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1.
A new family of space/wavelength/time spread three-dimensional (3-D) optical codes for optical code-division multiple-access (OCDMA) networks has been proposed. Two types of 3-D codes have been constructed: 3-D codes with single pulse per plane and 3-D codes with multiple pulses per plane. Both codes are based on the prime sequence algorithm and have shown improved performance compared to the previously proposed two-dimensional (2-D) prime code. Effective implementation of the 3-D code has also been proposed. In order to eliminate the requirement of fiber ribbons and multiple star couplers in space/wavelength/time spread 3-D code based optical networks, a wavelength2/time scheme has been suggested, in which the periodic property of an arrayed waveguide grating (AWG) is used. It has been shown that the system performance can be maximized for given resources with a proper choice of the wavelength2/time scheme. Due to the improved performance of the 3-D code and the effective architecture of the wavelength2/time scheme, the feasibility of the OCDMA network is much enhanced 相似文献
2.
《Lightwave Technology, Journal of》2008,26(16):2840-2847
3.
Fresh Prime Codes Evaluation for Synchronous PPM and OPPM Signaling for Optical CDMA Networks 总被引:2,自引:0,他引:2
In this paper, we have proposed a novel prime spreading sequence family hereby referred to as ldquodouble-padded modified prime code (DPMPC)rdquo for direct-detection synchronous optical code-division multiple-access (OCDMA) networks. The new code is applied to both pulse-position and overlapping pulse-position modulation CDMA networks, and their performances were evaluated and compared with existing prime codes family. In addition, we have analyzed the system throughput and also introduced a new interference cancellation technique which significantly improves the bit error probability of OCDMA networks. 相似文献
4.
This study proposes a novel radio-over-fiber (RoF) system using two-dimensional (2-D) optical code-division multiple-access (OCDMA) scheme using pseudorandom (PN) codes for the time-spreading and wavelength-hopping (t-spreading/λ-hopping) codes. The 2-D system is implemented using optical switches (OSWs) and arrayed-waveguide grating (AWG) routers. By constructing 2-D codes using bipolar PN codes rather than unipolar codes provides a significant increase in the maximum permissible number of active radio base stations (RBSs). In general, the phase-induced intensity noise (PIIN) generated at high optical intensities significantly degrades the performance of a conventional multi-wavelength scheme. However, the OSW-based time-spreading method employed in the current 2-D OCDMA scheme effectively suppresses the PIIN effect. Additionally, multiple-access interference (MAI) is suppressed by the use of a wavelength/time balanced detector structure in the network receivers. The numerical evaluation results demonstrate that under PIIN- and MAI-limited conditions, the proposed system outperforms a conventional multi-wavelength OCDMA scheme by using the spectral spreading scheme to suppress beating noise. Especially, the t-spreading encoder/decoder (codec) groups share the same wavelength codec and the overall complexity is reduced and system network becomes more compact. 相似文献
5.
In this paper, a novel prime code, which is hereby referred to as ldquodouble-padded modified prime code,rdquo is introduced and employed in a synchronous optical code division multiple access for both spreading and despreading operations. We have analyzed this system signal-to-noise-ratio penalty as a function of the number of simultaneous users that is accommodated to maintain an appropriate value of the bit-error rate. In the analysis, the coherent binary-phase-shift-keying modulation is used, and at the receiver, signals are heterodyne detected and processed. In addition, in the analysis, both the receiver noise and multiple-access interference are investigated. 相似文献
6.
In this paper, we have studied the probability of error of optical code division multiple access (OCDMA) system using 2-D optical codes, namely prime hop and hybrid codes with a probability distribution approach. In order to increase the OCDMA system performance and increase the number of simultaneous users in the system, we have investigated the system when two different receivers are employed, namely, OCDMA serial interference cancellation (SIC) receivers and OCDMA correlation conventional receiver (CCR). Comparison in terms of OCDMA system's performance between these two receivers has been reported. In order to obtain the optimum OCDMA system's performance, we have studied several optical SIC receiver structures. Optimum choice of the number of stages in the SIC receiver and the threshold value on each stage has been reported. 相似文献
7.
In an optical multiple-access system, overall system throughput efficiency add significant implementation cost-reduction would be achieved if many users could access a common optical channel at any time without control among users. Recently one such scheme, an optical orthogonal code division multiple-access system (OOCDMA), was introduced by Salehi et al. (1982) for the case of no noise. In this paper, some extensions of that work are presented, including the effects of avalanche photodiode (APD) noise and thermal noise as well as interference for the OOCDMA direct-detection receiver. Since it has been shown that an optical hard-limiter before the receiver correlator can reduce the interference effect for the OOCDMA system in the absence of noise, the hard-limiter role in the presence of thermal and APD noise is also examined 相似文献
8.
OCDMA系统二维QPC地址码的设计和性能研究 总被引:3,自引:1,他引:2
通过对光纤信道波长片和时间片的重新组合,提出了一种新的适用于二维OCDMA系统的素数码(2D-QPC)的结构方案;给出了具体的码字设计步骤和过程;运用有限域理论,分析了码字的相关特性.在此基础上,根据"撞击法'研究2D-QPC应用于同步OCDMA系统时的用户容量和误码性能.结果表明:较之一维QPC,2D-QPC的相关特性有了很大的改进,最大自相关旁瓣由1降为0,最大互相关由2降为1;2D-QPC在系统容量上也有很大提高,在相同带宽,传输速率相同的情况下,比一维QPC的系统容量增加p 1倍. 相似文献
9.
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. 相似文献
10.
Che-Li Lin Jingshown Wu 《Lightwave Technology, Journal of》1998,16(8):1393-1403
In this paper, we propose a new synchronous fiber-optic code-division multiple-access (CDMA) system using adaptive optical hardlimiter and modified prime sequence code. At the receiver, the energy in one bit duration is estimated and used to adjust the threshold value of the adaptive optical hardlimiter which is placed after the optical correlator. The bit error probability of the system is analyzed with the consideration of thermal noise, shot noise, and dark current noise of the photodetector. The results show that this system can support a larger number of simultaneous users than other systems also using modified prime sequence code under the same bit error probability constraint 相似文献
11.
采用光硬限幅器和RS码的多波长OCDMA性能分析 总被引:1,自引:1,他引:0
提出了一种采用多个光硬限幅器和RS信道编码的多波长光码多分址(MW OCDMA)系统,理论分析了其误码率和(BER)和归一化吞吐量性能.结果表明,采用光硬限幅器的MW OCDMA系统BER性能将明显改善,进一步采用RS信道编码后,MW OCDMA系统BER性能将大大改善.另一方面,采用光硬限幅器的MW OCDMA系统的归一化吞吐量明显提高,特别是归一化吞吐量峰值提高了约1倍,但进一步采用RS信道编码后,MW OCDMA系统的归一化吞吐量并没有提高,在系统负载量不是很大的情况下还略有下降. 相似文献
12.
This paper proposes a novel IP routing schemes over coherent optical code-division multiple-access (OCDMA) network. As spreading code, flexible in length double-padded modified prime code (DPMPC) has been deployed. The performance has been analyzed in terms of the users' channel utilization factor in the network. The results are comparable with previous schemes and indicate that the architecture is power efficient and capable of accommodating greater number of active users with advantage of shorter code length (i.e., higher bit rate). It is shown that for a maximum bit rate the network performance can be improved by reducing the channel utilization. However, when each user in the network has a fixed bit rate, optimal channel utilization can be set for the overall network performance. Additionally, each IP packet is buffered only at the edge of this network, thus the buffer delay is significantly reduced compared with traditional routing schemes. Since the optical encoder is adjusted for number of packets rather than individually, the encoder adjusting time is also significantly reduced. Analytical results clearly indicate that coherent OCDMA technique can be a fine candidate for the future ultra fast optical IP networks. 相似文献
13.
Gamal A. Hussein Abd El-Naser A. Mohamed Osama Aly Oraby Emad S. Hassan Ibrahim M. Eldokany El-Sayed M. El-Rabaie Moawad I. Dessouky Saleh A. Alshebeili Fathi E. Abd El-Samie 《Photonic Network Communications》2013,26(2-3):74-83
This paper presents a simple and efficient multiple access interference (MAI) cancelation technique in optical code division multiple access (OCDMA) system. The proposed technique is based on hybrid frequency shift keying (FSK) with an enhanced modified prime code as a signature sequence for coding techniques. Coherent FSK modulation along with incoherent demodulation using Arrayed-Waveguide Grating has been examined in the transceiver structure. In the proposed technique, a reference signal is constructed by using one of the addressed spreading sequences, and MAI cancelation is performed by subtracting the reference signal from the received signal of the desired user. The performance of the proposed FSK-OCDMA system is compared with the performance of the existing pulse position modulation (PPM)–OCDMA system. The simulation results reveal that the bit-error rate performance of the proposed technique is superior to the performance of the pulse position modulation (PPM) technique. Also, the results indicate that the proposed technique is very power efficient, and when the bit rate is constant, the network capacity can be expanded to accommodate a large number of simultaneous active users with low error rate. Moreover, the proposed technique simplifies the hardware of the receiver design. 相似文献
14.
15.
16.
基于光正交码的多波长OCDMA与WDM+OCDMA系统的性能分析 总被引:5,自引:0,他引:5
分析了两种基于光正交码的二维光纤码分多址 (OCDMA)系统 :WDM+ OCDMA、MW OCD-MA。分析表明 ,当 WDM+ OCDMA系统存在能均匀分配波长的中央控制器时 ,它的误码率性能优于MW OCDMA。 相似文献
17.
A novel receiver for two-dimensional (2D) optical code division multiple access (OCDMA) which utilises the wavelength information of the codes to provide enhanced performance than the regular receiver is presented. The performance improvement increases with the number of wavelengths. Maximal spectral efficiency is doubled, for carrier-hopping prime codes. 相似文献
18.
In this work, we investigate the energy efficiency in optical code division multiplexing access (OCDMA) networks with forward error correction (FEC). We have modeled the energy efficiency considering the capacity of information transmitted and the network power consumption. The proposed network power consumption model considers the optical transmitter, receiver, optical amplifiers, FEC and network infrastructure as encoders, decoders, star coupler and network control in the overall optical power network consumption balance. Furthermore, an expression relating the signal-to-noise-plus-interference ratio gain for forward error correction with low-density parity-check code scheme considering the power consumption and bandwidth occupancy has been derived. Numerical results for OCDMA networks with aggregated FEC procedure have revealed the viability of the FEC deployment aiming to increase the overall energy efficiency of OCDMA networks. 相似文献
19.
In this paper, time-spreading wavelength-hopping optical CDMA system using trellis coded modulation scheme is investigated. The carrier hopping prime code and its shifted version are employed as signature sequences. Since the carrier hopping prime code is a symmetric code, the out of phase autocorrelation is zero. Applying the orthogonality of the signature sequences, the ternary transmission mechanism can be achieved. The proposed coding scheme is simple in both transmitter and receiver. As the multiple access interference and beat noise are the major deterioration of system performance, using coding scheme is an effective way to reduce the error floor. The numerical results reveal that the proposed coding scheme can significantly improve the system performance. 相似文献
20.
Compensating fiber gratings for source flatness to reduce multiple-access interferences in optical CDMA network coder/decoders 总被引:1,自引:0,他引:1
Jen-Fa Huang Chen-Mu Tsai Yu-Lung Lo 《Lightwave Technology, Journal of》2004,22(3):739-745
A fiber-Bragg-grating (FBG)-based optical code-division multiple-access (OCDMA) network coder/decoder (codec) is investigated for its interference suppression induced by nonflattened broad-band lightwave sources. Since each network user with different signature address code has different spectral distribution, the nonflattened light sources will cause multiple-access interference (MAI). Flatness compensation schemes are proposed to solve the MAI effects induced by nonflattened broad-band light sources. By arranging the same coding scheme but in different spectral coding band, spectral chips from FBG coder/compensator will incoherently power summed in the photodetectors to approach a more flattened power level. Signal-to-interference ratio (SIR) performances are evaluated with such compensation method for the discussed OCDMA network. 相似文献