Tatsuo Miyachi

Voiceband modem control algorithm for improving image quality of mobile telephone facsimile

The authors describe the control algorithm of V.27ter voiceband modem function for improving the image quality of mobile telephone facsimiles and present the results of field experiments to verify the effectiveness of that algorithm. First, impairments unique to the mobile telephone network, in which an analog cellular system is connected with the public switched telephone network (PSTN), are described. Second the impairment of incoming signals mobile telephone facsimile is shown and the key aspects of the voiceband modem control algorithm are described. Finally, the authors show, through experimental results, that the developed modem DSP chip can improve the image quality of mobile telephone facsimile.<<ETX>>

Improving Image Quality of Mobile Telephone Facsimile by Keeping Modem Condition Stable.

The image quality of mobile telephone facsimiles is frequently degraded by improper actions at the receiving modem due to several problems not present in standard phone lines. This paper describes a method for improving facsimile modem functions based on the results of field experiments. We conducted field experiments, and analyzed the actions of the receiving modem functions by using a facsimile simulator. This research notes the continuity of modem function control signals, especially carrier recovery and timing recovery functions, which are used in designing a method to improve carrier recovery and timing recovery functions. Also introduced is a new indicator of improvement to verify the effectiveness of this method. The results of field experiments confirm that the image quality can be improved.