5 research outputs found
Electronic processing for optical communication systems
I sistemi di comunicazione in fibra ottica risentono di diversi tipi di disturbi, quali ad esempio la dispersione cromatica e la dispersione dei modi di polarizzazione. La compensazione ottica di tali disturbi è possibile ma complessa e costosa, mentre le tecniche di elaborazione elettronica del segnale presentano diversi vantaggi, semplicità , costo, adattabilità . L'equalizzazione elettronica e la strategia di rivelazione di sequenza a massima verosimiglianza rappresentano soluzioni efficaci e realizzabili con semplici modulazioni di ampiezza e anche con più avanzate modulazioni di fase e fase-ampiezza.Optical communication systems are suffering from several typical impairments, chromatic dispersion and polarization mode dispersion. Optical compensation of such impairments is possible but it is technological demanding and expensive, whereas electronic signal processing presents many advantages, implementation ease, cost-efficiency, adaptability. Electronic equalization and maximum likelihood sequence detection represent effective and feasible solutions for simple amplitude modulation formats as well as for more advanced phase and phase-amplitude modulation formats
Carrier Synchronization in High Bit-Rate Optical Transmission Systems
In this dissertation, design of optical transmission systems with differential detection and coherent detection is briefly described. More over, algorithms for carrier synchronization and phase estimation with their implementation in high bit-rate optical transmission systems are proposed
Cross-layer energy efficiency of plc systems for smart grid applications
Though opinions are still divided over the specific choices of technology for
smart grid, there is a consensus that heterogeneous communications network
is most appropriate. Power line communication (PLC) is promising because
it is readily available and it aligns with the natural topology of power distribution
network. One of the emerging realities is that the communication
system enabling smart grid must be energy-efficient. This thesis employs a
cross-layer approach to address energy efficiency of PLC networks in different
smart grid scenarios.
At network layer, this work exploits the topology of a PLC-enabled advanced
metering infrastructure (AMI) to improve the probability of successful
packet delivery across the network. The technique, termed AMI clustering,
leverages the traditional structure of the low voltage (LV) network by organising
the smart meters into clusters and locally aggregating their readings.
Improvement in packet delivery inherently reduces energy wastage.
Next, the adaptation layer exploits the low data rate transmission techniques
to reduce the energy requirements of PLC nodes. To achieve that, this
work developed a network model in NS-3 (an open-source network simulator)
that considers PLC transceivers as resource-constrained devices and interconnects
them to emulate home energy management system (HEMS). The model
was validated with experimental results which showed that in the home area
network (HAN), low-rate applications such as energy management can be
supported over low-power PLC networks.
Furthermore, at physical layer, this thesis proposes a more energy-efficient
multi-carrier modulation scheme than the orthogonal frequency division multiplexing
(OFDM) used in most of the current PLC systems. OFDM is widely known for its high peak-to-average-power ratio (PAPR) which degrades energy
efficiency of the systems. This thesis found that by employing vector-
OFDM (V-OFDM), power requirements of PLC transmitter can be reduced.
The results also showed the energy efficiency can be further improved by
using a dynamic noise cancellation technique such as dynamic peak-based
threshold estimation (DPTE) at the receiver.
By applying the proposed methods, packet delivery can be improved by
3% at network layer (which conserves energy) and reduced data rate can save
about 2.6014 dB in transmit power. Finally, at physical layer, V-OFDM and
DPTE can respectively provide 5.8 dB and 2.1 dB reduction in power requirements
of the PLC transceivers. These signify that if V-OFDM is combined
with DPTE, future PLC modems could benefit from energy-efficient power
amplifiers at reduced cost