A mobile station of the mobile communication system measures signal energy
on a traffic channel and interference energy on a sync channel to
calculate SIR, compares the calculated SIR with a threshold, and then
transmits the comparison results to a base station for a forward power
control operation. To this end, a PN despreader multiplies a received
signal by a unique PN code and outputs a PN despread signal. An orthogonal
code despreader multiplies the PN despread signal by a sync channel
orthogonal code and a traffic channel orthogonal code and outputs first
and second orthogonal code despread signals. An interference energy
processor measures interference energy by processing the first orthogonal
code despread signal. A signal energy processor measures signal energy by
processing the second orthogonal code despread signal. An SIR calculator
calculates SIR depending on the measured signal energy and interference
energy. The calculated SIR is compared with a predetermined threshold and
the compared results are transmitted to the base station for the forward
power control operation.
