By Mukta Kar, Majid Chelehmal, and Richard S. Prodan Cable Television Laboratories, Chezhian Renganathan , HCL Technologies Private India Pvt. Ltd.
Since cable headends traditionally deal with analog audio/video (A V) television signals, analog transmission service opportunities are limited. With analog technology, it is difficult to maintain interoperability and, as such, headend equipment can be proprietary in nature, as well as expensive and sometimes difficult to replace. Digital technology, combining standards-based compressed audio/video/data and digital transmissions, is more efficient and flexible. By implementing digital technology, opportunities to deliver new services over hybrid fiber coaxial (HFC) cable networks greatly increase, along with a proportional increase in revenue.
Additional services will add complexity at the headend. One of the benefits of standardized digital technology is that, through interoperability, distinct services can be integrated across system components from multiple suppliers. ISO/MPEG has provided standards for compression, storage, and digital A V transport; SMPTE has established standards for interfaces used in baseband digital A V equipment; and IETF has provided standard protocols for IP-based applications. Headend equipment may be designed with an integrated, flexible analog/digital architecture so that new standardized equipment may be added incrementally to enhance existing services or to add new services.
An integrated, flexible architecture with coexisting analog and digital services is presented in this paper. This architecture allows the enhancement of existing services or the addition of new services with minimal disruption to headend functions. Interface design issues relating to analog A V signals and multimedia signals, such as DTV, HDTV, and IP-based streaming is discussed.
Additionally, information is included on digital program insertion systems for adding locally compressed content (e.g., advertising) to remotely distributed compressed programming, as well as processing of IP/Internet traffic at the headend for delivery over HFC cable networks using cable data modems.