Hamza M. R. Al-Khafaji

A new two-code keying scheme for SAC-OCDMA systems enabling bipolar encoding

In this paper, we propose a new two-code keying scheme for enabling bipolar encoding in a high-rate spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) system. The mathematical formulations are derived for the signal-to-noise ratio and bit-error rate (BER) of SAC-OCDMA system based on the suggested scheme using multi-diagonal (MD) code. Performance analyses are assessed considering the effects of phase-induced intensity noise, as well as shot and thermal noises in photodetectors. The numerical results demonstrated that the proposed scheme exhibits an enhanced BER performance compared to the existing unipolar encoding with direct detection technique. Furthermore, the performance improvement afforded by this scheme is verified using simulation experiments.

Impact of different transceiver design on the performance of SAC-OCDMA systems

Multiple-access interference (MAI) and phase-induced intensity noise (PIIN) are the principal limitations for the performance of spectral-amplitude-coding optical codedivision multiple-access (SAC-OCDMA) systems. Focusing on increasing the performance and reducing the bit-error rate (BER), the ideal transceiver design should be accentuated. In this paper, we studied the effect of the different combination of codes, detection techniques, and the usage of single and multiple light emitting diodes (LEDs) in SAC-OCDMA system to highlight the main point that affect the most in reducing the BER as well as increasing the performance. We simulate the system performance of direct detection, AND subtraction detection, as well as modified-AND subtraction detection techniques with enhanced double weight (EDW) and modified double weight (MDW) codes via OptiSystem software. Simulation results show that the detection techniques significantly enrich the performance compared to the usage of diverse codes. Although the multiples LEDs give better performance than single LED in SAC-OCDMA system, the single LED still able to provide a good performance with less costly design than multiples LEDs.

A steerable 28 GHz array antenna using branch line coupler

This paper provides details on the design of a beam steerable array antenna for mobile applications at 28 GHz frequency band. The array is designed using a Rogers RT/duroid 5880 substrate material of 0.254 mm thickness and dielectric constant of 2.2. The designed antenna is fed by a 2 × 2 Butler matrix (BM) which also serve as a beam former to obtain the beam scanning of from -16 to 16 degrees. The 6-element array realized a peak gain of 14 dBi at the designed frequency and a wideband that cover 63 % of the frequency range. The designed antenna is applicable to 28 GHz frequency band proposed for future generation mobile communications.

A novel encoding and decoding structure for SAC-OCDMA systems enabling high-rate transmission

In this research, we present a novel encoding and decoding structure based upon two-code keying for high-rate spectral-amplitude-coding optical code-division multiple-access (SAC-OCDMA) systems. The OptiSystem (version 13) simulation software is used to measure the bit-error rate (BER) performance for different fiber lengths. The results indicate that the proposed coding structure clearly provides a significant improvement in performance when compared to the prior reported direct detection technique.

A new approach for enabling bipolar encoding in high-rate SAC-OCDMA systems

In this paper, a new two-code keying approach to enable bipolar encoding in high-rate spectral-amplitude-coding optical code-division multiple-access (SAC-OCDMA) systems is suggested. The analytical expressions are developed for the signal-to-noise ratio (SNR) and bit-error rate (BER) of SAC-OCDMA system based on the recommended approach using multi-diagonal (MD) code. The results indicate that the proposed approach exhibits an improved BER performance in comparison to the traditional unipolar encoding with direct detection technique.

Implementation of Switched Beam Smart Antenna Using Artificial Neural Network

The capacity enhancement promised by switched beam smart antenna is a function of efficient selection of the active beam at each point in time. This article presents the use of artificial neural network (ANN) to improve the performance of switched beam smart antenna. The proposed method is based on feed forward backpropagation ANN. In this design, samples of the calibration of the footprint of the base station is mapped to the radiation pattern of Butler matrix (BM) base station antenna arrays. A

An innovative encoding/decoding architecture based on two-code keying for SAC-OCDMA systems

4\times 4

A 4 × 4 Butler Matrix for 28 GHz Switched Multi-Beam Antenna

4×4 BM is designed to implement the developed technique and a digitizer applied to obtain the ANN training data. The results are compared with the existing numerical method and negative selection algorithm based on received signal strength indicator. It is shown that the proposed method exhibits a better switching performance.