Wireless technology for your Smart City networks of IOT devices

The “Smart City” sounds like a science fiction vision of the future. In reality, we already live in Smart Cities, at least to a degree. We travel – whether by car, foot or public transport – with the aid of mapping software. We pay for tickets or parking with our phones. The numbers of people moving through a particular area may be discretely being counted, to understand the behaviours of crowds throughout the day. In this article we look at wireless technologies that are being deployed and why different approaches suit different use-cases.

There are many different wireless technologies available in the market, each with unique characteristics, but they can be classified according to a few basic parameters. The critical factors are Speed (of transmission), Power Consumption, Range and Cost. Further considerations are Security and the Complexity of implementing a solution.

Bluetooth – a core IOT technology

One of the most straightforward wireless technologies to implement is Bluetooth. This offers easy connectivity to an individual’s smartphone for applications such as parking and vehicle charging, or local information either outside or inside facilities such as museums and galleries. The key characteristics of the technology are that it is reasonably fast, and capable of low power operation. So connecting units can be battery powered for extended periods, making installation simpler. It is also a low-cost technology making it attractive where many units are required.

The main drawback of Bluetooth is its limited range, and basic broader networking capabilities. For some use-cases, local interaction with a smartphone or other device might be sufficient, but often a solution might require some broader connectivity in addition. Cellular connections can be an option, but this requires network coverage, which even in an urban environment is not guaranteed. It also requires back-end integration, and adds costs associated with network access and web services.

LoRa – a wide area technology for Smart City Applications

An alternative is LoRa (long range) – a lightweight wide area network protocol using free access spectrum. Whilst limited in bandwidth, LoRa offers the option to install your own network, meaning you have control of coverage. It also is much lower power than cellular, making battery powered devices realistic. In situations such as parking management, where cellular coverage may be poor, or monitoring inside large buildings, where a cellular solution may not work well and be overly complex, this can be a good solution.

Secure Access to Buildings

Secure Access to buildings and within them is an important topic Simple RFID  (radio frequency identification) badges, which can be easily copied, are now seen as a weak solution. The first element to improve security is to have secure storage for any digital key – either in a physical or virtual secure element. This allows the key to be validated by cryptographic exchange, but never accessed or copied.

However secure keys are not necessarily enough if the exchange between a key and access control unit can be intercepted or boosted,giving access to a malicious actor via faking proximity. Here Ultra-Wide Band (UWB) communication is increasingly being  used when security is a key consideration. UWB allows you to measure distance precisely. It is extremely hard to fake, unlike more conventional signal strength methods. Thus, you can be sure it is really the key holder at an entry point, and not someone transmitting a signal from a distance.

Street Lighting Solutions

When considering some outdoor applications like street lighting, the “Smart City” approach can promote energy efficiency whilst still providing necessary illumination for safety and security. It is wasteful to have lighting illuminate empty streets. So a solution with presence detection can ensure lighting is only on when needed. A mesh type solution can be used to link lighting units locally to each other, together with presence detection units, so that a safe area around a vehicle or pedestrian can be kept illuminated whilst unused areas of the street remain unlit. In such a scenario a Bluetooth mesh could be deployed, or if range was an issue, there are other solutions such as DECT NT+ . As power supply is not an issue in lighting solutions, radios can be run at maximum transmit power to increase range.

For professional lighting, there are also dedicated higher level networking protocols such as DALI (Digital Addressable Lighting Interface). Originally based on a wired connection bus, recent updates to the specification have introduced standards for gateways to Bluetooth Mesh or Zigbee, or with DALI+, a native wireless implementation on top of Thread. Future evolutions of the standard may extend support for DALI+ over Bluetooth Mesh and WiFi.

WiFi 6 – a WiFi for IOT solutions

Moving onto WiFi, this also has interesting use-cases for the Smart City. Whilst most WiFi networks supply straightforward private computer networking, WiFi access points (APs) are sufficiently ubiquitous in cities that there is nearly always one nearby. These can be used for a location service or medium accuracy, as many WiFi AP have known locations. There are now tracking devices that support both GPS and WiFi based location tracking. So this can work seamlessly indoors and outdoors. The WiFi part doesn’t require connection to the WiFi AP, as for many the identity of the AP is simply broadcast.

For more general IOT applications WiFi has always offered very good potential bandwidth, but suffered from high power consumption, and limited channels. This means that if many devices are present in the same area, the network quickly becomescongested. However the updates in the WiFi 6 specification establish the possibility of both lower power applications and more efficient spectrum sharing, opening the way to dense networks of devices. For applications where the more modest speeds of Bluetooth aren’t sufficient, or faster outward IP connectivity is required, WiFi 6 moves WiFi firmly into IOT territory.

Conclusions

Clearly for any particular use-case, design engineers need to conduct a detailed analysis of the different requirements of their Smart City network of IOT devices– range, speed, power supply constraints, etc, before choosing the appropriate technologies.. Often more than one technology can potentially fit the application needs.

By: Nick Wood, Director, Sales & Marketing, Insight SiP