Application of COFDM Technology in Wireless Image Transmission
The first advantage: in the complex electromagnetic environment, COFDM has excellent anti-jamming function.
It is superior to frequency selective fading or narrowband interference and interference between signal waveforms, and has strong anti-fading ability through the joint coding of each subcarrier. In a single carrier system (such as digital microwave, spread spectrum microwave, etc.), a single fading or interference can cause the entire communication link to fail, but in a multi-carrier COFDM system, only a small number of subcarriers are disturbed, and these Subchannels can also use error correction codes for error correction to ensure low bit error rates for transmission.
The second advantage: suitable for urban, suburban, buildings and other non-visual and blocking the application of the environment, showing excellent "diffraction" and "penetrating" ability.
Traditional microwave equipment, must be in the premise (both send and receive between the two points must be blocked) to establish the link, so the use of environmental constraints, the need to examine the environment in advance, the development of the measured point. Even if the success of "cloth", antenna orientation, cable layout and other work is also quite long-winded, not only directly limit the acquisition of audio and video sources, transmission, and system reliability, efficiency is also greatly reduced.
COFDM wireless image equipment is completely changed this situation. Because of its multi-carrier and other technical features, COFDM equipment with "non-line of sight", "diffraction" transmission of the upper hand, in the city, mountain, inside and outside the building can not be seen and blocked environment, the device can be high probability To achieve the image of the chaos transmission, not affected by the environment or affected by the environment. The end of the transceiver, audio and video source of the collection side, the receiver can be based on the scene and the requirements of the command / director of the free flow. The system is simple, reliable and flexible.
The third advantage: channel utilization is high.
This is especially important in wireless environments with limited spectrum resources. When the number of subcarriers is large, the spectral efficiency of the system tends to 2Baud / Hz.
The fourth advantage: suitable for high-speed data transmission, the rate is generally greater than 4M bps, to meet the high-quality video and audio transmission.
High-quality video and audio in addition to the requirements of the camera, the coding flow, channel rate requirements are very high. Ordinary digital microwave, spread spectrum microwave transmission, although the use of MPEG2 encoding, but the channel using 2M rate, such as E1, making the decoded image resolution is generally 352 × 288, can not meet the post-analysis, storage, compilation and other requirements.