Research On Key Technology Of High-speed Facsimile System

With the development of information society, facsimile communication has been widely used for its unique superiority which requires the facsimile systems to develop into high speed, miniaturization, network and secrecy. Based on the standard G3 facsimile machine defined by ITU-T, this paper researches the software realization of facsimile communication terminals in aspects of parameters and procedures in T and V series Recommendations, theories of algorithm and programming code realization. The facsimile system in this paper is realized in standard C language, which is easy to transfer to different platform such as ARM and DSPs with high executed efficiency, and facilitates the sending and receiving facsimile on handy equipment in miniature.This paper focuses on the physical and data link layer, and realizes the whole facsimile communication procedure including source and channel coding. The main accomplished tasks of this paper are as follows:(1) Realizes the source bi-level image compression method - One-dimensional Modified Huffman Coding method. According to the features of facsimile documents, a fast coding method is adopted, and the data structure is optimized.(2) Realizes the continuous phase BFSK soft modulate procedure based on the V.21 modem recommendation, and proposes a valid orthogonal structure detecting algorithm to determine the start time of a code, and a BFSK signal demodulating algorithm based on CZT spectrum analysis.(3) Realizes V.29 signal basic modulate and demodulate procedure which includes square root raised cosine rolling-off shaping filter and orthogonal channel signal modulator and demodulator.(4) Realizes procedures for standard G3 document facsimile transmission in the PSTN defined in T.30 Recommendation, including the generating and processing varies of command and response signals, packaging and checking HDLC frames, and interface between coding data buffer and physical layer modem data buffer.The system designed in this paper has the ability to progress integrated sending and receiving procedure between two threads of terminals with whole five phases including call establishment, pre-message procedure, message transmission, post-message procedure and call release.