Multi-Antenna Techniques for Next Generation Cellular Communications

Aalto University, P.O. Box 11000, FI-00076 Aalto www.aalto. fi Author Umut Ugurlu Name of the doctoral dissertation Multi-Antenna Techniques for Next Generation Celular Communications Publisher School of Electrical Engineering Unit Department of Signal Processing and Acoustics Series Aalto University publication series DOCTORAL DISSERTATIONS 156/2016 Field of research Signal Processing for Communications Manuscript submited 9 November 2015 Date of the defence 2 September 2016 Permission to publish granted (date) 18 February 2016 Language English Monograph Article dissertation Essay dissertation Abstract Future celular communications are expected to offer substantial improvements for the preexisting mobile services with higher data rates and lower latency as wel as pioneer new types of applications that must comply with strict demands from a wider range of user types. Al of these tasks require utmost efficiency in the use of spectral resources. Deploying multiple antennas introduces an additional signal dimension to wireless data transmissions, which provides a significant alternative solution against the plateauing capacity issue of the limited available spectrum. Multi-antenna techniques and the associated key enabling technologies possess unquestionable potential to play a key role in the evolution of next generation celular systems. Spectral efficiency can be improved on downlink by concurrently serving multiple users with high-rate data connections on shared resources. In this thesis optimized multi-user multiinput multi-output (MIMO) transmissions are investigated on downlink from both filter design and resource alocation/assignment points of view. Regarding filter design, a joint baseband processing method is proposed specificaly for high signal-to-noise ratio (SNR) conditions, where the necessary signaling overhead can be compensated for. Regarding resource scheduling, greedyand genetic-based algorithms are proposed that demand lower complexity with large number of resource blocks relative to prior implementations. Channel estimation techniques are investigated for massive MIMO technology. In case of channel reciprocity, this thesis proposes an overhead reduction scheme for the signaling of user channel state information (CSI) feedback during a relative antenna calibration. In addition, a multi-cel coordination method is proposed for subspace-based blind estimators on uplink, which can be implicitly translated to downlink CSI in the presence of ideal reciprocity. Regarding non-reciprocal channels, a novel estimation technique is proposed based on reconstructing ful downlink CSI from a select number of dominant propagation paths. The proposed method offers drastic compressions in user feedback reports and requires much simpler downlink training processes. Ful-duplex technology can provide up to twice the spectral efficiency of conventional resource divisions. This thesis considers a ful-duplex two-hop link with a MIMO relay and investigates mitigation techniques against the inherent loop-interference. Spatial-domain suppression schemes are developed for the optimization of ful-duplex MIMO relaying in a coverage extension scenario on downlink. The proposed methods are demonstrated to generate data rates that closely approximate their global bounds.Future celular communications are expected to offer substantial improvements for the preexisting mobile services with higher data rates and lower latency as wel as pioneer new types of applications that must comply with strict demands from a wider range of user types. Al of these tasks require utmost efficiency in the use of spectral resources. Deploying multiple antennas introduces an additional signal dimension to wireless data transmissions, which provides a significant alternative solution against the plateauing capacity issue of the limited available spectrum. Multi-antenna techniques and the associated key enabling technologies possess unquestionable potential to play a key role in the evolution of next generation celular systems. Spectral efficiency can be improved on downlink by concurrently serving multiple users with high-rate data connections on shared resources. In this thesis optimized multi-user multiinput multi-output (MIMO) transmissions are investigated on downlink from both filter design and resource alocation/assignment points of view. Regarding filter design, a joint baseband processing method is proposed specificaly for high signal-to-noise ratio (SNR) conditions, where the necessary signaling overhead can be compensated for. Regarding resource scheduling, greedyand genetic-based algorithms are proposed that demand lower complexity with large number of resource blocks relative to prior implementations. Channel estimation techniques are investigated for massive MIMO technology. In case of channel reciprocity, this thesis proposes an overhead reduction scheme for the signaling of user channel state information (CSI) feedback during a relative antenna calibration. In addition, a multi-cel coordination method is proposed for subspace-based blind estimators on uplink, which can be implicitly translated to downlink CSI in the presence of ideal reciprocity. Regarding non-reciprocal channels, a novel estimation technique is proposed based on reconstructing ful downlink CSI from a select number of dominant propagation paths. The proposed method offers drastic compressions in user feedback reports and requires much simpler downlink training processes. Ful-duplex technology can provide up to twice the spectral efficiency of conventional resource divisions. This thesis considers a ful-duplex two-hop link with a MIMO relay and investigates mitigation techniques against the inherent loop-interference. Spatial-domain suppression schemes are developed for the optimization of ful-duplex MIMO relaying in a coverage extension scenario on downlink. The proposed methods are demonstrated to generate data rates that closely approximate their global bounds.