Online ISSN
1751-8636
Print ISSN
1751-8628
IET Communications
Volume 6, Issue 8, 22 May 2012
Volumes & issues:
Volume 6, Issue 8
22 May 2012
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- Author(s): D. Grace ; H. Zhang ; M. Nekovee
- Source: IET Communications, Volume 6, Issue 8, p. 783 –784
- DOI: 10.1049/iet-com.2012.0270
- Type: Article
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- Author(s): M. López-Benítez and F. Casadevall
- Source: IET Communications, Volume 6, Issue 8, p. 785 –796
- DOI: 10.1049/iet-com.2010.0571
- Type: Article
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Energy detection constitutes a preferred approach for spectrum sensing in cognitive radio owing to its simplicity and applicability (it works irrespective of the signal format to be detected) as well as its low computational and implementation costs. The main drawback, however, is its well-known detection performance limitations. Various alternative detection methods have been shown to outperform energy detection, but at the expense of increased complexity and confined field of applicability. In this context, this work proposes and evaluates an improved version of the energy detection algorithm that is able to outperform the classical energy detection scheme while preserving a similar level of algorithm complexity as well as its general applicability regardless of the particular signal format or structure to be detected. The performance improvement is evaluated analytically and corroborated with the experimental results. - Author(s): O. Habachi and Y. Hayel
- Source: IET Communications, Volume 6, Issue 8, p. 797 –804
- DOI: 10.1049/iet-com.2010.0537
- Type: Article
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The authors are interested in evaluating the performance of a cognitive radio network composed of secondary and primary mobiles, and look for optimising the decision process of the secondary mobiles when they have to choose between licensed or unlicensed channels. In fact, the system is composed of several channels where only one unlicensed channel is shared between all the secondary mobiles, when they decide to use this particular channel. As the secondary mobiles are equipped with cognitive radios, they are able to sense the licensed channels and use one of them if it is free. The authors consider first the global system and look for the optimal proportion of secondary mobiles that sense the licensed channels in order to optimise an average performance of the system. Second, the authors assume that each secondary mobile decides to sense or not the licensed channels and, are interested in an equilibrium situation as the secondary mobiles are in competition. After showing the existence and the uniqueness of equilibrium, the performance of this equilibrium is evaluated by looking at the price of the anarchy of the system. - Author(s): J. Song ; Z. Feng ; P. Zhang ; Z. Liu
- Source: IET Communications, Volume 6, Issue 8, p. 805 –809
- DOI: 10.1049/iet-com.2010.0536
- Type: Article
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Spectrum sensing is regarded as a key technology in cognitive radio (CR). Energy detector has been performed as an alternative spectrum sensing method because of its low computational complexity and not requiring a priori information of the primary signal. This study proposes an enhanced energy detector by making an arbitrary positive power operation of the received signal amplitude instead of the squaring operation in the traditional energy detector (TED). The detection probability of the proposed detector is theoretically derived under a constant false alarm probability in additive white Gaussian noise (AWGN) channels. Performance analysis and simulation results indicate that the enhanced energy detector with the optimum power operation outperforms the traditional energy detector, especially in low signal-to-noise ratio (SNR) regime. - Author(s): W.-L. Chin ; H.-C. Kuo ; H.-H. Chen
- Source: IET Communications, Volume 6, Issue 8, p. 810 –818
- DOI: 10.1049/iet-com.2010.0579
- Type: Article
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Spectrum sensing is a key enabling technique for implementing cognitive radio (CR) networks. Based on the detection of primary users’ signals, a CR can fully exploit wireless radio resources, thus to increase spectrum efficiency and allow opportunistic transmissions for secondary users. This work presents a spectrum sensing approach for its applications in a wireless regional area network (WRAN) based on features detection of advanced television systems committee (ATSC) digital TV and WRAN signals over a Rayleigh fading channel. The scheme aims at detecting and identifying both ATSC and WRAN signals. To improve spectrum sensing performance in low-signal-to-noise ratio (SNR) regions, the characteristics of both ATSC and WRAN signals are exploited in spectrum sensing algorithms based on a correlation-based feature identification approach. In this study, real working scenarios of a WRAN CR network are considered. The effectiveness of the proposed detector has been verified by simulations. - Author(s): L. Luo and S. Roy
- Source: IET Communications, Volume 6, Issue 8, p. 819 –827
- DOI: 10.1049/iet-com.2010.0554
- Type: Article
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A successful cognitive radio network (CRN) needs a fast and reliable spectrum sensing scheme to enable secondary users to utilise available channels. In this work, the authors first revisit conventional urn models for channel availability (the random independent identical distribution (i.i.d) models) and introduce a correlated Markov model which is apropos for scenarios with memory. After proposing an n-step serial search strategy, the authors investigate the performance of random and serial search schemes for the above occupancy models in terms of the mean number of steps for detection of an ‘open’ channel. The analytical results of the average detection are then presented for different sensing schemes under both random and correlated channel model. The authors then highlight a key trade-off underlying the overall mean time to detect a free channel: it is a function of both the mean number of steps and the sensing time per step. Reduced sensing duration in each step leads to lower detection probability (Pd) thereby increasing the average number of search steps required. This suggests that there exists an optimal sensing duration that minimises the overall mean detection time; this is analytically investigated (for low signal-to-noise ratio (SNR)) and verified by simulation results under various SNR environments. - Author(s): X. Wang ; W. Chen ; Z. Cao
- Source: IET Communications, Volume 6, Issue 8, p. 828 –835
- DOI: 10.1049/iet-com.2010.0639
- Type: Article
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Cognitive radio (CR) provides a promising solution to the spectrum scarcity problem by implementing opportunistic spectrum access over the licensed spectrum. However, spectrum holes are discontinuous in frequency and time, resulting in a challenge to CR transmissions. Fortunately, rateless codes can be utilised to exploit these distributed spectrum opportunities in an aggregate way. In such system, how to conduct the sensing and transmission is a key problem that affects the system performance. Therefore in this study, the authors propose a rateless-coded transmission protocol in a multi-channel CR system, addressing the media access control (MAC) layer sensing issues. Specifically, how many channels and which ones should be sensed in each time slot. Owing to the dynamics of channel availability, stochastic control is a necessity. Therefore the authors analyse the average throughput and formulate an optimisation problem to find the optimal sensing policy based on the theory of partially observable Markov decision process (POMDP). The myopic sensing policy is also studied owing to intractable computation complexity of a general POMPD. Moreover, the authors propose a heuristic policy with comparable performance and low complexity. Simulation results will show that the heuristic policy is superior to the static policy and has almost the same performance as the myopic policy. - Author(s): D.B. Rawat and D.C. Popescu
- Source: IET Communications, Volume 6, Issue 8, p. 836 –844
- DOI: 10.1049/iet-com.2010.0585
- Type: Article
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Cognitive radio (CR) technology is an emerging technique for dynamic spectrum access, which attempts to share licensed spectrum with licensed users opportunistically and dynamically to provide high bandwidth and efficient spectrum utilisation. In this study, the authors address the problem of finding combined precoder and power of CRs for dynamic spectrum sharing in interference networks. First, the authors present the precoder and power optimisation problem in spectrum underlay by considering both power and interference constraints where CR users coexist and transmit simultaneously with primary users. Then the authors particularise the problem of precoder and power adaptation to spectrum overlay where CRs operate only in idle frequency bands obtained from spectrum sensing. In the proposed approach, bandwidth use is expressed in terms of a finite set of discrete resources whose use is optimised by the CR transmitters in terms of achievable rate corresponding to individual link under operating constraints that restrict the operation of unlicensed secondary CR transmitters to protect licensed primary user transmissions. The authors formulate the optimal resource allocation for CR links as a constrained optimisation problem and solve using the Lagrange method. The authors illustrate the proposed algorithm with the help of numerical results obtained from simulations. - Author(s): A. Zarrebini-Esfahani and M.R. Nakhai
- Source: IET Communications, Volume 6, Issue 8, p. 845 –851
- DOI: 10.1049/iet-com.2010.0642
- Type: Article
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This study focuses on the problem of cell-edge user coverage in the context of cognitive radio networks operating within the vicinity of primary cell borders. Two strategies are introduced such that the primary cell-edge users get assisted by the cognitive base station (BS) to receive a consistent quality of service (QoS) because of their long distance from the primary BS. In return, the cognitive BS is rewarded by using the same spectrum that has already been allocated to the primary users’ link to serve a group of cognitive users. In the first strategy that we call cooperative, the cognitive BS relays the primary cell-edge users’ data, sent by the primary BS, through spatial multiplexing and beamforming, while transmitting towards its cognitive users. In the second strategy that we call soft interference shaping, the cognitive BS serves cognitive users as well as primary cell-edge users by spatial multiplexing and beamforming, while forming controlled nulls towards the primary users located outside but within the close vicinity of the cognitive cell border. This technique is done to avoid the interference towards the primary users surrounding the cognitive cells border. - Author(s): T.J. Harrold and M.A. Beach
- Source: IET Communications, Volume 6, Issue 8, p. 852 –860
- DOI: 10.1049/iet-com.2010.0581
- Type: Article
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The selection of optimum frequency channels by cognitive radio devices is considered challenging, particularly when such devices have to mutually co-exist and also take account of existing users of the spectrum. In addition to the problem of accurate spectrum sensing, there are additional considerations that result because of the dynamic capabilities of the terminals. Particular problems include that of allowing terminals to discover each other when they may be tuned to different frequencies, operating without a common control channel. This work has developed a spectrum access algorithm by which cognitive radio terminals monitor the available spectrum, discover each others’ presence and collaborate to select the optimum communications channel. This is achieved while avoiding interference to incumbent users. In contrast to previous work in this area, the proposed algorithm is of low complexity, requiring the terminals neither to dedicate part of their operational time to spectrum sensing, nor to periodically switch to a control channel. It is thus suitable for implementation in simple terminals. A simulation tool, which models the interaction and behaviour of the terminals, has been produced and used to test the performance of the algorithm in a demanding environment. It was shown that the algorithm permits a high level of data throughput, with protection for incumbent spectrum users. - Author(s): S. Hussain ; Y. Louët ; J. Palicot
- Source: IET Communications, Volume 6, Issue 8, p. 861 –871
- DOI: 10.1049/iet-com.2010.0531
- Type: Article
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Transmitter non-linear components cause distortions when a signal with high Peak to Average Power Ratio (PAPR) is transmitted. High PAPR is a parameter commonly associated to the multi-carrier signals like Orthogonal Frequency Division Multiplexing (OFDM) and Software Radio (SWR). Since SWR is an enabling technology for Cognitive Radio (CR), the signals demonstrate high PAPR in CR context as well. Upon opportunistic spectrum access in CR, PAPR further increases as more carriers (secondary carriers) are added in an already large numbered multi-carrier signal (primary signal). This paper explores the PAPR variations on spectrum access in CR context. Also, the reduction of PAPR in SWR and CR is performed using Tone Reservation (TR). In TR, certain carriers of the data signal are reserved to create a peak reducing signal which on addition to the data signal reduces its peak power. These carriers are called peak reducing carriers (PRC). At first, PAPR is reduced for different SWR signal scenarios. Then the influence of bandwidth, position and power of PRC on he PAPR reduction performance is discussed. Finally, CR PAPR is reduced by presenting a joint pectrum access scheme which implies a part of secondary data carriers as PRC to reduce CR PAPR. - Author(s): S. Anand ; S. Sengupta ; R. Chandramouli
- Source: IET Communications, Volume 6, Issue 8, p. 872 –882
- DOI: 10.1049/iet-com.2010.0607
- Type: Article
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The authors present a distributed channel acquisition mechanism in dynamic spectrum access (DSA) networks. A novel graph MAximum SPECTrum packing algorithm (MASPECT) is proposed for a system with N secondary networks. Each secondary network makes use only of the local topology information to resolve contentions during channel access. The proposed algorithm also adapts easily to topological changes. Most approaches to channel acquisition use either centralised graph colouring or distributed approaches that result in under utilisation of spectrum. The authors show that the proposed MASPECT algorithm results in improvements by up to one order of magnitude in the spectrum utilisation for the secondary networks and results in Jain's fairness index of about 0.9. The authors further present a modified probabilistic heuristic, PMASPECT, that improves the termination time of the algorithm by up to two orders of magnitude. The authors also study the impact of the MASPECT algorithm on each individual secondary networks in the system in the presence of primary activity. For each secondary network, the proposed algorithm results in up to two orders of magnitude of reduction in the call blocking dropping probabilities in the presence of primary activity. - Author(s): H. Zhao ; E. Garcia-Palacios ; J. Wei ; S. Wang ; D. Ma
- Source: IET Communications, Volume 6, Issue 8, p. 883 –888
- DOI: 10.1049/iet-com.2010.0546
- Type: Article
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The authors propose a novel and practical approach to estimate resources and perform a distributed admission control in multi-hop ad hoc networks based on multi-rate enabled IEEE 802.11 technology. The main challenge is to determine if there exist sufficient resources [i.e. the available bandwidth (AB)] for a new incoming flow to be admitted rather than quantifying the exact amount of existing resources. In order to determine the AB along a multi-hop path, the authors take into consideration the channel rate at each hop as well as the channel idle ratio of relevant neighbouring nodes. Furthermore, the admission control is performed at the same time as the AB is determined which minimises overhead. The proposed approach can be applied hop-by-hop in a distributed manner by the end-user, thus being suitable for wireless ad hoc networks. Analysis and simulation based on the Network Simulator version 2 (NS2) platform verify the proposed approach. - Author(s): V. Asghari and S. Aïssa
- Source: IET Communications, Volume 6, Issue 8, p. 889 –899
- DOI: 10.1049/iet-com.2010.0653
- Type: Article
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In this study, the authors investigate different capacity notions in cognitive radio systems where the transmission parameters of the cognitive users are adaptively changed based on the availability of (i) channel state information (CSI) pertaining to the cognitive (secondary) user link, and (ii) soft-sensing information (SSI) about the activity of the licensed-band (primary) user as obtained from the sensing detector at the secondary user's transmitter. Using statistics of available SSI and CSI at the secondary transmitter, the cognitive user adopts a transmission policy that maximises the achievable capacity under appropriate system constraints. Assuming above considerations in a cognitive radio system operating under average received-interference and peak transmit-power constraints, the authors study three different capacity notions of spectrum-sharing fading channels – namely, ergodic, delay-limited and service-rate with/without outage – and obtain their corresponding optimal power allocation policies. In particular, in this study, the authors obtain the optimal power allocation policies to achieve the channel capacity of the secondary link for the appropriate transmission policy which satisfies the spectrum-sharing system requirements in each of the above-mentioned scenarios, and further provide expressions for the capacity metrics. They also provide illustrative numerical simulations sustaining our theoretical results. - Author(s): F.E. Lapiccirella ; Z. Ding ; X. Liu
- Source: IET Communications, Volume 6, Issue 8, p. 900 –908
- DOI: 10.1049/iet-com.2010.0542
- Type: Article
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Cognitive radio systems capable of opportunistic spectrum access represent a new paradigm for improving the efficiency of current spectrum utilisation. In this work, the authors present a novel cognitive channel access method based on learning from both primary channel transmissions and the receiver ARQ feedback signals. This new sensing-plus-confirmation scheme constitutes a non-trivial generalisation of the more traditional ‘Listen-Before-Talk’ (LBT) strategy that merely listens to and yields to primary transmissions regardless of primary receiver (PRx) responses. Our new method exploits the bi-directional and interactive nature of most wireless communication links to facilitate better opportunistic secondary access while achieving PRx protection. By allowing the secondary users to learn from both primary transmissions and the corresponding receiver confirmations, our approach allows secondary cognitive users to exploit critical information that PRxs regularly send to their transmitters. The authors show that, by monitoring both primary transmissions and receiver feedback signals, secondary radio access can improve throughput over the traditional LBT while limiting the probability of collision with primary user signals. - Author(s): S. Li and X. Wang
- Source: IET Communications, Volume 6, Issue 8, p. 909 –916
- DOI: 10.1049/iet-com.2010.0566
- Type: Article
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In this study, the authors have investigated a dynamic spectrum access method for cognitive radio (CR) networks by using polychromatic sets (PS) theory. First, a power control model is proposed in which the transmission power at a CR node can be calculated by considering both the primary radio (PR)-to-CR and PR-to-PR interference under a specific outage probability. In order to allocate the available spectrum among the CR nodes in a spectrum overlay scenario, the authors further propose a channel selection algorithm based on PS. This study also gives a framework of the PS-based method and concludes with future work describing the practical implementation of the proposed framework. Effectiveness of proposed method is demonstrated through an example application. - Author(s): J. Zhou ; Y. Li ; B. Evans
- Source: IET Communications, Volume 6, Issue 8, p. 917 –930
- DOI: 10.1049/iet-com.2010.0586
- Type: Article
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Using multiple antennas in coexisting radio systems can cancel or control the co-channel interference and hence improves the overall spectrum efficiency. However, the hardware complexity and costs limit the usage of multiple-antenna technologies. Antenna selection technology may reduce such costs while partly remaining the advantages of the multiple-antenna technology. In this paper, the authors focus on the downlink of a multiple-input single-output (MISO) cognitive radio (CR) system and apply antenna selection techniques in the transmitter side of the secondary system. Two scenarios have been considered: one is single antenna selection and the other one is multiple antenna selection using linear beamforming. For the first scenario, the authors analyse the performance of minimum interference and maximum data power strategies, and then propose a maximum signal to leak interference power ratio (SLIR) strategy which consider both interference and useful signals; for the second scenario, the authors discuss the optimal, maximum norm, and proposed subset optimal strategy, which has lower computational complexity and less feedback information. Simulations results verified the analysis. It is also shown that the proposed methods achieve a better trade-off and obtain near-optimal performance in terms of SNR. - Author(s): M. Marazin ; R. Gautier ; G. Burel
- Source: IET Communications, Volume 6, Issue 8, p. 931 –935
- DOI: 10.1049/iet-com.2010.0463
- Type: Article
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For enhancement of the quality of digital transmissions, standards are in continual evolution, which generates compatibility problems. Cognitive radio systems permit one to solve this problem through the design of intelligent receivers. However, such receivers must be able to adapt themselves to a specific transmission context. This requires the development of new methods in order to blindly estimate error-correcting codes. Coding schemes such as turbocode, composed of convolutional codes, belong to a family of error-correcting codes in use in many standards. In most of the methods designed to identify convolutional encoders the algebraic properties are used implicitly. However usually, these dedicated properties are neither explicated, nor detailed, nor demonstrated. The study reported here investigates the algebraic properties of convolutional encoders, useful for blind recognition methods in the cognitive radio context and more specially the algebraic relationships between different forms of a convolutional code and its corresponding dual code. Moreover, some simulation results are presented to show the relevance of these properties for the blind identification of the convolutional encoder. - Author(s): W. Zhou ; J. Wang ; W. Tang ; S. Li
- Source: IET Communications, Volume 6, Issue 8, p. 936 –944
- DOI: 10.1049/iet-com.2010.0555
- Type: Article
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This study deals with the scaling laws of ad hoc cognitive networks. In the network, m primary users and n secondary users (m<n) are randomly located in the same geographic area and share one common frequency spectrum. By loosening some of the restrictions for the network, the authors obtained the throughput upper bounds for both primary and secondary users. To obtain the lower bounds (achievable throughputs), we proposed a cooperative transmission scheme between the primary and secondary users by using the percolation theory, and the results showed that the achievable throughputs can meet the upper bounds, thus, the authors obtained the throughputs. On the basis of our results, per primary user can transmit with a throughput of min(Θ(1), Θ(√n/m)), which is higher than the throughput of Θ(√1/m) in the cognitive network without cooperative relay. This may serve as a strong incentive for primary users to cooperative with secondary users. Meanwhile, secondary users can achieve the same scale as if there is no primary network exists. - Author(s): J. Liu ; W. Chen ; Z. Cao ; Y.J. (Angela) Zhang
- Source: IET Communications, Volume 6, Issue 8, p. 945 –954
- DOI: 10.1049/iet-com.2010.0640
- Type: Article
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The authors propose a cross-layer approach, which exploits distributed beamforming in the physical layer and token passing in the media access control (MAC) layer, to improve quality of service (QoS) for secondary users (SUs) with bursty traffics in cognitive relay systems. In this scheme, source-to-destination transmissions are relayed by some SU nodes, which can form a distributed beamformer to forward messages in busy timeslots while completely eliminating interference to primary users (PUs). In contrast with previous cognitive relaying protocols, this scheme can utilise more spectrum resources, namely idle timeslots (or temporal spectrum holes) as well as busy timeslots (or spatial spectrum holes). Based on a token passing mechanism, an opportunistic scheduling protocol is then developed to dynamically balance available spectrum holes between the source and the relays, and hence adapts to bursty arrival of secondary traffics and random presence of PUs. By formulating a tandem queueing analytical framework, the performance of the proposed scheme is then analysed using a multi-dimensional Markov chain model. Numerical results demonstrate that the proposed scheme can achieve significant QoS gains over conventional cognitive relaying protocols that utilise only idle timeslots. - Author(s): S. Li ; X. Wang ; J. Wang
- Source: IET Communications, Volume 6, Issue 8, p. 955 –963
- DOI: 10.1049/iet-com.2010.0590
- Type: Article
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Adaptive signal identification has been an important issue in cognitive radio networks (CRNs). Most existing techniques require high-level signal-to-noise ratio (SNR) for signal identification. This study presents an intelligent technique that focuses on a theoretical and experimental study of the signal identification by using manifold learning algorithm in CRNs. The authors pose the problem of signal identification in CRNs as signal classification by using manifold learning on high dimensions, and a novel manifold learning algorithm named as SIEMAP is proposed, which is able to identify signals in a low-dimensional space. Simulation results indicate that SIEMAP outperforms classical methods in low dimensions and is capable of identifying signal types from the received signals. - Author(s): Y. Tan ; S. Sengupta ; K.P. Subbalakshmi
- Source: IET Communications, Volume 6, Issue 8, p. 964 –973
- DOI: 10.1049/iet-com.2010.0573
- Type: Article
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Cognitive radio (CR) enabled dynamic spectrum access (DSA) networks are designed to detect and opportunistically utilise the unused or under-utilised spectrum bands. However, due to the open paradigm of CR networks and lack of proactive security protocols, the DSA networks are vulnerable to various denial-of-service threats. The authors propose a game-theoretic framework to study the primary user emulation attack (PUEA) on CR nodes. A non-cooperative dynamic multistage game between the secondary nodes and the adversaries generating the PUEA is formulated. The pure-strategy and mixed-strategy Nash equilibria for the secondary user and malicious attacker are investigated. Moreover, a novel belief updating system is proposed for the secondary user to learn the state of the primary user as the game evolves. Simulation results demonstrate that the proposed belief updating system achieves better performance than other models for the secondary user in terms of greater payoff, lower probability of missing primary user and better robustness to the inaccurate estimation of the primary user's state. - Author(s): H. Tang ; F.R. Yu ; M. Huang ; Z. Li
- Source: IET Communications, Volume 6, Issue 8, p. 974 –983
- DOI: 10.1049/iet-com.2010.0553
- Type: Article
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Cognitive radios (CRs), which are capable of sensing its surrounding environment and adapting its internal parameters, have been considered in mobile ad hoc networks (MANETs). The area of security in CR-MANETs has received far less attention than other areas. However, some distinct characteristics of CRs introduce new non-trivial security risks to CR-MANETs. In this article, the authors study spectrum sensing data falsification (SSDF) attacks to CR-MANETs, in which intruders send false local spectrum sensing results in cooperative spectrum sensing, and it will result in wrong spectrum sensing decisions by CRs. The authors present a novel bio-inspired consensus-based cooperative spectrum sensing scheme to counter SSDF attacks in CR-MANETs. Their scheme is based on recent advances in consensus algorithms that have taken inspiration from self-organising behaviour of animal groups such as birds, fish, ants, honeybees and others. Unlike the existing schemes, there is no need for a common receiver to do the data fusion for reaching the final decision to counter SSDF attacks. The scheme has self-configuration and self-maintenance capabilities. Moreover, in order to further improve the security of CR-MANETs, the authors present an authentication scheme using identity (ID)-based cryptography with threshold secret sharing. Simulation results are presented to show the effectiveness of the proposed schemes. - Author(s): E. Romero ; A. Mouradian ; J. Blesa ; J.M. Moya ; A. Araujo
- Source: IET Communications, Volume 6, Issue 8, p. 984 –990
- DOI: 10.1049/iet-com.2010.0582
- Type: Article
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Along with the development of cognitive radio networks, designing optimistic security mechanisms is becoming a big challenge. This study proposes a taxonomy of attacks on cognitive radio networks. This will help researches to better understand the security problems and to design more optimistic countermeasures. A new simulation framework for security threats has been developed to check all these attacks and countermeasures. The simulation framework has been tested with a primary user emulation attack. A new testbed for simulations suitable for cognitive radio security is ready. - Author(s): K. Koufos ; K. Ruttik ; R. Jäntti
- Source: IET Communications, Volume 6, Issue 8, p. 991 –1003
- DOI: 10.1049/iet-com.2010.0572
- Type: Article
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The authors consider a short-range cognitive network with secondary users (SUs) generating voice calls. The SUs measure the TV spectrum and classify the measured bands as either idle or occupied. When most of the measured bands are detected to be occupied, there might not be enough capacity to serve all the SUs' calls. In this study the authors identify the minimum required number of measured bands such that the probability to serve all the secondary calls is controlled. The detection performance requirements imposed by the primary systems are also satisfied. The authors formulate this problem as an optimisation problem with optimisation parameters the number of users measuring each band and the measurement time. For a small number of SUs the authors identify the minimum required number of measured bands by using exhaustive search. For a large number of users the authors propose to solve the optimisation problem by means of a greedy algorithm. The algorithm is verified against the exhaustive search results and it is found to perform remarkably well. Therefore it is suitable for practical secondary systems searching for sharing opportunities over the TV spectrum. - Author(s): L. Subrt and P. Pechac
- Source: IET Communications, Volume 6, Issue 8, p. 1004 –1010
- DOI: 10.1049/iet-com.2010.0544
- Type: Article
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This study introduces the concept of an intelligent wall as an autonomous part of a smart indoor environment for cognitive wireless networks. Here, an intelligent wall is a wall inside a building equipped with an active frequency-selective surface, simple low-cost sensors and a cognitive engine with machine-learning ability. Using simulations, it has been shown that the smart environment based on intelligent walls can react to the immediate demands of an indoor wireless system, control radio coverage and, consequently, influence the overall system performance. The concept of the intelligent walls is described and evaluated based on a simple implementation of an arrangement of two intelligent walls in a conference centre scenario. Artificial neural networks were employed in the cognitive engine. Elementary orthogonal frequency division multiple access static system simulations are used to analyse the influence of the smart environment on the system performance. Results are discussed in detail and typical characteristics of the aforementioned system are derived and summarised.
Editorial: Cognitive communications
Improved energy detection spectrum sensing for cognitive radio
Optimal opportunistic sensing in cognitive radio networks
Spectrum sensing in cognitive radios based on enhanced energy detector
Features detection assisted spectrum sensing in wireless regional area network cognitive radio systems
Modelling and analysis of detection time trade-offs for channel searching in cognitive radio networks
Partially observable Markov decision process-based MAC-layer sensing optimisation for cognitive radios exploiting rateless-coded spectrum aggregation
Precoder adaptation and power control for cognitive radios in dynamic spectrum access environments
Secondary spectrum access and cell-edge coverage in cognitive cellular networks
Low complexity distributed spectrum access algorithm for cognitive radio
Peak power control in cognitive radio context
MAximum SPECTrum packing: a distributed opportunistic channel acquisition mechanism in dynamic spectrum access networks
Distributed resource management and admission control in wireless ad hoc networks: a practical approach
Spectrum sharing in cognitive radio systems: service-oriented capacity and power allocation
Improved spectrum access control of cognitive radios based on primary ARQ signals
Polychromatic set theory-based spectrum access in cognitive radios
Antenna selection for multiple-input and single-output cognitive radio systems
Some interesting dual-code properties of convolutional encoder for standards self-recognition
Scaling laws of cognitive networks with cooperative relay
Token-based opportunistic scheduling protocol for cognitive radios with distributed beamforming
Manifold learning-based automatic signal identification in cognitive radio networks
Primary user emulation attack in dynamic spectrum access networks: a game-theoretic approach
Distributed consensus-based security mechanisms in cognitive radio mobile ad hoc networks
Simulation framework for security threats in cognitive radio networks
Voice service in cognitive networks over the TV spectrum
Intelligent walls as autonomous parts of smart indoor environments
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A review on security threats, vulnerabilities, and counter measures of 5G enabled Internet‐of‐Medical‐Things
- Author(s): Mohammad Kamrul Hasan ; Taher M. Ghazal ; Rashid A. Saeed ; Bishwajeet Pandey ; Hardik Gohel ; Ala’ A. Eshmawi ; S. Abdel‐Khalek ; Hula Mahmoud Alkhassawneh
- Type: Article
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Compressive sensing-based coprime array direction-of-arrival estimation
- Author(s): Chengwei Zhou ; Yujie Gu ; Yimin D. Zhang ; Zhiguo Shi ; Tao Jin ; Xidong Wu
- Type: Article
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Massive MIMO: survey and future research topics
- Author(s): Daniel C. Araújo ; Taras Maksymyuk ; André L.F. de Almeida ; Tarcisio Maciel ; João C.M. Mota ; Minho Jo
- Type: Article
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Performance analysis of non-orthogonal multiple access in downlink cooperative network
- Author(s): Jinjin Men and Jianhua Ge
- Type: Article
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Non-orthogonal multiple access schemes with partial relay selection
- Author(s): Sunyoung Lee ; Daniel Benevides da Costa ; Quoc-Tuan Vien ; Trung Q. Duong ; Rafael Timóteo de Sousa Jr.
- Type: Article
