Protocol For Cognitive Radio Networks Research Articles

A Review: Routing Protocols for cognitive Radio Networks

A Review: Routing Protocols for cognitive Radio Networks

A Reinforcement Learning Based Routing in Cognitive Radio Networks for Primary Users with Multi-stage Periodicity

Designing an efficient routing protocol for cognitive radio networks is critical due to the dynamic behavior of the primary users. Based on empirical studies, the primary users activity on the licensed channels has periodicity comprised of several stages, and that the model of primary users activity may change during different stages. This paper has identified two main challenges facing designers: how to transmit packets via a stable route, and how to ensure imposing of minimal interference on the primary users. To address these, we propose a routing protocol which is based on a generalized version of Q-learning and which exploits the said model of primary users behavior. We divide the infinite time horizon into cycles (corresponding to periods), then break each cycle into several sub-cycles (corresponding to stages), making an assumption that the statistical model parameters of the primary users activity will not change during a sub-cycle. The extensive simulations confirm that our proposed routing approach outperforms existing schemes in terms of throughput and minimal interference. The paper also verifies that imposing of significant interference on the primary users and degradation of QoS of secondary users stem from lack of attention to the multi-stage periodic behavior of primary users.

Cooperation-based multi-hop routing protocol for cognitive radio networks

In the scope of cognitive radio networks, typical routing protocols avoid areas that are highly congested with primary users, leaving only a small fragment of available links for secondary route construction. In addition, wireless links are prone to channel impairments such as multipath fading which renders the quality of the available links highly fluctuating. In this paper, we propose Undercover: a multi-hop routing protocol for cognitive radio networks in which we integrate the collaborative beamforming technique with layer 3 routing. Specifically, our protocol revisits a fundamental assumption taken by the state of the art routing protocols designed for overlay cognitive radio networks; this assumption is that secondary users cannot use the spectrum when primary users are using it. In Undercover, we allow a group of secondary users, each with a single antenna, to collaborate together and transmit in the regions of primary users activity. This is done through nulling out transmission at primary receivers via beamforming. Moreover, Undercover is designed to enhance the transmission quality at the secondary destinations whenever possible. To account for the excessive levels of interference typically incurred due to cooperative transmissions, we allow our protocol to be interference-aware. Thus, cooperative transmissions are penalized in accordance with the amount of negatively affected secondary flows. We evaluate the performance of our proposed protocol via NS2 simulations which show that our protocol can enhance the network goodput by a ratio reaches up to 250% compared to other state-of-art cognitive routing protocols with minimal added overhead.

ARQ-based cooperative spectrum sharing protocols for cognitive radio networks

In this paper, we propose two cooperative spectrum sharing protocols for cognitive radio networks which consist of an automatic repeat request based primary user with a primary transmitter (PT) and a primary receiver (PR), and a bidirectionally communicating secondary user (SU) with two nodes, S1 and S2. PT transmits a packet to PR by accessing the spectrum alone or by the cooperation of SU or under the interference of SU in the underlay transmission, according to the acknowledgement/negative acknowledgement feedback from PR. The two protocols differ by the application of decode-and-forward and amplify-and-forward strategies at SU during cooperation. Analytical expressions are derived for the throughputs of both users for both protocols and the results are compared with the corresponding reference protocols given in the literature. The theoretical results which are in perfect match with the simulation results show the advantages of the proposed protocols.

A bio-inspired leader election protocol for cognitive radio networks

The bio-inspired approach has been used effectively to address computing problems related to the domains, where nondeterminism is involved, e.g. sensing, assignment, localization, resource allocation, routing, optimization etc. The leader election in cognitive radio networks (CRN) is one such problem however no published work in the existing literature has used bio-inspired approach for leader election in CRN. The article proposes a bio-inspired ant colony approach for leader election in cognitive radio network (CRN). Our leader election algorithm is based on diffusion computation. We use metaheuristic method to explore CRN, create spanning tree, and find extrema that is declared leader. Our metaheuristic functions such as generation of ants, activity to search pheromone trail, pheromone evaporation (or daemon action) are composed of basic bio-inspired mechanisms, namely spreading, aggregation and evaporation. We validate our work with extensive simulation based on popularly used performance metrics. Further, the correctness proof of the protocol has also been included in the exposition. To the best of our knowledge, it is first bio-inspired extrema finding algorithm in cognitive radio networks.

CMORC: Class-based Multipath On-demand Routing Protocol for Cognitive Radio Networks

Cognitive Radio (CR) technology enables Dynamic Spectrum Access (DSA) to ameliorate the eciency of under-utilized licensed bands and overcrowded unlicensed bands. However, providing an acceptable service for cognitive users requires more sophisticated approaches due to the existence of Primary Users (PU) with high priority over licensed bands. Additionally, reducing interference with PUs so that they can communicate without interruption is of paramount importance. In order to meet requirements of users as much as possible and reduce interference with PUs, a new Class-based Multi-path On-demand Routing protocol for Cognitive radio networks (CMORC) is proposed. CMORC is a multipath routing protocol which de nes two classes of routing to make delay or interference optimum. To the best of our knowledge, it is the rst multipath protocol that takes into consideration both route discovery and rate allocation. CMORC fi nds optimum sending rates for each path by solving an optimization problem for each routing class. Since it is shown to be easy to solve these optimization problems, CMORC is an ecient and practical solution for radio equipment with limited hardware. The simulation results reveal that CMORC outperforms the other recent multipath routing protocol,D2CARP, in terms of interference, delay and packet delivery ratio depending on the class type.

Cooperative spectrum sharing in cognitive radio networks: An interference free approach

We present a novel interference free dual-hop cooperative spectrum sharing protocol in cognitive radio networks exploiting spatial modulation (SM) at both primary transmitter (PT) and secondary transmitter (ST). A ST equipped with multi-antenna acts as a half-duplex decode-and-forward relay for the primary system. During phase-1, SM is invoked at PT, while ST keeps silent. The information bit stream of PT is mapped into two different sets: the M-ary phase shift keying (M-PSK)/M-ary quadrature amplitude modulation (M-QAM) bits and the antenna index. The ST then exploits iterative-maximum ratio combining (i-MRC) technique to de-map the block of information bits, transmitted by PT. During phase-2, ST forwards the primary data by activating only one antenna based on its own secondary data exploiting the concept of SM. The PT’s data is then retrieved at the primary receiver (PR) and the secondary receiver (SR) recover its own desired data by detecting only the transmit antenna indices of ST using i-MRC. As a result, mutual interference between primary and secondary systems is avoided and interference cancellation techniques at the PR and SR are no longer needed. In the proposed protocol, the primary user does not need to lease its spectrum or time slots to the secondary user in exchange for cooperation. Moreover, power of ST does not need to be distributed for primary and secondary transmission simultaneously during phase-2. The simulation and analytical results are presented to show effectiveness of the proposed protocol compared to conventional spectrum leasing and superposition coding based overlay protocols.

A Leader Election Protocol for Cognitive Radio Networks

Leader election is a fundamental problem of distributed computing systems. In cognitive radio network (CRN), the secondary users (SUs) are connected under the leased spectrum of primary user (also called, licensed user) and hence often called opportunistic network. The emerging trend is to maximize the channel utilization in CRN. However, the computational activities performed by the SUs depend on the activity of primary user. Thus, in general, CRN is highly dynamic and network architectures are short lived. Many applications require a leader node to carry out better coordination among the participating nodes. The CRN being a highly dynamic network, the leader election is more challenging than in other networks. The leader node coordinates the activities of SUs and regulates the appropriate channel among them keeping in view the behavioral activities of PUs, which leads to enhanced channel utilization. We propose a diffusion computation based leader election protocol for CRN. The protocol is “weakly” self stabilizing and terminating.

Cooperative Hybrid Spectrum Sharing: A NOMA-based Approach

Non-orthogonal multiple (NOMA) access using successive interference cancellation and cognitive radio are two promising techniques for enhancing the spectrum efficiency and utilization for future wireless communication systems. This paper presents a NOMA-based cooperative hybrid spectrum sharing protocol for cognitive radio networks. A two phase decode-and- forward (DF) relaying scheme in a multi-relay scenario is considered. Each secondary transmitter is grouped into one of the two clusters: a non-cooperative cluster (NCC) and a cooperative cluster (CC). The cluster head (CH) of the CC working as the best DF relay for the primary system is permitted to transmit its own signal superimposed on the primary signal using a NOMA approach in exchange for cooperation. On the other hand, the CH of the NCC transmits in parallel with the primary system satisfying a predefined peak transmit power and peak interference power constraints that guarantee a given primary quality of the service requirement. It is demonstrated that the performances of both the primary and secondary systems increase with the increasing number of secondary nodes. The simulation and theoretical results affirm the efficacy of the proposed protocol compared to the traditional overlay and underlay models in terms of the outage probability and the ergodic capacity.

基于NS-3的CR认知网络仿真平台研究

认知无线电技术为缓解频谱资源紧缺，提高频谱利用率提供了重要解决方案。但目前尚缺乏验证相关理论的成熟原型和仿真平台，而且一些实验平台和设备无法实现认知网络跨层协作。针对缺少仿真验证平台和跨层协作问题，提出并实现了一种基于新型网络模拟器NS3的认知网络仿真平台CRE-NS3。该平台扩展了认知无线电的频谱感知功能，采用跨层协作方法实现频谱在空、时、频多域的有效利用。实验结果表明，CRE-NS3平台可实现跨层协议和认知功能的仿真验证，并可扩展到实际大规模无线网络的应用中，为下一代无线网络关键技术的研究提供了重要验证工具。 Cognitive radio has been proposed as a viable solution to alleviate spectrum scarcity problems and improve spectrum efficiency. However, some related theories were difficult to be verified because of the absence of mature prototype and experimental platform. Also, some cross-layered protocols in cognitive radio networks cannot be trivially implemented in off-the-shelf hardware. To resolve these problems, therefore, a new cognitive radio extension framework based on NS3 simulator (CRE-NS3) was proposed and implemented. This simulation platform incorporated some functions of cognitive radio and cross-layered protocols to improve spectrum efficiency in space, time and frequency. The simulation results show that the CRE-NS3 verified the feasibilities of cross-layered protocols and cognitive capabilities. Moreover, it can be extended to the actual larger-scale cognitive networks, and provides an approach to research of key techniques in next- generation wireless networks.

Energy Aware Routing Protocol for Cognitive Radio Networks

In this article, a routing protocol EARP (Energy Aware Routing Protocol) with the terminal node is proposed, to deal with the impact of the limited energy resources of Cognitive Radio Networks on the whole network routing. The protocol allows choosing the route from the neighbor nodes in different transmission paths, according to energy consumption of a single node and the full path. If the path breaks, the protocol will increase local routing maintenance strategy. It effectively reduces the retransmission caused by the situation, and improves the routing efficiency. It also can prevent the link transmission process selecting the fault route due to the energy depletion. Through simulation experiments compared with the LEACH (Low Energy Adaptive Clustering Hierarchy) routing protocol, the results showed that in the same experimental environment, the proposed EARP could obviously balance the load, protect low energy nodes, prolong the network survival time and reduce packet loss rate and packet delay of data delivery. So it can improve the energy consumption of sensing node and provide routing capabilities.

Energy‐efficient cooperative two‐hop amplify‐and‐forward relay protocol in cognitive radio networks

It has been shown that amplify-and-forward (AF) transmission is a viable transmission protocol for wireless networks incorporating distributed spatial diversity. However, a drawback of this relatively simple protocol is identified, the destination node is only to combine a part of the signal, while the other part of the signal has been regarded as interference for delay, leading to the lower utilisation of the resource inevitably, which manifests in the bigger noise, lower signal-to-noise ratio, and higher bit error rate. A revised AF relay protocol has been proposed for it could fully combine signal and eliminate delay at destination node through caching signal. A multi-user single-relay transmission model could demonstrate the superior performance of this protocol, which is in a hotspots region of a cognitive radio network. The closed-form solution of the channel transmission rate is obtained with the form of matrix multiplication, and it can ensure that even if without any interference cancellation operation it still can improve the transmission rate. Analytical expression of downlink transmission energy efficiency (DLEE) has been derived. Numerical simulation results show that the transmission performances and DLEE have been improved by proposed protocol compared with the conventional AF relay protocol and direct transmission.

Cooperative HARQ protocols using semi-blind relays for underlay cognitive radio networks

In this paper, we evaluate the throughput of cooperative ARQ and HARQ I protocols in underlay cognitive radio networks using semi blind relays. Semi Blind Relays do not require to estimate the channel of the first hop, they use only some channel statistics. Relays help the secondary source to deliver its packet. Only relays that generate an interference to primary receiver lower than a predefined threshold will be activated. Three relay selection techniques are considered: opportunistic relaying, partial and reactive relay selection. Opportunistic relaying consists in selecting the relay that offers the highest end-to-end SNR. Partial relay selection consists in selecting the relay that offers the highest SNR of the first hop. Reactive relay selection consists in selecting the relay that offers the highest SNR of the second hop. This relay is selected among the active ones that generate an interference to primary receiver lower than a predefined threshold. To the best of our knowledge, there are no studies dealing with throughput evaluation of HARQ protocols for cognitive radio networks using opportunistic relaying, partial and reactive relay selection. Besides, this is the first paper to deal with HARQ protocols using semi blind relays. Previous studies dealt with outage, bit and symbol error probabilities evaluation for cognitive radio networks.

A Batch-Based MAC Design With Simultaneous Assignment Decisions for Improved Throughput in Guard-Band-Constrained Cognitive Networks

The adjacent channel interference (ACI) resulting from imperfect filtering can severely degrade the performance of any wireless communication system. Despite this fact, most of previously proposed medium access control (MAC) protocols for cognitive radio networks (CRNs) were designed while ignoring the effects of ACI (assuming ideal filtering). The effect of ACI can be reduced by introducing guard bands (GBs). However, this solution comes at the expense of degrading spectrum efficiency. In this paper, we develop an efficient GB-aware MAC protocol that attempts at maximizing network throughput while improving fairness in CRNs. Unlike most of previously proposed GB-aware MAC protocols that perform channel assignment sequentially, our MAC performs the channel assignment for multiple CR links simultaneously (the so-called batch method). Batching enables concurrent channel assignment for multiple CR links, which consequently allows for concurrent data transmissions. Batching can be realized by introducing an admission control phase for CR users to share their control information. The batch method can effectively provide distributed decisions that achieve better throughput while reducing the number of GBs. Our MAC also allows the CR users to utilize the reserved GBs of primary networks under predefined FCC power constraints. Simulation results indicate that our protocol achieves significant performance improvement compared to previous GB-aware protocols.

A Sparsity-Aware Cooperative Protocol for Cognitive Radio Networks With Energy-Harvesting Primary User

We consider a cognitive setting composed of multiple primary frequency bands each of which consists of a limited-battery energy-harvesting primary user and a secondary user. The primary user is equipped with a limited-capacity energy queue to maintain the energy harvested from the environment. We propose a novel cooperative protocol for the secondary users. The secondary user assigned to one of the primary frequency bands is aided by a set of nearby secondary users, which we refer to as secondary relays . We assume that each secondary relay participates in relaying the secondary packets with a certain probability. The proposed protocol exploits the sparsity of the participating-relays set and is efficient as it allows dynamic relay assignment. When the secondary user's direct link is in outage, the received secondary packets at the relays are stored in a relaying queue for future retransmissions. The relays perform cooperative beamforming to achieve a cooperative diversity gain for the secondary source. We study two types of quality-of-service requirements for the primary user. We analyze the impact of the primary user energy queue arrival rate and capacity on the secondary user throughput. In addition, we investigate the impact of the relaying queue capacity and the number of relays participating in spectrum sensing on the secondary user throughput.

A novel protocol for transparent and simultaneous spectrum access between the secondary user and the primary user in cognitive radio networks

In this paper, we propose a novel protocol for cognitive radio networks, termed spectrum co-access protocol (SCAP), for secondary users to transparently and simultaneously access spectrum with primary users. The motivation is to eliminate the disruption to secondary user communications by the resurgence of primary user transmission. This protocol enables mutually beneficial coexistence between the primary user network and the secondary user network. Through spectrum co-access, SCAP creates a virtual secondary user control channel in licensed spectrum that is invisible to the primary user. As a result, SCAP is a medium access control protocol that allows for simultaneous spectrum access between the secondary user and the primary user networks. The performance evaluation indicates that SCAP provides significant performance improvement for the secondary user network over the existing opportunistic spectrum access scheme.

Joint optimisation of transmission and waiting times in cognitive radio

Transmission time optimisation is one of the key considerations of cognitive network design. There are many studies in cognitive radio networks (CRNs) focusing on finding the best transmission time for secondary users (SUs) to maximise transmission or energy efficiency. While longer sensing duration leads to a higher sensing accuracy and causes less interference, the SU spends less time for transmission and more energy on sensing spectrum. On the other hand, when the transmission duration becomes longer, although the SU has more opportunities to access the channel, it may encounter higher interference due to primary user (PU) returns and the probability of collision becomes higher. In this article, in a decentralised slotted protocol for CRN, the SU spectrum access is proved as a renewal process, then the interference due to PU return during SU transmission, the missed opportunities due to waiting for the channel to become idle and the energy consumed by the SU in the whole spectrum access process including idling energy, transmission energy and sensing energy consumption are formulated and integrated into newly defined efficiency to obtain the optimum transmission time and waiting time.

Performance Comparison of Routing Protocols for Cognitive Radio Networks

Cognitive radio networks (CRNs) have emerged as a promising solution to the ever-growing demand for additional spectrum resources and more efficient spectrum utilization. A large number of routing protocols for CRNs have been proposed recently, each based on different design goals, and evaluated in different scenarios, under different assumptions. However, little is known about the relative performance of all these protocols, let alone the tradeoffs among their different design goals. In this paper, we conduct the first detailed, empirical performance comparison of three representative routing protocols for CRNs, under the same realistic set of assumptions. Our extensive simulation study shows that the performance of routing protocols in CRNs is affected by a number of factors, in addition to PU activity, some of which have been largely ignored by the majority of previous works. We find that different protocols perform well under different scenarios, and investigate the causes of the observed performance. Furthermore, we present a generic software architecture for the experimental evaluation of CRN routing protocols on a testbed based on the USRP2 platform, and compare the performance of two protocols on a 6 node testbed. The testbed results confirm the findings of our simulation study.

Performance study of a CSMA based multiuser MAC protocol for cognitive radio networks: analysis of channel utilization and opportunity perspective

In the overlay medium access control (MAC) of cognitive radio networks, secondary user (SU) uses the spectrum portion which is assigned to primary user (PU), when PU is not using this spectrum at that time. In this article, a multiuser overlay MAC protocol is considered in which PUs and SUs are using time division multiple access and carrier sense multiple access (CSMA) MAC schemes, respectively. Firstly, new frame format and algorithm for the proposed MAC protocol are described, then the analytical modelling of this protocol is explained. In the SU network, Markov chain model along with the CSMA protocol is used for better utilization of the opportunity from the PU network (PUN). Channel utilization and probability of success are also derived and analyzed for this protocol with respect to idle time, collision (failure) time, various spectrum opportunities from PUN, number of SUs, and their fairness. This MAC scheme provides the optimal solution for channel utilization under a constraint on the probability of collisions. Numerical results are also provided to validate analysis of proposed MAC protocol and to investigate the performance behaviour of the optimal solution.

A Survey on Routing Protocols for Cognitive Radio Networks

A Survey on Routing Protocols for Cognitive Radio Networks