Why 5G repeaters are being installed on streetlights

17 May 2023
5G repeaters are being used to expand coverage from cell towers, these devices are frequently being placed on existing infrastructure like streetlights to cut costs associated with installation. Source: FOlga/AdobeStock

The use of millimeter wave (mmWave) technology in the 30 GHz to 300 GHz frequency band range is the second phase of 5G development and is predicted to supersede the slower but more widely used sub-6 GHz 5G.

The higher band is being deployed to get the most out of 5G initiatives, but the waves have trouble getting through foliage, buildings and other obstacles, including human bodies, and are further degraded by moisture-rich atmospheric conditions. To get around this, small base cells are being used to piggyback on cell towers to expand coverage.

One of the ways to deploy these small cells into existing community infrastructure is by using street furniture, like streetlights. But, because mmWave small cells are short-range and need line-of-sight (LoS) transmission, more cells need to be installed than with cells using lower frequencies. The solution: 5G repeaters.

How does it work?

Until recently, frequency bands above 6 GHz were considered unsuitable for mobile communications because of distance limitations — mmWave technology is super-fast but also super-short range — and because signals are easily blocked by physical objects. Because it needs more towers to get decent coverage over sizeable distances, mmWave technology can be expensive to deploy.

However, new antenna technologies and improved signal propagation are increasing the possibility of successful deployments on existing, low-cost street furniture. But, it’s technology in its infancy and misleading marketing claims by carriers about the speed and coverage of connections make the topic confusing for consumers. For example, in 2018, AT&T claimed to be the first carrier to deploy 5G services — 5GE — to its customers but this took place over its 4G LTE-A networks.

Why use streetlights?

Street furniture includes streetlights, traffic lights, electricity poles and billboards at bus stops. Attaching small cells onto street furniture is a potentially budget-friendly option for telecoms operators to densify 5G network coverage and cover signal gaps.

Data is transmitted over multiple wireless links between fiber point of presence (PoP) installations and termination points. Streetlights already have an electricity power supply, are usually erected close to fiber infrastructure for backhaul, and their height and spacing are a good match for small cell deployment.

The way forward

A recent Wireless Infrastructure Association (WIA) report shows that at the end of 2022, there were 452,200 outdoor small cell nodes and 747,400 indoor small-cell nodes across the U.S. These figures included connections across a range of frequency bands, including mmWave.

While it is envisaged that small cell deployment will take place in dense urban environments, there are potential use cases in rural environments like precision agriculture, and for personal networks, video surveillance and augmented reality (AR) applications.

Despite the challenges, exploratory small cell deployments on streetlights are already operational in numerous countries, like the U.S. and Germany. Leading telecoms companies predict full 5G coverage using mmWave and small cell technology by the end of 2025.

But technological trends don’t always follow the rules. For Google, mmWave is just one tier in a stack of technologies to enhance cloudification. These technologies include multi-access edge computing (MEC), massive machine type communications (mMTC) and the use of all band types, like low-, through mid-, to high-bands depending on application requirements.

Pros and cons of mmWave technology

mmWave is the band of radio spectrum designated by the International Telecommunications Union (ITU) between approximately 10 mm (30 GHz) and 1 mm (300 GHz). mmWave is used for extremely high frequency (EHF), high-speed broadband access. The frequency for 5G use usually ranges from 24 GHz to 100 GHz. To put this in perspective, 3G and 4G cellular networks transmit signals below 3.6 GHz in the radio frequency (RF) spectrum.

mmWave technology enables higher data rates, particularly for Wi-Fi and cellular networks, and allows the use of smaller antennas. The technology is useful for connecting small internet of things (IoT) devices in massive IoT networks and in use cases like autonomous vehicles, security scanners, active denial systems (ADSs), smart cities, transportation hubs, outside applications like sporting events and in disaster management scenarios.

However, mmWave technology relies on LoS. On their own, waves can’t penetrate or be directed around objects. Small cell antenna technology, RF repeaters and the use of graph and mesh network topologies address these issues.

What is small cell technology?

Small cells are low-power, miniature base stations, about the size of a pizza box and are used to expand traditional 5G coverage. They are portable, relatively easy to install and cover small distances, from a few meters to a few hundred meters. The best use cases are high-density traffic areas.

The main problem with small cell technology is that it provides 5G coverage only for short distances, so, while the need for building new towers in the 5G landscape may be reduced, small cells need to be installed in a hyper-dense manner, up to 200 per km/sq, and they are not quite as easy to install as consumers are led to believe because they still need fiber connectivity and some cities charge high fees for the use of their infrastructure, like streetlights or road signs. This gives rise to another deployment challenge, what constitutes a pole?

Small cells work in a similar fashion to any other base station but make use of multi-user massive multiple-input multiple-output (MU-MIMO) architectures and beamforming to increase data speeds, allow more users on a network and reduce latency. MIMO enables enhanced spectral efficiency and more concurrent transmissions across smaller bandwidths. Beamforming is used in 5G networks to reduce the challenges of physical and range interference. It works by using a phased array of antennas to redirect beams, or waves, in a particular direction. The successful deployment of small cells is dependent on both the LOS and non-line-of-sight (NLOS) propagation of signals and antenna design. MIMO antennas allow engineers to redirect beams to address NLOS conditions.

There are three types of small cells. Femtocells are used primarily for residential and enterprise applications, up to 50 meters and 16 users, to reduce network congestion, particularly for home users. Coverage for Picocells is more than for Femtocells, up to 250 meters and 64 users, but is still used for smaller personal and commercial applications. The coverage area for microcells is up to 2.5 kilometers and 200 users, which makes the technology most suitable for outdoor applications.

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