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British Army

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British Army - Case Study

British Army

"My sincere thanks for your professionalism and what I can only describe as excellent customer support" - Lieutenant Colonel M Lansdown TD R Signals

The 36 (Eastern) Signal Regiments role in providing communications support to UK Operations has been considerably enhanced by having CASBAH available and fully operational in its new role....

UK Armed forces utilise a packet based line-of-sight microwave radio system known as Casbah. Easily deployable and commonly housed in the LandRover Defender. The radio mast, located on top of the LandRover, can be raised to establish point-to-point communications to another Casbah mast over distances up to 40Km. The benefits of this system are that forward operating bases can be quickly established enabling communications back to a regional command facility.

The interface into the radio system is a standard 100Mbps Ethernet interface. A cryptographic device is also used to ensure all communications are encrypted. Currently the system is used for data only. The customer has identified the necessity to add voice capability and also the desire to significantly reduce the complexity of adding new data clients as the restricted availability of technical staff has reduced the flexibility of the system.

The Challenge

Two core issues were identified that needed to be overcome:

  1. The microwave system is packet based, fine for data applications, but the voice PBX's were TDM based and the interface requiring back haul was a 2.048Mbps DPNSS trunk.
  2. Due to the way the cryptographic devices operated, traffic could only be routed between Casbah locations and this led to complexity in the deployment of data clients as very often only non-technical staff were deployed.

The Solution

Firstly, to successfully back haul the TDM based voice traffic a method of encapsulating this in IP was required. By using PacketBand 'TDM over IP' equipment it was possible to connect the PBX's over packet based Casbah. PacketBand offers highly accurate clock recovery to provide stable transmission of TDM services over packet based networks.

Secondly to overcome the complexity surrounding the routed network it was identified that if all traffic could be bridged, or in other words, remote data clients made to look as if they were part of the same network as those on the regional command location, then the complexity of deploying remote clients would disappear.

As the cryptographic equipment could only route, an advanced VPN device was installed at each location. This VPN device, (the RP450), created an 'Ethernet over IP' tunnel between the 2 Casbah locations and effectively joined the 2 networks together allowing Ethernet traffic to be bridged over the routed microwave link. This is reflected in the diagram below:

MOD IP Microwave schematic

The Results

Capability of Casbah has now been increased to provide the ability to make voice calls. The deployment of remote data clients is also now a simple matter with zero additional configuration. In summary the Army now has a 'plug and play' system for the back haul of both encrypted voice and data over Casbah.