It is easy to forget how many mobile users in the world do not have full web access on their handsets but are still using featurephones. That has ensured a long survival for the unglamorous workhorse of GSM technologies, the USSD (Unstructured Supplementary Service Data) protocol, which allows basic web services to be accessed from featurephones. Having enjoyed a revival based on mobile money services for the unbanked, there is now new potential for USSD, to deliver IoT services over 2G networks in emerging economies.
USSD has been supported by some companies, such as Myriad Technologies, which have been heavily focused on emerging economies. Myriad’s subsidiary, Thingstream, is now pushing into the IoT.
The GSM protocol has also caught the attention of Facebook in the past few years as the social media giant has sought to bring its services to the unconnected or the poorly connected worldwide. The company made a deal in 2011 with India-based U2opia Mobile to use the latter’s USSD connectivity platform to open up its apps to users with low end devices or connections. Bharti Airtel in India and Telenor in its Malaysian and Indian operations are among the operators which have offered this Facebook USSD service, and the 2G technology also underpins many mobile money services aimed at the unbanked of Africa and Asia.
While mobile money has been the single biggest factor in keeping USSD at the forefront of carriers’ minds in emerging markets, interest will grow even higher as the protocol becomes a low cost way to support some Internet of Things applications for those with featurephones. For instance, Thingstream – a subsidiary of Myriad – has unveiled a USSD-based IoT messaging service, based on SIM cards supplied by the company, which promises low-power messaging for any device inside a GSM network footprint.
Myriad, a Swiss provider of USSD gateways, has been a major developer of USSD-based services, offering email, location and social services to emerging economies. It set up Thingstream two years ago to target the potential for IoT services, aware that most cellular-connected machine-to-machine applications still run on GSM and require little more than reliable, ultra-low power messaging.
The new Thingstream system will launch in late 2017 or early 2018. With around 23 staff on the project, mostly developers, progress appears to have been swift – with pilot customers including pet tracking systems and oil-well monitoring services.
Thingstream VP Neil Hamilton explained the core of the offering, and argued the merits of USSD. He said that its biggest benefit is the pre-existing coverage of GSM. While there are still gaps in some rural areas in 2G coverage, the older protocol enjoys a far greater footprint than 3G or 4G – meaning that USSD is an option for any devices that can reach a 2G tower.
The USSD approach means that a device using a Thingstream SIM card can wake up from sleep, quickly connect to the strongest available GSM signal, whether that’s 2G, 3G, or LTE, and send a message to the network using a two-way secure socket with the network server within a single session – meaning that the message isn’t stored in the network, like an SMS message would be.
The lack of the store-and-forward system should allow for more secure messaging, since there are fewer chances for the message to be intercepted as it travels through the network. In addition, because the device is relying only on USSD, it doesn’t require a data connection to the network, meaning this would work over a voice-only network – which is a great benefit for rural coverage. The network operators also benefit from not having to add SMS infrastructure to support the system, and of course, Myriad can supply them with USSD gateways (appliances or virtualized).
As for power consumption, Hamilton says that it uses less power than sending data-packets on those cellular networks. The deployed battery life will depend on radio usage, and Hamilton notes that a Thingstream testing device that resembles the Amazon Dash button can manage a year’s operation on an 1,800mAh battery with hourly sends. That performance can be significantly stretched with a larger battery or fewer sends, but the likes of Sigfox and LoRa might be a better choice for developers where battery-life is a top requirement, provided unlicensed spectrum – with its potential QoS issues – is acceptable.
USSD is baked into the Signaling System Number 7 (SS7) standards, and will be most familiar to users of pay-as-you-go phones, who remember typing in short codes to their keypads to receive balance or package usage updates. That same mechanism is being used by Thingstream to send secure messages over GSM networks, in real time two-way sessions that can push data from the networks to the devices too – something that many of the upstream-focused LPWAN approaches don’t prioritize.
The messages themselves can be 182 alphanumeric characters, which provides enough information to support some fairly advanced services, often focused on banking and ecommerce. Hamilton noted that Myriad supports a Facebook application using USSD, and that larger payloads, such as telemetry data, that exceed the single-message capacity, can be spread across multiple sessions.
Once the secure tunnel with the MNO’s network is created, USSD allows the end device to fire off its payload. Thingstream supports MQTT-SN, which allows the devices to more easily communicate with IoT applications that support the commonplace industrial-focused MQTT protocol, which also enables different QoS functions natively.
While USSD appears very applicable to IoT applications, Thingstream’s global coverage agreements are the key to its platform. The company is offering a SIM card that allows connections to over 600 operators, as well as its small software developers’ kit, which the end devices require in order to use the feature.
Thingstream envisions this costing around $1 per device per month, with Hamilton noting that the security of the connection means that it can offer a service for which customers would gladly pay more. In this early stage of the wider IoT, the high value applications often have larger budgets for their connectivity, but as time progresses and volumes increase, the connectivity costs globally will be squeezed – as different business uses/applications embrace the IoT.
Currently, about 80% of the connections managed by Thingstream occur on 2G networks, with almost all of the others on LTE. Hamilton thinks that the ratio is probably going to remain pretty similar when the service launches in full, but that it could shift down the road. He noted that industrial asset tracking is a core market, especially for developers looking for an almost disposable unit for monitoring high value assets – where a $50 hardware cost is but a fraction of the asset cost or the cost of an outage. Agriculture and environmental monitoring are expected to be high growth areas.
The next step for Thingstream is the creation of a flow builder, for designing and managing applications that ingest and send USSD messages. Based on IBM’s open source Node.Red, a drag-and-drop tool for designing the workflow of an application, the tool should make it easier for developers to test and deploy their own systems.
When asked about the security features of USSD, Hamilton noted that the system doesn’t use IP addresses that can be exposed to attack, as each USSD session closes after the message is conveyed – unlike a static IP address, which could be found through web-trawling, and constantly targeted. Encrypted payloads are the norm, and trying to intercept a message in the air would be something only capable with nation state resources – a not something that a criminal hacker would be able to accomplish.