Smart city low power wide area (LPWA) is expected to achieve over 140 million connections. According to analyst ON World, there could be as many as 2.6 billion connected, wireless IoT devices for smart cities, with LPWA suitable for 60% of those connections.

The IoT relies on data, and lots of it, as sensors gather and send data from around a network. There are many ways to enable this. Bluetooth Low Energy, ZigBee, Wi‑Fi and cellular technologies are all established, but LPWA networking technologies, such as Sigfox, LoRa, LTE-M and NB-IoT are emerging as IoT disruptors.

These are low power and able to connect millions of devices across kilometres of cloud-connected networks. They are increasingly used outdoors in parking, utilities, pollution monitoring and other applications that require wireless communication via always-on nodes in a network.

“Different wireless protocols have different benefits, but where the use case is moving sensor data or small amounts of data, LoRa is designed specifically for that,” says Dave Armour, strategic marketing manager for wireless products at Semtech. The company licenses the proprietary LoRa technology and is a founder member of the LoRa Alliance.

Characteristics of LoRa are “very long range and exceptionally low power consumption,” says Armour.

LoRa technology

LoRa is based on a transceiver design and uses an unlicensed spectrum, allowing users the option to deploy their own gateways or have their own devices communicate with third party networks, explains Samir Hennaoui, product manager, LPWA at Murata Europe. “Some cities have deployed networks based on LoRa that are free to access and service providers have appeared that rent access to their gateways,” he says.

A spread-spectrum modulation scheme supports data rates from 300bit/s to 50kbit/s to overcome the problem of interference in the shared RF band. Similar to LoRa is Sigfox, a low-cost, wide area M2M technology that was developed in 2010 by a French company of the same name.

Data rates for this technology are 10bit/s to 1kbit/s. The main differences between the two are range – Sigfox uses narrowband transmission to achieve up to 50km and LoRa has a range of up to 30km – and that LoRa is bi-directional, whereas Sigfox is not.

“Range depends on a number of things,” concedes Armour. With gateways on top of buildings, the range is more than with a gateway inside the building. “In big open areas we are getting tens of kilometres range typically,” he says, “for sending messages from the sensor back to the gateway in the cloud and also getting updates from the cloud back down to the sensor.

“Most technology allows you to send messages back to the network, but LoRa also enables you to receive messages from the network,” says Armour. This, he adds, is a key characteristic, as LoRa will be deployed in devices that are expected to be in long term use, for example parking sensors or occupancy sensors that can be updated over the air (OTA) rather than needing to be physically removed for updates.

The same OTA functionality can be used for security, which Armour describes as a moving target. A multi‑level AES encryption is the default in the protocol. “Encrypted data is sent from the sensor and goes on to the network encrypted. It is only when its gets to the end-user, who has registered the device, that they can unlock the data and decrypt it,” he explains.

“LoRa is designed specifically for moving sensor data, or small amounts of data,” says Armour. “It can do that over a very long range and at exceptionally low power. The consumption depends on the use case, but some of the sensors can run on coin cell batteries for over 10 years,” he says. “The great thing with sensors is that we can install a large number on a gateway in a building and all the data goes easily back into the cloud where you can start to make use of it,” says Armour.

Sensors can be used to adjust heating and lighting according to the number of tenants in a building, or to adjust the billing in multi-occupancy buildings. LoRa is also used for location services, to track goods, using the two-way communications capability.

“LoRa allows you to locate devices reasonably accurately at low power. If your data starts coming from a location that makes no sense to you, that may be because someone is spoofing, or the device has been stolen or moved,” Armour says.

In comparison, GPS is power‑hungry. “If you turn on a GPS chip, it can be 30 seconds before you get a location fix. That is hard on the battery,” he says.

Although GPS can give a precise location, LoRa can send data for a long time to let you know, for example, that your dog is not in your garden, or a pallet of goods is not at its destination.

Armour sees LoRa and Wi‑Fi as complementary technologies: “Wi‑Fi is great when you want to move a lot of data (emails, video, music) but that is not power‑efficient or low enough to run on a battery for sensors and devices. The use cases are different but the technologies are complementary,” he argues. “If people have Wi‑Fi, they will use that for smartphones and devices to talk to the internet. All the sensors and low power devices will talk over LoRa back to the internet to exchange data”.

LoRa developments

In October 2017, the LoRaWAN 1.1 specification was introduced to support handover roaming and with additional security hardening.

Handover roaming allows control of the end device to be transferred from one LoRaWAN network to another. The earlier specification supports passive roaming only. It also has support for bi-directional end devices having scheduled receive slots and additional security hardening.

The LoRaWAN Backend Interfaces 1.0 specification allows networks to offload the authentication procedure to a dedicated system which can be operated by a third party. Using a third party joint server allows the end device to be manufactured without having to be personalised for connection to specific networks.

The inclusion of passive and active roaming targets smart cities, although, as Research & Markets points out in its Smart Cities LPWA report, the largest opportunity for LPWA is LTE networks, following last year’s 3GPP Release‑13 and ‑14 that introduced enhancements to LTE in terms of active antennae, MIMO, self-organising networks (SONs), carrier aggregation and dual connectivity, LTE-WLAN aggregation and LTE-WLAN IP, Narrowband IoT (NB-IoT) and device-to-device communication.

By: DocMemory
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