DVB-H

Dvb-h standard is built on DVB and DVB - T two standard on standards.

A dvb-h system by the front-end dvb-h wrapper class and dvb-h modulator constitute, dvb-h wrapper class will IP data encapsulation for into mpeg-2, system transmission flow (TS), dvb-h modulator responsible for channel coding and modulation; By terminal system dvb-h modem and dvb-h terminal constitute, dvb-h modem responsible for channel demodulation, decoding, dvb-h terminal responsible for relevant business display, processing.

(1) system requirements

Because of using batteries, mobile terminal for improving the use time of battery, terminal should be able to cycle off part of receiving circuit to conserve power consumption.

For the user, when users roam to enter a new area should be still could very well after receive dvb-h business.

For indoor, outdoor, walk, ride and so on the different takeover, transmission system should be able to ensure smooth in various mobile rate in receiving dvb-h business.

With lots of pulse jamming environment, transmission system should be able to take effective measures to reduce the impact of such interference.

Dvb-h hand-held terminals as universal service standard, the system should be able to provide enough flexibility to meet different transmission bandwidth and channel bandwidth applications.

(2) protocol hierarchy classification

The network layer is not dvb-h standard range, standard only realize the data link layer and physicality.

The data link layer using time subdivision technology, used to reduce the average power consumption, hand-held terminals for smooth, seamless business exchange. MPE adopts agreement before packages to correction technology, can improve mobile use the signal-to-noise ratio (C/N) threshold and doppler performance, but also can enhance the ability of impulse noise resistance.

In the physical DVB - T is conducted on the basis of supplement, increased the 4K transmission mode and depth of content such as symbols, except the original interweave the technical features of DVB - T outside, the transfer of the parameters signaling (TPS) bit added dvb-h signaling, used to improve business development speed. Cellular logo in the instructions, and used to support the TPS when moving reception rapid signal scanning and frequency exchange. Increase 4K mode can adapt to mobile receiving characteristics and the size of the honeycomb SFN, increasing the network design, planning flexibility. 4K mode 2K and in-depth symbols interweave, can further enhance the mobile environment and impact noise environment system robustness.

Key technology

Dvb-h technology is DVB - T DVB and fusion of two technologies, but if solely rely on these two technology is dvb-h cannot completely solve the problems faced. For example, although DVB - T has already been proved in fixed and mobile, portable receive wait for a respect to have very outstanding performance, but for handheld devices speaking also needs further improvement, such as power, cellular mobile performance under, network design, etc. Therefore dvb-h added new technology module, they include:

(1) time subdivision

Time subdivision technology USES abrupt way transmit data every sudden time piece sends a business, in business transfer within the time piece business will separate possession, and points out that all data bandwidth next the same time piece produce moment of business. This handheld terminal in designated moment to receive the selected business, leisure time do in business, thus reduces energy processing the average power consumption. Of course, this is always work during the front-end transmitter, in the same business between two time piece will transmit other business data, dvb-h signal by many such time is composed of slices. From the receiver in terms of the business, receiving data is not as traditional continuous way, constant rate in the way of discrete data, so called sudden arrive between transmit. If decode terminal require the data rate lower but must be constant bitrate, receiver can docking received emergent data buffer, and then generate all the data flow rate unchanged. Sudden bandwidth is generally about 10 times more fixed bandwidth. Sudden bandwidth twice in fixed bandwidth under the condition of the power consumption can save 50%, so if bandwidth for 10 times, can save 90%.

(2) multi-protocol encapsulation - prior to error correction

Dvb-h standard in the data link layer for IP data reported increased reed · Solomon (RS) correction coding, as the MPE prior to correction coding, verify the information will be designated prior to forward error correction (FEC) segments transmitted, we call it a multi-protocol encapsulation - prior to MPE - error correction (FEC). MPE - FEC goal is to improve mobile channel the C/N, doppler performance and resistance to pulse disturbance capability.

Experiments prove even in very bad receiving environment, used appropriately MPE - FEC can still be accurate to restore the IP data. MPE - FEC data cost allocation is very flexible, in other transmission parameters under the condition of invariable, if calibration spending increased to 25%, it MPE - FEC can make use of hand-held terminals reach and receive the same antenna diversity of C/N. Dvb-h based on IP data broadcast mode.

(3) 4K mode and depth symbols intertwined

Dvb-h standard in DVB - T original 2K and 8K mode 4K mode, increased through coordination mobile receiving performance and SFN scale to further improve the flexibility of the network design. At the same time, in order to further improve the 4K mode 2K and moving the resistance to impulse noise performance, dvb-h standard is introduced for both the depth symbols interwoven technology. In DVB - T system, 2K mode providing better than 8K mode, but mobile receiving performance 2K mode symbols cycle and protect interval very short, 2K model applies only to make small SFN. Additional 4K mode symbols have a longer cycle and protect interval, can build medium SFN, network designers to better network optimization, improve spectrum efficiency. Although the optimization model of high efficiency than 8K 4K mode, but than 8K mode symbols cycle is short, can more frequently made channel estimation, provide a better move than 8K performance. Anyhow, the performance of 4K mode between 2K and 8K mode between, for coverage, the spectrum efficiency and mobile receiving performance measures supply an additional option.

(4) transmission parameters signaling

Dvb-h transmission parameters signaling for system (TPS) can offer a good robustness, easy to access signaling mechanism, can make the receiver to find faster dvb-h business signal. TPS is one has good robustness of signals, even in low C/N conditions, modem can still fast will its lock. Dvb-h systems use two new TPS bits to mark time slice and judgment optional MPE - FEC exists, in addition with DVB - T already exists bits to represent some of the sharing 4K mode, symbols interwoven depth and cellular logo.

Dvb-h standard trend of development

Dvb-h of broadcasting and communications will be a significant impact. Dvb-h business can be put into use in 2005 to 2007, and is expected to mobile television users will reach 1 million in 2009, and this number will increase to 300 million. Dvb-h inheritance in DVB - T, DVB - T network in just do small modification would send accord with dvb-h standard data flow. To adopt the DVB - T state (about 50 countries, mainly concentrated in Europe), popularlize dvb-h price is relatively low, but for the other terrestrial digital TV transmission standard countries, this problem will need to make further discussion. In the United States, terrestrial digital TV transmission standards with 8 ATSC 8-vsb technology, mobility is bad, need to introduce new technology or standard to promote digital television, at present had the company adopts dvb-h technology cloth nets; In Japan, considering the power consumption and mobility etc. Factor, dvb-h even has replaced Japan ISDB - T standard trend.

Dvb-h standard basically is to prepare for the digital television broadcast video compression technology, so is one extremely important technology, video compression of traditional broadcast standards, such as mpeg-2,, obviously can't meet the demand dvb-h. DVB organization dvb-h members examines various video compression format, one of the most important h.264 (namely is mpeg-4 first 10 parts), see [3], current problems mainly focus on the h.264 on intellectual property rights; Another compressed format is Microsoft's Win Media9, its performance is gradually improving. But too much choice may make mobile video into mess, apparently users don't want to face these each other incompatible platform, DVB organization will soon expected to give the final answer.

Dvb-h can guarantee the mobile terminal in mobile environment and micro-consumption electronic conditions, can receive digital TV very well and cooperate to use 3G networks. Besides completing its 3G network, acted as outside the function of reverse dvb-h network, such as video transmission control channel vod, television vote, television browse, interactive games, offers a variety of personalized business signaling multimedia services, so as to realize the fusion of two network.