MAC Layer Access Research Articles

Effect of Increasing Number of Nodes on Performance of SMAC, CSMA/CA and TDMA in MANETs

The importance of Wireless Sensor Network (WSN) increases due to deployment for geographical, environmental and surveillance purpose in war fields. WSN facing several challenges due to its complex nature including key problems, such as routing and medium access control protocols. Several approaches were proposed for the performance evaluation of WSN on the basis of these issues due to the fact that MAC layer access protocols have a great impact on the performance of WSN. In this paper, we investigated the performance evaluation of three well known MAC Access protocols, i.e. sensor medium access control protocol (SMAC), carrier sense multiple access with collision avoidance (CSMA/CA), and time division multiple access (TDMA) over adhoc on demand distance vector (AODV) routing protocol. The number of simulation scenarios were carried out by using NS- 2, the simulation metrics used are throughput, end-to-end delay and energy consumed. Simulation results showed that SMAC out perform CSMA/CA and TDMA by consuming less energy, less end to end delay and high throughput due to contention based approach to access the medium for transmission.

A Cyber Physical Systems Perspective on the Real-time and Reliable Dissemination of Information in Intelligent Transportation Systems

Timely and reliable dissemination of traffic-related information to drivers is a key property that intelligent transportation systems (ITS) should support. Numerous impediments stemming due to (a) physical factors, such as mobility and speed of vehicles, density of vehicles, characteristics of the wireless radio channel, and power and bit rate of radio transceivers, and (b) cyber issues, such as MAC layer access point associations and address resolutions (ARP), network layer addressing, routing and handoffs, and transport layer retransmissions lead to unpredictability in the timely and reliable dissemination of information to drivers. This paper presents compelling arguments in favor of new research directions in this area that are based on a cyber-physical systems (CPS) perspective. In particular, this paper makes three contributions. First, it considers a vehicle-centric perspective to survey and study the physics-and cyber-imposed impediments to the timely and reliable dissemination of information. Second, it presents a promising CPS solution to overcome a subset of the impediments discovered. Third, it outlines lessons learned indicating the need for more focused research and realistic testbeds. The evaluations

Topology and MAC layer access protocol investigation for industrial optical fibre LANs

The application of optical fibre communications technology is advocated for LANs to be employed within an industrial environment. Attributes and drawbacks associated with possible topologies for optical fibre LANs are discussed, and reasons are advanced for the use of a multiple star topology for industrial LANs. Consideration is then given to the use of MAC layer access protocols with industrial traffic, including probable asymmetric traffic loads. A novel adaptive hybrid token-passing CSMA/CD access protocol is suggested for use with a passive star-based industrial optical fibre LAN. Operating details of the hybrid protocol are described together with its computer simulated performance characteristics. In this way, the novel hybrid protocol is shown to perform efficiently with both symmetric and asymmetric traffic load distributions.