Design And Implementation Of The Whole Software Digital Fax Communication System Based On B/S Structure

Today,with the rapid development of communication technology and network technology,facsimile communication is still widely used in daily work and life because of its real-time nature,security and reliability,and the legal effect of fax documents.With the increasing frequency of information exchange in modern society,traditional fax machines have not kept up with the times and are gradually being replaced by fax servers and fax-based network fax devices.The network fax method needs to upload the fax to a third-party server,which is not applicable in some cases.The fax-related technology used in the domestically produced fax server is mainly implemented by a modem chip that is monopolized by a foreign company,but the chip upgrade needs to be redesigned each time.Domestic research institutions mainly study the upper-layer protocol of fax,and the research progress in fax technology is slow and lacks independent intellectual property rights.Therefore,it is of great practical significance to develop a full-software facsimile communication system with good portability and independent intellectual property rights.In this thesis,through the research and software implementation of the key technologies involved in the facsimile communication system,a full software digital facsimile communication system based on B/S structure is developed.The key technologies of fax are implemented by C code with good portability.The fax function is transplanted into the chip,and the fax server hardware device with independent intellectual property rights is developed to lay the foundation.The main work done is as follows:1.Through the system architecture and platform selection,system module division and functional design of each module,the overall scheme design of the system.2.Design and implement the function of the system server-side fax sending module.After the user uploads the file for digitization,the obtained image data is subjected to MR source coding to remove data redundancy,and the signal modulation is completed by designing and implementing the scrambler,constellation coding and shaping filter,so that it can be A passband signal transmitted in an analog telephone line.Through in-depth study of the fax T.30 protocol,the HDLC frame encapsulation of the fax signaling data is completed and the modulation of the signaling signal is completed by the direct frequency modulation method.According to the T.30 communication protocol and the actual requirements,the communication process between the system and the fax terminal is designed,and finally the function of system fax transmission is realized.3.The function design and implementation of the system server-side faxreceiving module.The process of designing the communication between the system and the fax machine is established,and the acquisition of the signaling signal and the fax message signal in the facsimile communication process is realized.The analysis of the signaling signal and the demodulation and decoding of the message signal are completed,and the message message signal is restored to an image file consistent with the sender.The key technologies in signal analysis and message signal demodulation are improved and optimized.The Goertzel algorithm is used in the demodulation of signaling signals,and the window length and step value in the Goertzel algorithm are improved to further reduce the influence of clock bias on the demodulation effect and improve the accuracy of the demodulation result..In the demodulation of the fax message signal,the symbol synchronization loop based on the Gardener timing error detection algorithm is improved,which improves the operation rate and overcomes the error caused by the effective word length effect.In the carrier synchronization part,using the idea of window detector windowing,a software-based phase-locked loop with phase-detection phase-detection function is proposed and implemented,and a carrier-synchronous loop is designed together with a universal phase-locked loop.In order to further reduce inter-symbol interference,an equalization technique is introduced on the basis of the original algorithm,and a signal space inverse mapping method is proposed for inverse mapping and decoding of signal constellation.4.Build a B/S architecture fax communication system based on ASP.net +SQLserver + IIS web server,complete the web client and database design,load the fax sending and receiving functions on the server,and finally realize the two-way communication between the system and the fax machine.,through the web page to complete the fax transmission and reception.