With the next round of the US Federal Communications Commission’s auction of the airwaves drawing nearer, San Diego, California-based Qualcomm Inc has been trying to promote its Code Division Multiple Access wireless technology, in the hope that successful bidders will adopt it as the basis for their networks. The company says that in recent tests, enhancements to its technology provided voice quality that was as good or better than the international 16Kbps standard for wireline quality speech. The Qualcomm Code Excited Linear Predictive (QCELP-13) 13Kbps variable rate voice coder was developed by Qualcomm, and has, says the company, been supported by the recently-formed CDMA Development Group. The tests on the technology, which has been dubbed PureVoice, were carried out at AT&T Corp’s Holmdel Listening Laboratory and the technology is itself an enhancement to Qualcomm’s QCELP-8 8Kbps coding system, which is used in the US IS-95 Code Division Multiple Access standard. Indeed, PureVoice is said to enable cellular operators to switch between 8Kbps and 13Kbps coding to maximise the number of simultaneous users and to enhance voice clarity. Similarly, Qualcomm says that the technology can automatically code at the higher rate when speech is taking place and at the lower speed when the speaker is pausing or listening. The technology is to be incorporated into an ASIC that will be sold to licensees, while both AT&T and Motorola Corp are to announce the availability of 13Kbps voice coding options in their Code Division Multiple Access product offerings. In a separate series of tests, AT&T and Qualcomm also claim to have found that in the 1.8GHz-to-2.0GHz Personal Communications Services frequency range, Code Division Multiple Access provides at least double the coverage area of the rival DCS-1900 technology. DCS-1900, which is used in the Groupe Speciale Mobile mobile phone standard, is based on Time Division Multiple Access technology. The tests, which were carried out on operational systems in the field, are said to have found that the Code Division Multiple Access link budget advantage was a minumum of 8dB, which corresponds, according to AT&T, to some three to five times the area for each cell site.
