Ultra Narrow Band (UNB) is usually referred to technology transmitting over very narrow spectrum channel, i.e. <1KHz, to achieve ultra-long distance link (5 km in urban or 25km+ in suburb area) for data link between transmitter and receiver. This makes theoretical sense because of excellent link budget from low in-band receive noise (narrow receive filters remove most of the noise). An alternative is to use wideband, high-data-rate communication and add coding gain (such as CSS in LORA). Yet given the same net data throughput, both systems will have similar range.


It is noted that trading higher receive sensitivity for less spectrum efficiency (higher bandwidth) by spread spectrum goes against regulatory requirements and worldwide industry practice on spectrum utilization. As an example, narrowbanding to 12.5 kHz was a well-established solution to increasing spectrum efficiency in FCC and CE. This proves the UNB validity in the limited spectrum of unlicensed sub-GHz band in IoT use cases. Nevertheless, the challenge of an UNB system has traditionally been the higher RF crystal requirements: if the frequency offset gets too big, the signal will fall outside the channel, thus filtered out by the receive filters. Use of high-stability crystal such as TCXO can significantly increase the device cost and maintenance hassles.


This complication is greatly relaxed by today’s digital signal processing at Base Station. The system can assume the transmitter device is not all that accurate. The Base Station scans either side of the expected frequency and moves its reception. So long as remote transmitter has knowledge of drift its process, the Base Station can tell it where it has drifted, and the system can adapt the parameters to recover the loss. Similar ideas are present in both Weightless-N standard (now ETSI LTN) as open standard and SIGFOX networking as proprietary technology.


By transmitting through an UNB channel – i.e. 200Hz wide in SIGFOX signaling, little power is required to transmit data over considerable distances with low air data date. UNB systems are frequently used in one-way, from a sensor (Terminal Device) to a Base Station, but two-way services may be required from time to time. For example, a sensor in a car park that tells if a particular space is empty only has to transmit once when a car enters the space, and once again when a car leaves – and optionally open its receiver a few times each hour to listen for system commands. To keep power-hungry work confined to the mains-powered base station, it will almost certainly be asymmetric. With transmission of 50mW from the battery-powered UNB remote node, with classical filters and digital filters controlling transmit bandwidth, it will be up to the Base Station to find this narrow signal amongst unwanted RF.

Ultra-Narrow-Band Communication among wide-band interference

Ultra-Narrow-Band Communication among wide-band interference

SIGFOX is relatively unique in this market space, as both technology driver and service provider, by offering the modem certification so that the SIGFOX-compatible device can be subscribed to the network solely run by SIGFOX Network Operator (SNO). This is similar to the Telecom operator in the cellular business except only focusing on CONNECTED OBJECTS. Their benefit is the commercially available chipset enabled to accelerate the market growth and early technology adoption. SIGFOX service is currently available in 26 countries worldwide in 2016.

With billion IoT devices projected in the near feature, device cost and the form factors are crucial for the Terminal Devices. M2COMM offers the competitive System-on-chip (SoC), integrating both RF front end 32-bit microprocessor, for device makers to effectively develop the UNB modem and sub-system such as SIGFOX signaling. For details please refer to Portfolio about SoC or Module offers.

As a final note, Weightless-P open standard, proposed by M2COMM in 2015, is somewhere between UNB and NB (Narrow-band), utilizing Narrow Band modulation scheme with bandwidth up to 10KHz, for interactive links with synchronization and improved spectrum efficiency. As a result, Weightless-P may offer a bidirectional communications capability to enable unrivalled quality of service (QoS) and add on functionality. It will provide fully acknowledged 2-way communications offering both uplink and downlink capabilities and best-in-class QoS required for the stringent industrial IoT sector. Weightless-P equipment is now under development by other Weightless Alliance partners.

IoT defragmentation with viable solutions is crucial for the continued momentum of the LPWAN market place. M2COMM enthusiastically supports the collaboration among versatile technologies to power charge this new territories, bringing new scope to the IoT connectivity.

To contribute to Low-power Wide Area Network (LPWAN) democratization and establishment of open standard in this space, M2COMM has honorably initiated the Weightless-P development from 2015 and became the Weightless SIG board member since then. We cordially support this technology and our partners to bring this exceptional work from early development to the next level of advancement.

Dr. Derrick C. Wei, CEO, M2COMM, Dr. William Webb, CEO, Weightless Alliance

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