C band interference filters (external link):
C Band spectrum threat at CPM and WRC 2007
If you are operating in C band (3.4 - 4.2 GHz), you are in potential big trouble. I am putting this page here to make you aware of a significant technical threat to your business.
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. In addition, other administrations are looking to deploy these new terrestrial services in the standard C band frequencies (3.7 to 4.2 GHz). 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 interference interruptions which have occurred throughout Africa, and in Australia, Bolivia, the Caribbean, China, Fiji, Hong Kong, Indonesia and Russia.
A Report recently issued by The Office of the Telecommunications Authority (OFTA) in Hong Kong 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 to BWA systems, C band spectrum is being targeted for deployment of terrestrial mobile services (IMT). The ITU-R Working Party 8F, responsible for the terrestrial component of Agenda Item 1.4 of the World Radiocommunications Conference 2007 (WRC-2007), has included the 3.4-4.2 GHz frequency range as a potential candidate band for these services.
|Broadband Wireless Access and
IMT services are similar in that they are both characterised 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 can not 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.
Furthermore, the implementation of exclusion zones would negatively impact
the ability of FSS operators to expand operations beyond existing earth
The only effective solution to protect satellite services in the extended and standard C band frequencies is to separate them from terrestrial systems such as WiMax or BWA by several to thousands of kms, or to find other spectrum for these services to operate.
The Global VSAT Forum is asking you to help us help you protect your business from this threat. I urge you to take the following actions:
C band spectrum action plan:
Page created 10 October 2006, 21 March 2007, 17 Feb 2015 Eric Johnston