The present invention provides an overflow control method for frame
synchronization of base stations in wireless communication network
system. The wireless communication network system includes a radio
network controller, a first base station, a second base station, and a
mobile unit. The radio network controller transmits a plurality of data
frames to the first base station and the second base station. The present
invention includes the following steps. First, determine whether number
of the plurality of data frames received by the second base station is
larger than a judging storage capacity. Second, calculate an X and delete
X of data frames from the second base station if the number is larger.
The X is equal to the result of subtracting the judging storage capacity
from the number. Meanwhile, detect a link quality between the mobile unit
and the first base station. If the link quality is lower than a preset
value, calculate an N and delete N of data frames from the second base
station when N is larger than zero. The N is equal to number of data
frames not yet deleted from the second base station and already received
by the mobile unit.