TAILIEUCHUNG - Independent Component Analysis - Chapter 23: Telecommunications

This chapter deals with applications of independent component analysis (ICA) and blind source separation (BSS) methods to telecommunications. In the following, we concentrate on code division multiple access (CDMA) techniques, because this specific branch of telecommunications provides several possibilities for applying ICA and BSS in a meaningful way. | Independent Component Analysis. Aapo Hyvarinen Juha Karhunen Erkki Oja Copyright 2001 John Wiley Sons Inc. ISBNs 0-471-40540-X Hardback 0-471-22131-7 Electronic 23 Telecommunications This chapter deals with applications of independent component analysis ICA and blind source separation BSS methods to telecommunications. In the following we concentrate on code division multiple access CDMA techniques because this specific branch of telecommunications provides several possibilities for applying ICA and BSS in a meaningful way. After an introduction to multiuser detection and CDMA communications we present mathematically the CDMA signal model and show that it can be cast in the form of a noisy matrix ICA model. Then we discuss in more detail three particular applications of ICA or BSS techniques to CDMA data. These are a simplified complexity minimization approach for estimating fading channels blind separation of convolutive mixtures using an extension of the natural gradient algorithm and improvement of the performance of conventional CDMA receivers using complex-valued ICA. The ultimate goal in these applications is to detect the desired user s symbols but for achieving this intermediate quantities such as fading channel or delays must usually be estimated first. At the end of the chapter we give references to other communications applications of ICA and related blind techniques used in communications. MULTIUSER DETECTION AND CDMA COMMUNICATIONS In wireless communication systems like mobile phones an essential issue is division of the common transmission medium among several users. This calls for a multiple access communication scheme. A primary goal in designing multiple access systems is to enable each user of the system to communicate despite the fact that the other 417 418 TELECOMMUNICATIONS CDMA A schematic diagram of the multiple access schemes FDMA TDMA and CDMA 410 382 . users occupy the same resources possibly simultaneously. As the number of

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