644 research outputs found
CR-MAC: A multichannel MAC protocol for cognitive radio ad hoc networks
This paper proposes a cross-layer based cognitive radio multichannel medium
access control (MAC) protocol with TDMA, which integrate the spectrum sensing
at physical (PHY) layer and the packet scheduling at MAC layer, for the ad hoc
wireless networks. The IEEE 802.11 standard allows for the use of multiple
channels available at the PHY layer, but its MAC protocol is designed only for
a single channel. A single channel MAC protocol does not work well in a
multichannel environment, because of the multichannel hidden terminal problem.
Our proposed protocol enables secondary users (SUs) to utilize multiple
channels by switching channels dynamically, thus increasing network throughput.
In our proposed protocol, each SU is equipped with only one spectrum agile
transceiver, but solves the multichannel hidden terminal problem using temporal
synchronization. The proposed cognitive radio MAC (CR-MAC) protocol allows SUs
to identify and use the unused frequency spectrum in a way that constrains the
level of interference to the primary users (PUs). Our scheme improves network
throughput significantly, especially when the network is highly congested. The
simulation results show that our proposed CR-MAC protocol successfully exploits
multiple channels and significantly improves network performance by using the
licensed spectrum band opportunistically and protects PUs from interference,
even in hidden terminal situations.Comment: 14 Pages, International Journa
Efficient medium access control protocol for vehicular ad-hoc networks
Intelligent transportation systems (ITS) have enjoyed a tremendous growth in the last decade and the advancement in communication technologies has played a big role behind the success of ITS. Inter-vehicle communication (IVC) is a critical requirement for ITS and due to the nature of communication, vehicular ad-hoc network technology (VANET) is the most suitable communication technology for inter-vehicle communications. In Practice, however, VANET poses some extreme challenges including dropping out of connections as the moving vehicle moves out of the coverage range, joining of new nodes moving at high speeds, dynamic change in topology and connectivity, time variability of signal strength, throughput and time delay. One of the most challenging issues facing vehicular networks lies in the design of efficient resource management schemes, due to the mobile nature of nodes, delay constraints for safety applications and interference. The main application of VANET in ITS lies in the exchange of safety messages between nodes. Moreover, as the wireless access in vehicular environment (WAVE) moves closer to reality, management of these networks is of increasing concern for ITS designers and other stakeholder groups. As such, management of resources plays a significant role in VANET and ITS. For resource management in VANET, a medium access control protocol is used, which makes sure that limited resources are distributed efficiently. In this thesis, an efficient Multichannel Cognitive MAC (MCM) is developed, which assesses the quality of channel prior to transmission. MCM employs dynamic channel allocation and negotiation algorithms to achieve a significant improvement in channel utilisation, system reliability, and delay constraints while simultaneously addressing Quality of Service. Moreover, modified access priority parameters and safety message acknowledgments will be used to improve the reliability of safety messages. The proposed protocols are implemented using network simulation tools. Extensive experiments demonstrated a faster and more efficient reception of safety messages compared to existing VANET technologies. Finally, improvements in delay and packet delivery ratios are presented
An Energy Efficient Multichannel MAC Protocol for Cognitive Radio Ad Hoc Networks
This paper presents a TDMA based energy efficient cognitive radio
multichannel medium access control (MAC) protocol called ECR-MAC for wireless
Ad Hoc Networks. ECR-MAC requires only a single half-duplex radio transceiver
on each node that integrates the spectrum sensing at physical (PHY) layer and
the packet scheduling at MAC layer. In addition to explicit frequency
negotiation which is adopted by conventional multichannel MAC protocols,
ECR-MAC introduces lightweight explicit time negotiation. This two-dimensional
negotiation enables ECR-MAC to exploit the advantage of both multiple channels
and TDMA, and achieve aggressive power savings by allowing nodes that are not
involved in communication to go into doze mode. The IEEE 802.11 standard allows
for the use of multiple channels available at the PHY layer, but its MAC
protocol is designed only for a single channel. A single channel MAC protocol
does not work well in a multichannel environment, because of the multichannel
hidden terminal problem. The proposed energy efficient ECR-MAC protocol allows
SUs to identify and use the unused frequency spectrum in a way that constrains
the level of interference to the primary users (PUs). Extensive simulation
results show that our proposed ECR-MAC protocol successfully exploits multiple
channels and significantly improves network performance by using the licensed
spectrum band opportunistically and protects QoS provisioning over cognitive
radio ad hoc networks.Comment: 8 Pages, International Journa
An Energy Efficient MAC Protocol for QoS Provisioning in Cognitive Radio Ad Hoc Networks
The explosive growth in the use of real-time applications on mobile devices has resulted in new challenges to the design of medium access control (MAC) protocols for ad hoc networks. In this paper, we propose an energy efficient cognitive radio (CR) MAC protocol for QoS provisioning called ECRQ-MAC, which integrate the spectrum sensing at physical (PHY) layer and the channel-timeslots allocation at MAC layer. We consider the problem of providing QoS guarantee to CR users as well as to maintain the most efficient use of scarce bandwidth resources. The ECRQ-MAC protocol exploits the advantage of both multiple channels and TDMA, and achieves aggressive power savings by allowing CR users that are not involved in communication to go into sleep mode. The proposed ECRQ-MAC protocol allows CR users to identify and use the unused frequency spectrum of licensed band in a way that constrains the level of interference to the primary users (PUs). Our scheme improves network throughput significantly, especially when the network is highly congested. The simulation results show that our proposed protocol successfully exploits multiple channels and significantly improves network performance by using the licensed spectrum opportunistically and protects QoS provisioning over cognitive radio ad hoc networks
Internet Traffic based Channel Selection in Multi-Radio Multi-Channel Wireless Mesh Networks
Wireless Mesh Networks(WMNs) are the outstanding technology to facilitate wireless broadband Internet access to users. Routers in WMN have multiple radio interfaces to which multiple orthogonal/partially overlapping channels are assigned to improve the capacity of WMN. This paper is focused on channel selection problem in WMN since proper channel selection to radio interfaces of mesh router increases the performance of WMN. To access the Internet through WMN, the users have to associate with one of the mesh routers. Since most of the Internet Servers are still in wired networks, the major dominant traffic of Internet users is in downlink direction i.e. from the gateway of WMN to user. This paper proposes a new method of channel selection to improve the user performance in downlink direction of Internet traffic. The method is scalable and completely distributed solution to the problem of channel selection in WMN. The simulation results indicate the significant improvement in user performance
Multi-channel Utilization Algorithms for IEEE 802.15.4 based Wireless Network: A Survey
In the pass years, IEEE 802.15.4 based Wireless Sensor Networks (WSNs) have received great attention and have been employed in many areas such as inventory checking, local monitoring and alarming etc. One of the key issues affecting WSN's system performance is interference caused by devices operating with the same or different standards on the overlapping frequency within the 2.4 GHz ISM band. This paper addresses the coexistence problem, which is the key motivation for the necessity of flexible channel usage. A review of existing approaches being proposed to date supporting multi-channel utilization in IEEE 802.15.4 based WSNs is categorized and discussed. The paper also presents major functionalities needed in implementing multi-channel utilization
Medium Access Control Protocols for Ad-Hoc Wireless Networks: A Survey
Studies of ad hoc wireless networks are a relatively new field gaining more popularity for various new applications. In these networks, the Medium Access Control (MAC) protocols are responsible for coordinating the access from active nodes. These protocols are of significant importance since the wireless communication channel is inherently prone to errors and unique problems such as the hidden-terminal problem, the exposed-terminal problem, and signal fading effects. Although a lot of research has been conducted on MAC protocols, the various issues involved have mostly been presented in isolation of each other. We therefore make an attempt to present a comprehensive survey of major schemes, integrating various related issues and challenges with a view to providing a big-picture outlook to this vast area. We present a classification of MAC protocols and their brief description, based on their operating principles and underlying features. In conclusion, we present a brief summary of key ideas and a general direction for future work
Thirty Years of Machine Learning: The Road to Pareto-Optimal Wireless Networks
Future wireless networks have a substantial potential in terms of supporting
a broad range of complex compelling applications both in military and civilian
fields, where the users are able to enjoy high-rate, low-latency, low-cost and
reliable information services. Achieving this ambitious goal requires new radio
techniques for adaptive learning and intelligent decision making because of the
complex heterogeneous nature of the network structures and wireless services.
Machine learning (ML) algorithms have great success in supporting big data
analytics, efficient parameter estimation and interactive decision making.
Hence, in this article, we review the thirty-year history of ML by elaborating
on supervised learning, unsupervised learning, reinforcement learning and deep
learning. Furthermore, we investigate their employment in the compelling
applications of wireless networks, including heterogeneous networks (HetNets),
cognitive radios (CR), Internet of things (IoT), machine to machine networks
(M2M), and so on. This article aims for assisting the readers in clarifying the
motivation and methodology of the various ML algorithms, so as to invoke them
for hitherto unexplored services as well as scenarios of future wireless
networks.Comment: 46 pages, 22 fig
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