How does mobile coverage work

Mobile connectivity, alongside the development and implementation of mobile phones and supporting infrastructure, has been one of the biggest leaps in communication and connectivity technology and the development of in building mobile networks in recent years presents an opportunity to harness mobile connectivity in places where it was previously not available. 

By mobile coverage, we are referring to the supporting infrastructure that provides the connectivity coverage rather than end user devices. The breakthrough came with the development of a cellular radio system that a user device could connect to wirelessly. This radio system is comprised of many radio masts (or antennae) distributed in a grid or 'cell' configuration that broadcast a signal that devices can connect to.

Devices connect to the mast best suited to provide them with a signal and as a device moves it will automatically be handed over to whichever mast and cell can provide it with the best signal strength.  When the device is passed from one cell to another it uses make-before-break principles to assure continued voice connectivity, unlike most wireless technologies, all of the call information is also passed over so there is no loss of connection and calls are continued seamlessly.

The first implementation of mobile systems are referred (retrospectively, after 2G was launched) to as the first generation, or 1G. This first generation was built around analogue voice only. The next step change was the second generation of technology,2G. Here, voice moved from being analogue to digitally encrypted as well as introducing a digital short messaging service (SMS) and GPRS packet-switched data for basic data applications, such as access to email and multimedia messaging (MMS).

Following on from this there have been more advances in the way mobile data can be transmitted making use of higher radio frequencies and more complex algorithms for data compression, leading to higher data rates. Each of these upgrades is referred to as a new generation of technology and became known as 3G, 4G and the latest iteration which commercially launched in 2018, 5G. 

Standards for the next generation of mobile connectivity, 6G, are currently being defined and are commercially anticipated by 2030. For any implementation of indoor mobile in the next 5 years from the time of writing, 6G products and capabilities will not be available and as such they are not taken into consideration in this guidance or the below table.

The table below contains a simple comparison of the different mobile generations.

More information on the timelines is available. 

As technology has improved over the years to provide faster data rates using higher frequencies, new issues with coverage and access to the connectivity have emerged. 

The higher the frequency the shorter the distance radio waves travel, and they are less able to penetrate objects and buildings to reach the receiving device. This lack of penetration has become more noticeable with widespread rollout of high speed 5G requiring comparably more 5G masts within the same area to provide the benefits of faster 5G. Low frequency (coverage layer) 5G spectrum is broadcast at lower frequencies than 2G or 3G, but this low frequency 5G won’t have most of the 5G benefits, such as higher data rates.

High frequency public mobile will also be less able to penetrate buildings and may reduce indoor mobile connectivity experience. One way to overcome this challenge is to install a private or public indoor mobile solution within your building, which allows for distribution of signal inside the building to maintain connectivity and service. 

For an example of an NHS organisation who have introduced an indoor mobile solution see Cambridge University Hospitals NHS Foundation Trust – Indoor mobile network. 

Mobile connectivity can be broadcast as Public or Private. Only Public networks can be built outdoors due to spectrum licensing and provided by MNOs (Mobile Network Operators) who purchase this public spectrum through government auctions in each country. The network operator defines what and who can connect to their service. Whilst technically possible for 2G and 3G to be used to build indoor networks these options will not be covered in this document, due to the planned switch-off of both 2G and 3G (, and due to technical limitations and cost considerations.

See 3G and 2G switch-off - Ofcom and 2G / 3G Switch-Off for the NHS (you will need an NHSFutures login) .

4G and 5G can be procured as indoor networks and 5G standards in particular have been specified to make this simpler to implement with open architectures. Traditionally, each mobile network provider would have built their network architectures on a set of proprietary hardware and software making it difficult to integrate with others. 5G has been developed with open standards, making much simpler to connect different vendors systems. This is called Open RAN or ORAN, a non-proprietary version of the Radio Access Network (RAN) system that allows interoperation between cellular network equipment provided by different vendors and makes it much easier to implement private 5G based on an open market principle.

See Open RAN principles.