1,720,966 research outputs found
Performance evaluation of ASK multichannel coherent optical systems
No full textIn this work we evaluate the impairments due to laser phase noise in multichannel coherent optical systems using a heterodyne ASK modulation scheme. The effects of crosstalk due to a finite value of the channel spacing are considered in a system employing a frequency division multiplexing technique. The phase noise and the frequency spacing between adjacent channels are the fundamental parameters which determine the design criteria (e.g. the bandwidth of the intermediate frequency filters) and the performance of the receiver. The accurate statistical characterization of the filtered phase noise and of the crosstalk is the key to get accurate results: to this aim the exact moments of the random processes related to the phase noise and to the crosstalk interference are used together with a Gaussian Quadrature Rule for the evaluation of the error probability
Crosstalk interference in FSK coherent optical systems
No full textIn this work, the impairment due to crosstalk interference in a FSK coherent optical system is investigated. The crosstalk can arise from both co-channel interference due to the dual-filter receiver structure, and inter-channel interference due to the frequency division multiplexing technique in multichannel systems. Here, we perform the analysis of a multichannel system, taking into account simultaneously the two contributions to interference. An approximation of the crosstalk contributions seems necessary in order to carry out the analysis. The joint moment characterization of the filtered phase noise and of the interference is suitable to get accurate result
A comparison of CDMA, TDMA and Slotted ALOHA multiple access schemes in cellular mobile radio systems
No full textBit error rate evaluation of a dual-filter heterodyne FSK optical system
Full text linkThe frequency separation between the two channels of a dual-filter heterodyne FSK optical system is a very important parameter to evaluate in the presence of laser phase noise. In this work the impairment due to the crosstalk interference between the two transmitted tones of a weakly coherent FSK optical system is investigated.
In order to make accurate computations, the method of moments seems to be the most suitable: to this aim, in this work an algorithm for the moments evaluation is proposed. The numerical results are then compared with a Monte Carlo simulation approach
Outage probability in personal communication systems in the presence of Rice fading
No full textMany studies have dealt with the outage probability evaluation for mobile radio systems in faded/shadowed propagation environments and the main results available in the literature consider Rayleigh fading and log-normal shadowing or, eventually, Rice-Rayleigh fading without shadowing. An algorithm for the outage probability evaluation when the propagation medium suffers Rice fading, log-normal shadowing, a power loss inversely proportional to a power of the distance transmitter-receiver, additive white Gaussian noise and the radios randomly distributed on the ground is presented. The method is general, simple and fast, so that it can be applied in the comparison of system performance for different system parameters in personal communication systems. Examples of application of the algorithm to different radio layouts are given in the pape
Performance evaluation of slotted Aloha for digital voice cellular communications
No full textThe performance of mobile communications is critically dependent on the multiple access protocol used to access the network from the mobiles. In recent years many proposals have been compared on the basis of spectrum efficiency measured as the number of voice channels which can be accommodated in a given bandwidth per unit area and TDMA versus CDMA has captured the major attention in the past. Hereafter we propose a new packet-voice random access protocol by taking into account the effect of ACKs, random channel attenuation due to fading, shadowing and interference. The system efficiency is reasonable for a slotted Aloha random access protocol and suggests further studies in this directio
Exact performance evaluation of heterodyne coherent optical systems with FSK modulation
No full textThe authors report the analysis and the performance evaluation of a coherent optical receiver with binary frequency shift keying (FSK) modulation. The receiver makes use of envelope detection with two branches for the two transmitted frequencies. The analysis is performed also in the presence of a low-pass post-detection filter. The analysis accounts for the effect of phase noise, modeled as a Brownian motion, which strongly affects the system performance. The numerical evaluation is carried out by the use of Gaussian quadrature rules and is based on previous results on the moment characterization of the phase nois
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