Showing papers by "Sequans published in 2012"

Multi-user MIMO and Carrier Aggregation in 4G systems: The SAMURAI approach

Abstract: The market success of broadband multimedia-enabled devices such as smart phones, tablets, and laptops is increasing the demand for wireless data capacity in mobile cellular systems. In order to meet such requirements, the introduction of advanced techniques for increasing the efficiency in spectrum usage was required. Multi User -Multiple Input Multiple Output (MU-MIMO) and Carrier Aggregation (CA) are two important techniques addressed by 3GPP for LTE and LTE-Advanced. The aim of the EU FP7 project on “Spectrum Aggregation and Multi-user-MIMO: real-World Impact” (SAMURAI) is to investigate innovative techniques in the area of MU-MIMO and CA with particular focus on the practical, real-life, implementation and system deployment aspects. In the present paper, we provided an overview of the up-to-date SAMURAI contributions together with a description of the SAMURAI demonstrators developed as core part of the project.

Iterative compensated MMSE channel estimation in LTE systems

Abstract: In this paper, an iterative channel estimation algorithm is considered in LTE systems. In order to take advantage of “null” sub-carriers (guard band) in LTE systems and make the algorithm simpler, an iterative compensated MMSE (IC-MMSE) channel estimation algorithm is proposed in frequency domain. Together with a simple “linear interpolation” in time domain, channel estimates are obtained in an iterative way with lower complexity. Theoretical analysis shows that the compensation process does not affect the accuracy of iterative MMSE channel estimation. Simulation results confirm that the proposed channel estimation has very robust performance and approaches the best achievable performance.

Iterative channel estimation method with compensated mmse

Abstract: A channel estimation treatment method and device for obtaining binary data conveyed in a signal. The method includes: obtaining a current vector of channel estimates, each element of the current vector corresponding to an estimate of a subchannel; detecting, inside the current vector, at least one pilot symbol; splitting the current vector in at least two subvectors, at least one first subvector including channel estimates related to data symbols and/or pilots symbols and at least one second subvector including channel estimates related to null symbols; decoding the at least one first subvector, delivering at least one first treated subvector; modifying the at least one second subvector by assuming presence of pilot symbols in the at least one second subvector, delivering at least one second treated subvector; and calculating a new vector of channel estimates with the at least one first treated subvector and the at least one second treated subvector.

Co-channel interference cancellation in reuse-1 deployments of WiMAX system

Abstract: In order to maximize the spectral efficiency, the current wireless systems tend to allocate the same frequency resources to different users, which causes the so-called Co-Channel Interference (CCI) on the signal received by the mobile user. If not handled appropriately, CCI may seriously degrade the communication performance. Therefore, for more reliable performance, robust transceiver techniques are required. In this paper, we consider WiMAX systems as example and propose a CCI cancellation method at the mobile user side based on a realistic cell-edge scenario. Particular attention is given to improve the performance during handover which is inevitable in reuse-1 networks. By using the conventional receiver structure with small additional processing, it is shown by simulations that the proposed method improves the performance significantly when a strong CCI is present.

Carrier aggregation aparatus

Abstract: An arrangement for a transmitter and/or receiver which is adapted to allow carrier aggregation in a wireless communication system, comprising a plurality of radio frequency (RF) blocks, each of which is inherently adapted to operate substantially across (in the region of) one of the particular groups of frequency ranges. The number of groups may be 5 or less.

Circuit and method with improved mixer linearity

Abstract: A switching circuit is linearized by using a capacitor to apply a drive voltage to an FET, wherein the drive voltage is independent of the signal switched by the switching circuit.

Method for decoding a spatially multiplexed data signal using a maximum likelihood detection

Abstract: The disclosure relates to a method for decoding a received signal in a MIMO communication system and in at least one layer, each layer carrying at least one data symbol belonging to a signal constellation. The method includes, for one of the at least one layer, a maximum likelihood detection step. This step includes: selecting one candidate value for the data symbol of the layer, and determining the Euclidian distance between the received signal Y and the data signal transmitted using said candidate value multiplied by said channel matrix H, weighted by the inverse of a noise covariance matrix C such as ∥Y−Σ i H i x i ∥ C −1 2 , expressed as: Σ i≠n ∥H i ∥ C −1 2 |x i | 2 −2 ( H i H C −1 Y −0.5Σ j≠i,n H i H C −1 H j x j ) x* i +∥H n ∥ C −1 2 |x n | 2 −2 ( H n H C −1 Y−Σ j≠n H n H C −1 H j x j ) x* n =Σ i≠n α i R ( x i ) 2 −2β i R x i +α n R ( x n ) 2 −2β n R x n +Σ i≠n α i I (ℑ x i ) 2 −2β i I ℑx i +α n I (ℑ x n ) 2 −2β n I ℑx n . The terms depending on α k are computed by adding to each of them a predetermined constant depending on the size of the constellation of the layer k, called a constellation dependent constant.

Interference Reduction Method for multimode radio communication system

Abstract: The invention relates on a method for calibrating multimode radio communication systems comprising at least two different subsystems, a first subsystem implementing a first signal transmission technology and a second subsystem implementing a second signal transmission technology that is different from the first signal transmission technology . According to the invention, said method comprises: - a step of transmitting, by said first subsystem, a signal at a predetermined transmission power; - a step of measuring, by said second subsystem, an amount of noise perceived on at least one channel associated with said second subsystem; - a step of recording, in a data structure, said amount of noise for said at least one associated channel.

Method and user equipment for carrrier aggregation

Abstract: The disclosure relates to a user equipment for receiving an OFDM signal, said user equipment comprising a plurality of carrier processing chains (4001, 4002). According to the disclosure, said user equipment comprises a carrier aggregation module (30), aggregating the signals received on each carrier processed by said plurality of carrier processing chains (4001, 4002), said aggregation module (30) being implemented for delivering a set of aggregated signals of said plurality of carrier processing chains at the input of a Fast Fourier Transform module (430) of a PHY layer processing subsystem (31) of said user equipment

TSVD-EM channel estimation for transmit diversity in LTE systems

Abstract: In this paper, the truncated singular value decomposition expectation-maximization (TSVD-EM) based channel estimation on single transmit antenna transmission is extended to transmit diversity transmission. Particular attention is given to Long Term Evolution (LTE) systems. In order to obtain the received symbols for each transmit antenna, an approximation is proposed by using the soft symbols and channel estimates from the previous iteration. We prove that the mean square error (MSE) of TSVD-EM on transmit diversity transmission has almost the same constant value at high signal-to-noise ratio (SNR) as on single transmitter antenna case. Simulation results show that the proposed TSVD-EM channel estimation improves system performances remarkably and approaches the performance with perfect channel state information. Even without pilot boosting used in LTE systems, the TSVD-EM achieves the same performances as with pilot boosting.