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Wi-SUN: here’s why mesh networking works

First publishedin ITS International
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There are several networking options available for smart city planners. Phil Beecher of Wi-SUN Alliance makes the case for wireless mesh networks when it comes to rolling out IoT solutions

The Internet of Things (IoT) is growing fast. Connecting thousands of sensors and control systems in bi-directional networks is paving the way for a new generation of smart city and transport infrastructures. For many of these applications, wireless connectivity is essential where cable installation is not practical.

Wi-SUN Alliance surveyed 350 organisations (within government, telecoms, energy, utilities and others) across the US, the UK, Sweden and Denmark about the barriers, challenges, opportunities and benefits of the IoT. Two-thirds (67%) listed IoT enablement as an IT priority within the next 12 months. These organisations are nevertheless cautious about the technologies they use when rolling out IoT solutions. The most-cited evaluation criterion was network topology and coverage, at 58%. The right network is critical for a successful IoT solution in any scenario.

Wireless mesh networks are becoming the glue that holds modern cities and modern transport infrastructure together. Network planners in smart cities are using them to both monitor and control the equipment underpinning the applications and services.

As these organisations continue to modernise, such networks represent a growing trend. Research and Markets forecasts that this network category will grow at a compound annual growth rate of 9.6% between 2017-2023, reaching $8.9 billion.

Mesh networks

Cabled networks use a variety of topologies for interconnection.  However, wireless networks typically use either a star topology or a mesh topology, or a combination of star and mesh.   

With star topology, devices connect to a central tower. One shortcoming of this type of network is reliability. With just a single connection between the device and the tower, equipment failure, interference or an obstruction can cut communication from the device.

Conversely, mesh networking enables devices to connect with multiple others nearby. Connected devices can relay traffic from each other, passing it to one of several nodes downstream. Mesh networks will typically choose the shortest route to a backhaul point, which can convey traffic along a typically cable-based, high-speed link to back-office systems.

Multiple connections

Wireless mesh networks carry several benefits for smart city planners and transport hubs, as well as other implementers that need to build connectivity between large numbers of devices over a wide geographical area:

  • Resilience Because mesh networks build multiple connections with other devices nearby, they are inherently resilient. If interference or device failure causes a communication problem on one route, traffic can still get through using another route through the mesh.
  • Cost Wireless meshed devices relaying each other’s traffic minimises the number of cable-based connections and allows flexibility when locating connections to the backhaul network.
  • Fast implementation Using a self-forming wireless mesh network can speed up initial network deployments, decreasing the time to market for critical infrastructure services. If additional devices are deployed after the initial installation, then they simply join the existing mesh network.


Networking specifications

In 2012, the IEEE published its IEEE 802.15.4g, a standard for the physical radio layer for wireless Smart Utility Networks. The Wireless Smart Ubiquitous Network (Wi-SUN) Alliance was formed at this time to leverage the standard by developing communications profiles and testing and certification procedures that would help vendors to produce compliant and interoperable products.

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Ratified in 2016, narrow band-IoT (NB-IoT) was developed by the Third Generation Partnership Project (3GPP). This cellular protocol uses either GSM spectrum or the guard band used to separate channels and prevent interference. LoRaWAN is a low-power, wide-area network technology based on proprietary spread spectrum technology, focusing on equipment that communicates infrequently.

NB-IoT and LoRaWAN use a star network topology. As with cellular systems, star networks are susceptible to poor connectivity due to ‘black spots’ introduced by weather or physical obstructions. As a standards-based technology, NB-IoT has the potential to garner widespread support and build an ecosystem of interested parties. However, this technology is still relatively new, and work is ongoing.  LoRaWAN is supported by a non-profit alliance of over 400 members. However, the interoperability of different member ecosystems is unclear. LoRaWAN uses proprietary radio technology rather than a standard.

Efficiency and security

When evaluating IoT network requirements, it is important to assess performance and efficiency together to understand the trade-offs of any particular technology. High-speed communication is crucial in many IoT environments, where control data must be relayed quickly to and from sensor devices in the field. Wi-SUN’s technical profile specifies high data rates, reaching up to 300 kilobits per second (kbps). Mesh devices can also provide very low latency (tens of milliseconds) for fast data transfer.

Security is critical in wireless IoT devices, especially in industrial settings where intruders could otherwise disrupt mission-critical processes ranging from energy distribution to road traffic flow. The Wi-SUN Alliance designed its technical profile with extremely robust security in mind, specifying the use of x.509 certificate-based, public-key infrastructure to authenticate devices, as well as Advanced Encryption Standard (AES) encryption and message integrity check. Keys are also rotated automatically using the 802.11i (Wi-Fi Protected Access II) standard.

Devices will protect their digital credentials either by storing them in hardened cryptographic processors that are resistant to physical tampering, or by using physically unclonable function (PUF) technology.

Wi-SUN Alliance

The Wi-SUN Alliance is a global, non-profit, member-based association. Its mission is to drive the global proliferation of interoperable wireless solutions for use in smart cities, smart grids and other Internet of Things (IoT) applications using open global standards from international organisations, such as IEEE 802, IETF, TIA, TTC and ETSI. With more than 180 members worldwide, membership of the Wi-SUN Alliance is open to all industry stakeholders and includes product vendors, services providers, utilities, universities, enterprises and municipalities and local governments.

Extensive growth

Scalability is an inherent requirement in many industrial IoT networks. Covering a wide geographical area, these networks often encompass thousands of wireless sensor and control devices covering a wide variety of use cases.

As smart city councils and planners become more confident in the financial and productivity benefits from these devices, they are deploying more of them and expanding the range of supported applications. Wireless networks supporting these devices must enable rapid, extensive growth.

Mesh networks are designed to scale thanks to their highly-distributed peer-to-peer communications topology. In fact, the reliability and performance of wireless mesh networks increases as more devices are connected. Our community has already deployed tens of millions of devices around the world, including several projects involving more than a million devices on an individual network.

With thousands of nodes deployed over long distances, IoT wireless networks and the devices they support must be able to operate for extended periods without maintenance.

Because mesh topologies become more reliable as they scale, networks based on Wi-SUN can also keep operating even in the event of occasional device failure, reducing the negative impact of short-term failures on smart municipal and utility wireless infrastructures.

In conclusion, wireless mesh networking offers the perfect solution for modern wide-area IoT deployments. Evaluation teams should factor this networking topology into their technology decisions, while also considering characteristics including security, scalability, interoperability and reliability. These networks must not only be easy to set up but must run for years, offering a mixture of high bandwidth, low latency and power efficiency.

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