Guided by Dr. K.R. Rao Irfan Kerawalla [email protected] ID: 1000719155 DVB-SH System for Broadcasting to Handheld DevicesIntroduction Mobile TV is expected to become one of the largest markets for mass media. Growing number of mobile phone users around the globe has triggered excessive demand for multimedia content. People are constantly on the move and want all the latest news and social life updates on their fingertips. Users want high quality multimedia content delivered at fast speed.Requirements of a mobile TV service Low power consumption technology. Stable reception with mobility. High speeds and clear picture quality. Minimal loss of signal due to fading and multipath effects.What is DVB-SH? Digital Video Broadcast - Satellite Services to Handheld Devices (DVB-SH) [1] is the name of a transmission system standard designed to deliver video, audio and data services to vehicles and handheld devices It is designed to use frequencies below 3GHz, typically around 2.2GHz. The system and waveform specifications have been published as ETSI standards. (TS 102 584, TS 102 585 and EN 302 583). [1]Applications of DVB-SH Broadcasting of radio and TV content. Broadcasting of audio or video content customized for mobile TV (e.g. virtual TV channels, podcasts,). Data delivery (“push”), e.g. for ring tones, logos. Video-on-demand services. Informative services (e.g. news) including location-based services. Interactive services via an external communications channel e.g. Universal Mobile Telecommunications System(UMTS).System architecture of DVB-SH Figure 1. DVB-SH network architecture [8]Band used for DVB-SH transmission DVB-SH seeks to exploit the less congested, higher frequency, S-band where there are opportunities for mobile satellite services (MSS) systems, operating in conjunction with complementary ground components (CGC). S-band enables small omnidirectional antennas to be used in mobile devices. Figure 2: S-Band used in DVB-SH transmission [7]Compression in DVB-SH DVB-SH uses H.264/AVC [19] compression standard. Figure 3. H.264 encoder block diagram [10]Figure 4. H.264 decoder block diagram [10]Orthogonal frequency division multiplexing (OFDM) It is a frequency-division multiplexing (FDM) scheme used as a digital multi-carrier modulation method. Signal is split into a number of streams, each with a low bit rate. OFDM (Orthogonal Frequency Division Multiplexing) [8] is the natural choice for terrestrial modulation and is the basis of both the DVB-H and DVB-T systems. DVB-SH introduces a second scheme, a time division multiplex (TDM), leading to two reference architectures termed SH-A and SH-B: [8] • SH-A uses OFDM both on the satellite and the terrestrial link • SH-B uses TDM on the satellite link and OFDM for the terrestrial link.Time Slicing The objective of time-slicing is to reduce the average power consumption of the terminal and enable smooth and seamless service handover. [8] Time-slicing enables a receiver to stay active only a fraction of the time, while receiving bursts of a requested service. Time-slicing also supports the possibility to use the receiver to monitor neighboring cells during the off-times. By accomplishing the switching of the reception from one transport stream to another during an off period it is possible to accomplish a handover decision.Block diagram of the DVB-SH system Figure 5. Conceptual description of a DVB-SH system [11] (MPE: multiprotocol encapsulation – forward error correction, TPS: transmission parameters signaling)Figure 6. Conceptual description of a DVB-SH receiver [11]Basic parameters in DVB physical layer Table 1. Physical layer parameters and data rates of DVB-SH system [11] Table 1. Physical layer parameter and data rates of DVB-SH system [14]Table 2. Framing and typical data rates in an S-band DVB-SH-A system in 5 MHz spectrum slot [14]Figure 7. Transmission mode influence in 16QAM 2/3 [11].Testing DVB streams: DVB streams can be obtained from the website www.dvb-h.org In this project, a tool called „TS reader lite‟ version 2.8.46g [15] has been used to analyze the DVB test streams. TS reader is a transport stream analyzer, decoder, recorder and stream manipulator for MPEG-2 systems. It supports DVB, ATSC, ISDB, and Digicipher® II extensions to the base MPEG-2 specification. TS reader gives the user the big picture overview of what is being carried inside MPEG-2 transport streams and can be very useful for finding errors or inefficiencies. TS reader does not necessarily need hardware to operate and analyze DVB streams. It can run a virtual simulation by taking the transport stream file as an input.Test Stream 1 Figure 8. Test stream 1 [15]Figure 9. Test stream 1 pie chart [15]Test stream 2 Figure 10. Test stream 2 [15]Figure 11. Test stream 2 pie chart [15]DVB-SH systems in the United States The United States currently follows the advanced television systems committee (ATSC) [17] standard for satellite and terrestrial transmission. The telecom operator AT&T has agreed to buy spectrum in the lower 700 MHz frequency band licensed by Qualcomm. [12] Alcatel Lucent has hosted successful trials of DVB-SH systems across the United States. [12] ICO Global Communications has successfully launched a satellite named ICO G1 specifically for mobile television. [12]Figure 12. The ICO G1 system based on DVB-SH system [14] (ATC: ancillary terrestrial component)Future systems using DVB-SH technology Development of interactive TV applications. DVB-SH can be used in intelligent transport services to warn drivers of traffic congestion and alternate route planning. Statistical multiplexing can increase the number of broadcasted TV channels. Remote network monitoring.List of acronnyms CAT: Conditional access table. CGC: Complementary ground components. DVB-SH: Digital video broadcast satellite to handheld. EIT: Event information table. FFT: Fast fourier transform. ISI: Inter-symbol interference. MPE: Multiprotocol encapsulation-forward error correction. MSS: Mobile satellite services. NIT: Network information table. OFDM: Orthogonal frequency division multiplexing. PAT: Program association table. PMT: Program map tables. QAM: Quadrature amplitude modulation. QCIF: Quarter common intermediate
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