In this paper we consider channel estimation for MIMO-OFDM systems, specifically when null carriers are placed at the border of the spectrum in order to limit interference with neighboring spectrums. Indeed, the presence of these null carriers leads to degradation on the transform domain channel estimation (TD-CE) because of a "border effect" phenomenon. Truncated singular value decomposition (TSVD) based method allows to improve the accuracy of the TD-CE by significantly reducing each "border effect". However, its application to MIMO systems may cause problem due to its high complexity. We propose in this paper, a solution based on the power profile of the transfer matrix in order to considerably reduce the complexity. The efficiency of the proposed solution is demonstrated within 3GPP system context.

In this paper, a new multiple access scheme called frequency interleaved code division multiple access (FI- CDMA) is proposed. The major novelty of this scheme is that it is able to benefit from the advantages of the well known multi-carrier code division multiple access (MC-CDMA) and to solve one of the major drawback encountered by OFDM-based techniques, the fluctuations of the transmitted signal, represented by the peak-to- average power ratio (PAPR).

This paper deals with a novel transform domain channel estimation (TD-CE) based on discrete cosine transform (DCT) for the MIMO-OFDM system. After the description of the conventional DCT based method, a channel estimation scheme improved in terms of both performance and complexity using small DCT blocks is proposed. Finally the efficiency of this estimator is evaluated within IEEE802.11n and 3GPP/LTE system contexts.

This paper deals with a novel transform domain channel estimation (TD-CE) based on discrete cosine transform (DCT) for the MIMO-OFDM system when null carriers are placed at the edges of the spectrum. After the description of the conventional DCT based method, an improved channel estimation scheme using truncated singular value decomposition is proposed. Finally the efficiency of this estimator is evaluated within 3GPP/LTE system context.

In this paper, hardware implementation of a 4 times 4 MIMO MMSE Equalizer based on a matrix triangularization is analysed. An architecture is proposed, where the 81 rotations required in the triangularization process are performed using pipelined CORDIC. Based on this architecture, the trade-off between complexity and data rate is studied through two FPGA implementations of the MMSE equalizer, computing MMSE filtering every 6 clock cycles or 38 clock cycles. Hardware complexity evaluations shows that due to the irregular computational need of the triangularization, it is more efficient to pipeline operations as much as possible to obtain the best complexity/data rate trade-off.

Today iterative receivers have proved their efficiency in cancelling interference within the field of wireless communications. However their complexity is often seen as a brake for their use in real systems. In this paper an efficient iterative receiver real-time implementation for a 4 times 4 MIMO system is presented. An architecture of MMSE iterative receiver for MIMO-OFDM systems is proposed to limit latency and complexity due to iterative process: MMSE equalization implementation is realized using CORDIC operators; the scheduling between MIMO detection and channel decoding is optimized and specific interleaving functions are introduced to reduce latency and accelerate the convergence process. The implemented receiver is integrated in a real-time FPGA testbench and compared in terms of complexity and performance with a non iterative solution.

In this paper a FPGA implementation of a 4 times 4 MIMO MMSE Equalizer based on the QR factorization technique is presented. Considering fast varying channels a new filter is computed at each new channel realization thanks to an efficient architecture of matrix triangularization. The QR decomposition is performed with only 6 unrolled coordinate rotation digital computer (CORDIC) operators, which are efficiently exploited to minimize the latency of computation. Soft LLR obtained in output of the equalizer are validated on an FPGA hardware bench including a 4 times 4 Rayleigh fading channel and turbo- coding.

In this paper an iterative receiver including a duo-binary turbo code is proposed for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. A double iterative loop allows to obtain good performance by efficiently cancelling co-antenna interference and profiting from the gain of duo-binary turbo decoding. Nevertheless, in order to limit complexity of the receiver, a MMSE interference canceller is considered and a new sequencing is proposed to compute in parallel turbo decoding and MIMO detection. By this way, calculation power is evenly distributed and processing time is reduced. The performance of this MIMO-OFDM system is validated by simulations for a 4times4 spatial multiplexed case under BRAN E channel.