Channel Hopping Mechanism Research Articles

ASAA: Multihop and Multiuser Channel Hopping Protocols for Cognitive-Radio-Enabled Internet of Things

The devices of Internet of Things (IoT) are integrated and interconnected by using the traditional wireless communication technology. Unavailability of spectrum sharing occurs in traditional wireless communication due to the presence of a massive number of IoT devices. Thus, Cognitive Radio Network (CRN) is introduced as a promising technology to utilize the spectrum efficiently. Channel Hopping Sequence (CHS) is used to establish communication among CRN users. However, the majority of CHS mechanisms only focus on multi-user single-hop scenarios, which can lead to bottleneck and throughput degradation problems. It is also found that few existing CHS mechanisms still have a low percentage of rendezvous that can cause difficulties for the Secondary Users (SUs) to communicate. Thus, it is a challenge to design efficient CHS for establishing fast communication among SUs under multi-user, multi-hop scenarios and asymmetric asynchronous environments. In this paper, Asymmetric Synchronous and Asymmetric Asynchronous (ASAA) Channel Hopping (CH) algorithms are designed for the multi-user CRN-enabled IoT devices to share the unused spectrum in the multi-hop scenario. The Multi-User Asymmetric Synchronous (MUAS) and Multi-User Asymmetric Asynchronous (MUAA) protocols are designed in the proposed ASAA channel hopping mechanism. The simulation results show that the proposed ASAA CHS algorithms outperform the existing CHS mechanisms in terms of throughput, Channel Loading (CL), Channel Utilization (CU), Maximum Time To Rendezvous (MTTR), Average Time to Rendezvous (ATTR) and Maximum Inter Rendezvous Interval (MIRI).

Time-slotted LoRa MAC with variable payload support

LoRaWAN is an upcoming Low Power Wide Area Network (LPWAN) technology for Internet of Things implementations in various application domains. Despite its various advantages, LoRaWAN employs an Aloha-based MAC, which in terms of performance cannot guarantee high packet delivery ratio and low latency. To overcome this issue, we propose a time-slotted scheme, called TS-VP-LoRa, which supports multiple transmission times and packet sizes at the same time. In TS-VP-LoRa, scheduling is coordinated by the LoRa gateway, broadcasting beacon frames periodically for the synchronization of LoRa end-devices. A channel hopping mechanism is also proposed in order to minimize the occurrence of collisions and to evenly split the transmission load among all channels. TS-VP-LoRa is evaluated and compared to three other MAC-layer schemes in single gateway simulation scenarios with up to 500 nodes. The proposed scheme has proven to achieve low latency with high packet delivery ratios, significantly minimize collisions and maintain a relatively low energy consumption despite the scaling of the LoRa network.

Setup-Independent Sensing Architecture With Multiple UHF RFID Sensor Tags

Ultra High Frequency Radio Frequency Identification (UHF RFID)-based sensing technology with antenna-integrated sensor tags offers a cost-effective solution for Internet of Things (IoT) applications. A multi-dimensional differential measurement technique for eliminating the effect of measurement setup, such as unknown mutual distance and orientation between the read/write device (RWD) and sensor tags, and line-of-sight obstruction, on acquiring information from multiple sensor tags simultaneously is proposed. The concept is based on 1) using a channel hopping mechanism to acquire multi-dimensional datasets and 2) conducting a dissimilarity analysis between offline and online datasets to extract sensor information. The differential measurement, which is activated by the channel hopping mechanism, mitigates the impact of the measurement setup, making the pattern of the multi-dimensional datasets tightly relate to the sensing state. A sensor tag for measuring the water filling level of polyvinyl chloride (PVC) pipes is designed and fabricated. Experiments show that the proposed method can accurately acquire information from three sensor tags simultaneously under different measurement setups. The performances using datasets of different dimensions are compared. Results reveal that using low-dimensional datasets can still be capable of getting accurate information from the sensor tags, implying that the acquisition time can be reduced.

Digital Twin Network for the IIoT using Eclipse Ditto and Hono

Digital twins are beginning to revolutionize many industries in the last decade, offering a plethora of benefits to optimize the performance of industrial systems. They aim to create a continuously synchronized model of the physical system that allows for rapid adaptation to dynamics, primarily to unpredicted and undesired changes. A vast range of industrial domains have already benefited from digital twin technology, such as aerospace, manufacturing, healthcare, city management and shipping. In addition, recent research is beginning to explore the integration of digital twins into computer networks to enable more innovation and intelligent management. One of the building blocks of digital twin technology is the Internet of Things, where wireless sensors and actuators are deployed to provide interaction between the physical and digital worlds. This type of network is complex to manage due to its strong constraints, especially when controlling critical industrial applications, which gave rise to the Industrial Internet of Things (IIoT). We believe that optimizing IIoT will lead to effective integration of digital twins in Industry 4.0. In this paper, we design a Digital Twin Network (DTN) for IIoT where sensors, actuators, and communication infrastructure are replicated in the digital twin to enable real-time intelligent management of these networks. By taking advantage of Eclipse Hono which allows an efficient connectivity for the network devices and Eclipse Ditto for representing the devices states in a digital form and also providing easy access to these states for the DTN. In this way, cognitive network services such as predictive maintenance, sustainability features, network diagnostics, security management, resource allocation, energy optimization can be efficiently integrated and operated in the network lifecycle. We validate the proposed architecture by providing a resource allocation case study where we explain how the Time Slotted Channel Hopping mechanism is exploited in our architecture.

Adaptive Channel Hopping for IEEE 802.15.4 TSCH-Based Networks: A Dynamic Bernoulli Bandit Approach

In IEEE 802.15.4 standard for low-power low-range wireless communications, only one channel is employed for transmission which can result in increased energy consumption, high network delay and poor packet delivery ratio (PDR). In the subsequent IEEE 802.15.4-2015 standard, a Time-slotted Channel Hopping (TSCH) mechanism has been developed which allows for a periodic yet fixed frequency hopping pattern over 16 different channels. Unfortunately, however, most of these channels are susceptible to high-power coexisting Wi-Fi signal interference and to possibly some other ISM-band transmissions. This interference manifests itself in the form of the presence/absence of other devices with either or both static and dynamic channel selection policies. In order to isolate channels with undesirable conditions, blacklisting mechanisms are defined to adapt the channel hopping process. However, the existing solutions which form blacklists unrealistically assume that the statistical model of the external interference remains fixed, and do not vary over time. In this paper, we realistically assume that the impact of external interferes on 802.15.4 may generally follow a non-stationary pattern, and accordingly formulate the adaptive channel hopping problem as a Dynamic Multi-Armed Bernoulli Bandit (Dynamic MABB) process from the machine learning theory. We then propose an online learning algorithm with track-ability properties for computing an adaptive hopping policy. Simulations confirm that when the statistics of the external interference has a switching regime, the proposed solution outperforms the previous schemes in terms of both energy efficiency as well as two important KPIs for TSCH-based networks, i.e., PDR and latency.

A Latin rectangles-based TSCH scheduling and interference mitigation design

The Industrial Internet of Things (IIoT) connects a large number of industrial objects to the Internet that requires a higher level of control in terms of reliability, low power, and delay. IEEE 802.15.4e is the standard of the IIoT and includes time-synchronized channel hopping mechanisms to allow multiple communications. It controls the medium access operations using a time–frequency schedule. However, TSCH (Time Slotted Channel Hopping) specification does not specify how to build an optimized schedule. In this paper, we propose a distributed channel hopping scheme by providing an analytical model for the exploitation of Latin rectangles to avoid interference and collisions. Indeed, Latin rectangles are used to perform the scheduling process, where rows present the channel offsets and columns for slot offsets. Thus, the frequency of communication is derived using Latin rectangles, which prevents the scheduling function of nodes from considering channels already allocated in their neighborhood. Consequently, interference and multi-path fading are mitigated with more reliability and robustness. Markov chain model for the queue on every node is introduced and takes the bulk arrivals and the slot distribution into account. We analyze the efficiency of this algorithm by analytical techniques and extensive simulations for three bulk arrivals: Poisson, Bernoulli, and Geometric.

An adjustable channel hopping algorithm for multi-radio cognitive radio networks

In cognitive radio networks, achieving rendezvous for two nodes (switching to the same channel at the same time) is a premise for them to communicate. Applying a channel hopping protocol is a common solution to achieve rendezvous. Most existing channel hopping protocols work in a single-radio environment and use available channels evenly without considering the time-varying channel conditions for different channels. Such channel hopping protocols may suffer from poor performance due to inefficient channel allocation. To efficiently solve the rendezvous problem, we propose the Adjustable Multi-radio Channel Hopping (AMCH) protocol in this paper. Instead of using available channels evenly, nodes running AMCH are able to adjust the usage ratio of each available channel. Simulation results verify that such a ratio adjustable channel hopping mechanism provides an efficient way to solve the rendezvous problem.

Interference Mitigation for Coexisting Wireless Body Area Networks: Distributed Learning Solutions

When multiple wireless body area networks (WBANs) exist in close proximity to each other, the inter-user interference considerably degrades the signal to interference plus noise ratio of the packets arriving at each WBAN coordinator. Also, the propagation paths within each WBAN experience fading due to the continuous changes in the body posture and mobility of the human body. The most preferred coexisting mechanisms specified in the IEEE 802.15.6 standard is the channel hopping mechanism, which fails to consider the varying radio environment and obtained reward in its channel selection. Thus, our paper investigates this channel selection problem for interference mitigation in a time-varying environment. We formulate this channel selection problem as a finite repeated potential game and propose two learning algorithms, Stochastic Learning Algorithm (SLA) and Stochastic Estimator Learning Algorithm (SELA) to achieve the Nash Equilibrium (NE) of the game. Numerical results show the convergence of the learning algorithms to the NE point of the game. The performance evaluation and impact of parameters on these two algorithms are also analyzed in our paper.

Coexistence Analysis of Multiple Asynchronous IEEE 802.15.4 TSCH-Based Networks

Low-power Wireless Sensor Networks (WSNs) play a key role in realization of the Internet-of-Things (IoT). Among others, Time Slotted Channel Hopping (TSCH) is a Medium Access Control (MAC) operational mode of the IEEE 802.15.4 standard developed for communications in short range IoT networks. TSCH provides high level reliability and predictability by its channel hopping mechanism and time division channel access nature. In many applications, a number of TSCH networks may coexist in the same neighborhood. Several vehicles close to one another, each including a TSCH network for its in-vehicle communications, serve as an example. Since such networks are running independent of one another, they are not expected to be synchronized in time, and they are not scheduled to operate in exclusive frequency channels. This may lead to inter-TSCH interferences deteriorating the reliability of the networks, which is an important requirement for many IoT applications. This paper analyzes the impact of multiple asynchronous TSCH networks on one another. An analytical model is developed that estimates the chance of such interferences, and the expectation of the number of affected TSCH channels when a number of them are in the vicinity of one another. The developed model is verified using extensive simulations and real-world experiments. Also, a scalable and fast multi-TSCH coexistence simulator is developed that is used to get insight about coexistence behaviors of any number of TSCH networks with various configurations.

Spectrum Allocation With Guaranteed Rendezvous in Asynchronous Cognitive Radio Networks for Internet of Things

The massive usage of Internet-of-Things devices in various smart applications enables spectrum scarcity issues. In order to enhance the dynamic spectrum capability, cognitive radio network (CRN) is considered as a key technology to address the spectrum scarcity problem. However, the establishment of a common communication channel in CRN by considering the unlicensed heterogeneous devices in an asynchronous environment is a challenging problem. In this paper, a novel asymmetric asynchronous channel hopping mechanism is designed, where secondary users have different sets of available channels and can enter into the network without any global clock synchronization. The proposed algorithms can guarantee the rendezvous within a small interval of time with minimum inter rendezvous intervals. Simulation results show that the designed protocol outperforms over the existing channel hopping algorithms in terms of the degree of rendezvous, average time to rendezvous and throughput.

Joint Scheduling and Channel Allocation for End-to-End Delay Minimization in Industrial WirelessHART Networks

WirelessHART is one of the most widely used communication standards in industrial wireless networks. In order to meet the stringent real-time requirements in industrial applications, WirelessHART incorporates many designs including the time slotted channel hopping mechanism that enables dynamic time scheduling and channel allocation. In this paper, we study the problem of joint transmission scheduling and channel allocation aiming to minimize the end-to-end delay of multiple flows in multihop WirelessHART networks. We propose a new network model based on a multidimensional scheduling space spanned by flow-link-channel-slot tuples. A multidimensional conflict graph is then established to depict the conflict relationships among the tuples. Based on this, the original delay minimization problem is formulated as an integer program, which however is difficult to solve due to its significantly large scale. To this end, we develop an iterative hop-wise scheduling algorithm by transforming the original problem into a series of maximum weighted independent set problems. We derive theoretical analysis on the schedulability and the performance bound of the proposed algorithm. In addition, we show that our results can be easily extended to accommodate more general scenarios. Finally, extensive simulation results are provided to demonstrate the effectiveness of the algorithm.

Channel List Selection Based on Quality Prediction in WirelessHART Networks

WirelessHART is one of the most widely used technologies in industrial wireless networks. However, its performance is highly influenced by the quality of wireless channels. To improve the reliability of wireless communications, WirelessHART employs channel blacklisting and channel hopping mechanisms, which highlights the importance of channel assessment. Traditional methods generally resort to packet reception ratio (PRR) of the previous time slot to assess and allocate channels, but this is not accurate. In this paper, we propose a learning-based framework for predicting the PRR, and on the basis of the predicted PRR, we develop a heuristic channel selection algorithm to confirm the channel list, which takes into account the balance of channel diversity and route diversity. Simulation results demonstrate that our algorithm outperforms existing ones in terms of achieved reliability.

Dynamic Spectrum Allocation Algorithms for Industrial Cognitive Radio Networks

Irregular spectrum usage and spectrum scarcity in emergency situations is a common problem in industrial wireless networks. To enhance the dynamic spectrum usage, cognitive radio network (CRN) is introduced in various automotive industrial wireless applications named as industrial cognitive radio network (ICRN). However, establishing the control channel by using channel hopping mechanism in ICRN is a challenging problem. In order to achieve reliable performance in ICRN, efficient channel hopping protocols need to be designed. In this paper, two channel hopping protocols are designed for the ICRN with or without the global clock synchronization to maximize the degree of rendezvous within the shortest time, minimize the inter rendezvous intervals and to reduce the maximum time to rendezvous by two secondary users. Performance evaluation of our protocols outperform in terms of throughput, percentage of rendezvous and average time to rendezvous over existing CRN protocols.

DeCoT: A Dependable Concurrent Transmission-Based Protocol for Wireless Sensor Networks

Concurrent transmission (CT)-based wireless sensor networks, where nodes transmit at the same moment upon receiving successfully, begin to be applied to real-world scenarios. CT-based protocols have been proven experimentally that they can achieve good the end-to-end performance, namely high reliability, low latency, and high energy efficiency. For various communication patterns (one-to-many, many-to-one, and many-to-many), most current CT-based networks require a given and fixed host to realize global synchronization and scheduling. However, in real-world cases, there is a great deal of interference in the 2.4 GHz ISM band. Interference can partition the network unexpectedly due to the centralized scheduling in current CT-based networks. Even worse, current CT-based networks cannot complete the initialization phase if the unexpected partition occurs at an very beginning. To address this problem, we propose a dependable CT-based protocol (DeCoT) for wireless sensor network (WSN) to support information exchange under adverse conditions. In DeCoT, continuous transmission with a channel hopping mechanism maintains links under interference and an initiated mechanism decentralizes the network. Through our experiments in FlockLab, under interference, DeCoT achieves an average reliability of 87%, and outperforms the state-of-the-art flooding protocol, namely Robust Flooding that won the 1st place in the EWSN 2017 Dependability Competition. Especially when the source nodes are placed sparsely, DeCoT speeds up the information exchange. Above all, DeCoT can complete the initialization and work properly even when the network partitions unexpectedly. DeCoT has been evaluated as the most reliable protocol in the EWSN 2018 Dependability Competition with respect to resistance against interference. Thus, DeCoT can function dependably under interference.

Priority-based scheduling using best channel in 6TiSCH networks

Many industrial wireless sensor networks deploy the IEEE 802.15.4-2015 standard with low power consumption and the Internet networking capabilities. The time-slotted channel hopping (TSCH) is an amendment to the medium access control protocol defined by the IEEE 802.15.4 standard. Furthermore, the Internet engineering task force (IETF) defines an architecture for IPv6 over the TSCH mode of IEEE 802.15.4 (6TiSCH) to provide deterministic properties on wireless sensor networks. The TSCH leverages the scheduled time slot to achieve low power operation and frequency hopping to combat external interference and multi-path fading. Although TSCH provides the channel hopping mechanism to increase transmission reliability, it is still susceptible to periodic interference for the specific frequency. In this research, we focus on the issue of random channel hopping in the error-prone wireless channel condition and the scheduling for different service requirements. We propose a priority-based scheduling using best channel (P-SBC) mechanism for periodic sensing data and emergency packets transmission in 6TiSCH networks. The simulation results show that the proposed P-SBC achieves higher reliability with significantly lower end-to-end latency for emergency packets transmission as compared to TSCH standard.

An Enhanced Analytical Model and Performance Evaluation of the IEEE 802.15.4e TSCH CA

The Time Slotted Channel Hopping (TSCH) mechanism is created in the IEEE 802.15.4e amendment, to meet the need of Industrial Wireless Sensor Networks. It combines time slotted access and channel hopping with deterministic behavior. The mechanism offers two types of links: dedicated links and shared links. In order to reduce the probability of repeated collisions in shared links, the mechanism implemented a retransmission backoff algorithm, named TSCH Collision Avoidance (TSCH CA). In this article, we develop a two dimensional Markov chain model for the IEEE 802.15.4e TSCH CA mechanism, we take into account the deterministic behavior of this mechanism. In order to evaluate its performances, we estimate the stationary distribution of this chain. Then, we derive theoretical expressions of: collision probability, data packet loss rate, reliability, energy consumption, throughput, delay and jitter. Then, we analyze the impact of the number of devices sharing the link for a fixed network size under different traffic conditions. Finally, the accuracy of our theoretical analysis is validated by Monte Carlo simulation. It is shown that the performances of the IEEE 802.15.4e TSCH parameters are strongly related to the number of devices sharing the link.

A Distributed Scheduling Algorithm for IEEE 802.15.4e Wireless Sensor Networks

As the widely adopted IEEE 802.15.4 standard exhibited severe drawbacks when used in multi-hop WSN environment, the IEEE Standards Association Board has released a revised version, IEEE 802.15.4e, which includes Time-Slotted Channel Hopping (TSCH) mechanism as the MAC amendment to IEEE 802.15.4. The key feature of IEEE 802.15.4e TSCH mechanism is to allow the sensors to plan the time-slot schedule for efficient data transmission. However, the standard does not specify how to plan a time-slot schedule so that data collected by the sensors can be received by the base station as soon as possible without being delayed by transmission conflicts. In this paper, we propose a constant-time, distributed time-slot scheduling algorithm to address this problem. Existing works on IEEE 802.15.4e TSCH scheduling depend on one or a few nodes to collect traffic-flow information from their descendants and plan a centralized time-slot schedule for the whole network. In contrast, our algorithm allows every sensor node to compute its time-slot schedule in a simple, truly distributed manner. Simulation results show that our algorithm significantly outperforms a state-of-the-art protocol in terms of the packet transmission delay and yields a smaller duty cycle.

A Study on Coexistence Capability Evaluations of the Enhanced Channel Hopping Mechanism in WBANs.

As an important coexistence technology, channel hopping can reduce the interference among Wireless Body Area Networks (WBANs). However, it simultaneously brings some issues, such as energy waste, long latency and communication interruptions, etc. In this paper, we propose an enhanced channel hopping mechanism that allows multiple WBANs coexisted in the same channel. In order to evaluate the coexistence performance, some critical metrics are designed to reflect the possibility of channel conflict. Furthermore, by taking the queuing and non-queuing behaviors into consideration, we present a set of analysis approaches to evaluate the coexistence capability. On the one hand, we present both service-dependent and service-independent analysis models to estimate the number of coexisting WBANs. On the other hand, based on the uniform distribution assumption and the additive property of Possion-stream, we put forward two approximate methods to compute the number of occupied channels. Extensive simulation results demonstrate that our estimation approaches can provide an effective solution for coexistence capability estimation. Moreover, the enhanced channel hopping mechanism can significantly improve the coexistence capability and support a larger arrival rate of WBANs.

Channel hopping scheme to mitigate jamming attacks in wireless LANs

Although a jamming attack is an important problem in Wi-Fi networks, there is no effective solution to this problem yet. In this paper, we propose a new approach to resolve jamming attacks in Wi-Fi networks based on the concept of channel hopping. If we assume that the attacker does not jam all the channels simultaneously, then it might be possible to circumvent a jamming attack by changing the channel. A channel hopping mechanism is designed so that the access point (AP) and a normal user can agree on the next channel with a high probability without pre-sharing of any secret information between the AP and a user node. The proposed scheme is evaluated through experiment in a test bed.

Load-aware channel hopping protocol design for mobile ad hoc networks

Using multiple channels in wireless networks improves spatial reuse and reduces collision probability and thus enhances network throughput. Designing a multi-channel MAC protocol is challenging because multi-channel-specific issues such as channel assignment, the multi-channel hidden terminal problem, and the missing receiver problem, must be solved. Most existing multi-channel MAC protocols suffer from either higher hardware cost or poor throughput. Some channel hopping multi-channel protocols achieve pretty good performance in certain situations but fail to adjust their channel hopping mechanisms according to varied traffic loads. In this paper, we propose a load-aware channel hopping MAC protocol (LACH) that solves all the multi-channel-specific problems mentioned above. LACH enables nodes to dynamically adjust their schedules based on their traffic loads. In addition to load awareness, LACH has several other attractive features: (1) Each node is equipped with a single half-duplex transceiver. (2) Each node's initial hopping sequence is generated by its ID. Knowing the neighbor nodes' IDs, a node can calculate its neighbors' initial channel hopping sequences without control packet exchanges. (3) Nodes can be evenly distributed among available channels. Through performance analysis, simulations, and real system implementation, we verify that LACH is a promising protocol suitable for a network with time-varied traffic loads.