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1X Advanced: Delivering the best spectral efficiency for voice service

CDMA2000 1X has been widely deployed to provide voice service to more than 555 million users today. Qualcomm R&D has been developing 1X Advanced, capable of providing networks with a fourfold increase in voice capacity. Operators can deploy 1X Advanced to support more voice subscribers using limited spectrum. 1X Advanced can also be used to free up precious spectrum which can be utilized to increase broadband data capacity.


Many CDMA operators are experiencing tremendous subscriber growth today and run into spectrum limitation. The explosive growth of mobile data traffic further amplifies the need to improve spectrum efficiency. The primary goal of 1X Advanced is to maximize voice capacity. Combining air interface innovations and implementation enhancements, 1X Advanced can quadruple the voice capacity of today’s commercial CDMA 1X systems, far exceeding the voice spectrum efficiency of any other 3G and even 4G wireless technologies. 1X Advanced can be also used to improve 1X network coverage and offer enhanced voice quality.

Capacity of 1X systems can be improved incrementally. Use of EVRC-B codec and forward link interference cancellation (both available today) can achieve up to 50% gain in voice capacity. This is done without base station channel card upgrade. With receive diversity in the mobile station and reverse link interference cancellation enabled by new channel card, the voice capacity can be further improved by approximately 75%. A new radio configuration defined in 1X Advanced standard, which includes frame early termination, reduced power control overhead, and smart blanking, provides the remaining gain in voice capacity. Note that all these capacity gains are obtained without degrading the voice quality or the robustness of the system and the new radio configuration is fully backward compatible with existing ones.

The new air interface has been standardized in 3GPP2 under CDMA2000 rev E, with the spec published in April 2010. Qualcomm R&D, along with other 3GPP2 participants, are working towards completing the standardization of 1X Advanced. With the chipsets for 1X Advanced base stations and mobile devices already announced by Qualcomm, it is expected that 1X Advanced will be deployed in 2011.