hi Karthik,
today i first time saw that question thats why i m giving u answer.
as u said each frequency in gsm is further divided into 8 time slots and u get this. 1/200KHZ=5 microseconds.so my sweet buddy.200KHZ is the bandwidth of the channel if it is devided it will give u the bandwidth of the slots not “time”.so ur question is wrong.if u want more u can write ur question.
bye
mirza