Robustness of bus overlays in optical networks

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (p. 53-56).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Local area networks (LANs) nowadays use optical fiber as the medium of communication. This fiber is used to connect a collection of electro-optic nodes which form network clouds. A network cloud is a distribution network that connects several external nodes to the backbone, and often takes the form of a star or tree. Optical stars and trees have expensive and inefficient recovery schemes, and as a result, are not attractive options when designing networks. In order to solve this problem, we introduce a virtual topology that makes use of the robustness that is inherently present in a metropolitan area network (MAN) or wide area network (WAN) (long haul network). The virtual topology uses a folded bus scheme and includes some of the elements of the real topology (architecture). By optically bypassing some of the router/switch nodes in the physical architecture, the virtual topology yields better recovery performance and more efficient systems (with respect to cost related to bandwidth and recoverability). We present a bus overlay which uses simple access nodes and is robust to single failures. Our architecture allows the use of existing optical backbone infrastructure. We consider a linear folded bus architecture and introduce a T-shaped folded bus. Although buses are generally not able to recover from failures, we propose a loopback approach. Our approach allows optical bypass of some routers during normal operation, thus reducing the load on routers, but makes use of routers in case of failures. We analyze the behavior of our linear and T-shaped systems under average use and failure conditions. We show that certain simple characteristics of the traffic matrix give meaningful performance characterization. We show that our architecture provides solutions which limit loads on the router.by Ari Levon Libarikian.S.M

Implementation of a high-speed optical network and spectrum analysis of a multichannel CATV system.

by Chun-kit Chan.Thesis (M.Phil.)--Chinese University of Hong Kong, 1995.Includes bibliographical references (leaves 68-[73]).Chapter 1 --- A High-Speed All-Optical Tunable-Channel Multi-Access (TCMA) Network --- p.1Chapter 1.1 --- Introduction --- p.1Chapter 1.2 --- Tunable-Channel Multi-Access (TCMA) Networks --- p.4Chapter 1.3 --- Protocols For TCMA Networks --- p.5Chapter 1.3.1 --- Media Access Procedure For ACTA Protocol --- p.6Chapter 1.3.2 --- Cyclc Utilization & Adaptive Algorithm --- p.8Chapter 1.3.3 --- Advantages of ACTA Protocol --- p.9Chapter 1.4 --- Proposed High-Speed Photonic TDM Implementation --- p.10Chapter 1.4.1 --- Centralized Pulse Source --- p.12Chapter 1.4.2 --- Channel-Tunable Transmitter --- p.14Chapter 1.4.3 --- High Speed All-Optical Demultiplexing --- p.22Chapter 1.4.4 --- Timing and Synchronization --- p.23Chapter 1.4.5 --- Advantages of the Proposed Scheme --- p.24Chapter 1.5 --- Other Network Issues --- p.25Chapter 1.5.1 --- Scalability --- p.25Chapter 1.5.2 --- Surviability --- p.26Chapter 1.5.3 --- Cost-Effectiveness --- p.27Chapter 1.6 --- Conclusion --- p.28Chapter 2 --- Theoretical Analysis of High Repetition Rate Optical Pulse Multiplication using Fiber Coupler Loop Configuration --- p.29Chapter 2.1 --- Introduction --- p.29Chapter 2.2 --- Single Coupler Loop Configuration --- p.30Chapter 2.3 --- Cascaded Coupler Loop Configuration --- p.34Chapter 2.4 --- Discussion --- p.36Chapter 2.5 --- Conclusion --- p.38Chapter 3 --- Spectrum Analysis of Multichannel CATV Systems --- p.39Chapter 3.1 --- Introduction --- p.39Chapter 3.2 --- Considerations of Analysis of Multichannel CATV Systems --- p.41Chapter 3.3 --- Effects of Incomplete-cycle Sampling --- p.43Chapter 3.4 --- Methods to Alleviate the Incomplete-cycle Sampling Effcct --- p.48Chapter 3.4.1 --- Windowing --- p.48Chapter 3.4.2 --- Correction --- p.54Chapter 3.5 --- Nonlinear Distortion in Multichannel CATV Systems --- p.55Chapter 3.5.1 --- Two-tone Third Order Distortion Estimation --- p.56Chapter 3.5.2 --- Composite Triple Beat Estimation --- p.62Chapter 3.6 --- A Procedure of Spectrum Analysis for Multichannel CATV Systems --- p.64Chapter 3.7 --- Conclusion --- p.67Bibliography --- p.68Chapter A --- Implementation of a high-speed TCMA optical network --- p.74Chapter A.1 --- System Setup --- p.74Chapter A.2 --- Channel-tunable Delay Line Circuit --- p.75Chapter A.3 --- DFB Laser diode --- p.76Chapter A.4 --- Erbium-doped Fiber Amplifier (EDFA) --- p.76Chapter A.5 --- 1 Gb/s to 16 Gb/s Fiber Multiplexer --- p.77Chapter A.6 --- Nonlinear Amplifying Loop Mirror (NALM) --- p.77Chapter A.7 --- Decision Circuit --- p.78Chapter B --- Frequency Assignment Scheme of CATV Systems --- p.79Chapter C --- Derivation --- p.80Chapter C.1 --- Channel Carrier Power Level Variation with Rectangular Window --- p.81Chapter C.2 --- Channel Carrier Power Level With Hanning Window Function ´Ø --- p.82Chapter C.3 --- Correction Factor for the Channel Carriers --- p.83Chapter C.4 --- Correction Scheme for Distortion Terms --- p.8

Channel-tunable mode-locked laser transmitter for OTDM networks and modeling of mode-locked semiconductor laser.

by Hung Wai.Thesis (M.Phil.)--Chinese University of Hong Kong, 2000.Includes bibliographical references (leaves 69-[73]).Abstracts in English and Chinese.Chapter 1 --- Introduction --- p.1Chapter 1.1 --- All Optical Multi-Access Network --- p.1Chapter 1.2 --- Multi-access Techniques --- p.2Chapter 1.2.1 --- Wavelength-Division Multi-access (WDMA) --- p.2Chapter 1.2.2 --- Subcarrier Multi-Access (SCMA) --- p.3Chapter 1.2.3 --- Time-Division Multi-Access(TDMA) --- p.3Chapter 1.3 --- Numerical Modelling of Semiconductor Mode-locked laser --- p.4Chapter 1.4 --- Objective of this Thesis --- p.5Chapter 2 --- Optical TDMA networks --- p.7Chapter 2.1 --- Introduction --- p.7Chapter 2.2 --- OTDM --- p.8Chapter 2.3 --- Network Architecture --- p.9Chapter 2.3.1 --- Broadcast Networks --- p.9Chapter 2.3.2 --- Switch-based networks --- p.10Chapter 2.4 --- Key technologies for optical TDMA Network --- p.13Chapter 2.4.1 --- High Repetition Rate Short Pulse sources --- p.13Chapter 2.4.2 --- Multiplexer and de-multiplexers --- p.15Chapter 2.4.3 --- Optical Clock Recovery --- p.17Chapter 2.4.4 --- All optical logic gates --- p.18Chapter 2.5 --- Summary --- p.19Chapter 3 --- A Channel-Tunable Mode-locked Laser Transmitter for OTDM Networks --- p.20Chapter 3.1 --- Introduction --- p.20Chapter 3.2 --- Principle of Operation --- p.21Chapter 3.3 --- Experimental Demonstration --- p.23Chapter 3.4 --- The Channel Tuning Transient --- p.25Chapter 3.5 --- Experimental Investigation of channel-tuning transient --- p.28Chapter 3.6 --- Summary --- p.37Chapter 4 --- Modeling of Mode-Locked Semiconductor Laser --- p.38Chapter 4.1 --- Introduction --- p.38Chapter 4.2 --- Principle of Mode-Locking --- p.39Chapter 4.3 --- Simulation Model --- p.41Chapter 4.3.1 --- Travelling Wave Rate Equation Analysis --- p.41Chapter 4.3.2 --- Large Signal Time Domain Mode-locked Laser Model --- p.42Chapter 4.3.3 --- Modeling of Spontaneous Noise --- p.44Chapter 4.3.4 --- Modeling of Self-phase Modulation --- p.44Chapter 4.3.5 --- Frequency Dependent Gain Profile --- p.45Chapter 4.3.6 --- Computation Procedure --- p.45Chapter 4.4 --- Device Parameters --- p.47Chapter 4.5 --- Simulation Results on Passive Mode-locking --- p.48Chapter 4.5.1 --- Pulse Repetition Rate under Passive Mode-locking --- p.48Chapter 4.5.2 --- The effect of Differential Gain and Differential Absorption on Mode-locking Regimes --- p.50Chapter 4.5.3 --- The Effects of Linewidth Enhancement Factor and Ab- sorber Carrier Lifetime on Mode-locking Pulse Width --- p.53Chapter 4.6 --- Simulation Results on Hybrid and Subharmonic Mode-locking --- p.54Chapter 4.6.1 --- Modeling the Effect of Modulation on Absorber Section --- p.54Chapter 4.6.2 --- Modulation Phase Change Dynamics --- p.55Chapter 4.6.3 --- Subharmonc Mode-Locking Induced Amplitude Modulation --- p.62Chapter 4.7 --- Summary --- p.64Chapter 5 --- Conclusion --- p.66Chapter 5.1 --- Summary of the Thesis --- p.66Chapter 5.2 --- Future Work --- p.67Bibliography --- p.6

Scheduling Non-Uniform Traffic: A Preliminary Report

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryNational Science Foundation / NSF NCR 90-0435

Dynamic bandwidth allocation in CDMA-based passive optical networks

Fiber to the home (FTTH) technology is an attractive solution for providing high bandwidth from the Central Office (CO) to residences and small-and medium-sized businesses. The emergence of Internet Protocol-based communication within households such as VoIP, IPTV, video conferencing, and high definition multimedia shows that there is a need for high-capacity networks that can handle differentiated services. By providing an optical fiber link to a household where the optical network unit (ONU) is located, there will be a tremendous increase in information capacity with respect to Digital Subscriber Line and cable modem technologies that are currently in place. In access networks, Passive Optical Networks (PON) are rapidly replacing copper-based technologies due to a wide range of benefits, one of which is having the capability to transmit data at a higher rate and reach further distances without signal degradation. Under the PON family of technologies, Ethernet PON (EPON) was developed and is specified in the IEEE 802.3 standard outlining the framework that can deliver voice, data, and video over a native Ethernet port to businesses and residential customers. An increasingly important subject to network operators is Quality of Service (QoS). Although the EPON specification provides mechanisms for supporting QoS, it does not specify or define an algorithm for providing QoS. Rather it is up to the CO to design and implement an appropriate algorithm to meet the specifications of services that are offered to their clients. Researchers have extensively studied bandwidth allocation in EPON where the challenge is to develop bandwidth allocation algorithms that can fairly redistribute bandwidth among ONUs based on their demand. These algorithms were developed for the uplink direction, from ONUs to CO, in a network where only a single ONU is permitted to transmit at a time. Another well-established PON technology is Optical Code-Division Multiple Access PON (OCDMA-PON). In recent years, it has become more economical due to hardware advancements and it has gained a lot of attention due to its benefits over EPON. The most attractive benefit of OCDMA-PON is that multiple ONUs may transmit to the CO simultaneously, depending on a number of constraints, whereas EPON is limited to a single ONU transmission at a time. In this thesis, we develop a dynamic bandwidth allocation algorithm called Multi-Class Credit-Based Packet Scheduler (MCBPS) for OCDMA-PON in the uplink direction that supports the Internet Protocol (IP) Differentiated Services and takes advantage of the simultaneous nature of OCDMA. The IP Differentiated Services specifications stipulate the following traffic classifications: Expedited Forwarding for low latency, low packet loss, and low jitter applications; Assured Forwarding for services that require low packet loss; and Best Effort which are not guaranteed any bandwidth commitments. MCBPS incorporates the use of credit pools and the concept of a credit bank system to provide the same services as EPON by assigning ONUs specific timeslots to transmit data and also by specifying the amount of bytes from each class. MCBPS is a central office based algorithm that provides global fairness between Quality of Service (QoS) classes while also ensuring that at any given moment the desired number of simultaneous transmissions is not exceeded. We demonstrate through simulation that MCBPS algorithm is applicable in both EPON and OCDMA-PON environments. An in-house simulation program written in the C programming language is used to evaluate the effectiveness of the proposed algorithm. The MCBPS algorithm was tested alongside a benchmark algorithm called Interleaved Polling with Adaptive Cycle Time (IPACT) algorithm to compare network throughput, average packet delay, maximum packet delay, and packet loss ratio. From the simulation results it was observed that MCBPS algorithm is able to satisfy the QoS requirements and its performance is comparable to IPACT where the simultaneous transmission is limited to one. The simulation results also show that as the number of simultaneous transmissions within the network increases, so does the bandwidth. The MCBPS algorithm is able to re-distribute the scaling bandwidth while ensuring that a single ONU or QoS class does not monopolize all the available bandwidth. In doing so, through simulation results, as the simultaneous transmissions increases, the average packet delay decreases and the packet loss ratio improves

Time diversity solutions to cope with lost packets

A dissertation submitted to Departamento de Engenharia Electrotécnica of Faculdade de Ciências e Tecnologia of Universidade Nova de Lisboa in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engenharia Electrotécnica e de ComputadoresModern broadband wireless systems require high throughputs and can also have very high Quality-of-Service (QoS) requirements, namely small error rates and short delays. A high spectral efficiency is needed to meet these requirements. Lost packets, either due to errors or collisions, are usually discarded and need to be retransmitted, leading to performance degradation. An alternative to simple retransmission that can improve both power and spectral efficiency is to combine the signals associated to different transmission attempts. This thesis analyses two time diversity approaches to cope with lost packets that are relatively similar at physical layer but handle different packet loss causes. The first is a lowcomplexity Diversity-Combining (DC) Automatic Repeat reQuest (ARQ) scheme employed in a Time Division Multiple Access (TDMA) architecture, adapted for channels dedicated to a single user. The second is a Network-assisted Diversity Multiple Access (NDMA) scheme, which is a multi-packet detection approach able to separate multiple mobile terminals transmitting simultaneously in one slot using temporal diversity. This thesis combines these techniques with Single Carrier with Frequency Division Equalizer (SC-FDE) systems, which are widely recognized as the best candidates for the uplink of future broadband wireless systems. It proposes a new NDMA scheme capable of handling more Mobile Terminals (MTs) than the user separation capacity of the receiver. This thesis also proposes a set of analytical tools that can be used to analyse and optimize the use of these two systems. These tools are then employed to compare both approaches in terms of error rate, throughput and delay performances, and taking the implementation complexity into consideration. Finally, it is shown that both approaches represent viable solutions for future broadband wireless communications complementing each other.Fundação para a Ciência e Tecnologia - PhD grant(SFRH/BD/41515/2007); CTS multi-annual funding project PEst-OE/EEI/UI0066/2011, IT pluri-annual funding project PEst-OE/EEI/LA0008/2011, U-BOAT project PTDC/EEATEL/ 67066/2006, MPSat project PTDC/EEA-TEL/099074/2008 and OPPORTUNISTICCR project PTDC/EEA-TEL/115981/200

Multilevel Parallel Communications

The research reported in this thesis investigates the use of parallelism at multiple levels to realize high-speed networks that offer advantages in throughput, cost, reliability, and flexibility over alternative approaches. This research specifically considers use of parallelism at two levels: the upper level and the lower level. At the upper level, N protocol processors perform functions included in the transport and network layers. At the lower level, M channels provide data and physical layer functions. The resulting system provides very high bandwidth to an application. A key concept of this research is the use of replicated channels to provide a single, high bandwidth channel to a single application. The parallelism provided by the network is transparent to communicating applications, thus differentiating this strategy from schemes that provide a collection of disjoint channels between applications on different nodes. Another innovative aspect of this research is that parallelism is exploited at multiple layers of the network to provide high throughput not only at the physical layer, but also at upper protocol layers. Schedulers are used to distribute data from a single stream to multiple channels and to merge data from multiple channels to reconstruct a single coherent stream. High throughput is possible by providing the combined bandwidth of multiple channels to a single source and destination through use of parallelism at multiple protocol layers. This strategy is cost effective since systems can be built using standard technologies that benefit from the economies of a broad applications base. The exotic and revolutionary components needed in non-parallel approaches to build high speed networks are not required. The replicated channels can be used to achieve high reliability as well. Multilevel parallelism is flexible since the degree of parallelism provided at any level can be matched to protocol processing demands and application requirements