What are White Spaces?
I was about to ask about licensing issues, I guess this answers my main question - we still need the cooperation of ICASA, a major hurdle, as positive as you may want to be.
My other question is how does this affect the migration to DTT and the digital dividend. The way I understand it, TVWS will be making partial use of (future) digital dividend spectrum which will eventually sold/auctioned off in chunks, making TVWS a wasted exercise. Right?
No. Fair question, but it's not a wasted exercise
Let's introduce a little technical literacy here. The term "TV White Spaces" refers to unused spectrum in the TV bands. The UHF Bands IV and V cover 470 MHz to 860 MHz, which is channels 21 to 68, that is 36 channels, each 8 MHz wide. In the VHF Band III (174 - 230 MHz) , we only use 9 channels (4 - 13, excluding 12). The "Digital Dividend" is 790 - 860 MHz, i.e. channels 61 - 68.
On the Johannesburg Transmitter (Auckland Park Tower, IIRC), Sentech transmits as follows:
SABC1: channel 6, SABC2: 9, SABC3: 13, M-NET: 39, CSN: 43, e-tv: 47.
You will notice that 2 or 3 channels are left unused in each case.These are "white space". This is because analogue technology doesn't handle adjacent channels well. Changing to digital transmission solves this problem - adjacent channels can be used without suffering from adjacent channel interference.
Digital technology gives us another benefit. Currently, SABC1 is transmitted fron 12 transmitters in Gauteng on 11 channels (frequencies). Using digital technology, a Single Frequency Network (SFN) will transmit SABC1 on one channel for the whole of Gauteng, from the same 12 transmitters. In fact, using DVB-T2 (the chosen Digital Terrestrial TV technology), we can fit about 20 TV slots into one frequency channel, so all of the above (SABC1-3, e-tv, etc.) plus a whole lot more will fit into the same 8 MHz frequency channel - called a "multiplex". All of these add up to a huge saving in spectrum.
Does Digital TV also have white space?
Yes, it does.
White Spaces will still exist, although not as much. With both analogue and digital technology, the same frequency can't be used again unless it's several hundred km away. So, even if we were to fill up every available channel with digital multiplexes, there would still be geographical areas where a specific channel isn't used for TV broadcasting, but can be used for low power data transmission over a relatively limited range - less than the 50 km typical for a high power TV transmitter. The concept behind TVWS technology in the digital scenario is to use the spectrum in a "sterilised" area - where it can't be reused for high power TV broadcasting - for low power data transmission and reception.
"High power", BTW, means 10 kW or more. Durban uses a 100 kW transmitter, for example.
So, while there will be significantly less White Space once we have completed the migration to DTT (whenever that will be ...), White Space will still exist, and TVWS technology is still useful.
And yes, ICASA is quite prepared to talk about testing the technology. We are keen to foster several things, one of which is to make more efficient use of spectrum, and another is to explore new ways to provide useful and cost effective broadband connectivity to the public. TVWS technology promises to do both of these.
Steve, please make sure that your people talk to the ICASA spectrum people soon, and submit an application for a test licence before you start transmitting!
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