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Optical Code Division Multiple Access (OCDMA) is considered as the strongest candidates for the future high speed optical networks due to the large bandwidth offered by the system, Based on the vast amount of bandwidth, OCDMA systems have received much attention in fiber optic Local Area Networks where the traffic is typically bursty. However, Mult...
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... that there are N optical encoder and decoder pairs (users) in the fiber-optic CDMA system under investigation (Figure 2). Each user in this system is assigned a unique optical signature code with desired distinguishable correlation properties, so simultaneous users are allowed to send their data asynchronously through this code. ...
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Citations
... Communication System with Optical Encoder and Decoder in configuration [1] In the OCDMA systems, the major drawback which limits the QoS of the system is the MAI due to the other interfering users. Author has also studied the MAI cancellation techniques using Optical Parallel Interference Cancellation (OPIC) [9]. In this technique, interference is cancelled but at the receiver's side in electrical domain. ...
Optical CDMA (OCDMA) technology provides best solution for multiuser communication system with the help of appropriate codes. However, for multiuser system, Multiple Access Interference (MAI) increases as the number of users increase. It is very much essential to limit MAI. Use of Optical Hard Limiter (OHL) is one of the popular techniques to reduce MAI. But, use of OHL to reduce MAI has certain drawbacks like its incapability to handle random signals effectively. Hence, in this paper, we proposed a technique using Optical Normalizer (in Non Uniform Mode) for dynamic thresholding. This technique is proved to be much effective to handle random signals. Results indicate significant improvement in term Quality of Service (QoS). In our analysis, we have used Pseudo Orthogonal (PSO) codes. The simulations are carried out using OptSim (RSOFT).
... In the OCDMA systems, the major drawback which limits the Quality of service (QoS) of the system is the MAI due to the other interfering users. Author has also studied the MAI cancellation techniques using Optical Parallel Interference Cancellation (OPIC) [9]. In this technique, interference is cancelled but at the receiver's side in electrical domain. ...
Optical Code Division Multiple Access (OCDMA) has been proposed as an attractive alternative for access networks due to its advantages over current Wavelength Division Multiplexing (WDM) and Optical Time Division Multiplexing (OTDM), such as asynchronous transmission, fair division of bandwidth and quality of service control. However, OCDMA systems suffer from the phenomenon of Multiple Access Interference (MAl) which is generated by other channels transmitting over the same fiber as the desired data signal. This MAl noise reduces system performance so it is very much essential to limit MAI. Hence in this paper we analyzed bit error rate (BER) performance with fixed and dynamic thresholding. There are certain drawbacks of fixed thresholding in terms of BER and random signals. We proposed a technique using Optical Normalizer (in Non Uniform Mode) which acts as dynamic thresholding. This technique is proved to be much effective to handle random signals and improve BER. In our analysis, we have used Pseudo Orthogonal (PSO) codes. The simulations are carried out using OptSim (RSOFT) software.
In this paper, a new technique of transmission, reception of optical codes and a smart computational and decision based bit detection technique has been proposed in Synchronous Optical Code Division Multiple Access network. Here, Modified Prime Codes is used and simple On-Off keying modulation is considered. A simple simulation is run in OptiSystem 9.0 to prove practical applicability of the proposed system. This proposed system can accommodate up to almost maximum users available if the hardware can adjust to it.
Interference cancellation is one of the key technologies in wireless optical code division multiple access (CDMA) systems. The principle and performance of blind multi-user detector algorithm based on recursive least square (RLS) are analyzed, and it is applied to wireless optical CDMA using optical orthogonal code (OOC). The selecting principle of forgetting factor, the convergence and error rate performance caused by forgetting factor are discussed. A RLS blind multi-user detection algorithm is proposed using variable forgetting factor. The forgetting factor is modified. The results show that the system using the improved method can get faster convergence speed and tracking speed of convergence and the estimation error is smaller. The signal to interference ratio is improved from 6 dB of the traditional algorithm to 9 dB. The RLS algorithm with variable forgetting factor is suitable for the wireless optical CDMA system using OOCs, and the performance of tracking the desired user signal is very good.
Optical Code Division Multiple Access (OCDMA) is a technology which supports multiple simultaneous transmissions in the same time slot and the same frequency to realize multiplexing transmission and multiple accesses by coding in the optical domain. But one of the major disadvantages of the multi user system is the Multiple Access Interference (MAI) that can occur due to the false detection of incoming signals by the users at receiver side. This MAI can be reduced by using an Optical Hard Limiter (OHL) at the receiver front end. But use of OHL has the drawback that it is incapable of handling random signals effectively. So a new technique using Optical Normaliser (ON) for dynamic thresholding is introduced, that can effectively handle random signals. The Bit Error Rate (BER), Q factor and the received power of the system using ON is analysed and improvement in above factors are observed than that of using OHL. The simulations are carried out using commercially available simulator from Rsoft, OptSim 5.3.
Optical CDMA systems suffer from multiple access interferences (MAI) originating from other simultaneous users. As the number of simultaneous user increases, the bit error probability becomes higher. Several interference cancellation techniques have been proposed aiming at lowering MAI as Optical Parallel Interference Cancellation (OPIC), this system is complex, and the hardware is increased as the number of users increased which consume cost and processing time, so it is not practical for use in LAN. In This research we introduce One-Stage Optical Parallel Interference Cancellation (OS-OPIC) with one Optical Hard Limiter (OHL) and Double Optical Hard Limiter (DOHL), which based on OPIC; this system is simple, effective in cost, and suitable for LAN applications, it reduces MAI, gives better performance and lower BER than OS-OPIC. We use an Optical Orthogonal Code (OOC) as a signature code.
Passive optical division multiple access codes are of great interest in the transmission of broadband networks. However, multiple access interference is one of the main factors limiting the decoding performances. Moreover, these networks suffer from imperfections in up link powers originating from active different users at different locations on the perimeter of the central optical line terminal. In this paper, we examine the near-far impact due to imperfect power control, particularly in the up link passive optical network. We consider two groups of critical users for this purpose. The originality of this work consists in proposing a receiver based on the linear parallel interference cancellation with additional gain factor compensation to mitigate the multiples access interference and to solve the problems of the uncontrolled input power. Link quality of the proposed receiver is analytically established by bit error probability evaluation under the Gaussian approximation. Also, a comparison study to other types of receivers of similar algorithmic complexity is done.
