Real-time Medium Access Control Protocol Research Articles

A Real-Time and Efficient MAC Protocol for Smart Grid Wireless Communications

Communication and information technologies play crucial roles in the smart grid system. Wireless communications offer many unique features to utilities. Real-time capability and high efficiency under heavy load are vital capabilities for smart grid wireless communications. However, the existing medium access control (MAC) protocols for low-rate and short-range wireless transfer in the literature mainly aim to achieve the objectives of low energy consumption and self-configuration and rarely address these requirements under heavy traffic intensity. This paper presents a real-time, efficient, and lightweight MAC (RE-MAC) protocol to support smart grid applications, based on priority node polling and a hybrid scheme. The upper bounds of packet delay are determined using the embedded Markov chain method, and the simulation results demonstrate that the protocol can achieve predictable, real-time, and efficient performance.

A Real-Time MAC Protocol with Extended Backoff Scheme for Wireless Sensor Networks

Wireless sensor networks (WSNs) are formed by a great quantity of sensor nodes, which are consisted of battery-powered and some tiny devices. In WSN, both efficient energy management and Quality of Service (QoS) are important issues for some applications. Real-time services are usually employed to satisfy QoS requirements in critical environment. This paper proposes a real-time MAC (Medium Access Control) protocol with extended backoff scheme for wireless sensor networks. The basic idea of the proposed protocol employs (m,k)-firm constraint scheduling which is to adjust the contention window (CW) around the optimal value for decreasing the dynamic failure and reducing collisions DBP (Distant Based Priority). In the proposed protocol, the scheduling algorithm dynamically assigns uniform transmitting opportunities to each node. Numerical results reveal the effect of the proposed backoff mechanism.

Hierarchical Real-Time MAC Protocol for (m,k)-firm Stream in Wireless Sensor Networks

In wireless sensor networks (WSNs), both efficient energy management and Quality of Service (QoS) are important issues for some applications. For creating robust networks, real-time services are usually employed to satisfy the QoS requirements. In this paper, we proposed a hierarchical real-time MAC (medium access control) protocol for (m,k)-firm constraint in wireless sensor networks shortly called HRTS-MAC. The proposed HRTS-MAC protocol is based on a dynamic priority assignment by (m,k)-firm constraint. In a tree structure topology, the scheduling algorithm assigns uniform transmitting opportunities to each node. The paper also provides experimental results and comparison of the proposed protocol with E_DBP scheduling algorithm.

A real-time and energy-efficient MAC protocol for wireless sensor networks

Energy saving has been the primal issue in designing medium access control (MAC) protocols for wireless sensor networks (WSNs). However, with the advent of new micro electro-mechanical systems (MEMS) technologies and recently thermo-powered and solar-powered sensor nodes – where nodes operate virtually for an unlimited time period – the research community is set to experience many diverse directions in this area. Factors like timeliness, scalability, synchronisation, adaptivity and reliability will play their part in the near future. This paper discusses AREA-MAC, a MAC protocol specially designed for real-time and energy-efficient WSN applications. AREA-MAC reduces latency and energy consumption of nodes by using low power listening (LPL) technique with short preamble messages. Other protocols like B-MAC use long preamble messages that cause higher latency, energy consumption and control overhead. Moreover, AREA-MAC provides reasonable trade-offs between vital parameters such as system fairness, throughp...

Robust implicit EDF

Advances in wireless technology have brought us closer to extensive deployment of distributed real-time embedded systems connected through a wireless channel. The medium-access control (MAC) layer protocol is critical in providing a real-time guarantee. We have devised a real-time wireless MAC protocol, robust implicit earliest deadline first, or RI-EDF. Packets are transmitted according to EDF scheduling rules, offering a protocol that implicitly avoids contention. In the event of a packet loss or a node failure, every node has the opportunity to recover the schedule based on a static recovery priority, offering a protocol that is robust with no central point of failure. We demonstrate in simulations that RI-EDF provides better goodput and lower packet loss than existing protocols like 802.11 PCF and EDCF. In our implementation and distributed control test-bed, we show that RI-EDF provides better throughput than the TinyOS MAC-layer protocol. Overall, RI-EDF provides predictable temporal behavior with minimal impact on node failures, packet losses, and noise in the channel.

Packetized voice transmission using RT-MAC, a wireless real-time medium access control protocol

RT-MAC is a simple, elegant, and robust medium access control (MAC) protocol for use in transmitting real-time data in point-to-point ad hoc wireless local area networks (WLANs). Our enhancement of IEEE 802.11, real-time MAC (RT-MAC), dramatically reduces missed deadlines and packet collisions while increasing throughput by selectively discarding packets and sharing station state information. For example, RT-MAC is able to successfully transmit 40 2-way voice conversations in addition to a normalized offered load of 80%. IEEE 802.11 is only able to transmit 10 2-way conversations under the same conditions. In another instance, RT-MAC reduced packet collisions from 50% to less than 15% while increasing throughput by more than 50%. Herein we extend our previous performance analysis of RT-MAC to include integrated voice-data transmission. Stations using RT-MAC are interoperable with stations using IEEE 802.11 and show a significant performance improvement even when a minority of stations in the network employ RT-MAC.

A real-time medium access control protocol for ad hoc wireless local area networks

We develop and analyze a simple, elegant medium access control (MAC) protocol for use in transmitting real-time data in point to point ad hoc wireless local area networks (WLANs). Our enhancement of IEEE 802.11, real-time MAC (RT-MAC), achieves dramatic reductions in mean delay, missed deadlines, and packet collisions by selectively discarding packets and sharing station state information. For example, in a 50 station network with a normalized offered load of 0.7, mean delay is reduced from more than 14 seconds to less than 45 ms, late packets are reduced from 76% to less than 1%, and packet collisions are reduced from 36% to less than 1%. Regression models are developed from simulation data to describe network behavior in terms of throughput, mean delay, ratio of late packets, and ratio of collisions. Stations using RT-MAC are interoperable with stations using IEEE 802.11.