Design of Joint Spatial and Power Domain Multiplexing Scheme for Massive MIMO Systems

Massive Multiple-Input Multiple-Output (MIMO) is one of the key techniques in 5th generation wireless systems (5G) due to its potential ability to improve spectral efficiency. Most of the existing works on massive MIMO only consider Time Division Duplex (TDD) operation that relies on channel reciprocity between uplink and downlink channels. For Frequency Division Duplex (FDD) systems, with continued efforts, some downlink multiuser MIMO scheme was recently proposed in order to enable “massive MIMO” gains and simplified system operations with limited number of radio frequency (RF) chains in FDD system. However these schemes, such as Joint Spatial Division and Multiplexing (JSDM) scheme and hybrid precoding scheme, only focus on multiuser transmission in spatial domain. Different from most of the existing works, this paper proposes Joint Spatial and Power Multiplexing (JSPM) scheme in FDD systems. It extends existing FDD schemes from spatial division and multiplexing to joint spatial and power domain to achieve more multiplexing gain. The user grouping and scheduling scheme of JSPM is studied and the asymptotic expression for the sum capacity is derived as well. Finally, simulations are conducted to illustrate the effectiveness of the proposed scheme

Multi-user Linear Precoding for Multi-polarized Massive MIMO System under Imperfect CSIT

The space limitation and the channel acquisition prevent Massive MIMO from being easily deployed in a practical setup. Motivated by current deployments of LTE-Advanced, the use of multi-polarized antennas can be an efficient solution to address the space constraint. Furthermore, the dual-structured precoding, in which a preprocessing based on the spatial correlation and a subsequent linear precoding based on the short-term channel state information at the transmitter (CSIT) are concatenated, can reduce the feedback overhead efficiently. By grouping and preprocessing spatially correlated mobile stations (MSs), the dimension of the precoding signal space is reduced and the corresponding short-term CSIT dimension is reduced. In this paper, to reduce the feedback overhead further, we propose a dual-structured multi-user linear precoding, in which the subgrouping method based on co-polarization is additionally applied to the spatially grouped MSs in the preprocessing stage. Furthermore, under imperfect CSIT, the proposed scheme is asymptotically analyzed based on random matrix theory. By investigating the behavior of the asymptotic performance, we also propose a new dual-structured precoding in which the precoding mode is switched between two dual-structured precoding strategies with 1) the preprocessing based only on the spatial correlation and 2) the preprocessing based on both the spatial correlation and polarization. Finally, we extend it to 3D dual-structured precoding.Comment: accepted to IEEE Transactions on Wireless Communication

Massive MIMO σε 5G

Η παρούσα διπλωματική εργασία έχει ως αντικείμενο της τεχνολογίας του Massive MIMO σε δίκτυα 5ης γενιάς. Η τεχνολογία του Massive MIMO προσφέρει δυο βασικά πλεονεκτήματα για τα συστήματα 5ης γενιάς, τα οποία είναι η εξαιρετική φασματική απόδοση, καθώς και ιδιαίτερα υψηλή ενεργειακή απόδοση. Η εργασία διαρθρώνεται ως εξής: Στο πρώτο κεφάλαιο γίνεται μια συνοπτική αναφορά στα δίκτυα 5ης γενιάς, στις δυνατότητες αλλά και τις απαιτήσεις αυτών, καθώς και μια εισαγωγή στην τεχνολογία MIMO και τις κατηγορίες αυτής, παράλληλα με σύντομη ανάλυση του τρόπου λειτουργίας αυτών. Στο δεύτερο κεφάλαιο, αναλύονται ορολογίες απαραίτητες για την περιγραφή του ασύρματου καναλιού. Επιπρόσθετα, περιγράφονται τύποι ασύρματων καναλιών διαφορετικών χαρακτηριστικών. Στο τρίτο κεφάλαιο παρουσιάζεται η αρχιτεκτονική των υβριδικών στοιχειοκεραιών για την τεχνολογία Massive MIMO, όπου συνδυάζονται οι τεχνολογίες των αναλογικών και των ψηφιακών στοιχειοκεραιών, με σκοπό την κάλυψη των απαιτήσεων των δικτύων 5ης γενιάς. Στο τέταρτο κεφάλαιο πραγματοποιείται μια ανάλυση της τεχνολογίας του Massive MIMO ως προς το επίπεδο ζεύξης. Παρουσιάζονται οι διαφορετικές τεχνικές beamforming, η τεχνική της χωρικής πολυπλεξίας, και πως αυτές επηρεάζουν τη χωρητικότητα και τη συνολική απόδοση του επιπέδου ζεύξης.This thesis deals with Massive MIMO technology in 5G networks. Massive MIMO technology offers two key advantages for 5G systems, which are excellent spectral efficiency as well as particularly high energy efficiency. The work is structured as follows: In the first chapter there is a brief reference to 5G networks, their capabilities and requirements, as well as an introduction to MIMO technology and its categories, along with a brief analysis of how they work. In the second chapter, terminologies necessary to describe the wireless channel are analyzed. In addition, types of wireless channels of different characteristics are described. The third chapter presents the architecture of hybrid array antennas for Massive MIMO technology, combining analogue and digital array antenna technologies to meet the requirements of 5G networks. In the fourth chapter an analysis of Massive MIMO's technology from a link level perspective is performed. The different beamforming techniques, the technique of spatial multiplexing, and how these affect the capacity and overall performance of the coupling level are presented