Analysis: Mobile Tv Technology And Its Development
Broadcast, the receiver installed in the bus terminal first car
, metro, suburban railway, taxis, commercial vehicles and other public places, television system, the second is a hand-held receiving equipment (such as mobile phones, laptop, PMP, ultra-portable PC, etc) to meet needs of people viewing mobile TV system. This paper discusses the support of the second category of mobile terminals, that is, hand-held applications of mobile TV technology. Handheld mobile TV products now account for the absolute number is Mobile TV .
Key technologies for mobile TV 1, the wireless transmission technology Wireless receiving environment of the multi-path problems, receive signals from different paths of the transmit signal vector superposition. The introduction of different paths of different delay and phase, if the delay expanding the channel to send signals over the symbol period, the signal will have a frequency selective fading and cause inter-symbol interference, resulting in system performance.
Mobile TV business must be in a different rate of movement of mobile users with high quality and reliable video transmission, including basic stationary indoor users, low speed mobile users (less than 30km / h) and at high speed movement of vehicles users (more than 100km / h). Receive the Games as opposed to the sender generate Doppler frequency shift. This frequency shift is proportional to the speed and relative motion, it will lead to the adjacent carrier interference, affect the orthogonality between carriers. So demodulator should have a larger range of Doppler frequency shift, which is a measure of radio channel time selectivity of the scale.
2, the power consumption of mobile phone problems
In the phone system design, power consumption is one of the factors designers are most concerned about. The introduction of mobile TV services can not be too much to sacrifice the cost of standby time, users want a single charge to more than 4 hours of continuous viewing of TV programs. Past terrestrial digital broadcasting standards such as DVB-T, although the high speed reception under good performance, but not the power consumption for mobile reception for special design and optimization, now more energy-efficient DVB-T front-end also consume about 300-500mW of power, which is Mobile Battery , The economy is not enough. In the introduction of mobile TV services to mobile phone power consumption, the receiver front-end to account for about 80% of the ratio of power need to choose specifically designed for mobile TV standard, low-power design Tuner And demodulator.
3, spectrum planning In the frequency spectrum, mainly related to the four frequency bands: VHFIII (174 ~ 240MHz), UHF (470 ~ 862MHz) and L1 (1452 ~ 1492MHz), L2 (1660 ~ 1685MHz). States on the mobile TV spectrum planning is also not uniform. Multi-standard, multi-band global roaming will bring the problem of users in the U.S. to Japan may not be able to enjoy mobile TV services. To solve this problem, move the receiver's tuner and demodulator, and signal processor and software stack must have the flexibility to support multiple standards and multiple frequency bands.
4, codec technology
For the full use of spectrum resources, limited bandwidth to provide as many channels, you must use high compression ratio Audio and Video Coding techniques such as the latest video compression standard H.264 (MPEG-4Part10) and audio encoding standard AAC, including H.264, MPEG-2 compression ratio higher than 2-3 times, 1Mb / s of image data close to the MPEG- 2DVD image quality, so it is mobile TV in the most ideal source coding standard. H.264 motion compensation with DCT techniques, and directional intra prediction, variable block-based motion segmentation, context-based binary arithmetic coding, ring filter, block-based 4 4 integer transform 1 / 4 as precision motion compensation elements, such as layered coding syntax, these technologies make H.264 high compression efficiency, in the same image quality, can save more than MPEG-4/H.263 rate of about 50% .
Analysis: Mobile Tv Technology And Its Development
By: viedy
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