Spectrum conflicts threaten existing services and new technology take-up
This week sees the simmering spectrum conflicts that have existed in Africa boil over as the Global VSAT Forum launches a global campaign to protect the wavelengths used by C-Band operators. However this is simply the most public of a number of conflicts that Africa’s operators and regulators have before them. It is often said without challenge that spectrum is a scarce resource. But all the while Government agencies hog its use (particularly the military) and regulators allow people to buy licensed spectrum without using it for long periods. One operator told us that he had bought spectrum in one country as a commercially pre-emptive action. Russell Southwood looks at how the GVF’s campaign highlights some of these issues.
In a letter to its members this week, the GVF wrote:”The purpose of this letter is to make you aware of a significant technical threat to your business.” The issue for the GVF is that the “extended” C-band frequencies (3.4 to 3.7 GHz) have already been identified by several national administrations for use by new services like Broadband Wireless Access (BWA) and WiMax.
If that were not difficult enough for satellite operators, other administrations are looking to deploy these new terrestrial services in the “standard” C-band frequencies (3.7 to 4.2 GHz). As the GVF’s Martin Jarrold told us:”In countries where WiMax services have been introduced, there have been significant in-band and out-of-band interference issues and services interruptions for satellite ground stations and their related services. We are aware of interruptions which have occurred throughout Africa as well as elsewhere in the world.”
In a precedent-setting decision, Hong Kong’s regulator OFTA concluded that without the implementation of technical constraints (principally geographic separation and the use of LNB filters) -- which would be costly for both BWA operators and FSS users - the deployment of BWA services in the 3.5 GHz band would lead to interference problems in the entire C-band (3.4 – 4.2 GHz), making a wide and cost-effective deployment of BWA systems in a small place like Hong Kong difficult. In the conclusions to the Report, OFTA also noted that these interference problems have been increasingly reported in places outside of Hong Kong.
In addition the GVF is concerned that the ITU-R Working Party 8F has included the 3.4-4.2 GHz frequency range as a potential candidate band for terrestrial mobile services. According to the GVF BWA and IMT services are similar in that they are both characterized by a large number of ubiquitously deployed base stations and user terminals. FSS satellite systems deliver extremely weak signals which are highly sensitive in both the standard and extended C-band frequencies.
The most effective solution to avoid interference from these services is to separate the systems by implementing exclusion zones around existing FSS earth stations. The need for exclusion zones has been recognized by the ITU-R (including WP 8F) and several ITU studies within Working Parties 4A and 8F. However, exclusion zones are impractical in the case of ubiquitously deployed C-band antennas (as such zones cannot be defined) and for C-band antennas at known locations the width of such zones may go up several hundreds of km, preventing therefore the deployment of terrestrial IMT in large areas.
The implementation of exclusions zones would affect both existing service operators and the roll-out of new services. The GVF recommends that operators register their receive-only and transmitting earth stations that operate in the extended and standard C-band frequencies with their local telecom regulatory authority wherever possible, “so that they can be afforded the proper protection against interference”. It is also recommending members present the case against re-assigning C-Band frequencies to BWA and Wi-MAX.
Other spectrum conflicts are also putting in question the roll-out of cheaper, new technologies. For example, Neotel is trying to get spectrum to offer CDMA fixed wireless operation but is being prevented by an existing broadcaster that is arguing that interference will occur.
Africa’s regulators now have the delicate task of sorting out their available spectrum so that it can be used effectively to deliver new technologies but does not disadvantage existing operators. This must put pressure on Government agencies and non-operators of licensed spectrum to justify what they are doing with these resources.
These issues will be discussed at:
2nd West Africa Satellite Communications Summit
31 October to 2 November 2006
Contacts for further information: firstname.lastname@example.org & email@example.com
How to register for the event: firstname.lastname@example.org