Convergence shows its colors as cable TV provider Cox Communications Inc. charts its course into next-generation wireless telephony, underscored by its announcement last month of plans to use Code Division Multiple Access technology on its personal communications services networks.
The company is a PCS pioneer’s preference winner in the Los Angeles-San Diego major trading area and also won a license for the Omaha, Neb., MTA. PCS trials have been conducted with Ericsson Inc., Motorola Inc., Northern Telecom Ltd., Qualcomm Inc., Omnipoint Corp. and others. Tested technologies include both CDMA and Global System for Mobile communications.
“CDMA is more compatible with cable infrastructure because it requires less frequency planning over cable’s extensive terrestrial network,” explained David Woodrow, senior vice president of broadband services at Cox. “CDMA also uses spectrum more efficiently and increases call capacity and call quality.” The decision to use CDMA follows more than three years of cable-based PCS testing, Woodrow added.
While CDMA may be the best suited technology for cable-based PCS, Bruce Crair, vice president and general manager for Cox California PCS Inc., said, “the condition of the cable plant and the existing topology and market of the area” is the critical factor determining a network’s success.
Cox’s PCS system will operate using remote antenna driver technology, which centralizes functionality and reduces the incremental investment in each cell, said Cable Television Laboratories Inc. of Louisville, Colo. RADs connect the cell antennas to the cable system and are placed where coverage is required.
CableLabs holds two U.S. patents on a digital version of analog-based RAD technology. D-RAD “digitizes and time-compresses the telephone signal between a base station and one or more remote antenna sites, connected via a cable television system,” CableLabs said.
To operate PCS via cable, a RAD, with a microcell integrator inside it, is strung from an existing aerial cable and connected to the cable plant through a standard tap connecting device, according to Crair. Three small antennas are mounted on the RAD, which is enclosed in a casing.
When a subscriber signal is detected, it is drawn into the RAD and converted to a cable frequency. The signal then is amplified and sent back up the coaxial cable to the fiber node. Once the signal reaches the headend interface, radio antenna signal processors split the PCS signal from the rest of the cable TV signal, explained Crair. The PCS signal is transmitted to a base station and the wireless process advances.
Crair said cable-based PCS has several advantages over standard cellular systems, including centralized modulation, network flexibility to increase capacity and infrastructure costs. Centralized modulation-having actual base stations located at a centralized point as opposed to the antenna site-reduces maintenance problems and costs associated with remote sites, Crair said. With a cable system, antennas are hung on aerial cable so they can be adjusted along the length of the cable if needed. Also, additional RADs easily can be added to increase capacity and are relatively inexpensive, he noted. In contrast, a system using towers incurs high installation costs, said Crair, between $200,000 and $500,000 per tower and associated infrastructure.
Radio channels can be reassigned to different RADs as necessary, Crair explained, and eventually they will be assigned according to usage and capacity factors. As a result, cable systems bypass some of the zoning barriers that confront networks trying to build new towers and base stations.
Simulcasting a single frequency over many RADs reduces the number of base stations needed to operate Cox’s cable system because, by broadcasting the same frequency over several RADs, overall cell size increases and a larger area can be covered, Crair contended. Cox has not yet decided which variation of RAD technology or manufacturer it will employ for its PCS systems, noted Crair.
Cox plans to begin commercial PCS service in California sometime next year, according to Crair. The company’s A and B band PCS competitors will be Pacific Telesis Mobile Services in California and AT&T Wireless Services in Nebraska.
Cox also is a partner in Sprint Telecommunications Venture, a PCS consortium headed by Sprint Corp. and including Tele-Communications Inc. and Comcast Corp.
