LTE for Critical Communications – Mind the Step
Public Safety networks, being designed for saving life under danger, are by nature demanding the most stringent reliability. Technically this requires vast geographical coverage and rigid service availability. Anything less would potentially put life under danger. The upcoming trend for mission-critical networks is leveraging multiple LTE operators as Mobile Virtual Network Operators (MVNO). As we all know, commercial networks have been designed for profit maximisation and serving consumer needs which differs from the public safety requirements being non-profit and reliability in any location at any time. One may wish the service quality improvement effort known as Network Hardening takes just a tiny effort to finish the job.
Let’s take a closer look at this.
On rough level, commercial LTE networks offer 90-99% reliability today. The example table beside demonstrates practical meaning in practice. It is fair to say that the 97% requirement does not satisfy the public safety need whereas the 99.9% is excellent, however practically more on the unachievable level.
The design principle of LTE networks is different from widely used GSM technology based TETRA networks. LTE is designed from capacity perspective avoiding any overlapping cell coverage. Radio resiliency comes through frequency layers such as 800, 1800 and 2600 MHz since they overlap by nature whereas site parameters such as transmission architecture needs to be looked at. Networks are powered by electricity – protection against site power failure caused by storms and other disaster recovery protection mechanisms have become vital. There’s much talk about upcoming Hydrogen society – now it’s the latest technology introduced for network hardening due to its greenness, superior quality and cost efficiency! Deep pockets with money will buy hardening for all sites to fulfill excellent reliability! Unfortunately, this is not always the reality, thus the need to look for more intelligent hardening approaches.
Let’s split each site into technology, frequency layer serving cells, base station, transmission and power. By hardening the power of a single site does not necessary mean 100% reliability because of transmission network which may be vulnerable due to another site. Also hardening all aspects of a single LTE network may not guarantee 100% availability due to failure of the inherent network system, thus asking for multi-operator LTE network resiliency. There’s no right or wrong answer – it really depends on your defined objectives and how much you are ready to spend!
I believe Intelligent Network Hardening starts by defining your reliability objectives. Thereafter comprehensive analysis is performed on what reliability is achievable with your predefined budget. In practice, it means bottom-up site-by-site, technology-by-technology, power, transmission architecture and operator-by-operator risk weighted analysis with an objective to reach and exceed your defined objective. It will not be easy and in my opinion, it truly requires independent Operational Network Design competences at its best!
Unfortunately, I don’t come with all the answers but it’s fair to say that complexity of network hardening arises when moving from dedicated TETRA into leased multi-operator LTE dealing with external parameters not fully under own control. If you’d like to discuss more about the issue, call/email me and let’s sit down together!