Most of the current public safety broadband challenges can be tackled by smartly using not one, but several
existing networks. By combining readily available networks the
access can be improved significantly, the reliability and resiliency is not of
a single network, but of an independent combination. Availability and quality
of service are what the operators can jointly offer. The network infrastructure
providers will naturally develop the spectrum efficiency to maximize the
efficiency of their network and roaming could be provided between networks,
using the best one available.
What do these combined networks
then practically have to offer? The challenge is the always online connectivity
especially when we are in moving vehicles. The recent studies show sometimes as
low as 70% availability for any single 3G network even in the best coverage
areas.
Table 1. Example of single and multiple broadband network availability.
The usually discussed needed
availabilities for dedicated PS broadband are at the level of 99%. It is clear that
providing that kind of availability over dedicated networks incorporates huge costs
when applied over a larger region. It is understandable that the single carrier
approach that occasionally provides these low availabilities is not sufficient.
Luckily the statistics help with the multiple network approach. With two 3G
networks, as presented here, as low as 64% over first network and 76% over the
second one provide a combined availability of over 99%! Just by using two
networks the availability needed can thus be met. And introducing 3rd
network enhances that even further. When the switch over from network
to another is seamless, one can claim that this approach provides for the
needed technical functionality that is acceptable for critical communications
already today.
The ultimate counterargument is always that there will be situations when none of the commercial networks will function. They can be blocked due to other traffic, there are areas where commercial networks don't exist or power could be cut off. In these cases there remains a need for priorisation, QoS or even dedicated networks. Different dedicated LMR technologies, like TETRA, need to be there as a back up also for data.
There is, however, a chicken and an egg problem here. The broadband solutions are needed in daily operations today. Should we postpone the introduction of broadband data to PS because of possible rare incidents or could we introduce a concept that works now and can be upgraded to meet the requirements of future as needed regulatory decisions are made? I think broadband should be introduced today and upgraded later. But not just any kind of a solution. We need a future proof solution that is capable to meet most of the demands of criticality today!
The solution requires for router equipment in
the vehicle with very special features that are unmet by established router
manufacturers today.
Hybrid Network Approach in PS Broadband
Overall Picture of the Needed Router
Solution
The more flexible the used WAN link configuration is, the
more flexibility, reliability, resilience and security can be provided. The
router solution needs to include a wide variety of links, a top of class
encryption capabilities, fast switch over from network to another and a
possibility to remotely manage and to have an overview of the connectivity. The system needs to be able to
provide seamless services to vehicle that include, but are not limited to:
These services can be used in
critical environment only by using routers that are specifically designed for the
purpose. This includes special hardware, software and management features.
PSS Router Software Requirements
The most important software
feature for the router system is the capability to switch over from network to
another seamlessly, without any service interruptions. Mobile IP tunneling
implemented by few manufacturers is a part of the solution. This technology
hides the network changes from the termination point and enables fast switch
over without unnecessary VPN negotiations. PS customers always use encrypted
traffic, so various levels of VPN tunnels are used by different user
organizations. MIP also guarantees session persistency so that the users are
not required to re-authenticate to their backend systems every time a link is
changed. But MIP cannot handle the fast switch over just by itself.
The mobile networks are extremely
dynamic and having data streams to and from moving vehicles increases the
demands of the connection. The networks are mainly designed to serve nomad
customers and systems that solemnly depend on networks’ routing capabilities
cannot follow a fast moving vehicle. With just protocol based routing the switch
over decision cannot be made quickly enough. The only feasible solution is to
use predefined routes and predict at all times the best possible routing for
any the used links. This enhances the capabilities for decision making about
when the network switch over is necessary. For this very same reason load sharing or data bundling over multiple networks seldom provides any advantage.
The router software requirements
include also the capability of autonomously control the used modems. The modems
tend sometimes to stay in “hanging” mode and look like they are connected to
the network, but no data is transmitted. This and other similar dysfunctions
need to be detected by the router and software needs to wake the modems up.
PSS Router Hardware Requirements
The router market offers quite a few
appliance hardware solutions for router developers. These appliances are not
designed to handle the specific requirements of critical PS communication. The
first needed requirement is flexibility. When the connectivity is introduced to
wide areas, it is often demanded that various routers have quite different
hardware configurations. This is mostly emphasized in the WAN link flexibility.
In many cases two links might be enough to fulfill the criticality demands, but
there are cases where 3 or even 4 links are necessary. These links need to
include all UMTS technologies (3G and 4G), but also capabilities for all CDMA
based technologies and even satellite connectivity.
Robustness of hardware is a must
in these demanding applications. Although the routers are located inside the
vehicles, the shock resistance and IP classification needs to be high. It is
clear that consumer products or slightly upgraded consumer products will not
offer the long time durability required.
Router demands also carrier class
hardware approach when it comes to updating the software. When remote software
update is implemented, the router needs to test it before taking into use. This
requires double memories. There is also needed a software functionality for
fall back to elder functioning version if something goes accidentally wrong.
Sometimes just software based booting of the equipment is not enough. It is
upmost important that the hardware has functionalities to mechanically switch
the power off. This mechanical power switched, controlled by the software, are
one element of a perfect solution for PS. Similar functionality is needed in
the power back-up. The vehicle on battery should be used, but with starting the
vehicle the power to the router should be remained. Special up to 30 seconds
back-up without extra battery is thus needed.
PSS Router Remote Management Requirements
A horror for the PS broadband
user is just a box with no remote monitoring, configuring or set-up
possibilities. The demand is that the connectivity to all routers, even to
thousands of units, should be monitored from a one secure system from a secure
location. The communication between the management server and the router should
not depend on which links are used for the actual network connection and it
should always be encrypted. Software upgrades shall be made easy in a way that
even large amounts of routers can be updated simultaneously. The routers in
themselves should not have fixed IP address requirements for security reasons.
The contact to management should always be initialized by the router. Easy
management interface that can handle the number of routers and does not require
any special coding expertise is needed.
Finally, the status of the routers and
their links including connections, modems and even SIM-cards should be made possible to monitor
over large amount of routers with a simple graphical interface.
Summary
Special purpose router equipment,
a multichannel router, is required in all furture scenarios of providing broadband data to Public Safety. No general appliance based
or originally for consumers developed routers can meet the requirements for
secure always on-line connectivity in vehicles. The solution has special requirements for
software, hardware and remote management. When all of these areas are
considered in the design, the ultimate target of providing critical
connectivity can be met cost efficiently.
As one PS officer who has been using this type of a solution since 2011 put it:
“Multichannel
routing system provides savings in time, resources, money and lives”
This is what a hybrid network approach can provide for public safety today. And with right system the upgrade to future networks will be easy.
