Don't Get Cut Off
Brabourne Communications' Simon Hugessen warns UK industry has become complacent as it has become used to reliable wired and wireless communications networks. These networks rarely fail but few understand how little resilience is built in to the landline and the GSM networks
UK businesses and other organisations are more dependent than ever on the ability to communicate effectively. This applies locally, regionally and nationally. In Manchester, for example, in March 2004 a single tunnel fire took out two main BT cables and cut off 130,000 telephone lines, plunging a large area of the city into a communications crisis for both public and private users. It would appear that no resilience had been designed in to the system.
Unfortunately, experience has shown time and time again that reliance upon a single system exposes vulnerability to the unexpected. This was starkly demonstrated when in April 2002 when about 400,000 people living in Hampshire lost all 999 emergency services when the main public telephone exchange at Southampton failed. Although each service (including Hampshire Fire Brigade) thought they had resilience built in to their systems, this proved not to be the case. Because all the emergency services relied primarily on the same type of connectivity they all suffered the same result. The police provided the only emergency communications available during this period via their independent VHF system for motorway traffic cars. These were deployed to key points and provided a limited level of communication and coordination during the crisis. In short, the only Plan B was of limited use.
Since the Madrid bombings and subsequent terrorist attacks in London, communications networks which are not affected can still be commandeered by the security services or even shut down in the case of the mobile phone networks due to the risk of further detonations via these systems. In either case commercial organisations are left without a means to inform their own staff of the local situation and are therefore vulnerable to further attack. In Louisiana following the hurricanes even the satellite networks became unusable due to congestion as this was the only method the public safety authorities could employ.
The Solution: Private Mobile Radio (PMR)
Private Mobile Radio can offer a very effective solution to the problems outlined above. This is because PMR systems are directly under the control of the owner of the network. Networks can be as small or as large as required and provide a wireless communications capability either within a building, around a site or across an entire city. There are various types of PMR system available and they each provide benefits which can be tailored to the users' requirements. In all cases radio is generally used to allow user or work groups to communicate whilst mobile. This 'all informed' method of communicating can be ideal in an emergency as all users are kept aware of the situation as it develops.
To make the radio network even more effective various signalling techniques can be included which allow different users groups to communicate amongst themselves, or indeed to allow just two users to communicate with each other. A typical system might have managers and supervisors sharing one group with another group where everyone is a member. In addition radios can be configured with specific features to improve safety for personnel. This might include Lone Worker, Man Down, Emergency buttons, Priority calls, encryption and scanning, amongst others.
Below is a basic description of the current systems available and the future technologies which are under development.
Conventional System
A conventional system is the lowest cost method of communicating with a wireless device over an extended area. Generally speaking a repeater or repeaters are employed to extend the coverage area. In these systems the users simply activate their radio by depressing the Press To Talk switch (PTT) and transmit to either another user or to a group of users if selective calling is configured. The coverage area will be determined by the power of the repeater transmitter and the antenna height and type.
Quasi-synchronous System
This system uses several repeaters located at different sites where the coverage areas overlap thus creating a number of cells. Radios move from cell to cell and the system recognizes the signal strength measured at the mobile radio and allocates the best repeater accordingly. This type of system allows re use of the same frequencies and is ideal where a large geographical area needs to be covered and where there are few available frequencies.
Trunking
Trunked radio received its name from the 'trunk line' which is used in commercial telephone communications. Put simply, a 'trunk' is a communication path between two or more points, typically between the telephone company central office and one or more users. The trunk line is time-shared by several different users, but users of the telephone service do not need to be aware of this sharing. One party places a call to another party and the call is completed; the internal working of the telephone system is transparent to the users.
Radio communication over a trunked system is quite similar to such telephone systems. The transmitting and receiving radio units can be thought of as the calling and receiving parties, and a trunked radio system can be thought of as the telephone company equipment. Instead of telephone lines, the radio system uses radio channels to place calls. As with the telephone system, the radio users are not aware of which particular radio channel they are communicating over. All that is apparent is that a communication path has been established between the users.
Trunking a multi-channel radio system increases the efficiency of the radio system by dynamically managing the use of a radio channel. This is accomplished by the computer control of radio channels and the virtual elimination of the delay experienced by field units in obtaining a clear radio channel.
TETRA
Terrestrial Trunked Radio (TETRA) is a set of standards developed by the European Telecommunications Standardisation Institute (ETSI) that describes a common mobile radio communications infrastructure throughout Europe. This infrastructure is targeted primarily at the mobile radio needs of public safety groups such as police and fire departments, utility companies, and other organisations that require voice and data communications services.
Based on digital, trunked radio technology, TETRA is the next-generation architecture and standard for current, analogue PMR users. TETRA incorporates features from several different technological areas including mobile radio, digital cellular telephones, paging, and mobile wireless data. TETRA-based products come with built-in encryption features to ensure the privacy and confidentiality of sensitive data and voice communications. These products are also designed with the ability to transfer data at faster rates than seen before in mobile communications.
Designed primarily as an emergency communications system TETRA is slowly becoming available to commercial users and should certainly be considered when deciding to implement an emergency communications network.
Simon Hugessen
Managing Director
Brabourne Communications Ltd.
www.brabournecommunications.com
