Quality of Service Analysis of
Real Time Applications in Ad Hoc
Networks
Mohammad Ayyash
Supervisor: Prof. Raimo Kantola
Nov 2006
Networking laboratory
Table of Contents
•
•
•
•
•
•
•
•
Introduction
Objectives
Steps
Real Time Audio management
VoIP Software Client
Testing
Results
Future Work
Nov 2006
Networking laboratory
Introduction
• Voice over IP (VoIP) is telephone over
packet switched networks.
• The future of voice communications.
• Utilizes the existing wide deployment of
the Internet.
• Can be applied to any packet switched
network. WLAN is an example.
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Networking laboratory
Objectives
• Perform real time audio conversations
over an ad hoc WLAN network.
• Record the Quality of Service (QoS)
factors.
• Compare between the two ad hoc routing
protocols families: proactive routing
(OLSR) and reactive routing (AODV
Nov 2006
Networking laboratory
Steps
• Design and Implement a VoIP software
client.
• Test cases are designed and executed:
– The effect of increasing number of hops.
– The effect of the type of intermediate nodes.
– The effect of network topology change.
• Every test case is executed for AODV and
OLSR.
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Networking laboratory
VoIP protocols
• Signaling: Session Initiation Protocol (SIP)
• Media Transport: Realtime Transport
Protocol (RTP)
VoIP Software
RTP/SIP
• Routing: OLSR and AODV
UDP/TCP
• Network Transport: IP
IP
• MAC: 802.11b
Link Layer
Physical
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Networking laboratory
IP
UDP
VoIP protocols
RTP
GSM Packet
33 Bytes
s
tes byte
y
8 b r 12
0b
r
2
e
r
de
ad
de
a
e
a
e
He
P H TP H
D
P
I
U
R
s
yte
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GSM Packet
33 Bytes
GSM Packet
33 Bytes
userA
userB
userA
SIP
userB
userA
userB
INVITE
INVITE
INVITE
180 RINGING
180 RINGING
180 RINGING
200 OK
486 BUSY HERE
CANCEL
ACK
ACK
ACK
Busy Callee
Rejected call
RTP Session
Successful call setup
BYE
userA
userB
200 OK
Ending call
MESSAGE
MESSAGE
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Networking laboratory
RTP
RTP header
32 bytes
GSM audio frame
33 bytes
GSM audio frame
33 bytes
GSM audio frame
33 bytes
RTP Header
0
V P X CC
8
M PT
16
24
Sequence Number
Time stamp
Synchronization Source identifier (SSRC)
Contributing source identifier (CSRC)
Refer to RFC 1889 [5] for detailed explanation of header fields
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Networking laboratory
324
OLSR vs AODV
OLSR
AODV
• Proactive
• + up-to-date topology
• + smaller packets
• - need larger memory
• - bandwidth overhead
• Reactive
• + less bandwidth usage.
• + less complex
• - Larger packets
• - slower route descovery
• Ad hoc networks topology is dynamic with changing topology.
• AODV has higher cost of initial link establishment. (File sharing)
• OLSR has higher share of bandwidth. (Chatting)
• VoIP tolerates initial link establishment (AODV), but need fast reestablishment (OLSR)
Nov 2006
Networking laboratory
Audio basics
• Audio is sampled at 8000 Hz sampling
rate and 16 bits per sample
• GSM Codec is used.
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260 bytes uncompress audio.
Every 20 msec.
13 bit per sample.
Rate: 104 kbps.
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GSM Codec
Networking laboratory
·
·
·
33 bytes of compress audio.
Every 20 msec.
Rate: 13.2 kbps.
Delay Budget
• ITU-T recommends the delay budget to be
under 150 msec, but not more than 400
msec
End To End Delay
Sender Processing
Time
Transmission Delay
Recording
Transmission
Processing
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Receiver
Processing
Time
Buffering
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Playback
Processing
Time
Realtime audio Management
yb
ac
k
Additional delay
Pl
a
ng
di
Buffer Empty
Se
n
Sequence Number
Original delay
Enough packets in buffer,
resume playback
Time
Buffer is emptying
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Stop and buffer
(Audio playback pause)
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Quality factors
•
•
•
•
•
Packet loss.
Jitter.
End to End delay.
Out of order packet delivery.
Routing Protocol.
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Networking laboratory
VoIP Software client
SIP Component
SIP Parser
Audio Component
RTP Component
JRTP Lib
Nov 2006
GSM Codec
Networking laboratory
Logging
Component
Testing
• 3 major test cases:
– Effect of number of hops
– Effect of intermediate node type
– Effect of topology change.
Nov 2006
Networking laboratory
Test Bed Environment
• 4 iPAQs running Familiar linux, and
equipped with CompactFlash WLAN
802.11b cards, operating at 2.457GHz
11Mbps.
• 2 Laptops, running Fedora Core Linux.
Both are Intel Centrino 1.6 GHz, 512 MB
RAM and Intel PRO Wireless 2200 BG.
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Networking laboratory
Environment Difficulties
• Unstable iPAQs. Unstable CompactFlash
cards.
• Noisy WLAN environment (all channels!)
• iPAQs clocks are not fixed (software
clocks). No time reference.
• Topology re-discovered 50’s of times
during a test case!
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Networking laboratory
Test Case Example
Inter-arrival (Jitter) Distribution
Inter-arrival (Jitter)
Interarrival (Jitter) Distribution
Interarrival (Jitter)
250
0.8
0.7
Highest peak
around 66 msec
200
0.6
150
0.5
0.4
100
0.3
50
0.2
0.1
0
0
0
1145205460
1145205480
1145205500
1145205520
1145205540
1145205560
1145205580
1145205600
-50
-0.1
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Networking laboratory
0.05
0.1
0.15
0.2
0.25
Test Case Example (Cont.)
End to End Delay.
End to End Delay distribution
Delay
End to End Delay Distribution
400
40
350
35
30
300
25
250
20
200
15
150
10
100
5
50
0
50
0
1145205460
100
-5
1145205480
1145205500
1145205520
Network Delay
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1145205540
End to End Delay
1145205560
1145205580
1145205600
Total Processing Delay
Networking laboratory
150
200
250
300
350
400
450
Test Case Example (Cont.)
All values in msec
End to
Delay
Average
187
Std deviation
90% percentile
End Network
Delay
Processing
Delay
Inter-arrival time
169
17
61
37
36
12
43
244
226
36
106
Packet loss (packet)
16
Re-establish time (second)
15
Protocol overhead (packets)
286 / 7969 = 3%
Protocol overhead (bytes)
21220 / 1222673 = 1.73%
Average packet size
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RTP (byte/packet)
OLSR (byte/packet)
153
74
Networking laboratory
Results – Test Case 1
• OLSR has less average end to end delay,
but wider delay distribution.
• AODV has higher processing demand.
• OLSR needs more time re-discovering a
broken link.
• AODV has higher bandwidth share. (but
unstable test bed environment)
Nov 2006
Networking laboratory
Results – Test Case 2
• Using powerful intermediate nodes will
reduce the network delay, and eventually
the end to end delay.
• Using powerful intermediate nodes means
larger scale ad hoc network.
Nov 2006
Networking laboratory
Results – Test case 3
• OLSR requires more processing power
when discovering an alternate route.
• AODV consumes more share of the
bandwidth.
• Both protocols discover the new route
after almost the same delay.
• AODV adds an additional end to end delay
after discovery!
Nov 2006
Networking laboratory
Future Work
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Testing on a larger scale Ad Hoc network.
Testing other routing protocols.
Using other audio codecs.
Including video.
Conference calls.
Distributed SIP infrastructure for ad hoc
networks.
Nov 2006
Networking laboratory