Time Division Multiple Access Slot Research Articles

An Innovative Clustering Hierarchical Protocol for Data Collection from Remote Wireless Sensor Networks Based Internet of Things Applications

Recently, unmanned aerial vehicles (UAVs) have emerged as a viable solution for data collection from remote Internet of Things (IoT) applications. However, the successful implementation in this regard necessitates the development of a reliable and energy-efficient routing protocol. This paper proposes a reliable and an energy-efficient UAV-assisted clustering hierarchical (EEUCH) protocol designed for remote wireless sensor networks (WSNs) based IoT applications. The proposed EEUCH routing protocol facilitates UAVs to collect data from ground sensor nodes (SNs) that are equipped with wake-up radios (WuRs) and deployed remotely from the base station (BS) in the field of interest (FoI). During each round of the EEUCH protocol, the UAVs arrive at the predefined hovering positions at the FoI, perform clear channel assignment, and broadcast wake-up calls (WuCs) to the SNs. Upon receiving the WuCs by the SNs’ wake-up receivers, the SNs perform carrier sense multiple access/collision avoidance before sending joining requests to ensure reliability and cluster-memberships with the particular UAV whose WuC is received. The cluster-member SNs turn on their main radios (MRs) for data packet transmission. The UAV assigns time division multiple access (TDMA) slots to each of its cluster-member SNs whose joining request is received. Each SN must send the data packets in its assigned TDMA slot. When data packets are successfully received by the UAV, it sends acknowledgments to the SNs, after which the SNs turn off their MRs, completing a single round of the protocol. The proposed EEUCH routing protocol with WuR eliminates the issue of cluster overlapping, improves the overall performance, and increases network stability time by a factor of 8.7. It also improves energy efficiency by a factor of 12.55, resulting in a longer network lifespan compared to Low Energy Adaptive Clustering Hierarchy (LEACH) protocol. Moreover, EEUCH collects 5.05 times more data from the FoI than LEACH. These results are based on simulations in which the EEUCH protocol outperformed the existing six benchmark routing protocols proposed for homogeneous, two-tier, and three-tier heterogeneous WSNs.

TDMA scheduling schemes targeting high channel utilization for energy‐harvesting wireless sensor networks

As a contention-free channel access protocol, Time Division Multiple Access (TDMA) is widely applied in Energy Harvesting Wireless Sensor Networks (EH-WSNs) due to ease of implementation. TDMA scheduling in EH-WSNs faces the problem of low channel utilization since time slots assigned to some nodes may not be used by them due to shortage of energy or data. It is important to design TDMA scheduling schemes that enhance channel utilization. In this paper, the Fixed Frame Size Scheme (FFSS) and the Adaptive Frame Size Scheme (AFSS) are proposed to improve channel utilization of EH-WSNs. The FFSS aims at the optimal TDMA slot assignment for the TDMA scheduling with fixed frame size, and the AFSS considers the TDMA with variable frame size and targets both the optimal frame size and the optimal slot assignment. The optimization problems maximizing channel utilization are formulated for the FFSS and the AFSS, respectively, which take the upcoming energy and data into account. The optimization problems are transformed into assignment-like problems and solved by the Hungarian-based algorithm in polynomial time. Simulation results indicate that the proposed FFSS and AFSS can considerably improve channel utilization in the EH-WSNs compared with the existing TDMA scheduling schemes.

A Dynamic Distributed Multi-Channel TDMA Slot Management Protocol for Ad Hoc Networks

With the emergence of new technologies and standards for wireless communications and an increase in application and user requirements, the number and density of deployed wireless ad hoc networks is increasing. For deterministic ad hoc networks, Time-Division Multiple Access (TDMA) is a popular medium access scheme, with many distributed TDMA scheduling algorithms being proposed. However, with increasing traffic demands and the number of wireless devices, proposed protocols are facing scalability issues. Besides, these protocols are achieving suboptimal spatial spectrum reuse as a result of the unsolved exposed node problem. Due to a shortage of available spectrum, a shift from fixed spectrum allocation to more dynamic spectrum sharing is anticipated. For dynamic spectrum sharing, improved distributed scheduling protocols are needed to increase spectral efficiency and support the coexistence of multiple co-located networks. Hence, in this paper, we propose a dynamic distributed multi-channel TDMA (DDMC-TDMA) slot management protocol based on control messages exchanged between one-hop network neighbors and execution of slot allocation and removal procedures between sender and receiver nodes. DDMC-TDMA is a topology-agnostic slot management protocol suitable for large-scale and high-density ad hoc networks. The performance of DDMC-TDMA has been evaluated for various topologies and scenarios in the ns-3 simulator. Simulation results indicate that DDMC-TDMA offers near-optimal spectrum utilization by solving both hidden and exposed node problems. Moreover, it proves to be a highly scalable protocol, showing no performance degradation for large-scale and high-density networks and achieving coexistence with unknown wireless networks operating in the same wireless domain.

A Robust Approach to TDMA Synchronization in Aerial Networks.

Unmanned Aerial Vehicles (UAVs) can be a powerful tool for live (interactive) remote inspection of large-scale structures or areas of interest. Instead of manual, local, and labor-intensive inspections, we envision human operators working together with networks of semi-autonomous UAVs. The current state-of-the-art for low-delay high-throughput inter-vehicle networking relies on Time-Division Multiple Access (TDMA) techniques that require accurate synchronization among all network nodes. In this paper, we propose a delay-tolerant synchronization approach that converges to the correct order of the TDMA slots implemented over COTS WiFi in a fully-distributed way and without resorting to a global clock. This highly flexible solution allows building an ad-hoc aerial network based on a backbone of relaying UAVs. We show several alternatives to achieve this synchronization in a concrete aerial network and compare them in terms of slots’ overlap, throughput, and packet delivery. The results show that these alternatives lead to trade-offs in the referenced metrics. The results also provide insight into the delays caused by buffering in the protocol stack and especially in the WiFi interface.

Hybrid Slotted-CSMA/CA-TDMA for Efficient Massive Registration of IoT Devices

Recently, the Wi-Fi alliance announced a new Wi-Fi standard known as IEEE 802.11ah (or Wi-Fi HaLow) to efficiently support Internet of Things (IoT) applications. However, the existing registration method under IEEE 802.11ah, based on carrier-sense multiple access with collision avoidance (CSMA/CA), was analyzed as not efficient enough for registration of large-scale machine-to-machine (M2M) communications where a massive number of devices try to access a single, centralized access point (AP). In this paper, we propose a hybrid slotted-CSMA/CA–time-division multiple access (TDMA) (HSCT) medium access control (MAC) protocol for efficient massive registration of IoT devices (up to 8000) in M2M networks. We focus on situations, where a large number of M2M devices simultaneously try to register at a single, centralized AP. In the proposed HSCT, contention-based slotted-CSMA/CA allows devices to send an authentication request via randomly selected backoff slots, whereas contention-free TDMA permits those devices to send/receive the subsequent association request/association response via an individually allocated TDMA slot. In addition, a centralized authentication control (CAC)-based mechanism with modified algorithms for optimal selection of CAC parameters and the slotted fixed-window CSMA protocol with Sift geometric probability distribution are used to mitigate severe contention between massive registrations upon network (re-)initialization from an AP reboot. This paper also analyzes the performance of the proposed scheme and determines the optimal configuration to enhance registration performance. Simulation results demonstrate that the proposed HSCT MAC protocol achieves substantial improvement, compared with the contention-free transmission, a combined authentication/association scheme, and the conventional IEEE 802.11ah with CSMA/CA.

An Efficient Proposed MAC Protocol for M2M Networks

Machine to machine (M2M) communications refer to the technology that enables huge number of devices to be wired or wireless communication with each other’s. Neither the contention based medium access control (MAC) protocols nor the reservation based MAC protocols can provide a flexible, scalable solution for M2M networks. That is because of the huge number of communicating devices. In this paper, an efficient proposed MAC protocol for M2M networks is suggested. It is divided into three periods, namely the notification, the contention and the transmission periods. During the contention period, the contention is occurred with equal probabilities between the devices which have traffic to be sent. The non-persistent carrier sense multiple access protocol is selected for the contention strategy. In the notification period, the devices get information about the contention state. Furthermore, the transmission time slots location for the succeeded ones are announced. Finally, in the transmission period, the packets from each successful contended device are sent. This is done using time division multiple access (TDMA) strategy in the reserved time slot. Moreover, more than one device can transmit in one TDMA slot as long as the signal to interference plus noise ratio condition is not violated. In addition, the analytical analysis of the proposed MAC protocol is produced. Furthermore, extensive simulation programs are executed using MATLAB to measure the system performance. The system throughput, average delay time, and packet collision ratio are our performance metrics. Further, our MAC protocol outperforms other traditional ones.

Resource Allocation in Space Multiaccess Systems

Currently, most Landsat satellites are deployed in the low earth orbit (LEO) to obtain high-resolution data of the Earth surface and atmosphere. However, the return channels of LEO satellites are unstable and discontinuous intrinsically, resulting from the high orbital velocity, long revisit interval, and limited ranges of ground-based radar receivers. Space-based information networks, in which data can be delivered by the cooperative transmission of relay satellites, can greatly expand the spatial transport connection ranges of LEO satellites. While different types of these relay satellites deployed in orbits of different altitudes represent distinctive performances when they are participating in forwarding. In this paper, we consider the cooperative mechanism of relay satellites deployed in the geosynchronous orbit (GEO) and LEO according to their different transport performances and orbital characteristics. To take full advantage of the transmission resource of different kinds of cooperative relays, we propose a multiple access and bandwidth resource allocation strategy for GEO relay, in which the relay can receive and transmit simultaneously according to channel characteristics of space-based systems. Moreover, a time-slot allocation strategy that is based on the slotted time division multiple access is introduced for the system with LEO relays. Based on the queueing theoretic formulation, the stability of the proposed systems and protocols is analyzed and the maximum stable throughput region is derived as well, which provides the guidance for the design of the system optimal control. Simulation results exhibit multiple factors that affect the stable throughput and verify the theoretical analysis.

A Distributed TDMA Scheduling Algorithm Based on Exponential Backoff Rule and Energy-Topology Factor in Internet of Things

In the Internet of Things scene, the wireless sensor network (WSN) is widely used to monitor and perceive various context environments. The efficient utilization of time division multiple access (TDMA) slot resource has attracted more and more attention, especially for applications with high network performance requirements, for example, vehicular networks. The characteristics of the WSN, which have limited battery volume and variable topology structure, restrict the development of the centralized time slot allocation algorithm. Moreover, the traditional distributed time slot allocation algorithm is helpless to reduce the energy consumption, even if the variable topology is solved to some extent. In this paper, we propose the distributed TDMA scheduling algorithm based on exponential backoff rule and energy-topology factor, namely EB-ET-distributed randomized (DRAND) algorithm. We analyze the typical DRAND time slot assignment algorithm and the distributed TDMA slot scheduling algorithm based on energy-topology factor, which is proposed in our another work. By introducing the idea of Lamport’s bakery algorithm, the priority control algorithm based on exponential backoff rules and energy-topology factor are presented to appropriately adjust the priority of time slot allocation and greatly reduce the probabilities of message collision and time slot allocation failure. Then, we introduce the implementation processes of the EB-ET-DRAND scheduling algorithm in various different states. The time slot structure and frame formats of algorithm are designed in detail. Finally, we implement a mesh network simulation system to evaluate the performance of proposed scheme. The experimental results indicate that the EB-ET-DRAND scheduling algorithm greatly improves the performance of time slot allocation and reduces the message complexity, time complexity, and energy consumption.

A Distributed TDMA Scheduling Algorithm Based on Energy-Topology Factor in Internet of Things

In Internet of Things, various things realize interconnection and intercommunication by the wireless sensor network (WSN). The time-division multiple-access (TDMA) slot scheduling algorithm for WSN is a crucial technology for improving network efficiency and prolonging network lifetime. Considering the industrial field of WSN, the problems of limited energy and changed topology restrict the development of the centralized resource allocation. Although some traditional distributed time slot allocation algorithms solve the network topology change to a certain extent, there are still some problems and challenges in terms of efficiency and energy consumption. In this paper, we propose a distributed TDMA slot scheduling algorithm based on energy and topology factor. By analyzing and summarizing the distributed randomized time slot assignment algorithm, it is found that energy and topology information of network nodes are very important for TDMA slot scheduling. Then the definition of energy-topology (E-T) factor is proposed, which is based on the influence of residual energy and topology on the time slot allocation. Moreover, the distributed TDMA slot scheduling algorithm based on E-T factor is proposed by taking the number of neighbors and residual energy of network nodes into consideration to reduce the execution time and energy consumption of algorithm. Finally, we simulate the proposed scheme to evaluate its performance. The experimental results indicate that the proposed algorithm can reduce the message complexity, time complexity, and energy consumption, and improve the efficiency of TDMA slot scheduling.

TQCR‐media access control: two‐level quality of service provisioning media access control protocol for cognitive radio network

Recently cognitive radio has been proposed to solve the problem of spectrum scarcity with the help of an opportunistic utilisation of unused spaces in the spectrum. The implementation of cognitive radio for real-time application faces with the challenge of real-time media access control (MAC) design. To this end the authors propose an energy efficient cognitive radio MAC protocol with two level of quality of service (QoS) support: two level quality of service provisioning in cognitive radio (TQCR)-MAC. The data traffic in the cognitive radio network is classified as real-time traffic and non-real-time traffic, with former having higher priority over latter. The proposed protocol utilises variable interframe spaces for implementing different priorities to data and also exploits the combination of multiple channels and time division multiple access (TDMA) scheme to further improve the QoS provisioning. The TDMA slots in different channels are used as the data carrier segment, in which a real-time data can take over the time slots reserved by non-real-time data. Thus, non-real traffic may suffer from starvation, and hence a guarantee on the non-real-time data is provided with the help of a starvation prevention algorithm. The performance analysis of the proposed MAC protocol is done against two similar MAC protocols, which shows that the performance is improved significantly, especially when the network is either biased towards real-time or non-real-time data traffic.

BOD‐LEACH: broadcasting over duty‐cycled radio using LEACH clustering for delay/power efficient dissimilation in wireless sensor networks

SUMMARYBroadcasting delay‐sensitive information over a duty‐cycled wireless sensor network is considered, and a cluster‐based protocol is proposed. The proposed protocol, namely Broadcast over Duty‐Cycle and LEACH (BOD‐LEACH), takes advantage of the LEACH's energy‐efficient clustering. This approach shifts the total burden of energy consumption of a single cluster head by rotating the cluster‐head role among all nodes in the network. It also permits the ordinary (member) nodes in a cluster to turn off their radios whenever they enter inactive TDMA slots. However, LEACH does not consider broadcast messages, and the member nodes scheduling is established as a sequence of Time Division Multiple Access (TDMA) without any common active period. A broadcast message should then be postponed to the next TDMA schedule and transmitted in a sequence of unicast messages, which is inefficient in terms of latency, bandwidth occupation, and power consumption. The proposed protocol adds new common static and dynamic broadcast periods to support and accelerate broadcasting. The dynamic periods are scheduled following the past arrivals of messages and using a Markov chain model. To our knowledge, this work is the first that proposes the use of clustering to perform simultaneous local broadcasts at several clusters. This reduces broadcast latency and ensures scalability. The protocol has been simulated, numerically analyzed, and compared with LEACH. The results show clear improvement over LEACH with regard to broadcast latency, at a low energy cost. Copyright © 2013 John Wiley & Sons, Ltd.

An Adaptive TDMA Slot Assignment Algorithm for Scalable Wireless Mesh Networks

The media access control (MAC) protocol based on fixed slot allocation has low throughput and high delay in high load wireless mesh network. In order to improve the performance of wireless mesh network, we propose a scalable adaptive time division multiple access (TDMA) slot allocation algorithm based on the existing fixed TDMA. The algorithm uses the network structure of clustering and builds a more optimized frame structure, cluster head dynamically allocates time slot according to the packet number of the cluster member sent and the priority level, at the same time taking into account the situation of nodes joining and leaving to improve the scalability of the network The simulation results on OPNET network simulation platform show that the algorithm is superior to fixed TDMA algorithm in both throughput and delay.

Adaptive TDMA slot assignment protocol for vehicular ad-hoc networks

This paper proposes a novel adaptive time division multiple access (TDMA) slot assignment protocol (ATSA) for vehicular ad-hoc networks. ATSA divides different sets of time slots according to vehicles moving in opposite directions. When a node accesses the networks, it choices a frame length and competes a slot based on its direction and location to communication with the other nodes. Based on the binary tree algorithm, the frame length is dynamically doubled or shortened, and the ratio of two slot sets is adjusted to decrease the probability of transmission collisions. The theoretical analysis proves ATSA protocol can reduce the time delay at least 20% than the media access control protocol for vehicular ad-hoc networks (VeMAC) and 30% than the ad-hoc. The simulation experiment shows that ATSA has a good scalability and the collisions would be reduced about 50% than VeMAC, channel utilization is significantly improved than several existing protocols.

A Quality of Service Supported Time Division Multiple Access Slot Assignment Protocol with Cross Layer Design

A Quality of Service Supported Time Division Multiple Access Slot Assignment Protocol with Cross Layer Design

Evaluation of a TDMA-based energy efficient MAC protocol for multiple capsule networks

Abstract Wireless capsule endoscopy is a new kind of medical device, which monitors the gastrointestinal tract of the human body. It can be envisaged that in the future more than one capsule could be ingested by the patient and they operate collaboratively in the gastrointestinal (GI) tract to perform certain diagnostic and therapeutic tasks. These mobile capsules and the coordinator node, which is attached to the abdomen of the patient, form a wireless network. The capsule devices are typically powered by batteries, therefore, energy efficient medium access control (MAC) protocols for multiple capsule networks are necessary. This article proposes a novel energy efficient MAC protocol for multiple capsule networks based on time division multiple access (TDMA). An asymmetric up/down link network architecture is introduced. A novel TDMA slot assignment scheme is proposed and simulation results using Qualnet show that the proposed MAC protocol achieves lower energy consumption than B-MAC and star topology TDMA.

PC‐MAC: pico cellular MAC protocol for motorway vehicular multimedia communication (extended version)

AbstractDue to the dynamic nature of vehicular networks, provisioning multimedia (triple play—video, voice and data) communications to motorway drivers with quality of service (QoS) is extremely challenging. To overcome the challenges in this scenario, substantial effort is required to analyse the characteristics of vehicular traffic profiles on motorways around a base station (BS). For this purpose, we first perform detailed analysis of real vehicular traffic data taken from inductive loops on a motorway, and then develop our own vehicular simulator to study real‐time vehicular traffic scenarios where a main BS is responsible for multimedia communication. To address the issue of maintaining QoS for different traffic classes in reservation‐based medium access control (MAC) protocols in high‐speed vehicles, a novel medium access control, PC‐MAC (pico cellular medium access control) protocol is introduced. The proposed PC‐MAC protocol is a combination of carrier sense multiple access (CSMA) and slotted time division multiple access (S‐TDMA) for multimedia communication with optimal utilization for a motorway environment. Finally, the access to the BS is managed by our proposed PC‐MAC protocol that we have integrated into the vehicular simulator. The results of this configuration have been compared with other protocols. Copyright © 2009 John Wiley & Sons, Ltd.

Self-Stabilizing Deterministic Time Division Multiple Access for Sensor Networks

An algorithm for time division multiple access (TDMA) is found to be applicable in converting existing distributed algorithms into a model that is consistent with sensor networks. Such a TDMA service needs to be self-stabilizing so that in the event of corruption of assigned slots and clock drift, it recovers to states from where TDMA slots are consistent. Previous self-stabilizing solutions for TDMA are either randomized or assume that the topology is known upfront and cannot change. Thus, the question of feasibility of self-stabilizing deterministic TDMA algorithm where the topology is unknown remains open. In this paper, we present a self-stabilizing deterministic algorithm for TDMA in networks where a sensor is only aware of its neighbors. To our knowledge, this is the first such algorithm that achieves these properties. Moreover, this is the first algorithm that demonstrates the feasibility of stabilization-preserving deterministic transformation of a program in shared-memory model on an arbitrary topology into a program that is consistent with the sensor network model.

A Five-Phase Reservation Protocol (FPRP) for Mobile Ad Hoc Networks

A new single channel, time division multiple access (TDMA)-based broadcast scheduling protocol, termed the Five-Phase Reservation Protocol (FPRP), is presented for mobile ad hoc networks. The protocol jointly and simultaneously performs the tasks of channel access and node broadcast scheduling. The protocol allows nodes to make reservations within TDMA broadcast schedules. It employs a contention-based mechanism with which nodes compete with each other to acquire TDMA slots. The FPRP is free of the "hidden terminal" problem, and is designed such that reservations can be made quickly and efficiently with negligible probability of conflict. It is fully-distributed and parallel (a reservation is made through a localized conversation between nodes in a 2-hop neighborhood), and is thus scalable. A "multihop ALOHA" policy is developed to support the FPRP. This policy uses a multihop, pseudo-Bayesian algorithm to calculate contention probabilities and enable faster convergence of the reservation procedure. The performance of the protocol, measured in terms of scheduling quality, scheduling overhead and robustness in the presence of nodal mobility, has been studied via simulations. The results showed that the protocol works very well in all three aspects. Some future work and applications are also discussed.

TDMA-based adaptive modulation with dynamic channel assignment for high-capacity communication systems

This paper proposes a time-division multiple-access (TDMA)-based adaptive modulation scheme with dynamic channel assignment (AMDCA) to achieve high-capacity communication systems under dynamically changing propagation path and traffic conditions. The proposed method measures the received carrier-to-noise plus interference power ratio (C/(N+I)) of each TDMA slot to search available slots as well as to find out the optimum modulation parameters for each terminal, thereby effectively combining the effect of mitigating both spatially distributed electric field strength variation by the slow adaptive modulation and spatially and temporally distributed traffic variation by the dynamic channel assignment (DCA). Computer simulation confirms that the proposed AMDCA system can achieve approximately three times higher system capacity than the conventional fixed channel assignment (FCA) using QPSK.

Adaptive modulation with dynamic channel assignment (AMDCA) for TDMA microcellular systems

This paper aims at the realization of a large-capacity mobile communication system in the microcellular environment and proposes adaptive modulation with dynamic channel assignment (AMDCA) where the idea of dynamic channel assignment (DCA) is introduced into the slow adaptive modulation system. In the proposed system, the received average signal power-to-noise/interference power ratio [C/(N + I)] is measured for each TDMA (time division multiple access) slot. The choice of idle slots in DCA and the choice of applicable modulation parameters for the slots are made in parallel. Thus, wireless frequency resource assignment and the setting of the modulation parameters take place at the same time. This reduces the effect of the space–time distribution of the traffic in DCA and also reduces the effect of the spatial distribution of the received power in the slow adaptive modulation system on the geographical difference of the blocking probability of the users. The performance of the proposed method is evaluated by a computer simulation, and it is verified that a capacity approximately 3 times larger can be realized compared with conventional fixed-channel assignment in fixed QPSK in the case of voice transmission. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 82(1): 55–64, 1999