to 19 2 kbps in this way after the reverse packet data rate is increased at step 314 the reverse packet data transmission is performed at the predetermined data rate at step 300 in addition as a result of the determination in step 312 if the received rab does not have the value u201c 1 u201d the mobile terminal determines at step 316 whether the received rab has a value u201c 10 u201d as a result of the determination in step 316 if the received rab has the value u201c 10 u201d the mobile terminal maintains the reverse packet data rate at step 320 the reverse packet data transmission is performed at the predetermined data rate at step 300 while maintaining the current set data rate however as a result of the determination in step 316 if the received rab does not have the value u201c 10 u201d it has a value u201c 11 u2019 in this case after decreasing the reverse packet data rate by one step at step 318 the mobile terminal performs the reverse packet data transmission at the predetermined data rate at step 300 in this way the mobile terminal changes the width of the variation of the data rate not by one step but by two steps or one step as required this allows the base station to adjust for the interference and capacity variation of the base station in addition the data can be transmitted with improved probability of success owing to.