Georgia Bournaka

An SINR balancing based multiuser relaying scheme

We consider a relay network with multiple users and propose a signal-to-interference and noise-ratio (SINR) balancing based relay signal forwarding scheme. Each relay receives a combined signal from multiple sources and processes it using a complex valued scalar and transmits towards the destinations so that the SINR at the receiver of each user is maximised. We solve this problem using semidefinite and geometric programming along with bisection search methods. The performance of the proposed scheme has been studied in terms of worst case SINR for various numbers of users and relays.

Experimental validation of Kalman filter based tracking in passive radar systems

Target localization and tracking capabilities of a passive radar system based on exploitation of DVB-T transmission as a signal of opportunity are demonstrated. The results are based on a real data acquisition campaign performed using an eleven elements antenna based passive radar developed at FHR in Germany. Specifically, the experiment considered a scenario of two small fast maneuvering targets and the passive radar system is able to discriminate and track the fast maneuvering targets.

Base station beamforming technique using multiple signal-to-interference plus noise ratio balancing criteria

The authors propose a coordinated multi-cell beamforming technique for signal-to-interference plus noise ratio (SINR) balancing under multiple base station power constraints. Instead of balancing SINR of all users in all cells to the same level, the authors’ propose a new approach to balance SINR of users in various cells to different maximum possible values. This has the ability to allow users in cells with relatively more transmit power or better channel condition to achieve a higher balanced SINR than that achieved by users in the worst-case cells. This multi-level SINR balancing problem is solved using SINR constraints based SINR balancing criterion and subgradient method. The simulation results support the optimality of the results through comparison with semi-definite programming-based optimisation.

An Iterative Semidefinite and Geometric Programming Technique for the SINR Balancing in Two-Way Relay Network

In this paper, we consider a two-way amplify-and-forward relaying scheme, which consists of multiple transceivers and r relay nodes. Assuming that both the transceivers and the relays are equipped with single antennas, we deploy a signal-to-interference and noise-ratio (SINR) balancing technique, where the smallest of the transceivers SINRs is maximized under a total transmit power constraint. We solve this problem through an iterative procedure that uses semidefinite and geometric programming along with bisection search methods. We evaluate the performance of the proposed scheme in terms of the mean SINR for various relays and power at the relays.

A two stage beamforming approach for low complexity CFAR detection and localization for passive radar

We propose a two stage beamforming technique for localisation of moving target in a passive radar environment. In order to perform localization and tracking in Cartesian plane, in addition to detection in the range Doppler domain, it is necessary to have angle of arrival of target return, which is obtained using beamforming. The beamforming technique can also enhance signal to disturbance ratio. However, performing constant false alarm rate detection (CFAR) in this case requires storing beamformer output statistics for every range-Doppler-azimuth bin which significantly burdens the system and hinders the real time processing and tracking of moving targets. Using experimental measurements, we demonstrate real time detection and tracking of an airborne target using a two stage beamforming approach, where a smaller set of beams is used in the first stage for CFAR detection and a larger set of beams is used in the second stage for angle of arrival estimation with higher accuracy.

An SINR Balancing Technique for a Cognitive Two-Way Relay Network

We propose a two-way relay based spatial multiplexing technique for a cognitive radio relay network (CR). The relay coefficients and the transmission powers are optimized to maximize the worst-case user signal-to interference and noise ratio (SINR), while ensuring interference leakage from the relays to the primary users (PUs) in the network is below a threshold. We solve this problem through an iterative procedure that uses semidefinite and geometric programming along with bisection search method. We evaluate the performance of the proposed scheme in terms of the mean SINR for different number of relays and transmission power at the relays.

Multipath clutter cancellation and tracking algorithms for passive radars

We demonstrate the ability of a passive radar system to monitor a large area of interest by applying advanced multipath clutter cancellation algorithm, spatial beamforming and tracking techniques. The mitigation of clutter disturbance and a two stage beamforming method facilitate real time tracking of small to moderate size targets in real Cartesian domain. The results have been validated through a real data acquisition campaign performed using an eleven element array antenna based passive radar developed at FHR Institute in Germany.

Experimental validation of beamforming techniques for localization of moving target in passive radar

We investigate the performance of a Bucci based beamformer design and MUSIC algorithm under a passive radar setup using experimental measurements. A uniformly spaced linearly array of 11 discone antennas was used for the passive radar. The experiment was performed by exploiting the DVB-T broadcasting station as the illuminator of opportunity. In order to suppress the direct reference signal and clutters, the beamforming and MUSIC algorithms have been applied to the range-Doppler processed data; however, challenges remain due to very low SNR. This work proposes spatial smoothing based Bucci algorithm whose angle of arrival estimation performance is comparable to that of the MUSIC algorithm, however, this method does not need the computationally expensive singular value decomposition.

Coordinated beamforming with mixed SINR-balancing and SINR-target-constraints for multicell wireless networks

We propose a coordinated multicell beamformer design method based on the signal-to-interference-plus-noise ratios (SINRs) balancing technique within the context of mixed quality of services (QoS). Instead of attaining an overall balance of SINRs to all users in all cells, the proposed algorithm allows a specific subset of users in each cells to achieve certain target SINRs while the SINRs of the remaining users in all cells are balanced subject to the total transmission power. The uplink-downlink duality is used for converting the downlink problem into the uplink beamformer design problem. The semidefinite programming (SDP) method is used to check the optimality.

Experimental Study for Transmitter Imperfections in DVB-T Based Passive Radar

We investigate effects of transmitter imperfections in terms of time and frequency offsets on the performance of digital video broadcast-terrestrial based passive radars. To facilitate an accurate reconstruction of the transmitted waveform, transmitter imperfections need to be understood and compensated. The transmitter introduced clock imperfections are estimated and compensated via two different methods and tested on real-field measurements acquired in Germany and Australia for single frequency and multiple frequency networks.