this is what i understand from ur question.
an E1 given to site wether a erisson or nokia site n atmost 15 TRX are supported by each E1 (LAPD MUX Technique).
if we have a 444 config for a site
i.e for each sector we hav
8×4 = 24 channels
out of these v use 3 1 for BCCH, 2 for SDCCH, n remaining 21 for TCH without GPRS Dimensioning,
for 21 channels at 2% GOS we hav equavalent BH traffic of abt 14.038 erlangs.
i dont thinks hopping hav some effect on traffic, if i am wrong some one correct me.
i hope it is useful