Reza Omrani

A Generalized Bose-Chowla Family of Optical Orthogonal Codes and Distinct Difference Sets

A new construction of optical orthogonal codes is provided in this correspondence which is a generalization of the well-known construction of distinct difference set (DDS) by Bose and Chowla. This construction is optimal with respect to the Johnson bound and has parameters n=qa-1, omega=q, and lambda=1

Analytical interference model for two-dimensional (time-wavelength) asynchronous O-CDMA systems using various receiver structures

This paper gives a probabilistic model for the interference in optical code-division multiple access (O-CDMA) systems using a conventional and hard-limiting receiver that relates the code parameters to the system performance. It is shown that for a specified number of wavelengths and chip times, the code weight and maximum collision parameter (MCP) of the code can be optimized in order to maximize the numbers of active and/or potential users. Design rules to maximize the number of active users under certain system constraint are also provided. In this study, the spectral efficiency limits in the O-CDMA system using conventional and hard-limiting receivers are studied. It is worth mentioning that the models offered in this paper do not require the knowledge of the specific codes in the code set and provide the full statistics of the interference under the random code assumption.

Codes for optical CDMA

There has been a recent upsurge of interest in applying Code Division Multiple Access (CDMA) techniques to optical networks. Conventional spreading codes for OCDMA, known as optical orthogonal codes (OOC) spread the signal in the time domain only, which often results in the requirement of a large chip rate. By spreading in both time and wavelength using two-dimensional OOCs, the chip rate can be reduced considerably. This paper presents an overview of 1-D and 2-D optical orthogonal codes as well as some new results relating to bounds on code size and code construction.

Improved constructions and bounds for 2-D optical orthogonal codes

Some bounds and efficient constructions for 2-D optical orthogonal codes (OOC) in which spreading is carried out over both wavelength and time are provided. Such codes are of current practical interest as they enable fiber-optic communication at lower chip rates. The bounds provided include 2-D versions of the Johnson bound as well as a novel bound based on an extension of the Johnson bound to non-binary alphabets. The Singleton bound is recovered as a special instance of this bound. Several constructions of 2-D OOC are presented in the paper and almost all of these are either optimal or else asymptotically optimum in the sense of having code size that equals or approaches the maximum possible as the size of the code matrix (along the dimension associated to time) approaches infinity. Our principal construction views each wavelength-time OOC as the plot of a function and the functions employed in the constructions belonging to this class are either polynomials or rational functions. Other constructions include a technique for deriving 2-D OOCs from 1-D OOCs using the Chinese remainder theorem, a means of making use of MDS codes to construct 2-D OOCs satisfying the one-pulse-per-wavelength constraint and a method of concatenating a constant-weight code with a one-pulse-per-wavelength 2-D OOC to generate OOCs with at most one pulse per wavelength

New constructions and bounds for 2-d optical orthogonal codes

Some efficient constructions and bounds for 2-D optical orthogonal codes in which the spreading is carried out over both wavelength and time are provided. Such codes are of current practical interest as they enable optical communication at lower chip rate. The bounds provided include 2-D versions of the Johnson bound as well as a novel bound that makes use of the properties of a maximum-distance separable codes.

A New Construction of Multiple Target Sonar and Extended Costas Arrays with Perfect Correlation

Previously there were no multiple target perfect families of Costas and sonar arrays. In this paper using the Welch Costas array and some results from design theory we construct four perfect auto and cross-correlation families of sonar and of extended Costas arrays.

Spreading Sequences for Asynchronous Spectrally Phase Encoded Optical CDMA

In phase encoding optical CDMA (OCDMA) the spreading is achieved by encoding the phase of signal spectrum. In this paper we first derive a mathematical model for the output of phase encoding OCDMA systems. Based on this model we introduce a metric to design spreading sequences for asynchronous transmission. Then we connect the phase encoding sequence design problem to OFDM PMEPR (peak to mean envelope power ratio) problem. Using this connection we conclude that designing sequences with good properties for samples of timing delay guarantees that the same sequence to be good for all timing delays. Finally using generalized bent function we manage to construct a family of sequences which are good for asynchronous phase encoding OCDMA systems and using these sequences we introduce an M-ary modulation scheme for phase encoding OCDMA

Topics on optical orthogonal codes

Recently, there has been an upsurge of interest in using Code-Division Multiple-Access communication over optical fiber channels (OCDMA). In this paper we provide a new Johnson-bound-optimal construction of OOC with parameter A = 1. We use the idea of the same construction to generate OOCs with A > 1. A new bound for optical orthogonal codes based on a known bound for constant weight codes is introduced. This bound is used to prove the optimality of our constructions. We also present a recursive technique for generating OOCs with λ = 1 that makes use of a recursive construction for cyclic block designs by Colbourn and Colbourn [1]. This technique has yielded several new optimal constructions for Optical Orthogonal Codes.

Construction of low density parity check codes from optical orthogonal codes

In this paper, we introduce a new method for generating low-density parity check codes (LPDC) from optical orthogonal codes (OOC). The parity check matrix of an LDPC code is constructed by selecting the rows of the parity-check matrix from amongst the codewords of an OOC, taking care to include all the cyclic shifts of a codeword when the codeword itself has been selected.

Experimental demonstration of code position modulation in an O-CDMA system to increase the number of users

A novel, code-position modulation(CPM) that permits increase in the number of active users proposed and experimentally demonstrated. CPM-O-CDMA system with 6-asynchronous users at bit-rate 2.5 Gb/s and BER<1E-9 demonstrated to increase the bit-rate by 4X.