Sequans

About: Sequans is a company organization based out in Reading, United Kingdom. It is known for research contribution in the topics: Communication channel & MIMO. The organization has 73 authors who have published 126 publications receiving 1066 citations.

Full frequency reuse method in a wireless communication network with sectored cells

Abstract: A full frequency reuse communication method for a base station in a cell of a wireless communication system, the cell comprising at least a plurality of sectors, the base station comprising at least one antenna per sector to be covered, the antennas using the same frequency band. When at least a user is located in an interference region of two adjacent sectors, at least the antennas covering the two adjacent sectors cooperate with each other to carry out a MIMO (Multi-Input-Multi-Output) technique for communication with at least the user.

Messaging scheme for positioning

Abstract: A method of providing position assistance to a UE, the method comprising providing, by a location server, at least one unsolicited message, each message comprising one of data selected from a list comprising GNSS ephemeris assistance data, GNSS acquisition assistance data, OTDOA assistance data and eNB position data for a predefined area.

Performance Analysis of Reciprocity Calibration in Massive MIMO

Abstract: Time Division Duplexing (TDD) Massive MIMO (MaMIMO) relies on channel reciprocity to derive the channel state information at the transmit side (CSIT) from the uplink (UL) channel estimates. This reciprocity is impacted by the transmit and receive front ends which are non-reciprocal and hence a calibration is required to obtain the downlink (DL) channels from the UL channel estimates. The Cramer-Rao Bound (CRB) for reciprocity calibration and an optimal algorithm were derived in [1], [2] recently. In this work, we extend this and derive a generalized CRB that applies to both coherent and non-coherent calibration schemes (introduced in [1]). More importantly, we provide original mean squared error analysis for the commonly used Least-Squares (LS) estimator under different parameter constraints, and relate it to the CRB. Finally, we compare some antenna grouping strategies for calibration based on their CRB.

Moving-Average Based Interference Suppression on Frequency Selective SIMO Channels

Abstract: Co-channel interference suppression is a key design concern for next-generation communication systems. It is particularly challenging in the presence of frequency-selective fading as the covariance matrices of the interference plus noise vary across subcarriers. The moving average technique is an effective scheme for estimating the frequency- selective covariance matrices. But the problem of choosing the optimal window size is far from trivial. In this work, we propose a window selection scheme based on the mean square error (MSE) of the covariance estimate. It only requires information of the signalto-noise ratio (SNR) and signal-to-interference ratio (SIR) and is robust against variations of the interfering channel's power delay profile. Moreover, the results can be applied to time-varying channels by simply replacing the frequency correlation function by the time correlation function.

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.