571 research outputs found
Low Complexity Noncoherent Iterative Detector for Continuous Phase Modulation Systems
This paper focuses on the noncoherent iterative detection of continuous phase modulation. A class of simplified receivers based on Principal-Component-Analysis (PCA) and Exponential-Window (EW) is developed. The proposed receiver is evaluated in terms of minimum achievable Euclidean distance, simulated bit error rate and achievable capacity. The performance of the proposed receiver is discussed in the context of mismatched receiver and the equivalent Euclidean distance is derived. Analysis and numerical results reveal that the proposed algorithm can approach the coherent performance and outperforms existing algorithm in terms of complexity and performance. It is shown that the proposed receiver can significantly reduce the detection complexity while the performance is comparable with existing algorithms
Design of Waveform Set for Multiuser Ultra-Wideband Communications
The thesis investigates the design of analogue waveform sets for multiuser and UWB communications using suitably
chosen Hermite-Rodriguez basis functions. The non-linear non-convex optimization problem with time and frequency
domains constraints has been transformed into suitable forms and then solved using a standard optimization package.
The proposed approach is more flexible and efficient than existing approaches in the literature. Numerical results show
that orthogonal waveform sets with high spectral efficiency can be produced
PLC for the smart grid: state-of-the-art and challenges
This paper aims to review systems and applications for power line communications (PLC) in the context of the smart grid. We discuss the main applications and summarise state-of-the-art PLC systems and standards. We report efforts and challenges in channel and noise modelling, as well as in state-of-the-art transmission technology approaches
Pilot based single user frequency offset estimation in spectrally-overlapping FDMA CPM systems
The spectral efficiency of a frequency division multiple access system can be increased by allowing some spectral overlap of adjacent user signals, at the expense of higher interuser interference. We derive the linearized mean square error of pilot based single user maximum likelihood frequency offset estimation in such a system, assuming continuous phase modulation. We consider synchronous as well as asynchronous reception of the pilot signals from the various users. Moreover, the pilot signals are assumed to be either constant and equal to 1, or pseudo-random and independent for all users. In spite of the presence of interuser interference, we obtain relatively simple closed-form expressions, from which the effect of the modulation parameters, the pilot signal structure and the number of users is easily derived
Advanced low-complexity multiuser receivers
It tema centrale di questa tesi Ăš la rivelazione multi-utente per sistemi di comunicazione wireless ad elevata efficienza spettrale.
Lo scopo del lavoro Ăš quello di proporre nuovi ricevitori multi-utente a bassa complessitĂ con elevate prestazioni.
Sono considerati sistemi satellitari basati su FDM (Frequency Division Multiplexing), in cui ogni utente adotta una modulazione
CPM (Continuous Phase Modulation) concatenata serialmente con un codificatore tramite un interlacciatore e decodifica iterativa.
Si considerano, inoltre, canali lineari in presenza di AWGN (additive white Gaussian noise). In particolare, si studiano sistemi FDM, in cui i canali adiacenti possono sovrapporsi in frequenza per aumentere l'efficienza spettrale, e sistemi CDMA (code division multiple access).
Per gli scenari presi in esame, proponiamo schemi di rivelazione con un eccellente compromesso tra prestazioni e complessitĂ computazionale, che permettono di implementare schemi di trasmissione con straordinaria efficienza spettrale, al prezzo di un limitato aumento di complessitĂ rispetto ad un classico ricevitore singolo-utente che ignora l'interferenza.This thesis deals with multiuser detection (MUD) for spectrally-efficient wireless communication systems. The aim of this work is to propose new advanced low-complexity multiuser receivers with near-optimal detection performance. We consider frequency division multiplexing (FDM) satellite systems where each user employs a continuous phase modulation (CPM), serially
concatenated with an outer code through an interleaver, and iterative detection/decoding. We also consider linear channels impaired by additive white
Gaussian noise (AWGN), focusing on FDM systems where adjacent channels
are allowed to overlap in frequency, and on code division multiple access systems (CDMA).
For the considered scenarios, we propose detection schemes with an excel-
lent performance/complexity tradeoff which allow us to implement transmission schemes with unprecedented spectral efficiency at a price of a limited
complexity increase with respect to a classical single-user receiver which neglects the interference
Information Transmission using the Nonlinear Fourier Transform, Part III: Spectrum Modulation
Motivated by the looming "capacity crunch" in fiber-optic networks,
information transmission over such systems is revisited. Among numerous
distortions, inter-channel interference in multiuser wavelength-division
multiplexing (WDM) is identified as the seemingly intractable factor limiting
the achievable rate at high launch power. However, this distortion and similar
ones arising from nonlinearity are primarily due to the use of methods suited
for linear systems, namely WDM and linear pulse-train transmission, for the
nonlinear optical channel. Exploiting the integrability of the nonlinear
Schr\"odinger (NLS) equation, a nonlinear frequency-division multiplexing
(NFDM) scheme is presented, which directly modulates non-interacting signal
degrees-of-freedom under NLS propagation. The main distinction between this and
previous methods is that NFDM is able to cope with the nonlinearity, and thus,
as the the signal power or transmission distance is increased, the new method
does not suffer from the deterministic cross-talk between signal components
which has degraded the performance of previous approaches. In this paper,
emphasis is placed on modulation of the discrete component of the nonlinear
Fourier transform of the signal and some simple examples of achievable spectral
efficiencies are provided.Comment: Updated version of IEEE Transactions on Information Theory, vol. 60,
no. 7, pp. 4346--4369, July, 201
Coexistence of high-bit-rate quantum key distribution and data on optical fiber
Quantum key distribution (QKD) uniquely allows distribution of cryptographic
keys with security verified by quantum mechanical limits. Both protocol
execution and subsequent applications require the assistance of classical data
communication channels. While using separate fibers is one option, it is
economically more viable if data and quantum signals are simultaneously
transmitted through a single fiber. However, noise-photon contamination arising
from the intense data signal has severely restricted both the QKD distances and
secure key rates. Here, we exploit a novel temporal-filtering effect for
noise-photon rejection. This allows high-bit-rate QKD over fibers up to 90 km
in length and populated with error-free bidirectional Gb/s data communications.
With high-bit rate and range sufficient for important information
infrastructures, such as smart cities and 10 Gbit Ethernet, QKD is a
significant step closer towards wide-scale deployment in fiber networks.Comment: 7 pages, 5 figure
Next-generation optical access networks based on Orthogonal Frequency Division Multiplexing
Orthogonal Frequency Division Multiplexing (OFDM) is a robust modulation and multiplexing format which is at the base of many present communication standards.
The interest of the OFDM application in optical fiber deployments is quite recent. As the next generation of Passive Optical Networks (NG-PONs) is envisioned, targeting greater capacity and user counts, the limitations of TDMA (Time Division Multiplexing Access) approaches to meet the expected increase in requirements becomes evident and therefore new technologies are being explored. Optical OFDMA is an emerging technology which can be a promising candidate.
The main goal of this Master Thesis is to study the problem of users multiplexing in access networks, using OFDM as a technology to transmit the user information data. This work has focused in the uplink study of the network, because it is the most challenging part of the network to design.
The studies have been conducted both in a theoretical way and also by simulating the targeted environments by means of a fiber optics transmission simulation tool. Virtual Photonics Integrated (VPI) is the software selected for the simulations. This tool is specially designed to simulate optical transmission system environments.
The analysis of the Optical Beat Interference, which is a critical impairment in optical carrier multiplexing schemes, is the most important part of the user
multiplexing study
Nonorthogonal coding in spectrally-entangled photons
Controlling and engineering continuous spectral modes of entangled photons
represents one of the promising approaches toward secure quantum
communications. By using the telecom bandwidth generated from a cascade-emitted
biphoton in atomic ensembles, a fiber-based long-distance quantum communication
can be feasible owing to its low transmission loss. With multiplexed photon
pairs, we propose to implement a nonorthogonal coding scheme in their spectral
modes and present an architecture of multiple channels enabling a high-capacity
transfer of codewords. Using the measures of the second-order correlations and
associated visibility and contrast, we further quantify the performance of the
proposed nonorthogonal coding scheme. Our results demonstrate the capability to
encode and decode quantum information beyond the orthogonal coding scheme. The
proposed scheme here can be applicable to a large-scale and multiuser quantum
communication and pave the way toward an efficient and functional quantum
information processing.Comment: Four figure
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