Optical CDMA Networks Research Articles

Performance analysis toward 880 m/4.255 Gbps underwater optical wireless communication CDMA network based on hybrid M-ary differential pulse position modulation and double length modified prime code

Performance analysis toward 880 m/4.255 Gbps underwater optical wireless communication CDMA network based on hybrid M-ary differential pulse position modulation and double length modified prime code

Information Leakage Rate of Optical Code Division Multiple Access Network Using Wiretap Code.

Secrecy capacity is usually employed as the performance metric of the physical layer security in fiber-optic wiretap channels. However, secrecy capacity can only qualitatively evaluate the physical layer security, and it cannot quantitatively evaluate the physical layer security of an imperfect security system. Furthermore, secrecy capacity cannot quantitatively evaluate the amount of information leakage to the eavesdropper. Based on the channel model of an optical CDMA network using wiretap code, the information leakage rate is analyzed to evaluate the physical layer security. The numerical results show that the information leakage rate can quantitatively evaluate the physical layer security of an optical CDMA wiretap channel, and it is related to transmission distance, eavesdropping position, confidential information rate and optical code.

Linear programming-aided power allocation for large OCDMA networks

To provide a suitable operation in optical code division multiple access (OCDMA) networks, it is paramount to balance the powers received at the destination optical node. This work presents a solution strategy for the power allocation (PA) problem in OCDMA by rewriting it as a linear programming (LP) problem and applying two LP methods based on the Simplex method and the Interior Point method (IPM). Such LP methods proposed in the PA OCDMA context were compared with two methods available in the literature: a) hybrid ALPSO PA method, which is based on the particle swarm optimization (PSO) strategy combined with the augmented Lagrangian (AL) analytical method and the solver GUROBI; b) the high-complexity benchmark solution matrix inversion method (MIM), which is used to verify the quality of the Simplex and IPM solutions. Numerical result reveal the effectiveness and efficiency of both LP methods when compared with other competitive methods. Numerical results in terms of floating-point operations (FLOPS), normalized mean squared error (NMSE), convergence, and the evolution of the allocated power reveal the effectiveness and efficiency of both LP methods when compared with the literature methods, mainly under higher network dimensions (K≥32 optical nodes), achieving better accuracy-complexity tradeoffs. For 32≤K≤512 users, the IPM has resulted in perfect feasibility (F=0) and little complexity, i.e., an order less in terms of Flops than Simplex, twice to five times less than MIM procedure, and at least four orders less complexity than the hybrid analytical-heuristic ALPSO method.

Multiservice transmissions in optical code-division multiple access networks of spectral amplitude coding based on hypothesis testing and multiple chip decoding

I propose a multiservice scheme in optical code-division multiple access (OCDMA) networks by adapting hypothesis testing to a receiver design of multiple chip decoding. Each transmitted bit of a single user is divided into several time-domain chips carrying an identical spectral amplitude coding (SAC) signature. Multiservice transmissions are achieved by assigning the users with different chip numbers based on the user classes. Hypothesis testing is employed to derive the required chip number supporting the desired bit-error rate (BER) performance. Numerical results have shown that efficient BER classifications are achieved among distinctive classes for multiple conditions of user numbers and power levels. The proposed multiservice scheme can be transparently applied to SAC-OCDMA systems with existing optical codes and various user class numbers.

Contribution of New Three-Dimensional Code Based on the VWZCC Code Extension in Eliminating Multiple Access Interference in Optical CDMA Networks

In order to solve the problem of one-dimensional code length, two-dimensional code spatial length, phase induced intensity noise PIIN effect, improved system capacity, and increased the number of simultaneous users, a new three-dimensional spectral/time/spatial variable weight zero cross correlation code for non-coherent spectral amplitude coding-optical code division multiple access (3D-VWZCC-SAC-OCDMA) is proposed in this paper. Its construction is based on a one-dimensional (1D) spectral sequence and two-dimensional (2D) temporal/spatial sequences, which are characterized by the property of zero cross correlation ZCC. The simulation results demonstrate that our code proves high immunity against PIIN noise and shot noise, it increases multiplexing ability when the passage is from (1D) and (2D) to (3D) up to 5.112 and 2.248 times, and it saves −7.04 dBm and −5.9 dBm of the receiver power due to simple detection at the receiver; furthermore, the 3D-VWZCC system capacity has outperformed the 3D-PD, 3D-PD/MD and 3D-DCS/MD codes, which reach 3686, 2908, and 3234 times, respectively. Moreover, our code offers better performance, in terms of data rates, with up to 2 Gbps compared to previous codes, which makes the system meet the requirements of optical communication networks. Further, 3D-VWZCC is also simulated in Optisystem software, where our code offers a transmission quality Q reaching 11.56 with a bit error rate BER of 1.99×10−31 despite a high number of users.

Halton-Chaos and ALPSO power allocation methods for passive optical CDMA networks

The allocation of minimum power with guarantee of minimum rate in passive optical network optical code division multiple access (PON-OCDMA) networks is analyzed considering heuristic optimization methods such as Particle Swarm Optimization (PSO) and four variants. The base of the power-rate adaptive PON-OCDMA is the multi-length 2-D wavelength-hopping/time-spreading code called multiple-length extended wavelength-hopping prime code (MLEWHPC) to support the services of different media in accordance with the bit-rate and quality of service (QoS). The Halton-Chaos-β-PSO (HC-PSO) algorithm is proposed for solving the optimal power and rate allocation in order to maximize the EE of the optical system, subject to QoS restrictions based on the signal-to-interference plus-noise ratio (SINR) in each class of optical user and minimum required power. The proposed HC-PSO and the analytical–iterative–heuristic approach based on the augmented Lagrangian and PSO (ALPSO) method demonstrate promising performance-complexity trade-off, specially for high dimensionality OCDMA systems. The proposed hybrid analytical-evolutionary resource allocation method is corroborated by numerical simulation results, considering the tuning of heuristic evolutionary input parameters, which have demonstrated to improve the EE of the optical system when the power-rate allocation procedure is deployed dynamically in real time applications.

Performance Improvement of Optical Multiple Access CDMA Network Using a New Three-Dimensional (Spectral/Time/Spatial) Code

In this paper, a novel code named three dimensional single weight zero cross correlation (3D-SWZCC) code has been developed for spectral/time/spatial (S/T/S) encoding in non coherent optical code division multiple access (OCDMA) systems. This novel code is based on one dimensional (1D) and two dimensional (2D) SWZCC code already proposed. According to simulation results, it is really observed that 3D-OCDMA systems employing SWZCC code can resist against both thermal noise and phase induced intensity noise in other words; shot noise can be totally neglected. Mover, the proposed code can improve the system capacity up to 6, 8 and 2.98 times and save the receiver power level to reach − 8.39 dBm and − 1.5 dBm going by from (1D) to (2D) to (3D) respectively as well as this code has outperformed the already existing codes such 3D-perfect difference (3D-PD), 3D-perfect difference/multi diagonal (3D-PD/MD) and 3D-dynamic cyclic shift (3D-DCS/MD) and 3D-MD codes in terms of system’s capacity 4.82, 4.13, 3.75 and 1.29 times respectively that satisfies the optical communication networks requirements. In accordance with simulation results, 3D-OCDMA system based on SWZCC code achieves good performance and meets optical communication requirements due to low BER and high Q-factor it provides, equal to $${10}^{-27}$$ and 10 dB respectively for 1 Gbps data rate and a distance of 50 km up to 70 km.

Adaptive Transceiver Architecture With QoS Provision for OCDMA Network Based on Logic Gates

Utilization of an adaptable transceiver with quality of service (QoS) features is a promising notion to build next generation optical network. This paper proposes an adaptive transceiver design by adopting logic gates in the optical domain. The proposed design offers multiple scenarios to support QoS diversity with a slight modification of conventional optical code division multiple access (OCDMA) transceiver architecture through Sigma Shift Matrix (SSM) signature code. In particular, the proposed transceiver design categorizes the users into two classes of service, one having a higher quality level and the other having a lower quality level. Users of high class transmit at low interference versus high interference power for low classes’ users. To switch between the multiple scenarios, an optical Mux performs digital operation is developed and integrated to the transceiver design. This type of MUX is built by using a semiconductor optical amplifier (SOA). In addition, a comprehensive algorithm is developed to control the function of the adaptable transceiver. Five scenarios were formed and investigated to offer a platform for a different type of applications. A proof concept using Optisystem software demonstrates ability of the proposed architecture to efficiently switch between different levels of QoS as per user requirement and provide desired transmission capacity

Spectral and energy efficiency tradeoff in optical code division multiple access networks

AbstractA paradigm on the energy efficiency (EE) and spectral efficiency (SE) tradeoff named resource efficiency (RE) exploits the EE‐SE equilibrium, which is formulated as Pareto optimal set based on two objectives balancing power consumption against occupied bandwidth. In optical code division multiple access (OCDMA) networks, the EE‐SE tradeoff is discussed by formulating a multiobjective optimization problem, while solutions are compared by deploying the weighted sum (WS) and ‐Constraint (‐C) scalarization procedures combined with nonlinear programming methods. The generalized RE optimization problem with QoS guarantees for the OCDMA networks is formulated considering that such methods result in the same Pareto boundaries. Theoretical results demonstrate that the obtained numerical optimized solutions are efficient due to the multiobjective characteristics of the optimization problem. Also, considering the numerical tests performed, it is noteworthy that the ‐C procedure found a greater diversity of solutions inside the Pareto front when compared with the WS method.

Hopfield learning‐based and non‐linear programming methods for resource allocation in OCDMA networks

This study proposes the deployment of the Hopfield neural network (H-NN) approach to optimally assign power in optical code division multiple access (OCDMA) systems. Figures of merit such as the feasibility of solutions and complexity are compared with the classical power allocation methods found in the literature, such as sequential quadratic programming (SQP) and augmented Lagrangian method. The analysed methods are used to solve constrained non-linear optimisation problems in the context of resource allocation for optical networks, especially to deal with energy efficiency in OCDMA networks. The promising performance-complexity trade-off of the modified H-NN is demonstrated through numerical results performed in comparison with classic methods for general problems in non-linear programming. The evaluation is carried out considering challenging OCDMA networks in which different levels of service quality required were considered for large numbers of optical users. The numerical results demonstrated that the three power allocation methods attain suitable convergence for different network sizes, while both the mH-NN and SQP methods achieve suitable equilibrium with less complexity.

BER performance of OCDMA system based on optimised 2D PhC passive encoder

This study introduces an accurate design and optimisation of a passive optical code division multiple access (OCDMA) network encoder using the coupled cavity waveguide (CCW) as an optical delay line. Such CCW has the capability of providing more time delay with minimum encoder size. The proposed design and analysis are based on the two-dimensional (2D) photonic crystal (PhC) structure. Additionally, two different 2D-PhC structures are studied, in which a silicon material with an effective refractive index of 3.487 is used. The first structure is a silicon bar in air background, whereas the second one is air holes in a silicon substrate. Furthermore, the behaviour of the proposed 2D-PhC structures is studied over the wavelength, ranging from 1300 to 1600 nm. Since the structure geometry is simple with a clear operating principle, it is sufficient to use in the photonic integrated circuits. Moreover, the performance analysis of such design is investigated in terms of the bit error rate (BER) calculations. Finally, the results showed that a 21% BER performance enhancement was achieved using the optimised silicon bars in air background encoder model and this model can be utilised for the multimedia applications in the OCDMA networks.

Novel encryption technique for security enhancement in optical code division multiple access

In this paper, a novel two dimensional (2D) wavelength/time (W/T) optical code division multiple access (OCDMA) code with zero cross-correlation property to minimize multiple access interface (MAI) is addressed. The code is constructed using various features of two different one-dimensional codes, i.e., multi-diagonal code and prime hop code referred as multi-diagonal prime hopping (MDPHC) code. The proposed 2D W/T MDPHC code is generated using java software version 8.1, which is found to be optimal. In this paper, the code complexity of the proposed 2D code is also derived. In addition to the novel 2D code design, security provision at the photonic layer of the OCDMA network is also addressed by transmitting the data through a novel encrypted circuit in order to prevent attacks by an eavesdropper. In this work, the proposed encryption circuit is integrated with the proposed 2D (W/T) MDPHC OCDMA encoder to enhance the overall security performance. The proposed model is validated using optisystem software version 14. Robustness of the proposed technique against different types of attacks such as ciphertext-only attack, known plain text attack, chosen plaintext attack, energy detection attack in on off keying optical code division multiple access, Brute-force search attack is investigated theoretically. Bit error rate is also estimated for different fiber distances.

Augmented Lagrangian combined to evolutionary heuristic for energy efficiency in OCDMA networks

This paper proposes combining the augmented Lagrangian method (ALM) with evolutionary heuristic methods, as well as quasi-Newton optimization methods applied to the energy efficiency (EE) maximization in the optical code division multiple access (OCDMA) communication network. The particle swarm optimization (PSO) and a hybridization between the PSO and the gravitational search algorithm (GSA) called PSOGSA have been deployed. The ALM structure replaces the objective function and allows a best fit to the problem, and ultimately provide more information about the solution. Numerical results demonstrate the robustness and low-complexity of hybrid ALM-PSO, while the ALM associated with PSOGSA attains robustness at cost of high-complexity. In turn, the usually ALM combined with Broyden-Fletcher-Goldfarb-Shanno (BFGS) method presents convergence for a restrict scenarios, failing to perform suitably for networks with large numbers of users.

Fluorinated photopolymer cascaded MMI-based integrated optical waveguide switching matrix with encoding functions.

In this work, thermo-optic tunable 4 × 4 cascaded multimode interference based integrated optical waveguide switching matrices are designed and fabricated using photopolymer lightwave circuits. The materials of the waveguide core and cladding are fluorinated epoxy-terminated copolycarbonate and polymethylmethacrylate, respectively. The driving power that controls matrices for binary encoding of different optical switching states are simulated and analyzed. The measured insertion loss of the actual chip is < 7.1 dB and the maximum crosstalk in adjacent channels is <-30 dB. The switching time is approximately 220 μs and the extinction ratio is obtained as 21.5 dB. This flexible encoding technique can be applied for achieving optical code-division multiple-access network coders.

Constructions for optimal [formula omitted]-OOSPCs

Multiple-weight optical orthogonal signature pattern codes (OOSPCs) were introduced by Kwong and Yang for 2-D image transmission in multicore-fiber optical code-division multiple-access (OCDMA) networks with multiple quality of services (QoS) requirement. In this paper, an upper bound on the maximum code size of a (u×v,W,λ,Q)-OOSPC is obtained. A link between optimal (u×v,W,λ,Q)-OOSPCs and block designs is developed. Several infinite families of optimal (u×v,{3,4},1,Q)-OOSPCs are presented by means of semi-cyclic group divisible designs ((W,Q)-SCGDDs) and perfect relative difference families.

On the performance of OCDMA/SDM PON based on FSO under atmospheric turbulence and pointing errors

This paper proposes and analyzes an optical code-division multiple-access (OCDMA) network based on free-space optical (FSO) links for broadband access provisioning in areas where laying down optical fiber is difficult or even impossible. Spectral-amplitude coding (SAC) category generated by a compact encoder is adopted as a coding scheme with binary ON-OFF keying (OOK) modulation and direct detection. Moreover, we employ spatial multiplexing scheme to increase the capacity of the proposed network by exploiting the unused already generated (by compact encoder) codewords at a certain acceptable bit error rate (BER) level. A closed-form average BER expression is derived under the joint impact of both turbulence-induced fading modeled by the Gamma-Gamma (ΓΓ) distribution and misalignment-induced fading, in the presence of beat noise, shot noise, and thermal noise. In addition, the data link layer performance modeled by Markov chain is evaluated in terms of achieved throughput and average packet delay by considering the effects of atmospheric turbulence and pointing errors. Our results show that both the atmospheric turbulence and the pointing errors impose a detrimental impact on the achievable throughput and average delay of FSO-based OCDMA passive optical network (PON).

Constructions of optimal balanced $ (m, n, \{4, 5\}, 1) $-OOSPCs

Kitayama proposed a novel OCDMA (called spatial CDMA) for parallel transmission of 2-D images through multicore fiber. Optical orthogonal signature pattern codes (OOSPCs) play an important role in this CDMA network. Multiple-weight (MW) optical orthogonal signature pattern code (OOSPC) was introduced by Kwong and Yang for 2-D image transmission in multicore-fiber optical code-division multiple-access (OCDMA) networks with multiple quality of services (QoS) requirements. Some results had been done on optimal balanced \begin{document}$ (m, n, \{3, 4\}, 1) $\end{document} -OOSPCs. In this paper, it is proved that there exist optimal balanced \begin{document}$ (2u, 16v, \{4, 5\}, 1) $\end{document} -OOSPCs for odd integers \begin{document}$ u\geq 1 $\end{document} , \begin{document}$ v\geq 1 $\end{document} .

Energy-efficient QoS-based OCDMA networks aided by nonlinear programming methods

One of the advantages of the optical code division multiple access (OCDMA) system networks over other multiple access methods is the ability to provide differentiated classes of quality of service (QoS) for different users. The performance of the OCDMA networks is mainly limited by the multi-access interference (MAI) coming from other users sharing the same spectral resources. The suitable resource allocation in OCDMA networks allows greater capacity and the reliable deployment of the available resources in the network. This work aiming at applying and analyzing four analytical optimization methods applied to energy efficiency (EE) maximization of OCDMA networks. Hence, such optimization methods were applied and their performance-complexity tradeoffs are compared, namely the augmented Lagrangian method (ALM) (Hadi and Pakravan, 2018), sequential quadratic programming method (SQP), majoration-minimization (MaMi) approach (Sun et al., 2017; Stoica, 2004), as well as Dinkelbach’s method (DK). Tests were performed considering practical and realistic OCDMA networks with a wide range of nodes, typically K={8;16;32} nodes. The evaluated optimization methods were able to achieve convergence and perform suitably to solve the optical EE-OCDMA optimization problem. However, in a few specific high loading system configurations, the DK method did not reach full convergence; besides DK processing time was much greater compared to the promising ALM, SQP and MaMi EE-OCDMA optimization approaches.

Asymptotically Optimal Optical Orthogonal Signature Pattern Codes

Optical orthogonal signature pattern codes (OOSPCs) have played an important role in a novel type of optical code-division multiple-access network for 2-D image transmission. In this paper, we give four direct constructions for OOSPCs based on polynomials and rational functions over finite fields. We also use $r$ -simple matrices to present a recursive construction for OOSPCs. These constructions yield new families of asymptotically optimal OOSPCs.

Performance improvement of optical CDMA networks with stochastic artificial bee colony optimization technique

Abstract This paper proposes a modified artificial bee colony optimization (ABC) algorithm based on levy flight swarm intelligence referred as artificial bee colony levy flight stochastic walk (ABC-LFSW) optimization for optical code division multiple access (OCDMA) network. The ABC-LFSW algorithm is used to solve asset assignment problem based on signal to noise ratio (SNR) optimization in OCDM networks with quality of service constraints. The proposed optimization using ABC-LFSW algorithm provides methods for minimizing various noises and interferences, regulating the transmitted power and optimizing the network design for improving the power efficiency of the optical code path (OCP) from source node to destination node. In this regard, an optical system model is proposed for improving the network performance with optimized input parameters. The detailed discussion and simulation results based on transmitted power allocation and power efficiency of OCPs are included. The experimental results prove the superiority of the proposed network in terms of power efficiency and spectral efficiency in comparison to networks without any power allocation approach.