System
end system is mainly composed of video and audio compression encoder, multiplexer and modulator. Since the satellite transponder lease is very expensive, and therefore the most important task is to improve the compression ratio front-end system, to transmit more programs over a limited frequency band of the transponder as possible.
multiple programs to use satellites in two ways: SCPC MCPC mode and manner, DTH use MCPC mode. In MCPC mode, in addition to MPEG-2 video audio signal compression, dynamic statistical multiplexing technology, this new role is particularly important. Dynamic statistical multiplexing is a real-time allocation of bandwidth needed technology, has a great role in improving the bandwidth efficiency across multiple programs, so each encoder manufacturers will be considerable force into the development of dynamic statistical multiplexing technology. Dynamic statistical multiplexing algorithm is no international standard, each vendor has its own unique technology, the BIRTV this exhibition, each encoder manufacturers have demonstrated their dynamic statistical multiplexing technology to the audience.
NDS in British show the latest Reflex E5610 encoder and a multiplexer, a statistical multiplexing coding method employed by the previous frame or previous change rate "Slice" image when a subsequent adjustment to the image encoding quantization step size, i.e., using tracking mode to predict the rate of change.
US Divicom company launched a new MV40 encoder and multiplexer MN20, "forward-looking" way of using statistical multiplexing, which uses two-pass encoding mode. MV40 using three C-Cube of E4 coding chip, secondary encoding, the first encoding process to predict the optimal coding rate, the second coding procedure is adjusted according to when coding the quantized first prediction result step.
properties of the two forms of statistical multiplexing techniques differ from the statistical accuracy point of view, a prediction coding is required, inevitably there will be some prediction error ,, and "forward" this way the prediction error does not exist, a high statistical accuracy; see from the encoding delay, a delay encoding short, "forward-looking" approach will have much longer. Furthermore, once encoding has an important performance indicator is the maximum variable range of a coding rate between the coding system NDS This indicator is 0.7Mbit / s ~ Mbit / s.
the world's most advanced statistical multiplexing technology can already be ten sets of standard TV programs are compressed to less than 20Mbit / s, which means that can be forwarded up to 10 sets of television programs on a 27MHz transponder of the satellite , significant savings in resources transponder, has significant practical value.
receiving system
DTH user receiving antenna and receiving system integrated receiver decoder (IRD) and a smart card (the SmartCard) by a small satellites.
DTH user receiving antenna is generally not more than 1 m, usually about 0.5 to 0.6 m, can be placed in an ordinary home.
DTH is responsible for the IRD four main functions:
decoding the program stream, and output on the TV.
in the smart card using the key to decrypt.
to receive and process a variety of user commands.
download and run a variety of software applications.
It should be noted, DTH in the IRD has been not only a hardware device, it also includes a large number of operating systems and applications software. With the expansion of services and functions, the role of IRD software systems have become increasingly significant, the product is more successful international OpenTV.
transmission
and the uplink transmission system comprises a front end and an uplink communication line upstream station apparatus. Front to transmit uplink station program in two ways: IF and digital baseband transmission mode transmission scheme. When using municipal system is placed in the front end of the intermediate frequency transfer scheme, to facilitate monitoring and centralized management; the use of digital baseband transmission system it is possible to transmit a plurality of programs on the way forward in the fiber, two methods have advantages and disadvantages, the need selected depending on the application.
receiving
conditional access system has two basic functions:
Program code stream by encrypting the scramble method;
to programs and user authorization.
DTH internet international common conditional access system: NDS, Irdeto, Access, NagraVision, GI, TV / COM and the like.
conditional access system via the front end system din reuse, generates three kinds of information.
control word controls a pseudo-random sequence generated by the scrambler.
EMM is information to authorized users.
ECM is the information associated with the program authorization.
EMM and ECM are transmitted together with the program stream to the receiver.
User Management System (SMS: SubsciberManagementSystem)
User management system is the heart DTH platform, mainly performs the following functions:
Registration and manage user data.
buy and packaging programs.
billing program to develop standards for user charges.
DTH platform market forecasting and marketing.
User management system includes a variety of user and program information there are data management system and there are many answers to users responsible for consulting customer service representative (CSR) constitutes a user call center.
satellite
DTH platform uses a high-power radio or communication satellite. While the international community generally agreed that DTH should adopt high-power direct broadcast satellite (BSS), only three international DTH platform uses a BSS, the rest are made of high-power communications satellite (FSS). Available over high-power DTH satellite my country has three: the asterisk in the Asia-Pacific number 10 and 7, which are FSS satellites, another one is in the Star 9 broadcast satellite belongs.
Other explain
band
veteran band from Dusseldorf, Germany DieTotenHosen. German punk movement was founded in the era of the early 1980s. It is a little taste of the famous German industrial PunkMetal band.
hypersensitivity
delayed-type hypersensitivity (delayedtypehypersensitivity), also known as delayed type hypersensitivity. Th1 effector cells during the release of cytokines exert immune effector antigen clearance, large activated monocytes - phagocytes and lymphocyte recruitment to the site where the antigen, resulting in the site where the antigen to mononuclear cell infiltration of the inflammatory response, as this delayed-type hypersensitivity. That type IV hypersensitivity.
hole drilling
means Drill-the-hold on the rig industry, i.e. DTH drilling.
Great Tyrant
network terminology