Topology-Transparent Scheduling in Mobile Ad Hoc Networks Supporting Heterogeneous Quality of Service Guarantees

Transmission scheduling plays a critical role in mobile ad hoc networks. Many transmission scheduling algorithms have been proposed to maximize the spatial reuse and minimize the time-division multiple-access (TDMA) frame length. Most algorithms require information on the network topology and cannot adapt to the dynamic topology in mobile scenarios. To overcome this limitation, topology-transparent scheduling algorithms have been proposed. Most of them, based on Galois field theory, Latin square, and block design theory, assign time slots to users and guarantee that there is at least one collision-free slot in each frame for each user. To the best of our knowledge, none of these topology-transparent algorithms support multiple quality of service (QoS) requirements. In this paper, we exploit the variable-weight optical orthogonal codes (VW-OOC) to design a topology-transparent scheduling algorithm in wireless ad hoc networks with multiple QoS levels. We study the performance, in terms of minimum guaranteed throughput and average throughput, of our proposed algorithm analytically and by extensive simulations.published_or_final_versio

Development of User-Interface Software Program for Double Weight Code Family for OCDMA

Optical Code Division Multiple Access (OCDMA) offers high statistical multiplexing gain in a busty traffic environment and is thought to be a more suitable solution in local-area network. There have been many codes proposed OCDMA systems, such as Hadamard code, Modified Frequency Hopping (MFH) code and Double Weight (DW) code family. The inspiration of this study is to improve the Modified Double Weight (MDW) code to give a better performance and to enhance the detection technique of DW code family. There are few aspects that have been identified in this study. First of all, the construction of MDW code is studied. Besides, the equation-based construction technique is examined and is then simulated using Virtual Basic software version 6.0. The findings of the project will lead to a new development of the MDW code by having new user-interface software program to generate the DW codeword with an ease

Throughput Performance Evaluation of Multiservice Multirate OCDMA in Flexible Networks

\u3cp\u3eIn this paper, new analytical formalisms to evaluate the packet throughput of multiservice multirate slotted ALOHA optical code-division multiple-access (OCDMA) networks are proposed. The proposed formalisms can be successfully applied to 1-D and 2-D OCDMA networks with any number of user classes in the system. The bit error rate (BER) and packet correct probability expressions are derived, considering the multiple-access interference as binomially distributed. Packet throughput expressions, on the other hand, are derived considering Poisson, binomial, and Markov chain approaches for the composite packet arrivals distributions, with the latter defined as benchmark. A throughput performance evaluation is carried out for two distinct user code sequences separately, namely, 1-D and 2-D multiweight multilength optical orthogonal code (MWML-OOC). Numerical results show that the Poisson approach underestimates the throughput performance in unacceptable levels and incorrectly predicts the number of successfully received packets for most offered load values even in favorable conditions, such as for the 2-D MWML-OOC OCDMA network with a considerably large number of simultaneous users. On the other hand, the binomial approach proved to be more straightforward, computationally more efficient, and just as accurate as the Markov chain approach.\u3c/p\u3

Development of Zero Cross Correlation-Double Weight Code for Optical CDMA

Optical fibers are very attractive communication media if compared to the conventional guided media like twisted wire pairs and coaxial cables since they offer large bandwidth and low attenuation. Hence, by utilizing optical fibers as the media of communication links, more advantages can be obtained if compared to traditional media. The three major multiple access for optical networks are Time Division Multiple Accees (TDMA), Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CDMA). OCDMA has advantages over TDMA and FDMA because first of all it makes efficient use of communication media by allowing asynchronous access to each user. Second no scheduling is required in CDMA and new users can easily be added to the networks. The Optical Code Division Multiple Access (OCDMA) suffers from various types of noise but the dominant source of noise is Multiple Access Interference (MAl). Therefore, the cancellation or suppression of MAl is a big problem in OCDMA. Much OCDMA codes have been designed to reduce the MAl and to enhance the performance of the system. This thesis concentrates on how to reduce the MAl in OCDMA. In this thesis Zero Cross Correlation-Double Weight Code (ZCC-DW) is proposed based on Modified Double Weight Code (MDW) for OCDMA system to decrease the cross correlation value from one to zero hence the Multiple Access Interference (MAl) should be decrease and this will improve the system performance. After completion the code construction techniques a simulation is used to study the performance of ZCC-DW code. The performance is carried out to various data rate and various optical fiber lengths to calculate the Bit Error Rate (BER) which it used to evaluate the code performance. Lastly Comparisons are then made between Direct Detection (ZCC-DW code Detection) and Hybrid Detection (MDW code Detection). Direct Detection Technique offers better result than Hybrid Detection Technique

Security enhancement in passive optical networks through wavelength hopping and sequences cycling technique

Growth in the telecommunication industry continues to expand with requirements evolving around increased bandwidth and security. Advances in networking technologies have introduced low cost optical components that has made passive optical networks (PON) the choice for providing huge bandwidth to end users. PON are covered by established standards such as IEEE 802.3ah and ITU-T G.983.1/984.1, with star topology of broadcast and select (B&S) on shared fiber links that poses security vulnerability in terms of confidentiality and privacy;Research and reports in the literature focus around increasing cardinality via coding schemes that lack in addressing security, which was left for implementation in application layers via cryptography. This dissertation presents an approach on security in PON at the network level using slow wavelength hopping techniques and diffusion of data packets among dense wave division multiplex (DWDM). Orthogonal wavelength sequences are generated by mapping an ITU-T G694.1 based wavelength grid matrix and code matrices. The arrangement of wavelengths in the wavelength grid matrix, which can be changed frequently (i.e, hourly) serves as the first key of secure operation. Allocation of generated wavelength sequences distributed in multiple quantities to nodes based on their security level serve as second individual keys for the nodes. In addition, an improved level of security provided via the cycling order of those allocated wavelength sequences to nodes is the third key between the central office (CO) and a node. The proposed approach to PON security provides three new keys available outside the world of cryptography;Various coding techniques are used, and results show that even time spreading/wavelength hopping based on symmetric prime numbers provided the least wavelength sequences; however, it provided excellent correlation properties and level of security. A PON simulation model was implemented to investigate channel impairments in DWDM with 64 channels spaced at 25GHz carried over a 25 km ITU-T G.655 compliant shared fiber cable. Security performance evaluation included analytical studies in classical probabilities to capture the correct order of wavelength hopping sequence using exhaustive searching and reverse construction of matrices from monitored channels. Encouraging results obtained support the feasibility of this proposed technical approach for security

Study on Flexible Optical Code Label Generation and Processing by High-speed/Spatial Light Modulators

制度:新 ; 報告番号:甲3560号 ; 学位の種類:博士(工学) ; 授与年月日:2012/3/15 ; 早大学位記番号:新589

New Optical Orthogonal Codes By Using Diophantine Equations [construção De Novos Códigos Ortogonais ópticos Por Meio De Equações Diofantinas]

Two families of optical orthogonal codes (OOC's) are algebraically designed by using the parametric binary quartic and quadratic forms. The first family of codes has ideal auto and cross-correlation properties and the second family has nonideal cross-correlation properties. The performance of these codes is presented as function of the number of simultaneous OCDMA system users. We present examples of the constructed codes for illustration purposes. The algebraic OOC's being proposed in this paper find applications in asynchronous optical code division multiple access (OCDMA) systems.33225232Chung, F., Salehi, J.A., Wei, V.K., Optical orthogonal codes: Design, analysis and applications (1989) IEEE Trans. Inform. Theory, 35 (3), pp. 595-604. , MarSalehi, J.A., Code division multiple access techniques in optical fiber networks - Part I: Fundamental principles (1989) IEEE Trans. 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