Time Division Multiple Access MAC Research Articles

AdaptiveHART: An Adaptive Real-Time MAC Protocol for Industrial Internet-of-Things

Wireless sensor–actuator networks (WSAN) for real-time reliable communications are being embraced in the Industrial Internet of Things. One key property required for WSAN is <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">adaptability</i> with respect to dynamic environments. Most existing studies assume that a network manager computes global schedules and disseminates schedule information to every node whenever the network parameters need to be updated. Such a centralized approach may degrade control performance due to nonreal-time response to dynamic environments. In this article, we introduce a novel time division multiple access MAC protocol, AdaptiveHART, which updates the network parameters in real-time without the dissemination intervals. AdaptiveHART achieves a reduction in adaptation latency up to 74%, maximum schedulable ratio, and control performance up to 75% than the conventional WirelessHART. We assess our protocol using a stochastic response time analysis, which provides an accurate end-to-end delay distribution and a schedulability condition that can guarantee real-time performance in WSAN.

Impairments-aware time slot allocation model for energy-constrained multi-hop clustered IoT nodes considering TDMA and DSSS MAC protocols

The possibility of Internet of Things (IoT) is that a large number of live items (e.g., apparatuses) in the network are available, detected, and interconnected. In any case, the performance of IoT networks may be limited due to several impairments, most importantly, the energy-constrained IoT nodes. In fact, this limitation opens the door to many researchers where using network clustering has proven to be efficient energy saving mechanism. To the best of our knowledge, there are no prior research, in the field of multi-hop clustered IoT networks, which addressed the energy-constrained IoT nodes problem along with the delay in receiving data messages from devices, located far away from the remote users (or control center), in timely basis. Practically, it is significantly challenging to contemplate and clarify this issue. Consequently, in this paper, we make major amendments on the prior work, Improved Energy and Distance Based CH Selection with Balanced Objective Function (IEDB-CHS-BOF), and particularly propose a multi-hop routing (MR) protocol in which the IoT network is divided into a number of virtual sections with lengths held below the cross-over communication distance, thereby ensuring minimal energy depletion. Over those virtual sections, efficient forwarder and cluster head selection algorithms are further proposed. Interestingly, we propose a novel delay-, power-, and interference-aware time slot allocation model in which Time Division Multiple Access (TDMA) and Direct Sequence Spread Spectrum (DSSS) MAC protocols are operated. Furthermore, it is a good representation of the above-mentioned proposals. As a result, our protocols are referred to as MR-IEDB-CHS-TDMA and MR-IEDB-CHS-DSSS, respectively. To this end, numerous simulations have been conducted for evaluating the performance of the proposed protocols in the perspective of IoT network lifetime. In addition, sufficient comparisons have been conducted with the existing state-of-the-art protocols. In overall, the MR-IEDB-CHS-TDMA protocol keeps the IoT network functioning the longest.

Optimisation‐based time slot assignment and synchronisation for TDMA MAC in industrial wireless sensor network

Wireless sensor network in the industrial environment [industrial wireless sensor network (IWSN)] has data delivery time constraint. Due to the dynamic routing and transmission collision, the data delivery time is unpredictable. The authors utilised time division multiple access (TDMA) MAC to avoid data collision and to provide bounded transmission delay. Moreover, a linear programming model is proposed to construct the TDMA schedules, which is focused on spatial reuse and fixed routing in IWSN. The objective function of the model is to minimise the time slot usage to increase the overall network bandwidth. Finally, both simulated annealing algorithm and particle swarm optimisation are applied to approximate the optimal solution of time slot usage.

Det-WiFi: A Multihop TDMA MAC Implementation for Industrial Deterministic Applications Based on Commodity 802.11 Hardware

Wireless control system for industrial automation has been gaining increasing popularity in recent years thanks to their ease of deployment and the low cost of their components. However, traditional low sample rate industrial wireless sensor networks cannot support high-speed application, while high-speed IEEE 802.11 networks are not designed for real-time application and not able to provide deterministic feature. Thus, in this paper, we propose Det-WiFi, a real-time TDMA MAC implementation for high-speed multihop industrial application. It is able to support high-speed applications and provide deterministic network features since it combines the advantages of high-speed IEEE802.11 physical layer and a software Time Division Multiple Access (TDMA) based MAC layer. We implement Det-WiFi on commercial off-the-shelf hardware and compare the deterministic performance between 802.11s and Det-WiFi under the real industrial environment, which is full of field devices and industrial equipment. We changed the hop number and the packet payload size in each experiment, and all of the results show that Det-WiFi has better deterministic performance.

Pre-Emptive Traffic Management for a Cluster-Based TDMA System in Vehicular Communications

The IEEE 802.11p is a standard in a vehicular communication system, known as Wireless Access in Vehicular Environment (WAVE). An implementation of that standard as the MAC Protocol in a high-density of nodes in Vehicular Ad-Hoc Networks (VANETs) may create a performance drawback, in particular for packet loss and delay whenever collisions happen. Introducing Time Division Multiple Access (TDMA) schemes can improve the performance. However, TDMA scheduling is difficult to manage the case of high-density of traffic, the high mobility of vehicles, and dynamic network topology. This journal proposes a clustered-based TDMA by traffic priority in VANETs. The clustered traffic is defined as high and low traffic priority and embedded in TDMA MAC Header. The evaluation result obtained through NS3 Simulator shows that the proposed approach performed better in a high-density of nodes.

Robust Ad-hoc Sensor Routing (RASeR) protocol for mobile wireless sensor networks

Robust Ad-hoc Sensor Routing (RASeR) is a novel protocol for data routing in mobile wireless sensor networks (MWSNs). It is designed to cope with the demanding requirements of emerging technologies, which require the reliable and low-latency delivery of packets in highly mobile conditions. RASeR uses blind forwarding, which is facilitated by a novel method of gradient maintenance. The problem of maintaining a gradient field in a changing topology, without flooding, is solved by using a global time division multiple access MAC. Furthermore, it is enhanced with the additional options of a supersede mode, to aid time-critical applications, reverse flooding, to allow sink-to-sensor commands and energy saving sleep cycles to reduce power consumption. Analytical expressions are derived and verified by simulation. RASeR is compared with the state-of-the-art MWSN routing protocols, PHASeR and MACRO, as well as the MANET protocols, AODV and OLSR. The results indicate that RASeR is a high performance protocol, which shows improvements over PHASeR, MACRO, AODV and OLSR. Tested over varying levels of mobility, scalability and traffic, the simulations yield near perfect PDR in many scenarios, as well as a low end-to-end delay, high throughput, low overhead and low energy consumption. The robustness of this protocol and its consistent reliability, low latency and additional features, makes it highly suitable to a wide number of applications. It is specifically applicable to highly mobile situations with a fixed number of nodes and small payloads.

Location-Based TDMA MAC for Reliable Aeronautical Communications

The growth of data traffic as air traffic increases is leading to bottlenecks. We propose a new time division multiple access (TDMA) protocol termed location-based TDMA (LBTM) to accommodate increasing data traffic and air-to-air communications. LBTM provides all three modes of communication: unicast, multicast, and broadcast. ACK needs a long guard time for reliable multicast in the aeronautical environment, because it is a long distance communication system. LBTM uses location information to overcome this problem. We can reduce the guard time of ACK and prevent collisions. In our scheme, multicast aircraft calculate ACK arrival time to ensure that ACKs arrive at the sender at different times. Therefore, LBTM reduces the amount of guard time of ACK and the total average time to complete a reliable multicast MAC request. This results in a significant increase in network utilization and throughput.

Pairwise: a time hopping medium access control protocol for wireless sensor networks

The availability of low cost, multifunctional embedded devices have become ubiquitous due to their wide ranging application that includes monitoring Radio Frequency Identification (RFID) tagged objects to ambient conditions such as temperature and humidity. Also, these devices can be equipped with a camera and then deployed in hostile environments. A key characteristic of these devices is that they can communicate wirelessly and form an ad-hoc, Wireless Sensor Network (WSN). Devices in a WSN then collaboratively monitor environment factors or objects, and forward data back to one or more central nodes. A key challenge in WSN is ensuring nodes operate in the order of months as they have limited energy resource, and it is impractical to replace their batteries due to their large numbers, and they may be deployed in inaccessible terrains. Hence, it is critical that these devices or nodes employ energy efficient protocols. To this end, we present PairWise, a novel, low power, time division multiple access (TDMA) based protocol for use in WSNs. PairWise is easily deployable in large scale WSNs as nodes are not synchronized globally. Instead, they synchronize and establish a pair of channels with each of their neighbors independently. Each channel hops pseudo randomly in time according to a seed and maximum rendezvous period (MRP). Hence, nodes using PairWise experience very minimal to no collision during communications. Apart from that, higher layer protocols are able to control the MRP of each channel such that a node's duty cycle matches the observed traffic load. We have implemented PairWise in the ns-2 simulator, and compared it to Sensor Medium Access Control (S-MAC) and a TDMA MAC. Our results show PairWise to have very low power consumption whilst ensuring packets have minimal delays. Moreover, PairWise has a high goodput with increasing node density, where goodput is defined as the number of packets that are transmitted by each node pair successfully over a given total number of packets.

Ad hoc on demand multipath distance vector routing (AOMDV) over a distributed TDMA MAC protocol for QoS support in wireless ad hoc networks: integration issues and performance evaluation

AbstractThis paper focuses on the problem of QoS multi‐path in wireless ad hoc networks. An integration of a novel multi‐path routing protocol and a distributed time division multiple access (TDMA) MAC protocol is proposed. The MAC considered is called evolutionary TDMA (E‐TDMA) and the analysed multi‐path routing protocol is the ad hoc on demand multi‐path distance vector (AOMDV) protocol. The integrated approach multi‐path routing and TDMA MAC protocol offers advantages typical of multi‐path routing, in terms of reduced route discovery frequency and increased throughput. The advantage of the E‐TDMA MAC is a higher throughput in comparison with the standard IEEE 802.11 MAC and the reduction of the contention interference due to the slot reservation mechanism for high‐data traffic. Two schemes to build the multi‐route are exploited. The simulation results show the benefits of the integrated routing‐MAC protocol in terms of reduced overhead, higher throughput and reduced end‐to‐end delay for a scenario with very high mobility and heavy data traffic. Copyright © 2006 AEIT