Citation: Orozco-Santos, F.;
Sempere-Payá, V.; Silvestre-Blanes, J.;
Albero-Albero, T. TSCH Multiflow
Scheduling with QoS Guarantees: A
Comparison of SDN with common
Schedulers. Appl. Sci. 2022, 12, 119.
https://doi.org/10.3390/app12010119
Academic Editor: Alvaro Araujo
Pinto
Received: 16 November 2021
Accepted: 20 December 2021
Published: 23 December 2021
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Article
TSCH Multiflow Scheduling with QoS Guarantees:
A Comparison of SDN with Common Schedulers
Federico Orozco-Santos
1,
* , Víctor Sempere-Payá
1,2
, Javier Silvestre-Blanes
1,3
and Teresa Albero-Albero
1,3
1
Instituto Tecnológico de Informática (ITI), 46022 Valencia, Spain; vsempere@dcom.upv.es (V.S.-P.);
jsilves@disca.upv.es (J.S.-B.); talbero@disca.upv.es (T.A.-A.)
2
Departamento de Comunicaciones (DCOM), Universitat Politècnica de València (UPV), 46022 Valencia, Spain
3
Departamento de Informática de Sistemas y Computadores (DISCA), Universitat Politècnica de València
(UPV), 03801 Alcoy, Spain
* Correspondence: forozco@iti.es
Abstract:
Industrial Wireless Sensor Networks (IWSN) are becoming increasingly popular in pro-
duction environments due to their ease of deployment, low cost and energy efficiency. However, the
complexity and accuracy demanded by these environments requires that IWSN implement quality
of service mechanisms that allow them to operate with high determinism. For this reason, the IEEE
802.15.4e standard incorporates the Time Slotted Channel Hopping (TSCH) protocol which reduces
interference and increases the reliability of transmissions. This standard does not specify how time
resources are allocated in TSCH scheduling, leading to multiple scheduling solutions. Schedulers
can be classified as autonomous, distributed and centralised. The first two have prevailed over the
centralised ones because they do not require high signalling, along with the advantages of ease of
deployment and high performance. However, the increased QoS requirements and the diversity of
traffic flows that circulate through the network in today’s Industry 4.0 environment require strict,
dynamic control to guarantee parameters such as delay, packet loss and deadline, independently
for each flow. That cannot always be achieved with distributed or autonomous schedulers. For this
reason, it is necessary to use centralised protocols with a disruptive approach, such as Software
Defined Networks (SDN). In these, not only is the control of the MAC layer centralised, but all
the decisions of the nodes that make up the network are configured by the controller based on a
global vision of the topology and resources, which allows optimal decisions to be made. In this
work, a comparative analysis is made through simulation and a testbed of the different schedulers
to demonstrate the benefits of a fully centralized approach such as SDN. The results obtained show
that with SDN it is possible to simplify the management of multiple flows, without the problems of
centralised schedulers. SDN maintains the Packet Delivery Ratio (PDR) levels of other distributed
solutions, but in addition, it achieves greater determinism with bounded end-to-end delays and
Deadline Satisfaction Ratio (DSR) at the cost of increased power consumption.
Keywords: AMUS; IWSN; Orchestra; QoS; SDN; TSCH
1. Introduction
The adoption of Industrial Wireless Sensor Networks (IWSN) in industry requires
devices and protocols that can guarantee physical operation and greater determinism in
transmissions [
1
]. In order to satisfy the latency and reliability requirements of automation
systems, even in converged environments, in which multiple information flows with
different levels of priorities are involved. Therefore, the IEEE 802.15.4 standard, which
specifies the physical and medium access control layers, has been updated to IEEE 802.15.4e.
It maintains the physical layer, which consists of 16 channels in the 2.4 GHz band, and the
medium access control replaces Carrier Sense Multiple Access with Collision Avoidance
(CSMA/CA) with three new protocols [
2
] to support different types of industrially oriented
Appl. Sci. 2022, 12, 119. https://doi.org/10.3390/app12010119 https://www.mdpi.com/journal/applsci
