Global VSAT Forum
In recent years, as fiber has begun to be rolled out in major African cities, there was a common assumption that satellite-based connectivity’s days were past. But the introduction of fiber – which is at its best when providing point-to-point links – has actually paved the way for more satellite services to be deployed, providing applications for which they are best suited: Point-to-multipoint links.
This can be seen today in enterprise market, where large businesses with widely-dispersed operations increasingly recognize that there are major cost savings to be made through deployment of satellite networks.
As this trend continues, volumes are escalating, economies of scale are increasing, technology improvements are being applied, and the satellite industry is becoming more adept at tailoring not only large-enterprise solutions but also SME and consumer applications. In parallel, another crucial trend is underway in the public sector: National administrations and groups of governments are grappling with how to bridge the so-called "digital divide". National budgets have begun to allocate funding for projects that help fulfil public policy objectives, and improved access to education is among the first to be addressed.
A few developing nations began large-scale deployments of satellite-based distance learning – Ethiopia was among the first – and they reported their successes to their neighbors. Word is spreading to the highest levels of government through inter-governmental dialogues like the World Summit for the Information Society, a program through which heads of state agreed to embrace certain principles - and to achieve tangible results - in closing the communications gap in regions like Africa.
The Battle for C-band SpectrumJust as the prospects for satellite-based connectivity in Africa are gaining, the systems that operate in the 3.4-4.2 GHz band (C band) began suffering substantial interference, to the point of system failure, in places where national administrations are allowing Broadband Wireless Access systems like Wi-MAX to share the same spectrum bands already being used to provide satellite services. Worse, the same will happen if 3G and the planned 4G mobile systems (also referred to as IMT systems) are allowed to use the frequencies used in the C band for satellite downlink services as is being contemplated by some African administrations in the context of the International Telecommunication Union World Radiocommunication Conference 2015 (agenda item 1.1).
To eliminate this harmful interference, operators of satellite earth stations and users of satellite communications services have begun to unite to communicate their positions and technical requirements to national and international telecommunications regulators. Regulators and radio frequency managers need to allocate spectrum in ways that recognize the reality of harmful interference and validate the right of incumbent operators to operate and to expand services to new customers, and their customers to enjoy their services, without disruption by new users.
C band satellite, and the Broadband Wireless Access (BWA) and IMT mobile services are all important services, and there are ways to find suitable spectrum for all of them to operate.
Several African national administrations have designated portions of the frequency band 3.4 – 4.2 GHz for terrestrial wireless applications such as BWA and future mobile services (“IMT advanced”, Beyond 3G, 4G…). This band is already in use by satellite services, radar systems, and domestic microwave links. This band is commonly referred to as the C band.
In places where administrations have allowed BWA services to use the C band, there have been massive interruptions of satellite services. Interference with radars and microwave links, which also operate in these frequencies, is likely.
Use of the C-band for satellite communications is widespread throughout Africa. It is particularly vital for corporate communications in many developing countries, because of its resilience in the presence of heavy rain. C-band earth stations are also used extensively in many developed countries. C-band (“Standard C-Band” and “Extended C band” ) frequencies have been assigned for satellite downlinks since the industry was inaugurated more than 40 years ago.
C-band services cover large areas. They facilitate intercontinental and global communications, and provide a wide range of services in developing countries. Services in this band now provide critical applications such as not only distance learning, but also telemedicine, universal access, disaster recovery and television transmission in many regions.
C-band services are especially important for Africa. The supporting equipment is relatively inexpensive and the signals easily cover large areas. Such services are well adapted to provide voice, data services and internet connectivity in remote areas underserved by other communications means. They are an essential component in the ITU’s push to bridge the “digital divide” between the developed and developing world. Because they cover wide areas with minimal susceptibility to rain fade, they have proven to be exceptionally useful in tropical areas.
It is important to understand that satellite transmissions in the 3.4 – 4.2 GHz band are received by a large number of stations worldwide. Many of these stations are “receive only”, and are therefore not registered at the ITU (or generally even with the local administrations) since such registration is not required. Co-frequency operation of BWA systems would severely disrupt reception of satellite transmissions.
It must be emphasized that operation of wireless systems at C-band frequencies will not only cause interference to existing customers receiving satellite signals in this band, but it will virtually eliminate any further expansion of satellite service to new customers and regions given the incompatibility between the two systems. This will in turn lead to an eventual stagnation of satellite business in this band.
Fortunately, this is not an insoluble problem. Many other candidate bands have been identified during the course of ITU studies. The merits of these have been documented at length and the alternatives will be presented to the ITU WRC-15.
It is critical that governments and spectrum management authorities recognize the very real damage caused, and tremendous threat posed, to satellite services by use of the Standard C and Extended C-bands for terrestrial wireless systems.
A real effort to use alternatives must begin immediately. Time and again, the satellite industry has demonstrated that it is an unbeatable value proposition in supporting point-to-multi-point applications. It was demonstrated in corporate networks. It was demonstrated in DBS. It was demonstrated next in digital radio. And now it’s being demonstrated as a complement to fiber. This will be an enduring source of business for Africa for years to come.
 The bands 3.4-3.7 GHz and 3.7-4.2 GHz are usually referred to as Extended C-Band and Standard C-Band, respectively.