Prime Code Family Research Articles

Performance analysis of 2-D optical prime codes for optical-CDMA

In this paper, comparative analysis of code performance of distinct optical 2-D codes belonging to the Prime code family have been examined. Various optical 2-D Prime codes such as Low-weight Prime sequence code (LW-PSC), Modified prime-hop code (MPHC), Extended prime-hop code (E-CHPC), Transposed-modified prime code (T-MPC), Transposed-sparse padded modified prime code (T-SPMPC) are considered. Hard-limiting Error Probability (HEP) equations of these codes are used to scrutinize the performance of these codes. Performance of one of the 2-D Prime codes, more specifically MPHC performs best in OCDMA systems where only Multi-user interference effect is considered. This optical 2-D MPHC code possesses very low BER value as compared to universally accepted standard with the increasing user count. MPHC provides robustness to multiple user interference affected OCDMA therefore very much apt for applications where simultaneous access of immense number of active user is required.

Experimental investigation on synchronized optical code division multiple access transmission

In this paper an experimental study on the performance of our previously reported optical CDMA co-channel interference reduction is presented, where an end-to-end synchronized CDMA network, implementing a point-to-point fiber-optic link, is modeled in the laboratory test bed. For the first time, the experimental and simulation results on bit-error rates of various prime code families using this laboratory based optical link are presented and compared both in the presence and absence of our previously reported MAI cancellation scheme. Also, to reduce the simulation time during the transmission and verify our results, we have modeled this system in the OptiSystem software. Our experimental results clearly validate all simulations results that we have reported previously.

A Novel Multi User Interference Cancellation Scheme for Synchronous OCDMA Networks

In this paper we have proposed a novel multi-user interference (MUI) cancellation scheme for OCDMA systems employing prime code families. We have also discussed in detail the feasibility and implementation of this novel scheme. In addition, the performance analysis of a few prime code families are evaluated experimentally using this newly proposed MUI cancellation scheme. The results reveal that the proposed scheme is easy to implement and totally removes the MUI effect.

Energy-Efficient High-Capacity Optical CDMA Networks by Low-Weight Large Code-Set MPC

In this paper, we have proposed a novel spreading code-set based on the prime code families, hereby referred to as transposed sparse-padded modified prime code for synchronous optical code-division multiple-access (OCDMA) networks. The proposed code-set is compared with modified prime codes (MPCs) in terms of correlation properties, bit-error rate (BER), and cardinality. This new low-weight large code-set has better correlation characteristics as compared with MPC families and, as results indicated, the new code-set has considerably improved the BER and power consumption of the OCDMA networks. We have analyzed the performance of the proposed code-set in both incoherent ON-OFF keying and pulse position modulation OCDMA systems, while the multiple access interference was the major degrading quality. The results indicate that at the BER floor of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> , the proposed code-set can accommodate greater number of users and consume less power as compared with the MPC under the same transmission conditions.

Uniform Cross-Correlation Modified Prime Code for Applications in Synchronous Optical CDMA Communication Systems

In this paper we have proposed a novel Optical Code Division Multiple Access (OCDMA) prime code, hereby referred to as the “Uniform Cross-Correlation Modified Prime Code (UC-MPC)”. A novel set of formulas is derived for construction of the UC-MPC. Also the correlation properties of the UC-MPC are analyzed and compared with other existing prime code families. Based on this new spreading code, we have analyzed and compared the performances of the following PPM-OCDMA systems (i) without interference cancellation (ii) with interference cancellation and Manchester codes and (iii) with cancellation only. We have found that the proposed UC-MPC has better correlation properties, enhances the bit error rate (BER) and improves the security, as compared with the other existing prime code families.

Enhancing spectral efficiency and capacity in synchronous OCDMA by transposed-MPC

This paper investigates a newly proposed spreading code-set based on the prime code (PC) families referred to as ‘transposed modified prime codes (T-MPC)’ for the enhancement of spectral efficiency of synchronous incoherent optical code-division multiple-access (OCDMA) networks. This code family increased the code-set cardinality up to twice of existing PC families’ size. This also implies that a greater number of users can be accommodated by the network. Since there is no longer a time-shift feature in T-MPC like in conventional modified prime codes (MPC), the code is not predictable and thus even more secure. Since the code structure is similar to MPC, its deployment in a system/network already running MPC will not require hardware modification. Due to the higher code utilization factor of T-MPC, a greater number of users are accommodated under certain bit-error rate (BER) resulting in remarkable improvement in the spectral efficiency (SE) and capacity. The T-MPC compatibility with low-weight energy-efficient MPC construction is also investigated. The BER and SE performances are analyzed and compared with existing code families. The results indicated that the T-MPC employment can improve up to 50% higher spectral efficiency.

Synchronous Optical CDMA Networks Capacity Increase Using Transposed Modified Prime Codes

A novel spreading code-set based on the prime code (PC) families, referred to as `transposed modified prime codes (T-MPC)', is proposed for synchronous optical code-division multiple-access (OCDMA) networks. The new code-set is constructed algorithmically to enhance and simplify its implementation. The proposed code-set performance is compared with existing spreading code families in terms of correlations, bit-error rate (BER) and cardinality. The proposed optical spreading code family doubles the cardinality as compared to existing PC families. This also implies that greater number of users can be accommodated in the network. Since there is no longer a time-shift feature in T-MPC like in conventional modified prime codes (MPC), the code is not predictable and thus even more secure. However, the code structure is similar to MPC, thus its employment in a system running MPC will be nondestructive. The code is also compatible with low-weight MPC. The results indicate that the proposed code-set has properties to enhance the OCDMA network capacity remarkably.

Performance Analysis of Enhanced-MPC in Incoherent Synchronous Optical CDMA

A novel spreading code set based on the prime code (PC) families, referred to ¿Enhanced-Modified PC,¿ is proposed for incoherent synchronous optical code-division multiple-access (OCDMA) network. The new code set is employed to Pulse-Position Modulation-OCDMA scheme and the system throughput is also analyzed; the overall system performance in terms of bit-error rate is then evaluated and compared with existing PC families in three types of receiver architectures: 1) basic functionalities; 2) with an multiple-user interference (MUI) cancelation; and 3) with the MUI canceler coupled with Manchester encoding. The results indicate that the proposed code set is promising to enhance the network capacity.

Analysis of Scalability and Performance in Passive Optical CDMA Networks

This paper proposes a novel architecture for coherent optical code-division multiple-access passive optical networks (OCDMA-PON). As optical spreading sequences, a recently introduced prime code family hereby referred to as double-padded modified prime code (DPMPC) has been employed and analyzed. The transceivers operate under homodyne dual-balanced detection scheme. For coherent modulation, binary phase-shift keying is employed where the phase is modulated by Mach-Zehnder external phase-modulator. The proposed architecture for optical network units and line terminals are also presented and analyzed. The network scalability of fiber link distances as well as bit-error rate, considering (1) fiber link noise e.g., amplifier spontaneous emission noise; (2) thermal noise; (3) photo-detectors' shot-noise; (4) relative intensity noise; and (5) mainly multiple-access interference, have been investigated. The results have indicated that this architecture can improve the network scalability, capacity and transmission performance, leading to the promising scheme for optical transport networks.

Incoherent Two-Dimensional Array Modulation Transceiver for Photonic CDMA

This paper proposes a novel incoherent optical code-division multiple-access (OCDMA) transceiver design, as a promising network access employing a newly introduced prime code family named as double-padded modified prime code as spreading sequences, based on the 2-D optical modulation scheme deploying frequency and polarization shift keying. Hereafter, it is referred to as F-PolSK. The novel F-PolSK-OCDMA system has been accurately analyzed taking into account the presence of 1) optical amplified spontaneous emission noise; 2) electronic receiver noise; 3) photo-diode shot-noise; and 4) multiple-access interference (MAI). The application of the optical tapped-delay lines at the receiver as a CDMA-decoder has also been investigated. The evaluation of 2-D array modulation in conjunction with OCDMA indicates that the binary combination of this hybrid scheme enhances the overall system performance. The results reveal that the proposed architecture can easily accommodate greater number of users and consume less power as compared with previous schemes. On the other hand, in polarization modulation since the optical beam power is constant, the system has immunity against the self- and cross-phase modulations. Besides, the system security is much enhanced due to 2-D advanced modulation in optical domain.

Transceiver Architecture for Incoherent Optical CDMA Networks Based on Polarization Modulation

This paper proposes a novel incoherent transceiver structure for the optical modulation scheme deploying polarization shift keying (Pol-SK) in conjunction with optical code-division multiple-access (OCDMA). The system has been accurately analyzed taking into account the presence of optical amplifier spontaneous emission (ASE) noise, electronic receiver noise, photodiode shot-noise and also multiple access interference (MAI). The application of optical tapped-delay lines in the receiver as the CDMA-decoder has also been investigated. In terms of spreading code, a newly introduced prime code family named as double-padded modified prime code has been utilized. A comprehensive set of results in the literatures showed that the performance of the binary system is approximately 3 dB better than intensity modulations. Therefore, in our following proposed transceiver architecture we have also employed binary Pol-SK modulation. Our results indicate that the proposed architecture consumes less power while enhances the system capacity. Moreover, since the optical beam power is constant, the system has immunity against the self- and cross-phase modulations. Above all, the polarization-based scheme is more promising for very-long-haul high-speed transmissions over the OCDMA networks.

Study of Phase Modulations With Dual-Balanced Detection in Coherent Homodyne Optical CDMA Network

In this paper, we examine the performance of two different phase modulation methods in coherent optical code-division multiple-access (OCDMA) systems. As optical spreading sequences, a recently introduced prime code family hereby referred to as double-padded modified prime code has been employed and analyzed. The OCDMA system operates under synchronous homodyne dual-balanced detection scheme. In this analysis, binary phase-shift keying format is deployed where the phase is modulated by either a Mach-Zehnder interferometer external phase-modulator or an injection-locking of distributed feedback laser diode's driving current. The performances of the two phase-modulation techniques in the presence of multiple-access interferences in a shot-noise limited regime are studied. Phase limitations and reasonable consequence associated with the limited phase excursion are also investigated.

Evaluation of coherent homodyne and heterodyne optical CDMA structures

This paper evaluates the coherent optical code-division multiple-access (OCDMA) techniques and examines the overall system performance in terms of signal-to-noise ratio (SNR) penalty as a function of simultaneous users accommodated to maintain an appropriate value of the bit-error rate (BER) for homodyne and heterodyne detections. As spreading codes, the proposed structures are utilizing a recently introduced prime code family hereby referred to as double-padded modified prime code (DPMPC). As a coherent modulation, binary phase-shift keying (BPSK) format is deployed. In homodyne detection, two different phase modulations are studied including either an external phase-modulator or injection-locking methods. The phase limitation and the performance for two methods plus multiple-access interferences (MAI) and receiver noise in a shot-noise limited regime are investigated. In heterodyne detection, BER analysis of the system based on only external phase modulator is examined. It is found that by maintaining BER = 10−9, this system can accommodate an increased number of simultaneous users to compare with systems which employ conventional bipolar codes.

Novel Channel Interference Reduction in Optical Synchronous FSK-CDMA Network Using a Data-Free Reference

In this paper, we propose a novel multiple-access interference (MAI) cancellation technique using a reference signal, which contains no data components (data-free) of the desired signal, and then simplifies the receiver configuration in synchronous M-ary frequency-shift keying optical code-division multiple-access (FSK-OCDMA) network. In doing so, we have taken advantage of a recently introduced energy-saving unipolar prime-code family, referred to as double-padded modified prime-code (DPMPC) as the spreading codes. In the theoretical analysis, the system upper bounded bit error rate (BER) is derived taking into account the Poisson effect on the I/O characteristics of the photodetectors. We have found that when the bit rate is constant, the capacity of this system increases by employing the proposed interference canceller and spreading code as compared with the synchronous M-ary pulse-position modulation OCDMA system with an existing interference canceller. In contrast to wavelength-division multiple access, a fewer set of wavelengths is needed as a result of only M-ary source coding.