Cobham Surveillance COFDM Digital Video Products
Benefits of Digital Transmission
The migration from analogue microwave systems to digital transmission offers several key benefits to users:
Better Performance
By using digital modulation and compression techniques, digital microwave provides superior performance in non-line of sight and high multipath applications. Unmanned Ground Vehicles operating in buildings or urban environments, as well as low flying Unmanned Aerial Vehicles, will be able to transmit dramatically clearer video with less break up to remote receive stations. Covert surveillance cameras no longer need to have a clear line of sight to the receive location to have good picture quality. Unlike analogue, digital video picture quality is noise free regardless of distance.
Efficient Spectrum Utilisation
Digital video systems operate in a fraction of the spectrum utilised by typical analogue transmitters, offering up to 8 digital video streams in the spectrum previously used to transmit a single analogue channel. Cobham SOLO products support 1.25MHz or 2.5MHz channels in the narrowband configuration or 6-8MHz channels in the full DVB-T compliant configuration. This compares to up to 25MHz for a typical analogue channel.
In addition, digital channels can be located adjacent to each other without a guard interval. Analogue systems tend to bleed over their allotted spectrum, requiring several Megahertz of separation between channels at a minimum. As regulatory agencies worldwide reallocate spectrum, it’s clear that digital transmission enables more users to co-locate channels in an increasingly crowded RF spectrum.
Secure Transmission Using Encryption
Digital transmission enables the secure transmission of video by using AES128 or 256 bit encryption. There is no penalty to the user in terms of performance. Analogue systems don’t offer this capability as a feature. Analogue “cut and rotate” encryption modules are expensive, often doubling the price of a system, and not nearly as effective in securing the video data stream.
In addition, they add to the size of both the transmitter and the receiver. Digital offers true encryption with no additional size penalty. In the case of the Cobham receiver, AES encryption can be carried on over the IP network.
Set up for Internet Access
Many customers are looking at how to access their video from anywhere, at any time, over the internet. Digital transmission makes it easier to send data over the internet, avoiding the need for a separate analogue-to-digital conversion. Cobham receivers have been designed to offer internet connectivity by means of an optional TCP/IP Ethernet network interface, accessed via a convenient RJ45 connection.
