|Map of digital terrestrial televison broadcast standards: DVB-T, ATSC, ISDB, DMB-T/H. Successor to Image:PAL-NTSC-SECAM.svg. (Photo credit: Wikipedia)|
Satellite radio systems are actually part of a larger group of broadcasting mediums, which specialists refer to as Digital Multimedia Broadcasting or DMB. This digital transmission system is used in order to send data to different receivers such as radios, television sets or mobile phones and PDAs. There are two different ways of using digital multimedia broadcasting - S-DMB which is broadcasting via a satellite or T-DMB which uses terrestrial emitters. The complexity of the entire digital multimedia broadcasting field is huge. Out of all the features and characteristics digital broadcasting offers, satellite radio is probably the most spectacular as it generated immense interest and triggered an intense competition between the two main satellite radio broadcasters, Sirius and XM Radio. The development of satellite radio and other forms of digital broadcasting is spectacular because it offers two main qualities that terrestrial emitters are deficient in: quality and coverage. In the case of satellite radio, for example, the sound quality from a satellite broadcast is much higher than AM or FM broadcasts, as the hissing noises and transmission disturbances are eliminated.
Technical features of digital multimedia broadcasting - overview
Whether it refers to television, satellite radio or cell phone transmissions, digital multimedia broadcasting is based on the Eureka 147 DAB standard. Digital television uses the T-DMB which is made for transmissions on frequency bands III (VHF) and L (SHF). T-DMB is an ETSI standard (TS 102 427 and TS 102 428).
T-DMB uses MPEG-4 Part 10 (H264) for the video and MPEG-4 Part 3 BSAC or HE-AAC V2 for the audio. When it comes to satellite radio, there were a few issues to be resolved by the main satellite radio broadcasters. The satellite radio receiver needs to be in the line of sight of the satellite to receive the transmission – and there is the problem of having different landscaping objects block the direct transmission. Land based devices were installed in order to eliminate the lack of direct satellite transmission. Since the wider spectrum of broadcasts has to be covered, digital multimedia broadcasting uses OFDM-4DPSK modulation and a chip of T-DMB receiver is also provided by MPEG-2 Transport Stream De-multiplexer. This helps reduce the negative effects of shadowing and fading, present in many digital transmissions.
The future of digital multimedia broadcasting
The transfer from the analog world to the digital one is obvious in all fields of work. Since digital multimedia broadcasting is developing so quickly, there is a silent battle going on between the new age digital technology and the classic analog one. OF course, many compare the transition from the analog to the completely digital era with the way audio cassettes were replaced by CDs and later on even DVDs. However, the development of digital multimedia broadcasting is slower since it happens on so many levels at the same time. Digital television is taking us into new spaces that are basically hybrids of the features of regular TV and characteristics of the Internet. Satellite radio is also taking huge leaps forward, with more and more programs having satellite radio exclusivity. There are even discussion of moving events like the MLB exclusively on satellite radio, which would provide one of the first deadly strikes against terrestrial radio broadcasting. Digital data transmission is fast and accurate, and so far reality proves that the satellites used in order to facilitate broadcasting and reliable. Most digital multimedia broadcasting companies that own satellites also have backup ones ready to go in orbit and replace a defective one. Some other benefits of digital multimedia broadcasting recommend it as a next step in the development of broadcasting. From the consumer’s point of view, the quality and interactivity options of digital TV or satellite radio broadcasts are important features. Although most digital multimedia broadcasting channels and technologies are still complex and sometimes expensive, the evolution of digital broadcasting seems to be here to stay.