Biblio

Optical Code Division Multiple Access (OCDMA) is an inevitable innovation to cope up with the impediments of regularly expanding information traffic and numerous user accesses in optical systems. In Spectral Amplitude Coding (SAC)-OCDMA systems cross correlation and Multiple Access Interference (MAI) are utmost concerns. For eliminating the cross correlation, reducing the MAI and to enhance the security, in this work, all optical Diagonal Identity Matrices codes (DIM) with Zero Cross-Correlation (ZCC) and optical gating are presented. Chip rate of the proposed work is 0.03 ns and total 60 users are considered with semiconductor optical amplifier based AND operation. Effects of optical gating are analyzed in the presence/absence of eavesdropper in terms of Q factor and received extinction ratio. Proposed system has advantages for service provider because this is mapping free technique and can be easily designed for large number of users.

Spreading code assumes an indispensable work in WCDMA system. Every individual client in a cell is isolated by an exceptional spread code. PN grouping are commonly utilized in WCDMA framework. For example, Walsh codes or gold codes as spread code. Data received from WCDMA are transmitted using chaotic signal and that signal is generated by using logistic map. It is unsuitable to be utilized as spreading sequence. Using a threshold function the chaos signal is changed in the form of binary sequence. Consequently, QPSK modulation techniques is analyzed in W-CDMA downlink over Additive white Gaussian noise channel (AWGN) and Rayleigh multipath fading channel. The activity was assessed with the assistance of BER contrary to SNR utilizing parameters indicating the BER in low to high in SNR.

Optical CDMA (OCMDA) technology directly encrypts optical transmission links at the physical layer, which can improve the security of communication system against fibre-optic eavesdropping attacks. System parameters will affect the performances of OCDMA systems, based on the wiretap channel model of OCDMA systems, "secrecy capacity" is employed as an indicator to estimate the effects of system parameters (the type of code words, the length of code words) on the security of the systems. Simulation results demonstrate that system parameters play an important role and choosing the code words with better cross-correlation characteristics can improve the security of OCDMA systems.

In this paper, we introduce an optical network with cross-layer security, which can enhance security performance. In the transmitter, the user's data is encrypted at first. After that, based on optical encoding, physical layer encryption is implemented. In the receiver, after the corresponding optical decoding process, decryption algorithm is used to restore user's data. In this paper, the security performance has been evaluated quantitatively.

In this study, we evaluate a multipath diversity reception in underwater CDMA system by performing a lake experiment. First, we design CDMA transmitter and receiver equipped with a multipath diversity with equal gain combining (EGC) and maximal ratio combining (MRC). Then, an experiment is performed at Lake Kyungcheon, South Korea to show that the diversity combining successfully corrects bit errors caused by multipath fading.

In this paper, we investigate the performance of multiple-input multiple-output aided coded interleave division multiple access (IDMA) system for secured medical image transmission through wireless communication. We realize the MIMO profile using four transmit antennas at the base station and three receive antennas at the mobile station. We achieve bandwidth efficiency using discrete wavelet transform (DWT). Further we implement Arnold's Cat Map (ACM) encryption algorithm for secured medical transmission. We consider celulas as medical image which is used to differentiate between normal cell and carcinogenic cell. In order to accommodate more users' image, we consider IDMA as accessing scheme. At the mobile station (MS), we employ non-linear minimum mean square error (MMSE) detection algorithm to alleviate the effects of unwanted multiple users image information and multi-stream interference (MSI) in the context of downlink transmission. In particular, we investigate the effects of three types of delay-spread distributions pertaining to Stanford university interim (SUI) channel models for encrypted image transmission of MIMO-IDMA system. From our computer simulation, we reveal that DWT based coded MIMO- IDMA system with ACM provides superior picture quality in the context of DL communication while offering higher spectral efficiency and security.