The functionality gap PMR and LTE
The functionality gap – should businesses pause for thought before making the change from narrowband PMR to broadband services?
There are many arguments for replacing a legacy PMR technology, such as DMR or TETRA, with mobile broadband services, as technology such as LTE can potentially bring a host of additional benefits and functionality to an organisation. However, there are also concerns about the ability of these services to provide the unfailingly reliable service that is expected of mission critical networks. In this blog we will explore an example of the functionality gap between traditional PMR technology, in this case, TETRA, and LTE and think about the implications for a company looking to implement this new technology.
The Third Generation Partnership Project (3GPP) has said in a statement that release 15 of the LTE standard includes most TETRA functionality, but how this looks in practice remains to be seen.
One feature that will not be available is Direct Mode Operation (DMO). LTE has standardized a similar, but not identical function, called Proximity Services, or ProSe however unlike DMO this is a new standard that has not been widely used so far.
What is Direct Mode Operation?
Direct Mode Operation (DMO) is a feature of TETRA technology that enables a subscribed device that is outside the area of network coverage to communicate directly with another device without base station coverage. This is used extensively in public safety TETRA networks at present, as well as by some transport providers where the feature is a key requirement of their networks. For example; a police officer using a handheld terminal can travel outside the coverage area but still maintain contact by using their vehicle mobile as a repeater thanks to DMO functionality. The vehicle’s mobile radio links in to the network and communicates to the handheld terminal directly, even if the officer has strayed outside of the immediate area of network coverage. The vehicle mobile is able to do this as it gets slightly better transmit power than the handheld device, allowing the police officer to use their handheld radio outside the network area and away from the vehicle, with the vehicle mobile essentially acting as a repeater.
Barriers to effective mission critical communications with LTE
This switch from DMO with TETRA to ProSe with LTE is an example of where the mission critical industry might not get the same attention in LTE, 4G and 5G as they have previously enjoyed from more mission critical focused technology in the past.
There have been some tests carried out as a proof of concept for ProSe, but the results fell short of the functionality of DMO. The two devices had to be within meters of each other for the technology to work, which means that in a real-world scenario it would add very little to coverage capabilities.
There are other features that have developed much more quickly since being introduced in the standard, such as mission critical push to talk (MCPTT). However, it is uncertain whether a serviceable alternative to DMO will be commercially available in the foreseeable future.
Although the latest standard for LTE introduces ProSe to plug the gap left by DMO, this still requires chipset manufacturers to develop new device chips to support it. This particular feature was included in Release 13 in the 3GPP process; however, the feature is not available or on the horizon, more than three years after initial standards were set. While there is always a lag of two to three years between a standard being set and the reflection of that standard in the market, the chip set manufacturers will not develop this new functionality until there is a sufficient market for the technology and a sufficiently strong business case, ensuring return on investment for the updates.
This creates a potential conflict between the mission critical market and commercial market requirements. Chip set manufacturers and operators of 5G and LTE are dealing with millions of subscribers on the commercial networks, whereas mission critical subscribers like the emergency services are only a very small percentage of that overall subscriber picture. Because of this, updates relating to ProSe might not be prioritised by the manufacturer.
Because business priorities and their own bottom line will always come first for manufacturers, the sensible way forward for organisations is to embrace a blended model.
Until LTE is proven in a mission critical setting, the functionality is established and we are able to be 100% confident in the technology and its ability to deliver a faultless mission critical service we should exercise some caution.
In our view, a phased and gradual migration is the best approach. After all the point of switching technologies is to improve overall communication capabilities. While there will be benefits such as an improvement in data transfer rates with LTE, we still do not know what other essential services, like Direct Mode Operation, will be missing.
We advise retaining existing TETRA or other PMR services and bringing in LTE to support complementary functionality and services in parallel on the same fully integrated network. This will allow organisations to continue to use the mission critical elements of TETRA and slowly test and develop use of LTE in a controlled manner.
If you are looking to integrate LTE with PMR technology get in touch today.