DIGITAL WIRELESS COMMUNICATION SYSTEM USING LMDS

摘要

PURPOSE: A digital wireless communication system using an LMDS(Local Multipoint Distribution System) is provided to improve the reliability of a service signal by performing a bi-directional digital communication service such as a VOD(Voice On Demand) service and a CATV service through the transmission and receipt of a microwave signal with 28GHz band by the LMDS. CONSTITUTION: A VOD server(10) compresses and stores video data, encodes the stored video data as an MPEG1 or MPEG2 stream, and simultaneously services 24 channels. An ATM switch(20) switches the video data outputted from the VOD server(10) according to a VOD control signal of a subscriber side and outputs corresponding downward video data. A modulating unit(30) performs a 16.64 QAM modulation of the downward video data outputted through the ATM switch(20). A combiner(40) combines the video data modulated in the modulating unit(30). An up-converter(50) converts a frequency of the downward video data outputted from the combiner(40) into a frequency with 28GHz using a download IF(Intermediate Frequency). A high power amplifier(60) amplifies the video data through the up-converter(50). A down-converter(70) receives a VOD control signal of a subscriber side inputted through an antenna and performs the down-conversion of the received VOD control signal. A demodulating unit(80) demodulates the VOD control signal of the down-converter(70). An NMS unit(90) performs an interface and real-time process of a signal regarding the network management maintenance and operation of a system. An MAC and control unit(100) performs a control and monitoring function to various devices and automatically performs a switching function and an alarm function when abnormality is generated in the system. A monitoring unit(110) monitors a state of the system. A head end unit(120) receives VOD service data received through a subscriber-side antenna(Ant2) and demodulates the received VOD service data, or modulates an VOD control signal for receiving the VOD service and outputs the modulated VOD control signal through the subscriber-side antenna(Ant2). A cell and ATM process unit(130) processes the VOD service demodulated in the head end unit(120) as original VOD service data or processes the VOD control signal as an ATM cell signal, and outputs the processed data to the head end unit(120).