Multicarrier Block-Spread CDMA for Broadband Cellular Downlink
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Multicarrier Block-Spread CDMA for Broadband Cellular Downlink Frederik Petre´ Wireless Research, Interuniversity MicroElectronics Center (IMEC), Kapeldreef 75, 3001 Leuven, Belgium Email: [email protected]
Geert Leus Electrical Engineering, Mathematics and Computer Science, Delft University of Technology (TUDelft), Mekelweg 4, 2628 CD Delft, The Netherlands Email: [email protected]
Marc Moonen Department of Electrical Engineering (ESAT), Katholieke Universiteit Leuven (KULeuven), Kasteelpark Arenberg 10, 3001 Leuven, Belgium Email: [email protected]
Hugo De Man Interuniversity MicroElectronics Center (IMEC), Kapeldreef 75, 3001 Leuven, Belgium Email: [email protected] Received 6 March 2003; Revised 7 November 2003 Effective suppression of multiuser interference (MUI) and mitigation of frequency-selective fading effects within the complexity constraints of the mobile constitute major challenges for broadband cellular downlink transceiver design. Existing wideband direct-sequence (DS) code division multiple access (CDMA) transceivers suppress MUI statistically by restoring the orthogonality among users at the receiver. However, they call for receive diversity and multichannel equalization to improve the fading effects caused by deep channel fades. Relying on redundant block spreading and linear precoding, we design a so-called multicarrier block-spread- (MCBS-)CDMA transceiver that preserves the orthogonality among users and guarantees symbol detection, regardless of the underlying frequency-selective fading channels. These properties allow for deterministic MUI elimination through low-complexity block despreading and enable full diversity gains, irrespective of the system load. Different options to perform equalization and decoding, either jointly or separately, strike the trade-off between performance and complexity. To improve the performance over multi-input multi-output (MIMO) multipath fading channels, our MCBS-CDMA transceiver combines well with space-time block-coding (STBC) techniques, to exploit both multiantenna and multipath diversity gains, irrespective of the system load. Simulation results demonstrate the superior performance of MCBS-CDMA compared to competing alternatives. Keywords and phrases: multicarrier CDMA, broadband cellular system, frequency-selective fading channels, equalization, MIMO, space-time block coding.
1. INTRODUCTION The main drivers toward future broadband cellular systems, like high-speed wireless internet access and mobile multimedia, require much higher data rates in the downlink (from base to mobile station) than in the uplink (from mobile to base station) direction. Given the asymmetric nature of most of these broadband services, the capacity and performance bottlenecks clearly reside in the downlink of these future systems. Broadband cellular downlink communications poses three main challenges to successful transceiver design. First, for increasing data rates, the underlying multipath channels
become more time dispersive, causing intersymbol interferen
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