1. VoIP over Wireless Networks
James Michaels
Jonathan Levitt

2. Introduction Issues with wireless networks:
Inability to provide QoS
Unable to guarantee bandwidth
Determine maximum number of quality VoIP calls over wireless networks

3. Background and Motivation
VoIP(Voice over Internet Protocol)
Routing of voice through any IP-based network
VoIP Components:
Codec converts analog voice to digital data and compresses it
SIP (Session Initiation Protocol) to establish call connection

4. Preliminary Work Equipment: Hardware Software
2 Laptop computers (1 wired, 1 wireless)
1 Router/AP
Software
SJphone
Iperf

5. Preliminary Work
Testbed

6. Results Calls Error % Average Jitter (ms) 2 .12 1.20 3 .11 2.28 4 2.35
3.3
2.41 6
26.8
4.11 7
35.6
9.56 8
55.6
13.14
Calls: SJphone call +
n(Iperf call)
Error % =
100(Packet Loss / Packets Sent)
Average Jitter =
Summation of each Jitter / n(Iperf call)

7. Results
Audio Comparison
1 Call
5 Calls
6 Calls
8 Calls

8. Perceptible, but not annoying
Work To Be Done
MOS (Mean Opinion Score):
Subjective test where listeners rate the quality based on the following scale
MOS
Quality
Impairment 5
Excellent
Imperceptible 4
Good
Perceptible, but not annoying 3
Fair
Slightly annoying 2
Poor
Annoying 1
Bad
Very annoying

9. Work To Be Done R-Factor: Objective call quality measurement
ITU developed E-model
Ranges from (100 = perfect quality)
Score decreases based on amount of delay and equipment impairments
Construct an advance monitoring metric
Develop a program to measure and compare VoIP call quality while increasing the number of calls

10. Summary
VoIP’s call quality diminishes as the number of calls are increased
5 is the maximum number of VoIP calls with less than 3.5% error
Average jitter increases as the number of calls increase
Questions?