ENGINEERS' INSIGHT

Designing for LoRaWAN - Murata Wireless Modules

As one of the world’s leading manufacturers of wireless modules for smartphones, including supplying some of the very biggest names in the market, Murata knows about wireless technologies, and also about manufacturing modules. The company’s new LoRa connectivity module is expected to be received as a significant development for IoT (Internet of Things) markets: one that really opens up new possibilities for companies developing products and technologies for LoRaWAN based networks. Designed to reduce both costs and energy use, LoRaWAN is a low-power wide-area network (LPWAN) with an open specification standardised by the LoRa Alliance. The Alliance includes a host of different companies, many of them multi-nationals, including telecom companies, system integrators and equipment manufacturers, as well as many leading semiconductor and sensor vendors, among many others.

Today we are seeing major ongoing installations of infrastructure for LoRaWAN networks, primarily in Europe, but also in other parts of the world. The network is designed to enable a wide range of applications in areas such as public transportation, smart metering, wearables, livestock and asset tracking, and M2M communications and sensor-based end nodes in IoT networks.

LoRaWAN hits the sweet spot between the cellular/LTE based technologies and the short-range very-high-throughput capabilities of Wi-Fi and Bluetooth, but most importantly delivers on the low-power and small-packet data requirements of many IoT applications. Implementing ultra-narrow-band technology and minimising energy consumption in battery-powered devices, and in the network itself, LoRaWAN is ideal for ‘smart city applications’. For example, it can support the primary data transport infrastructure for the sending of collected measurements from remotely located environmental monitoring devices. In the coming years, an alternative network for these types of applications is the new 3GPP NB-IoT technology, but it is still very early days for the standard, while LoRaWAN is already well established.

This brings us to Murata’s LoRa wireless module and why the module approach can bring a number of benefits for developers in this field. Highly integrated and measuring only 12.5 x 11.6 x 1.76mm in a metal-shielded LGA package, the CMWX1ZZABZ-078 is a stand-alone low-power device that is one of the world’s smallest solutions for adding LoRa-based wireless connectivity to a range of products and applications for the IoT and Machine-to-Machine (M2M) communications. The module integrates the Semtech SX1276 RF transceiver together with a low-power microcontroller, the STM32L Cortex M0+ based MCU from STMicroelectronics. An integrated TCXO crystal oscillator has robust low-drift thermal characteristics and delivers an accurate clock source for the RF transceiver. The integration of the MCU means, depending on the application, an external microcontroller is not necessarily required for the system, which can deliver a high level of design flexibility. The STM32L has 192-kbytes flash memory and 20-kbytes RAM, which should provide enough memory for most applications or the ability to host other modulation protocol stacks.

Block diagram for Murata's new LoRa module

Another important point is that the use of modules can simplify compliance testing. The Murata module has pre-certified radio regulatory approvals for operating in the 868 and 915MHz ISM spectrum. So, in addition to getting a pre-certified and pre-tested module, it is also suitable for integration in end products that can be deployed in most geographical regions of the world, thereby negating the need for separate solutions for each particular region. The module delivers a range of up to 15km in non-urban environments based on a normal output power of +14dBm, which can be further boosted by a power amplifier boost function to increase RF output to + 20dBm for longer range applications. Other specifications include UART, SPI or I2C peripheral interfaces and integration of an ADC and up to 18 GPIOs, providing flexibility for connecting sensors, switches and status LEDs.

The use of this module brings a number of other benefits: it essentially means that high levels of RF expertise, as well as detailed knowledge of LoRaWAN, are not necessarily required. Clearly this can have an effect on the size and capabilities of the team required to deliver the design. Buying in the connectivity subsystem should also mean fewer design iterations and allow the team to concentrate on the overall system design, potentially shortening time to market. In addition, basic standalone applications can be developed, simply by adding a sensor or combination of sensors, a battery or alternative energy solution, and an external antenna. The device is also available with an optional STSAFE secure element to enhance network security.

Essentially, Murata’s expertise in wireless is bought in, which can make a great deal of sense compared to high cost of developing dedicated discrete solutions that may also take up more board space. The use of a single module over the discrete approach can mean a smaller BoM and reduced operational costs, as well as a reduction in cost for board assembly.

Engineering samples of the CMWX1ZZABZ-078 with preliminary datasheet are available now – click the button below to request; mass production will commence at the end of November 2016. 

WRITTEN BY

Martin Keenan

As Technical Manager, Martin is responsible for marketing strategy across IP&E, power and battery products into key market segments. Martin has over 15 years' experience in electronics having begun his career at Nortel Networks, and since occupied roles at RS Components, Avnet and Altera.

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