Space-Time Processing algorithms

Our traditional research topic at SARG is the development of space-time processing algorithms. These include advanced multiple access schemes, bandwidth-efficient coding and signal processing techniques. The use of space-time processing is a powerful tool for improving the performance of wireless communication networks by employing multiple antennas at the transmitter and/or receiver. Space-time processing can increase system capacity, enhance link quality and improve cell coverage.

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Contact: Prof. Arogyaswami Paulraj

Wireless Ad-Hoc Relay Networks

Our research comprises the performance analysis of basic communication structures arising in wireless ad-hoc and relay networks. Information Theory: We are interested in the information theoretical capacity bounds of such structures as well as the impact of different network geometries,  such as placement and location of nodes, on the coverage performance. The analysis involves simple single antenna, as well as multiple antenna nodes, possibly using network coding and spatial precoding strategies.  The investigation requires the application of different tools ranging from majorization theory, random matrix theory, information theory and signal processing. We are also interested in the application of majorization theory in a variety of fields such as biology, random graph theory and stochastic processes. Contact: Aydin Sezgin Network Coding: In information-flow networks, the available multicast capacity cannot be achieved by simple rouing protocols, except for a very limited number of network configurations. However, using network coding, one is able to reach the multicast capacity in any network. We currently conduct research on the capacity implications of network coding over random wireless ad-hoc networks. We also investigate the information theoretic capacity of network coding over relay channels. Contact: Gökmen Altay

Interference in Wireless Networks

We are interested in the role of interference in wireless channels, in both ad-hoc and traditional cellular systems. Modern cellular networks are becoming increasingly interference limited as cell sizes shrink to accommodate a growing number of users. Scheduling techniques that exploit channel state information can make use of multiuser diversity to mitigate such interference. We are interested in quantifying the benefit of such techniques and in assessing the practicality of such schemes. Interference can also severely limit the capacity of ad-hoc networks. We study how local channel-aware scheduling can be used to handle this problem so that the spectrum may be used more efficiently. Our research concentrates on information-theoretical approaches (e.g., the Gaussian interference channel), schemes and algorithms that handle interference in practice, and providing realistic models of the the interference channel. In particular, some of our research questions in this area are: How is the interplay between known results in the interference channel and the spatial dimension in MIMO systems? Interference alignment and the deterministic interference model Game-theoretic approaches to the interference channel Spatial correlation of the interference channel Contact: Bernd Bandemer, Stephanie Pereira, Nicolai Czink

Multi-Antenna Channel Measurements and Modelling

Using our state-of-the-art RUSK Stanford channel sounder, we have the capability to accurately measure the time-varying multi-antenna radio channel. Our current research focuses on: the characterization of small antenna arrays for WiMAX applications spatial properties of MIMO interference multi-node measurements characterizing the collaborative ad-hoc channel Contact: Nicolai Czink

Wideband Beamforming for a Planar Phased Array with Antenna Switching

In recent years, there exists a significant interest in the development of advanced wireless systems with planar arrays of antennas as an essential component of the system. In conventional multichannel antenna array systems, the number of receivers should be equal to the number of receiving antennas, and thus the hardware expense and power consumption of such a system is considerably high. An array system based on antenna switching is a promising substitute for the multichannel array due to its lower cost and a simpler front-end circuitry. In this research, we propose beamforming algorithms for estimating the azimuth angle, elevation angle, velocity, and range using a planar phased array with antenna switching. Contact: Moon-Sik Lee