Johannesburg, 23 Sep 2015
As more high frequency Ka-band becomes available, it is becoming more affordable than the low frequency C-band satellite offerings, optic fibre and dedicated Diginet lines for the transmission of video from a remote location to a studio, says Mark Chertkow, Managing Director of Graphic Image Technologies (GIT).
What makes it attractive is the arrival of technology like Video Flow's Data Video Protection (DVP) solution, which reduces IP packet loss and jitter, making transmission of larger data streams over a group of small Ka-band IP connectivity links possible.
Traditionally, video contribution (the uploading of video footage to the studio) has been done on a 'point-to-point' basis via satellite. With the introduction of the Internet Protocol (IP), broadcasters and production houses have had to make use of high-cost high-speed Internet connectivity or dedicated links. They are now considering Ka-band technologies that reduce interference and increase coverage, capacity and speed (e.g., steerable beam and regional beam technology) emerge. Video Flow's DVP technology is a leader in this category.
VideoFlow's DVP solutions integrate with satellite data channels, keeping delays under the maximum two seconds tolerated by live broadcasts. It does this by using error correction, a unique on-demand packet recovery technique that minimises bandwidth overhead.
The VideoFlow DVP's server-side Protector stores the packets until it is certain that they have been correctly received, while the client-side VideoFlow DVP Sentinel monitors the health of the video stream, watching for packet loss and requesting that packets be resent from the Protector's cache only if required. This not only ensures a user good viewer experience, it also cuts use of satellite bandwidth.
Why Ka-band?
The launch of more Ka-band satellites, such as Inmarsat's Global Xpress which became fully operable in 2014, is making more high frequency, high-speed satellite capacity available globally. It has raised some debate in the broadcasting industry: which is better - C-, Ka- or Ku band; and how can it be used to good effect? The short answer: new data video protection technology makes Ka-band an effective and affordable solution for live video contributions.
Comparing C-, Ku- and Ka- bands
How do the bands compare and what are the challenges specific to each? In brief, the lower the frequency (as in the L- and C-bands at 1-2 Gigahertz (GHz) and 4-8GHz respectively), the more desirable the bandwidth and the more expensive it is. These low frequency bands also have a longer wavelength, therefore require larger sophisticated antennas. The robust C-band is typically used by TV broadcasters for backhaul and contribution feeds as it is resilient to 'rain fade' but also requires a larger dish (as it operates at a lower frequency).
In the lower reaches of the K-band, the Ku-band (12-18GHz) is typically used for Direct to Home (DtH) satellite TV transmission. However, as radio frequency signals above 11GHz are absorbed by atmospheric rain, ice or snow, Ku-band signals are subject to rain fade. Ka-band, which operates at a higher frequency than Ku-band, is therefore subjected to most interference and has typically not been used in video applications.
The Ka-band, which functions in the upper reaches (26.5-40GHz) of the K-band, is even more susceptible to rain fade and has in the past been considered "junk" bandwidth by broadcasters. Very little jitter and latency can be tolerated with live video streaming. Broadcasters are reviewing their options, however, as more Ka-band becomes available. Although typically considered unusable for high bandwidth applications video flow enables the use of video over this typically poor connectivity.
Satellite transmission capacity is increasing rapidly and there is much opportunity for broadcasters to improve processes and communications capabilities. The Ka-band and DVP solutions can offer significant benefits in terms of convenience, cost savings and increased competitiveness. It is a consideration many broadcasters find increasingly attractive.
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