Channel Estimation and Precoding in Closed-Loop Distributed Multi-Antenna Systems

  • Wild T.

Today's wireless cellular systems are limited by inter-cell interference. Coordinated multi-point transmission and reception (CoMP) is a promising approach to cope with this problem. Here, multiple base stations act as a distributed antenna system, exchanging coordination information and potentially user data via backhaul in order to reduce this interference, increasing spectral efficiency and generating a more homogeneous user experience throughout the entire cell, especially at the currently weak cell edges. This dissertation aims at enabling coordinated multi-point systems by dealing with its current realization challenges. Accurate channel knowledge is required both at transmitter and receiver side in order to realize the CoMP gains. Hence, practical channel estimation algorithms are investigated and developed in order to get as accurate channel knowledge as possible with manageable computational complexity under realistic system operation points. Especially the often neglected obtainment of statistical parameter knowledge is included here, which is challenging under dynamic user scheduling conditions. A multi-user multi-cell channel estimator is provided which, even for larger number of coordinated cells, can get receiver performance fairly close to performance with perfect channel knowledge. Furthermore, different downlink precoding and receive combining strategies are compared against each other under imperfect channel knowledge. As the number of coordinated cells - the cluster size - is limited in practice, mobiles at cluster edges suffer from inter-cluster interference. A novel patented precoding and control signaling scheme is introduced in order to deal with the inter-cluster interference.

Recent Publications

August 09, 2017

A Cloud Native Approach to 5G Network Slicing

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5G networks will have to support a set of very diverse and often extreme requirements. Network slicing offers an effective way to unlock the full potential of 5G networks and meet those requirements on a shared network infrastructure. This paper presents a cloud native approach to network slicing. The cloud ...

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Modeling and simulation of RSOA with a dual-electrode configuration

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Based on the physical model of a bulk reflective semiconductor optical amplifier (RSOA) used as a modulator in radio over fiber (RoF) links, the distributions of carrier density, signal photon density, and amplified spontaneous emission photon density are demonstrated. One of limits in the use of RSOA is the lower ...

July 12, 2017

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How to preserve users' privacy while supporting high-utility analytics for low-latency stream processing? To answer this question: we describe the design, implementation and evaluation of PRIVAPPROX, a data analytics system for privacy-preserving stream processing. PRIVAPPROX provides three properties: (i) Privacy: zero-knowledge privacy (ezk) guarantees for users, a privacy bound tighter ...