hi hargeisa,
band VIII = GSM900
band III = DCS1800
en.wikipedia.org/wiki/UMTS_frequency_bands
you need to define the center frequency of the 5MHz band you want to use. This is explained in the second table of the wikipedia page.
for example, if you need the 5MHz which are at the beginning of the GSM900 band:
in DL GSM900 : 935-960 MHz (ARFCN 1-124)
you have the first 5MHz available:
935-940MHz (ARFCN 1-25)
therefore you need toset the DL center frequency at 937.5 MHz.
the closest available is, using this range “927.4 – 957.6” increment = 0.2 : 937.6 MHz
The code for that frequency is :
5 * ((center freq in MHz) – 340 MHz)
5 * (937.6 – 340) = 2988
which indeed belongs to the Test Set “DL Channel” Range [2937 – 3088]
The UMTS system is more efficient than GSM : every WCDMA site is allocated the full 5MHz. The amount of traffic that can be carried on those 5MHz across a whole network is much more than what you could carry on a GSM network using ARFCN 1-25.
Regards
pix