Unbeknownst to urban citizens, a new creature is about to invade our city rooftops, traffic lights, and lamp posts. She hardly makes any noise, does not look anything special and yet she may very well transform our everyday life. She is slowly crawling her way into unthinkable places above our heads where she hides, waiting patiently and communicating with her kin. Don’t run away! This is not yet another article on aliens or any other conspiracy theory of the kind, in fact we would like to dwell on a very down-to-earth subject: the deployment of small cells, the latest telecommunications infrastructure. 

A small cell is a low-power, short-range and small-footprint radio access point that provides cellular coverage to nearby users. Small cells serve the same function as the big cell towers that can be seen near highways (also known as macrocells), only their reach is way smaller. Several types of small cells exist according to their range and power output – femtocells, picocells or microcells are for instance referred to as categories of small cells.

Small cells typically have a range between 10 meters and half a kilometer.

Why do we need small cells?

In other words, what are the challenges that led telecom operators to the deployment of small cells? 

Well, for one thing, the number of mobile data users is growing exponentially. As for today, estimates give around 4 billion mobile data users but the growth rate should be almost in double figures in the years to come. In addition, those users increasingly want their data to be available all the time, no matter where they stand and their online habits – videos, live streaming, online gaming, to name just a few – are more and more data-consuming. Hence mobile network operators have to come up with solutions to cope with that crave for data usage. 

Global Mobile Data Traffic Growth is expected to double between 2019-2021. Credits @ZDNet

One parameter that could be modified is coverage, meaning that mobile operators could simply try to meet the surge of mobile data users by setting up new antennas, thus multiplying the areas where cellular service is available. However, the typical cellular site is expensive and rather cumbersome, to the extent that it takes usually quite some efforts to go through the administrative and installation process. Moreover, indoor urban areas -like a subway station for instance- often inhibits radio waves’ propagation coming from the outside and thus cannot be served by macro base stations. Also, for a cellular site to be profitable, it must provide coverage to a certain amount of users, yet in rural areas scarcity of users is real and standard cellular sites might represent a negative return on investment. Last but not least, macrocells tend to interfere with each other, which hinders any massive deployment strategy in a high density environment.

All these reasons combined prompt mobile operators to consider small and easy to adapt access points – small cells. They are much quicker and easier to install than classic cellular stations and, if deployed in great number, they could effectively cover a whole city without interfering with one another. Unlike cell towers, small cells can sneak their way into dense urban complexes and offer coverage where a macrocell would not be able to. Plus, their low upfront cost enables them to be deployed even for a small number of users, which can typically be the case in rural areas.  


Comparing macrocells and small cells network: small cells together cover a larger surface than the antenna alone and can be installed indoors to provide data for specific urban building (i.e. the mall)

But improving coverage alone won’t be sufficient to meet future data needs. We need to increase the number but also the connectivity of our antennas, be them big or small. The thing is, more users also means more data to be handled by the network. Just like road traffic, telecommunications networks can suffer from congestion and it is especially relevant in densely populated areas. This happens when a network node is carrying so much data that it deteriorates quality, results in queuing delay or blocks new connections. We have all already how annoying it can be to be stuck in the traffic inside our car or in front of our screen and we would very much appreciate that it would not become the norm in the future. 

This triggers mobile network operators to consider another parameter which is capacity. Increasing the network capacity (or bandwidth) will increase the amount of data that can be transferred via the network. To do so, telecom companies seek to offload macrocells by deploying small cells, which alleviates the pressure on the available bandwidth. Furthermore, mobile operators nowadays try to allocate more radio frequency spectrum to the cellular network. Notably, millimeter waves are currently targeted by mobile operators. This large section of the spectrum (between 24GHz and 100Ghz) is currently unused and could significantly increase the bandwidth. In addition, the speed of data transfers would also be increased. 

Current technologies (TV, 4G LTE, radio, etc.) only use a tiny portion of the spectrum, meaning that a large segment is up for grabs for mobile operators. Credits@AndroidAuthority.

Millimeter waves do retain the potential for solving the network’s capacity issues, but it will require adaptations from telecommunications equipment. Indeed, propagation losses are greater with millimeter waves, which means that they can only cover small areas -like sprinters, they travel super fast but fail to go the distance. Furthermore, building penetration is also shallower using millimeter waves. Cement and brick and to a lesser extent wood, glass and even water all attenuate high-frequency signals, thus impairing the transition outdoors-indoors for millimeter waves. 

The solution for telecommunications infrastructure is small cells once again. Because millimeter waves cannot travel far without losing their “strength”, a tight network of small cells would become very handy in the future. In the same spirit, small cells would avoid any problem of the signal’s reflection or obstruction because they will provide alternative paths to the consumer. Millimeter waves may not be able to penetrate buildings, but they would be able to circumvent them thanks to strategically located small cells.   

Hence small cells will prove essential for tomorrow’s telecommunications network, for they will solve coverage and capacity issues in highly populated urban areas. But how is this likely to change your everyday life?

What will small cells make possible?

The reason why you should get interested in small cells lies in one word: 5G. Small cells are pivotal for this new revolution that is likely to have an impact on our transportation systems, medical services, manufacturing industries, and so on. 5G is estimated to offer 20 times greater speed than actual 4G; for illustration purposes, this means that downloading an entire DVD would only take a handful of seconds. Small cells will also participate to the Smart Cities’ dynamic which very much relies on data collecting and processing. Big cities are evolving, high tech innovations are used to optimize costs, organization, and welfare of their inhabitants. The backbone for this bright future will consist of a high-speed data transmission network and this necessarily includes small cells.

Yet small cells are not confined to megapoles. In some remote places on earth, small cells will be instrumental in enabling people to have access to digital resources at a low cost. Education, financial or medical services will stand at a few clicks’ reach thanks to the installation of small cells in remote territories. Some countries have already jumped on the opportunity, launching programs for digital empowerment in rural regions. Such is, for instance, the case of India, who recently sparked its “Digital Villages” program, which aims at developing internet connectivity throughout all the country via wifi hotspots. 

But perhaps more importantly, one distinctive feature of small cells will precisely be that…you will not be able to tell they even exist! Small cells are designed to blend into the urban landscape and be completely unnoticeable to wanderers’ eyes. They usually look like tiny, rectangular boxes that you could easily mistake for some venting device or circuit breaker – if you ever happen to look at the odd places where they are installed. Small is beautiful but in this case, small is above all invisible which is key for a smooth transition to a more connected world.  

What could be Small Cells’ potential weaknesses?

Those marvelous little creatures do not come without downsides though. Obviously, their massive deployment would require them to be highly cost-efficient. That might not seem an issue at first glance, given that we are talking about low-powered, shoebox-sized devices, but the truth is that small cells’ design will have to take into account outdoor climatic conditions. Resistance to harsh environment will therefore be a valuable asset for small cells but it should not come at the expense of their small size, sober design or appropriate price. 

Most likely, the biggest challenge ahead of small cells’ massive deployment is power supply. Although small cells are not energy-intensive by any means, they still need to be powered, even when power outages occur on the grid. Just like macrocells, the small cells’ network cannot afford downtime periods and for this reason, will have to be equipped with backup power solutions. With their proliferation, the cellular network will have to rely more and more on small cells to ensure its stability, which means that each small cell will have to incorporate a backup power solution. 

This scheme illustrates the necessity to keep small cells powered no matter what. On the left, every small cell is powered properly and the network as a whole is functioning well. On the right, few small cells ran out of power and as a consequence, the macrocell they were supporting is facing congestion.

 

As for today, three power supply solutions are commonly available. One involves a remote power line using coaxial cables (note: a coax cable is an electrical cable specifically designed to transmit high-frequency signals with low losses) and a UPS. In this case, the typical voltage supplied is 89 V AC. However, this solution cannot realistically be generalized since it requires the operator to already possess a ‘legacy’ network using coaxial cables.

Another solution relies directly on Uninterrupted Power Supply (UPS) equipment, usually providing 120 / 220 V AC. Typically, operators are not able to monitor remotely the health of their UPS in outdoor conditions like it is the case for small cells, leading to downtime, or operational inefficiencies.

Telecom operators can also trust rectifiers associated with rectifiers (also known as battery chargers) and battery packs to power their small cells in the event of a power outage. Typically 48 V DC, this solution can arguably be considered the most reliable. Yet, these backup power equipment are cumbersome and sometimes even bigger than the small cell itself.

Here are the three current solutions to provide uninterrupted power to small cells: coax cables, UPS device or battery bank.

How Autonom can change the game?

Autonom aims to address the shortcomings of the latest solution. By providing AutoNod, an all-in-one device (rectifier and batteries are combined), Autonom’s solution takes up twice as less space than traditional setups. That distinctive feature greatly eases the installation of small cells and, after all, it makes a lot of sense for small cells to be powered by small batteries, right?

Think smarter, not bigger!

Autonom’s engineers did not stop there. They figured it might useful to add a remote monitoring system inside each and every battery to collect realtime insights on the battery’s health status. That way, the maintenance (crucial for backup power applications) is greatly simplified and no longer requires technicians to manually test every battery. Anticipating the massive deployment of small cells across our cities, Autonom is already providing a simple and smart management system for tomorrow’s cellular network. 

Using the best battery technology available, Autonom’s lithium-ion devices outlast its counterparts and retain an outstanding level of performance even in harsh climatic conditions. 

If you are not convinced yet, check it out yourself!

Sources

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