The Wireless Access Providers' Association (WAPA) has asked its members to stop using the 5 600-5 650MHz spectrum, because of interference with C-band weather radar systems.
In an advisory issued yesterday, WAPA says it has held discussions with the South African Weather Service and the Open Spectrum Alliance (OSA). It was found that wireless access providers are causing interference with the weather radar systems, particularly those located at Irene, in Gauteng, it notes.
C-band weather radar is used for measuring rainfall, flood prediction, aviation safety, storm tracking/prediction, civil and industrial disaster mitigation, as well as agricultural and environmental management.
The spectrum WAPA is advising its members to stop using is unlicensed and is utilised by wireless Internet service providers (WISPs) for terrestrial point-to-point connectivity. However, only those service providers with proper frequency licensing will receive protection from the regulator, ICASA, should they experience interference when using unlicensed spectrum.
An investigation by the OSA into spectrum shows it may be feasible to demonstrate an industry self-regulation model through “lite-licensing” spectrum for terrestrial point-to-point wireless links in the 5.9-6.1GHz range. One of the outcomes of this investigation is the advisory on the weather radar interference. The OSA includes WAPA, the Internet Service Providers' Association of SA, the Shuttleworth Foundation and 24.com.
“This is the first case of the wireless industry looking to self-regulate through consultation with other frequency users,” says Johan Botha, a WAPA joint chairman.
A software package, Dynamic Frequency Selection, should be used by WISPs on their transmission equipment to determine if frequency channels are available for transmission. The software should automatically switch to spectrum that is not being used.
“Unfortunately, the software is not as stable as it should be and so there was interference with the weather radar,” says Ellipsis Regulatory Solutions lawyer Dominic Cull.
Cull says the other problem is that there are still a number of “cowboy” operators - unlicensed service providers operating in the sector - and they often exceed power maximums on their base stations to push their signals through.
However, Botha says these so-called cowboy operators are more inclined to operate in the rural areas.
“In most of the urban areas, we find people are really trying to get along and not interfere with each other,” he notes.
Botha adds it is too early to say if the advisory has been a success, as many of WAPA's members are still doing an audit of what frequencies they are using.
“The advisory was sent out yesterday, so there has not been much of a response yet. The interference to the radars is usually within a 40km radius of their location and the Weather Service. The GPS locations of all their radars are on their Web site, so it is quite easy to figure out.”
Botha says WAPA does not have the budget or the inclination yet to be a policeman, and so it is taking a “nice guy” approach and consulting with others who have an interest in radio frequency spectrum.
“Hopefully, in 12 to 18 months' time, we will have developed a set of rules to help the industry self-regulate itself.”
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