digital video broadcasting for handheld devices(dvb-h) sahar aghayan 6592207 [email protected]
TRANSCRIPT
Digital video Broadcasting(DVB)
Digital video Broadcasting(DVB)
Digital Video Broadcasting-Satellite(DVB-S): In DVB-S, the signal is broadcasted
through the satellite.
Digital Video Broadcasting-Cable(DVB-C): In DVB-C, the signal is broadcasted
through the broadband coaxial cable.
Digital Video Broadcasting-Terrestrial(DVB-T): In DVB-T, the signal transmitted
using terrestrial methods.
Digital Video Broadcasting-Handheld(DVB-H): In DVB-H, the broadcast services
are given to the mobile handsets.
DVB-T
• Terrestrial Digital Television Standard
– Used in 36 countries world wide
• One-to-many broadband wireless data transport
• Developed for MPEG-2 stream distribution, but can basically carry any data
• DVB-T includes hierarchical modes where two transport streams can be sent
simultaneously
DVB-H
• Digital Video Broadcasting—Handheld (DVB-H) standard is based on
the earlier standard DVB-T, which is used for terrestrial digital TV broadcasting.
• It Brings features that make it possible to receive digital video broadcast type services in handheld, mobile terminals.
DVB-HA full DVB-H system is defined by combining elements in the physical and link layers as
well as service information. DVB-H makes use of the following technology elements for the link layer and the physical layer:
• Link layer:
time-slicing -To reduce the average power consumption of the terminal
- smooth and seamless frequency handover; forward error correction for multiprotocol encapsulated data (MPE-FEC)
- improvement in C/N-performance and Doppler performance in mobile channels
- improving tolerance to impulse interference.
DVB-H• Physical layer:
DVB-H signalling in the TPS(Transmission Parameter Signalling)-bits
- enhance and speed up service discovery
- Cell identifier is also carried on TPS-bits to support quicker signal scan and
frequency handover on mobile receivers 4K-mode
- for trading off mobility and SFN(Single Frequency Network) cell size,
- allowing single antenna reception in medium SFNs at very high speed, adding thus flexibility in the network design;
in-depth symbol interleaver for the 2K and 4K-modes
- for further improving their robustness in mobile environment and impulse noise conditions.
DVB-H Reciever
DVB-H:Time Slicing• Reduce the average power consumption of the terminal (up to about 90%–95%)• Enable smooth and seamless service handover. • Sending data in bursts • On and Off time(Power safe Mode)• Possibility to monitor neighbouring cells during the off-times• Transmitter is constantly on• Mandatory in DVB-H.
Time between the bursts gives the power saving (off time)Time
Ba
nd
wid
th
TS bitrate
Time sliced:
•Service 1
•Service 2
•Service 3
1 1 1 1 2222 333
4
Not timesliced:
•Service 4
• IP encapsulation allows sending the data in bursts to the mobile station and this saves energy (battery power)
• Power consumption and handover
– Handover possible during off time (services can be used even if the terminal has moved during off time)
Power consumption and handover
IP packets in DVB-H
• DVB system can be used for transmission of IP packets. This is done by
Multiprotocol Encapsulation (MPE)
• DVB-H uses exclusively IP packets for media transfer
Multiprotocol Encapsulation
IP packets are embedded into MPE sections which are put into TS
packets
DVB-H:MPE-FEC• FEC for multiprotocol encapsulated data (MPE-FEC)
gives an improvement in carrier-to-noise (C/N) performance
and Doppler performance in mobile channels • Immunity to impulse interference.• By adding parity information calculated from the datagram and sending them in
separate MPE-FEC section, error-free datagrams can be output from MPE-FEC decoding despite a very bad reception condition
• MPE-FEC is optional
MPE-FEC frame structure
DVB-H: in-depth interleaver
• Interleaving is a technique where sequential data words or packets are spread across several transmitted data bursts. In this way, if one transmitted burst or group is lost as a result of noise or some other drop-out, then only a small proportion of the data in each original word or packet is lost and it can be reconstructed using the error detection and correction techniques employed.
• Using the in-depth interleaver enables the noise resilience performance of the 2K and 4K modes to be brought up to the performance of the 8K mode and it also improves the robustness of the reception of the transmissions in a mobile environment.
Conclusion
• features/pros Cost efficient delivery of broadcast content to a large audience Low time to market Low complexity Flexible transport stream sharing between DVB-T and DVB-H possible Based on DVB-T with minimal changes Fulfils most commercial requirements Allows seamless handover No adverse effect on DVB-T
Conclusion(2)
• DVB-H features/cons
o Only IP based services possibleo Reduced power saving when total bit rate for DVB-H services is very low (no
big “bursts” possible)(Max 2Mb)
Question1.
• DVB-H, as a transmission standard uses a power-saving algorithm(Time-slicing)
based on the time-multiplexed transmission of different services. With considering
20 services to be transmitted and The MPEG-2 TS have a bitrate of 10 Mb/s. How
much would be the off-time for a receiver in DVB-H? Compare the situation for
DVB-T?
• (Note :the Maximum burst value is 2 MB)
Q1.Aswer:
In time-slicing IP-services within a MPE data service are organised:
• One service will use the full DVB-H data capacity for a while, say 200 ms(burst time).
• After that comes the next service and so on…
• After longer period, say 4s, the first service is again in the air.
• Ott-time=relative time difference between two consecutive bursts of the same service
On Off
Q1.Answer
•In normal DVB-T MPEG-2 and data transmissions the transport streams from the services are multiplexed together with high frequency on the TS-packet level.
•This means that the services are transmitted practically in parallel.
• For a DVB-T receiver it is impossible to receive only the wanted TS-packets due to the high multiplexing rate. All data must be received -> high power consumption.
Channel Capacity
time
• Adding 4K transmission mode in DVB-H aims to offer an additional trade-off
between Single Frequency Network (SFN) cell size and mobile reception
performance. Please explain in detail the terms of this trade-off compare to 2k
and 8K mode?
Question2.
Q2. Answer
• 8K mode can be used both for single transmitter operation and for small,
medium and large SFNs. It provides a Doppler tolerance allowing high speed
reception.
• 4K mode can be used both for single transmitter operation and for small and
medium SFNs. It provides a Doppler tolerance allowing very high speed
reception.
• 2K mode is suitable for single transmitter operation and for small SFNs with
limited transmitter distances. It provides a Doppler tolerance allowing
extremely high speed reception.
suppose we have the following four bytes of data: D1=10100101,
D2=11110000, D3= 00111100, and D4=10111001,
a) Calculate the parity data.
b) Suppose we have received D1, D2, and D4 at the receiver. How we
can retrieve D3 data?
Question3.
• HINT
Parity information calculated from the block of data can be used to reconstruct the block of data in the event of data loss or failure.
The parity calculation is typically performed using a logical operation called "exclusive OR" or "XOR“
Given Property "A XOR B XOR B = A"
Q3. Answer
A) Answer
D1 XOR D2 XOR D3 XOR D4= ( (D1 XOR D2) XOR D3) XOR D4= ( (10100101 XOR 11110000) XOR 00111100) XOR 10111001= (01010101.XOR 00111100) XOR 10111001= 01101001 XOR 10111001= 11010000
b) Answer
D1 XOR D2 XOR D4 XOR DP= ( (D1 XOR D2) XOR D4) XOR DP= ( (10100101 XOR 11110000) XOR 10111001) XOR 11010000= (01010101 XOR 10111001) XOR 11010000= 11101100 XOR 11010000= 00111100
Q3. Answer
Thank You
Any Question!