Low-Power Wide-Area Network
Low-Power Wide-Area Network (LPWAN) is a type of wireless telecommunication wide area network designed to allow long range communications at a low bit rate among connected objects, such as sensors operated on battery.
On one end of the spectrum are cellular standards (3G, 4G) that offer good range and good data rates but also consume lot of power. On the other end are short-range technologies such as Wi-Fi and Bluetooth that consume less power but are limited by range. LPWAN fills the gap in between where a longer range is desired at lower power for sending small amounts of data.
What's the big picture of LPWAN in IoT?
LPWAN is a key driver for Internet-of-Things (IoT) innovation. LPWAN helps connect far-flung sensors and other devices. LPWAN technologies optimize battery life by decreasing power consumption, while networking standards ensure reliable connections at low speeds to support low levels of data use. Thus, LPWAN enables energy-efficient transmission of small data volumes over long distances.
Where does LPWAN fit?
The low power, low bit rate and intended use distinguish LPWAN from a wide area network that is designed to carry more data using more power. LPWAN data rate ranges from 0.3 kbit/s to 50 kbit/s per channel. Cellular networks based on GPRS used to offer this connectivity for carrying M2M data back since the late 1990s. However, operators across the world are shutting down their legacy 2G networks. For example, AT&T announced that its 2G network will be completely shutdown by end of 2016. It's in this context that new LPWAN technologies were invented and sometimes standardized.
- Cellular (e.g. NB-IoT and LTE Category M1) WANs using licensed spectrum.
- Wireless WANs operating in unlicensed frequency bands(e.g. LoRaWan and Sigfox).
What are the different types of LPWAN and how do they compare?
The comparison between any of the LPWANs available is based primarily on coverage, bandwidth, data rate, and number of messages per day. Selecting the right LPWAN is application dependant but typically the goal is to obtain decent rates at minimum power consumption.
- LoRa: Unlicensed sub-GHz spectrum. Chirp Spread Spectrum (CSS) modulation. Can define packet size. Transceiver chip is available only from Semtech Corporation. LoRaWAN the Medium Access Control (MAC) layer for managing communication between LPWAN devices and gateways.
- Sigfox: Proprietary. Unlicensed 868 MHz or 902 MHz bands with only a single operator per country. Coverage of 30-50 km (rural), 3-10 km (urban) and up to 1,000 km (line-of-site). Uplink 150 messages of 12 bytes per day. Downlink 4 messages of 8 bytes per day.
- NB-IoT: Licensed bands including unused 200 kHz bands previously used for GSM or CDMA. Based on LTE resource blocks.
What are the application areas or use cases of LPWAN?
LPWANs are deployed globally in many countries, some even nationwide, to enable services in the Smart metering, Facilities and Logistics management, Wearables, Smart dustbins, Smart street lighting, Industries with connected appliances, Environmental monitoring, and more.
Deployments noted above include both kind of licensed LPWANs (NB-IoT) and unlicensed LPWANs (LoRaWAN, Sigfox). The choice is based on requirement and availability.
How do I select a suitable LPWAN for my application?
Selecting a LPWAN involves understanding and refining the key characteristics and requirements of the IoT application and a particular use case. The following parameters can be considered: Battery life, Capacity, Range, Cost, Licensed/Unlicensed spectrum, Quality of Service, Reliability, and Security.
What LPWAN products are available for prototyping or deployment?
Microchip Technology Inc. have developed its RN2483 LoRa® module, the world’s first to pass the LoRa Alliance’s LoRaWAN™ Certification Program. Some of the operations performed on RN2483 transceiver include:
- radio get bt - reads back current data
- radio get mod - current mode of modulation - LoRa, FSK
- radio get fr - reads back current frequency of transceiver
- radio get power - reads back the current transmit output power
For Cellular LPWANs there are various chip-set vendors available such as Alter Semiconductors, Huawei, Mediatek, etc.
What's that status of LPWAN standardization and interoperability?
3GPP governs and provides specification for the cellular IoT alternates as NB-IoT and LTE-M.
IEEE 802.15.4 is a technical standard which defines the operation of low-power wireless personal area networks (LP-WPANs). It specifies the physical layer and media access control for LP-WPANs, and is maintained by the IEEE 802.15 working group, which defined the standard in 2003. It is the basis for the ZigBee, ISA100.11a, WirelessHART, MiWi, SNAP, and Thread specifications, each of which further extends the standard by developing the upper layers that are not defined in IEEE 802.15.4. Alternatively, it can be used with 6LoWPAN, the technology used to deliver the IPv6 version of the Internet Protocol (IP) over WPANs, to define the upper layers.
Is there anything in place to test and certify LPWAN products?
A new study item titled "Cellular System Support for Ultra Low Complexity and Low Throughput Internet of Things" is proposed in 3GPP. This kick-starts the work on NB-IoT. The document states that 3GPP M2M devices use legacy GPRS but there are competing technologies that provide better coverage and efficiency at lower cost. Document proposes looking into evolving GERAN plus designing a new access system.
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