Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 1 -
Hrvoje Jenkac
Joint Advanced Student School (JASS) 2005
30.03.05 – 10.04.05St. Petersburg, Russia
Reliable Multimedia Broadcast in
Cellular Systems:
Retransmission
and
Fountain Coding Strategies
Reliable Multimedia Broadcast in
Cellular Systems:
Retransmission
and
Fountain Coding Strategies
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 2 -
• MBMS: Motivation and Overview
• Unacknowledged Broadcast Strategies
• Acknowledged Broadcast Strategies
• H. 264 Video over MBMS
• Fountain Coding: The Turbo Fountain
OutlineOutline
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 3 -
• Multimedia Broadcast and Multicast Services (MBMS)
Traffic telematics, weather information, news broadcast,music streaming (web radio) , video concert,
sports replay, file sharing
• Standardization is still ongoing
• All subscribers receive the same content
• Efficient data delivery (common resources)
• Reuse of existing physical layer functionalities
• Sufficient Quality of Service (QoS)
Motivation - Broadcast Services Motivation - Broadcast Services
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 4 -
UnicastUnicast
ContentServer
BTS
MS
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 5 -
Broadcast / Multicast Broadcast / Multicast
ContentServer
BTS
MS
RTP/UDP/IP
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 6 -
Packet Broadcast Packet Broadcast
P1P2P3P4P5
P4
P3
P2
P1
• MSs listen to the same frequency / timeslot / code
• Data transmission downlink only
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 7 -
Dynamics depends on• Receiver velocity• Frequency
Receive Power = 1/T ∫( . )2 dt
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 8 -
time in seconds
C/I
in d
B
Fading Processes Fading Processes
• losses• errors
• losses• errors
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 9 -
Traditional GPRS Protocol Stack Traditional GPRS Protocol Stack
Encoded block Encoded block
Convolutional Encoding Convolutional Encoding
LLC frame
RLC SDUsegment
RLC SDUsegment
RLC SDUsegment
RLC SDUsegment
RLC SDUsegment
RLC dataBH CRC tail RLC dataBH CRC tail RLC dataBH CRC tail
Burst Burst Burst Burst Burst Burst Burst Burst
physic
al la
yer
RLC
/MA
C layer
IP / UDP / RTP headerFH FCS
LLC
layer
ok err
xx
NAL unitx
statistical representation of RLC-SDU segments
statistical representation of RLC-SDU segments
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 10 -
GPRS PerformanceGPRS Performance
50 bytesCS 4
36 bytesCS 3
30 bytesCS 2
20 bytesCS 1
Payload
size
Coding
Scheme
• Performance shown for
1 timeslot
• Packet length S=500
bytes
• Combination of max. 6
timeslots possible
• RLC payload sizes:
CS1 CS2 CS3 CS4
17.5dB
15.0dB
10.0dB
7.5dB
GERAN working assumtion:
required QoS for most multimedia
codecs
Impacts to the broadcast scenario:
� Different loss characteristics for different
receivers
� Worst user C/I=7.5 dB should be supported
Impacts to the broadcast scenario:
� Different loss characteristics for different
receivers
� Worst user C/I=7.5 dB should be supported
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 11 -
IP over Wireless IP over Wireless
PayloadHeader
x xPacket Erasure ChannelPacket Erasure Channel
PayloadHeader x
Tra
nsm
itte
r (B
TS
)R
ece
iver
(MS
)
Segment Segment Segment Segment
Segment Segment SegmentSegment
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 12 -
Packet Erasure Channel Packet Erasure Channel
packet
(segment)
correct reception
erasure
correct reception
erasure
correct reception
erasure
correct reception
erasure
11 p−
1p
21 p−
2p
31 p−
3p
1 Mp−
Mp
MS 1
MS 2
MS 3
MS M
• statistically
independent
packet erasures
• erasure (loss) probability pm
• pm depends on C/I of
MSs and packet size
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 13 -
Transmission Bearer Transmission Bearer
• Unacknowledged Bearer
• best effort delivery
• FEC only
• low delay
• Acknowledged Bearer
• reliable
• lost packets are retransmitted or incremental
redundancy (IR)
• persistent / non-persistent
• increased delay / reduced throughput
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 14 -
• MBMS: Motivation and Overview
• Unacknowledged Broadcast Strategies
• Acknowledged Broadcast Strategies
• H. 264 Video over MBMS
• Fountain Coding: The Turbo Fountain
OutlineOutline
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 15 -
Unacknowledged Bearer Unacknowledged Bearer
Packet Source
Segmentation
Segmentation
PECPEC
SegmentationReassemblyReassembly
PECPEC
Packet SourcePacket
SourcePacket
SourcePacket Sink
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 16 -
Unacknowledged Bearer Unacknowledged Bearer
Packet Source
Segmentation
Segmentation
PECPEC
SegmentationReassemblyReassembly
PECPEC
Packet SourcePacket
SourcePacket
Source
FECFECFECFEC
FEC
Packet Sink
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 17 -
Unacknowledged Bearer Unacknowledged Bearer
Packet Source
Segmentation
Segmentation
PECPEC
SegmentationReassemblyReassembly
PECPEC
Packet SourcePacket
SourcePacket
SourcePacket Sink
FECFECFECFEC
FEC
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 18 -
Simple Solutions Simple Solutions
• Repetition of IP packets
• Located in the BM-SC (Broadcast Multicast Service Center)
• No impact on physical layer
• Fast deployment
• Low complexity
• No changes to BTS
• Repetition of Link Layer Packets
• Located in the RAN
• No impact on the physical layer
• Low complexity
• Small changes at RAN required
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 19 -
BM-SC RepetitionBM-SC Repetition
( )1 1MS
LS mP p
= − −
Ps residual IP-packet error rate
pm segment loss probability
S IP-packet size [byte]
L segment size
8 LZ
T M
⋅=
⋅
SD M T
L
= ⋅
IP Packet
IP Packet IP Packet
IP Packet
IP Packet IP Packet
IP Packet IP Packet
M times repetition M times repetition
Segment Segment Segment Segment Segment Segment Segment Segment Segment Segment Segment Segment Segment Se
M times repetition of media packets
Residual IP-packet error rate: Maximum throughput:Delay:
D delay
M number of repetitions
T packet (transmission) rate [1/s]
S
L
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 20 -
Link Layer Packet RepetitionLink Layer Packet Repetition
( )1 1S
M LSP p = − − 8 LZ
T M
⋅=
⋅
SD M T
L
= ⋅
IP Packet
Segment Segment Segment Segment
Segment Segment Segment Segment Segment Segment Segment Segment Segment Segment Segment Segment
L
S
Ps residual IP-packet error rate
pm segment loss probability
S IP-packet size [byte]
L segment size
Residual IP-packet error rate: Maximum throughput:Delay:
D delay
M number of repetitions
T packet (transmission) rate [1/s]
IP Packet IP Packet IP Packet
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 21 -
Performance Results RepetitionPerformance Results Repetition
0 1 2 3 4 5 6 7 8 9 1010
−4
10−3
10−2
10−1
100
RLC−SDU error rate vs. throughput for TU03, CS4, C/I=7.5 dB, FH=1, and S=500.
Throughput in kbit/s
RLC
−S
DU
err
or
rate
BM−SC CS1RLC CS1BM−SC CS2RLC CS2BM−SC CS3RLC CS3BM−SC CS4RLC CS4
0 1 2 3 4 5 6 7 8 9 1010
−4
10−3
10−2
10−1
100
RLC−SDU error rate vs. throughput for TU03, CS4, C/I=7.5 dB, FH=1, and S=500.
Throughput in kbit/s
RL
C−
SD
U e
rro
r ra
te
BM−SC CS1RLC CS1BM−SC CS2RLC CS2BM−SC CS3RLC CS3BM−SC CS4RLC CS4
RLC frame repetition
IP packet repetition
Combination of 6 timeslots max. throughput approximately 12 kbit/s
Better coding strategies exist than repetition redundancy!
Better coding strategies exist than repetition redundancy!
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 22 -
Video over PECVideo over PEC
0% packet loss
1% packet loss10% packet loss
0.1% packet loss
• 900 frames QCIF (176 x 144)
• H264 encoded
• QP=37, 48 kbit/s
• What is the required residual error rate?
• Each Video Frame is mapped to one IP-packet
• 10 frames/s
• 1 I-frame/s
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 23 -
Outer RS-Coding Outer RS-Coding
IP Packet
Segment Segment Segment
IP Packet IP Packet
k n-k
Segment Segment Segment Segment SegmentSegment Se
IP Packet
Segment Segment Segment Segment Segment SegmentSegment Segment Segment Segment SegmentSegment Se
Segment Segment Segment
byte-wise Reed-Solomon codingbyte-wise Reed-Solomon codingbyte-wise Reed-Solomon codingbyte-wise Reed-Solomon codingbyte-wise Reed-Solomon codingbyte-wise Reed-Solomon coding
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 24 -
Properties of Reed-Solomon Codes Properties of Reed-Solomon Codes
• systematic shortened Reed-Solomon codes defined over GF(2q),
where q is the number of bits per symbol (usually q=8).
• The code is specified by its overall symbol length n and its
information symbol length k, the rate is k/n.
• Any n ≤ 2q-1 and any k ≤ n can be chosen.
• (n,k,q)-RS codes have the following property:
As long as the number of lost symbols (erasures) within one
code word is smaller or equal than n-k, the entire k
information symbols can be reconstructed.
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 25 -
Outer RS-Coding Outer RS-Coding
( )S1
11
nn ii
m mi n k
np i p p
in−
= − +
= − ∑
/S 1 (1 )
S LsP p= − −
8k L MZ
n T
⋅ ⋅= ⋅
( )( )1D n k n Tγ β= + − + +S
Lα
=
1
k
αβ
− =
( )1 modkγ α= −
Symbol (segment) erasure probability after RS decoding:
Residual IP-packet loss rate:
Throughput:
Delay:
Ps residual IP-packet error rate
pm segment loss probability
S IP-packet size [byte]
L segment size
D delay
M number of repetitions
T packet (transmission) rate [1/s]
k/n code rate
Ps residual IP-packet error rate
pm segment loss probability
S IP-packet size [byte]
L segment size
D delay
M number of repetitions
T packet (transmission) rate [1/s]
k/n code rate
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 26 -
Performance of Outer RS CodingPerformance of Outer RS Coding
throughput gain
[Jenkac, Stockhammer, Liebl, Xu, 2004]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 27 -
Performance of Outer RS CodingPerformance of Outer RS Coding
0 500 1000 15000
1000
2000
3000
4000
5000
6000
7000
8000Delay versus RLC−SDU size S
RLC−SDU size S in bytes
De
lay D
in
ms
RLC/MAC rep. CS1, M=5Outer Coding, CS1, n=16, k=8Outer Coding, CS1 n=128, k=98
[Jenkac, Stockhammer, Liebl, Xu, 2004]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 28 -
• MBMS: Motivation and Overview
• Unacknowledged Broadcast Strategies
• Acknowledged Broadcast Strategies
• H. 264 Video over MBMS
• Fountain Coding: The Turbo Fountain
OutlineOutline
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 29 -
Acknowledged Bearer Acknowledged Bearer
Packet Source
Segmentation
Segmentation
PECPEC
SegmentationReassemblyReassembly
PECPEC
Packet SourcePacket
SourcePacket
SourcePacket Sink
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 30 -
Acknowledged Bearer Acknowledged Bearer
Packet Source
Segmentation
Segmentation
PECPEC
SegmentationReassemblyReassembly
PECPEC
Packet SourcePacket
SourcePacket
SourcePacket Sink
ARQARQARQARQ
ARQ
Feedback
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 31 -
Packet Broadcast Packet Broadcast
P1P2P3P4P5
P4
P3
P2
P1
• p-t-M broadcast
• common frequency / time slot / code
• packet losses (PEC)
• different users lose different packets
• Reliable broadcast bearer (ARQ)
• Feedback to transmitter required
• Reliable broadcast bearer (ARQ)
• Feedback to transmitter required
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 32 -
Feedback Channel Feedback Channel
• Ideal feedback scenario
• Separate feedback channels for each receiver
• ACK/NACK indication
• Packet labeling
• Restricted feedback scenario
• Common Feedback Channel
• Only NACK indication
• No packet label information
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 33 -
Common Feedback Channel Common Feedback Channel
• Base station recognizes that at least one of the terminals
needs a retransmission (power measurement)
• As p-t-M retransmissions are performed, it is not of interest
for BS which terminal needs retransmission
• Base station recognizes that at least one of the terminals
needs a retransmission (power measurement)
• As p-t-M retransmissions are performed, it is not of interest
for BS which terminal needs retransmission
Packet reception failed:
• terminals send NAK using a common frequency and time
slotin uplink
• BS receives superposed signal
Packet reception succeeded:
• terminals do not send anything
• Feedback similar to On-Off-Keying
modulation
superposition
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 34 -
BORMAC Feedback ModelBORMAC Feedback Modelf2(t)fM (t)f1(t) F (t)�Binary OR Multiple Access Channel (BORMAC)
• fm(t)=1⇒ receiver m indicates nack
• fm(t)=0⇒ receiver m indicates ack
•Fm(t)=1⇒ at least one receiver indicated nack
• fm(t)=0⇒ no receiver indicated nack
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 35 -
p-t-p Retransmissions p-t-p Retransmissions
P3
P3P4
P2
P1P2P3P4P5
P4
P3
P2
P1
• After the broadcast session M
p-t-p sessions are initiated
• lost packets are requested by the
terminals (ideal feedback scenario)
• p-t-p transmission to each
separate terminal
• each requested packet is utilizing
one frequency and time slot
• parallel transmission to terminals
possible
4 channel accesses required4 channel accesses required
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 36 -
p-t-M Retransmissions p-t-M Retransmissions
P1P2P3P4P5
P4
P3
P2
P1
• lost packets are indicated by
the terminals
• p-t-M re-broadcast to the
terminals
• terminals listen to one
frequency / time slot / code
• identical frames requested by
several terminals only occupy
one radio resource
3 channel accesses required3 channel accesses required
P2
P3
P3P4
P2
P4
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 37 -
1 1 1
1
1 1 101 11
0
101 1
1100
0 10 01 00110
11 1 11 110 1 01 10 010 1 111 0 1 00
XOR
Transmission to user 1
1 01 10 010 1 1?? ? ? ?? 1 0 11001 0
11 1 11 110 1 01 10 010 1 1 0 0 1 0
Message 1 Message 2 Message 3
11 1 11 1101 1
Transmission to user 2
1 0 11001 0
11 1 11 110 1 01 10 010 1 1 0 0 1 0
11 1 11 1101 1 1 1?? ? ? ?? 1 111 0 1 00
NACK
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 38 -
p-t-M ARQ with IR p-t-M ARQ with IR
R1
R1
R2
R2
P1P2P3P4P5
P4
P3
P2
P1
• Incorrect code words are
indicated by terminals
• p-t-M transmission to the
terminals (terminals listen to
one frequency / time slot /
code)
• Incremental redundancy
packets are sent,
• Outer code can recover lost
packets
• Only 2 channel accesses required
• Reduced feedback frequency
• Only 2 channel accesses required
• Reduced feedback frequency
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 39 -
IR with Reed-Solomon Codes IR with Reed-Solomon Codes
Information k symbols Redundancy n-k symbolsChannel
Coding
Puncturing: Puncturing
p symbols
Transmission
(like puncturing):
Decoding 1 failed
→ NAK and IR
Decoding 2 failed
→ NAK and IR
Decoding 3 succ.
→ ACK
Channel
losses
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 40 -
Performance of p-t-M-IR ARQ Performance of p-t-M-IR ARQ
• T is random variable – denoting the number of required
packet broadcasts to deliver data to all users (correctly)
• We are interested in the expected value E{T}
Throughput derivation:
T
1
{ } Pr{ }n
t
E T t T t=
= ⋅ =∑
t
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 41 -
Performance of p-t-M-IRPerformance of p-t-M-IR
( ) ( )
( )
1
1 1 11
0 0
1
0
{ } Pr{ }
11 1 1 1
11 1 1 1
n
t
n k ki it i t i
m m m m
m mt k i i
ki j i
m m
m i
E T t T t
t tt p p p p
i i
j jn p p
i i
=
− − −− − −
= = =
−−
=
= ⋅ =
− = ⋅ − − − − − +
− + − − − − −
∑
∑ ∑ ∑∏ ∏
∑∏ ( )1 1
1
0
1n k
i j i
m m
mj k i
p p− −
− −
= =
− ∑ ∑∏
{ }k
ZE T
=
Throughput: Residual segment error rate:
( ),1
11
nn xx
res m m m
x n k
np x p p
xn
−
= − +
= − ∑
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 42 -
Performance of p-t-M-IRPerformance of p-t-M-IR
0 5 10 15 20 25 30 35 40 45 501
2
3
4
5
6
7
8
number of users M
thro
ughput in
kbit/s
Throughput vs. number of users M, iFH, 7.5 dB, k=12
p−t−p CS1 R=1p−t−M CS1 R=1p−t−M IR CS1 r=1p−t−p CS1 R=2p−t−M CS1 R=2p−t−M IR CS1 r=2p−t−p CS1 R=10p−t−M CS1 R=10p−t−M IR CS1 r=10
p-t-p retransmissions
p-t-M retransmissions
p-t-M-IR ARQ
[Jenkac, Stockhammer, Liebl, Xu, 2004]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 43 -
Performance of p-t-M-IRPerformance of p-t-M-IR
0 200 400 600 800 1000 1200 1400 1600 1800 20000
1
2
3
4
5
6
7
8
number of users M
thro
ughput in
kbit/s
Throughput vs. number of users M, iFH, 7.5 dB, k=12
p−t−p CS1 R=1p−t−M CS1 R=1p−t−M IR CS1 r=1p−t−p CS1 R=2p−t−M CS1 R=2p−t−M IR CS1 r=2p−t−p CS1 R=10p−t−M CS1 R=10p−t−M IR CS1 r=10
p−t−M IR (r=1, r=2, r=10)
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 44 -
Performance of p-t-M-IRPerformance of p-t-M-IR
0 1 2 3 4 5 6 7 8 9 1010
−10
10−9
10−8
10−7
10−6
10−5
10−4
10−3
10−2
10−1
100
Residual RLC frame error rate 7.5 dB, k=12
number of retransmissions R / average number of redundancy packets r
RL
C f
ram
e e
rro
r ra
te
p−t−p CS1p−t−M CS1p−t−M IR CS1
p-t-p retransmissions
p-t-M retransmissions
p-t-M-IR ARQ
[Jenkac, Stockhammer, Liebl, Xu, 2004]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 45 -
Performance 10 dB Performance 10 dB GERAN parameters:
• CS1 (L=20 byte)
• C/I = 10 dB (p=0.03)
• 1 time-slot
[Jenkac, Stockhammer, Liebl, Xu, 2004]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 46 -
Residual IP-Loss Rate Residual IP-Loss Rate GERAN parameters:
• CS1 (L=20 byte)
• C/I = 7.5 dB (p=0.2)
• 1 time-slot
[Jenkac, Stockhammer, Liebl, Xu, 2004]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 47 -
Conclusions: Transmission BearersConclusions: Transmission Bearers• Only FEC with Reed-Solomon Codes is suitable to define
an appropriate unacknowledged mode bearer for
broadcast in cellular environments.
• For reliable services feedback from the receivers to the
transmitter is required.
• ARQ combined with incremental redundancy performs
excellent in broadcast environment with feedback.
• Degeneration of p-t-M-IR ARQ with increasing number of
users is minimal compared to other schemes.
• Current work: Closer investigation of the common
feedback channel
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 48 -
• MBMS: Motivation and Overview
• Unacknowledged Broadcast Strategies
• Acknowledged Broadcast Strategies
• H. 264 Video over MBMS
• Fountain Coding: The Turbo Fountain
OutlineOutline
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 49 -
� World cup 2006 in Germany: “A time to make friends”
� But how can we provide football to everyone, on the road, in or nearby the stadium, etc.?
� The idea: A video broadcast service on top of existing cellular systems, name it:
� Multimedia Broadcast and Multicast Services
� How can video transmission be accomplished in this scenario?
� Use the best available video coder H.264/AVC
� Use GSM/GERAN with no or little modifications
� Adaptation of the video application!
�What is the achievable Video Quality?
Motivation Video over MBMSMotivation Video over MBMS
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 50 -
H.264/AVC and NALH.264/AVC and NALH.264 Conceptual Layering
Transport Layer
Network AbstractionLayer Encoder
Network AbstractionLayer Decoder
H.264 to
H.320
H.264 to
MPEG-2
Systems
H.264 to
H.324/MH.264 to
RTP/IP
H.264 to
ISO
file format
NAL Decoder InterfaceNAL Encoder Interface
Wireless Networks
VCL-NAL Interface
Video Coding LayerEncoder
Video Coding LayerDecoder
Wired NetworksBroadcast Networks
Video Coding LayerEncoder
Video Coding LayerDecoder
slices
NAL units
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 51 -
� GPRS parameters:
� TU03 (3km/h pedestrian user)
� Fixed coding scheme CS1
� combination of 6 downlink time-slots, 48 kbit/s max. throughput
� H.264/AVC parameters:
� static parameters for all simulations:
� Foreman (QCIF), 7.5 fps
� I-frames every 10 sec
� no B-frames (IPPPP…)
� variable parameters:
Parameters – Experimental Setup Parameters – Experimental Setup
Expected loss rate in RaDiOMacroblock Mode Selection
PNALU
Max. NAL unit length (slice length)
NNALU
Header overhead (RTP/UDP/IP)
Total bit-rate including headers
HRv
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 52 -
� Video encoding without channel aware macroblock selection (only I-frames every 10 sec)
� GPRS system unmodified, broadcast mode
� Performance at C/I=7.5dB (worst user to be supported)
Non-optimized approach Non-optimized approach
0%
PNALU
= frame size
NNALU
40 bytes48000 bit/s
HRv
0%
PNALU
50 bytes
NNALU
40 bytes48000 bit/s
HRv
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 53 -
Optimized H.264 over GPRS Optimized H.264 over GPRS � Video encoding optimized on
packet loss rate of worst user to be supported in the cell (C/I = 7.5 dB)
� rate-distortion optimization
� GPRS system unmodified
40%
PNALU
50 bytes
NNALU
40 bytes48000 bit/s
HRv
40%
PNALU
50 bytes
NNALU
40 bytes48000 bit/s
HRv
Worst user to b
e supported
=> => ModificationsModifications
to GSM GPRSto GSM GPRS
areare necessarynecessary forfor
sufficientsufficient QoSQoS of of
videovideo
[Jenkac, Stockhammer, Liebl, Xu, 2004]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 54 -
H.264 over UNAK-MBMS H.264 over UNAK-MBMS � UNACK bearer for MBMS based
on RS coding on RLC layer
� Reduction of loss rate:
37875
bit/s
36000
bit/s
48000
bit/s
throughput
0.02%
(128,101)
0.03%
(64,48)
11%RLC/MAC block loss rate @ 7.5dB
no coding (GPRS)
(n,k)-RS code
0%
PNALU
300 bytes
NNALU
40 bytes36000 bit/s
HRv
40%
PNALU
50 bytes
NNALU
40 bytes48000 bit/s
HRv⇒⇒ RelativelyRelatively lowlow
complexitycomplexity
⇒⇒ Little Little changeschangesin in thethe systemsystem
⇒⇒ reasonablereasonablequalityquality
[Jenkac, Stockhammer, Liebl, Xu, 2004]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 55 -
H.264 over ACK-MBMSH.264 over ACK-MBMS� ACK bearer with feedback and
retransmissions
� No. of users infl. throughput
0%
PNALU
300 bytes
NNALU
40 bytes36000 bit/s
HRv
0%
PNALU
=frame size
NNALU
40 bytes36000 bit/s
HRv
39300 bit/s
40500 bit/s
Throughput,
k=128
0%
U=50
0%
U=10
RLC/MAC block
loss rate @ 7.5dB
No. of users
⇒⇒ HigherHighercomplexitycomplexity
⇒⇒ SignificantSignificantchangeschanges areare
necessarynecessary
⇒⇒ Good Good qualityquality
[Jenkac, Stockhammer, Liebl, Xu, 2004]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 56 -
� RTP/UDP/IP header H=40 bytes
� Compressed RTP/UDP/IP header H=5 bytes on average
� More bitrate for error resilience features and video coding
� PSNR results outperform system without HC, but only slight
� Robust header compression was assumed
Header Compression (HC) Header Compression (HC)
⇒⇒ Slight improvements with HC.Slight improvements with HC.
[Jenkac, Stockhammer, Liebl, Xu, 2004]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 57 -
� In UNACK and ACK mode increase in C/I did not results in increased PSNR performance.
� Support of worst case user results in fixing the code rate.
� Outer coding provides flexibility to adapt coding rate:
� relaxed worst case user
assumption
� change in user topology
� increased throughput
� Significant gains
Adaptation to User Topology Adaptation to User Topology
0%
PNALU
=frame size
NNALU
40 bytes70848 bit/s
HRv
[Jenkac, Stockhammer, Liebl, Xu, 2004]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 58 -
� The traditional GPRS in combination with non-optimized
and optimized H264/AVC cannot provide sufficient QoS.
� Modification at wireless network required.
� Enormous gains in PSNR and perceptual quality with RS outer coding and optimized video.
� Header compression slightly improves system
performance.
� Exploitation of feedback (ACK) does not provide huge
gains for video delivery compared to UNACK mode.
� Flexible coding allows adaptation to changing user
topology. Additional gains in video quality can be
achieved.
Conclusions: H.264 over MBMSConclusions: H.264 over MBMS
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 59 -
• MBMS: Motivation and Overview
• Unacknowledged Broadcast Strategies
• Acknowledged Broadcast Strategies
• H. 264 Video over MBMS
• Fountain Coding: The Turbo Fountain
OutlineOutline
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 60 -
Broadcast without FeedbackBroadcast without Feedback
ContentServer
BTS
MS
Download and Play Service
� No feedback channels
� Asynchronous data access
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 61 -
Asynchronous Data Access Asynchronous Data Access
� Users enter asynchronously into serving area
� All users get same content (e.g. location based information like traffic control or restaurant information)
Scenario: Highway with many expected users
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 62 -
Fountain CodesFountain Codes� Information message u of finite size k symbols
� Fountain encoder produces an infinite number (n→∞) of code symbols x = F (u)
� Infinite redundancy: “rateless”
� Ideal Fountain code (erasure channel):
� No restriction on number of information symbols k
(large messages can be encoded without separation)
� MDS property: Any k out of n→∞ are sufficient to reconstruct the information message
� Never-ending redundancy like never ending water in a fountain.
Information k symbols Redundancy (n-k)→∞
[Bayers, Luby, Mitzenmacher, 2002]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 63 -
Ideal Fountain Code Ideal Fountain Code Continuous broadcast as long as
receivers are present and unsatisfied
Erased packet
RX 1
RX 2
RX 3
RX 4
TX
Parity packetSystematic packet No transmission
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 64 -
Water Fountain vs. Digital Fountain Water Fountain vs. Digital Fountain
Fountain Code
� Person wants to fill up a cup with water
� Many persons can fill a cup with water at same time (broadcast).
� It does not matter which drops fill the cup, but only how many
� Asynchronous start of water reception possible
� Receivers want to receive messages from a transmitter
� Many receivers are able to receive at the same time
� It does not matter which symbols are received, but only how many
� Asynchronous start of download possible
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 65 -
Example: Reed-Solomon Coding Example: Reed-Solomon Coding
Information k symbols Redundancy n-k symbols
max. n-k erasures can be corrected
Information length is restricted to k
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 66 -
Coupon Collector problem Coupon Collector problem
Information k symbols Redundancy n-k symbols
File length 2k
Information k symbols Redundancy n-k symbols
ok
lost
Entire file data can not be reconstructed, though number of erasures is less than 2(n-k).
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 67 -
Generalization:
Ideal erasure fountain code:
Fountain Codes: Formalization Fountain Codes: Formalization
r = [ 1 01 1 1 1 1 1
1
111 1
1 1 1 1 1 1
1
1
1 1 1 1 1 1
1 1 1
1
1 1 1 1
1 1 1 1 1 111
1 0 0 …. ]
0 0 0 …. ]
0 0 0 0
00
0 0
0 0 … … 0
0 …. ]
0 .. ]
r = [
r = [
r = [
{ }1: ( )I IF F k−
≡ ∀ ≥x' u x'
1: ( )S S
kF F
C
− ≡ ∀ ≥
x' u x'
x' ≜ Number un-erased and un-punctured symbols
Number of un-punctured symbols x' ≜
Capacity achieving fountain code:
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 68 -
Ideal Fountain Approximations Ideal Fountain Approximations
� Unfortunately, fountain codes with optimal MDS property were notfound yet. Seems infeasible.
� Practical solutions have decoding inefficiency, i.e., k ’=(1+ε)k, with ε->0, symbols on average have to be received.
� Practical Fountain Codes:
� Data Carousel
� Data Carousel coded with RS-codes
� Tornado Codes (LDPC like)
� LT Codes (Luby Transform) (= randomly encoded LDGM Code)
� Raptor Codes (LT Code + accumulating)
� Turbo Fountain (TF)
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 69 -
Turbo Fountain: ConceptTurbo Fountain: Concept
� Infinite redundancy by applying turbo codes
� Ideally, all parity bits are independent
� using many different component codes
� interleave symbols randomly after encoding
� Decoding: exchange of extrinsic information
� Achieve gains by exploiting soft information
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 70 -
Multiple Turbo-FountainMultiple Turbo-Fountain
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 71 -
Parallel TF - EncodingParallel TF - Encoding
� parallel Concatenated Turbo Code produces T(u)
� T(u) randomly interleaved by random interleavers
� produced infinite redundancy
� Interleaved repetition structure
� for practical puncturing behavior sufficient
Parallel Turbo Fountain Encoder F
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 72 -
The Parallel TF - DecodingThe Parallel TF - Decoding
� Distribution of incoming bits
� y’ obtained by Soft Combining
� Decoding decision: Hard decision of the turbo decoder output L(u’)
Parallel Turbo Fountain Decoder F -1
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 73 -
Decoding Multiple Turbo CodesDecoding Multiple Turbo Codes
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 74 -
The Multiple TF - DecodingThe Multiple TF - Decoding
Multiple Turbo Fountain Decoder F -1
L(x’)
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 75 -
Simulation SetupSimulation Setup
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 76 -
Ideal Erasure Based
Fountain Code, R=1
Ideal Erasure Based
Fountain Code, R=1/2
Capacity Achieving
Fountain Code
Parallel TF, R=1
Parallel TF, R=1/2
Simulation ResultsSimulation Results
receiv
er
thro
ughput
ES/N0 in dB
AWGN – K=16000 Bit – L=160 Bit
Multiple TF, R=1
[Jenkac, Hagenauer, Mayer, 2005]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 77 -
Simulation Results (2)Simulation Results (2)
Ideal Erasure Based
Fountain Code, R=1
Ideal Erasure Based
Fountain Code, R=1/2
Ideal Erasure Based
Fountain Code, R=1
Capacity Achieving
Fountain Code
Ideal Erasure Based
Fountain Code, R=1/2
Ideal Erasure Based
Fountain Code, R=1
Parallel TF, R=1
Ideal Erasure Based Fountain Code, R=1/2
Capacity Achieving
Fountain Code
Ideal Erasure Based
Fountain Code, R=1
Ideal Erasure Based
Fountain Code, R=1
Ideal Erasure Based
Fountain Code, R=1/2
Capacity Achieving
Fountain Code
Parallel TF, R=1
Parallel TF, R=1/2
Ideal Erasure Based
Fountain Code, R=1
Ideal Erasure Based
Fountain Code, R=1/2
Capacity Achieving
Fountain Code
Parallel TF, R=1
Parallel TF, R=1/2
Multiple TF, R=1
receiv
er
thro
ughput
ES/N0 in dB
Fast Fading – K=16000 Bit – L=160 Bit
[Jenkac, Hagenauer, Mayer, 2005]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 78 -
Simulation Results (3)Simulation Results (3)
Ideal Erasure Based
Fountain Code, R=1
Ideal Erasure Based
Fountain Code, R=1Ideal Erasure Based
Fountain Code, R=1/2
Ideal Erasure Based
Fountain Code, R=1Ideal Erasure Based
Fountain Code, R=1/2
Capacity Achieving
Fountain Code
Ideal Erasure Based
Fountain Code, R=1Ideal Erasure Based
Fountain Code, R=1/2
Capacity Achieving
Fountain Code
Parallel TF, R=1
Ideal Erasure Based
Fountain Code, R=1Ideal Erasure Based
Fountain Code, R=1/2
Capacity Achieving
Fountain Code
Parallel TF, R=1
Parallel TF, R=1/2
Ideal Erasure Based
Fountain Code, R=1Ideal Erasure Based
Fountain Code, R=1/2
Capacity Achieving
Fountain Code
Parallel TF, R=1
Multiple TF, R=1
Parallel TF, R=1/2
receiv
er
thro
ughput
ES/N0 in dB
Block Fading – K=16000 Bit – L=160 Bit
[Jenkac, Hagenauer, Mayer, 2005]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 79 -
Combined Source-Fountain CodingCombined Source-Fountain Coding
Pr{ u = +1} = p
Pr{ u = -1} =1 - p
Source State Information
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 80 -
Simulation Results (4)Simulation Results (4)
[Dütsch, Jenkac, Hagenauer, Mayer, 2005]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 81 -
Simulation Results (5)Simulation Results (5)[Dütsch, Jenkac, Hagenauer, Mayer, 2005]
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 82 -
Conclusions: Turbo-FountainConclusions: Turbo-Fountain
� Fountain codes solve the reliable broadcast problem with
asynchronous data access.
� No feedback channels are required.
� Digital Fountain approximation based on turbo codes :
The Turbo Fountain (TF)
� Significant gains by exploiting soft information.
� Interleaved repetition structure based on a rate 1/3 turbo-code, approximates a digital fountain very well.
� Combined Source-Channel-Fountain Coding.
� Future work: close remaining gap to capacity.
Technische Universität München (TUM)
Lehrstuhl für Nachrichtentechnik (LNT)
Prof. Dr.-Ing. Joachim Hagenauer
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005
Reliable Multimedia Broadcast in Cellular Systems
H. Jenkac, JASS, St. Petersburg, 4/2005- 83 -
Thank you
for your attention!
Thank you
for your attention!
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