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23 May 2023

Streetlamps and 5G small cells enter symbiotic relationship

Streetlights and 5G smart cells are made for each other, according to Germany’s O2 Telefonica, which started piloting the concept in Frankfurt during 2021 where it is now expanding city-wide. Other operators around the world are also picking up this idea of combining 5G small cells with street lighting to achieve the required densification at the same time as serving new “smart city” IoT applications from these converted poles.

This can be regarded as the second generation of smart street lighting, succeeding early incarnations where connectivity was provided by LPWAN networks, often based on the LoRa protocol.

Indeed, Rethink Research described Philips Lighting’s choice of Vodafone for its CityTouch connected street lighting platform as early as March 2016, as part of a drive to cut energy consumption. This ran over Vodafone’s cellular M2M (Machine to Machine) network, but since then many smart street lighting deployments have used LoRa.

That protocol however is only for low bit rate applications up to 50 Kbps, which is adequate for smart metering, environmental monitoring and smart lighting control, but not for some of the emerging use cases being posited now, including video surveillance. Those come under second generation smart lighting, such as what O2 Telefonica is deploying.

The poster application cited by Telefonica is intelligent watering of trees surrounding the poles, which could by itself have been served by LoRa or another low bit rate LPWAN protocol such as the cellular NB-IoT. This has been enabled by hosting the lamp posts within a wooden street cabinet incorporating a water storage tank for the trees, which are watered on the basis of moisture measurements from sensors in the ground, combined with the weather forecast. If the soil is dry, but rain is forecast, the system will cease watering, ready to resume only if the predicted amounts fail to materialize.

Other applications though, such as video surveillance, are more data intensive and have already been featured in streetlamp 5G deployments elsewhere. One example is around the campus of Nantong University in East China, where streetlamps with heads resembling lotus flowers in full bloom can access 5G for facial recognition among other applications, for what some have called experiments in behavioral engineering, incorporating machine learning.

More benign examples can be found elsewhere at the northern Spanish port of Gijon where Deutsche Telekom has deployed five of its Omniflow smart poles along the beach front to measure air quality, which is low bit rate, but also to monitor flow of pedestrians in order to open or close parts of the beach on the basis of usage, while contributing to traffic planning.

An extension of this is smart crossing, where the sensors will activate lights and sound alerts when pedestrians are detected about to cross a busy road – with thoughts of linking that to connected cars via Cellular V2X (Vehicle to Everything) to extend the warnings to drivers. DT has gone further than most by developing its own platform for incorporating 5G with street lighting, which could be offered commercially to other telcos.

This could well gain further traction because it simultaneously enables street applications and extends or densifies 5G coverage in areas where otherwise performance would be more variable depending on precise location within a town or city.

Lamp posts are usually well placed for small cell deployment because they often have fiber terminating conveniently somewhere close by for backhaul and their spacing is usually about right. Small cells in cities typically cover areas around 100 meters across and can readily be deployed on streetlamps, with the ability to disguise them and avoid the planning wrangles over larger macro cells amid complaints they bespoil the cityscape.

There is also the potential for small cells on streetlamps to backhaul themselves and avoid the need for fiber termination at all. This can be advantageous in some dense urban settings where fiber is not readily available at the required points and would be costly to install, and where there is line of sight between the cells, as often with street posts. Support for integrated access and backhaul (IAB) over common frequencies was introduced in 3GPP Release 17, which came out with final code freeze in June 2022.

There is also the mmWave dimension, with growing interest and trials in use of small cells on streetlamps to extend coverage beyond line of sight of the primary base station through use of 5G repeaters. These are now available from some specialist vendors such as Pivotal Commware, Prevail Technology and WilsonPro, which can receive incoming 5G source signals up to 10 Kms from the originating base station at data rates up to 1 Gbps, typically using adjustable mMIMO antennas to ease configuration.

We anticipate increasing deployment of mmWave small cells on streetlamps, especially away from the densest central urban canyons, where line of sight between cells and repeaters can more readily be obtained. That said, there is also potential even for mmWave frequencies, that is above 25 GHz, for non-LOS operation using reflectors or other techniques for mitigating the impact of signal blockage.