Connectivity technology

The following is a non-exhaustive list of technology options used to provide connectivity for peripatetic workers across the NHS today: 

• mobile data (4G/5G)
• multi-SIM, dual SIM, bonded SIM cards
• satellite connectivity
• 4/5G cell boosters or repeaters
• Wi-Fi hotspots and mobile hotspots such as patients Wi-Fi connectivity and Mi-Fi

Mobile data, sometimes referred to as cellular data, is the internet connectivity delivered to your mobile devices wirelessly. If you're using the internet on your phone, or other SIM enabled device, and it's not connected to Wi-Fi, then you are using what we call mobile data.

To access mobile data a user will need a device capable of using a SIM card, a data contract and access to a 4G or 5G data signal.

In the most basic terms, a SIM holds all the information needed to allow connection to specified mobile phone network. SIM cards hold information that not only authorise the device to connect to the network but also user identification and the associated phone number.

SIM types

Physical card (SIM card)

These as currently the most common type of SIM card, and the one most users will be familiar with. The mobile provider issues the physical card which then needs to be inserted into the device to connect to the network. 

Each SIM card can connect to a single network, some Smartphones can support two physical SIM cards.

eSIM (Embedded SIM)

An eSIM is a blank 'SIM card' attached to the circuit board of the device as part of the manufacturing process. Network providers can then 'push' the necessary SIM details and identification out over the air to users. 

This has the advantage of being able to quickly connect to a network as there is no need to wait for a physical card. This type of SIM is becoming very common in mobile phones, however the types of devices that can take advantage of eSIMs is limited as they may need to support SMS (text) messaging to receive the SIM configuration information. 

One of the benefits of an eSIM is that you can use multiple eSIMs from various providers on a single device, allowing connection to multiple networks. How many eSIMS can be active in the same device is dependent on the manufacturer of the device and the network carriers.

iSIM (Integrated SIM)

iSIMS are similar to eSIMs in that they are built into the device. The main difference is that iSIMS are not a physical device that needs to be attached to the circuit board but are part of the devices base 'chip set' alongside other functions that make the device work.

iSIMs are becoming very common for Internet of Things (IoT) devices that are small and require very low power. The first commercially available smartphones using iSIMS were released recently and it is expected that iSIMS for consumer smartphones will become more popular in the near future (1 to 2 years).

Roaming SIM

A roaming SIM is a mobile phone SIM card that operates on more than one network, 'roaming' between the networks to seek the best available signal and connectivity. As getting data access is dependant on the location you are in and if you have coverage from your mobile carrier roaming SIMs have the benefit of being able to choose between one or more networks for a connection. 

Depending on the mobile carrier and the type of contract you have with them, they may allow roaming onto another carriers network if there is no coverage from the primary carrier. If there is no coverage from any carrier, then roaming SIMs will not confer any connectivity benefit.

Most SIM that allows roaming will switch network automatically, however, the threshold for switching network needs to be considered. This switching could happen when the signal drops below a certain threshold or when the signal is lost altogether.

When discussing roaming SIMs the key distinction to understand is 'steered' versus 'non-steered'. Steered roaming is when the primary network provider has a list of networks it is possible to connect to and ranks them in order of preference. You are then 'steered' to connect in the preference order of this list.

This can cause issues as if there are several of the networks are available to you then you may not connect to the strongest but to the highest ranking one on your network providers list.  

Non-steered roaming is where there is no list to 'steer' the network selection, and the SIM will connect to any of the partner networks available, usually based on the quality of the signal.

Multi SIMs

Some devices can support multiple SIMs, to support access to multiple mobile networks with the aim of improving connectivity coverage and quality. This can be achieved via using 2 physical SIM cards or up to 6 eSIMs, or a combination of both. Each SIM needs its own contract.

The benefit of this approach is that if there is no, or poor, signal from one provider, it is possible to switch to another of the SIMs in the device to take advantage of better-quality signal and connectivity from another network provider.

Dual SIM

Dual SIMs support the use of 2 SIM cards in one device, to confer the benefits multiple network providers without having to manually switch between them. This can be either in an 'Active/Standby' configuration or 'Active/Active'. The type of configuration will depend upon the device and which it can support.  

Active/Standby has only one SIM connected to the network at a time (Active), with the other SIM dormant (Standby). With this configuration the user generally has to manually change which SIM is active and connected for data.

Active/Active mode supports both of the SIMs being connected for voice and messages, Active/Active can support access to voice and messaging for 2 phone numbers, for example business and personal, without needing to carry 2 devices.

However, currently only one SIM can be connected for data, meaning the connectivity benefits are limited. The SIM that is used for data is marked as the primary SIM. 

Bonded SIMs

Bonded SIMs use multiple SIMs to connect to all of the MNO networks at once to provide a single enhanced, or 'bonded', network connection.

This is typically achieved by use of a dedicated router with multiple SIMS cards installed from providers to create the 'bonded' connection. This dedicated router has a radio for each of the SIMs which allows for data connections from each to be combined and broadcast as a Wi-Fi SSID. The end user device (for example, phone or laptop) then connects to this router via Wi-Fi.

Whilst this can provide enhanced connectivity there are additional cost and usability considerations, with these devices coming at an additional expense, both for the router and subscription to multiple data contracts and requiring workers to carry another piece of equipment that requires power.