Flexible Multi-Group Single-Carrier Modulation: Optimal Subcarrier Grouping and Rate Maximization

Orthogonal frequency division multiplexing (OFDM) and single-carrier frequency domain equalization (SC-FDE) are two commonly adopted modulation schemes for frequency-selective channels. Compared to SC-FDE, OFDM generally achieves higher data rate, but at the cost of higher transmit signal peak-to-average power ratio (PAPR) that leads to lower power amplifier efficiency. This paper proposes a new modulation scheme, called flexible multi-group single-carrier (FMG-SC), which encapsulates both OFDM and SC-FDE as special cases, thus achieving more flexible rate-PAPR trade-offs between them. Specifically, a set of frequency subcarriers are flexibly divided into orthogonal groups based on their channel gains, and SC-FDE is applied over each of the groups to send different data streams in parallel. We aim to maximize the achievable sum-rate of all groups by optimizing the subcarrier-group mapping. We propose two low-complexity subcarrier grouping methods and show via simulation that they perform very close to the optimal grouping by exhaustive search. Simulation results also show the effectiveness of the proposed FMG-SC modulation scheme with optimized subcarrier grouping in improving the rate-PAPR trade-off over conventional OFDM and SC-FDE.Comment: Submitted for possible conference publicatio

Algorithm based new Tone Reservation method for mitigating PAPR in OFDM systems

There are abundant methods to mitigate PAPR in OFDM signals among which algorithm based tone reservation is of great popularity owing to its low complexity as well as decent BER. Here we have put forward a new distinct algorithm based Tone Reservation technique which is not only less complex and calculates its own threshold as well as PRT signal (unlike other algorithms requiring predetermined threshold and PRT) but also aptly modifies the data by bit by bit comparison with a modified copy of itself (algorithm modified) thus scaling the peaks as and providing a decent BER and good PAPR reduction.

Analysis of Improved µ-Law Companding Technique for OFDM Systems

YesHigh Peak-to-Average-Power Ratio (PAPR) of transmitted signals is a common problem in broadband telecommunication systems using an orthogonal frequency division multiplexing (OFDM) modulation scheme, as it increases transmitter power consumption. In consumer applications where it impacts mobile terminal battery life and infrastructure running costs, this is a major factor in customer satisfaction. Companding techniques have been recently used to alleviate this high PAPR. In this paper, a companding scheme with an offset, amidst two nonlinear companding levels, is proposed to achieve better PAPR reduction while maintaining an acceptable bit error rate (BER) level, resulting in electronic products of higher power efficiency. Study cases have included the effect of companding on the OFDM signal with and without an offset. A novel closed-form approximation for the BER of the proposed companding scheme is also presented, and its accuracy is compared against simulation results. A method for choosing best companding parameters is presented based on contour plots. Practical emulation of a real time OFDM-based system has been implemented and evaluated using a Field Programmable Gate Array (FPGA)

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