Applications of perfect difference codes in fiber-optics and wireless optical code-division multiplexing/multiple-access systems

After establishing itself in the radio domain, Spread spectrum code-division multiplexing/multiple-access (CDMA) has seen a recent upsurge in optical domain as well. Due to its fairness, flexibility, service differentiation and increased inherent security, CDMA is proved to be more suitable for the bursty nature of local area networks than synchronous multiplexing techniques like Frequency/Wavelength Division Multiplexing (F/WDM) and Time Division Multiplexing (TDM). In optical domain, CDMA techniques are commonly known as Optical-CDMA (O-CDMA). All optical CDMA systems are plagued with the problem of multiple-access interference (MAI). Spectral amplitude coding (SAC) is one of the techniques used in the literature to deal with the problem of MAI. The choice of spreading code in any CDMA system is another way to ensure the successful recovery of data at the receiving end by minimizing the effect of MAI and it also dictates the hardware design of the encoder and decoder. This thesis focuses on the efficient design of encoding and decoding hardware. Perfect difference codes (PDC) are chosen as spreading sequences due to their good correlation properties. In most of the literature, evaluation of error probability is based on the assumptions of ideal conditions. Such assumptions ignore major physical impairments such as power splitting losses at the multiplexers of transmitters and receivers, and gain losses at the receivers, which may in practice be an overestimate or underestimate of the actual probability of error. This thesis aims to investigate thoroughly with the consideration of practical impairments the applications of PDCs and other spreading sequences in optical communications systems based on spectral-amplitude coding and utilizing codedivision as multiplexing/multiple-access technique. This work begins with a xix general review of optical CDMA systems. An open-ended practical approach has been used to evaluate the actual error probabilities of OCDM/A systems under study. It has been concluded from results that mismatches in the gains of photodetectors, namely avalanche photodiode (APDs), used at the receiver side and uniformity loss in the optical splitters results in the inaccurate calculation of threshold level used to detect the data and can seriously degrade the system bit error rate (BER) performance. This variation in the threshold level can be compensated by employing techniques which maintain a constant interference level so that the decoding architecture does not have to estimate MAI every time to make a data bit decision or by the use of balanced sequences. In this thesis, as a solution to the above problem, a novel encoding and decoding architecture is presented for perfect difference codes based on common zero code technique which maintains a constant interference level at all instants in CDM system and thus relieves the need of estimating interference. The proposed architecture only uses single multiplexer at the transmitters for all users in the system and a simple correlation based receiver for each user. The proposed configuration not only preserves the ability of MAI in Spectral-Amplitude Coding SAC-OCDM system, but also results in a low cost system with reduced complexity. The results show that by using PDCs in such system, the influence of MAI caused by other users can be reduced, and the number of active users can be increased significantly. Also a family of novel spreading sequences are constructed called Manchestercoded Modified Legendre codes (MCMLCs) suitable for SAC based OCDM systems. MCMLCs are designed to be used for both single-rate and Multirate systems. First the construction of MCMLCs is presented and then the bit error rate performance is analyzed. Finally the proposed encoding/decoding architecture utilizing perfect difference codes is applied in wireless infrared environment and the performance is found to be superior to other codes

SYSTEM AND METHOD FOR PERFORMING OPTICAL CODE DIVISION MULTIPLE ACCESS COMMUNICATION USING BPOLAR CODES

An optical encoding and decoding system which performs code-division multiple access (CDMA) communication in the incoherent, or direct detection, optical domain using bipolar +1/-1 codes. The present invention uses code modu lation and detection principles that permit all-optical imple mentation of the bipolar. +1/-1. code and correlation detec tion that have been developed for the radio frequency (RF) systems. This is possible in spite of the non-negative, or unipolar, +1/0, nature of the incoherent optical system that only detects and processes the signal intensity. The unipolar optical system of the present invention is equivalent to the bipolar RF system in that the correlation properties of the bipolar codes is completely preserved. The optical CDMA system can be realized both in time or frequency domain encoding with all-optical components

Study of spread spectrum multiple access systems for satellite communications with overlay on current services

The feasibility of using spread spectrum techniques to provide a low-cost multiple access system for a very large number of low data terminals was investigated. Two applications of spread spectrum technology to very small aperture terminal (VSAT) satellite communication networks are presented. Two spread spectrum multiple access systems which use a form of noncoherent M-ary FSK (MFSK) as the primary modulation are described and the throughput analyzed. The analysis considers such factors as satellite power constraints and adjacent satellite interference. Also considered is the effect of on-board processing on the multiple access efficiency and the feasibility of overlaying low data rate spread spectrum signals on existing satellite traffic as a form of frequency reuse is investigated. The use of chirp is examined for spread spectrum communications. In a chirp communication system, each data bit is converted into one or more up or down sweeps of frequency, which spread the RF energy across a broad range of frequencies. Several different forms of chirp communication systems are considered, and a multiple-chirp coded system is proposed for overlay service. The mutual interference problem is examined in detail and a performance analysis undertaken for the case of a chirp data channel overlaid on a video channel

Dark signalling and code division multiple access in an optical fibre LAN with a bus topology

This thesis describes an optical fibre network that uses a bus topology and Code Division Multiple Access (CDMA). Various potential configurations are analysed and compared and it is shown that a serious limitation of optical CDMA schemes using incoherent correlators is the effect of optical beating due to the presence of multiple incoherent optical signals at the receiver photodiode. The network proposed and analysed in this thesis avoids beating between multiple optical fields because it only uses a single, shared, optical source. It does this through the SLIM (Single Light-source with In-line Modulation) configuration in which there is a continuously-operating light source at the head-end of a folded bus, and modulators at the nodes to impose signals on the optical field in the form of pulses of darkness which propagate along the otherwise continuously bright bus. Optical CDMA can use optical-fibre delay-line correlators as matched filters, and these may be operated either coherently or incoherently.Coherent operation is significantly more complex than incoherent operation, but incoherent correlators introduce further beating even in a SLIM network. A new design of optical delay-line correlator, the hybrid correlator, is therefore proposed, analysed and demonstrated. It is shown to eliminate beating. A model of a complete network predicts that a SLIMbus using optical CDMA with hybrid correlators can be operated at TeraBaud rates with the number of simultaneous users limited by multiple access interference (MAI), determined only by the combinatorics of the code set

[[alternative]]Design of Robust System and Smart Network for Broadband Optical Metro and Access Networks(I)

計畫編號：NSC94-2213-E032-005研究期間：200508~200607研究經費：660,000[[abstract]]Part A: 提出一寬頻光都會與接取網路之強健系統設計，利用強健控制器來使雷射波長更穩定縮短穩定時間且 利用參數最佳化設計來調整網路效能(包括溫度變化與元件的老化等)，也針對所用的強健控制系統作 硬體的實現來驗證我們所設計的控制器。 (1) 強健控制器設計 (2) 波長穩定控制器之分析與設計 (3) 網路元件之強健動態控制系統分析 (4) 強健控制器最佳化設計 (5) 波長穩定控制器之最佳化分析與設計 (6) 網路元件之強健動態控制系統設計 (7) 強健控制器硬體設計 (8) 波長穩定控制器之實際參數分析與設計 (9) 網路元件之強健動態控制最佳化 Part B: 提出由基因演算法來對每個網路元件作動態控制器設計，針對光接取網路提出基因演算法加速裝置將 網路作最佳化的調整使網路效能達最佳化。另一方面，我們也對寬頻光都會與接取網路之智慧網路設 計增加網路的效能。 (1) 基因演算法之最佳化控制設計 (2) 基因演算法加速裝置之光接取網路設計 (3) 智慧網路之光接取網路設計 (4) 基因演算法之動態控制設計 (5) 管線型基因演算法加速裝置之光接取網路設計 (6) 智慧網路之光接取網路設計 (7) 基因演算法之光接取網路動態控制設計 (8) 管線型基因演算法加速裝置硬體設計 (9) 智慧網路之光接取網路最佳化設計 Part C: 將強健系統與智慧網路套用至PON(Passive Optical Network) 的系統中來驗證， 包括針對 WDM-PON(Wavelength Division Multiplexing-PON) 與CDMA-PON (Code Division Multiple Access-PON)的最佳化設計，另一方面也針對WDM-PON與CDMA-PON的MAC(Media Access Control) 做規劃與設計(包括封包的設計等)，利用GA 來做波長分配與碼分配的最佳化且用於MAN(Metro Aera Network)，最後加入平型式之錯誤更正碼來增加與改善網路系統的效能。 (1) PON 智慧網路設計 (2) WDM-PON 與CDMA-PON 之智慧網路設計 (3) 平行架構之錯誤更正碼探討 (4) PON 智慧網路最佳化設計 (5) WDM-PON 與CDMA-PON 之網路協定設計 (6) 平行架構錯誤更正碼之硬體設計 (7) PON 智慧網路之控制器與基因演算法之實現 (8) WDM-PON 與CDMA-PON 網路最佳化設計 (9) 利用GA 來做波長與碼的分配最佳化 (10) 在MAN 中網路與WDM-PON/CDMA-PON 溝通之探討 (11) 智慧型網路結合平行架構之錯誤更正碼之分析[[sponsorship]]行政院國家科學委員

On architecture and scalability of optical multi-protocol label switching networks using optical-orthogonal-code label.

Wen Yonggang.Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.Includes bibliographical references.Abstracts in English and Chinese.Chapter 1 --- IntroductionChapter 1.1 --- Multi-Protocol Label Switching (MPLS) Technology --- p.1Chapter 1.2 --- Objective of this Thesis --- p.4Chapter 1.3 --- Reference --- p.5Chapter 2 --- Optical MPLS Network and Optical Label SchemesChapter 2.1 --- Optical MPLS Network --- p.7Chapter 2.2 --- Optical Label Schemes --- p.10Chapter 2.2.1 --- Time-division OMPLS scheme --- p.12Chapter 2.2.2 --- Wavelength-division OMPLS scheme --- p.16Chapter 2.2.3 --- Frequency-division OMPLS scheme --- p.22Chapter 2.2.3.1 --- UCSB Testbed --- p.23Chapter 2.2.3.2 --- UC-Davis Testbed --- p.26Chapter 2.2.3.3 --- NCTU-Telecordia Testbed --- p.28Chapter 2.2.4 --- Code-division OMPLS scheme --- p.30Chapter 2.2.4.1 --- Coherent Code-Division Label Scheme --- p.30Chapter 2.2.4.2 --- Noncoherent Code-Division Label Scheme --- p.32Chapter 2.3 --- Reference --- p.35Chapter 3 --- Architecture of OOC-based OMPLS networkChapter 3.1 --- Infrastructure of OOC-label switch router (code converter) --- p.37Chapter 3.1.1 --- Architecture of the Proposed Code Converter --- p.38Chapter 3.1.2 --- Enhancement of the Code Converter --- p.41Chapter 3.2 --- Implementation of the OOC code converter --- p.43Chapter 3.2.1 --- Encoders/Decoders --- p.43Chapter 3.2.1.1 --- All-parallel encoders/decoders --- p.43Chapter 3.2.1.2 --- All-serial encoders/decoders --- p.45Chapter 3.2.1.3 --- Serial-to-parallel encoder/decoders --- p.47Chapter 3.2.1.4 --- Comparison of the three kinds of encoders/decoders --- p.49Chapter 3.2.2 --- Time-Gate-Intensity-Threshold (TGIT) Device --- p.50Chapter 3.2.3 --- Optical Space Switch Array --- p.54Chapter 3.2.3.1 --- All-optical Space Switch --- p.54Chapter 3.2.3.2 --- Optical switching technologies --- p.56Chapter 3.2.3.2.1 --- Scalability --- p.56Chapter 3.2.3.2.2 --- Switching Speed --- p.57Chapter 3.2.3.2.3 --- Reliability --- p.57Chapter 3.2.3.2.4 --- Losses --- p.58Chapter 3.2.3.2.5 --- Port-to-Port repeatability --- p.58Chapter 3.2.3.2.6 --- Cost --- p.59Chapter 3.2.3.2.7 --- Power Consumption --- p.60Chapter 3.3 --- Reference --- p.61Chapter 4 --- Scalability of OOC-based MPLS networkChapter 4.1 --- Limitation on Label Switching Capacity --- p.63Chapter 4.1.1 --- Upper Bound --- p.65Chapter 4.1.2 --- Lower Bound --- p.66Chapter 4.2 --- Limitation on Switching Cascadability --- p.70Chapter 4.2.1. --- Limit Induced by the Inter-channel Crosstalk --- p.70Chapter 4.2.2 --- Limits Induced by the Residue Intensity of Sidelobes --- p.74Chapter 4.3 --- Appendix --- p.78Chapter 4.3.1 --- Derivation of Chip Intensity --- p.78Chapter 4.3.2 --- The 5% residue power criterion --- p.81Chapter 4.4 --- Reference --- p.83Chapter 5 --- ConclusionChapter 5.1 --- Summary of the Thesis --- p.85Chapter 5.2 --- Future work --- p.8

Ultra Wideband

Ultra wideband (UWB) has advanced and merged as a technology, and many more people are aware of the potential for this exciting technology. The current UWB field is changing rapidly with new techniques and ideas where several issues are involved in developing the systems. Among UWB system design, the UWB RF transceiver and UWB antenna are the key components. Recently, a considerable amount of researches has been devoted to the development of the UWB RF transceiver and antenna for its enabling high data transmission rates and low power consumption. Our book attempts to present current and emerging trends in-research and development of UWB systems as well as future expectations

Millimeter-wave Communication and Radar Sensing — Opportunities, Challenges, and Solutions

With the development of communication and radar sensing technology, people are able to seek for a more convenient life and better experiences. The fifth generation (5G) mobile network provides high speed communication and internet services with a data rate up to several gigabit per second (Gbps). In addition, 5G offers great opportunities of emerging applications, for example, manufacture automation with the help of precise wireless sensing. For future communication and sensing systems, increasing capacity and accuracy is desired, which can be realized at millimeter-wave spectrum from 30 GHz to 300 GHz with several tens of GHz available bandwidth. Wavelength reduces at higher frequency, this implies more compact transceivers and antennas, and high sensing accuracy and imaging resolution. Challenges arise with these application opportunities when it comes to realizing prototype or demonstrators in practice. This thesis proposes some of the solutions addressing such challenges in a laboratory environment.High data rate millimeter-wave transmission experiments have been demonstrated with the help of advanced instrumentations. These demonstrations show the potential of transceiver chipsets. On the other hand, the real-time communication demonstrations are limited to either low modulation order signals or low symbol rate transmissions. The reason for that is the lack of commercially available high-speed analog-to-digital converters (ADCs); therefore, conventional digital synchronization methods are difficult to implement in real-time systems at very high data rates. In this thesis, two synchronous baseband receivers are proposed with carrier recovery subsystems which only require low-speed ADCs [A][B].Besides synchronization, high-frequency signal generation is also a challenge in millimeter-wave communications. The frequency divider is a critical component of a millimeter-wave frequency synthesizer. Having both wide locking range and high working frequencies is a challenge. In this thesis, a tunable delay gated ring oscillator topology is proposed for dual-mode operation and bandwidth extension [C]. Millimeter-wave radar offers advantages for high accuracy sensing. Traditional millimeter-wave radar with frequency-modulated continuous-wave (FMCW), or continuous-wave (CW), all have their disadvantages. Typically, the FMCW radar cannot share the spectrum with other FMCW radars.\ua0 With limited bandwidth, the number of FMCW radars that could coexist in the same area is limited. CW radars have a limited ambiguous distance of a wavelength. In this thesis, a phase-modulated radar with micrometer accuracy is presented [D]. It is applicable in a multi-radar scenario without occupying more bandwidth, and its ambiguous distance is also much larger than the CW radar. Orthogonal frequency-division multiplexing (OFDM) radar has similar properties. However, its traditional fast calculation method, fast Fourier transform (FFT), limits its measurement accuracy. In this thesis, an accuracy enhancement technique is introduced to increase the measurement accuracy up to the micrometer level [E]

Fiber-optic code division multiple access : multi-class optical orthogonal codes, optical power control, and polarization encoding

Ever since the mid- 1980s when the single-mode fiber-optic media were believed to become the main highways of future telecommunications networks for transporting high-volume high-quality multipurpose information, the need for all-optical multi-access networking became important. An all-optical multi-access network is a collection of multiple nodes where the interconnection among various nodes is via single- or multi-mode fiber optics and for which they perform all their essential signal processing requirements such as switching, add-drop, multiplexing/demultiplexing and amplification in the optical domain. Optical CDMA networking is one possible technique that allows multiple users in local area networks to access the same fiber channel asynchronously with no delay or scheduling. Optical CDMA networks are not without their own problems. Search for codes suitable to the optical domain is one of the important topics addressed in the literature on optical CDMA. Existing codes developed in the late 80's are limited to single class traffic or can support multiclass traffic but with restrictions on code lengths and weights. Also the number of generated codes is severely limited due to orthogonality issues. In this thesis, we pay particular attention to propose new codes that can support multiclass traffic with arbitrary code weights and lengths. Therefore, data sources with varying traffic demands can be accommodated by optical CDMA networks using the proposed codes. We also present a simple generation technique for the proposed multiclass codes and analyze their performance. The number of users supported by the proposed multiclass codes will be limited since it is an extension of existing code designs with such limitation. We then propose the use of polarization dimension in order to double the number of supported users. On the other hand, incoherent optical CDMA systems are considered as positive systems meaning that only unipolar codes can be considered for such systems. Therefore, multiple access interference will be quite high in optical CDMA due to the nature of incoherent power detection. Reducing the effect of the interference on the performance of optical CDMA is an important topic. We propose the use of power control to decrease the effects of interference in optical star networks in which users' fiber lengths and data rates are not equal. We consider the case of optically amplified network with amplifier noise as the main source. We then elaborate by considering the nonlinearity in the photodetection process and propose the use of an iterative algorithm to find the solution of the non-linear optical power control problem. Finally, we propose an optical CDMA system based on polarization encoding. Since the encoding is performed in the spatial domain, therefore, positive and negative levels can be realized. This approach leads to increasing the number of supported users of optical CDMA by the use of known codes, such as Gold and Hadamard codes, with enhanced performance.reviewe