Small cells increase telecoms network range and capacity in densely populated urban areas which cannot be sustained by macro cells on their own, filling coverage gaps and increasing bandwidth. This is particularly important in the age of increasing mobile data usage, smart cities and the Internet of Things.
Small cells are key drivers of 5G communications. Network operators will not only use the low and mid-band spectrum that existing mobile networks rely on; to deliver 5G they will also need to use the high-band spectrum. This spectrum only carries over short distances (as opposed to the longer distances covered by lower frequencies), so carriers will need a much more dense collection of access points.
These access points, or nodes, are the small cells required to power 5G. They might well be situated on city lamp posts, on commercial buildings or on traffic lights.
Small cells are capable of transmitting high data rates in distances between 10 metres and 2 kilometres, both indoors and outdoors. This is important because macro antennas sometimes have a hard time providing coverage indoors, and small cells are ideal for use in just these places where macro antennas cannot reach. Sports stadiums, college campuses and exhibition halls can all be very well served by small cell sites.
Coverage and capacity – why small cells are important
Traditional macro antennas can cover a wide area. Whilst a single tower might technically have coverage of up to 20 miles, the wireless signals that connect the tower to the end user are only capable of carrying so much data at once. The more connections on the network, the more data is being carried, thus the slower everyone’s connection becomes. It is not unusual to be in the middle of an urban area or a sports stadium with full bars on your smartphone, but be temporarily unable to place a call or download data.
The frequency bands that are currently being used by carriers to transmit data signals can easily get clogged up (as in the example above). It is just this sort of wireless density problem that small cells step in to solve.
Small cell nodes can be deployed many times over within the areas covered by traditional macro antennas. Each node is potentially capable of carrying the same amount of data as the tower, but as there will be very many more small cell sites in the same geographic area, it is less likely that any one small cell node would be overwhelmed with data.
Small Cells and 5G
Whilst small cells are not a new concept, having been used initially in 3G deployments, and more significantly with 4G, they are ideally suited to help deliver 5G connections. For 5G, small cells equate to more reliable coverage and improved performance and capacity.
As stated earlier, lower frequency bands (sub 6GHz) can cover great distances, but they offer slower data speeds.
But in addition to these lower frequency bands, 5G networks will utilise the previously under utilised very short wavelength spectrum (MmWave), capable of very fast data transfer. These high frequency bands can carry much more data than the lower frequencies, but they can only transmit over a much smaller area, hence the requirement for small cells.
Potential issues facing the roll out of small cells
Amongst the issues that network operators are up against is the length of time that small cells take to deploy.
All major wireless network operators are currently setting up small cells, and typical installations incorporate 20 to 25 small cells per square mile. In any country rolling out 5G, many thousands of potential small cell locations must be identified.
Once these sites are found, public and private property owners are to be contacted, permission sought, and leases need to be agreed. At the same time, local authority permission needs to be granted.
Costs to acquire, lease, deploy and maintain new small cell sites can be very high, especially in the private sector, and on privately owned infrastructure such as advertising hoardings.
Generally less expensive are public infrastructure sites (so called ‘street furniture’ sites), like lamp posts and traffic lights. Whilst it can easily take a year for a small cell site to be permitted on publicly owned sites, from the carrier’s point of view it makes sense for them to make one big small cell deal within a city’s authority area than trying to negotiate hundreds of smaller deals with individual building owners.
Many of the planning requirements covering small cell installations were initially created to cover traditional cell phone mast installations. These traditional installations might have included a full cell phone tower, and a free standing building nearby to house network and power equipment. This has led a call for authorities to initiate different planning regulations for these less obtrusive small cell sites.
One answer would be for authorities to allow blanket deployment of small cell sites within commercial zones, permitting their installation on public infrastructure like lamp posts, as well as on high rise buildings and outside shopping centres. The network operator would then only need to agree planned locations with the local authority.
Different regulations could apply to residential areas, parks, schools and colleges, as they would to more sensitive areas such as hospitals and historic buildings.
Small cell sites are poised for significant growth with 5G, having been used with 3G, and their use ramped up with 4G. The more reliable network coverage, and the improved overall capacity and performance they bring mean that dense deployments of small cells will continue to grow. Small cells will bring with them faster more reliable speeds for users both outdoors and significantly indoors where most data usage happens.