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So, we have already been writing about IoT connectivity, but I wanted to investigate if there’s solution suitable for existing SCADA (Supervisory Control and Data Acquisition) systems.

I’ll be focusing on wireless connectivity of SCADA systems for critical utility services that we take for granted, but without them we couldn’t live on a today’s standards, like for example water, electricity, oil and gas. SCADA systems for controlling and monitoring of water, electricity, oil, gas are pretty much mature,  stable systems and they support usage of different wireless connectivity solutions. In today’s businesses, everybody is looking for a way to optimize the processes and cut costs, utilities behave the same – some water utility company would like to know about any leakages that they have, react on time, fix them as soon as possible and not lose money. This means that a lot of new sensor will be brought to the system and that they need to be reliable but also need to be price competitive and IoT is seen as a perfect candidate. What we might see as a cause effect is that utilities will start asking themselves are those IoT systems suitable for replacement of our existing SCADA solutions, where can we have immediate cost savings if we use IoT – and here I see connectivity as a first point to start.

Traditionally SCADA systems use VHF/UHF point to multi-point wireless connectivity solutions. Networks are built around base station that polls data from end points or receive data when there’s a alarm on the end point. Planning, commissioning and maintaining of those networks can be challenging and you’re dependent on one vendor for any future expansion, feature development and support. Data rates varies from 39 kbit/s in 12.5 kHz channel up to 1 Mbit/s in 150 kHz channel (depending what are the RF regulations in your country and what local RF regulator has to offer in specific area).

GPRS (General Packet Radio Service) had a great impact on SCADA connectivity and now we see it as a most widely used solution. Reason for this is that it’s more cost effective and easier to implement than VHF/UHF systems, since the coverage is usually very good. For sure there are some drawbacks, like latency that depends on network loading, there no QoS guarantee, data rate in practice is around 20 – 40 kbit/s.        

TETRA (TErrestrial Trunked RAdio) was originally developed for public safety segment with emphasize on voice communication. Today we see it more and more present within utility segment that finds this technology as a good fit for its needs, since it’s offering voice and data capabilities in once, high level security (mutual authentication, air interface encryption and end-to-end encryption), QoS, it mature technology and it’s not so expensive as it was before. TETRA’s data services SDS (Short Data Service) uses control channel and can transfer 130 8-bits character in 1-2 seconds, while and PD (Packet Data) uses static or dynamic (switches between voice and data usage) dedicated packet data channel that is IP based and can offer up to 12 kbit/s if we use all 4 time slots of TETRA’s 25kHz traffic channel.

DMR (Digital Mobile Radio) firstly designed for voice communication, but lately DMR is something that we see emerging  for data communication as well. By nature, it’s very similar to TETRA trunking but a bit more cost effective and available in VHF for wider area coverage. It offers data rate of around 4.8 kbit/s in 12.5 kHz DMR traffic channel. Biggest drawback is that DMR is not mature standard, that it’s not yet a widely proven solution for data communication and that it’s not really a “standard” as TETRA and you are stuck to one vendor for all the expansions, new feature development and future support of your solution.

Satellite connectivity is also seen more and more as SCADA’s connectivity solution, since pricing of the VSAT (Very Small Aperture Terminals) is getting lower. It’s not wide spread solution, but it’s very suitable for some remote areas with no adequate terrestrial infrastructure.   

In last few years we are witnessing an incredibly fast development of IoT’s LPWAN (Low-Power Wide-Area Network) connectivity solutions from licence (LTE-M, NB-IoT) to licence-exempt (LoRa, Sigfox). Key requirements of IoT’s LPWAN solutions are: low unit cost of edge device, low data rate, high cell density, 10+ years of battery life, simple out-of-the box installation and commissioning, tolerance to increased latency. Predictions say that there’s be billions of those devices – so can this have impact on today’s’ SCADA connectivity solutions?      

               NB-IoT

               CAT-M

DL/UL data rate

up to 250 kbps/250 kbps

up to 1 Mbps/1 Mbps

Latency

up to 10 s

up to 15 ms

Service type

Half-duplex

Full and Half-duplex

Link budget

164 dB

156 dB

Device Tx power

20/23 dBm

20/23 dBm

Battery life (2 AA)

> 10 years

> 10 years

Channel Bandwidth

180 kHz

1.4 MHz

As we can see on GSMA deployment map, operators across the EU are mainly rolling out NB-IoT networks, while LTE-M roll out is dominating in the USA. When I look at the data for licenced connectivity solutions, what I find interesting is very low latency of the LTE-M and this is very important factor for critical SCADA use cases. So, if you are in part of the EU where Orange is present you can “come and test your connected device for free in Europe’s first open IoT Lab dedicated to LTE-M”.

In licence-exempt connectivity solution offering we have LoRa and Sigfox as two dominating solutions. LoRa is  is an open standard solution developed by the LoRa Alliance. LoRa uses chips developed by only one vendor, and this is Semtech. It uses  868 MHz unlicensed spectrum in EU, but there’s no protection from RF regulators in regards to interference in this band and everybody need to obey to limits on usage of power and duty cycles. You can build your private LoRa network, and this is especially interesting for some remote areas (like Croatia’s islands) with no adequate service offering and opportunity to develop a healthy business case. Anyhow, according to LoRa Alliance coverage map there’s 83 LoRa operators worldwide.  

Sigfox is proprietary solution and it’s expanding by principle of operator partners that need to sign a contract with Sigfox for specific country in which they plan to deploy and offer Sigfox network. It also uses 868 MHz unlicensed spectrum in EU with no  protection from RF regulators in regards to interference, so there are power and duty cycles limitations that need to be respected to have everything working properly. According to Sigfox coverage map there’s over 50 Sigfox operators worldwide.  

  LoRa

Sigfox

DL/UL data rate

up to 50 kbps/50 kbps

up to 8 bytes/up to 12 byte

Link budget

Up to 157dB @ 250bps

160 dB

Battery life (2 AA)

> 10 years

> 10 years

Channel Bandwidth

125kHz/250 kHz

100 Hz

Device Tx power

27 dBm

27 dBm

Latency

UL ALOHA followed by DL/periodic DL/continuous DL

Max. 140 messages/day UL 4 messages/day DL

LoRA and Sigfox are dedicated IoT connectivity solutions and they have to be built from the scratch but at the same time they need to offer very low cost of subscription and good QoS. This is a big challenge, costs need to be under control and there might be some savings, for example on the resilience  of the network.

What’s coming next is the 5G and it will offer higher data rates, lower latency, improved coverage, higher user density per cell, prioritised traffic, high availability and reliability. 5G is also introducing feature called network slicing by which MNOs could offer “slices” optimised for some specific customer needs, so there might be a “slice” optimized for SCADA systems usage. Potential of 5G is enormous, but we will see how it will go with adaptation in future , since LTE has quite a good offer of services and 5G roll out requires big investments from the MNOs as the need to built a new RAN (Radio Access Network).   

So, if we look up to date situation, we can see that SCADA systems relied on connectivity solutions that are designed to be resilient (in terms of power, transmission) and with no single point of failure – this is not cheap to achieve. That’s why we can’t have our eyes closed on the fact that licensed and licence-exempt network operators have improved coverage of their networks, that they offer new services that are cost effective – but please bare in mind that they must offers you an level of security, resilience and performance which will not jeopardize your core business.  

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