DVB-SH System for Broadcasting to Handheld DevicesProject proposal for EE 5359 Multimedia processing, Spring 2011.Guided by Dr. K.R. RaoIrfan Kerawalla ID: 1000719155 [email protected]:To implement the DVB-SH (Digital Video Broadcast - Satellite Services to Handheld Devices) standard designed for transmission of video, audio and data services on mobile devices.Motivation:Mobile TV is expected by many to become one of the next big mass media markets. 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 updates ranging from news to social life on their fingertips. This project is a step towards understanding the process involved inimplementing and delivering quality media content to handheld devices.What is DVB-SH?DVB-SH [1] is the name of a transmission system standard designed to deliver video, audio and data services to vehicles and handheld devices. The key feature of DVB-SH is that it is a hybrid satellite/terrestrial system that allows the use of a satellite to achieve coverage of large regions oreven a whole country. In areas where direct reception of the satellite signal is not possible, a terrestrial gap filler can be used seamlessly to provide coverage. 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]System Architecture:Figure 1 shows the network architecture of the DVB-SH system.TR(a) are broadcast infrastructure transmitters that provide reception in urban areas.TR(b) are personal gap fillers. Their purpose is to provide indoor coverage.TR(c) are mobile broadcast infrastructure transmitters.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-slicingTime slicing is a very important aspect in DVB-H technology. The objective of time-slicing is to reduce the average power consumption of the terminal and enable smooth and seamless service handover. Time-slicing consists of sending data in bursts using significantly higher instantaneousbit rate compared to the bit rate required if the data were transmitted using traditional streaming mechanisms. [8]Time-slicing enables a receiver to stay active only a fraction of the time, while receiving bursts of a requested service. Note that the transmitter is constantly on (i.e. the transmission of the transport stream is not interrupted).Time-slicing also supports the possibility to use the receiver to monitor neighboring cells during the off-times (between bursts). By accomplishing the switching of the reception from one transport stream to another during an off period it is possible to accomplish a quasi-optimum handover decision as well as seamless service handover.Compression in DVB-SHDVB-SH uses H.264/AVC compression standard. The block diagram of H.264 encoder and decoder are given in figure 2 and figure 3 respectively.Band used for DVB-SH transmissionFigure 4. Band used in DVB-SH transmission DVB-SH seeks to exploit the less congested, higher frequency, S-band where there are opportunities for MSS (mobile satellite services) systems, operating in conjunction with CGC (complementary ground components).Typical applications of DVB-SH may include:- 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. UMTS (Universal Mobile Telecommunications System).Figure 5. Conceptual description of a DVB-SH system [11] Figure 6. Conceptual description of a DVB-SH receiver [11]Table 1 gives the frequency domain parameters for the 8-MHz channel. For other bandwidths, simple scaling offers the parameters where narrowing channel bandwidth means increased symbol length. Note that the number of active carriers is smaller than directly proposed by the FFT size. As in DVB-T, this is due to having some guard band with zero amplitude carriers. Table 1. Physical layer parameter and data rates of DVB-SH system [11]Table 2 gives the OFDM symbol lengths in time domain with and without guard intervals. It isworth noting that with the longest guard interval and using 4K mode one can build SFN (singlefrequency network) using up to about 33–35-km transmitter distances. The maximum distanceis dictated by the transmission delay between the transmitter sites. This should be smaller thanthe guard interval length.Table 2. Time domain parameters for DVB-SH OFDM signal [11]DVB-SH systems in the United StatesThe 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]References:[1] ETSI EN 301192: Digital Video Broadcasting (DVB); DVB specification for data broadcasting (DVB-DATA).[2] ETSI TS 102005: Digital Video Broadcasting (DVB); Specification for the use of video and audio coding in DVB services delivered directly over IP.[3] ETSI EN 300468: Digital Video Broadcasting (DVB); Specification for Service Information (SI) in DVB systems (DVB-SI).References [1] [2] and [3] can be accessed from http://www.dvb-h.org [4] DVB BlueBook A079 Rev. 1: IP Datacast over DVB-H: PSI/SI.http://broadcasting.ru/pdf-standard-specifications/internet%20protocol/a079.pdf[5] DVB BlueBook A111: Framing structure, channel coding and modulation for Satellite Services to Handheld devices (SH) below 3GHz.http://www.dvb.org/(RoxenUserID=9b5031601a81d830f6f38d9ed110cb03)/technology/standards/a111_DVB-SH_Specification.pdf[6] DVB-Scene edition No. 21: A New Star in the Sky, by Prof. Dr-Ing. Ulrich Reimers.[7] P. Kelley, C. Rigal, “DVB-SH in S-band” References [6] and [7] can be accessed
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