Multiclass optical orthogonal codes for multiservice optical CDMA networks

Abstract

Optical code division multiple access (CDMA)-based networks are an interesting alternative to support various traffic types of multimedia applications with highly variable performance targets. Generally, multilength codes are designed to support multirate services, while the multiweight codes are designed to support differentiated quality of service (QoS) for multimedia applications. However, existing optical orthogonal codes (OOCs) are limited to single class or multiclass with restricted weight and length properties. Therefore, there exists a lack of flexibility in the existing OOCs to support arbitrary rate and QoS. This paper presents a proposal of generation procedure and performance analysis of joint multiweight multilength strict OOCs. The approach used in this paper is to apply a methodology strongly relying on developed analytical theory that is supported by computer optimization, because it has turned out that it is mathematically intractable to construct unconstraint joint multilength multiweight OOCs using pure algebraic techniques. The generated code set fulfills the conditions of strictly OOCs, namely, the maximum nonzero shift autocorrelation and the maximum cross correlation constraints of one. The mark position difference (MPD) approach is used to generate in a flexible way the multiclass code set. The MPD results in the simple evaluation of multiclass code set cardinality. Furthermore, the multiple-access interference (MAI) in a multiclass OOC system is evaluated by modeling the interference per class as a Poisson distribution to simplify performance evaluation with acceptable accuracy.

Multiservice, multirate IP transmission over OCDMA network

“…Notice that the class 3 (circles) has inferior performance compared to the other classes, which occurs due to its lower code weight. Moreover, increasing the number of active users in class 3 has a small effect on the performance because of its low probability of interference [5].…”

“…In this paper, we employ MWML-OOC family as signature sequence of an incoherent OCDMA system to provide multiservice, multirate IP transmission [5]. The system transmits ON-OFF pulses employing on-off keying (OOK) modulation.…”

“…The system transmits ON-OFF pulses employing on-off keying (OOK) modulation. In addition, these supported services and data rates are directly related to the weight and length of the respective codes, i.e., the different code weights support differentiated-QoS (multiservice), and the different code lengths support data rate differentiation [5]. We consider a MWML-OOC-based OCDMA system capable of achieving multiservice and multirate transmission through both arbitrary code weights and different code lengths , respectively.…”

“…Next, we obtain a BER expression assuming that MAI has a binomial distribution, given that the output interference of any OCDMA system is considered to be binomially distributed [5], [8], [9].The MAI is assumed to be the main degrading factor of the system, as it is the most important noise source [1]. In addition, we assume a chip synchronous scenario, which reflects the worst possible case for the system analyses [8], [10], and consider that users transmit data bits "0" and "1" with equal probability ½ [10].…”

“…Currently, optical code-division multiple-access (OCDMA) has become an attractive technology in all-optical networking, particularly due to features like easy addition of new users, possibility of differentiated-QoS at the physical layer, and support to bursty and asynchronous networks traffic, i.e., IP traffic nature [1], [2], [4]. In addition, OCDMA provides more immunity to packet collisions than dynamic bandwidth allocation in time-division multiple-access schemes [5]. Moreover, OCDMA has a teletraffic capacity larger than wavelength-division multiple-access, especially when bursty traffic is carried out [6].…”