Time Division Multiple Access Scheduling Research Articles

Joint optimization for energy efficient full-duplex UAV relaying with multiple user pairs

This paper investigates an unmanned aerial vehicle (UAV) assisted amplify-and-forward relaying, where a full-duplex (FD) fixed-wing UAV employs a time-division multiple access scheduling protocol to provide relay services for multiple source–destination user pairs. With the aim of maximizing energy efficiency (EE) of the system, a joint optimization problem is studied so as to jointly fulfill the communication scheduling of multiple user pairs, the transmit power control and the trajectory design of the UAV. Since the optimization variables of the problem are coupled, it is non-convex and hence hard to solve directly. To this end, the initial problem is decomposed into three subproblems corresponding to the optimization of communication scheduling, and transmit power and trajectory of the UAV, respectively. The three subproblems are solved by utilizing the linear programming, the successive convex approximation (SCA), and the Dinkelbach’s algorithm. Then an iterative algorithm based on the block coordinate descent technique is proposed to tackle the joint optimization problem by optimizing the three blocks of variables alternately. Simulation results demonstrate that the proposed algorithm converges efficiently, and the EE of the joint optimization scheme can be significantly improved compared to the benchmark schemes.

ACOMAR: ACO‐based MAC‐aware routing protocol

SummaryIn this work, we present a new nature‐inspired cross‐layer routing protocol named ACO‐based MAC‐aware routing protocol (ACOMAR). An enhancement of time division multiple access (TDMA) algorithm is proposed where slots allocation algorithm considers the geographical distance between nodes and the sink. The nodes that are far away from the sink have better chance to be scheduled first. This strategy will result in more efficiency than a usual random TDMA schedule. This algorithm uses a metric based on the pheromone's value of Ant Colony Optimization (ACO) to choose the best next hop with the aim of reducing latency and energy and extending the network lifetime. Comparisons are made between ACOMAR, MAC‐aware routing (MAR) and the latest cross‐layer protocol latency and energy MAC‐aware routing (LEMAR). The experimental results show that ACOMAR outperforms considerably LEMAR by 80%, 20%, 81%, and 54% in latency, energy, hop count, and throughput, respectively. Consequently, ACOMAR is a suitable solution for healthcare applications where WSN‐based critical IoT devices interact quickly in emergence cases (high rate in latency optimization 80%).

Distributed TDMA for Mobile UWB Network Localization

Many applications related to the Internet of Things, such as tracking people or objects, robotics, and monitoring require the localization of large networks of devices in dynamic, GPS-denied environments. Ultrawideband (UWB) technology is a common choice because of its precise ranging capability. However, allowing access and effective use of the shared UWB medium with a constantly changing set of devices faces some particular challenges: high frequency of ranging measurements by the devices to improve system accuracy; network topology changes requiring rapid adaptation; and decentralized operation to avoid single points of failure. In this article, we propose a novel time-division multiple access (TDMA) algorithm that can quickly schedule the use of the UWB medium by a large network of devices without collisions in local network neighborhoods and avoiding conflicts with hidden terminals, all the while maximizing network usage. Using exclusively the UWB radio network, we realize a decentralized system for synchronization, dynamic TDMA scheduling, and precise relative positioning on a multihop network. Our system does not have special nodes (all nodes are equal) and it is sufficiently scalable for real-world applications. Our method can be applied to implement device localization services in large spaces without GPS and complex topologies, such as malls, museums, mines, etc. We demonstrate our method in simulation and on real hardware in an underground parking lot, showing the effectiveness of its TDMA schedule for relative localization.

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 Modified Particle Swarm Optimization Approach for Latency of Wireless Sensor Networks

In time-sensitive applications, such as detecting environmental and individual nuclear radiation exposure, wireless sensor networks are employed.. Such application requires timely detection of radiation levels so that appropriate emergency measures are applied to protect people and the environment from radiation hazards. In these networks, collision and interference in communication between sensor nodes cause more end-to-end delay and reduce the network's performance. A time-division multiple-access (TDMA) media access control protocol guarantees minimum latency and low power consumption. It also overcomes the problem of interference. TDMA scheduling problem determines the minimum length conflict-free assignment of slots in a TDMA frame where each node or link is activated at least once. This paper proposes a meta-heuristic centralized contention-free approach based on TDMA, a modified particle swarm optimization. This approach realizes the TDMA scheduling more efficiently compared with other existing algorithms. Extensive simulations were performed to evaluate the modified approach. The simulation results prove that the proposed scheduling algorithm has a better performance in wireless sensor networks than the interference degree leaves order algorithm and interference degree remaining leaves order algorithm. The results demonstrate also that integrating the proposed algorithm in TDMA protocols significantly optimizes the communication latency reduction and increases the network reliability.

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 Dynamic TDMA Scheduling Strategy for MANETs Based on Service Priority.

Physical resource allocation strategy is a key factor affecting the performance of a mobile ad hoc network (MANET), which serves as a network model widely used in the sensor and detection field. For various perceived service information, it is significant for the allocation strategy to adapt to the dynamic service requirements and prioritize resource access for the service information with high priority to guarantee its real-time performance. In this paper, a novel dynamic time division multiple access (TDMA) scheduling strategy is proposed for MANETs. Firstly, a service priority-based dynamic TDMA scheduling (SP-DS) algorithm is presented, which introduces the service priority as a reference factor for slot allocation and fully considers the transmission throughput and end-to-end delay performance. Moreover, for improving the slot use of the whole system, a modified distributed color constraint heuristic (MD-CCH) scheme is presented to optimize the frame structure. The SP-DS and MD-CCH algorithms are combined to form the novel strategy. Simulation results have demonstrated that the proposed strategy has better performance in the slot use, slot allocation efficiency, end-to-end delay and transmission throughput compared with the existing slot allocation algorithms.

A survey on time division multiple access scheduling algorithms for industrial networks

In recent years, wireless networks have been widely adopted in industrial applications such as monitoring and control because of their flexibility and low cost. However, wireless networks use shared medium which require appropriate Media Access Control (MAC) protocols to manage the shared medium. Time Division Multiple Access (TDMA)-based MAC protocols, which are collision free are predominantly used in industrial networks. To achieve the stringent requirements of reliability and timeliness in industrial applications, proper scheduling of the nodes accessing the shared channel is essential. A number of TDMA scheduling algorithms have been proposed in the literature but there is no study that have analyzed and compared the algorithms to help designers of new algorithms with basic information of the existing algorithms. The objective of this study is to provide basic findings that should be used by researchers looking for TDMA scheduling algorithms for industrial applications. To achieve the objectives of this article various categories of the TDMA scheduling algorithms that have been implemented in various industrial networks mostly Industrial Wireless Sensor Network (IWSN) which is widely deployed have been presented. Comparison of the various categories of the scheduling algorithms using reliability and delay as performance metrics which are crucial in industrial applications have been done. It was noted that hybrid TDMA scheduling algorithms have improved performance compared to distributed and centralized algorithms in random networks. Designing and testing of hybrid TDMA scheduling algorithms in the emerging industrial wireless networks such as LoRaWAN are recommended future work.

Finite Blocklength Analysis of Multiple Access Channels With/Without Cooperation

Motivated by the demand of reliable and finite blocklength communications, we employ tools from information theory, stochastic processes and queueing theory, in order to provide a comprehensive framework regarding the analysis of a Time Division Multiple Access (TDMA) network with bursty traffic, in the finite blocklength regime. Specifically, we reexamine the stability conditions of a non-cooperative TDMA multiple access channel, evaluate the optimal throughput, and identify the optimal data packet size, k, for fixed codeword of blocklength, n. The evaluation is performed both numerically and via the proposed approximations, which result in closed form expressions and provide insight on how the optimal data size, k*, relates to the information metrics of channel capacity and channel dispersion in the finite blocklength regime. Then, we examine the stability conditions and the performance of the Multiple Access Relay Channel with TDMA scheduling, subject to finite blocklength constraints, by applying a cognitive cooperation protocol that assumes relaying is enabled when sources are idle. Finally, we propose the novel Batch-And-Forward (BAF) strategy, a mechanism that allows terminals to send batches of data packets instead on individual data packets, and evaluate the stability conditions and the optimal throughput. Numerical evaluation of the proposed strategy indicates that the performance of the cooperative network in the finite blocklength regime, in terms of throughput, can be significantly enhanced. Moreover, it reduces the requirement in control signals (metadata) [3], since, it avoids the unnecessary repetition of metadata (e.g. address of the source terminal and the destination). The BAF strategy is quite versatile, thus, it can be embedded in existing cooperative protocols, without imposing additional complexity on the overall scheme.

Minimum Age of Information TDMA Scheduling: Approximation Algorithms and Hardness Results

We consider a transmission scheduling problem in which multiple agents receive update information through a shared Time Division Multiple Access (TDMA) channel. To provide timely delivery of update information, the problem asks for a schedule that minimizes the overall Age of Information (AoI). We call this problem the Min-AoI problem. Several special cases of the problem are known to be solvable in polynomial time. Our contribution is threefold. First, we introduce a new job scheduling problem called the Min-WCS problem, and we prove that, for any constant r ≥ 1, every r-approximation algorithm for the Min-WCS problem can be transformed into an r-approximation algorithm for the Min-AoI problem. Second, we give a randomized 2.619-approximation algorithm, a randomized 3-approximation algorithm, which outperforms the previous one in certain scenarios, and a dynamic-programming-based exact algorithm for the Min-WCS problem. Finally, we prove that the Min-AoI problem is NP-hard.

Slot‐hitting ratio‐based TDMA schedule for hybrid energy‐harvesting wireless sensor networks

In the energy-harvesting wireless sensor networks (EH-WSNs) with Time division multiple access (TDMA), it is challenging to assign time slots to the nodes because energy shortage causes some nodes unable to transmit in their time slots, resulting in the inefficiency in slot usage and the increase of the data packet delay. To overcome this problem, the slot assignment in TDMA is required to consider energy packet arrivals, where an energy packet is defined as the amount of energy that suffices for one transmission. In this study, the authors investigate the EH-WSN with hybrid energy sources, in which the nodes harvest energy from the fixed inter-arrival time (FIAT) and the random inter-arrival time (RIAT) energy sources. After deriving the slot-hitting ratios (SHRs) of energy packet arrivals for both FIAT and RIAT energy sources, they propose the SHR-based TDMA (SHR-TDMA) scheme. Then, they derive the delay arising from the awaiting slot (DAFAS) and formulate the DAFAS minimisation problem for the SHR-TDMA. Solution to the DAFAS minimisation problem makes the slots optimally assigned according to the characteristics of the energy packet arrivals at the nodes. The simulation results show that the SHR-TDMA outperforms the existing TDMA schemes in terms of DAFAS.

Optimizing TDMA Schedule and SIC-Capable UAV Position via Gibbs Sampling

This letter considers a novel problem that aims to derive the shortest possible Time Division Multiple Access (TDMA) schedule for use by ground nodes to upload their data to an Unmanned Aerial Vehicle (UAV) over random channel gains. Its key novelties include equipping the UAV with a Successive Interference Cancellation (SIC) radio and applying a Gibbs sampling based approach to optimize the UAV’s position. Our results show that the UAV is able to learn the optimal location whereby the average schedule length at the optimal position is up to 17% shorter as compared to other locations.

Multi-criteria-Based Mobile Hotspot Selection in IoT-Based Highly Dense Network

One of the major challenges in Wireless Sensor Networks-based internet of things networks is to conserve energy and extend network lifetime. In order to provide green computing, energy-saving is necessary for both unchangeable limited battery sensors and energy outsourced devices such as smartphones. In this research work, a scenario is considered, in which sensors are deployed in an area where smart devices (mobile elements) are present in abundance. Only Mobile Elements can take the role of cluster head (CH). Mobile element is selected as CH based on the weighted average of multiple attributes. Then the cluster heads send data to the cloud network. Cluster members select their CH in a distributed manner and send an acknowledgment message to the respective CH. CH updates its member list and prepares a time division multiple access (TDMA) schedule. On the basis of this TDMA schedule, CH transmits the data of energy critical nodes first. As mobile elements are motile, therefore, proposed work manages mobility to avoid packet loss and end-to-end delay. Simulation and results prove that proposed energy-efficient multi-criteria-based clustering improves network lifetime, average throughput, and minimizes end-to-end delay and communication cost.

Median Access Control Protocols for Sensor Data Collection: A Review

Median Access Control (MAC) protocols are designed to mitigate collisions and enhance the energy efficiency for sensor data collection. This paper reviews two basic categories of MAC protocols. The first class is the contention-based protocols, where nodes randomly compete for channel access. The second class is the schedule-based MAC protocols, in which nodes access the channel on the basis of the predetermined schedules. We focus on discussing the Time Division Multiple Access (TDMA) protocols and classify different TDMA schedulings into three categories according to the communication patterns in the network, i.e., the link scheduling, aggregate scheduling and non-aggregate scheduling. Link scheduling deals with the peer to peer communication pattern, where there is no central node in the network. In comparison, both the aggregate and non-aggregate schedulings handle the convergecast communication pattern, in which all traffic are destined to the sink. This survey provides a comprehensive overview of these three categories and provided a detailed briefing on how the TDMA schedules handle the network traffic dynamics in the network. Compared with other surveys in this domain, this review does not confine itself to deal with collecting a particular form of data, but provides a unified framework to integrate the data semantics in a broader sense into the design of TDMA scheduling algorithms.

A Wireless Geophone Network Architecture Using IEEE 802.11af With Power Saving Schemes

Seismic surveys are conducted by oil exploration companies to keep up with the global demand for oil and gas. Although seismic cables offer fast and reliable data transfer, they account for a majority of the equipment weight, logistics, and labor costs. A novel wireless geophone network architecture, compliant with the IEEE 802.11af standard, is described. Operation in television white spaces can achieve long transmission ranges, allowing for scalable coverage of large seismic survey areas. Two methods for data collection are proposed: a Geophone-Polling (GP) scheme and an Adaptive Geophone Time Division Multiple Access Scheduling (AGTS) scheme. The two schemes are analyzed and evaluated in terms of the total time taken for data acquisition and the average power consumption, in comparison to the default IEEE 802.11 channel access schemes. The problem of hexagonal clustering for orthogonal deployment of geophones is also tackled, and the impact of co-channel interference is considered. The proposed schemes not only reduce data acquisition time, but also the average power consumption of the geophones, thereby improving the lifetime of wireless seismic surveys.

Effective TDMA scheduling for tree-based data collection using genetic algorithm in wireless sensor networks

Data collection is a major operation in Wireless Sensor Networks (WSNs) and minimizing the delay in transmitting the collected data is critical for a lot of applications where specific actions depend on the required deadline, such as event-based mission-critical applications. Scheduling algorithms such as Time Division Multiple Access (TDMA) are extensively used for data delivery with the aim of minimizing the time duration for transporting data to the sink. To minimize the average latency and the average normalized latency in TDMA, we propose a new efficient scheduling algorithm (ETDMA-GA) based on Genetic Algorithm(GA). ETDMA-GA minimizes the latency of communication where two dimensional encoding representations are designed to allocate slots and minimizes the total network latency using a proposed fitness function. The simulation results show that the performance of the proposed algorithm outperforms the existing state-of-the-art approaches such as Rand-LO, Depth-LO, DepthRe-LO, IDegRe-LO, and IDeg-LO in terms of average latency, average normalized latency, and average schedule length.

CSDGP: cluster switched data gathering protocol for mobile wireless sensor networks

Nowadays, most of the research focuses on the distributed algorithm to form the clusters in wireless sensor networks, in which the sensor nodes act autonomously to self-configure themselves with the help of the local information. However, the issues in such distributed mechanisms are (i) how to assign the time division multiple access (TDMA) schedule to collect the data from the cluster member (CM), (ii) how to distribute and balance the overall energy consumption of the cluster heads (CHs) under the circumstance of node's mobility. To overcome these problems, a cluster switched data gathering protocol (CSDGP) is proposed which ensures a uniform distribution of CHs by utilising a waiting time-based CH selection and an effective cluster switch based TDMA scheduling mechanism. The salient feature observed in the proposed CSDGP is that the migrated node has a chance to transmit the sensed data to the CH, whenever the CH has a free time slot. From the simulation results, it is proved that CSDGP provides a good performance under three different scenarios in comparison with existing protocols in terms of average energy consumption, average end-to-end delay, packet delivery ratio, and control overhead.

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.

An Energy-efficient Distributed TDMA Scheduling Algorithm for ZigBee-like Cluster-tree WSNs

The design of Medium Access Control (MAC) protocol for Wireless Sensor Networks (WSNs) with both limited energy consumption and data delivery time is crucial for industrial and control applications. Since Time Division Multiple Access (TDMA) MAC eliminates the collision occurrence and seeks the minimization of the number of time-slots assigned to each node, the energy consumption of the nodes is reduced. Furthermore, with the proper allocation of the time-slots to the nodes, the transmission delay can be significantly reduced. In this article, we propose TDMA scheduling algorithm for Cluster-tree topology WSNs that meets the timeliness and the energy demands. The algorithm adopts an elegant approach that expresses the timing constraints of the data transmissions as an integer multiple of the length of the schedule period. Moreover, since the distributed algorithm is well-suited to the scarce resources of the WSNs, we focus on the distributed methods that allow each cluster to come up with its allocated time-slots. The algorithm is based on graph theory, such as distributed shortest path, distributed topological ordering, and distributed graph coloring algorithms. The efficiency of the algorithm, regarding the elapsed time to construct the schedule and the energy consumption, is evaluated over benchmark instances up to several thousands of nodes.

TDMA in Adaptive Resonant Beam Charging for IoT Devices

Resonant beam charging (RBC) can realize wireless power transfer (WPT) from a transmitter to multiple receivers via resonant beams. The adaptive RBC (ARBC) can effectively improve its energy utilization. In order to support multi-user WPT in the ARBC system, we propose the time-division multiple access (TDMA) method and design the TDMA-based WPT scheduling algorithm. Our TDMA WPT method has the features of concurrently charging, continuous charging current, individual user power control, constant driving power and flexible driving power control. The simulation shows that the TDMA scheduling algorithm has high efficiency, as the total charging time is roughly half (46.9% when charging 50 receivers) of that of the alternative scheduling algorithm. Furthermore, the TDMA for WPT inspires the ideas of enhancing the ARBC system, such as flow control and quality of service (QoS).