Double Weight Code Research Articles

Development of a new direct AND (D-AND) detection technique for SAC-OCDMA systems using flexible double weight (FDW) code

Development of a new direct AND (D-AND) detection technique for SAC-OCDMA systems using flexible double weight (FDW) code

Development of New Spectral Amplitude Coding OCDMA Code by Using Polarization Encoding Technique

OCDMA is an optical access technology that has a lot of potential because it can be asynchronously accessed and provides a higher level of security. The authors presented a new DW family code, a flexible double weight (FDW) code, and a novel polarization encoding approach in this paper. The new code is applicable to both odd- and even-weighted codes. The novel polarization encoding approach may be used for numerous wavelengths that overlap. Based on analytic principles, a comparison of two widely used spectrum amplitude-coding SAC-based OCDMA codes, notably modified frequency hopping (MFH), Hadamard, and the double weight (DW) code family. The comparison was based on observing the bit error rate (BER) in each situation. The DW code has a fixed weight of two. The FDW code was introduced to reduce phase-induced intensity noise and multiple access interference (MAI) in transmission networks. FDW codes are versions of the DW code family with weights larger than two. The FDW code outperforms the Hadamard, MFH, DW, modified double weight (MDW), and enhanced double weight (EDW) algorithms. FDW has the capacity to support up to 220 concurrent users. With the new polarization encoding technology, the FDW code can travel up to 60 km at a bit rate of 2.5 Gb/s and 40 km for a 10 Gb/s bit rate.

Design of a High-Speed OFDM-SAC-OCDMA-Based FSO System Using EDW Codes for Supporting 5G Data Services and Smart City Applications

A novel free space optics (FSO) system is introduced in this article by combining orthogonal frequency division multiplexing (OFDM) with spectral amplitude coding optical code division multiple access (SAC-OCDMA) to be implemented in 5G technology and smart cities. Enhanced double-weight (EDW) codes are used as signature codes, while for the detection technique, single photodiode detection (SPD) is applied for the SAC-OCDMA system. OFDM with a four-quadrature amplitude modulation (4-QAM) scheme is assigned to the three users in the SAC-OCDMA system, each carrying 15 Gbps. Adverse weather conditions, such as clear, fog, haze, rain, and dust storm, that affect the FSO channel are considered. The performance of the proposed system is evaluated in terms of log of bit error rate and received power at different propagation distances. The simulation results show successful transmission of 3 × 15 Gbps with a propagation range of 3.45 km under clear air and 1.316, 1.045, and 0.7 km under rain conditions (light, medium, and heavy rain) with a received power of −12.6 dBm. As for haze conditions, the range and received power are 2.391 km with −13 dBm for low haze, 1.591 km with −12.7 dBm for medium haze, and 1.025 km with −12.6 dBm for heavy haze. The range is reduced and becomes 1.085, 0.784, and 0.645 km under fog conditions (light, medium, and heavy fog) with −12.6 dBm received power. Furthermore, the system achieved a range of 0.681, 0.232, and 0.102 km under dust conditions (light, medium, and heavy dust) with a received power of −16 dBm.

Performance analysis of 6 × 10 Gbps PDM-SAC-OCDMA-based FSO transmission using EDW codes with SPD detection

A new free space optical (FSO) system is proposed by combining spectral amplitude coding optical code division multiple access (SAC-OCDMA) with polarization division multiplexing (PDM). Enhanced double weight (EDW) codes are employed for the SAC-OCDMA system as well as single photodiode detection (SPD). Two polarization signals (x-polarization and y-polarization) are used; each carrying three different channels. Each channel carries 10 Gbps, so, the system capacity is increased to 60 Gbps. The proposed system is simulated and its performance is compared for the six channels under different weather conditions and is provided through the bit error rate (BER) metric. The obtained results assure a successful transmission under various climate with overall 60 Gbps capacity.

Cardinality Enhancement of SAC-OCDMA Systems Using New Diagonal Double Weight Code

Optical code division multiple access (OCDMA) provides another dimension to multiple access systems, in which each user is assigned a unique code. This allows each subscriber to simultaneously access the medium without any contention. However, simultaneous access of multiple users introduce multiple access interference (MAI) which primarily deteriorates the performance of OCDMA systems. This paper proposes a new code called diagonal double weight (DDW) code to elevate the performance and cardinality of spectral amplitude coding (SAC) OCDMA systems. Performance of our proposed code is evaluated using comprehensive analytical analysis followed by simulation analysis. Examination of bit error rate shows that DDW code along with single photodiode detection technique provides efficient performance, with added benefits of simplified design, large cardinality and ease of implementation.

120 Gbps SAC-OCDMA-OAM-based FSO transmission system: Performance evaluation under different weather conditions

A novel 120 Gbps free space optics (FSO) transmission scheme is introduced by combining orbital angular momentum (OAM) multiplexed signals with spectral amplitude coded (SAC)-optical code division multiplexing access (OCDMA) technique. Four OAM beams, each carrying three independent channels with 10 Gbps data rate, are used for increasing the capacity of the FSO system to 120 Gbps. Enhanced double weight (EDW) codes are employed for the SAC-OCDMA system. The proposed system is simulated and its performance is compared for the twelve channels under different weather conditions including clear air (CA), varying levels of rain, haze and fog conditions. The obtained results reveal that longer propagation distances between transmitter and receiver are possible with a bit error rate (BER) of ∼ 10-5. The possible distances are, respectively, 300 m, 160 m, 200 m, and 150 m, under CA, heavy rain (HR), heavy haze (HH), and heavy fog (HF), with a system capacity of 120 Gbps.

Performance and security analysis of novel ZCCRW codes in lower earth orbit based MDM-OWC incorporating hybrid modulations

Abstract Explosive data rate requirements in the satellite communication for surveillance, military services, and broadcasting have put peer pressure on the optical wireless communication (OWC) systems. Secure data transmission against eavesdropper and performance enhancement at authentic user is major concern these days. In this work, performance and security analysis of spectral amplitude codes (SAC) in mode division multiplexed (MDM) OWC have been carried out and a novel zero cross correlation resultant weight (ZCCRW) code at 100 Gbps capacity has been presented. Random diagonal (RD), Enhanced double weight (EDW), Diagonal double weight (DDW) codes have been compared through simulations and also mathematical expressions are derived under the effects of eavesdropper. Hybrid modulations have been compared to check optimal modulation with combination of Laguerre-Gaussian (LG), and HermiteGaussian (HG) modes. Results have revealed that ZCCRW code with MD-DQPSK using LG modes provide best performance and least susceptibility to eavesdropper.

Investigation of Enhanced Double Weight Code in Point to Point Access Networks

In this paper, an investigation and evaluation to enhanced double weight (EDW) code is performed, a new technique for code structuring and building using modified arithmetical model has been given for the code in place of employing previous technique based on Trial Inspections. Innovative design has been employed for the code into P2P networks using diverse weighted EDW code to be fitting into optical CDMA relevance applications. A new developed relation for EDW code is presented, the relation is based on studying and experimenting the effect of input transmission power with code weight, and the relation developed using numerical analysis method. This relation makes the estimation for the system input power needed more efficient. The results of the code has been explained by eye diagram and parametric illustrations from the simulated results. The result shows a magnificent performance of the code during high number of users and weight. On the other hand, the relation developed for power measurement helps to prevent power loss and consumption.

Performance of zero cross correlation resultant weight spectral amplitude codes in lower Earth orbit‐based optical wireless channel system

SummaryA consolidated performance investigation and design of newly constructed zero cross correlation resultant weight (ZCCRW) code is presented without mapping over optical wireless channel (OWC) in lower Earth orbit (LEO). Multiple access interference (MAI) is suppressed by incorporating proposed 1‐D code at 10 Gbps with an algorithm. A further state of the art comparison of diverse optical code division multiple access (OCDMA) codes such as multi diagonal codes and diagonal double weight codes is accomplished with proposed code in terms of root mean square (RMS) jitter, extinction ratio, MAI, quality factor (QF), and bit error rate (BER) at different linewidths, chip sizes, link lengths, and active users. It is perceived that for ZCCRW code, QF obtained is 16.5 for chip size (0.1 ns), and at 4000 km, BER 10‐9 is achieved using the forward error correction (FEC) technique. OWC system in LEO with lasers in spectral amplitude code (SAC) OCDMA is proposed for the first time as per the author's best knowledge.

MDW and EDW/DDW codes with AND subtraction/single photodiode detection for high performance hybrid SAC-OCDMA/OFDM system

In this paper, a hybrid system is introduced using orthogonal frequency division multiplexing (OFDM) technique with spectral amplitude coding optical code division multiple access (SAC-OCDMA). In this system, the AND subtraction detection is used with the modified double weight (MDW) and enhanced double weight (EDW) codes, in addition to the single photodiode detection with the diagonal double weight (DDW) code. The proposed system achieves performance enhancement in the performance enhancement concerning the maximum allowable number of users, signal to noise ratio and (minimum) bit error rate (BER) $${\Re}$$. The proposed codes that used with AND subtraction detection techniques are: MDW and EDW, while the DDW codes are used with single photodiode detection (SPD). Detection techniques are investigated to reduce the effect of both the multiple access interference and phase induced intensity noise. A comparison is performed between the conventional SAC-OCDMA systems and OFDM with SAC-OCDMA. The obtained results reveal that OFDM with SAC-OCDMA gives better performance than conventional SAC-OCDMA. OFDM with SAC-OCDMA using DDW code with SPD detection can support a high bit rate up to 10 Gbps for 70 users with a BER of 10–9.

New bipolar spectral amplitude code for cardinality enhancement in OCDMA network

A new bipolar double weight coding scheme in spectral domain is proposed for making the system more secure against the eavesdropping situation. The coding approach consists the uniform in phase cross-correlation similar to the existing codes. The design of decoder and encoder is such that they effectively transmit and receives the code. The decoder effectively eliminates the multiple access interference (MAI) by degrading the phase-induced intensity noise in bipolar mode, and balance detector method in bipolar domain improves the received power. All noise such as PIIN, shot and thermal noise have been considered during the performance analysis of system. The system performance evaluation is achieved by analysing the bit error rate variation for the factor of number of active users, received power and data rate. Result shows that system stands with the better performance than the existing methods such as bipolar M-sequence code, FCC and without mapping modified double weight code. The system accommodates the number of users in system more than 186%, 140% and 120% in comparison to existing methods such as without mapping modified double weight code, FCC code and bipolar M-sequence code. The power required for system is achieved at optimum BER (10−09) and is − 17.8 dBm which is lower than the existing without mapping modified DW code and FCC code. Eavesdropping against the unauthorised user is also analysed for proposed system. More number of users are secured in proposed approach than the existing methodes. System stands with constant and improve performance in spite of degradation, for the case of larger weight users.

Performance improvement of multi access OCDMA system based on a new zero cross correlation code

In this paper, a novel zero cross correlation (ZCC) code is proposed for spectral amplitude coding-optical code division multiple access (SAC-OCDMA) systems. The code construction method starts from the identity matrix and has several benefits summarized in both the code simplicity and flexibility. The proposed code presents also an adapted (or accepted) code length for SAC-OCDMA systems and a high SNR value that reaches respectively 3.18 and 1.84 times of the system capacity comparing to other existed codes such as modified quadratic congruence (MQC) and modified double weight (MDW) codes.

Performance Optimization of Diagonal Identity Matrix and Enhanced Double Weight Codes in Terms of Security for Short Haul Communication

Optical code division multiplexing is getting attention because it is an imminent multiple access technology which can cater ever increasing data traffic as well as multiple user access in optical networks. In this work, a zero cross correlation based diagonal identity matrix code is presented and it is compared with the enhanced double weight code to check the superior code in OCDMA system at data speed of 30 Gbps. Effect of some parameters of OCDMA system which prominently affects the security of the system and these are input power, linewidth and modulator extinction ratio. Optimization using single parameter optimization and multiple parameter optimizations has been done. In order to accomplish the work, optiwave optisystem software is used and extensive literature survey is done, issues encountered are carefully checked and to address the issues, proposed system is presented. Results are evaluated in terms of Q factor, bit error rate (BER) and signal to noise ratio. Novelty of proposed work is the search of optimal parameters of both the codes in terms of enhanced security such that eavesdropping at these optimal parameters will become tedious for unauthorized user.

An efficient SAC-OCDMA system using three different codes with two different detection techniques for maximum allowable users

In this paper, three codes spectral amplitude coding optical code division multiple access (SAC-OCDMA) are proposed and compared in terms of system performance including bit error rate (BER), number of active users, high achievable data rate, high signal to noise ratio (SNR) and the minimum received power that the OCDMA system supports to achieve a minimum BER value. The proposed codes are diagonal double weight (DDW) codes, modified double weight (MDW) codes and enhanced double weight (EDW). Different detection as AND subtraction detection technique and single photodiode detection (SPD) are investigated to reduce the effect of both the multiple access interference and phase induced intensity noise. The obtained results show that SAC-OCDMA using EDW code with SPD detection can achieve large number users with better BER (~ 10−9), SNR (> 20 dB), and minimum received power (~ − 20 dBm) relative to the other codes with other detection techniques.

Performance Evaluation of System in Free Space Optic Utilizing Gaussian Optical Filter in Different Detection Scheme

Abstract In recent years, free space optical communication (FSO) has become a leader for its unique characteristics: large bandwidth, unlicensed spectrum, simple implementation, low power and high data rate. However, we use as a transmission medium for Spectral Amplitude Coding-Optical Code Division Multiple Access SAC OCDMA system. In this paper, we investigate the optimum received power of FSO communication system employing SAC OCDMA, by using different detection technique, such us Spectral Direct Detection SDD and Single Photodiode Detection (SPD) technique under optical Gaussian filter decoder schemes with Modified Double Weight code (MDW). In this work, the adverse effects of atmospheric channel limit the possibility of a large FSO communication, moderate turbulence and hazy weather conditions are considered. The results show that the performance of the proposed system with wavelength-division-multiplexing (WDM) multiplexer (MUX) based on Gaussian optical filter with SDP detection fares better than the system employing SDD technique.

Performance of Hybrid OCDMA/WDM Scheme Under DPSK and QPSK Modulation Using Spectral Direct Detection Technique for Optical Communication Networks

Abstract The hybrid optical code-division multiple-access over wavelength-division multiplexing (OCDMA/WDM) scheme has attractive features of supporting system reach, multi Gbps data rates, security, and robustness for optical communication networks. This paper presents the performance of such scheme under DPSK and QPSK modulation formats using spectral direct detection technique. The modified double weight (MDW) code is used as spectral amplitude coding which also acts as a signature address code for the OCDMA system. The MDW code has the advantage of reducing the multiple access interference (MAI) and enhancing the security of the proposed hybrid system. The study focuses on the comparison between the two advanced modulation techniques (DPSK, QPSK) using spectral direct detection. Simulation results show bit-error-rate (BER) ≤10–09 for up to 25 km distance at the bit rate of 1 Gbps for optical communication networks.

Development of a novel two-dimensional-SWZCC – Code for spectral/spatial optical CDMA system

In order to overcome the effect of the Multiple Access Interference (MAI) and noises, and increase the number of the simultaneous users, the multiplexing capacity and data rate, this paper proposes a novel design of a two dimensional spectral/spatial code named Two Dimensional-Single Weight Zero Cross Correlation (2D-SWZCC) based on a single weight code which is characterized by a zero cross correlation and a high number of users. The proposed code is developed to be implemented in non-coherent Optical Code Division Multiple Access (OCDMA) systems. Numerical results of the design construction show that the proposed code enhances the system performance by improving its capacity, reducing the signal-to-noise ratio, and increasing the data rate. The system output performance for active user number is equal to 1.09, 1.54, 2.14, 2.215, 3.89 and 5.14 times than those of, Two Dimensional Multi-Diagonal (2D-MD), Two Dimensional Dynamic Cyclic Shift (2D-DCS), (1D-SWZCC), Two Dimension Perfect Difference (2D-PD), Two Dimensional Hybrid Flexible Cross Correlation- Modified Double Weight (FCC/MDW) and Two Dimensional Extended Enhanced Double Weight (2D-extended-EDW) codes, respectively. It can save an effective power around −3.2 dBm and −1.4 dBm at the level of the receiver compared to 2D-DCS and 2D-MD codes. Moreover, the system performance has been studied using Optisystem software. The simulation results show that the system respects the optical transmission property accommodating four users for a power of the source equal to −10 dBm, and the data rate is 1 Gbps.

Design of Variable Weight code for multimedia service in SAC–OCDMA systems

Variable weight (VW) codes for spectral amplitude coding–optical code division multiple access system are useful in multimedia applications. VW code algorithm is proposed which is based on enhanced and modified double weight codes. The proposed algorithm can be used for any combination of weights >2. The cross-correlation among all users is at most 1. This code construction algorithm ensures higher power at receiver for higher-weight users. Lower-weight users receive less power compared with higher-weight users. The difference in received power translates as varying performance, and are useful for multimedia applications. The performance of VW code is analysed using balanced detection (BD) exclusive-OR operation and direct detection with exclusive-OR operation. VW code gives comparable or better performance than previously reported code. It is observed that supportable number of users for higher weight, at bit error rate (BER) of 10−9 (data) are 28, 33 and 35 for random diagonal (RD) code, Khazani-Syed (KS) code and VW code, respectively, using BD. Supportable number of users for lower weight, at BER of 10−4 (voice) are 23, 31 and 37 for RD code, KS code and VW code, respectively, using BD.

Development and performance analysis zero cross correlation code using a type of Pascal’s triangle matrix for spectral amplitude coding optical code division multiple access networks

In this paper a new method to construct zero cross correlation code with the help of Pascal's triangle pattern called Pascal's Triangle Matrix Code (PTMC) for Spectral Amplitude Coding Optical Code Division Multiple Access (SAC-OCDMA) system is successfully developed. The advantages of this code are simplicity of code construction, flexibility of choosing code weight, number of users and acceptable code length. The numerical comparison shows that the newly constructed code is better code length than the existing codes such as Optical Orthogonal Code (OOC), Hadamard, Modified Frequency Hopping (MFH) and Modified Double Weight (MDW) codes and it supports more users than other Optical Spectrum Code Division Multiple Access (OSCDMA) codes.

Two-dimensional multi-service code for spectral/spatial optical CDMA system

A new two-dimensional(spectral/spatial) optical code division multiple access is developed by using one-dimensional Multi-Service code. The spectral/spatial proposed system can suppress the multiple access interference (MAI) by using the MAI cancellation property. The numerical analysis shows that two-dimensional multi-service code has a better performance compared to one-dimensional multi-service, two-dimensional perfect difference (2D-PD), two-dimensional Hybrid «flexible cross correlation/modified double weight» (2D-FCC/MDW)and two-dimensional extended enhanced double weight (2D-extended-EDW) codes; It accommodates 1.5, 2.5 and 3.3 times the maximum number of simultaneous users allocated by 2D-PD, 2D-FCC/MDW and 2D-Extended-EDW codes, respectively. By keeping the similar code length and increasing the spatial code length, the capacity and the available data rate are enhanced; also, the effective transmitted power and spectral width are decreased. The transit from 1D to 2D enhances around three times the system capacity.