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There are differences between routing in traditional and in Cognitive Radio Networks (CRNs). The availability of channels, periodic spectrum sensing, jammers activity, are some of these differences, etc. CRNs may contain a large number of Internet of Things (IoT) devices, hence, modeling such networks with a flat graph model generates a huge graph size. Thus, the motivation behind this work is clear bearing in mind that modeling such networks with a Multi-layer Hyper-Graph (MLHG) is the idea presented in this paper, in which each hyper-edge represents a group of CR devices, and each layer represents a licensed channel. In this paper, the main aim is to consider four key factors to maximize end-to-end network throughput, which are, transmission rate, licensed users activity, jammers activity, and needed number of time sharing. In literature, considering both jamming activity and time sharing for routing exists in few papers till now. This work proposes and develops three cutting-edge routing protocols that are aware of the four aforementioned factors, namely, Jamming-Activity-Sharing-Rate-Aware protocol, Jamming-Activity-Rate-Aware protocol, and Jamming-Activity-Sharing-Aware protocol. We compare these protocols with three recent proposed protocols in CRNs. Simulation results indicate that when jammers activity and time sharing are considered, network throughput is significantly enhanced. Specifically, our proposed jamming-aware protocols significantly outperform the existing three jamming-unaware protocols by up to 127 %. [ABSTRACT FROM AUTHOR]

Cognitive radio (CR) technology enables dynamic spectrum access for 5G and Beyond 5G (B5G) networks. Specifically, CR provides massive spectrum opportunities for enabling large-scale deployment of 5G/B5G networks. Multiple-input, multiple-output (MIMO) technology is another promising technique that can significantly improve the performance of 5G/B5G networks. Integrating the MIMO technology with the CR technology can further improve the wireless network's performance. However, due to the dynamic nature of the CR operating environment, such integration imposes several design challenges regarding the appropriate MIMO-mode selection, spectrum assignment, and user selection. Unlike the majority of previously developed MIMO-based spectrum access protocols that execute the channel assignment sequentially, we investigate the problem of maximizing the network throughput by simultaneously providing distributed CR-aware MIMO-mode channel-assignment decisions for multiple CR transmissions (batching approach) subject to a set of constraints. The joint batch-based MIMO-mode and channel-assignment optimization is, in general, an NP-hard combinatorial integer non-linear problem. To solve such a joint problem in polynomial-time, we propose a two-stage optimization algorithm. In the first stage, the proposed algorithm finds the highest number of packets that each contending CR user can send over each idle channel. Then, in the second stage, the best channel–user assignment that can result in the highest number of transmitted packets is computed. To realize the proposed batch-based algorithm in a distributed manner, we adopt an admission control process that allows CR users to announce the required control information. Compared with the existing MIMO-based CRN protocols, the results show that by jointly performing batch-based channel assignment and per-user MIMO-mode optimization, the proposed protocol significantly enhances the overall network throughput by up to 60%. [ABSTRACT FROM AUTHOR]

Typical MAC protocols for IEEE 802.11-based ad hoc networks employ a direct transmission strategy whenever the transmitter can directly reach the receiver (one-hop transmission). While such a design enjoys simplicity, it limits the number of admitted transmissions in a given neighborhood. Due to the performance anomaly of 802.11-based wireless networks, transmission with low data rates occupy the shared medium for longer periods of time. Occupying the transmission medium for a longer period of time results in less available transmission time for other nodes, which consequently reduces the number of transmitted packets during the same period of time, leading to a reduction in network throughput. To improve the overall network throughput, we present a cooperative multi-channel MAC protocol for single-hop wireless mobile ad hoc networks that attempts at computing the path with the minimum required transmission time for a given source–destination pair (including the channel assignment along that path). The proposed protocol attempts at improving network performance by means of cooperative communications. According to our approach, if the one-hop (direct) path between communicating nodes supports low data rate (requires longer transmission time), the source selects a multi-hop path to the destination such that the total amount of required transmission time is minimized. Through simulations, we show that our proposed protocol achieves significant throughput and fairness improvement compared to the standard IEEE 802.11-based protocol. [ABSTRACT FROM AUTHOR]

Software-defined Cognitive radio (CR) networking is considered a promising communication paradigm that can deliver huge spectrum opportunities for enabling massive deployment for wireless Internet-of-Things (IoT) applications and services. An important challenge in this domain is how to provide effective energy-efficient distributed spectrum coordination mechanisms (known as Spectrum Rendezvous), through which the CR IoT users can opportunistically coordinate their transmissions over the idle licensed frequency channels without relying on the existence of a dedicated common control channel (CCC). This paper proposes a novel frequency hopping (FH) distributed rendezvous mechanism for CR-capable IoT (CR-IoT) networks using grid-based quorum systems, referred to as adaptive grid-based quorum channel-hopping scheme. The proposed quorum-based scheme divides the time into equidistant cycle segments, referred to as quorum-based FH intervals. Each quorum interval consists of equal-duration beaconing intervals, each associated with a licensed channel. According to the proposed algorithm, each CR-IoT device randomly selects awake-sleep schedules based on the adopted quorum system structure. Any two devices can exchange their control information over the assigned channels of their common awake beaconing intervals. The proposed algorithm provides probabilistic guarantees on the successful rendezvous (RDV) between any two CR-IoT users within a single quorum-based FH interval (cycle) and dynamically adjusts the adopted QS structure based on the time-varying traffic load in the CR-IoT network such that the RDV probability and the expected average time to rendezvous improve with the least possible energy consumption. Compared to reference design schemes, the simulation results demonstrate that the proposed algorithm significantly increases the RDV probability, reduces the average rendezvous time, and reduces the energy consumption per successful RDV. • A distributed quorum-based FH rendezvous algorithm for CR-IoT networks is developed. • A probabilistic guarantee on successful rendezvous between IoT users is provided. • The rendezvous probability has been significantly increased. • The rendezvous time and consumed energy per successful rendezvous were decreased. [ABSTRACT FROM AUTHOR]

The emerging IEEE 802.22-based Wireless Regional Area Network (WRAN) is the first wireless standard based on the Cognitive Radio (CR) technology. WRAN is designed to offer wireless access services in a large coverage area by allowing Secondary Users (SUs) to opportunistically exploit the under-utilized licensed portion of spectrum that is primarily allocated for TV services. To enable efficient WRAN communications, the operation of a WRAN system should address two types of coexistence problem: incumbent co-existence and self-coexistence. In this paper, we investigate the self-coexistence problem in a multi-cell WRAN system that adopts an exclusive spectrum sharing policy. Specifically, we present an adaptive channel allocation scheme based on a cooperative max–min weighted fair allocation strategy. The proposed scheme is based on a centralized sensing mechanism that identifies the available spectrum opportunities for the WRAN cells. Our scheme dynamically allocates the available spectrum (idle channels) to the WRAN cells based on their expected traffic loads such that the total number of simultaneously admitted SU transmissions in the WRAN system is maximized. The expected traffic load is accurately estimated using a sample mean estimator based on previously monitored traffic in each cell. Simulation results indicate that our scheme is quite robust to traffic estimation error. Compared to reference spectrum allocation schemes, simulation results indicate that the proposed scheme effectively exploits the available spectrum opportunities by increasing the total number of served SU transmissions, which consequently results in a significant enhancement in the overall WRAN system performance. [ABSTRACT FROM AUTHOR]

Abstract: This letter proposes a multi-channel parallel transmission mechanism for channel assignment in cognitive radio (CR) networks. The proposed mechanism enables secondary users (SUs) to effectively utilize the spectrum. The main novelty in our mechanism lies in utilizing the parallel transmission capability of CRs while considering the randomness of their operating environment to provide soft guarantees on the performance of SUs. Simulation results show that utilizing CR''s parallel transmission capability while considering the time-varying nature of their operating environment allows for higher spectrum utilization and more energy saving. [Copyright &y& Elsevier]

Abstract: Cognitive radio (CR) is a revolutionary technology in wireless communications that enhances spectrum utilization by allowing opportunistic and dynamic spectrum access. One of the key challenges in this domain is how CR users cooperate to dynamically access the available spectrum opportunities in order to maximize the overall perceived throughput. In this paper, we consider the coordinated spectrum access problem in a multi-user single-transceiver CR network (CRN), where each CR user is equipped with only one half-duplex transceiver. We first formulate the dynamic spectrum access as a rate/power control and channel assignment optimization problem. Our objective is to maximize the sum-rate achieved by all contending CR users over all available spectrum opportunities under interference and hardware constraints. We first show that this problem can be formulated as a mixed integer nonlinear programming (MINLP) problem that is NP-hard, in general. By exploiting the fact that actual communication systems have a finite number of available channels, each with a given maximum transmission power, we transfer this MINLP into a binary linear programming problem (BLP). Due to its integrality nature, this BLP is expected to be NP-hard. However, we show that its constraint matrix satisfies the total unimodularity property, and hence our problem can be optimally solved in polynomial time using linear programming (LP). To execute the optimal assignment in a distributed manner, we then present a distributed CSMA/CA-based random access mechanism for CRNs. We compare the performance of our proposed mechanism with reference CSMA/CA channel access mechanisms designed for CRNs. Simulation results show that our proposed mechanism significantly improves the overall network throughput and preserves fairness. [Copyright &y& Elsevier]

Abstract Establishing stable routes over high mobility networks is a challenging field and consequently brought the attention of a lot of current researchers. In this article, a new reactive routing protocol has been proposed which is considered as a major extension of both Ad-hoc On-demand Distance Vector (AODV) and Mobility and Direction Aware AODV (MDA-AODV) prior routing protocols. It is named as Mobility Aware and Dual Phase Ad-hoc On-demand Distance Vector with Adaptive Hello Messages (MA-DP-AODV-AHM). It primarily concentrates on building routes considering vehicles’ speeds and direction of motion with respect to source vehicles, thereby establishing more stable routes and reducing the route breakages. Not only to this extent, but rather, we proposed an adaptive control packet announcement mechanism, which is directly connected to the periodic hello messages approach, with vehicles’ speeds, yielding a significant reduction in the amount of control overhead and congestion over the network. Moreover, the new protocol is proposed to alternate working among two phases, for the reason of guaranteeing the generation of efficient routes on a timely basis, which include MA-DP-AODV-AHM and AODV protocols. Our protocol has been evaluated in terms of control overhead, end-to-end delay, and energy consumption using QualNet simulator version 7.1 in which enormous simulations have been conducted under the base of vehicle density, packet rate, and constant bit rate connections. Simulation results summarize that MA-DP-AODV-AHM contributes efficiently in mitigating the network instability through generating effective stable routes and reducing link failures. Furthermore, it has proved its superiority over AODV and MDA-AODV. [ABSTRACT FROM AUTHOR]

The pilot overhead provides fundamental limits on the performance of massive multiple-input multiple-output (MIMO) systems. This is because the performance of such systems is based on the failure of the presentation of accurate channel state information (CSI). Based on the theory of compressive sensing, this paper presents a novel channel estimation technique as the mean of minimizing the problems associated with pilot overhead. The proposed technique is based on the combination of the compressive sampling matching and sparsity adaptive matching pursuit techniques. The sources of the signals in MIMO systems are sparsely distributed in terms of spatial correlations. This distribution pattern enables then use of compressive sampling techniques to solve the channel estimation problem in MIMO systems. Simulation results demonstrate that the proposed channel estimation outperforms the conventional compressive sensing (CS)-based channel estimation algorithms in terms of the normalized mean square error (NMSE) performance at high signal-to-noise ratios (SNRs). Furthermore, it reduces the computational complexity of the channel estimation compared to conventional methods. In addition to the achieved performance gain in terms of NMSE, the presented method significantly reduces pilot overhead compared to conventional channel estimation techniques. [ABSTRACT FROM AUTHOR]

Software-Defined Networking (SDN) is a modern network approach that replaces the conventional network architecture with a flexible architecture by separating the control plane from the data plane. SDN simplifies network management and monitoring through logically centralized intelligence, programmability, and abstraction. SDN architectures are vulnerable to attacks, such as the Denial of Service (DoS) attack. This article reviews and classifies the research efforts on SDN and DoS. We categorized the research efforts into two groups: solutions to cope with DoS attacks on SDN and SDN-based solutions to tackle DoS attacks on networks. The first group of solutions includes six categories: Table-Entry, Scheduling, Architectural, Flow Statistics, Machine Learning, and Hybrid solutions. Furthermore, the article surveys the tools and datasets considered by the reviewed contributions. The article presents a detailed comparison among reviewed approaches in terms of network devices, network layers involved, DoS attack's types, and targets of attacks. [Display omitted] • Software-Defined Networking architectures are vulnerable to Denial-of-Service attacks. • A review on solutions to cope with Denial-of-Service attacks on Software-Defined Networking. • A review on Software-Defined Networking based solutions to tackle Denial-of-Service attacks. • About 72.9% of the solutions used control layer modules. • The article surveys the tools and datasets considered by the reviewed contributions. [ABSTRACT FROM AUTHOR]