Anderson L. Sanches

Analysis of High-Speed Optical Wavelength/Time CDMA Networks Using Pulse-Position Modulation and Forward Error Correction Techniques

This paper presents a comprehensive analysis of an optical code-division multiple access (OCDMA) network based on two distinct modulation formats, namely ON-OFF keying (OOK) and pulse-position modulation (PPM). We also investigate how each of these modulation formats performs under two distinct 2-D coding schemes, i.e., single-pulse per row (SPR) and multiple-pulse per row (MPR). For both cases, we have accounted for the simultaneous effect of many different dispersion and noise mechanisms (including multiple access interference (MAI) that impair the overall system performance. We have included the laser relative intensity noise at the transmitter side, the fiber dispersive effects (group velocity dispersion (GVD), and first-order polarization-mode dispersion (PMD), and beat, avalanche photodiode (APD), and thermal noises at the receiver side. The effect of GVD and PMD, as well as the influence of noises, on the performance of SPR and MPR codes is also investigated. Another effect studied in this paper is the influence of the APD photodetector on the beat noise of an incoherent OCDMA network. To mitigate systems noises and bit error rate (BER), we have adopted a forward error correction (FEC) RS(255, 239) algorithm in both networks investigated here. New expressions for the BER with all noises and dispersion mechanisms were also derived for the SPR and MPR code schemes. Results indicated that OOK and PPM modulation schemes without additional mechanisms to mitigate MAI and other noise effects are not sufficient to accommodate 32 simultaneous users in an error-free environment (BER < 10-12). This occurs due to the already high BER at the FEC input, which severely affects FECs at the receiver side.

Throughput Performance Evaluation of Multiservice Multirate OCDMA in Flexible Networks

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.

Performance comparison of hybrid 1-D WDM/OCDMA and 2-D OCDMA towards future access network migration scenario

In this paper, we provide a performance comparison and analysis between a hybrid 1-D WDM/OCDMA system and a 2-D WHTS OCDMA system. In the hybrid system, OOC is employed as users code sequence of the OCDMA dimension. The simulation results show that the hybrid system presents better performance than the 2-D WHTS OCDMA system, and show also that under a standard BER scenario, i.e., BER = 10-9, the hybrid system can support at least 75% more simultaneous users than the 2-D OCDMA system for the analyzed case study. The analysis suggests that the hybrid 1-D WDM/OCDMA system is a qualified migration scenario since it can provide a smooth migration path from current networks towards OCDMA networks.

Highly efficient FFH-OCDMA packet network with coherent advanced modulation formats

In this paper we present, for the first time, the modelling and performance analysis of packet OCDMA networks based on coherent advanced modulation formats, namely binary and quadrature phase shift keying (BPSK and QPSK). We investigate how each of these advanced modulation formats perform under fast frequency hopping (FFH) encoding. For all cases, we have accounted for the simultaneous effect of multiple-access interference (MAI) and beat noise (BN) that impair the overall physical and link layer performance. Results indicate that networks based on BPSK and QPSK modulations possess increased packet delivery efficiency regardless of the traffic activity when compared with legacy on-off keying (OOK) based networks. The efficiency gain is maximized for intermediate traffic activity, accounting for improvements in the order of 80%.

Optimal Code Set Selection and Security Issues in Spectral Phase-Encoded Time Spreading (SPECTS) OCDMA Systems

In this paper, we perform a thorough analysis of a spectral phase-encoded time spreading optical code division multiple access (SPECTS-OCDMA) system based on Walsh-Hadamard (W-H) codes aiming not only at finding optimal code-set selections but also at assessing its loss of security due to crosstalk. We prove that an inadequate choice of codes can make the crosstalk between active users to become large enough so as to cause the data from the user of interest to be detected by other user. The proposed algorithm for code optimization targets code sets that produce minimum bit error rate (BER) among all codes for a specific number of simultaneous users. This methodology allows us to find optimal code sets for any OCDMA system, regardless the code family used and the number of active users. This procedure is crucial for circumventing the unexpected lack of security due to crosstalk. We also show that a SPECTS-OCDMA system based on W-H 32(64) fundamentally limits the number of simultaneous users to 4(8) with no security violation due to crosstalk. More importantly, we prove that only a small fraction of the available code sets is actually immune to crosstalk with acceptable BER (<;10-9), i.e., approximately 0.5% for W-H 32 with four simultaneous users, and about 1 × 10-4% for W-H 64 with eight simultaneous users.

Performance evaluation of a multirate, multiclass OCDM/WDM optical packet switch

In this paper, we propose a novel optical code division multiplexing/wavelength division multiplexing (OCDM/WDM) optical packet switch architecture capable of supporting multirate and multi-quality of service (QoS) transmission. The main idea is to use multi-weight multi-length optical orthogonal code (MWML-OOC) as signature sequence to provide diversified data rates and services. The architecture of the proposed multiservice OCDM/WDM switch is also presented. Furthermore, in order to analyze the packet loss probability (PLP) of the switch, we derive a bit error rate (BER) expression of the MWML-OOC-based OCDM system. Finally, we show that using high codeword weight and low offered traffic lead to a better PLP.

A Fuzzy solution to routing problem in Elastic Optical Networks

This paper introduces a new approach for the routing problem in Elastic Optical Networks using an intelligent system based on Fuzzy Logic. It defines a route to a given pair, considering metrics as the spectral fragmentation and the index of the slots to establish the circuit for the USA Topology. The paper outlines the performance of the external fragmentation and network utilization metrics. The simulation results show that the proposed approach has blocking rate 15.23, 1.80, 1.36 lower than Dijkstra, Pseudo Partition and Complete Sharing algorithms. The routing performance can be significantly improved as the Fuzzy system are employed and paves the way for new intelligent techniques to improve the quality of service in Elastic Optical Networks.

Throughput performance analysis of multirate, multiclass S-ALOHA OFFH-CDMA packet networks

In this paper, we propose a new throughput expression for multirate, multiclass slotted-ALOHA optical fast frequency hopping code-division multiple-access (OFFH-CDMA) packet networks considering a Poisson distribution for packet composite arrivals. We analyze the packet throughput performance of a three-class OFFH-CDMA network, where multirate transmissions are achieved via manipulation of the users code parameters. It is shown that users transmitting at low rates interfere considerably in the performance of high rate users. Finally, we perform a validation procedure to demonstrate that the proposed multirate throughput expression converges towards the single rate expression (considered as the network limiting case).

Comparison between Mamdani and Sugeno fuzzy inference systems for the mitigation of environmental temperature variations in OCDMA-PONs

This paper presents a comparative study between the Mamdani and Sugeno fuzzy inference systems (FIS) for intelligent traffic transmission over optical code-division multiple-access (OCDMA) network architectures. This FIS is capable of mitigating environmental temperature variation effects in the transmission link which are known to play an important role in the overall performance of the network. The paper outlines the basic difference between both Mamdani and Sugeno type FIS for this approach. The results highlight the performance of the two systems and the computational advantages of using Sugeno- type over Mamdani-type.

Multirate FFH-OCDMA networks based on coherent advanced modulation formats

In this paper, we propose and evaluate the performance of a new scheme for multirate optical code-division multiple-access (OCDMA) networks based on coherent advanced modulation formats, namely binary and quadrature phase shift keying (BPSK and QPSK). The proposed scheme employs BPSK and QPSK modulation formats for low and high rate transmission users, respectively. In addition, we develop a general formalism that allows performance evaluation of legacy networks based on on-off keying (OOK) modulation format. We investigate how the coherent demodulation of encoded fast frequency hopping (FFH) signals under multiple access-interference (MAI) can improve the network performance. It is shown for the first time that simultaneous users of different transmission rates can surprisingly achieve BER levels in the error-free region.