Cable Access Technologies - Introduction

Introduction

Historically, CATV has been a unidirectional medium designed to carry broadcast analog video channels to the maximum number of customers at the lowest possible cost. Since the introduction of CATV more than 50 years ago, little has changed beyond increasing the number of channels supported. The technology to provide high-margin, two-way services remained elusive to the operator.

During the 1990s, with the introduction of direct broadcast satellite (DBS) and digital subscriber line (DSL), the cable operators experienced a serious challenge to their existence by competing technologies threatening to erode market share of their single product.

DBS operators marketed more choice and better quality entertainment product through digital technology, whereas the incumbent local exchange carriers (LEC) proposed to offer a combination of voice, video, and data by means of DSL.

Fearing loss of market share and the need to offer advanced services to remain economically viable, key multiple system operators (MSOs) formed the Multimedia Cable Network System Partners, Ltd. (MCNS), with the purpose of defining a product and system standard capable of providing data and future services over CATV plants. MCNS proposed a packet-based (IP) solution in contention with a cell-based (ATM) solution promoted by IEEE 802.14. MCNS partners included Comcast Cable Communications, Cox Communications, Tele-Communications Inc., Time Warner Cable, MediaOne, Rogers CableSystems, and Cable Television Laboratories (CableLabs).

The Data Over Cable Service Interface Specification (DOCSIS) 1.0 standard that resulted from the MCNS effort was unanimously accepted as the North American standard, and vendors aggressively introduced products in compliance with this standard. MSOs defined upgrade and construction programs to increase the supporting bandwidth of their plants and to provide two-way functionality.

The DOCSIS 1.0 standard prescribes multivendor interoperability and promotes a retail model for the consumer's direct purchase of a cable modem (CM) of choice. To ensure multivendor interoperability, CableLabs subjects all products offered to rigorous testing. Equipment successfully passing all tests will be CableLabs Qualified for head-end Cable Modem Terminating System (CMTS), and CableLabs Certified for CM devices.

To date, the DOCSIS 1.0 standard is proving to be a universal success, with deployments now in operation worldwide.

CableLabs, in conjunction with the vendor and user communities, is now in the process of defining DOCSIS 1.1 for the purpose of supporting Voice Over Internet Protocol (VoIP) and advanced security, and is also paving the way for advanced future multimedia services.