This paper proposes two space-frequency schemes with a multi-user pre-filtering technique for downlink (DL) multicarrier code division multiple access (MC-CDMA) systems. We consider the use of antenna arrays at the base station (BS) and a single antenna at the mobile terminal (MT) and derive the proposed multi-user pre-filtering technique that modulates the transmitted signal to eliminate the effects of multiple access interference (MAI) and channel distortions at the mobile terminals, while maintaining low MT complexity. Two types of detectors are considered at the MT: simple despreading and single user equalizers. The performances of the proposed schemes are compared to those of other transmit signal design approaches that have been recently proposed for DL MC-CDMA, considering both typical indoor and pedestrian scenarios, and channel coding based on UMTS specifications. © Springer Science+Business Media, LLC. 2009.

The paper considers downlink space-frequency preequalizations techniques for time division duplex (TDD) MC-CDMA. We consider the use of antenna arrays at the base station (BS) and analytically derive different preequalization schemes for two different receiver configurations at the mobile terminal: a simple despread receiver without channel equalization and an equal-gain combiner (EGC) conventional receiver. We show that the space-frequency preequalization approach proposed allows to format the transmitted signals so that the multiple access interference at mobile terminals is reduced allowing to transfer the most computational complexity from mobile terminal to the BS. Simulation results are carried out to demonstrate the effectiveness of the proposed preequalization schemes.

This paper deals with downlink space-frequency block coding (SFBC) with a multi-user pre-filtering technique for MIMO MC-CDMA systems. We consider the use of an antenna array at both the base station (BS) and the user terminal (UT). The space-frequency block codes allow that the spatial diversity be efficiently exploited and the linear multi-user frequency pre-filtering technique modulates the transmitted signal to eliminate the effects of multiple access interference (MAI) and channel distortions at the user terminals. The aim of this technique is to transfer the most computational complexity from UT to the BS, keeping the first one at very low complexity. The performance of the proposed scheme is evaluated, considering typical pedestrian scenario and both uncoded data and channel turbo coding based on UMTS specifications. © 2008 IEEE.

This paper deals with downlink space-frequency block coding with a pre-filtering technique for time division duplex MC-CDMA. We consider the use of antenna arrays at the base station (BS) and a single antenna at the mobile terminal (MT). The space-frequency block codes allow that the spatial diversity be efficiently exploited and the linear multi-user pre-filtering technique allows to format the transmitted signals so that the multiple access interference (MAI) and channel distortions at mobile terminals are completely removed. The aim of this technique is to transfer the most computational complexity from MT to the BS, keeping the first one at very low complexity. Simulations results are carried out in high data rate scenarios with the channel turbo code specified for the current UMTS system, to demonstrate the effectiveness of the proposed multi-user pre-filtering algorithm with SFBC. © 2005 IEEE.

In this communication we present a space-frequency pre-filtering technique, for downlink time division duplex (TDD) MC-CDMA systems, where the base station is equipped with an antenna array. We show that the pre-filtering approach can considerably reduce the multiple access interference at the mobile terminals allowing to transfer a significant part of the computational complexity to the base station, using a very low complex receiver at mobile. This approach relies on the availability of the channel state information at transmission, i.e., uses the time division duplex channel reciprocity between alternative uplink and downlink to obtain the channel state information. Simulation results are presented to demonstrate the effectiveness of the proposed prefiltering algorithm. Moreover, the performance of the proposed pre-filtering algorithm is assessed in two distinct scenarios: beamforming and diversity.

This communication deals with downlink time division duplex MC-CDMA system, and presents a frequency domain pre-filtering technique, where the base station is equipped with an antenna array. We show that the space-filtering approach proposed allows to format the transmitted signals so that the multiple access interference at the mobile terminals is reduced allowing to transfer a significant part of the computational burden to the base station, and therefore enabling the use of a very low complex receiver at mobile. This approach uses the time division duplex channel reciprocity between uplink and downlink to obtain the channel state information. Simulation results are presented to demonstrate the effectiveness of the proposed pre-filtering algorithm.

This paper deals with downlink time division duplex MC-CDMA system, and presents a space-frequency pre-filtering technique designed for two different receivers: an advanced one and an EGC conventional receiver, where the base station e equipped with an antenna array. We show that the space-frequency pre-filtering approach proposed allows to format the transmitted signals so that the multiple access interference at mobile terminals is reduced allowing to transfer the most computational burden to the base station. Simulations results are carried out to demonstrate the effectiveness of the proposed pre-filtering schemes.

The Multicarrier CDMA Transmission Techniques for Integrated Broadband Cellular Systems (MATRICE) project addresses a candidate solution for a Beyond 3G (B3G) air-interface based on Multi-Carrier Code Division Multiple Access (MC-CDMA). It investigates dynamic resource allocation strategies at the Medium Access Control (MAC) layer to support the transport of Internet Protocol (IP) packets over the air-interface in a cost effective manner and maximise the cell capacity with a target QoS. A candidate Dynamic Resource Allocation (DRA) protocol architecture is proposed that is based on cross-layer signalling to provide reactive resource allocation according to the fast channel and traffic variations. In-line with B3G expectations, the proposed DRA handles a very large number of users with inherent flexibility and granularity necessary to support heterogeneous traffic, and still with limited complexity. Thanks to the modular architecture of the DRA, various scheduling policies are investigated and compared in terms of capacity and reactivity to the system environment. Simulation results have shown that the MATRICE system has the potential to deliver broadband heterogenous services in a cost-effective manner, and emerge as a propespective candidate air-interface for B3G cellular networks.

The aim of this paper is to design new multi-user receivers based on the iterative block decision feedback equalization concept for MC-CDMA systems with closed-form interference alignment (IA) at the transmitted side. IA is a promising technique that allows high capacity gains in interfering channels. On the other hand, iterative frequency-domain detection receivers based on the IB-DFE concept can efficiently exploit the inherent space-frequency diversity of the MIMO MC-CDMA systems. In IA-precoded based systems the spatial streams are usually separated by using a standard linear MMSE equalizer. However, for MC-CDMA based systems, linear equalization is not the most efficient way of separating spatial streams due to the residual inter-carrier interference (ICI). Therefore, we design new non-linear iterative receiver structures to efficiently remove the aligned interference and separate the spatial streams in presence of residual ICI. Two strategies are considered: in the first one the equalizer matrices are obtained by minimizing the mean square error (MSE) of each individual data stream at each subcarrier, while in the second approach the matrices are computed by minimizing the overall MSE of all data streams at each subcarrier. We also propose an accurate analytical approach for obtaining the performance of the proposed receivers. Our schemes achieve the maximum degrees of freedom provided by the IA precoding, while allowing close-to-optimum space-diversity gain, with performance approaching the matched filter bound.

There is already significant research targeting B3G systems. The vision for this new generation includes provision of a broadband component for which various implementation technologies are being considered, one of them being MC-CDMA. The 4MORE project focuses at the system concept on techniques believed to be crucial to reach the broadband capabilities envisioned, namely Multiple Transmit Multiple Receive (MTMR) antennas and cross-layer design (L1 and L2). Specifically, the joint application of dynamic resource allocation with double Alamouti encoding and cross-layer signalling are considered to ensure seamless IP packet transport with broadband capabilities. The simulation results have shown that the 4MORE system can match the anticipated throughputs required for the cellular component of B3G systems.