Dec 04 2020

Ka Band satellites have eliminated any rain fade disadvantage

By Marcus Bicknell

Both terrestrial point-to-point and satellite transmissions are subject to attenuation of anything which gets in the way… it’s not just satellites which are affected. Rain fade is sometimes cited as something which can reduce the signal strength at the reception equipment. Indeed, without a well-thought-out link budget, including the diameter of the dish, bad weather can have a negative influence on any terrestrial or satellite transmission.

I have direct experience of the polemics surrounding satellite reception and the way in which competitors falsify the technical issues to take advantage. In the three years leading up to the 1988 launch of the world’s first commercial television distribution satellite SES Astra in Europe, critics from our competition and from “technical experts” everywhere claimed that the recommended 50 cm dish would not be able to receive a proper TV signal and that any rain would cause an outage. They were claiming 75cm to 1.2-metre dishes would be needed in Astra’s 52 dBW footprint. I was the Commercial Director of SES Astra from 1986 to 1990 so I took on the responsibility for weathering the storm (excuse the pun) of unjustified fear-mongering in the media. As soon as the satellite was up, our engineers were proved right. Reception on the small dishes was perfect, with rain interferences measured in minutes per year and sometimes insignificant to the viewer. The critics disappeared, licking their wounds.

How did we know the 50 cm dish would be enough? SES Astra engineers with the support of consultant experts worked on the whole chain of transmission (the “link budget”) from studio to uplink to satellite and down the ground to make sure the reception signal (in EIRP, and ultimately in Signal-to-Noise figures) would give viewers a terrific picture and sound. And so it turned out. Rupert Murdoch’s Sky TV had 5 million homes by 1995 and 24 million in 2020, that’s 83% of all homes in the UK! Technical problems? Of course not. Satellite reception is one of the most reliable and quality media distribution mechanisms.

So why would criticisms of high-speed internet by satellite surface some 35 years later in the Pacific market?

The answer is… competition. Deceitful and selective use of technical data is so easy to put out there. Unfortunately, there is a temptation for any company in telecoms distribution to talk down the competition and exaggerate their technical issues. Satellites vary not only in transmission power but also in distance from the earth (Geo, middle or low-earth orbits), the frequency range used (typically Ku or Ka-band on the downlink), the need to control and hand-over transmission between the myriad of satellites in MEO and LEO orbits (Kacific operates in Geo, i.e. in the orbit where the satellite appears to be stationary and the dish does not have to move) and other characteristics. The manufacturers and operators of any satellite system have to establish their link budget, minimise any inherent technical issues and provide the best service for the customer.

First look at the inherent advantages of a Ka-band 26.5 to 40 GHz system; the satellite operator can extract more bandwidth, which means a higher data transfer rate and, therefore, higher performance and lower cost per MB (www.aidforum.org); good power manageability; narrow beams that are easily pointed to where they are needed on the ground; and narrow beams which avoid interference from other satellites.

It was true in the distant past that Ka-band frequencies if ever transmitted in a raw state, were slightly more susceptible to rain fade than some other frequencies, but engineering experts have been perfecting, for 35 years, the mitigation technologies to ensure a good signal. Independent sources confirm the techniques available, all of which are deployed by Kacific; redundant and multiple gateways, adaptive power control, adaptive modulation and coding (a common tool that uses advanced signal processing algorithms). Yes, install a Kacific dish and receiving equipment and get a big, fat, reliable high-speed internet signal.

WorldTeleport.org confirms “Ka-band ground terminals are installed throughout the world. The original Advanced Communications Technology Satellite (ACTS) protocol of 1993 confirmed the feasibility of Ka-band for satellite communications. This powerful spectrum has proven to be the most effective platform for high throughput communications (HTS), in spite of the original concerns over rain fade.

Viasat.com, probably the most successful US data satellite operator, agrees. “High capacity satellites, combined with a more technologically advanced ground segment are able to overcome the challenges (of weather attenuation). The mitigation techniques including adaptive power control and adaptive modulation and coding as well as gateway site planning, are powerful tools that can effectively mitigate these fades.

The International Journal of Microwave Science and Technology says “different techniques in a combined approach make the Ka-band spectrum fully available for broadband satellite applications and network-centric systems.

Would you like to discuss the inherent problems associated with MEO, LEO, Ku-band or other satellite types? No, let’s not bother. They can fix their technical problems themselves. The proof of the pudding is in the eating. Ka-band is a world standard providing robust data transmission when the system is engineered properly, and minimal rain fade. Thousands of large-scale telcos, ISPs, businesses and governmental institutions have been using Kacific with perfect results since the first Kacific satellite was operational in early 2020.

Marcus Bicknell is Senior Marketing Advisor to Kacific Broadband Satellites; he was commercial director of the world’s first privately-funded satellite operator SES Astra from April 1986 and was a Non-Executive Director 2005-2018. The views expressed in the article are his own. 

Connect with Marcus on LinkedIn.

This article was originally published on 14 September 2020.

Sources:

https://www.worldteleport.org/news/444948/The-Propagation-Impacts…-on-Ka-band-ground-terminals.htm

https://www.viasat.com/sites/default/files/media/documents/mitigating_the_effect_of_weather_on_ka-band_high_capacity_satellites.pdf

https://www.hindawi.com/journals/ijmst/2012/791635/