Akademik Veri Yönetim Sistemi
Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Elektrik Ve Elektronik Mühendisliği Bölümü, Türkiye
Tezin Onay Tarihi: 2023
Tezin Dili: İngilizce
Öğrenci: GÖKHAN YILMAZ
Danışman: Ali Özgür Yılmaz
Özet:
Analog-to-digital converter (ADC) units are one of the most power-hungry devices in
the radio-frequency (RF) chains of massive multiple-input multiple-output (MIMO)
systems. Therefore, utilizing low-resolution ADCs in uplink massive MIMO systems
is a practical solution to decrease power consumption. However, when high modulation
orders are employed for high-rate communication, the achievable rate saturates after
a finite SNR value due to the stochastic resonance (SR) phenomenon. This thesis
proposes a novel pseudo-random quantization (PRQ) scheme that can help compensate
for the effects of SR and makes communication with high-order modulation schemes
with one-bit quantization possible. The ADC thresholds at the receiver side of uplink
one-bit massive MIMO systems are changed to work with the PRQ scheme. We
modify linear detectors for one-bit non-zero threshold quantization and propose new
detection methods for the frequency-flat and frequency-selective fading scenarios. For
flat fading, we offer a two-stage detector that works with PRQ. The first stage is an
iterative method called Boxed Newton Detector (BND) that utilizes Newton’s method
to maximize the log-likelihood. The second stage, Nearest Codeword Detector (NCD),
exploits the first stage to create a small set of most likely candidates based on sign
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constraints to increase performance. For frequency-selective fading, we design a new
frequency-domain equalization (FDE) scheme, called the projected quasi-Newton
detector (PQND), to optimize the log-likelihood using a quasi-Newton approach that
works with PRQ in both orthogonal frequency division multiplexing (OFDM) and
single carrier (SC) systems. The proposed methods outperform the existing detectors
with comparable complexity