LTE Small Cell networks could support multiple public safety organisations

first responder 150There are many different public safety radio networks used by multiple first responder services today – fire, ambulance, police etc. In the US, each may have its own frequency (VHF or UHF) and dedicated handsets. Europe has adopted TETRA, a common standard similar to GSM. One problem with these specialist systems is that the relatively low volume of product means they are expensive and new features are developed slowly. Handsets can cost $3,000 yet provide basic voice and text only.


Today, a police officer's mobile device seems very basic compared to the criminal's (iPhone/Android/insert your favourite smartphone model here), leading to them using a mish-mash of different private and public wireless systems.

Many police and other vehicles use IP data services connected through the regular mobile network alongside their dedicated handsets. Cisco documented this in a case study with Zurich police.

A major disconnect

This was clearly highlighted after the 9/11 disaster in New York, where many fire and rescue services from adjacent states came to help. The trouble was they couldn't communicate with each other because of incompatible radio systems. The administration mandated change towards a common, interoperable standard. LTE is almost certain to be that common radio interface, but each service would like to retain control of who can access and use the system. Spectrum in Band 14 (700MHz) has been allocated in the US for this purpose.

In Europe, the TETRA system is considered very expensive. The UK government alone spends some $500 million each year running the system. Terminals offering basic voice and text can cost several thousand dollars each. 3GPP are adding features into the LTE standard to ensure it can match those of TETRA, while benefitting from the low cost of mass deployment.

Sharing the public safety spectrum

Typically the issue isn't about capacity – we only have so many first responders who would use the system. It's about coverage and limiting access only to those really need it. That means sharing networks both outdoors and in.

First responder organisations have been used to operating their own local radio networks, with their own towers, radio transmitters and dedicated spectrum. With LTE, each organisation still wants to retain the ability for access control, have their own core network and provision their own SIM cards.

Rajesh Mishra, co-founder of Parallel Wireless, an LTE small cell startup believes that MOCN (Multiple Operator Core Network), a 3GPP standard feature, would be an ideal method to achieve this. LTE radio networks can be directly connected through their gateway to many different Core Networks which could separate out fire, ambulance and police network access. Each would be managed directly by its own department. A small city might support three independent LTE core networks (EPCs) and there may be many more across a US state.

Their LTE Access Controller has been designed to allow it to filter and route signalling messages to the appropriate EPC, based on IMSI (SIM card number). There's no real limit to the number of different EPCs that could be connected.

In-building solutions

US legislation requires that all new buildings constructed must ensure provision of public safety service. With thermally efficient building materials being used (LEEDS specification), penetration of outdoor RF signals can be severely attenuated. Workarounds include installing active or passive DAS systems which act as repeaters for the outdoor VHF and UHF first responder networks.

As these migrate to LTE, using Enterprise Small Cells with MOCN may be a lower cost alternative. Rather than operating on Band 14, these would use the network operator's regular LTE spectrum within the building, giving priority where required.

Some are concerned that regulators might mandate stringent demands for continued operation despite power failure, requiring costly battery backup and fireproof cabinets. My view would be that if the building has burnt down that badly, the backhaul connection and/or other critical elements would probably also have failed. It would seem better to consider alternative options which include coverage from any existing external macrocells and nearby urban small cells.

Instantly deployed LTE networks for emergency use

Ranberry B1000First responders need the ability to setup their own temporary radio networks at the site of any incident, however remote or uncharted. The ability to do that quickly and efficiently brings many advantages.

You're probably familiar with the term COW (Cell on Wheels), entire mobile basestations on trucks or trailers that are deployed by network operators for major temporary events such as festivals, outdoor sporting events etc.

Imagine if the COW could be carried onboard emergency vehicles, so that the fire engine or police car can setup a local network at an incident within minutes? Small cells already provide the technology do to that quickly and at low cost. Such capabilities are also of interest for military and remote commercial operations (e.g. mining).


  • The transition from older technologies used by first responders, both proprietary VHF/ UHF and standard TETRA, towards LTE in inevitable in the medium to long term.
  • Small cell LTE gateways and MOCN enable a method of sharing common LTE coverage with first responder organisations, permitting them to have their own core network services and full access control.
  • Portable LTE small cell networks designed specifically for first responders could radically improve communications at major incident sites


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#1 Mo Nubar said: 
I'm interested to know whether it's possible to design an emergency lte cell that will accept connections from all GSM or LTE phones in the area, regardless of usual carrier, without needing a backhaul.

I'm thinking this could be useful in a disaster context (esp. conflict) where the usual mobile network is down. Phones connecting to the cell could receive a welcome text with vital information (like location of operating hospitals) and receive further emergency SMS broadcasts.

It would be amazing if such a tool could also allow phones connected to the cell to communicate with each other, even if they can't get calls onto the main network.

Is such a thing even possible?
0 Quote 2018-02-25 21:24
#2 ThinkSmallCell said: 
@Mo: Actually this is standard behaviour for all GSM and LTE cells, both large and small, and part of the 3GPP specifications. Even if your SIM card is from another network operator or your credit has expired, you can always make an emergency call and this will take priority over other non-emergency users.

For service in major incidents, where the cell tower networks are not operating, we now have rapid response vehicles which can instantly provide coverage using satellite other other backhaul service. This restores service not just to one operator but would also re-enable emergency calls for all.
0 Quote 2018-02-27 13:53
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