Hopping Networks Research Articles

Machine-Learning-Based Classification of Frequency Hopping in Radio Networks for Communication Reconnaissance

Abstract This article presents a customized approach for training a supervised learning neural network with the adaptive moment estimation algorithm, to classify the number of frequency hopping networks in an operational area. The algorithm was constructed based on data experimentally collected from a real-time spectrum analyzer for military very high frequency hopping networks. The impact of some training parameters on classification efficiency is briefly discussed while the obtained accuracy was above 97% for both test and validation data in all training variations. With this promising result, the proposed algorithm has the potential to be utilized in developing operational systems capable of real-time signal reconnaissance for military frequency hopping radio networks.

DCS: Dilution-based Convergecast Scheduling in a TSCH network

We describe Dilution-based Convergecast Scheduling (DCS), an algorithm to compute a convergecast tree and a corresponding schedule to Timeslotted Channel Hopping (TSCH) networks. DCS works by dividing the plane into a grid and computing local trees inside each grid box. DCS uses the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) to assign specific labels to nodes (called ranks) and to connect the local trees into a single convergecast tree spanning the whole network. DCS creates schedules that are collision-free. Additionally, differently from existing related approaches, apart from the use of RPL, DCS is itself a collision-free algorithm, i.e., the convergecast tree and the schedules are computed without collision during message transmissions. DCS adapts and implements over contiki-ng and the Cooja simulator a previous scheduling algorithm designed for the Signal-to-Interference-plus-Noise Ratio (SINR) model. contiki-ng is an operating system for embedded devices that offers a reference implementation of TSCH. In this paper we describe how DCS builds and structures TSCH schedules over a real communication stack. In particular, beyond being collision-free, DCS can generate short schedules when compared to the number of nodes in the network. In DCS schedule sizes do not depend directly on the number of nodes. We present simulation results where DCS outperforms related approaches in terms of slotframe sizes, packet delivery ratio and end-to-end delays.

Contention-Based Proportional Fairness (CBPF) Transmission Scheme for Time Slotted Channel Hopping Networks

Time slotted channel hopping (TSCH) is a mediumaccess control (MAC) protocol introduced in IEEE802.15.4e standard, addressing low-power requirements of the Internet of Things and low-power and lossy networks. The 6TiSCH operation (6top) sublayer of IEEE802.15.4e defines the schedule that includes sleep, transmit, and receive routines of the nodes. However, the standard does not specify the design of the schedule. In this article, we propose a contention-based proportional fairness transmission scheme for TSCH networks to maximize the system throughput addressing the fair allocation of resources to the nodes. We propose a convex programming-based method to achieve the fairness and throughput objectives. We model TSCH MAC as a multichannel slotted ALOHA and analyze it for a schedule given by the 6top layer. Performance metrics, such as throughput, delay, and energy spent per successful transmission, are derived and validated through simulations and real-time testbed implementations.

Network Delay and Cache Overflow: A Parameter Estimation Method for Time Window Based Hopping Network.

A basic understanding of delayed packet loss is key to successfully applying it to multi-node hopping networks. Given the problem of delayed data loss due to network delay in a hop network environment, we review early time windowing approaches, for which most contributions focus on end-to-end hopping networks. However, they do not apply to the general hopping network environment, where data transmission from the sending host to the receiving host usually requires forwarding at multiple intermediate nodes due to network latency and network cache overflow, which may result in delayed packet loss. To overcome this challenge, we propose a delay time window and a method for estimating the delay time window. By examining the network delays of different data tasks, we obtain network delay estimates for these data tasks, use them as estimates of the delay time window, and validate the estimated results to verify that the results satisfy the delay distribution law. In addition, simulation tests and a discussion of the results were conducted to demonstrate how to maximize the reception of delay groupings. The analysis shows that the method is more general and applicable to multi-node hopping networks than existing time windowing methods.

Resource Allocation in Time Slotted Channel Hopping (TSCH) Networks Based on Phasic Policy Gradient Reinforcement Learning

The concept of the Industrial Internet of Things (IIoT) is gaining prominence due to its low-cost solutions and improved productivity of manufacturing processes. To address the ultra-high reliability and ultra-low power communication requirements of IIoT networks, Time Slotted Channel Hopping (TSCH) behavioral mode has been introduced in IEEE 802.15.4e standard. Scheduling the packet transmissions in IIoT networks is a difficult task owing to the limited resources and dynamic topology. In IEEE 802.15.4e TSCH, the design of the schedule is open to implementation. In this paper, we propose a phasic policy gradient (PPG) based TSCH schedule learning algorithm. We construct the utility function that accounts for the throughput, and energy efficiency of the TSCH network. The proposed PPG based scheduling algorithm overcomes the drawbacks of totally distributed and totally centralized deep reinforcement learning-based scheduling algorithms by employing the actor–critic policy gradient method that learns the scheduling algorithm in two phases, namely policy phase and auxiliary phase. In this method, we show that the schedule converges quickly compared to any other actor–critic method and also improves the system throughput performance by 58% compared to the minimal scheduling function, a default TSCH schedule.

Parent and PHY Selection in Slot Bonding IEEE 802.15.4e TSCH Networks.

While IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) networks should be equipped to deal with the hard wireless challenges of industrial environments, the sensor networks are often still limited by the characteristics of the used physical (PHY) layer. Therefore, the TSCH community has recently started shifting research efforts to the support of multiple PHY layers, to overcome this limitation. On the one hand, integrating such multi-PHY support implies dealing with the PHY characteristics to fit the resource allocation in the TSCH schedule, and on the other hand, defining policies on how to select the appropriate PHY for each network link. As such, first a heuristic is proposed that is a step towards a distributed PHY and parent selection mechanism for slot bonding multi-PHY TSCH sensor networks. Additionally, a proposal on how this heuristic can be implemented in the IPv6 over the TSCH mode of IEEE 802.15.4e (6TiSCH) protocol stack and its Routing Protocol for Low-power and Lossy network (RPL) layer is also presented. Slot bonding allows the creation of different-sized bonded slots with a duration adapted to the data rate of each chosen PHY. Afterwards, a TSCH slot bonding implementation is proposed in the latest version of the Contiki-NG Industrial Internet of Things (IIoT) operating system. Subsequently, via extensive simulation results, and by deploying the slot bonding implementation on a real sensor node testbed, it is shown that the computationally efficient parent and PHY selection mechanism approximates the packet delivery ratio (PDR) results of a near-optimal, but computationally complex, centralized scheduler.

Slot Bonding for Adaptive Modulations in IEEE 802.15.4e TSCH Networks

The numerous applications of industrial automation have always posed many challenges for wireless connectivity. In the last decade, IEEE 802.15.4e time-slotted channel hopping (TSCH) networks have provided high reliability and low-power operation in such challenging industrial environments. Typically, TSCH networks employ one modulation at the physical layer and are thus limited by the characteristics of the chosen modulation in terms of, among others, data rate, reliability and energy efficiency. To tackle these limitations and to improve network performance and flexibility in those challenging industrial environments, this work explores the simultaneous use of multiple modulations in a TSCH network. Traditionally, TSCH relies on fixed-duration slots, large enough to send a packet of any size given the fixed data rate. In order to avoid wasting airtime when simultaneously using modulations with different data rates, we propose the concept of slot bonding. This allows the creation of different-sized bonded slots with a duration adapted to the data rate of each chosen modulation. To analyze the proposed slot bonding technique, we formally describe the TSCH slot bonding problem in terms of optimizing the packet delivery ratio while minimizing radio on time, with the inclusion of parent selection and interference avoidance. Afterward, we propose a genetic algorithm that allows us to implement the problem and find solutions heuristically. Finally, we provide insights into preferred parent selection and modulation configurations by using this heuristic approach during extensive simulation experimentation in which the scalability advantage of slot bonding over longer fixed-duration slots is also shown.

Low-delay fair-reliability scheduling in multi-hop IEEE802.15.4e time synchronised channel hopping networks

Low-delay fair-reliability scheduling in multi-hop IEEE802.15.4e time synchronised channel hopping networks

Low-delay fair-reliability scheduling in multi-hop IEEE802.15.4e time synchronised channel hopping networks

IEEE802.15.4e is the latest generation of high-reliability, low-power medium access control protocols. As part of IEEE802.15.4e, time synchronised channel hopping (TSCH) provides support for multi-...

TLSA: A Two Level Scheduling Algorithm for Multiple packets Arrival in TSCH Networks

Wireless communication has become the promising technology in the recent times because of its applications in Internet of Things( IoT) devices. The IEEE 802.15.4e has become the key technology for IoT devices which utilizes the Time-Slotted Channel Hopping (TSCH) networks for the communication between the devices. In this paper, we develop a Two Level Scheduling Algorithm (TLSA) for scheduling multiple packets with different arrival rate at the source nodes in a TSCH networks based on the link activated by a centralized scheduler. TLSA is developed by considering three types of links in a network such as link i with packets arrival type 1, link j with packets arrival type 2, link k with packets arrival type 3. For the data packets arrival, two stages in a network is considered. At the first stage, the packets are considered to be of higher priority. At the second stage, the packets are considered to be of lower priority. We introduce level 1 schedule for the packets at stage 1 and level 2 schedule for the packets at stage 2 respectively. Finally, the TLSA is validated with the two different energy functions i.e., y=eax -1 and y=0.5x2 using MATLAB 2017a software for the computation of average and worst ratios of the two levels.

A Scheduling Method Based on Packet Combination to Improve End-to-End Delay in TSCH Networks with Constrained Latency

Wireless sensor networks (WSN) are networks for gathering data from sensor nodes that have been applied in industry for a long time. In real-time industrial applications with tight latencies, schedulability is one of the most critical issues. Some authors have proposed centralized scheduling algorithms for time-slotted channel hopping (TSCH) networks for real-time applications in industry, however, they have some disadvantages such as schedulability and high data traffic. In this paper, we improve the schedulability, latency, data traffic by dynamically prioritizing packets which are based on number duplex-conflicts and dynamically combining the packets. As a result, we show that the packet-combining algorithm improves schedulability and minimizes the amount of traffic in a network when compared with existing approaches.

6TiSCH minimal scheduling function: Performance evaluation

6TiSCH is a standardization group within the Internet Engineering Task Force (IETF) that works on IPv6‐enabled Time‐slotted Channel Hopping (TSCH) networks. The 6TiSCH protocol stack, designed by the standardization work at the IETF, has direct applicability to low‐power Internet of Things (IoT) use cases, including smart factory, building, infrastructure and home applications. A key component of the 6TiSCH stack is the Minimal Scheduling Function (MSF). MSF implements a traffic adaptation algorithm which allocates link‐layer resources, that is, cells in the TSCH schedule, according to the traffic load. MAX_NUMCELL is an important parameter defined in the MSF draft standard which determines the length of the running window used to measure cell usage. MSF draft standard does not recommend a value of MAX_NUMCELL to use. This paper provides recommendations on how to choose the value of MAX_NUMCELL, validated through simulation. For periodic traffic, setting MAX_NUMCELL to at least four times the traffic load is recommended to increase efficiency. For bursty traffic, we show that setting MAX_NUMCELL to a small value achieves a low end‐to‐end latency but at high communication overhead. In addition, an improved version of MSF is implemented and tested, which shows a 44% reduction in the communication overhead, considering MAX_NUMCELL = 4, while maintaining the same end‐to‐end latency.

A performance analysis of Orchestra scheduling for time‐slotted channel hopping networks

The IEEE 802.15.4 TSCH (Time Slotted Channel Hopping) represents the latest generation of low‐power and highly reliable medium‐access control (MAC) protocols. It orchestrates the medium access according to a time‐frequency communication schedule. However, TSCH specification does not provide any practical solution for the establishment of the schedule. Orchestra is a recent scheduling solution for TSCH that brings significant advantages such as, the use of simple scheduling rules, the low signaling overhead, and the high delivery ratio it is able to fulfill. In this paper, we investigate the use of TSCH protocol with Orchestra scheduling approach for the Internet of Things (IoT) applications. Performance analysis results demonstrate that despite its unique features, Orchestra may incur high end‐to‐end communication delay, especially when the traffic is not uniformly distributed in the network. This limitation makes Orchestra not sufficiently convenient for several delay‐sensitive IoT applications, such as smart grid applications.

Basin Hopping Networks of continuous global optimization problems

Characterization of optimization problems with respect to their solvability is one of the focal points of many research projects in the field of global optimization. Our study contributes to these efforts with the usage of the computational and mathematical tools of network science. Given an optimization problem, a network formed by all the minima found by an optimization method can be constructed. In this paper we use the Basin Hopping method on well-known benchmarking problems and investigate the resulting networks using several measures.

A rapid joining scheme based on fuzzy logic for highly dynamic IEEE 802.15.4e time-slotted channel hopping networks

The IEEE 802.15.4e standard is an amendment of the IEEE 802.15.4-2011 protocol by introducing time-slotted channel hopping access behavior mode. However, the IEEE 802.15.4e only defines time-slotted channel hopping link-layer mechanisms without an investigation of network formation and communication scheduling which are still open issues to the research community. This article investigates the network formation issue of the IEEE 802.15.4e time-slotted channel hopping networks. In time-slotted channel hopping networks, a joining node normally takes a long time period to join the network because the node has to wait until there is at least one enhanced beacon message advertised by synchronized nodes (synchronizers) in the network on its own synchronization channel. This leads to a long joining delay and high energy consumption during the network formation phase, especially so in highly dynamic networks in which nodes join or rejoin frequently. To enable a rapid time-slotted channel hopping network formation, this article proposes a new design for slotframe structure and a novel adaptive joining scheme based on fuzzy logic. Our proposed scheme enables a synchronizer to be able to adaptively determine an appropriate number of enhanced beacons it should advertise, based on the number of available synchronizers in the network, so that joining nodes can achieve a short joining time while energy consumption of enhanced beacon advertisement at the synchronizers is optimized. Through extensive mathematical analysis and experimental results, we show that the proposed scheme achieves a significant improvement in terms of joining delay compared to state-of-the-art studies.

Link‐layer security in TSCH networks: effect on slot duration

AbstractThe IEEE802.15.4e‐2012 standard is widely used in multi‐hop wireless industrial Internet of things applications. In the time‐slotted channel hopping mode, nodes are synchronised, and time is cut into timeslots. A schedule orchestrates all communications, resulting in high reliability and low power operations. A timeslot must be long enough for a node to send a data frame to its neighbour, and for that neighbour to send back an acknowledgement. Shorter timeslots enable higher bandwidth and lower latency, yet the minimal timeslot duration is limited by how long link‐layer security operations take. We evaluate the overhead of link‐layer security in time‐slotted channel hopping networks in terms of minimal timeslot length, memory footprint and energy consumption. We implement full link‐layer security on a range of hardware platforms, exploring different hardware/software implementation strategies. Through an extensive measurement campaign, we quantify the advantage of hardware accelerations for link‐layer security and show how the minimal duration of a timeslot varies between 9 and 88ms for the most common configuration, depending on hardware support. Furthermore, we also highlighted the impact that the timeslot duration has on both high‐level application design and energy consumption. Copyright © 2016 John Wiley & Sons, Ltd.

Distributed PID-Based Scheduling for 6TiSCH Networks

Industrial low-power networks are becoming the nexus of operational technologies and the Internet thanks to the standardization of networking layer interfaces. One of the main promoters of this shift is the IETF 6TiSCH WG, which addresses network management and IP integration of time synchronized channel hopping (TSCH) networks as those developed by the IEEE802.15.4 TG. The 6TiSCH WG is defining the operational interface and mechanism by which the network schedule can be distributed amongst the devices in the network. This operational sublayer, called 6top, supports distributed scheduling and enables implementers to define the scheduling policy, only standardizing the distribution mechanism. This letter proposes a novel distributed scheduling policy based on the well-known industrial control paradigm referred as proportional, integral, and derivative (PID) control. The proposed technique is completely decentralized, enabling each node to determine the number of cells to schedule to one another, according to its traffic demand. The mechanism is reactive to sudden or bursty traffic patterns, while staying conservative in over-provisioning cells.

Column generation for frequency assignment in slow frequency hopping networks

This article deals with the frequency assignment problem (FAP) in slow frequency hopping (GSM) networks, a generalization of the classical FAP. Due to symmetry in the solutions, a natural integer linear programming formulation does not yield a good solution procedure. Instead, we decompose the co-channel and adjacent channel interference minimization and develop a two-stage algorithm. The co-channel optimization problem is solved with a column generation model, whereas the second stage is solved by a cutting plane approach. Computational experiments reveal, that although no optimal solutions can be guaranteed, the approach provides promising results, both regarding practical applicability and further research potential.

Correlation factors for interstitial-mediated self-diffusion in the diamond lattice: Kinetic lattice Monte Carlo approach

We have performed extensive analysis of the correlation factors for interstitial-mediated self-diffusion via various possible mechanisms and hopping networks in the diamond lattice using the kinetic lattice Monte Carlo approach. The correlation factor for the kick-out mechanism in the tetrahedral hopping network is calculated to be 0.73, in agreement with previous results; and the value for the hexagonal hopping network is 0.47 for the dominant mechanism. For the mechanism where a split interstitial is stable (``stable-split'' mechanism), the correlation factor for the tetrahedral network stays the same while that for the hexagonal network increases to 0.62. We then performed simulations for the diffusion process of silicon involving multiple mechanisms. The choice of mechanisms is justified by ab initio calculations. We conclude that unlike vacancy diffusion, interstitial self-diffusion has a temperature-dependent correlation factor. This conclusion holds in general for diffusion processes involving multiple mechanisms with different activation energies. The correlation factor obtained from ab initio results for interstitial-mediated self-diffusion in silicon at 1000--1100 \ifmmode^\circ\else\textdegree\fi{}C is 0.64--0.80, compared to the value of 0.6 extracted from the experiment.

Assignment of Frequency Lists in Frequency Hopping Networks

Metaheuristic algorithms for frequency assignment problems have received considerable attention in the literature, but few papers have addressed the question of list assignment in frequency hopping networks. The work of Bjo/spl uml/rklund, Va/spl uml/rbrand, and Yuan is a notable exception, which will be extended here in a number of directions. The current paper sets out to determine the relative merits of pregeneration of the lists before assignment and allowing the assignment algorithm to modify the lists as it proceeds. The relative merits of synchronization within individual cells and synchronization at a single site are considered. Some other options, such as splitting the spectrum into a part for control carriers and a part for traffic carriers, are also evaluated. The COST 259 benchmarks for frequency assignment are modified to create some benchmarks for frequency hopping problems. This will allow other authors to compare the results of new metaheuristic algorithms with the effective but relatively straightforward simulated annealing (SA) algorithm used here.