White space and its possible effect on broadband in Kenya
Posted Wednesday, June 20 2012 at 17:55
White space refers to frequencies that are allocated for telecommunications but are not used in active transmission.
They, however, play a crucial role in enabling interference free communication. In layman’s terms, if there are two adjacent FM radio stations say Hope FM at 93.30Mhz and BBC-Africa at 93.90Mhz, the two are separated by white space bandwidth equal to the difference of the two (93.90Mhz-93.30Mhz = 0.6Mhz or 600Khz).
If you look at the entire FM or TV spectrum, there is a lot of white space frequencies not in active use but is used as guard band to enable listeners tune clearly and avoid hearing two radio channels at the same time. The same is true also for Television (TV) transmission.
TV transmission uses the UHF frequency range of 470Mhz-806MHz (for example KTN Kenya transmits at 758-764Mhz which is channel 62 on the ITU chart. Remember this logo here? that rainbowy 62 wasn’t a fashion statement).
Each TV station is allocated 6Mhz out of which only three points are used for picture, colour and audio, the rest is white space.
Taking the KTN example, 759.25Mhz is used for video, 762.83Mhz is used for colour while 763.75Mhz is used for the audio in the TV channel. The rest is what is known as white space and just lies in waste though serving as guard bands.
It is this wasteful nature of analog TV and radio broadcast that there is a concerted push by Communications Commission of Kenya to move to digital transmission which unlike analog, does not have white spaces and therefore doesn’t waste precious frequencies.
The push to digital TV is informed by the fact that if all stations transmit digital signals, they will free up the white spaces for other uses.
From the consumer’s perspective, the push for analog to digital transmission is because they will also benefit from clearer and rich content that it will bring along (such richness includes being able to set reminders on future programs, scroll what’s next... just as you are able to do now on satellite TV such as DStv but not on the local free to air stations).
Kenya has set a target of 2012 to complete the analog to digital TV migration and there is already a lot of progress being made on that front. Once the migration is complete, it will have released the UHF band for other uses such as broadband internet, SCADA and remote metering systems and many more.
However, once released, these frequencies will be unlicensed meaning anyone can use them without prior approval by CCK.
In the USA for example the fact that white space will be unlicensed has seen the FCC face legal proceedings by wireless microphone manufacturers (which use white space) because it would mean that they will be interfered with by more powerful transmission sources such as white space base stations on tall buildings etc.
The FCC has however gone ahead and allowed the use of white space for other uses.
The fact that white space is at lower frequency (470Mhz-806MHz ) compared to existing last mile solutions such as Wimax (2000Mhz and 5000Mhz ranges) or Wi-Fi, the white space can travel much farther and around physical objects.
It is estimated that a Wi-Fi hotspot that changes to use white space frequency range can increase its coverage area by 16 times hence enabling wide reach.