This document discusses testing of VOIP call quality over a WiMAX network with and without Quality of Service (QoS). Three VOIP call scenarios were tested: 1) between a WiMAX user and GSM user, 2) between a WiMAX user and fixed user, and 3) between two WiMAX users. Key VOIP quality metrics like packet loss, jitter, delay, and Mean Opinion Score improved significantly with QoS in all scenarios. The greatest improvement was seen when both ends were WiMAX users. Based on these results, the document recommends integrating an Alcatel-Lucent Service Broker to provide dynamic QoS in order to ensure good VOIP call quality as data traffic on the WiMAX network increases

1. VOIP Quality over WIMAX Connection
Mobilink Pakistan
802.16 e (W3 Ed02)
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INDEX
index....................................................................................................................................................2
1. Introduction....................................................................................................................................3
2. VOIP call between wimax user & GSM user......................................................................................4
3. VOIP call between wimax user & Fixed user (PTCL)...........................................................................7
4. VOIP call between 2 different wimax users ....................................................................................10
5. Conclusion ...................................................................................................................................13

3. 1. INTRODUCTION
One of the Most important Business models for the WIMAX 802.16e Solution is the VOIP, and as the
VOIP is a basic requirement in the WIMAX license given by PTA to Mobilink and due to the fact that the
traffic on the WIMAX cells will be a mixture of both Data & VOIP, where data packets will cause Queuing
and consequently delay for the VOIP packets and Jitter (variable delay in the arrival of VOIP packets)
which will all cause a degradation on the Voice quality overseen in the VOIP call, it was mandatory to
have a Mechanism or Algorithm to provide the VOIP traffic with higher QOS or to mark the VOIP
packets (DSCP = 46) rather than the normal Data packets (DSCP = 0) and by this packet Marker
(Diffserv.) the system will identify the VOIP packets and hence will give them Higher QOS in terms of
Delay, dedicated Band Width, jitter threshold, which all contribute to Better VOIP quality.
So Mainly in the next Part of the Report there will be demonstration for VOIP calls with and without QOS
and in both cases measuring the VOIP quality using Call Analyzer Software and the Combinations will be
as follow;
1. WIMAX end user GSM
2. WIMAX end user fixed
3. WIMAX end user WIMAX end user (Mostly Affected by QOS)
The VOIP quality will be checked for the above combinations for both cases with QOS & without QOS.
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4. 2. VOIP CALL BETWEEN WIMAX USER & GSM USER
The VOIP call will be between a WIMAX end user (CPE connected to the WIMAX network) and a user in
the GSM Network.
Measurements Bench Marking for both cases with and without QOS;
Metric Value Without QOS Value With QOS
Received Packets 1760 1890
Lost Packets 2 1
Out of Sequence Packets 0 0
Duped Packets 0 0
Jitter 40 7
Maximum Jitter 73 46
R-Factor 90 91
Mean Opinion Score 4.13672 4.15625
Avg RTT 115 82
Max RTT 136 313
Jitter Buffer Delay (ms) 0 0
Jitter Buffer Packets Dropped 846 1214
Jitter Buffer Out-of-sequence Packets 0 0
SQS Bin 1 (0.5) 856 508
SQS Bin 2 (5) 389 1319
SQS Bin 3 (10) 351 58
SQS Bin 4 (15) 77 0
SQS Bin 5 (20) 78 2
SQS Bin 6 (25) 5 0
SQS Bin 7 (30) 1 0
SQS Bin 8 (35) 0 0
SQS Bin 9 (>35) 0 0
From the Table above the Enhancement in Voice quality parameters is very Obvious (Delay , jitter ,
Packets loss , MOS score & SQS)
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5. The Gain in VOIP quality parameters is
(The –ve percentages are resembling losses)
VOIP quality Parameter QOS Gain (+ve) or Loss (-ve) %
PLR (Packet Loss Rate) -53.44%
Jitter (Average) -36.99%
MOS Score 0.47%
RTT (Round trip time) -28.70%
As appearing above in the Table, the PLR decreased by 53 % and the Jitter decreased by almost 37%
and the delay is decreased by 29% and the MOS score is enhanced by 0.47%
The SQS (stream quality Signature) for the VOIP packets distribution
(Mainly the SQS is showing the Max. variation in the delay of the arrival of packets, the more
contained in the 1st
SQS level, the less variation in Delay of arrival of packets, the better voice
quality)
SQS distribution for VOIP call between WIMAX user & GSM user with no QOS
SQS distribution for VOIP call between WIMAX user & GSM user with QOS
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As appearing from the SQS Graph of Distribution of the no. of VOIP packets in the call, the call with
QOS granted to the wimax end user is having the majority of samples with SQS ranging between (0.5
2) which in the graph resembled by the 1st
two SQS BIN’s.
Coming from the Definition of the SQS parameter as Measure for the variation of delay in arrival of
VOIP packets between Packet number N & Packet number N+1 , it is clear that the less value of SQS
for arriving samples , the better VOIP quality.

7. 3. VOIP CALL BETWEEN WIMAX USER & FIXED USER (PTCL)
The VOIP call will be between a WIMAX end user (CPE connected to the WIMAX network) and a user in
the FIXED Network (PTCL).
Measurements Bench Marking with and without QOS;
Metric Value without QOS Value with QOS
Received Packets 1939 1975
Lost Packets 7 3
Out of Sequence Packets 0 0
Duped Packets 0 0
Jitter 71 63
Maximum Jitter 125 64
R-Factor 85 89
Mean Opinion Score 4.00781 4.11328
Avg RTT 151 124
Max RTT 193 137
Jitter Buffer Delay (ms) 0 0
Jitter Buffer Packets Dropped 814 1024
Jitter Buffer Out-of-sequence Packets 0 0
SQS Bin 1 (0.5) 355 840
SQS Bin 2 (5) 447 948
SQS Bin 3 (10) 475 172
SQS Bin 4 (15) 136 8
SQS Bin 5 (20) 427 3
SQS Bin 6 (25) 44 0
SQS Bin 7 (30) 31 0
SQS Bin 8 (35) 15 1
SQS Bin 9 (>35) 6 0
As appearing from the measurements above in the table, enhancement in all VOICE quality
parameters.
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8. The Gain in VOIP quality parameters is
(The –ve percentages are resembling losses)
VOIP quality Parameter QOS Gain (+ve) or Loss (-ve) %
PLR (Packet Loss Rate) -57.92%
Jitter (Average) -11.27%
MOS Score 2.63%
RTT (Round trip time) -17.88%
As appearing above in the Table, the PLR decreased by 58 % and the Jitter decreased by almost 11 %
and the delay is decreased by 18 % and the MOS score is enhanced by 2.6%
The VOIP Packets distribution with their SQS intervals
(Mainly the SQS is showing the Max. variation in the delay of the arrival of packets, the more
contained in the 1st
SQS level, the less variation in Delay of arrival of packets, the better voice
quality)
SQS distribution for the VOIP packets in WIMAX to Fixed with No QOS
SQS distribution for the VOIP packets in WIMAX to Fixed with QOS
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As appearing from the SQS Graph of Distribution of the no. of VOIP packets in the call, the call with
QOS granted to the wimax end user is having the majority of samples with SQS ranging between (0.5
20) which in the graph resembled by the 1st
two SQS BIN’s.
Coming from the Definition of the SQS parameter as Measure for the variation of delay in arrival of
VOIP packets between Packet number N & Packet number N+1 , it is clear that the less value of SQS
for arriving samples , the better VOIP quality.

10. 4. VOIP CALL BETWEEN 2 DIFFERENT WIMAX USERS
In the next scenario the VOIP call will be established between 2 different WIMAX end users in the
WIMAX Network.
In this Scenario it is expected that the Gain of the QOS and its impact on the Voice quality
parameters will be very high and this is because of the usage of the QOS in both UL & DL paths.
Measurements Bench Marking;
Metric Value without QOS Value with QOS
Received Packets 2036 2125
Lost Packets 7 4
Out of Sequence Packets 0 0
Duped Packets 0 0
Jitter 197 37
Maximum Jitter 296 105
R-Factor 47 89
Mean Opinion Score 2.3125 4.11328
Avg RTT 226 149
Max RTT 281 187
Jitter Buffer Delay (ms) 0 0
Jitter Buffer Packets Dropped 689 767
Jitter Buffer Out-of-sequence Packets 0 0
SQS Bin 1 (0.5) 212 1136
SQS Bin 2 (5) 246 263
SQS Bin 3 (10) 216 20
SQS Bin 4 (15) 143 23
SQS Bin 5 (20) 919 529
SQS Bin 6 (25) 103 150
SQS Bin 7 (30) 30 0
SQS Bin 8 (35) 28 1
SQS Bin 9 (>35) 136 0
As it was expected, the biggest enhancement of all VOIP scenarios in the VOIP quality indicators is
achieved when both ends are WIMAX users.
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11. The Gain in VOIP quality parameters is
(The –ve percentages are resembling losses)
VOIP quality Parameter QOS Gain (+ve) or Loss (-ve) %
PLR (Packet Loss Rate) -45.25%
Jitter (Average) -81.22%
MOS Score 77.87%
RTT (Round trip time) -34.07%
As appearing above in the Table, the PLR decreased by 45.25 % and the Jitter is reduced by 81 %
and the delay is decreased by 34 % and the MOS score is enhanced by 77.87 %
The VOIP Packets distribution with their SQS intervals
(Mainly the SQS is showing the Max. variation in the delay of the arrival of packets, the more
contained in the 1st
SQS level, the less variation in Delay of arrival of packets, the better voice
quality)
SQS packet distribution for WIMAX to WIMAX VOIP call without QOS
SQS packet distribution for WIMAX to WIMAX VOIP call with QOS granted at both ends
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12. As appearing from the SQS Graph of Distribution of the no. of VOIP packets in the call, the call with
QOS granted to the wimax end user is having the majority of samples with SQS ranging between (0.5
25) which in the graph resembled by the 1st
two SQS BIN’s.
Gain = +ve value %
Loss = -ve Value %
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5. CONCLUSION
As mentioned before, According to the User Authentication, the Service profile will be assigned by
the AAA and hence the QOS for the user packets (Data or VOIP) will be considered.
In W3 ed02 the WIMAX Solution for ALU offers different types of Service Profiles & QOS classes as
below;
BE: Best Effort (No QOS granted & the VOIP will be dealt as the data and in this case the VOIP
will be highly affected by the cell traffic load as the more Data packets stream on the cell
Queue will cause directly more delay in the VOIP packets & more jitter)
UGS: Un-solicited Grant Service (divided into VOIP & Leased Line Conservational).
o VOIP: Resembles dynamic QOS where The SBC is used to provide the QOS only for the VOIP
packets for the end user (data for that specific user will be dealt as BE).
o LLC: Resembles Static QOS where No SBC is needed and the user is granted QOS over all
his applications (Data & VOIP).
It is to be noted that the QOS over VOIP is the same between Static & dynamic QOS (no advantage for
one another – will have same QOS) and that’s how the VOIP quality was tested in the WIMAX network
in MOBILINK with No SBC integrated on the Gq interface.
With the increase in the No. of Subscribers in the WIMAX network of Mobilink, the Data traffic will
increase causing Variable delay and queuing in the VOIP packets and thus QOS must be granted for
the VOIP packets over the Data packets.
Static QOS (No SBC integrated) can not be the main key to resolve the issue for good as Mainly this
kind of QOS will be granted for the end user no matter what is the running application (Leased Line –
Same QOS class for both VOIP & Data).
Normally Leased Lines are to be provided at higher rates for corporate end users.
Hence from the above Values enhancement in the VOIP quality Measuring Indicators, it is highly
advised to integrate the ALU SBC (7500) to provide the Dynamic QOS into the WIMAX network in order
to provide VOIP performance un-affected due to traffic load in the cells.
All VOIP scenarios were tested in Good & Medium radio (static & dynamic – up to 50Kmph).
HCA (Hammer Call Analyzer) V1.6 was used to analyze the VOIP parameters, other VOIP Quality tools
can be used for the same task.

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