CARC MEETING 29th June 2011
By Dr Andrew Gillespie Technical Director Thales CommunicationsReliable networked communications to maritime platforms represents a significant technical challenge. Dr Gillespie’s presentation focused on the problems faced in providing Web Services over low bandwidth, intermittent bearers such as HF and V/UHF radio.
Andrew began by outlining the background to HF communications and its present needs in military and professional applications. Historically HF communications has been widely used by military, commercial, government, aid and relief organisations. However, the end of HF as a usable technology has been forecast for many years. The advent and growing usage of satellites at one time seemed to further hasten the demise of high frequency communications. To misquote Oscar Wilde “news of its death is greatly exaggerated”.
For all its long distance capability HF is susceptible to noise, interference, ionospheric variabilities and disturbances and other limiting issues that are not present in satellite communication. However, the major drawback of satellite for military comms is cost. Satellite time and bandwidth are expensive, and alternatives are needed to provide a common platform for member states, in NATO, for instance.
For some years there have been other alternative HF networking protocols in use. Some of these rely upon Automatic Link Establishment (ALE ) using the FED-1045 or MIL-STD 188-141B standard protocols. ALE uses anti-collision methods, multiple channels, and channel occupancy checking to avoid interference in multi-user HF spectrum. If one channel is busy, it moves to another one until it finds a good one.
Within the military environment any alternative system must be capable of interoperability across the organisation(s), and this requires agreement of technical standards. Within NATO STANAG is the NATO abbreviation for standardization agreement, which sets up processes, procedures, terms, and conditions for common military or technical procedures or equipment between the member countries of the alliance.
Each NATO state ratifies a STANAG and implements it within their own military. This provides common operational and administrative procedures and logistics, so one member nation's military may use the facilities - stores and support for instance - of another member's military. STANAGs also form the basis for technical interoperability between a wide variety of communication and information (CIS) systems essential for NATO and Allied operations.
The NATO standard STANAG 5066 is used extensively for HF military, government and commercial data communications. STANAG 5066 is a NATO specification for running data applications over HF Radio. Operating over an HF modem STANAG 5066 provides an interface for data applications to use and share an HF modem. It provides core data link services to enable applications to operate efficiently over HF radio, and specifies a protocol that enables a clean separation between applications and modem/radio level.
Over time the expectations of immediate results have already been realised by the Internet and mobile phone technology, where the press of a button brings instant information and communication without any need for operator intervention, knowledge or experience. HF radio has traditionally relied on the knowledge, experience and skills of operators to select optimum frequency, data rate and other parameters to optimise link performance. Any viable modern HF system must de-skill the operation: thus operation to the user seems fast and automatic.
This was a most interesting update on modern data comms from a military/defence perspective and, given its many complexities, was presented in an easy to understand way.
John Longhurst G3VLH
