An innovative cable modem system for broadband communication

In order to develop an effective and scalable approach for broadband communication over cable, it is essential to understand the realities of today´s cable plants, which range from pure-coaxial systems to hybrid fiber/coax (HFC) plants. An effective broadband access system must be able to send high-speed data in both directions over a variety of plant topologies. The upstream data path, occupying the 5-42 MHz portion of the RF spectrum, is filled with ingress, impulse noise, narrowband interference, wideband Gaussian noise, misalignments, and nonlinear impairments, making high-speed data transmission difficult. Effective upstream communication over this medium requires a new approach. This paper describes the principles of operation of a cable modem access system, based on S-CDMA (synchronous code division multiple access). This technology provides the basis for a robust two-way system, optimized for upstream communication over cable. It discusses key aspects of operation of an end-to-end cable modem system providing 14 Mbit/s two-way communication. It also addresses the technical and economic advantages of this approach. S-CDMA technology allows cable operators to deploy services in the high-noise portion of the upstream below 20 MHz, an area where other cable modems cannot operate. S-CDMA also employs a graceful adjustment technique, which allows continuous operation in extreme noise situations. The paper also reviews the economic benefits for cable operators