Friday, November 21, 2014

LoRa - the modem killer?

Internet of Things is at the top Gartner's hype curve of the year. But how to get the Things into the Internet? - That is the question.

When designing a IoT system, device connectivity is often among the biggest headaches. In case of consumer products, it is usually possible to rely on existing infrastructure, either Wifi Access point or Bluetooth/Smart connectivity of mobile phone. When considering city-wide installation of wireless sensors network or intending to cover a whole industrial plant, those consumer technologies are simply not feasible.

In practice, individual sensors are Today often having a cellular data modem with them, which is totally overkill. Reading a single sensor value every now and then does not need the bandwidth which is good for streaming video. Modem by itself as a component is usually more expensive than rest of the sensor electronics, and it ruins your power budget. Finally but not least, management of SIM subscriptions in global context is a nightmare.

Why there are so many cellular data modems then? Because there has been no other real options available. Low power 2.4 GHz radios like 802.15.4 can only do about 100 meters in open space. Wifi can be extended to some 500 meters, but then power consumption is over battery budget.

Sub-GHz radios can address the range issues. Narrowband RF like in TI portfolio are proven to have good performance in distance. A interesting new alternative is Semtech Lora.

Freescale FRDM-KL25Z Cortex-M0 evalution board with
ARM mbed-supported LoRa Shield from Semtech.
LoRA is a long range sub-GHz spread spectrum radio technology from Semtech. LoRa uses proprietary chirp spread spectrum  (CSS) modulation, which is rather unusual solution for data communication. CSS is more commonly known in radars and that sort of applications. In sensor node communication, added value of CSS is rather good distance measurement, which is far more accurate than traditional RSSI estimation.

BOM cost of Sub-GHz RF subsystem is less than 5€, which fits into the price range of most IoT sensors. However, having the radio in the sensor node only is not good enough. Also infrastructure is needed. In building-wide installations one can assume a gateway or two to be easily installed and maintained. In case of metropolitan area network the situation is different. Some one must build and operate the network infrastructure.

There are some indications that traditional telecom operators may be interested in introducing IoT networks. It may be considered as direct competitor with existing M2M cellular data business, which may hinder operators interest. However, if operators don't do that by themselves, some one else will do it, and then operators are only loosing.

FastNet in South Africa is the first public reference of a telecom operator investing in LoRa-infrastructure to provide IoT communication services. However, the playground is not reserved for traditional operators only, but new players like energy or transportation companies may invest into network infrastructure of their own and start selling capacity to other players as well.

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