Marco Driusso

Design Criteria and Genetic Algorithm Aided Optimization of Three-Stage-Concatenated Space-Time Shift Keying Systems

The Space-Time Shift Keying (STSK) framework subsumes diverse Multiple-Input Multiple-Output (MIMO) schemes, offering a near-capacity performance at a reduced complexity. The STSK systems performance crucially depends on the dispersion matrix (DM) set used for encoding the transmitted symbols. We introduce a novel criterion, based on EXtrinsic Information Transfer (EXIT) chart analysis, for selecting capacity-approaching sets from candidate DMs, and a novel Genetic Algorithm (GA) for efficiently exploring the search space formed by the candidate DM sets. Our proposed GA allows obtaining DM sets that enhance the systems performance compared to a random selection, while simultaneously reducing the search algorithms complexity.

OFDM Aided Space-Time Shift Keying for Dispersive Downlink Channels

The performance of a Space-Time Shift Keying (STSK) scheme was shown to degrade in frequency-selective fading channels. Hence, we propose Orthogonal Frequency Division Multiplexing (OFDM) combined with STSK for frequency-selective broadband channels. Furthermore, we consider both an uncoded and a near-capacity coded scenario. Our results show that a STSK system combined with OFDM is capable of overcoming the impairments of dispersive channels, hence approaching the same performance as in a flat- fading channel.

Vehicular Position Tracking Using LTE Signals

This paper proposes and validates, in the field, an approach for position tracking that is based on Long-Term Evolution (LTE) downlink signal measurements. A setup for real data live gathering is used to collect LTE signals while driving a car in the town of Rapperswil, Switzerland. The collected data are then processed to extract the received LTE cell-specific reference signals (CRSs), which are exploited for estimating pseudoranges. More precisely, the pseudoranges are evaluated by using the “ESPRIT and Kalman Filter for Time-of-Arrival Tracking” (EKAT) algorithm and by taking advantage of signal combining in the time, frequency, spatial, and cell ID domains. Finally, the pseudoranges are corrected for base stations clock bias and drift, which are previously estimated, and are used in a positioning filter. The obtained results demonstrate the feasibility of a position tracking system based on the reception of LTE downlink signals.

Estimation and tracking of LTE signals time of arrival in a mobile multipath environment

This paper proposes an algorithm for the estimation and tracking of the direct path (DP) time of arrival (TOA) of the signals received from 4G long term evolution (LTE) cellular base stations (BSs) in a mobile multipath environment. This is important for TOA-based ranging measurements, which may be exploited for positioning applications. A sub-space approach is used for the estimation of the multipath time of arrival, and a state-space approach is exploited for tracking the direct path. The developed framework is applied to real LTE signals collected using a portable experimental setup during a car drive in the town of Rapperswil, Switzerland. The pseudoranges derived from the tracking of the DP TOA are then compared to the ranges from the considered LTE base stations calculated using GPS, demonstrating the effectiveness of the proposed approach.

Performance Analysis of Time of Arrival Estimation on OFDM Signals

This letter characterizes the error performance of realistically modelled orthogonal frequency division multiplexing (OFDM) signals, when their time of arrival has to be estimated in an additive white Gaussian noise channel. In particular, different power distributions on the available sub-carriers of the OFDM signal are considered, and bounds on the corresponding root mean square estimation error (RMSEE) are evaluated. The tools used for such purpose are the widely adopted Cramér-Rao bound and the Ziv-Zakai bound, which is tight in a wide range of signal-to-noise ratio (SNR) values. The presented analysis reveals that, for a given signal bandwidth, a proper power distribution on the OFDM sub-carriers is crucial for achieving a good performance in the low to medium SNR region, where the RMSEE curve exhibits the typical threshold behavior. Moreover, a trade-off between asymptotic and threshold performance is identified, thanks to the adoption of a novel performance figure, which directly describes the threshold RMSEE behavior.

Discrete-time simulation of smart antenna systems in Network Simulator-2 Using MATLAB and Octave

This paper presents two platforms that exploit the scalability properties of Network Simulator-2 for the discrete-event simulation of a telecommunication network, and the modeling capabilities of two development tools for the discrete-time implementation of adaptive antenna arrays at the physical layer. The two tools are the proprietary MATLAB and the open source Octave, both of which are used to implement the physical antenna system, the beamforming algorithm, the channel coding scheme, and the multipath and fading statistics. The adopted approach enables detailed modeling of the antenna radiation pattern generated by each network node, thus improving the accuracy of the signal-to-interference ratio estimated at the receiver. This study describes the methods that can be adopted to interface MATLAB and Octave with Network Simulator-2, and discusses the advantages and disadvantages that characterize the integration of the two tools with Network Simulator-2. The proposed numerical platforms, which can be interfaced with any wireless network supported by Network Simulator-2, are used to investigate the possibility of exploiting smart antenna systems in a wireless mesh network to enable the coexistence of multiple simultaneous communications.

Indoor positioning using LTE signals

This paper presents an experiment using real Long-Term Evolution (LTE) signals to extend positioning from outdoors to indoors. LTE signals are of interest for positioning applications because of their availability indoors, where GNSS signal reception is limited. Different approaches for time of arrival (TOA) extraction are evaluated for their positioning performance, combined with an extended Kalman filter (EKF) for movement tracking. The paper shows that the performance is surprisingly good, with high visibility of cellular signals even in the difficult indoor test environment, and with a positioning error once indoors smaller than 8m in 50% of cases.

A simple method for TOA estimation in OFDM systems

In this paper a simple algorithm for the estimation of the Direct Path (DP) Time of Arrival (TOA) in an OFDM-based telecommunications system is proposed. It is shown that, under certain conditions, it is possible to infer the TOA of the direct path by estimating the phase slope across the subcarriers. The proposed algorithm exploits the intrinsic properties of a multi-carrier OFDM system to perform the estimation, and it can be employed in a fully opportunistic way if known reference signals (intended for purposes other than TOA estimation) are available. The obtained TOA estimations can be used to calculate the pseudo-ranges that can be employed for trilateration-based positioning. The performance of the proposed algorithm and its variants are assessed with simulations.

A low-complexity approach for time of arrival estimation in OFDM systems

This paper proposes a novel algorithm for Time of Arrival (ToA) estimation in Orthogonal Frequency Division Multiplexing (OFDM) systems. The algorithm performs the estimation starting from the channel frequency samples, in a fully opportunistic way when some known reference signals are already available for operations different from ToA estimation itself. The developed solution, named Difference-Based ToA Estimation (DBTE), exploits the intrinsic properties of a multi-carrier OFDM system to calculate the ToA with a low computational cost. The conceived technique is compared with other existing methods in terms of performance and computational time, in order to outline the interesting accuracy/complexity trade-off that characterizes the presented approach.

Outdoor and indoor experiments with localization using LTE signals

This paper reports experiments with realistic positioning using LTE downlink signals measurements. Sets of real live samples of LTE signals have been gathered during outdoor and indoor acquisitions in the town of Rapperswil, Switzerland. The collected data is then processed using a Super Resolution Algorithm in order to extract the received LTE cell specific reference signals, which are used to estimate the pseudoranges. Both an Extended Kalman Filter and an Iterative Least Squares algorithm are evaluated for processing the pseudoranges to obtain the location and time. The algorithms are compared and their different applications are discussed. The features and limitations of LTE signals and networks are also discussed and their impact on positioning performance assessed. The results show that positioning using LTE signals can achieve remarkable performance (50% error quantile as low as 6 m), and that their use is potentially suitable for indoor as well as outdoor applications.