by MARTHA ZEMEDE, Keysight Technologies
Test instruments help ensure connections to the cloud coexist peacefully with IoT communication schemes.
People once thought that a “thing” on the “Internet of Things” was an item that could be counted—RFID tags on shipping containers, for example, or parking lot exit-and-entry systems that know when the lot is full. Today, an IoT “thing” can be any natural or man-made entity, fixed or mobile, able to transfer data over a network. A common healthcare example is the remote monitoring of a patient’s condition away from a clinic or hospital. Another is a vehicle involved in a traffic accident that not only summons emergency assistance, but also reports its location, the number of occupants and the severity of their injuries.
It’s likely that a majority of IoT things will rely on some kind of wireless communication technology. There are myriad wireless schemes. They range from near-field communication (NFC) for mobile payments, to geosynchronous satellites for unattended remote weather stations, and everything in between: Bluetooth, wireless LAN (WLAN), cellular, ZigBee, point-to-point radio and more.
These wireless points will connect to the cloud through IoT Gateways. Gateways are the link between end devices and the cloud. In many instances, there is no direct connection between the thing and the cloud, or the remote application that needs to communicate with it. Rather than connect directly to the Internet, each device will use one or more standards to connect to a higher level gateway that is responsible for protocol and operation of the individual device with the cloud.
There is no such thing as an IoT communication standard, so networks will need to cope with numerous devices having different communication requirements. At one end will be simple wireless devices such as battery-powered sensors and actuators that will transmit little data while operating unattended for several years. At the other end—literally and figuratively—will be high-bandwidth, mission-critical services and devices such as autonomous cars demanding constant, reliable and super-secure connections.
In most cases there’s no direct connection between the thing, the cloud or the remote application. Instead, they will connect through a gateway. For one example, consider an apartment complex equipped with a network of ZigBee-based fire-detection and entry sensors: Data is compiled and stored in a local ADSL intelligent gateway that periodically reports to a security company. The gateway would be programmed to immediately raise an alarm when the system detects an abnormal sensor response. Gateways make data flow seamlessly and securely from sensors and other edge devices to the cloud. In general, a gateway is responsible for translating between protocols and the interoperation of individual devices, the app and the cloud.
While cellular and WiFi are quite common wireless standards, emerging low-power wide-area networks (LPWAN), such as Sigfox, LoRa and PLANet, are relatively new standards optimized for IoT/M2M communication. Unlike traditional cellular networks, LPWANs are optimized for low data rates, long battery life, low duty cycle, and the ability to coexist in a shared spectrum using unlicensed ISM bands. An example is in city street lamp lighting systems, which tend to be in place for decades, far longer than typical cellular standards are in force.
Here are some brief descriptions of these emerging LPWANs.
Sigfox is a French firm that builds wireless networks handling low data rate IoT and M2M applications. Its cellular-style network uses a patented radio technology based on ultra-narrow band (UNB) technology. The throughput is characterized by up to 140 messages per object per day, with a payload size of 12 bytes per message, and wireless throughput of up to 100 b/sec. Sigfox said each base station can handle up to a million connected objects, but the network is scalable to handle more objects. The density of the cells is based on an average range of about 30 to 50 km in rural areas and 3 to 10 km in cities. Distances can be much higher for outdoor objects where messages in line-of-sight can travel over 1,000 km.
A LoRaWAN (Long Range Wide-area Network) is a LPWAN specification targeting low-cost, low-power, mobile, bi-directional communications for IoT, M2M, smart city and industrial applications. It uses a spread spectrum modulation scheme derived from Chirp Spread Spectrum (CSS) modulation. This technology is standardized by a group of companies in the LoRa Alliance and defines several classes of end-point devices to address wide range of applications.
The PLANet communication scheme is from a UK firm called Telensa. Like Sigfox, it uses UNB wireless technology. PLANet was originally designed for controlling networks of street lights. It has also been used in a wireless parking space monitoring system called PARKet, which detects cars, monitors parking space availability and delivers real-time information to drivers about where to find a parking space.
A typical PLANet base station consists of a radio, antenna and sensor. Each base station has a range of several miles and communicates with Telecell devices installed at each monitored point. (In the case of lighting systems, a luminaire. For parking systems, a parking spot.) A central server manages connections with Telecell units through base stations.
Of course, the cellular standards bodies are not standing still. The 3GPP (3rd Generation Partnership Project) has been working toward support for IoT and machine-type communication (MTC). Release 12 of the standard (March 2015) added an MTC extension to LTE-Advanced, defining a new device category called Category-0 or Cat-0. Significant optimization of Cat-0 MTC is planned for Release 13 (March 2016), targeting lower-cost, lower-complexity devices with reduced transmission power, ultra-long battery life and extended-coverage operation.
Looking for even better link budget, cost and power consumption than available with LTE-MTC (Cat-0), the GSM (Global System for Mobile Communications) EDGE (Enhanced Data rates for GSM Evolution) Radio Access Network (GERAN) groups are proposing two strands for what’s called cellular IoT (CIoT). One is based on an evolution of GSM and the other uses clean-slate radio access technologies aimed at low-end IoT applications.
Technologies versus range
When it comes to the communication technologies being proposed for IoT, there is no firm definition of the boundaries of WPAN, WLAN, WNAN and WWAN. To facilitate future development, standards are quickly forming and evolving as new devices become connected. Currently, there are more than 60 legacy and new RF formats in use for M2M and IoT-related applications.
The multitude of these RF formats came about because some companies have developed proprietary communication schemes out of expediency: They have been relatively easy to create because they generally work at low data rates, their transmissions consume little power, and there are minimal interoperability requirements. This approach is likely to fall out of favor because the globalization of markets is pushing designs toward use of standardized methods.
Gateways will increasingly use standard interfaces to devices and to the cloud, but the amount of intelligence they’ll need will depend on specific applications. One key to rapid deployment of custom gateways is the availability of test gear flexible enough to meet the needs of engineers across R&D, manufacturing and deployment. To understand this flexibility in this context, consider an example: Early in product development, engineers can run simulations that include virtual measurement tools. These can attach to nodes in the simulation, providing realistic views of how the product will perform. As the design moves from simulation to reality, physical device modules can be substituted into the simulation, and real measurements replace their virtual simulations.
Once prototypes are available, engineers can make use of lab-grade test equipment, which generally has built-in measurement applications that can show whether the prototype performs to standards. For custom gateway products, engineers can do pre-qualification testing for each supported format to verify the product will meet the relevant specifications, including interoperability with other communication standards.
Sigfox white paper
Telensa PLANet system