As video on demand (VOD) services are deployed, cable operators will experience a fundamental shift in their business,
moving from broadcast to unicast content delivery. Another significant change is the introduction of Gigabit Ethernet
into their network, which is providing an unprecedented opportunity to turn the cable operator's infrastructure into a
sustainable competitive advantage. However, Gigabit Ethernet is more than just transport; it's the foundation of the
Next-Generation Digital Video Network. IPQAM modulator, which is a main equipment, aren't made in China so far. It
is the first time that we did design IPQAM modulator and will apply it to interactive TV based on DWDM (dense
wavelength-division multiplexing). This paper introduces the principle of IPQAM modulator and transmission approach.
The differences between IPQAM and conventional QAM are analysed. Some key techniques such as
scrambling, statistical multiplexing, Data over Cable Service Interface Specification (DOCSIS) 3.0, software defined
radio as well as DVB simulcrypt are also studied.