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Jeanclaude Belfiore - One of the best experts on this subject based on the ideXlab platform.

  • lattice Code design criterion for mimo wiretap channels
    Information Theory Workshop, 2015
    Co-Authors: Hamed Mirghasemi, Jeanclaude Belfiore
    Abstract:

    We consider the MIMO wiretap channel, where a legitimate transmitter (Alice) wishes to communicate a confidential message to the legitimate receiver (Bob) over a MIMO channel, while its messages are being eavesdropped by Eve through another MIMO channel. Supposing that Alice uses the nested lattice Code proposed in [8], we characterize the expected value of amount of information leakage to Eve, and from minimizing this expected value, we derive a Code design criterion for MIMO lattice wiretap Codes. The special cases of block and fast fading channels are also studied. We also illustrate our lattice Code design criterion using the Alamouti Code as the simplest MIMO Code available in the literature.

  • a rate 1 2 2 space time Code without any constellation extension for th uwb communication systems with ppm
    Vehicular Technology Conference, 2007
    Co-Authors: C Abourjeily, Jeanclaude Belfiore
    Abstract:

    In this paper, we propose for the first time a 2 × 2 space-time (ST) block Code that can be applied with pulse position modulation (PPM) without introducing any constellation extension. This encoding scheme is adapted to low cost carrierless time-hopping ultra-wideband (TH-UWB) systems where information must be conveyed only by the time delay of the modulated signal that has a very low duty cycle. The proposed scheme permits to achieve full transmit diversity with M-ary PPM constellations for all values of M. Moreover, it permits to overcome the additional phase rotations or amplitude amplifications that are introduced by all the known ST Codes such as the Alamouti Code (S.M. Alamouti, 1998), the rate-1 Codes proposed in B.A. Sethuraman et al. (2003), (A. J. Hammons and H. El Gamal, 2000) for PSK and the diversity schemes proposed in L. Yang and G.B. Giannakis (2004) for TH-UWB systems with PAM or PPM.

Xianggen Xia - One of the best experts on this subject based on the ideXlab platform.

  • space time block Codes achieving full diversity with linear receivers
    IEEE Transactions on Information Theory, 2008
    Co-Authors: Yue Shang, Xianggen Xia
    Abstract:

    In most of the existing space-time Code designs, achieving full diversity is based on maximum-likelihood (ML) decoding at the receiver that is usually computationally expensive and may not have soft outputs. Recently, Zhang-Liu-Wong introduced Toeplitz Codes and showed that Toeplitz Codes achieve full diversity when a linear receiver, zero-forcing (ZF) or minimum mean square error (MMSE) receiver, is used. Motivated from Zhang-Liu-Wong's results on Toeplitz Codes, in this paper, we propose a design criterion for space-time block Codes (STBC), in which information symbols and their complex conjugates are linearly embedded, to achieve full diversity when ZF or MMSE receiver is used. The (complex) orthogonal STBC (OSTBC) satisfy the criterion as one may expect. We also show that the symbol rates of STBC under this criterion are upper bounded by 1. Subsequently, we propose a novel family of STBC that satisfy the criterion and thus achieve full diversity with ZF or MMSE receiver. Our newly proposed STBC are constructed by overlapping the 2times2 Alamouti Code and hence named overlapped Alamouti Codes in this paper. The new Codes are close to orthogonal and their symbol rates can approach 1 for any number of transmit antennas. Simulation results show that overlapped Alamouti Codes significantly outperform Toeplitz Codes for all numbers of transmit antennas and also outperform OSTBC when the number of transmit antennas is above 4.

  • a simple Alamouti space time transmission scheme for asynchronous cooperative systems
    IEEE Signal Processing Letters, 2007
    Co-Authors: Xianggen Xia
    Abstract:

    In this letter, we propose a simple orthogonal frequency-division multiplexing (OFDM) scheme for an asynchronous cooperative system, where OFDM is implemented at the source node, and time-reversion and complex conjugation are implemented at the relay nodes. The cyclic prefix (CP) at the source node is used for combating the timing errors from the relay nodes. In this scheme, the received signals at the destination node have the Alamouti Code structure on each subcarrier, and thus, it has the fast symbol-wise ML decoding. It should be emphasized that the relay nodes only need to implement the time-reversion, some sign changes from plus to minus, and/or the complex conjugation to the received signals, and no IDFT or DFT operation is needed. It is shown that this simple scheme achieves second-order diversity gain without the synchronization requirement at the relay nodes.

  • a criterion and design for space time block Codes achieving full diversity with linear receivers
    International Symposium on Information Theory, 2007
    Co-Authors: Yue Shang, Xianggen Xia
    Abstract:

    In most of the existing space-time Code designs, achieving full diversity is based on maximum-likelihood (ML) decoding at the receiver that is usually computationally expensive and may not have soft outputs. Recently, Zhang-Liu-Wong introduced Toeplitz Codes and showed that Toeplitz Codes achieve full diversity when a linear receiver, zero-forcing (ZF) or minimum mean square error (MMSE) receiver, is used. Motivated from Zhang-Liu-Wong's results on Toeplitz Codes, in this paper, we propose a design criterion for space-time block Codes (STBC), in which information symbols and their complex conjugates are linearly embedded, to achieve full diversity when ZF or MMSE receiver is used. Subsequently, we propose a novel family of STBC that satisfy the criterion and thus achieve full diversity with ZF or MMSE receiver. Our newly proposed STBC are constructed by overlapping the 2times2 Alamouti Code and hence named overlapped Alamouti Codes in this paper. The new Codes are close to orthogonal while their symbol rates can approach 1 for any number of transmit antennas. Simulation results show that overlapped Alamouti Codes significantly outperform Toeplitz Codes for all numbers of transmit antennas and also outperform orthogonal STBC (OSTBC) when the number of transmit antennas is above 4.

  • distributive high rate full diversity space frequency Codes for asynchronous cooperative communications
    International Symposium on Information Theory, 2006
    Co-Authors: Wei Zhang, Xianggen Xia
    Abstract:

    In user cooperative communications, relay nodes are usually asynchronous. By realizing that the processing in the frequency domain is insensitive to the errors in the time domain, Mei et. al., (2005) recently applied the OFDM technique to achieve the full cooperative diversity for asynchronous cooperative communications, where orthogonal space-time block Codes, Alamouti Code in particular, were used for relay nodes and the channels from nodes to nodes are assumed flat fading. In this paper, we also consider asynchronous cooperative communications, but the channels from nodes to nodes are assumed to be frequency-selective fading. We use high rate space-frequency Codes to enCode the correctly detected information symbols across some subcarriers at relay nodes to achieve both full cooperative diversity and full multipath diversity for asynchronous communications, which, we show, holds if the recent high rate space-frequency Codes constructed in W. Zhang et al., (2005) are used

Belfiore Jean-claude - One of the best experts on this subject based on the ideXlab platform.

  • A rate-1 2 × 2 Space-Time Code without any constellation extension for TH-UWB communication systems with PPM
    IEEE, 2017
    Co-Authors: Abou-rjeily Chadi, Belfiore Jean-claude
    Abstract:

    In this paper, we propose for the first time a 2 × 2 space-time (ST) block Code that can be applied with pulse position modulation (PPM) without introducing any constellation extension. This encoding scheme is adapted to low cost carrierless time-hopping ultra-wideband (TH-UWB) systems where information must be conveyed only by the time delay of the modulated signal that has a very low duty cycle. The proposed scheme permits to achieve full transmit diversity with M-ary PPM constellations for all values of M. Moreover, it permits to overcome the additional phase rotations or amplitude amplifications that are introduced by all the known ST Codes such as the Alamouti Code (S.M. Alamouti, 1998), the rate-1 Codes proposed in B.A. Sethuraman et al. (2003), (A. J. Hammons and H. El Gamal, 2000) for PSK and the diversity schemes proposed in L. Yang and G.B. Giannakis (2004) for TH-UWB systems with PAM or PPM.N/

  • An Error Probability Approach to MIMO Wiretap Channels
    HAL CCSD, 2013
    Co-Authors: Belfiore Jean-claude, Oggier Frédérique
    Abstract:

    International audienceWe consider MIMO (Multiple Input Multiple Output) wiretap channels, where a legitimate transmitter Alice is communicating with a legitimate receiver Bob in the presence of an eavesdropper Eve, and communication is done via MIMO channels. We suppose that Alice's strategy is to use a Codebook which has a lattice structure, which then allows her to perform coset encoding. We analyze Eve's probability of correctly decoding the message Alice meant to Bob, and from minimizing this probability, we derive a Code design criterion for MIMO lattice wiretap Codes. The case of block fading channels is treated similarly, and fast fading channels are derived as a particular case. The Alamouti Code is carefully studied as an illustration of the analysis provided.

Wolfgang Utschick - One of the best experts on this subject based on the ideXlab platform.

  • hybrid transmit waveform design based on beam forming and orthogonal space time block coding
    International Conference on Acoustics Speech and Signal Processing, 2005
    Co-Authors: Guido Dietl, Jianqi Wang, Peilu Ding, M D Zoltowski, David J Love, Wolfgang Utschick
    Abstract:

    We derive a hybrid of beam-forming (BF) and space-time block coding (STBC), where the space-time Code is transmitted over the beams generated by the steering vectors corresponding to the channel path directions. This is for the practical case where the transmit array may have adequate information on the departure angles of the dominant paths between transmitter and receiver, but unreliable information on the associated complex path gains. We compute analytically the signal-to-noise ratio (SNR) of the proposed hybrid for the specific case of a two-path channel model and using the orthogonal Alamouti Code, and compare the result to the SNR of optimal linear precoding (LP) and the theoretically possible SNR of orthogonal STBC (OSTBC). Simulation results show that the performance of the BF/STBC hybrid can be very close to LP /sup n/der certain conditions - or even better in the practical case where there are phase estimation errors in the path gain estimates employed at the transmitter.

  • hybrid transmit waveform design based on beamforming and orthogonal space time block coding
    International Waveform Diversity and Design Conference, 2004
    Co-Authors: Jianqi Wang, Guido Dietl, Peilu Ding, M D Zoltowski, David J Love, Wolfgang Utschick
    Abstract:

    In this paper, we derive a hybrid of Beam-Forming (BF) and Space-Time Block Coding (STBC), where the space-time Code is transmitted over the beams generated by the steering vectors corresponding to the channel path directions. This is for the practical case where the transmit array may have adequate information on the departure angles of the dominant paths between transmitter and receiver, but unreliable information on the associated complex path gains. We compute analytically the Signal-to-Noise Ratio (SNR) of the proposed hybrid for the specific case of a two-path channel model and using the orthogonal Alamouti Code, and compare the result to the SNR of optimal Linear Precoding (LP) and the theoretically possible SNR of Orthogonal STBC (OSTBC). To improve the performance, power loading schemes are also considered. Simulation results show that the performance of the BF/STBC hybrid with and without power loading can be very close to LP — under certain conditions — or even better in the practical case where there are phase estimation errors in the path gain estimates employed at the transmitter.

Are Hjorungnes - One of the best experts on this subject based on the ideXlab platform.

  • decoding and performance bound of demodulate and forward based distributed Alamouti stbc
    IEEE Transactions on Wireless Communications, 2013
    Co-Authors: Ankur Bansal, Manav R Bhatnagar, Are Hjorungnes
    Abstract:

    In a demodulate-and-forward (DF) based cooperative communication system, erroneous relaying of the data leads to degradation in the performance of the destination receiver. However, a maximum likelihood (ML) deCoder in the destination can improve the receiver performance. For achieving a diversity gain, the Alamouti space-time block Code (STBC) can be used in the DF based cooperative system in a distributed manner. In this paper, we derive an ML deCoder of the distributed Alamouti STBC for the DF based cooperative system with two imperfect relaying nodes. We also consider a DF cooperative communication system in which one out of two relays is in outage. A piece-wise linear (PL) deCoder for the DF cooperative system with the distributed Alamouti Code and one relay in outage is proposed. The PL deCoder provides approximately the same performance as that of the ML deCoder with reduced decoding complexity. We derive the pairwise error probability (PEP) of the proposed ML deCoder with binary phase-shift keying constellation. An optimized transmit power allocation for the relays is performed by minimizing an upper bound of the PEP. It is shown by simulations that the proposed ML deCoder enables the DF protocol based cooperative system to outperform the same rate amplify-and-forward protocol based cooperative system when both systems utilize the distributed Alamouti STBC.

  • improved interference cancellation scheme for two user detection of Alamouti Code
    IEEE Transactions on Signal Processing, 2010
    Co-Authors: Manav R Bhatnagar, Are Hjorungnes
    Abstract:

    In this correspondence, we propose an improved interference cancellation method for two-user multiple access based MIMO communication system. It is shown in the correspondence, that by using the proposed receiver array processing technique a diversity order of 2M can be achieved in a two-user interference cancellation system with two transmit and more than two (M > 2) receive antennas. We derive pairwise error probability (PEP) bounds for different number of receive antennas and prove the diversity order for different cases theoretically. The proposed scheme provides better diversity than one existing interference cancellation scheme.