Throughput Performance Evaluation of Multiservice Multirate OCDMA in Flexible Networks

Abstract

In this paper, new analytical formalisms to evaluate the packet throughput of multiservice multirate slotted ALOHA optical code-division multiple-access (OCDMA) networks are proposed. The proposed formalisms can be successfully applied to 1-D and 2-D OCDMA networks with any number of user classes in the system. The bit error rate (BER) and packet correct probability expressions are derived, considering the multiple-access interference as binomially distributed. Packet throughput expressions, on the other hand, are derived considering Poisson, binomial, and Markov chain approaches for the composite packet arrivals distributions, with the latter defined as benchmark. A throughput performance evaluation is carried out for two distinct user code sequences separately, namely, 1-D and 2-D multiweight multilength optical orthogonal code (MWML-OOC). Numerical results show that the Poisson approach underestimates the throughput performance in unacceptable levels and incorrectly predicts the number of successfully received packets for most offered load values even in favorable conditions, such as for the 2-D MWML-OOC OCDMA network with a considerably large number of simultaneous users. On the other hand, the binomial approach proved to be more straightforward, computationally more efficient, and just as accurate as the Markov chain approach.

Hybrid optical CDMA-FSO communications network under spatially correlated gamma-gamma scintillation

“…The total number of simultaneous users in the network is U and the chip duration of all users' codes is assumed constant and is given by T c = T b /L, where T b is the bit period. Finally, without any loss of generality, deleterious noise sources such as optical channel impairments and time jitter are neglected since the main focus is on the MAI among the users' codes, generally considered as the dominant noise source in OCDMA networks [1,2]. …”

“…There are several noise sources that affect the performance of OCDMA networks, such as time jitter, non-linear effects, channel impairments [36], temperature variation [3] and, certainly, MAI [37]. However, since MAI is usually the dominant noise component in such networks [1,2] it is considered here as the only signal's degradation source in addition to the additive white Gaussian noise (AWGN). Notwithstanding the AWGN has no significant impact on the OCDMA performance, it may degrade the hybrid OCDMA-FSO network performance considerably due to the FSO link [8].…”

“…Optical code-division multiple-access (OCDMA) has been regarded as a prominent architecture in emerging flexible, robust and high capacity passive optical networks (PONs) that support integration of diversified data traffic types and increased bandwidth [1][2][3]. The success of this technology is mainly due its ability of sharing the underlying network resources among their users.…”

“…Thanks to OCDMA inherent spread spectrum feature, the physical bandwidth of the medium can be increased when multiplexing various information channels simultaneously with the use of spreading codes. OCDMA has also several other remarkable features, such as soft-capacity on-demand, high scalability and support for multirate as well as symmetric bandwidth support for up-and downlinks [1,2,20]. The use of coding schemes grants to OCDMA networks a higher level of data security and asynchronism if compared to other network technologies.…”

Next generation access networks: flexible OCDMA systems and cost-effective chaotic VCSEL sources for secure communications

“…An OCDMA network can efficiently carry out bandwidth allocation based on a user's traffic demand by means of different code lengths rendering this network as flexible. Flexible networks can divide their users into groups or classes, where each class has its own transmission specifications (data rate and QoS) [39]. Figure 1.4 illustrates a flexible OCDMA network with users divided by classes, where each user class has a different transmission rate and QoS.…”