Aug 12, 2014

Hybrid Mobile Network Use in Public Safety Vehicles

The recent hot potato in the public safety discussion has been mobile broadband data. The question of how to bring the broadband to public safety vehicles has multiple opposing viewpoints and conflicts of opinion.

The first answer to implementing broadband into vehicles is to build dedicated networks for authorities. The second solution is to use a commercial provider with special deals to offer the data capacity required. The third option includes several hybrid solutions, either combining dedicated and commercial networks or using multiple commercial ones.

Tests conducted in various locations across the US and Europe prove that hybrid commercial network use is a viable solution that can be later improved by adaptation of dedicated networks. This observation has already led to implementation of a fully commercial network based solutions in Scandinavia. The fully commercial solution does not limit the usage of dedicated networks like FirstNet, but due to lack of frequencies this has been the only way in many countries so far.

The key element of this solution is a managed multichannel router system. This system enables easier, secure sharing of confidential information. It is now possible to call up a suspect’s criminal record, any outstanding/previous fines or even vehicle information. With this approach, all the needed office tasks can be performed on the spot, while required documents can be created and printed immediately.

Users claim that co-operation has been elevated to an entirely new level. Information is more transparent thanks to task handling, shared blogs and the collection of statistics. The reliability of data transmission and sharing of critical information has and continues to improve significantly. Misunderstandings are reduced because different patrols can now locate each other from a shared map resource. This has led to gains in the command and control chain, with field management proving more efficient thanks to better allocation of resources.

Authorities have been extremely satisfied with presented system. Routers have changed and continue to change field operations and management due to provided capabilities for new applications. Also the addition of a dedicated LTE network to the solution is possible whenever a new networks is implemented giving also a future proof solution. It has been already shown that this technology saves time, resources, money and lives.

Juhani Lehtonen
VP Sales and Marketing
Goodmill Systems Ltd.

Apr 14, 2014

The Reasons Why Link Aggregation Does Not Work for Public Safety Mobile Broadband

The use of commercial networks in public safety has been a hot topic recently. Many countries have introduced concepts to offer public safety connectivity with variable results. One hot topic in how to use commercial networks is to utilize multiple networks at the same time. The reason for this is a natural reasoning since one commercial network occasionally has capacity problems: let’s combine many to always provide a good broadband solution. However, this reasoning lacks the understanding of the basic functionality of how mobile networks function. This misunderstanding has led to bad results in tests and occasionally to abandon the concept of using commercial networks for this critical user group.

What is it we’re talking about, really?

First it is important to understand the terms. We need to differentiate load sharing from link aggregation or “bundling” as often referred to. 

Load sharing sends different data streams to different WAN links and “balances” the load between the links. It either sends always different types of traffic to different links or works with and “water flow” principle when one link is full using the second one. The problem with this is that the data sharing is application based and individual application cannot be distributed over multiple links. Usually only one application, live video streaming requires the capacity that would need multiple links. This problem cannot thus be resolved with lead sharing.

Aggregation or bundling builds one “big pipe” of data over multiple links. This enables all individual applications to treat all combined links as one. The challenge comes from when one link is cut off; the whole aggregated frame needs to be built again. One big hinder in this solution is the extremely dynamic nature of mobile data networks. Aggregation can with current technology only give always only X times the worst link capacity, X being the amount of links!

Let’s look at these challenges more closely.

Challenges with load sharing or load balancing

The first challenge is to consider what is the criterion to share the load? Are we just having two times normal links with separate and dedicated data for each link? Or are we using some kind of “water fall” approach with filling one link first and then directing the overflow to the other links? With dynamic mobile networks in moving vehicles the network throughput capacities change constantly. To suit the correct amount of traffic into each link and then changing traffic between links when capacities change create problems.

With load balancing approach it is impossible for any router to share the traffic over multiple links unless you have multiple VPN tunnels. IP address - based load sharing would then only be possible with multiple VPN’s and the solution would be limited to “best effort” type use.

Most importantly: if an application demands more that the primary link, it cannot be shared. This means that live video streaming would not work. For live video streaming the aggregation would be the logical solution.

Challenges with link aggregation or bundling

Link aggregation enables capacity sharing over all links.  The joint delays are always at least at the level of the worst link used.  All link interruptions need a new build for the whole frame and this would need to happen all the time, even hundreds of times a day. This creates even more delays since the rebuild of the frame needs time. It is common to have some kind of a connectivity break in any network every few minutes over any of the used links. 

The rebuild of the aggregated stream is always depending on the latency of the worst link and it is thus very difficult to use interactive communication like VoIP or video conferencing due to continuous and frequent delays. The ITU standard defines the minimum one directional latency for voice to be at the most 150 ms. This can very seldom be reached with network interruptions in aggregated solutions. Additionally aggregation always needs a dedicated back-end system that can be very expensive due to large number of needed logical ports.

What is then the best solution?

Let’s consider the possibility of having a system where the link quality is always tested and the best available link would always be used. This would mean following capacities.

Fast switch from network to another in this case provides always better capacity than link aggregation. The similar would apply to load sharing, since the allocation of capacity due to very dynamic environment disables the allocation to its full extent. 

This means that one demanding application, like live video streaming cannot be used over load sharing over multiple links and the framing of the aggregated data stream creates delays and cannot utilize the best capacities of the available networks. There is evidence that supports this statement. With a test in Scandinavia a solution with 5 aggregated 3G links was able to give only 700 Kbit/s capacity despite the existence of 3G networks. If any of the links was occasionally using Edge capacities, this would mean 5 X 128 Kbit/s approximately. Simultaneously there is several HSPA+ or even LTE networks available with multiple Mbit/s over any single link! A suitable option would thus be something like presented in the picture below. 

This scenario requires a capability to monitor the link quality and cautious proactive switching between networks. The first tests of this approach have been leading to implementations with high-end applications like VoIP and live video.


Modern networks are developing and growing fast and the capacity over one link is often tens of megabits per second generally. This is enough for all current modern applications including live video streaming, VoIP and combinations of these. Using multiple networks with always selecting the best one gives very short delay times. With quick switch over from network to another one can reach the best overall link quality, availability and resilience. Load sharing and aggregation seldom meet the requirements for public safety mobile broadband data. Proactive selection of best mobile link is thus currently the Best in Class solution for applications that demand uninterrupted broadband connectivity.

Juhani Lehtonen

Mar 17, 2014

The Pilot Results of Hybrid Commercial Network Usage in Public Safety Mobile Broadband

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.


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.


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.