditions considering the regulatory rules specified by the National Communication Authority (NCA) for radio frequency spectrum utilization in the 2.6GHz licensed band in Ghana. Appropriate propagation models and Network planning tools have been used to design the final radio network plan. Coverage prediction has been performed using Genex-U-Net to achieve the main aim of providing coverage in the predefined areas of Accra and Tema, Ghana. Simulation results for different downlink/uplink ratios with different frequency reuse schemes have been presented. A total of 11 base stations have been suggested to provide coverage of -92dBm using 32 sectors 4 transmit 4 receive (4T4R) adaptive Multi-Input Multi-Output (MIMO) antenna configuration within the Accra and Tema municipality. Finally the system performance is evaluated through field trial measurement and the results presented.

Study on Energy Detection-based Cooperative Sensing in Cognitive Radio Networks

Cognitive radio (CR) technology aims to achieve efficient radio spectrum utilization based on overlay spectrum sharing. Therefore, one of the main requirements of CR systems is the capability to detect and sense the presence of primary transmissions. However, sensing is affected by the behavior of the wireless channel, i.e., hidden node, interference, shadowing, and fading, which may result in wrong detection decisions. Consequently, CRs may introduce harmful interference to primary radios. Cooperative spectrum sensing can improve detection decisions by obtaining sensing information from different sources, which has been recently proposed to overcome this problem. This paper reviews cooperative sensing aspects, approaches, architecture, as well as problematic aspect and drawbacks of the control channel and associated fusion methods.

A stochastic game framework for joint frequency and power allocation in dynamic decentralized cognitive radio networks

Cognitive radio networks (CRNs) have been recognized as a promising solution to improve the radio spectrum utilization. This article investigates a novel issue of joint frequency and power allocation in decentralized CRNs with dynamic or time-varying spectrum resources. We firstly model the interactions between decentralized cognitive radio links as a stochastic game and then proposed a strategy learning algorithm which effectively integrates multi-agent frequency strategy learning and power pricing. The convergence of the proposed algorithm to Nash equilibrium is proofed theoretically. Simulation results demonstrate that the throughput performance of the proposed algorithm is very close to that of the centralized optimal learning algorithm, while the proposed algorithm could be implemented distributively and reduce information exchanges significantly.