Comparison between WCDMA and CDMA2000 from technical aspect

W-CDMA
First let’s look at WCDMA technology. In conjunction with GPRS and EDGE which are evolutionary developments of the GSM technology, W-CDMA can be applied, both cost-effectively and with little need for additional resources. Mobile telephones and other devices used in W-CDMA mode will be able to use GSM, GPRS or EDGE, which ensures a seamless transition within the existing networks. W-CDMA attains its high performance by transmitting signals from the various services which require variable data rates by assigning bandwidth flexibly (bandwidth on demand). Each signal is coded, and then modulated and distributed ("spread") across a 5 MHz transmission bandwidth. The frequency band is available to all subscribers simultaneously. The coding identifies the signals destined for the each individual subscriber. All other users that do not have the appropriate codes will only receive the sum total of all signals in the form of undefined noise.

cdma2000
cdma2000 is a family of mobile technologies that are based on a narrow band (1.25 MHz channel bandwidth) version of CDMA and are derived from the Interim Standard No. 95 (IS-95) which was published in 1993 by the North American trading organization, the TIA. Although a multi-carrier CDMA that is able to handle multiple sequences IS-95 carriers was originally suggested within the framework of IMT-2000, only the single carrier solution of the cdma2000 family has remained (hence the name 1x). The first step takes the form of 1xRTT (also called cdma2000 1x) a slightly improved variant of IS-95 including the integration of a packet-switching core network which delivers similar performance to GPRS. Since the data throughput did not meet the 3G guidelines, the HDR (High Data Rate) system proposed by Qualcomm in 1998 was introduced as an evolution phase and was accepted as a standard known as cdma2000 1xEV-DO in August 2001. 1xEV-DO is designed especially for data services that are not runtime critical, and requires a separate frequency band. This means that transmission capacities are reserved exclusively for data, even if there is no need, which can be a waste of radio resources. In order to eliminate this problem, the new version, cdma2000 1xEV-DV, is designed to handle both voice traffic and data on a single frequency bandwidth. Only this second stage of evolution can be compared to W-CDMA.

Hence, the wider bandwidth of W-CDMA promises to deliver particularly good service quality and proliferation characteristics. The technology of 1xEV systems from cdma2000 appear to be stretched to its limits in terms of additional capacity increases. In contrast, W-CDMA still has potential for increased performance as is made clear by the HSDPA upgrade standard approved in Spring 2002. This allows for a downlink data rate of up to 10 Mbps thanks to improved transmission mechanisms optimized for data transfer.

Although the migration path from GSM to UMTS/W-CDMA also brings about a change in the technology used for transmission, solutions for the reuse of existing network infrastructures appear to be simpler and more cost-effective for this technology than for the cdma2000 system family. Thus, for instance, upgrading to version 1xEV-DO would require huge investment to set up a separate overlay network.

We should notice another problematic issue is the GPS satellite detection of the base stations which is required for cdma2000. Since GPS technology requires an uninterrupted line of sight to the satellites, small cells, for example, inside buildings, or between tall buildings, require additional outlay for installing external GPS receivers. W-CDMA on the other hand operates in asynchronous mode and, as a result, can be used universally without GPS detection.

From the above analysis, we can draw the conclusion that WCDMA outweighs CDMA2000 from a technical aspect.