A Joining Procedure and Synchronization for TSCH-RPL Wireless Sensor Networks

[EN] Wireless Sensor Networks have become a key enabler for Industrial Internet of Things (IoT) applications; however, to adapt to the derived robust communication requirements, deterministic and scheduled medium access should be used, along with other features, such as channel hopping and frequency diversity. Implementing these mechanisms requires a correct synchronization of all devices in the network, a stage in deployment that can lead to non-operational networks. The present article presents an analysis of such situations and possible solutions, including the common current approaches and recommendations, and proposes a new beacon advertising method based on a specific Trickle Timer for the Medium Access Control (MAC) Time-Slotted Channel Hopping (TSCH) layer, decoupling from the timers in the network and routing layers. With this solution, improvements in connection success, time to join, and energy consumption can be obtained for the widely extended IEEE802.15.4e standard.This work has been supported by the SCOTT Project (Secure Connected Trustable Things), (www.scottproject.eu), which has received funding from the Electronic Component Systems for European Leadership Joint Undertaking under grant agreement No 737422. This Joint Undertaking receives support from the European Union's Horizon 2020 research and innovation programme, and from Austria, Spain, Finland, Ireland, Sweden, Germany, Poland, Portugal, Netherlands, Belgium, and Norway.Vera-Pérez, J.; Todoli Ferrandis, D.; Santonja Climent, S.; Silvestre-Blanes, J.; Sempere Paya, VM. (2018). A Joining Procedure and Synchronization for TSCH-RPL Wireless Sensor Networks. Sensors. 18(10). https://doi.org/10.3390/s18103556S181

Otimização da eficiência energética em redes operando com tsch: avaliação analítica de uma implementação prática.

The IEEE 802.15.4-2015 standard defines a number of Medium Access Control (MAC) layer protocols for low power wireless communications, which is desirable for constrained Internet of Things (IoT) devices. Originally defined in IEEE 802.15.4e amendment, the Time Slotted Channel Hopping (TSCH) is recently attracting the attention from the research community, due to its reduced contention (time scheduling) and robustness (channel hopping). However, the TSCH needs a certain level of synchronization between the nodes, which can lead to a higher energy consumption. A guard time mechanism is implemented to ensure that the nodes will hear the frames even if they are not perfectly synchronized. In this work, we implement the Guard Beacon strategy, aiming to reduce the guard time, and present a realistic energy consumption model for a Contiki OS-based TSCH networks. The analytical values have a good match with the results obtained from the Contiki Powertrace Tool running on a real TSCH network and demonstrate that the proposed scheme can reduce the overall power consumption of each node by 13.05%.O padrão IEEE 802.15.4-2015 define novos protocolos para a camada de acesso ao meio (MAC, do inglês Medium Access Control) com foco em redes de comunicação sem fio com baixo consumo de energia, o que é desejável para dispositivos de Internet das Coisas (IoT, do inglês Internet of Things) que apresentam restrições energéticas. Originalmente definido na emenda IEEE 802.15.4e, o esquema de Salto de Canais por Intervalo de Tempo (TSCH, do inglês Time Slotted Channel Hopping) tem atraído atenção da comunidade científica devido ao nível reduzido de contenção (agendamento no tempo) e robustez (salto de canais). Entretanto, para operar corretamente o TSCH necessita de um determinado nível de sincronização entre os nós da rede, o que pode levar a um maior consumo de energia. Um mecanismo de tempo de guarda é implementado para assegurar que os nós irão “ouvir” os pacotes ainda que não estejam perfeitamente sincronizados. Neste trabalho, implementa-se a estratégia de Guard Beacon visando reduzir o tempo de guarda necessário, e se apresenta um modelo de consumo de energia realista para redes operando com TSCH e Sistema Operacional Contiki. Os resultados analíticos têm boa precisão quando comparados com os resultados obtidos de uma rede TSCH real através da ferramenta Powertrace do Contiki e demonstram que o esquema proposto pode reduzir o consumo de energia geral de cada nó em até 13,05%