WAP Downlink Performance Evaluation in UMTS
Network
Author: Pertti Hakkarainen
Supervisor: Prof. Jorma Virtamo
Instructors: MSc Jani Kokkonen, Dr Samuli Aalto
Work was carried out: Nokia Networks, Espoo
Thesis number: 1033 – 2004
Presentation date: November 9, 2004
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WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
HELSINKI UNIVERSITY OF TECHNOLOGY
Table of contents
• Introduction
• Research Problem
• WAP
• Wireless TCP/IP
• Measurement Setup
• Measurement Results
• Conclusion
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WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
HELSINKI UNIVERSITY OF TECHNOLOGY
Introduction
• The study is the downlink performance measurement in the Universal
Mobile Telecommunication Services (UMTS) network
• Technical specification of the network is based on 3rd Generation
Partnership Project (3GPP) Release 99
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WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
HELSINKI UNIVERSITY OF TECHNOLOGY
Research Problem
• The object of this study is to compare the download performance of the
Wireless Application Protocol (WAP) and TCP/IP protocol WAP applications
in the 3G network.
• The protocols are designed for different network domains
• WAP protocol stack for circuit switched networks where the bandwidth is
relatively low
• TCP/IP protocols for packet switched networks where the bandwidth is
considerably higher
• The aim of this work is to study how well different protocols can utilize the
performance of the 3G network.
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WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
HELSINKI UNIVERSITY OF TECHNOLOGY
WAP 1/2
Why WAP?
• The WAP specification is designed to bring Internet access to the wireless
environment.
• Wireless data networks present a more constrained communication environment
compared to wired networks.
• Handheld wireless devices present a more constrained computing environment
compared to desktop computers (CPU, memory, power supply, display, keypad
etc.).
• WAP-compatible component communicate with all other components in the solution
network by using the standard methods and protocols defined in the WAP
specification
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WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
HELSINKI UNIVERSITY OF TECHNOLOGY
WAP 2/2
WAP version 1.2
WAP version 2.0
•
WAP 1.2 is based on WAP protocols
•
WAP 2.0 is based on TCP/IP
•
WAP gateway makes the conversion from text
to binary and vice versa
•
WAP Gateway is acting as a WAP 2.0 proxy
•
No security gap, security is comparable to the
Internet model – transaction all the way from
WAP Device to the Web server will be secured
•
The plain text headers of HTTP are translated
into binary code that significantly reduces the
amount of data that must be transmitted over
the air interface.
•
Complete end-to-end security cannot be
guaranteed due to a security gap in the GW
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WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
HELSINKI UNIVERSITY OF TECHNOLOGY
Wireless TCP/IP
• The Transmission Control Protocol/Internet Protocol (TCP/IP) forms the basis of the
Internet. Originally it is designed and optimized to provide reliable byte transfer with
retransmission in a terrestrial environment where conditions are relatively stable
compared to the wireless environment. The assumption is that a packet loss is due
to congestion in the network.
• The wireless networks have brought new aspects to the packet loss.
• More narrow and variable bandwidth
• Higher bit error rate
• More latency
• More transmission delay
• Less connection stability
• Less predictable availability
• Since TCP/IP operates over different kinds of link conditions, from stable and fast
wireline links to delay sensitive wireless links, there may be situations that
performance degrades due to the fact that the optimization is done in a different way
on different parts of the network and packet delays that are treated as congestion
• wireless TCP/IP provides the same functions as the “normal” TCP/IP with some
optimization in the protocols
• The round-trip time (RTT) is one of the most essential issues that has affected to
wireless TCP optimization.
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WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
HELSINKI UNIVERSITY OF TECHNOLOGY
Measurement setup 1/2
• The target of the measurement has been to measure WAP throughput with different
WAP versions, WAP 1.2 and WAP 2.0, to the download direction and evaluate that
network is capable to carry traffic with nominal throughputs.
• Tools
• Ostrich is a trace interface adapter device that provides mechanisms for
buffering the tracing and debugging data sent by the phone.
• EARP is a PC application for decoding and logging trace data during the testing
and debugging of user equipment.
• Measurement is carried out in the Nokia WCDMA test network.
• During the measurement there were not other traffic in the network
Test network setup
UE
Gateway
Iub
EARP
Ostrich
BS
Iu-PS
RNC
Gn
Gi
3G SGSN 3G GGSN
Firewall
Switch
RTT
Content
Server
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WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
HELSINKI UNIVERSITY OF TECHNOLOGY
Measurement setup 2/2
• Measurement was conducted with 13 different file sizes, ranging from 2
kilobytes to 160 kilobytes
• Downlink rates are 64 kbps, 128 kbps and 384 kbps, for uplink 3G
Partnership Project Release 99 defines 64 kbps
• Used phones
• Nokia 6650 for WAP protocol measurement
• Nokia 7600 for TCP/IP measurement
Nokia 6650
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WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
Nokia 7600
HELSINKI UNIVERSITY OF TECHNOLOGY
Measurement results 1/4
• WAP 1.2 used segmentation and reassembly (SAR) value of 5
• SAR defines a method for a WAP gateway to break a large message into small
chunks (the segmentation) and for the phone to piece it back together (the
reassembly)
• SAR requires the UE to acknowledge to the WAP gateway after every fifth
packet
• Operator controlled value and optional
Handshake packets
• The measurement starts when the user has selected the file for download and
presses the button on the phone in order to receive it. The connection for the
download is already created.
• The measurement stops at the reception of the last octet of the file.
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WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
HELSINKI UNIVERSITY OF TECHNOLOGY
Measurement results 2/4
• Calculation for average and maximum download throughput
• Average throughput is the download period from the very first octet of the file
until the last octet of a particular file is received including the slow start
• The maximum throughput calculation is done over the stabilized transfer part of
the download (figure)
Steady transfer part
of the connection
Handshake packets
• WAP protocol has the segment size of 1412 bytes => 7060 bytes requires ACK
• In TCP/IP the Maximum Segment Size (MSS) is 1460 bytes and UE allows 20
segments per window
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WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
HELSINKI UNIVERSITY OF TECHNOLOGY
Measurement results 3/4
• WAP 1.2 shows quite poor download utilization in 3G network
• The reason is SAR value that requires UE to acknowledge to the gateway
• If SAR is not used and there is failure in transmission, the whole file must be
retransmitted, the bigger the file is the more retransmission deteriorates the
throughput
Max. WAP 1.2 throughput
Nominal bit rate
kilo bits/s
64
128
384
kilo bits/s
41.613
54.654
97.172
kilo bytes/s
5.080
6.672
11.862
Utilization
65.0%
42.7%
25.3%
• WAP 1.2 designed for circuit switched environment and hence it can not utilize the
packet switched environment features
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WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
HELSINKI UNIVERSITY OF TECHNOLOGY
Measurement results 4/4
•
Wireless TCP/IP utilizes the link connection pretty well, the ’pipe’ fill is optimal
•
Wireless TCP/IP is designed for the packet switched environment
Max. WAP 2.0 throughput
Nominal bit rate
kilobits/s
13
64
128
384
kilobits/s
63.650
125.095
375.694
kilobytes/s
7.770
15.271
45.861
Utilization
99%
98%
98%
•
For small packets the WAP 1.2 throughput is better than WAP 2.0 throughput
•
When using the SAR value five in WAP 1.2, the better throughput in favor of WAP 2.0 happens
between 7 and 10 kilobytes
WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
HELSINKI UNIVERSITY OF TECHNOLOGY
Average throughputs
• Average throughput remains below the maximum throughput
WAP 1.2 average throughputs for different
bearer rates
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WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
WAP 2.0 average throughputs for different
bearer rates
HELSINKI UNIVERSITY OF TECHNOLOGY
Conclusion
• What we found out in our measurement?
• The WAP protocol is beneficial when a small amount of data is downloaded,
less than 10 kilobytes
• For larger file size wireless TCP gains better performance
• The proportion of the slow start from whole downloaded data on the time
scale decreases as the file size grows
• The transition in favor of wireless TCP depends on the algorithms and
parameters used in both protocols
• In our measurement, the wireless TCP gained better download performance
around 10 kilobytes file
• The 3G network is mature to achieve and maintain nominal transfer rates
with WAP applications when using WAP 2.0 in stable environment
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WAP Downlink Performance Evaluation in UMTS Network / 09-11-2004 / Pertti Hakkarainen
HELSINKI UNIVERSITY OF TECHNOLOGY