[Dipl.-Ing. T. Jäkel, DiBroC]
- What is DVB-H?
- Related Standards
- Main Features DVB-H
- Time Slicing
- Improved Bit Error Ratio (BER)
- Application and Services
- Recommendations
| 1. What is DVB-H?
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- DVB-H stands for mobile reception of data via DVB-T (H means Handheld, recently called DVB-X or DVB-M)
- DVB-H is based on DVB-T, 'only' the higher layers are modified (TS, DSM/CC, MPE)
- The lower layers of DVB-T are reused and compatible, a simultaneous operation of DVB-T (TV service) and DVB-H (data service) in one multiplex is possible
- Transmission of data mainly as IP frames (Internet Protocol)
- As data high compressed video (H.264, similar to MPEG-4), with lower bitrate compared to MPEG-2 (instead 3-4 MBit/s approx. 384 KBit/s per each stream)
- Trimmed for the mobile reception on handheld devices (battery power save, screen resolution)
- Additional error correction for reliable transmission and reception with complicated conditions (movement, small antennas)
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| 2. Related Standards
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- EN 203 304, DVB TM 2977 (DVB-H)
- A079 (TM 3025 Rev. 1)
- DVB TM 3037 (DVB-H)
- A081 (TM 3037)
- Draft TM 2977 r3
- EN 301 192 (Time Slicing, MPE-FEC)
- ISO/IEC 13818-6 (DSM/CC, MPE)
- ISO/IEC 13818-6 (DSM/CC, MPE)
- TS 101 190 (DVB-T, TPS)
- TS 101 191 (SFN, TPS)
- EN 300 744 (DVB-T)
- EN 300 468 (DVB-SI)
- H.264
- A080 (I_MT)
- (FLUTE/ALC)
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| 3. Main Features DVB-H
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- Time Slicing
block oriented transmission of date (bursts), sleep mode of receivers, relative time information instead MAC addresses
- MPE-FEC
additional Reed Solomon code on MPE level used for the data (IP frames), increased C/N value for poor reception
- 4k mode
compromise between 2k (mobile reception) and 8k (large SFN networks)
- Signaling
extended signaling (modified TPS bits and additional MPEG tables - INT), handover support
- 5 MHz bandwidth
a smaller spectrum bandwidth in mind to support wireless telecom channels
- Non-broadcast channels
Not only used in common used broadcast (TV) channels (VHF, UHF), also for non-broadcast frequencies
- IP V6
the new IP version 6 protocol (and UDP) is used to transmit data, IP in DSM/CC, MPE
- H.264
Video is coded as H.264/AVC (Advanced Video Codec)
- FLUTE
New protocol for data carousels (file transfer)
- I_MT
Interface for service and applications as well as return channels based on wireless communication channels (GSM, UMTS)
- MMP
The extension and reuse of the Multimedia Home Platform (MHP) comes in mind as Mobile Media Platform (open service and application interface)
- In-Depth-Interleaver
OFDM symbol interleaver for 8k (memory size) is used to doubled or for-times interleaving in 4k or 2k mode
- Mandatory Cell_ID
The Cell_ID has to be set and transmitted now in DVB-H networks (cell identification and handover)
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| 4. Time Slicing
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The data of DVB-H services are transmitted as time slices in order to save the battery power of small handheld devices. Instead to be 'always on' the receiver can use a sleep mode because it is informed when the next data burst will be available.
In comparison to Digital TV services where the video and audio is delivered as continuous packet stream the entire bitrate of the transport stream is utilized as slots with variable parameters.
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| 5. Improved Bit Error Ratio (BER)
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Handheld receivers have to cope with two problems: small antennas and fast movement. Although DVB-T supports a very robust reception even during movement DVB-H needs additional improvements to compensate bit errors and to increase the speed when DVB-H is used to bring services into cars or trains. The doppler shift, means the maximum speed on what the reception of services will be available, can be increased by an additional protection level: the MPE Forward Error Correction (FEC). Therefore DVB-H provides a better Carrier to Noise value, at least increased by 3 dB, because of the additional check sums for IP datagrams which allow to correct corrupted data packets.
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| 6. Application and Services
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- Video Streaming, not TV-like (CIF size screens), short video infotainment, advertisement, gaming, e.g. During World Soccer Championship 2006 in Germany
- Mobile information service, music portals and video clips, web based applications (using Rich Media, XML)
- DVB-H remains "One-To-Many" (broadcast oriented)
- Perhaps not as Free-To-Air (FTA) service but very cost effective in comparison to UMTS
- Return channels and service interworking (billing, accounting) based on wireless communication (GSM, UMTS)
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| 7. Recommendations
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- Modulation:
16QAM (eventually 64QAM) FEC: 1/2 and 2/3 (16QAM with 1/2 better than QPSK with 3/4) GI: 2k: 1/4
4k: 1/4, 1/8
8k: 1/4, 1/8
- CIF (360 x 288) at 384 Kbit/s H.264 video streams
- Total bandwidth: 10 - 15 Mbit/s (up to 35 streams)
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