The current discussion
concerning broadband access to public safety mobile units has been active and
ongoing for years. The primary reason for discussion regarding this issue is
the fact that current dedicated digital authority networks cannot provide the data
capacity required for modern applications. However, capacity limitation seems
to be the last point that discussion participants can agree on. The question of
how to bring the broadband to these vehicles has multiple opposing viewpoints
and conflicts of opinion.
The first and the most obvious
answer to bringing broadband into public safety vehicles is to build dedicated
networks for authorities. The main problem with this solution is the huge cost
involved, along with limited available frequencies. The second solution is to
use a commercial provider with special deals to offer the data capacity
required. Here the main concern is the availability of the data and resilience
of the network. The third option includes several hybrid solutions, either
combining dedicated and commercial networks or using multiple commercial ones.
The key problems with this latest solution are perceived to be resilience and
availability.
Participants in this discussion
are however too often lead astray by either their own personal experiences on
how networks function, by operator promises regarding availabilities, or
dedicated network equipment providers’ denigration of commercial networks. The
only way to know with certainty the availability of any single network or
selected networks together, is to test them in real life environments with the
same applications used by the authorities.
This document shows the results
of several selected pilots or tests conducted in Europe and the USA. The number
was limited for presentation purposes, but very similar or even identical
results have been seen from tens of tests around the world.
Typical testing environment
The selected testing environment
included in all conducted tests contains the following set-up:
Each vehicle was equipped with a
Multi-Channel Router (MCR) with selected available main operators in each case.
A laptop or a tablet was attached to the router. The router created a Mobile IP
tunnel to a server in the cloud and from there the connection to authorities’
back-end systems was created.
We wanted to test against the
clarified customer claims. The first claim was that one network operator is
enough within cities. The second was that out in remote regions there is no
coverage at all.
Cities
We first present the results
from using the hybrid network approach within selected cities. The cities
included here are Brussels, Antwerp and Los Angeles. The test duration for each
of these tests is several hours - long enough to give a clear picture of real
life operation of the networks within the given cities.
As is clear from the example,
the network availabilities of individual network operators are far from the
100% claimed. Over just a few hours there may be more than 50 data
interruptions. It is similarly clear that multiple networks overlap favourably.
The joint coverage with just two operators is always close to 99.5% and often
close to 99.9%.
What is also important is that
the bundled solution practically removed all longer breaks that would have
caused the user to feel an interruption to the service. Looking at the GPS data in heat
maps gives a clear visual representation of the fact that the networks are full
of holes when it comes to delivering broadband to moving vehicles, even in
densely populated cities.
Remote locations
For remote location testing we
selected a third network to ensure we get the maximum coverage. Only in Iceland
did we use two networks due to fewer available operators without network
sharing. We always try to select networks that have as little coverage overlap
as possible. The locations tested include are some of the most remote in
Europe, including Ireland, Norway and Iceland. The results were surprising.
It is understandable that single
network availabilities are significantly lower than in the cities. But
surprisingly they still are very seldom as low as 80%. The number of service
interruptions increases with lower availability and it was noted that some of
the breaks extended from tens of second to minutes and even tens of minutes when
driving. Despite much lower individual network availability in these areas, the
bundled uptime results were excellent. Over 99% is an excellent figure
considering the places where these test routes were driven. Places so sparsely
populated that there are often no inhabitants within a radius of tens of
kilometers.
Even in these remote locations,
the bundled solution offered uninterrupted connectivity as any longer breaks in
data were reduced to zero. The user did not experience any interruptions to the
service, even when some short breaks in the data stream occurred.
Availability heat maps show
clearly how multiple networks combine to provide the high availability
encountered.
Summary
Anecdotal evidence and personal
opinions are especially misleading in this area without accurate data regarding
mobile broadband data coverage. Typically individual opinions have been
influenced by personal experiences and are further confused by operators
marketing messages. The discussion around the need for dedicated broadband
networks is manufactured to some degree by the equipment providers themselves.
Opinions that are not backed up by real data and test based findings should not
form the basis of decisions made in this area.
In every test made, several
parallel networks have been proven to provide greater resilience than a single
one. Tests conducted in various locations across the US and Europe prove two
crucial points. The first is that no city can provide sufficient broadband
availability for public safety vehicles over a single network. The second is
that even the most remote areas can provide availability that is acceptable for
public safety mobile broadband.
It is worth noting that similar
tests are always needed in a new region in order to form valid conclusions. Of
the tens of tests conducted so far, all have yielded very similar results
regardless of locations.
Mikko Kestilä and Juhani Lehtonen
Goodmill Systems Ltd.
Hello, thank you, it's interesting.
ReplyDeleteFew questions I have as I dealt with it my self in the past:
What is the net throughput you have received per vehicle?
Did you test it with video application where Latency & Jitter are imperative for high quality video on the move? (what were the results)
How do overcome the issue of network shut down in emergencies (such as suicide bomber) sue to network overload - especially where the Police, EMS and Fire need the connectivity?
Last question: throughput in cellular is not guaranteed as it is subject to the number of users in the cell and to the proximity to the BTS - how do you provide SLA in these terms?
Appreciate your response.
Jim.
Hi Jim,
DeleteFirst: The troughput varies. We got anything from edge in very remote locations to LTE speeds of over 10 Mbit/s in the best locations. In many cases the continuous connectivity is more important than huge capacity. In some instances the connection was lost also for short periods of time, but the user didn't notice it.
Second: Yes we tested with demanding online applications like webex and also video. Our approach of proactively selecting always the best network seems to be the right way to handle this. Bonding various networks creates too much latency and other problems when in these extremely dynamic environments.
Third: How to deal with congestion? This is a million dollar question. What we've seen is that sometimes the router solution that keeps all the networks "active" reserves capacity from the networks and functions despite other users have problems. But sometimes the networks crash. Then the question is. what is the alternative? Use satellite (we support this) or build a dedicated network in the area rapidly. But also P25 and Tetra get congested and the officers still need to be able to operate. Don't hesitate in investing into broadband connectivity only because there are rare occasions when it might not work.
Fourth: I partly answered with congestion to this. One can prioritize traffic classes or port level in our solutions. It is also possible to do by the operators already in 3G, but it is never implemented. LTE will provide better possibilities for this. Prioritization will remain the question between the users and the network operators.
So. Good questions. I have the feeling that the best thing to do is to start with these type of solutions that are cost efficient, but maybe not perfect. Using broadband will help us to find the actual killer applications and eventually we'll also learn about the anticipated problem situations, too. These systems have been in use in Finland already for 3 years and implemented nation wide. The users are still extremely happy despite occasional limitations.
Hi Juhani,
ReplyDeleteAppreciate your reply!
From your detailed answers I gather these systems can work nicely for non-mission-critical applications that require the bandwidth but not really need the SLA (minimum bandwidth for mobile applications such as Video/VoIP regardless to other users in the cell) nor to operate in emergencies (such as one that impacts the cellular networks operation).
BTW, some companies claim that networks aggregation works well but I am not in the details to understand the impact on latency.
And last, In case there is a need for true private wireless broadband network which is immune against cellular network interferences or shut down, it is required to use a sub 6GHz wireless network that supports mobility. It requires Capex obviously...but the turn out would be SLA, high bandwidth and full control.
Hi Jim,
ReplyDeleteThanks for being active!
The system is used also in mission critical applications and traffic can be prioritized to some point. It's used in thousands of public safety vehicles continuously in various applications. It's often a question of "define mission critical", because no one can count 100% on having data connectivity with any system. Also tetra and P25 have big congestion problems at larger events.
Aggregation has big challenges with mobile applications, since the networks behave so dynamic. And aggregation usually provides N times the lowest available bandwidth. As an example: if one network falls to Egde, you get N X edge. Despite that you might have one of the networks at LTE (10 + M). You loose one of the connections when driving around all the time that means that you needs to re-establish the aggregated connection all the time. Doesn't work well, in my opinion.
My message is that it's surprising how good, resilient and high availability data connectivity you can get by using the commercial networks smartly. The seamless switch over to always the best networks is a great and beneficial feature. No one should wait for the dedicated networks to start with the implementation. As the dedicated networks emerge, one can easily upgrade the routers with the suitable network card. Is the multichannel approach 100%? No. Is it good enough for 99.99% of time? Yes I think so. Can it improve the efficiency of pour public safety servants? Definitely a lot.