Smart Metering & Sigfox
This article details how smart water metering systems are utilising Sigfox to provide new solutions and price points. The intended audience is those who are interested in better managing resource use, lowering cost, and those interested in understanding new disruptive technology, business models, and scalable low cost solutions for smart metering.
What is Smart Metering?
There are various definitions used throughout the industry for smart metering. My definition is: Smart metering is the digital recording of resource usage such as water, gas, and electricity. It includes the hardware that collects the data, the methods of delivering that data to users, and the applications that transform this data into meaningful insights that drive actions and outcomes. To further define smart metering, one may include a higher detail of data collected e.g. meter readings taken more frequently than once per hour. It may also include or two-way communication between the devices in the field and the systems that operate them. This will differentiate smart metering from automated meter reading (AMR) systems which typically deliver meter readings daily or less frequently and offer only one-way communications.
Smart Metering Device with Sigfox Communications
What is Sigfox?
Sigfox is a global wireless communication provider and the name of the wireless network solution that it offers. Sigfox was founded as a company in France in 2009 and continues to rapidly roll out its wireless network across the world.
Unlike a traditional wireless network, the Sigfox network does not cater to voice communications or high speed, high volume data for video streaming to mobile phones. Sigfox is specialised in enabling Internet of Things (IoT) connectivity as simply and economically as possible. This is achieved by providing a low power, wide area network (LPWAN), a back-end infrastructure to receive and distribute data, and an ecosystem of lower power consumption radio module suppliers, device producers, consultants, and system integrators to deliver solutions that operate on the Sigfox network.
The network is made up of base stations (think very small and light radio equipment) which are installed on top of buildings and other tall structures to communicate with devices in the surrounding areas. These base stations offer long range connectivity across wide areas which means large geographic regions can be covered with a smaller number of base stations relative to other communication technologies.
Smart Metering System Overview with Sigfox Connectivity
The advantages of Sigfox over other wireless communication solutions make it ideally suited to smart metering applications, particularly for water and gas where metering devices typically no access to power outlets and the metering devices must therefore operate on batteries.
The area of coverage is expanding rapidly so these figures grow quickly, but as of May 2017, 512 million people in 32 countries across 6 continents live within a Sigfox coverage area. The areas of coverage are predominantly focused on population centres such as major cities. Sigfox state a target of operating in 60 countries by 2018. In many countries Sigfox has partners which function as the local Sigfox Operator (SO). In Australia, the local SO is Thinxtra, who have rolled out network coverage to approximately 70% of the Australian population as well operating networks in New Zealand and Hong Kong.
Sigfox operates on ISM (Industrial, Scientific, and Medical) radio bands. Sigfox groups each country in the world into four regions, with each region operating on one of four frequencies.
Summary of Sigfox Regions
Sigfox is rolling out its network on the principle: ‘build it and they will come’. This removes a huge cost item and barrier to entry for smart metering projects. The majority of large scale smart metering projects require the establishment of a wireless network consisting of base stations (i.e. small radio towers), range extending relays, network servers, and back-end systems. The cost of the wireless network infrastructure is typically a significant portion of the total smart metering project cost.
With Sigfox, one simply deploys devices and starts sending data. If a project is in an area with little or no existing Sigfox coverage, the local SO may be willing to assist in reinforcing the network in the area for minimal (or even zero) cost to ensure that your Sigfox enabled project is a success. This is beneficial for those wanting to roll out a smart metering project as it minimises costs and barriers to deployment. It also benefits Sigfox and the SOs as it helps them in their goal of expanding their network to enable new users and devices.
For smaller projects or very remote areas where coverage is not available, it may be difficult for an SO to justify the deployment of low-cost or no-cost base stations. In these instances an SO may be able to offer other solutions. Thinxtra offer a ‘Sigfox-in-a-Box’ product where users are provided with a miniature base station and a ‘Coverage as a Service’ arrangement to provide base stations and coverage for such an area.
There are many recounts of extremely long range transmissions. For example, from the South Island of New Zealand to the North Island (212kms), and Ireland to Spain (1,024kms). While this is impressive, it is more important to consider the ‘every day’ repeatable performance with commercially available products.
In our testings we have achieved highly repeatable results of transmitting water meter readings 10kms through dense urban environments. For example, at a testing location 4kms from the city centre of Sydney, our Sigfox enabled smart meters successfully connected to three base stations simultaneously. These base stations were in separate locations between 4 and 8kms, in different directions from the transmitting device with no direct line of site. In fact, between the transmitting device and the receiving base stations there were hills, skyscrapers, industrial areas, train lines, and hundreds of houses in the most densely populated areas of the city.
Example of Typical Sigfox Range Performance in Sydney
Reliability of Service
Many major population centres where Sigfox has been rolled-out can benefit from redundant coverage where devices will be able to transmit to multiple base stations from one location. This gives extra assurance that messages will be received. Most city centre areas will be covered by at least 3 base stations, and often more. City outskirts and regional areas may be covered by 1 or 2 base stations only which will still give a high transmission success rate.
Each time a device transmits a message, it transmits it 3 times on separate randomised frequencies within the given range. This is called ‘frequency hopping’. It accounts for external interference on the spectrum and greatly increases the chance that the messages will be received by the base station. All authenticated messages received by the base station are then sent to the cloud for processing where duplicated messages are consolidated and stored as one message.
Designing a wireless system that can guarantee a perfect 100% success rate for transmissions is challenging. All smart metering should be designed to be resilient to unsuccessful transmission events. If a message is not received by a base station, for example if changes in the physical environment around the device inhibit signal strength, the information should not be lost and should be delivered upon the next successful transmission. Automatic Meter Reading (AMR) systems should store the current meter reading in the local memory on the device. By always storing an accumulating total of water consumption, the next successful transmission will always contain the latest accurate meter reading. This gives redundancy and is superior to sending only the total water use since the last transmission.
Water and gas meters are often in challenging locations in terms of signal penetration and wireless connectivity. Meters may be in basements, underground car parks, under man-holes and metal coverings. This often requires additional parts such as higher gain antennas and extra installation time to ensure reliable connectivity. Due to the low frequency and ultra-narrow band nature of Sigfox, these situations are overcome with relative ease when compared to other radio systems.
In real world testing of Sigfox smart meters we have seen consistently impressive results in basements, car parks, and under metal covers such as man-holes.
Manhole with Steel and Concrete Lid
The most effective metric for assessing the capacity of the network is the maximum number of messages which can reliably be received by the network per day. Each Sigfox base station can receive a maximum of around 1.5 million messages per day. If a city has 100 base stations deployed in its network, the maximum number of messages that can be received in that city is 150 million per day. This is of course dependent on the geographic concentrations of transmitting devices in specific areas and timing of each message. If an area is experiencing a lack of capacity, the simplest solution is to add more base stations to receive the messages while also adding to the network coverage.
Usually water meters are not located near power outlets nor with sufficient sunlight to run on solar power. Thus, the majority of smart water metering systems rely on long-life batteries to power electronic hardware. This presents a challenge to ensure cost effective project delivery as battery replacements require expensive site visits with manual labour. If the battery consumption can be minimised, lower cost of life of projects can be achieved.
Sigfox devices have incredibly low power consumption relative to their ability to transmit data.
For example: Assume a smart metering device is used to transmit 12 times a day. It is equipped with a common Lithium battery (LiSOCL2) at 3.6VDC and 16,000mAh capacity.
With a 250mA transmit current, a modest 20uA stand by power consumption, and 1% battery degradation per year, this device will last for ~13 years by calculation. This is in excess of the expected maximum usable life of the battery.
Example of Common Long Life Lithium (Li-SOCl2) Battery
Another benefit of Sigfox in terms of battery consumption is consistency. Each transmission will consume practically the same amount of power. This makes predicting battery life much easier than many other communication technologies. Other communication technologies will lead to varying battery life of devices depending on signal quality. If the device is installed in a low signal area, the radio will consume more power while trying to deliver its data. Having a high variability in battery life from one device to the next makes scheduling battery replacements and pre-emptive maintenance challenging, especially with large scale roll-outs. This is not an issue with Sigfox.
Data Packet Size
Sigfox is designed around maximising the efficiency of delivering small packets of data. As such, the data packet size per transmission is very small, at a maximum of only 26 bytes. Each packet contains a 14 byte header containing preamble, frame sync and header, device ID, authentication, frame check sequence and a maximum of 12 bytes for the ‘payload’. The payload is the metering information such as water consumption values. A typical smart metering data set for a 24 hour period with 15min interval meter readings may be 80 to 200 bytes. This would appear to be a major limitation of the Sigfox technology, but, there are solutions and even advantages to Sigfox’ small packet size.
With the lower power consumption in mind, it is possible for a Sigfox device to transmit data in real-time while consuming battery power at a similar rate as a 3G device which sends data only daily (near-real-time). The advantage is that real-time data streams enable faster analytics and alerting of abnormal water use e.g. leaks and theft. This is contrary to the common perception that Sigfox is only suitable for the most basic metering functions.
It is also possible to compress a high amount of useful information such as multiple meter readings into the 12 bytes. This may reduce the number of transmissions required to deliver interval meter readings by a half or two thirds, while also reducing the demand on battery consumption by around 20-40%.
Without any additional compression or additional battery capacity, Sigfox is perfect for applications where quarterly, monthly, weekly, daily or even hourly meter readings are required.
Sigfox provides both uplink and downlink capabilities. This means that devices can feed data from the field up to the cloud, and messages can be sent from the cloud down to the device. Downlink messages can be used to change configuration of smart metering devices. For example, a downlink message could tell a smart metering device to change its upload frequency from daily to hourly in order to collect more detailed data on utility resource use.
Downlink messages are small at only 22 bytes including 14 bytes for the message header and a maximum of 8 bytes for the payload. These small downlink messages are not designed for firmware upgrades. Devices must be deployed with all required features already built in. If firmware upgrades are essential to a smart metering project, such as when a device is deployed prior to development of all required features and functionality, another method can be employed. For example, devices can be equipped with low-cost Bluetooth radios or other wireless modules to allow for future firmware updates.
All Smart Metering must have an appropriate level of security embedded into all layers of the system. To determine the right level of security for a project the risk, cost, and effort needed to meet the key requirements must be considered. Smart metering systems must provide security of data, privacy of user information, and resilience to outside attacks that can obstruct successful and secure operations. Consider Sigfox as a viable alternative to dedicated smart metering networks and IPv6 enabled devices.
The below video gives an overview of the Sigfox architecture relative to security:
Sigfox Security Overview Video
Security On the Device
An important concept to consider is that Sigfox enabled devices are not directly connected to the internet. Although Sigfox devices can be categorised under the tag-line ‘Internet of Things’, unless other communication types are installed in the device (e.g. Wi-Fi, 3G, NB-IoT), Sigfox devices connect only to the Sigfox network via Sigfox base stations.
Sigfox devices only transmit on occasion and for brief period of time. These transmissions may be scheduled, or based on events such as sensor reading changes.
As the radio in the device is typically in sleep-mode to maximise battery life, Sigfox devices can only receive downlink messages at scheduled or event based times. Downlink messages are delivered via Sigfox base stations only. A device will only recognise and receive downlink messages that contain the unique device identification key for that specific device. Downlink messages are Sigfox-encrypted. The device provider can elect to separately encrypt the downlink payload for an extra layer of security. Device suppliers can also elect to encrypt information stored in local memory on the device.
Due to the nature of Sigfox communications it is exceptionally challenging to undertake malicious attacks on devices remotely. Any communications over the Sigfox network must be addressed to specific devices including unique serial number, message sequence number, Sigfox encryption, and any additional supplier encryption on the packet.
Security On Network Infrastructure
The Sigfox network is highly resistant to signal jamming and interference, whether it is coincidental or malicious. This is due to the ultra-narrow-band frequencies and frequency-hopping capability where each transmission is repeated three times on randomised frequencies.
All Sigfox devices are provisioned with a unique identification number set by Sigfox and the manufacturer. These identification numbers are included in the header of each packet transmitted by a device. Only transmissions containing these unique IDs are recognised by Sigfox and delivered through to the back-end. These identification numbers are stored on the device in read only memory.
All data transmitted by Sigfox devices also contains a sequence number unique to each transmission. The sequence number increases with each transmission. This prevents the message from being maliciously recorded and replayed as the system will reject any transmissions which are out of sequence.
The message header is encrypted. The device maker can also apply their own encryption on the packet data to give another layer of data protection if they choose.
Gateways are installed in secure locations where they are not readily accessible to the public. In the event that the gateway hardware is accessed by an authorised party, an alarm will trigger to alert the network operator.
Gateways are equipped with a firewall to prevent unauthorised incoming messages. Only out-going connections to the Sigfox cloud and specific requests from authorised IPs are allowed.
Security On the Cloud
Once data reaches the Sigfox back-end it is stored in the Sigfox cloud servers with fail-safe servers in separate locations. From there, data can be accessed by authorised application servers to load the data into visualisation platforms, meter data management (MDM) systems, and other data storage.
Sigfox state in this publicly available white paper:
“In the IT segment, the Sigfox Core Network is essentially a cloud-based network. As such, it benefits from proven internet technologies and suppliers. More specifically, the Sigfox Core Network is hosted in secured certified data centers. Each rack is secured with biometric protection for physical access.
Each data centre is doubly internet-attached through different internet transit providers. By design, Sigfox architecture is fully load-balanced and redounded from the core switching to the applicative servers based on virtual machines through double-attached physical servers. At the application layer, each component is fully redundant, strongly monitored and fully scalable to support any increase in traffic.
The cloud-based model of Sigfox ensures high availability access to the Sigfox Operational and Business Support Systems service components, decreasing downtime and other operational risks controlled by the Sigfox Service Continuity Plan.
A dedicated solution protects Sigfox data centres against a wide range of denial-of-service cyber-attacks such as denial-of-service (DoS), distributed denial-of-service (DDoS), reflective denial-of-service (RDoS), and distributed reflective denial-of-service (DRDoS). This solution, supplied and maintained by our internet service provider, offers a cloud-based protection service with several scrubbing centres in order to detect and mitigate cyber-attacks against networks and websites. This solution uses proprietary detection and mitigation algorithms matching Sigfox-specific traffic patterns to prevent false positives.”
Sigfox has established a growing eco-system of partners and vendors to provide products and services that utilise the Sigfox network. To achieve this, Sigfox must be highly interoperable with other parties and systems.
Any electronic device can be fitted with a Sigfox compatible radio module and can start delivering data. Data can then be accessed from the Sigfox back-end via the Sigfox API or push functions. Either applications can receive the data directly from Sigfox, or one of the many IoT platforms that have partnered with Sigfox can transform the data to load into your applications in the preferred format.
WaterGroup, in partnership with Reekoh, have the facilities to integrate Sigfox smart metering data with other systems such as Envizi, Hypercat, SAP, Microsoft Azure, Google Cloud Datastore, AWS IoT, SCADA systems, BMS, EMS, and practically anything else.
Selection of WaterGroup & Reekoh System Integration Plug-ins
This is a major concern for utilities and others making significant investments in large scale smart metering systems. Traditionally, many large scale smart metering systems have been built on closed ecosystems where hardware, wireless communications, network infrastructure, and applications are proprietary and therefor difficult or even impossible to interoperate with products and services from more than one vendor.
Sigfox provides users with the ability to interoperate with hardware and software applications from multiple vendors. This opens up options for every component outside of the wireless communication layer and network server.
Capex and Opex Costs
The cost benefits of Sigfox relative to other technologies are predominantly in 3 areas; hardware devices, wireless network establishment, and wireless data delivery service. Keep in mind that these are only three cost aspects of a smart metering project. There is much more to consider such as device deployment, back-end infrastructure, maintenance, data analytics, user applications, customer applications, project management, and driving outcomes from the data. For a holistic understanding of what is required in a smart metering project, read this article. Costs mentioned in this article are an indication only. Actual costs depend on many variables relative to specific projects.
The most expensive individual components in a retro-fit smart metering device that are dependent on the wireless communication choice are typically the battery, and the radio module. Sigfox enabled devices have advantages in these areas, for example, super-low power consumption means the device can last many years on smaller (less expensive) batteries than other wireless technologies would require.
The radio module itself is very cheap. Sigfox have worked with radio module suppliers such as WiSOL and Innocomm to ensure radio modules are available at highly competitive price points. Sigfox often state US$2 for radio modules. These modules are Sigfox and local regulator certified. While some cost a little more than US$2, some actually cost less. Minimum order quantities are low (e.g. 1,000 units).
Relative only to large scale deployments, it is possible for Sigfox smart metering and AMR devices to be procured for as little as $50 depending on the volumes and specification. An example of what is achievable at this price point is a simple smart metering device that retro-fits to existing water meters, at a volume of, say, >10,000 units. These devices could last for 10+ years on a single battery while sending meter readings once per day at a network operating cost of <$15 per device per year. When compared to the cost to a utility of manually reading meters every 3 months with human labour, Sigfox can be significantly lower cost while delivering significantly more detailed data. This additional data is highly valuable for gaining insights into customer behaviour and utility network operations. Add to this that the cost to the user to deploy the wireless network is typically $0.
It is our intention to help those interested in smart metering to understand new technology and to enable improved products and services. We are not bias towards Sigfox. We are advocates for a range of wireless communication technologies and providers (see previous article here). Our interest is in helping people to improve water efficiency and improving smart metering technology.
There are other technologies available with many of the benefits of Sigfox, and some that offer advantages that Sigfox does not. This article is focused only on Sigfox. We will be sharing detailed content about other technologies in the near future.
IoT technologies such as Sigfox are opening new opportunities and enabling new uses for smart metering. It has never been easier to get started.
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