When using modern Code Division Multiple Access (CDMA) in mobile communications, the user must be able to vary the transmission rate of users to allocate bandwidth efficiently. In this work, Orthogonal Variable Spreading Factor (OVSF) codes are used with the same principles applied in a low-rate superorthogonal turbo code due to their variable-length properties. The introduced system is the Var...

Conventional linear and non-linear receivers are generally ineffective in detecting direct-sequence spread spectrum (DS/SS) signals if the spreading sequences are unavailable. An investigation into using correlation-based processing is reported showing that the cyclostationary property of DS/SS provides detection capability. Finally we describe with results an emerging technique based on higher...

Spread Spectrum technology is being applied to many areas of modern communications such as Cellular Telephones, Global Positioning Satellite (GPS), and Very Small Aperture Satellite Terminals (VSATS) just to name a few. The core concept behind this technology involves spreading the data to be transmitted over a much broader spectrum than what is conventionally done. The spreading is usually ach...

We report on the design, fabrication and performance of a matching integrated optical CDMA encoder-decoder pair based on holographic Bragg reflector technology. Simultaneous encoding/decoding operation of two multiple wavelength-hopping time-spreading codes was successfully demonstrated and shown to support two error-free OCDMA links at OC-24. A double-pass scheme was employed in the devices to...

Modern communication systems extensively use Code Division Multiple Access (CDMA) technology that associates one unique code to each user. Therefore the generation of these spreading codes has drawn considerable attention amongst the researchers with a fundamental requirement of having as much distinct members as possible along with a constraint of minimizing the inter-code correlation. Since t...

We find that the asymptotic bit-error probability (BEP), pb, of a convolutionally coded code-division multipleaccess (CDMA) system in a frequency-selective Rayleigh-fading channel depends on the length of the shortest error event path and the product of symbol distances (to be defined later) along that path. Based on this observation, we propose a new spreading scheme that maximizes the length ...

Abstract Civil receivers of Global Navigation Satellite System (GNSS) are vulnerable to spoofing and jamming attacks due their signal structures. The Spreading Code Authentication (SCA) technique is one the GNSS message encryption identity authentication techniques. Its robustness complexity in between Message (NMA) Encryption (NME)/Spreading (SCE). A commonly used spreading code inserts unpred...

Spread Spectrum Communications is a technique in which the transmission bandwidth is much larger than that normally required to transmit at the given data rate. The use of this excess bandwidth provides the system with advantages in the areas of anti-jam communications, high resolution ranging, resistance to multipath fading, and low probability of intercept/detection of the transmissions. The ...

In this paper, a turbo receiver for MIMO-CDMA systems employing parity bit selected and permutation spreading is proposed. In such systems, spreading codes used by transmit antennas are dependent on the transmitted data. In the proposed system, convolutional coding is used as an outer code, while the parity bit selected scheme is used as the inner code. Detection and decoding are performed iter...