Màrius

This text was published at Worldsensing webpage

Wireless Sensor Networks (WSN) are based on the concept of tiny devices, with a set of sensors and a radio to send the results to a dedicated server or the Internet. This radio infrastructure has been typically designed keeping in mind the state-of-the-art on radio transceivers with low power consumption, fairly high throughput (up to Mbps) and short range (100 meters max). The solution that almost everybody has found has been to build a mesh network of devices, with a medium to low range between the nodes of the mesh. In these designs, data is sent from one device to another until the data reaches the sink node which itself is connected to the Internet in a more traditional way (3G, GPRS, Ethernet).

These mesh networks have several problems. One of them is the synchronization between devices: because each device has a different clock drift, it is mandatory to synchronize often the whole network, leading to raising energy consumption; another problem is the asymmetry on the devices consumption, meaning that not all devices drain power at same rate: this is because nodes closer to the sink will act as repeaters to other devices. This phenomenon complicates the operational costs of the network maintenance, even limiting the use of energy harvesting techniques in some of the devices in the same network. Other operational costs of these mesh networks are in the use of repeaters to enhance coverage of some parts of the deployment. It is not easy to detect these dark zones, and usually one needs trained people to do the installation.

Recently, a new concept of – to date proprietary – radio systems has arisen. This new idea is focused on sending few bits of data at a very slow transmission rate (less than 1 kbps) but with a long range (up to kilometers). These solutions are based on techniques like spread spectrum and specifically designed modulation schemes for high sensitivity.

With this new concept of radio in mind, the landscape of WSNs is changing. The use of a mesh network is no longer needed, because with this long-range radios all devices can communicate directly with the sink node. Hence, from a mesh network topology we are changing to a star network, and a single sink node receives data directly from all devices.

On the other hand, the sink node is usually more complex and power-hungry than a sink device on mesh networks, but this compensated by the fact that much less sinks are needed because they have significantly larger coverage. This change simplifies enormously operational procedures and costs, because they avoid the use of repeaters, simplifies coverage tests and hence usually it is needed less trained people to do the installation.

New players with these new radios – such as SigFox, Semtech, Weightless, On-Ramp – are trying to become network operators offering coverage without end-user intervention, like GSM operators did in the past.

These companies, although they are founded in very similar radio technologies, offer different solutions to their customers:

SigFox offers a truly long-range one-way communication system, even working with devices in basements and below-ground parkings. SigFox presented SigFox Network months ago, offering full coverage on France and they are starting to cover Spain and other EU countries.

Weightless’ solution is like a replacement of GSM networks for M2M devices, with similar coverage with much less power consumption. Weightless network is synchronized and bidirectional if the application requires it, and it is based on basestations placed in the same GSM towers actually deployed. Recently, they have started operating in the licensed bands which simplifies service level agreements (SLAs) in the operator space.

Semtech is creating a new family of RF transceivers based on LoRa modulation for long range radio links. Their strategy is to provide the transceivers without any other business model behind, but creating an ecosystem of 3rd party companies providing services like basesations, coverage, etc.

On-Ramp is offering a complete solution of transceivers and basestations, suitable for devices with very low datarate (up to 30 KBs per day) tolerating a fairly long latency, like smart meters, etc.

For these proprietary M2M solutions to survive, however, they will need to become standards or de-facto standards in the upcoming years. Once accomplished, deploying a WSN will be as easy as picking what operator fits better your application, checking that they are covering your deployment zone and just dropping your devices and starting receiving data into your servers. That is, concentrating on what your true business is: providing services to specific industries (and not spending most of your efforts in dealing with coverage problems).