The first infrastructure equipment based on Code Division Multiple Access digital cellular technology is being installed in Seattle, Washington, by US West Inc, which plans to offer CDMA-based services in late 1994 or early 1995, says Thomas Crawford, director of marketing for the digital cellular group of CDMA supplier Qualcomm Inc. The real debate has […]
The first infrastructure equipment based on Code Division Multiple Access digital cellular technology is being installed in Seattle, Washington, by US West Inc, which plans to offer CDMA-based services in late 1994 or early 1995, says Thomas Crawford, director of marketing for the digital cellular group of CDMA supplier Qualcomm Inc. The real debate has been ‘when will CDMA be here?’ Well the standard was approved in July, the phones are available from us now and three of the seven Baby Bells – Pacific Telesis, Bell Atlantic and US West are doing CDMA says Crawford. PacTel Corp should begin CDMA service in early 1995, he said. He adds that San Diego-based Qualcomm has licensed almost a dozen major manufacturers, including AT&T Co, Motorola Inc, Northern Telecom Ltd, Nokia Oy and Oki Electric Industrial Co, to provide Code Division phones and infrastructure equipment. While there is still a debate in the US over the merits of Code Division versus Time Division Multiple Access, Crawford says that studies undertaken by Bell Atlantic Corp and Ameritech Inc have shown the technological superiority of Code Division. Bell Atlantic conducted field trials of Qualcomm’s Roving Test System in downtown Washington during the month of June 1992, to establish a string of performance parameters for CDMA: coverage of CDMA cells; the soft handoff; the signal power needed to produce an acceptable Frame Error Rate; the mobile transmit power versus frequency modulation, which is used in analogue cellular systems; in-building performance; and guard zone. In the test report’s conclusion, Bell Atlantic states, After analysing the results of these tests it is obvious that the CDMA system has a superior capacity, indoor performance, handoff procedure, and overall quality than a comparable FM system. The CDMA capacity of greater than 10 times FM capacity was proven in downtown Washington DC. The indoor performance showed a deeper penetration into buildings, along with a more reliable link. Soft handoff provided for uninterrupted service from cell to cell. Finally, most observers felt the quality of the speech on the CDMA system was equal to or better than the quality of FM overall. The 15 customers in a trial conducted by Ameritech between September 1992 and January 1993, gave CDMA more positive reviews than either TDMA or the existing analogue service. Says the report: Most participants rate the call quality of CDMA as ‘excellent’ or ‘very good’. Participants seem to experience few of the system problems typically encountered with analogue. In fact, compared to analogue and TDMA, few participants experience any type of system problems at all.
Participants prefer CDMA
Some of the study trial conditions, such as the small sample size, calls made from different areas and the presence of the company testing CDMA did not permit a definitive choice of CDMA, Ameritech said in its report. The company acknowledged, however, that the data from this limited trial experience suggest that the participants prefer CDMA… most, if not all, of the participants feel CDMA is a significant improvement over the current analogue system. Qualcomm’s Crawford said the company has also conducted trials in Europe, most recently in Geneva in May, 1992. He said the Swiss PTT would not let Qualcomm publish the results of the test, which was conducted side-by-side with the existing TDMA-based Groupe Speciale Mobile service. GSM and CDMA could coexist, he says, by allocating a part of GSM’s frequency to CDMA, which could then handle ten times the number of callers. There’s no frequency planning with CDMA. You don’t have to reshuffle frequencies because of its ability to adjust the signal power according to its distance from a cell site, Crawford said. He says he has also heard that German cellular suppliers are having trouble getting as many calls on TDMA as they can get on analogue. – Marsha Johnston