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Mobile digital multimedia communication system
One, the system constitution:
Wireless multimedia transmission system mainly consists of transmitting, receiving and relaying three functional unit.
1, the transmitter unit:
Transmission unit comprises a camera, transmitter, antenna feeder component VN-COMT.
2, the receiver unit:
The receiving unit is composed of, VN-COMT receiver, antenna and terminal (computer display, etc.)
3, relay unit (not as this project scope):
Relay unit selection of preparation in need of long-distance transmission, the public can access relay network (such as satellite, microwave, optical fiber, IP etc.), can also configure the VN-COMT frequency relay transmission.
The working principle, equipment two:
1, the transmitter:
Camera acquisition composite video two-way audio analog signal A/D conversion, MPEGIV compression coding - COFDM modulation and RF power amplifier and antenna.
2, the receiving end:
Antenna for radio frequency signal receiving - low noise amplifier - COFDM - MPEGIV - D/A transform demodulation decoding analog amplification to terminal analog signal output (monitor, computer) treatment.
3, if the baseband signal processing unit:
In the transmitter, the multiplexer through the interface circuit of input corresponding to the video signal, the speech signal (coded by the ADPCM) and the data signals are asynchronous multiplexing, error correction coding synthesis way signal, then the emergence and spread spectrum code generator of spread spectrum code together, form a base band signal. At the same time, T/R control signal to the switch T/R transceiver, the completion of TDD operation.
At the receiving end, first the received baseband signal is despread operations, then the error control operation, finally sent to the demultiplexer, separating the video signal, the speech signal (ADPCM decoder), data signal, the lower corresponding terminal equipment sent through respective interface circuits. The process is completely processed by software technology.