Performance Modeling of IEEE 802.15.4-TSCH with Shared Access and ON-OFF traffic

International audienceMany applications for the Internet of Things require strict guarantees to operate properly. IEEE802.15.4-TSCH has been proposed to design a real-time access for industrial wireless networks. The standard relies on a strict schedule of the transmissions., and combines frequency hopping to provide high-reliability. While most of the propositions focus on a periodic traffic, we propose here to address the non-periodic case. In particular, shared access would be more efficient to reduce the power duty cycle by multiplexing the transmissions through the same cells. We propose here a Markov model for a shared access and sporadic traffic. By formulating the collision probability, the scheduler can decide how many transmitters to assign to a given shared cell according to the amount of traffic each node generates on average. The simulations validate the accuracy of our model to capture the collision rate for non-periodic traffic

Experimental Analysis of the Efficiency of Shared Access in IEEE802.15.4-TSCH Networks with Sporadic Traffic

International audienceIndustrial wireless networks are now used in many applications, and require to fulfill a certain set of requirements to operate properly. IEEE802.15.4-TSCH is considered a suitable solution to provide real time multihop transmissions in noisy and harsh environments. The standard relies on a strict schedule of the transmissions to reduce the radio duty cycle ratio. While constructing a schedule for periodic traffic has been widely studied in the past, we focus here on the aperiodic, sporadic case. We have to multiplex the transmissions in the schedule to reduce the energy consumption while limiting the number of collisions to provide still high reliability. We propose here to study experimentally the performance of TSCH with shared access and bursty arrivals. Then, we demonstrate how to re-adapt the scheduler to better deal with unpredictable traffic. By performing experiments, we can predict the optimal number of transmitters in a shared cell. Thus, we can overcome collisions and packets drops in complex scenarios where bursty traffic is required

Performance Study of Co-Located IEEE 802.15.4-TSCH Networks: Interference and Coexistence

International audienceWith the large deployment of smart and heterogeneous devices, interest of researchers to define new protocols to meet Internet of Things (IoT) requirements is growing. A particular interest was accorded to define a robust MAC layer for wireless sensor networks, in order to reduce interference caused by other co-located networks and applications using the ISM band. This paper gives a comprehensive study of the Time Slotted channel Hopping IEEE802.15.4, part of the 6TiSCH stack and explains how its TDMA approach improves the reliability with performance guarantees. We also investigate analytically and experimentally the impact of the scheduling algorithm on the reliability. Then, we provide an experimental evaluation of co-located WSN using the FiT-IoT LAB testbed and the OpenWSN Stack. Performance analysis of IEEE802.15.4e-TSCH is achieved with a variable number of co-located synchronized or unsynchro-nized instances. While this standard is robust for lightly loaded networks, new mechanisms have to be proposed when we have too much traffic or too many interfering networks

Cooperative Resynchronization to Improve the Reliability of Colocated IEEE 802.15.4-TSCH Networks in Dense Deployments

International audienceWith the large adoption of small and smart objects, the interest of researchers to define new protocols to meet Internet of Things (IoT) requirements is growing. In particular, the Industrial Internet of Things (IIoT) aims to provide high reliability and upper bounded end-to-end latency while interconnecting a large collection of sensors and actuators. The TimeSlotted Channel Hopping (TSCH) mode of IEEE 802.15.4 exploits a slow channel hopping approach to combat efficiently external interference (e.g. Wi-Fi, Bluetooth). We envision in the future very dense deployments and we investigate here the mutual influence among different colocated TSCH networks. We first study analytically with a simple model the performance of several TSCH networks, able or not to be synchronized with each other. We emphasize the multiplication of collisions, exacerbated by clock drifts when no cooperation is achieved. We also highlight experimentally that a mutual synchronization improves very significantly the reliability. We propose here a mechanism to re-synchronize distributively the border routers of different TSCH networks. Our thorough experimental evaluation illustrates the relevance of our approach, able to guarantee high-reliability, even in very dense topologies