The purpose of the ‘Burst QPSK/16QAM Modulator’ is

the data transmission from the subscriber to the service

provider (upstream) via coax cable. Thus, its main

applications are cable modems at the subscriber’s

home. In such systems one headend cable modem

serves 500 to 2000 subscriber’s cable modems. The

connecting coax cable must be shared in upstream

direction. These multipoint-to-point connections are

controlled by one headend modem, which assigns time

slots for data transmission to the different cable

modems. Therefore the transmitter in the subscriber’s

cable modem must be able to transfer enclosed data

blocks in the assigned time periods (i.e. bursts) and

not to send continuously.