A method is proposed to improve the image quality of mobile telephone facsimile machines. The method enables the control of action of the fax modem based on information on signal conditions.
First, abnormalities, caused by fading during transmission, are detected in the input signal. An improvement in image quality in the receiving modem is achieved by compensating for this poor signal.
Control signals, calculated using signal errors, and tap coefficients for the modem equalizer are used to control the action of the receiving modem (such as equalization and recovery of carrier and timing).
Using computer simulation to compare our method with existing methods, we confirmed the following : (1) it is possible to accurately detect the control signal which corresponds to abnormalities, (2) the modem can be controlled using these signals, and (3) the line errors in the transmitted image can be decreased.
