Harnessing the Power of a Global IoT Network
Low Power Wide Area Networks (LPWANs) emerged recently to describe a particular class of wireless networking technology, positioned specifically for remote endpoints in the Internet of Things (IoT). They combine three key features: low power, long range and low bandwidth, all of which are relative, of course. With so many wireless technologies vying for design wins in the IoT, it should come as no surprise that those within the LPWAN space are also in competition, but as with most decision processes, understanding the nuances of each technology will enable engineers to choose the one that is right for their application.
Deciding to use an LPWAN rather than a Personal Area Network (PAN) technology should be relatively simple; most PANs use a Mesh technology with a local access point, while LPWANs typically employ a Star network without the need for a local access point. If range is important then an LPWAN is probably favourable because, while LPWANs can operate over short hops, it is really the need for distances in excess of 10km that would dictate the use of an LPWAN. In short, if you can’t see the network access point, or even know where it is, you probably want to use an LPWAN.
Another feature of an LPWAN is that you only need a single node to become part of a global network. This is similar, in concept, to the way cellular networks interoperate around the world, and Release 13 of the 3GPP specification does facilitate LPWAN functionality.
Assessing the amount of data that needs to be transmitted or received is the next step. Analysts estimate that nearly 90% of all IoT endpoints require less than 3Mbyte of data per month, while the vast majority of those using LPWANs will use 150kbyte or less per month. This really plays to the strengths of LPWANs, which were conceived with this user profile in mind. It also differentiates LPWANs from other solutions, including those defined by the 3GPP.
Global solution
Sigfox is a solution for a LPWAN today. It is based on a proprietary technology that operates in the unlicensed bands available around 868MHz and 902MHz, dependent on the operating region. Sigfox runs an open licence-free ecosystem with more than 300 partners around the world. It has similarities with cellular networks in that the network management is handled entirely by Sigfox Operators (one per country), who deploy base stations in their own region to handle the interface and backend connectivity to the Internet. Customers access LPWANs by adding the RF interface to their device, typically using either a chipset or a module, at which point it becomes part of the IoT, with access to all the benefits that implies.
LPWANs can support connections across distances as great as 1000km in line-of-site installations, up to 50km in rural environments, and as far as 10km in urban areas. This is farther than any PAN can offer and even rivals cellular, but it comes with the added benefit of having extremely low power demands during operation.
In the case of Sigfox, the uplink is designed for typical IoT smart endpoint activity, offering 140 messages per day, each of 12 bytes data payload. The network also supports downlinks for communicating back to endpoints, providing four messages per day of 8 bytes data payload each.
It may not sound like a lot, but this is a network optimised for low power operation over city-wide distances, sustaining continued connectivity for many years from a single primary cell. In terms of the IoT, Sigfox encapsulates the needs of the majority of applications without imposing costly demands that could become prohibitive in some cases. Each LPWAN provides an optimised mix of bandwidth, speed and downlink payload, and they generally do this by varying power, range, or the total cost of ownership. It’s these subtle differences between possible solutions that need to be evaluated at the design stage, and an area where Avnet has particular expertise.
Wisol also offers the WSSFM20R1, 2 and 4 modules (Fig 2), which are regional variants that integrate Sigfox, BLE, WiFi and GPS in a single device. The Korean manufacturer has also developed the world’s only dual-zone module: the WSSFM11R2DAT, which can operate in both RC2 and RC4. AT commands are used to change zones, and it also integrates an MCU with a UART interface in a module measuring just 13.0mm x 20.0mm x 2.21mm. Wisol is also developing additional product families that will integrate different combinations of these features for more optimised solutions.
Wisol also offers the WSSFM20R1, 2 and 4 modules (Fig 2), which are regional variants that integrate Sigfox, BLE, WiFi and GPS in a single device. The Korean manufacturer has also developed the world’s only dual-zone module: the WSSFM11R2DAT, which can operate in both RC2 and RC4. AT commands are used to change zones, and it also integrates an MCU with a UART interface in a module measuring just 13.0mm x 20.0mm x 2.21mm. Wisol is also developing additional product families that will integrate different combinations of these features for more optimised solutions.
The TD1207R/08R (Fig 1), for example, offers a range of GPIO along with analogue interfaces, high-speed ADC and DAC functionality coupled with UART, PWM and I2C ports. Operating in the 868MHz range, it offers a maximum link budget of 148dB and consumes just 5mA when transmitting at an output power of +16dBm. The FCC Certified TD1508 offers similar functionality, but operates in the 902-928MHz range and has a maximum output power of +25dBm. The TD1204 adds geolocation functionality through the integration of a GPS receiver, which makes it ideal for vehicle and object tracking applications, while the TD1205P goes a step further by integrating the antennas for both Sigfox and GPS.
Easy access
Implementing an LPWAN is much simpler than using other forms of RF communication, since the majority of design effort has already been carried out by the providers of the modules or chipsets. In general, using a Sigfox VerifiedTM certified module or reference design is the fastest way to connect to its network, and provides the optimal business case for low to medium volume needs.
Avnet has been working with TD next to help develop its range of Sigfox Verifed™ certified modules, which integrate radio transceivers with powerful embedded processors to give devices the ability to collect, process and send data to the Internet through the Sigfox LPWAN.
The TD1207R/08R (Fig 1), for example, offers a range of GPIO along with analogue interfaces, high-speed ADC and DAC functionality coupled with UART, PWM and I2C ports. Operating in the 868MHz range, it offers a maximum link budget of 148dB and consumes just 5mA when transmitting at an output power of +16dBm. The FCC Certified TD1508 offers similar functionality, but operates in the 902-928MHz range and has a maximum output power of +25dBm. The TD1204 adds geolocation functionality through the integration of a GPS receiver, which makes it ideal for vehicle and object tracking applications, while the TD1205P goes a step further by integrating the antennas for both Sigfox and GPS.
Wisol is another company offering connectivity modules for the Sigfox and LoRa LPWANs, LTE networks and PANs including Bluetooth, WiFi, ZigBee and Z-wave. As an example, Wisol has developed the WSLWSSFM10R1/2/3/4 modules covering all of Sigfox’s regional radio configurations: RC 1, 2, 3 and 4 respectively (where RC1 operates at 868MHz and covers Europe and the Middle East; RC2 operates at 902MHz and covers North America; RC3 operates at 923MHz and covers Japan; and RC4 operates at 920MHz and covers South America, Australia, New Zealand and parts of Asia). 
Wisol also offers the WSSFM20R1, 2 and 4 modules (Fig 2), which are regional variants that integrate Sigfox, BLE, WiFi and GPS in a single device. The Korean manufacturer has also developed the world’s only dual-zone module: the WSSFM11R2DAT, which can operate in both RC2 and RC4. AT commands are used to change zones, and it also integrates an MCU with a UART interface in a module measuring just 13.0mm x 20.0mm x 2.21mm. Wisol is also developing additional product families that will integrate different combinations of these features for more optimised solutions.
Modules that combine two or more wireless technologies provide significant benefits in the IoT. InnoComm also offers a range of 3G/4G, Pan and Sigfox modules, with some that combine Sigfox with Bluetooth, WiFi and GPS. For example, the SN10-2x family integrates Sigfox, BLE, WiFi and GPS, and is available for RC1, RC2 and RC3. Similarly, the SN10-3x (Sigfox + BLE + WiFi), SN10-4x (Sigfox + WiFi), SN10-5x (Sigfox + BLE) and SN10-6x (Sigfox + GPS) are all optimised for applications that need to provide two or more wireless features and are available for all three zones.
The majority of LPWAN modules available are based on chipsets developed by leading semiconductor manufacturers including Microchip, NXP, ON Semiconductor, STMicroelectronics and Texas Instruments, all of which are available from and supported by Avnet, and provide a roadmap to a custom implementation for very high volumes and further cost-optimisation. Radio solution design based on chipsets rather than modules will need to be independently certified, but for volumes higher than 50k per year, this can provide a cost advantage.
IoT development made simple
The Visible Things edge-to-enterprise reference design developed by Avnet provides all of the hardware and software building blocks needed to develop an IoT application (Fig 3). All of the smart sensors in the Visible Things platform are designed to interface with the Visible Things Gateway, which in turn connects to a cloud service. The software provided allows smart sensors to be ‘seen’ through any Internet browser, giving developers easier access to the power of the IoT.
As well as the Visible Things platform, getting started with LPWANs is aided by the availability of a range of development platforms. This includes the EVBSFM10Rx evaluation board from Wisol, which can be supplied with any of the regional SFM10Rx modules. InnoComm also offers an evaluation kit for its modules. /p>
The easiest way to get started with the TD next module is to use the TD120x EVB, which supports the TD1204, TDR1207R, TD1208R and TD1508 modules and uses the standard ARM SWD debug interface for device programming and debugging. It can be powered either via a USB interface to the host computer or by a dedicated power supply, and it also offers the ability to measure the current consumption of the module. The TD1204 EVB supports the TD1204 and TD1205P modules, which include geolocation features, and can also be programmed and debugged over the ARM SWD interface.
Conclusion
As LPWANs start to bring connectivity to more disparate devices over wider areas, it becomes apparent that not all LPWANs are the same. Some, like Sigfox (www.sigfox.com), can offer a single subscription model, meaning assets can be tracked and monitored wherever they are in the world through one simple interface. As partners maintain the network and all its base stations, subscribers aren’t encumbered with the cost and inconvenience of managing the wider network beyond their own endpoint. This makes getting anything connected to the IoT a ‘plug & play’ process.
The availability of low cost, low power LPWAN modules, development and evaluation boards and the Visible Things platform makes LPWANs even simpler, giving developers easy access to the power of global connectivity.
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