Internet of Things by Subhas Chandra Mukhopadhyay

Author:Subhas Chandra Mukhopadhyay
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

2.4 TSCH Deterministic Networks

The IEEE802.15.4e TSCH, due to the combination of Time Division Multiplexing (TDM), time synchronization and the time formatted into slotframes, results in a deterministic wireless MAC standard, suitable for deterministic traffic, i.e., traffic flows with an emission rate and routing path patterns that are well-known in advance. For such traffic, a deterministic network allocates the required resources (buffers, processors, medium access) along the multi-hop routing path at the precise moment the resources are needed. In a TSCH network, the bandwidth is pre-formatted in a TDM fashion. Thus, unlike the traditional CSMA/CA-based networks, there is no contention for gaining access to the channel. In fact, a time slot becomes a unit of throughput that can be allocated to a given deterministic flow. Deterministic networks are also adapted by Traffic Engineering, i.e., to support several isolated flows. Different optimized paths and tracks can be built for all the isolated flows, based on their specific requirements.

A deterministic network guarantees timely transmission. A good example of a deterministic network is a railway system, where trains are scheduled periodically to leave a railway station at a certain time, to traverse the stations along a predetermined track at precise times so that, in the end, a given train arrives at its final station at the expected time, with virtually no jitter from a human perspective. Moreover, collisions are eliminated: there is never another train blocking the rail and delaying this train.

The IEEE802.15.4e TSCH, with its deterministic behavior, opens up a set of new applications which require high reliability and low-power. It enables control loops in wireless process control/automation networks, where wired solutions have been used so far. Supporting Traffic Engineering and isolated traffic flows, it enables umbrella networks, transporting data from different independent clients. Each flow is isolated and shaped, according to the requirements specified by the client. With its low-power nature and predictable power consumption, TSCH enables networks of energy harvesting motes. Finally, it supports widespread monitoring (like corrosion monitoring or pipe leak detection), which requires slow periodic reporting rates from a large number of sensors and open loop operation. More details about potential 6TiSCH applications are provided in Sect. 4.

These new applications will make a lot more sense if they are able to reuse the same building blocks and thus share a same converged network for IT/OT, based on an IPv6-architecture.

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