Cognitive Radio Ad Hoc Networks Research Articles

인지 무선 애드혹 네트워크에서 경로 신뢰성을 고려한 효율적인 라우팅 기법

인지무선 애드혹 네트워크(Cognitive Radio Ad-hoc Networks)에서 요구기반 라우팅을 수행할 경우, 경로 탐색 과정에서 발생하는 경로탐색 메시지의 브로드캐스팅은 공통 제어 채널의 과부하를 유발하고 패킷 간의 충돌을 발생시킨다. 이런 현상은 경로탐색의 오버헤드를 증가 시키며, 정확하고 신뢰성있는 경로의 탐색에 제한을 받게 된다. 이로 인하여 신뢰성있는 채널을 찾는 경로가 제한되기 때문에 경로의 생존 시간이 단축되고 경로의 안정성이 감소된다. 본 논문에서는 인지무선 ad-hoc네트워크에서 주사용자의 출현 가능성과 주변 사용자의 상황을 고려하여 패킷 충돌을 감소시키고 경로의 생존시간을 향상 시키는 라우팅 알고리즘을 제안한다. 각 노드는 주기적인 센싱을 통해 주사용자의 사용패턴을 감지하고 채널의 사용 확률과 현재 채널 상태를 알고 있다. 또한 이웃 노드와 메시지 교환을 통해 공통된 채널과 해당 채널의 품질을 파악하여 노드 사이에 링크 레벨을 부여한다. 제안된 방법에서는 링크 레벨을 이용하여 경로 탐색 과정에서 발생하는 제어 메시지의 수를 감소시킨다. 또한 링크의 생존성과 품질을 홉 카운트에 따라 가중치를 부여하여 경로를 선택함으로써 경로의 생존 시간을 향상 시킬 수 있다. 성능 평가를 통해 기존의 방법 보다 제안된 방법을 이용하여 라우팅을 수행할 경우 제어 채널의 오버헤드가 감소되고 경로의 생존시간이 증가하는 것을 확인 할 수 있다. In the case of On-demand routing protocol in cognitive radio ad-hoc networks, broadcasting of control packets may occur common control channel overload and packet collisions during the routing procedure. This situation is to increase the overhead of path finding and also limited to find the accurate and reliable path. Since reliable channel and path finding is restricted, path life time is shorten and path reliability is reduced. In this paper, we propose a new routing algorithm that reduces control channel overhead and increases path life time by considering the probability of appearance of primary user and channel status of neighbor nodes. Each node performs periodic local sensing to detect primary user signal and to derive primary user activity patterns. The probability of primary appearance on the current channel and the channel status can be obtained based on the periodic sensing. In addition, each node identifies the quality of the channel by message exchange through a common channel with neighbor nodes, then determines Link_Levels with neighbor nodes. In the proposed method, the Link Level condition reduces the number of control messages that are generated during the route discovery process. The proposed method can improve path life time by choosing a path through Path_Reliability in which stability and quality are weighted depending on the location. Through simulation, we show that our proposed algorithm reduces packet collisions and increases path life time in comparison with the traditional algorithm.

SoRoute: a reliable and effective social-based routing in cognitive radio ad hoc networks

A cognitive radio ad hoc network (CRAHN) can be considered as a special delay tolerant network (DTN) that is composed of mobile secondary users (SUs) with social characteristics. Given intermittent connectivity and spectrum availability, it is a challenging issue regarding how to transmit messages between SUs in a reliable and effective way in CRAHNs. To tackle this challenge, we propose a social-aware opportunistic routing and relay selection scheme, called SoRoute, which first predicts the link reliability based on a new social-relationship-aware mobility model and then fuses the relationships of SUs to make a routing and relay decision. In our design, different prediction schemes are employed for the nodes with different relationships. A message is forwarded to the relay node with the largest encounter probability with the destination. The evaluation results demonstrate that our social-based opportunistic routing scheme significantly improves the performance compared to the existing routing schemes such as Direct Delivery, First Contact, MaxProp, and Prophet.

Cognitive cross-layer multipath probabilistic routing for cognitive networks

Mobile Ad-hoc NETworks (MANETs) is a set of mobile nodes that can move around arbitrarily, and communicate with others in a multi-hop fashion without any assistance of base stations. With recent advances in Cognitive Radio (CR) technology, it is possible to apply the Dynamic Spectrum Access model in MANETs. This introduces the concept of Cognitive Radio Ad Hoc Networks (CRAHNs). Applying CR techniques provides better throughput, even in congested spectrum along with better propagation characteristics. CRAHN is a kind of intelligent network that is aware of its surrounding environment, and adapts to the transmission or reception parameters to achieve efficient communication without interfering with primary users. Routing in CR environment is a challenging task as the availability of channel is constrained by the presence of primary user. The problem of routing in CRAHNs targets the creation and maintenance of wireless multi-hop paths among cognitive nodes by deciding both the spectrum to be used and the relay nodes of the path. This paper proposes a cognitive cross-layer multipath probabilistic routing for cognitive radio based networks. The proposed solution uses spectrum holes identified by MAC layer, decides the channel to be used and transmit power level for each hop in the path. The proposed solution is implemented in NS2, and performance of the proposed solution is compared with the existing solution from the literature. The paper also shows that the proposed solution outperforms existing solution in terms of packet delivery ratio, average end-to-end delay and energy consumed per data packet.

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.

Cost-Based Stackelberg Potential Game for Cognitive Radio Ad Hoc Network

In cognitive radio ad hoc networks, the opportunistic access of vacant wireless channel opens a new frontier for efficient spectrum utilization as in many situations, a wide range of spectrum is not even partially utilized by the license owners (primary users, PUs). While the idea seems to be lucrative for spectrum hungry users without licenses, a natural competition between potential stake holders arises, which needs to be regulated in order to efficiently utilize available resources and avoid chaos. With the introduction of unlicensed users in licensed bands, the operations and interests of PUs need to be protected, hence the spectrum owners are given an advantage and control over the multiple access policy (a leader-follower scenario). In this work, we address the problems in spectrum access and channel selection equilibrium in a leader (PU)-follower (secondary user, SU) setup. In contrast to previous game formulations that lack efficient power and pricing schemes, we present a cooperative Stackelberg potential game for cognitive players. A dynamic cost function is articulated to induce awareness in players to mitigate the effects of selfish choices in spectrum access while at the same time steer the distributed network towards achieving Nash equilibrium. The proposed scheme is mutually beneficial for all players and focuses on improving the network performance and power efficiency. We design the network potential function such that the nodes have performance based incentives to cooperate and achieve a Nash equilibrium solution for efficient channel acquisition and capacity. Simulation results show fast convergence in channel selection strategies and increase in capacity for the entire network.

DCEEMR: A Delay-Constrained Energy Efficient Multicast Routing Algorithm in Cognitive Radio Ad Hoc Networks

We discuss the delay-constrained energy efficient multicast routing problem in cognitive radio ad hoc networks. A cognitive radio ad hoc network is a wireless multihop network established by secondary users on varying available spectrum bands. The research on routing is a hot topic in the field of cognitive radio ad hoc networks. However, multicast routing algorithm study of cognitive radio ad hoc networks is still at its start stage. In this paper, we proposed a novel delay-constrained energy efficient multicast routing algorithm (DCEEMR) in cognitive radio ad hoc networks. The DCEEMR guarantees that the multicast tree can be found if it exists, and the multicast tree satisfies the delay bound and has low energy consumption. The algorithm uses delay-energy function to construct the multicast tree based on the spectrum selection. Through an example with random network topology, we demonstrate that our algorithm is better in terms of energy cost of multicast tree as compared to the existing algorithm QoS dependent multicast routing (QDMR). Moreover, the algorithm does not suffer from high complexity common to the algorithm QDMR. Experiment results by NS-2 show that the delay and cost of tree are lower than well-known multicast ad hoc on-demand distance vector (MAODV) protocol.

Mobility-Assisted Routing in Intermittently Connected Mobile Cognitive Radio Networks

In mobile ad-hoc cognitive radio networks (CRNs), end-to-end paths with available spectrum bands for secondary users may exist temporarily, or may never exist, due to the dynamism of the primary user activities. Traditional CRN routing algorithms, which typically ignore the intermittent connectivity of network topology, and traditional mobility-assisted routing algorithms, which generally overlook the spectrum availability, are obviously unsuitable. To tackle this challenge, we propose a Mobility-Assisted Routing algorithm with Spectrum Awareness (MARSA) to select relays based on not only the probability that a node meets the destination but also the chance at which there exists at least one available channel when they meet. To the best of our knowledge, this paper is the first to bring the idea of mobility-assisted routing to deal with the intermittently connected attribute of mobile ad-hoc CRNs, and the first to enhance the mobility-assisted routing by considering the temporal , spatial, and spectrum domains at the same time. Our simulation results demonstrate the superiority of MARSA over traditional algorithms in intermittently connected mobile CRNs.

Performance Evaluation of Transport Layer in Cognitive Radio Ad-hoc Networks

this paper, we have proposed some changes to MAC protocol for improving the performance of transport layer in cognitive radio ad-hoc networks. We have studied effects of different MAC and routing protocols on TCP in cognitive radio technology enabled environments. We have reviewed performance of TCP in two different situations. In first situation, all users are secondary users while in second situation both of primary and secondary users exist. We used CRCN simulator which is based on NS2. We added cognitive radio qualifications to different MAC protocols by sequential MAC method. This method appoints prioritized access for primary users in specified channels in offline mode with acceptable overhead. As we know, route failure is a notable problem in network layer so we handle different routing protocols in ad-hoc networks. We observed routing algorithms based on maintenance of multiple routes and periodic messages for route checking has appropriate effect on TCP performance. Simulation results shows our changed MAC protocols have better performance in Throughput, End to End Delay and Packet Delivery Ratio than prepared MAC protocol for CRNs.

L2ER: Low-Latency and Energy-Based Routing Protocol for Cognitive Radio Ad Hoc Networks

Cognitive radio ad hoc networks (CRAHNs) are active, self-organized, and dynamic networks, in which cognitive users can communicate with each other in an ad hoc fashion. Various delay and energy-based routing protocols have been proposed for CRAHNs. However, these protocols do not consider the delay and node energy in the routing process, which can significantly affect performance. Delay and node energy are important factors in ad hoc networks in which devices have limited power. In this paper, we propose a new routing protocol, named low-latency and energy-based routing (L2ER) protocol; it considers both delay and energy for the routing decisions in CRAHNs. The performances of the proposed protocol are evaluated comparing to two other protocols in terms of average throughput, end-to-end delay, packet delivery ratio, and network lifetime. Simulation results show that the proposed protocol performs better than the existing protocols in many aspects.

A distributed power allocation scheme in green cognitive radio ad hoc networks

For the realization of green communications in cognitive radio ad hoc networks (CRAHNs), self- adaptive and efficient power allocation for secondary users (SUs) is essential. With the distributed and time- varying network topology, it needs to consider how to optimize the throughput and power consuming, avoid the interference to primary users (PUs) and other SUs, and pay attention to the convergence and fairness of the algorithm. In this study, this problem is modeled as a constraint optimization problem. Each SU would adjust its power and corresponding strategy with the goal of maximizing its throughput. By studying the interactions between SUs in power allocation and strategy selection, we introduce best-response dynamics game theory and prove the existence of Nash equilibrium (NE) point for performance analysis. We further design a fully distributed algorithm to make the SUs formulate their strategy based on their utility functions, the strategy and number of neighbors in local area. Compared with the water-filling (WF) algorithm, the proposed scheme can significantly increase convergent speed and average throughput, and decrease the power consuming of SUs.

Prioritized Medium Access Control in Cognitive Radio Ad Hoc Networks: Protocol and Analysis

Cognitive radio (CR) technology enables opportunistic exploration of unused licensed channels. By giving secondary users (SUs) the capability to utilize the licensed channels (LCs) when there are no primary users (PUs) present, the CR increases spectrum utilization and ameliorates the problem of spectrum shortage. However, the absence of a central controller in CR ad hoc network (CRAHN) introduces many challenges in the efficient selection of appropriate data and backup channels. Maintenance of the backup channels as well as managing the sudden appearance of PUs are critical issues for effective operation of CR. In this paper, a prioritized medium access control protocol for CRAHN, PCR-MAC, is developed which opportunistically selects the optimal data and backup channels from a list of available channels. We also design a scheme for reliable switching of a SU from the data channel to the backup channel and vice-versa. Thus, PCR-MAC increases network throughput and decreases SUs' blocking rate. We also develop a Markov chain-based performance analysis model for the proposed PCR-MAC protocol. Our simulations, carried out in $$NS-3$$NS-3, show that the proposed PCR-MAC outperforms other state-of-the-art opportunistic medium access control protocols for CRAHNs.

A Novel Unified Analytical Model for Broadcast Protocols in Multi-Hop Cognitive Radio Ad Hoc Networks

Broadcast is an important operation in wireless ad hoc networks where control information is usually propagated as broadcasts for the realization of most networking protocols. In traditional ad hoc networks, since the spectrum availability is uniform, broadcasts are delivered via a common channel which can be heard by all users in a network. However, in cognitive radio (CR) ad hoc networks, different unlicensed users may acquire different available channels depending on the locations and traffic of licensed users. This non-uniform channel availability leads to several significant differences and causes unique challenges when analyzing the performance of broadcast protocols in CR ad hoc networks. In this paper, a novel unified analytical model is proposed to address these challenges. Our proposed analytical model can be applied to any broadcast protocol with any CR network topology. We propose to decompose an intricate network into several simple networks which are tractable for analysis. We also propose systematic methodologies for such decomposition. Results from both the hardware implementation and software simulation validate the analysis well. To the best of our knowledge, this is the first analytical work on the performance analysis of broadcast protocols for multi-hop CR ad hoc networks.

The Research of Self-Adaptative Power Adjustment Routing

Cognitive Radio Ad Hoc Network (CRAHN), established on the cognitive radio environment, configures the Ad Hoc Network which possesses the internal capacity. How to effectively control the power consumption is an important issue in the CRAHN for CRAHN‘s main power type is battery. At present, the energy-saving routing research in CRAHN is mainly based on the real-time routing mechanism. It means that it should be routed again after transferring an archive. In order to increase the network route’s surviving time and save the power consumption, it introduces a routing mechanism whose purpose is to optimize the communication algorithm’s performance by improving the existing routing mechanism in the Ad Hoc network.

Spectrum-Map-Empowered Opportunistic Routing for Cognitive Radio Ad Hoc Networks

Cognitive radio (CR) has emerged as a key technology for enhancing spectrum efficiency by creating opportunistic transmission links. Supporting the routing function on top of opportunistic links is a must for transporting packets in a CR ad hoc network (CRAHN) consisting of cooperative relay multiradio systems. However, there lacks a thorough understanding of these highly dynamic opportunistic links and a reliable end-to-end transportation mechanism over the network. Aspiring to meet this need, with innovative establishment of the spectrum map from local sensing information, we first provide a mathematical analysis to deal with transmission delay over such opportunistic links. Benefitting from the theoretical derivations, we then propose spectrum-map-empowered opportunistic routing protocols for regular and large-scale CRAHNs with wireless fading channels, employing a cooperative networking scheme to enable multipath transmissions. Simulations confirm that our solutions enjoy significant reduction of end-to-end delay and achieve dependable communications for CRAHNs, without commonly needed feedback information from nodes in a CRAHN to significantly save the communication overhead at the same time.

Distributed Scheduling in MIMO Empowered Cognitive Radio Ad Hoc Networks

Two fast growing technologies, MIMO and cognitive radio (CR), can both effectively combat the transmission interference among links and thus increase the network throughput. MIMO exploits spatial degree of freedom (DoF) through spatial multiplexing and interference cancellation within the same frequency channel, while CR exploits all available frequency channels for transmissions. We consider an ad hoc network where each node is equipped with an array of cognitive radios. A radio can tune to a different channel and transmit independently, or transmit together with other radios on the same channel using MIMO mode. Additionally, different frequency and spatial channels could have different conditions. There is a big challenge for nodes to distributively coordinate in selecting a transmission channel and/or a spatial DoF taking advantage of this unprecedented flexibility and diversity of channels for a higher network performance. In this work, we mathematically model the opportunities and constraints for such a network with the objective of maximizing the weighted network throughput. We propose a centralized algorithm as our comparison benchmark, and a distributed algorithm to flexibly assign spectrum channel or spatial DoF exploiting the multiuser diversity, channel diversity and spatial diversity for a higher performance in a practical network. The algorithm further supports different transmission priorities, reduces transmission delay and ensures fair transmissions among nodes by providing all nodes with certain transmission probability. The performance of our algorithms are studied through extensive simulations and the results demonstrate that our algorithm is very effective and can significantly increase the network throughput while reducing the delay.

Performance Comparison of AODV and CAODV Routing Protocol using Cognitive Radios

The Cognitive Radio (CR) technology has evolved in the recent past to solve the problem of wireless networks resulting from the limited available spectrum. The networks employing cognitive radios are termed as Cognitive Radio Ad hoc Networks (CRAHN). These networks employ: Primary Users (PUs) and Secondary Users (SUs), PU is the one that have licensed band while the SU uses the licensed band of PU opportunistically for communication purpose. To have communication in CRAHN, a routing protocol is required. The performance of this protocol depends upon various factors such as: mobility, transmission range, number of nodes deployed and environment. This paper is an effort to measure the efficacy of routing protocol by varying the above mentioned factors. For this purpose we implemented a Cognitive Ad hoc On demand Distance Vector (CAODV) routing protocol in MATLAb-09. Moreover, this paper also shows the advantage of CAODV over the standard protocol AODV.

Analytical Modeling of Ad Hoc Cognitive Radio Environment for Optimum Power Control

Radio is an emerging wireless technology that has grabbed the attention of researchers, academicians, and telecommunication industries worldwide. Recent survey reports show that unlicensed frequency bands have become overcrowded from past few years with widespread acceptance of diverse wireless technology applications whereas, licensed frequency bands are being used intermittently. To deal with the conflicts between unlicensed spectrum overuse and underutilization of licensed frequency band, Cognitive Radio technology has been evolved eventually. It allows unlicensed subscribers to access licensed subscriber frequency band with some power constraints such that minimum or no interference should be experienced by primary user and its quality of service should not be affected while sharing its spectrum with unlicensed secondary subscriber. In this paper, distance based power control scheme has been analyzed for overlay ad-hoc cognitive radio network. It is shown that algorithm provides optimum power control as long as the separation between cognitive transmitter and receiver is greater than or equals to maximum decodable radius of primary transmitter. Keywordscommunication commission (FCC), Primary user (PU), secondary User (SU), Quality of services (QoS), Cognitive Radio (CR).

Secure Routing and Scheduling in Ad-Hoc Cognitive Radio Networks for Public Safety

Public safety communication is a critical component of day-to-day life. The authors propose a flexible and resilient communication system using an ad-hoc cognitive radio network that fully utilizes the available spectrum resources. Two main components of the network are addressed: route discovery, i.e., identifying multiple paths from the source to the destination, and scheduling for these paths, i.e., efficiently allocating available resources to achieve an optimal transmission. Field-based routing is adopted. The authors also introduce a secure authentication and routing mechanism for this network. The authentication component leverages the social aspect of public safety communications and mitigates most basic wireless attacks. A hybrid novel reputation scheme is then proposed to allow for efficient routing in the presence of adversaries. The authors show through simulations that the proposed secure framework can efficiently reduce the transmission delay, be robust to the dynamics of channel availability, and mitigate routing attacks in a cognitive radio network.

Enhancing Detection Rate by using Distributed Reaction Mechanisms in Cognitive Radio Ad-Hoc Networks

Cognitive radio (CR) is a promising technology in ad-hoc networks to solve the problems that result from the limited available spectrum and the inefficiency in the spectrum usage by utilizing the existing wireless spectrum advantageously. When the licensed primary user is not using the spectrum, the available channels are allocated for the unlicensed secondary users. An increasing numbers of security threats are being identified when the idea of cognitive radio becomes reality. One such threat is the possible presence of selfish secondary users who try to occupy all available channels. In this paper, an efficient selfish attack detection technique called Distributed Reaction Mechanism is introduced and implemented which results in enhanced detection rate.

MAC Protocols in Cognitive Radio Ad Hoc Networks

MAC Protocols in Cognitive Radio Ad Hoc Networks