Vien Nguyen-Duy-Nhat

SIR Analysis for OFDM Transmission in the Presence of CFO, Phase Noise and Doubly Selective Fading

This paper presents an analysis of the detrimental effects of carrier frequency offset (CFO), phase noise (PHN) and doubly-selective fading on orthogonal frequency division multiplexing (OFDM) transmission performance. In particular, we derive a closed-form expression for the signal-to-interference ratio (SIR) at an OFDM receiver in the presence of CFO, PHN and doubly-selective fading. Simulation and analytical results under various OFDM system settings are in good agreement and reveal the contributions of these channel impairments in the SIR degradation.

On the effect of phase noise and time-selective channel on OFDM transmission: SINR analysis

This paper studies the detrimental effect of phase noise on the performance of orthogonal frequency division multiplexing (OFDM) transmissions over time-selective channels. In the literature, most of existing papers analyze the performance of OFDM systems in the presence of either time-selective channels or phase noise. Unlike the existing studies, this paper formulates an approximate expression of signal-to-interference-plus-noise ratio (SINR) at an OFDM receiver in the presence of both phase noise and time-selective channel response. The formulated SINR expression can be used as guidelines in determining appropriate OFDM transmission settings under a given quality-of-service (QoS) requirement. To illustrate the tightness of the approximate SINR formulation, empirical and theoretical values of SINR under different OFDM system settings are presented in this paper.

Doubly selective channel estimation in full-duplex MIMO-OFDM systems

This paper studies the problem of frequency-and time-selective (doubly selective) channel estimation in full-duplex multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. In particular, the maximum-likelihood (ML) principle is employed to formulate a pilot-aided channel estimation algorithm. To reduce the number of doubly selective channel parameters to be estimated, various basis expansion models (BEMs) are used as fitting parametric models. The use of BEMs enables an increase in the system spectral efficiency since estimating a reduced number of channel parameters entails a reduction in used pilot overhead. This paper provides analytical and empirical results of the BEM-based channel estimation accuracy. Several mean square error (MSE) results show that the discrete prolate spheroidal (DPS) or Karhuen Loeve (KL) basis functions would be a suitable choice for BEM-based full-duplex doubly selective channel estimation.

Joint phase noise and doubly selective channel estimation in full-duplex MIMO-OFDM systems

This paper is concerned with the joint estimation of phase noise and time-varying channel responses in full-duplex multiple-input multiple-output (MEMO) orthogonal frequency division multiplexing (OFDM) systems. The time-variation of phase noise and multipath MIMO channel responses gives rise to the identiflability problem of estimating a large number of unknowns which is much greater than the number of received signal samples. To overcome the resulting identiflability estimation problem, this paper employs basis expansion models (BEM) for reducing the number of time-varying channel impairment parameters to be estimated. Using the BEM-based approximation of the channel impairment responses, this paper formulates a pilot-aided algorithm for maximum-a-posteriori (MAP)-based estimation of the BEM coefficients. This paper provides empirical mean squared error (MSE) results of the joint channel impairment parameter estimation and related analytical values of Bayesian Cramer Rao lower bounds (BCRLB). The numerical results illustrate that the use of BEM facilitates reliable estimation of the time-varying channel impairment responses whereas the corresponding MSE and bit-error-rate (BER) values are comparable to related BCRLBs and ideal BER ones, respectively.

Robust precoding and postcoding for multicell multiuser transmission using imperfect CSI

This paper studies the problem of precoding and post-coding design for multicell multiuser downlink transmissions in the absence of perfect channel state information (CSI). Using statistical information of imperfect CSI, an iterative multiuser multicell transceiver design is formulated by minimizing the mean squared error (MSE) cost function of signal and leakage interference under per-base station power constraint (PBPC). The convergence of the iterative precoding and postcoding algorithm is verified by analytical and empirical results. The proposed precoding and postcoding algorithm offers a low computational complexity and robustness against CSI imperfection.

Interference management over multicell broadcast channels

This paper is concerned with multiuser downlink transmissions in the presence of inter-cell interference (ICI). In the considered system, precoding at base stations (BS) and postcoding at users are jointly determined to manage both inter-user interference (IUI) and ICI under mean square error (MSE) criterion. Unlike zero-forcing based precoding, the proposed MSE-based precoding scheme still work as the number of transmit antennas at each BS is smaller than the total number of receive antennas at all users.

Multiuser precoding in MIMO two-way relay transmission

This paper is concerned with the problem of multiuser precoding design for multiple-output multiple-input (MIMO) two-way relay transmission. In the literature, most of existing studies on multiuser transmission over two-way relay channels have assumed that user terminals (i.e., source nodes) are equipped with a single antenna. To increase the capacity of the multiuser two-way relay network, this paper introduces precoding designs at source and relay nodes for space division multiple access (SDMA) transmissions between source nodes. Numerical simulation results show that the proposed precoding designs at multi-antenna source nodes (i.e., user terminals) can improve the capacity of the network.

Multiuser scheduling in two-way relay networks

This paper studies the problem of multiuser selection in multiple-input multiple-output (MIMO) two-way relay networks. In the literature, existing studies consider multiuser selection for relay networks having homogeneous terminals/users (each is equipped with one antenna). Unlike the existing studies, this paper is concerned with the problem of multiuser scheduling in two-way relay networks using space division multiple access (SDMA) for heterogeneous multiuser transmissions. Numerical simulation results show that using block-diagonalization (BD) precoding and greedy user selection can facilitate heterogeneous multiuser relay transmissions which offer higher system capacity than homogeneous multiuser relay transmissions.