This series is excerpted from "Mobile Broadband Multimedia Networks: Techniques, Models and Tools for 4G."
Order this book today and receive an additional 20% discount. Click here
www.elsevierdirect.com and be sure to mention 92839 when ordering this book. Or call 1-800-545-2522 and be sure to mention 92839 when ordering this book. Offer expires 11/30/2008.
Part 2 covers time division CDMA and multicarrier CDMA. Also see our OFDM tutorial. The many papers noted in this series are listed in the references section.
2.3 CDMA systems
Code Division Multiple Access (CDMA) is the most important multiple access scheme for 3G mobile communication systems. These systems follow the worldwide standard International Mobile Telecommunications-2000 (IMT-2000), part of which is the European standard UMTS, adopted in January 1998. The UMTS standard provides two air interfaces: UMTS Terrestrial Radio Access (UTRA)-Frequency Division Duplex (FDD) and UTRA-Time Division Duplex (TDD).
UTRA-FDD is based on Wideband CDMA (WCDMA), is harmonized with other 3G WCDMA solutions, and is an FDD solution, therefore requiring paired frequency bands. WCDMA is the dominating air interface of 3G systems, and multiplexing and multiple access are based only on CDMA. The required data rate is adjusted by adapting the spreading length and by assigning up to six unique codes to each user. In October 2001, the first 3G network based on WCDMA started in the Tokyo metropolitan area, under the name Freedom of Mobile Multimedia Access (FOMA). Subscribers could choose between three different handsets. The number of WCDMA networks started to grow in 2004. However, most deployments, especially in Western Europe, have not been driven by market demand or competitive pressure, but by license deadlines. As of the beginning of 2005, more than 60 WCDMA networks have been deployed worldwide, and more than 16 million subscribers could choose between around 100 different WCDMA devices (handsets and PC card products).
UTRA-TDD is based on Time Division-Code Division Multiple Access (TD-CDMA) and uses TDD, therefore being adopted for the unpaired UMTS frequency bands. In this standard, multiplexing and multiple access are based on time and code division multiplexing, which leads to a narrowband CDMA technology. Starting in 2002, this technology is being deployed in various countries worldwide to offer mobile broadband Internet services competing with wired DSL solutions.
Time Division-Synchronous Code Division Multiple Access (TD-SCDMA), an enhanced version of TD-CDMA, is the Chinese contribution to IMT-2000 and will be commercially ready in 2000 according to the TD-SCDMA Forum [TDSCOS].
MC-CDMA is a combination of OFDM and CDMA. It was proposed independently by several groups in 1993, and is being considered a key technology for 4G mobile communication systems.
An introduction to Monte Carlo (MC)-CDMA can be found in [FaKa03], [Lind99]. The high data rate mode of CDMA-2000, a family of standards based on the narrowband CDMA standard CDMA systems 23 Interim Standard-95 (IS-95), uses three 1.25 MHz wide carriers, therefore it can be considered as a variant of MC-CDMA. It is part of IMT-2000, being deployed in several countries, especially in Asia and North America.
This section covers the system specific aspects of CDMA. Details on the various algorithms used in CDMA systems can be found in Sections 3.3 (equalization), 3.5 (multi-user systems and multi-user detection), 7.3 (array processing and beamforming), and 7.4 (MIMO transmission techniques). The remainder of this section is divided into three parts, each one devoted to a specific CDMA system. Subsection 2.3.2 deals with topics related to WCDMA systems, quite a few papers treat the combination of WCDMA and multiple receive and/or multiple transmit antennas (see also Sections 7.3 and 7.4), interference cancellation techniques being another important topic (see also Section 3.5). In Subsection 2.3.3 topics related to TD-CDMA and TD-SCDMA are covered, a few papers dealing with the signal processing scheme 'joint transmission' (see also Section 3.3). Finally, Subsection 2.3.4 deals with all aspects related to systems based on MC-CDMA.