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Performance Evaluation of IEEE 802.16 WiMAX Link With Respect to Higher Layer Protocols



The WiMAX technology based on the IEEE802.16-d standard is a broadband wireless access (BWA) technology and considered to be an important ingredient of the composition of the next generation networks (NGN). Till date, due to lack of deployment, not enough data is available in terms of its operational capabilities and efficiencies. The main objective of this paper is to evaluate, analyze and compare the performance of a WiMAX link under different load and traffic conditions. For this purpose an experimental WiMAX test-bed has been deployed at the Communication Network Institute (CNI), University Dortmund and several experiments and stress tests are carried out over this CNI WiMAX test-bed in the uplink and downlink directions for various service and traffic types and at various distances from the base station. The results of these experiments are presented in this paper.
Performance Evaluation of IEEE 802.16 WiMAX
Link With Respect to Higher Layer Protocols
Faqir Zarrar Yousaf
, Kai Daniel
, Christian Wietfeld
Communication Networks Institute, University of Dortmund
Otto-Hahn-Strasse 6, 44227 Dortmund, Germany
Abstract—The WiMAX technology based on the IEEE802.16-d
standard is a Broadband Wireless Access (BWA) technology and
considered to be an important ingredient of the composition of
the Next Generation Networks (NGN). Till date, due to lack
of deployment not enough data is available in terms of its
operational capabilities and efficiencies.
The main objective of this paper is to evaluate, analyze and
compare the performance of a WiMAX link under different load
and traffic conditions. For this purpose an experimental WiMAX
test-bed has been deployed at the Communication Network
Institute (CNI), University Dortmund and several experiments
and stress tests are carried out over this CNI WiMAX test-bed
in the uplink and downlink directions for various service and
traffic types and at various distances from the Base station. The
results of these experiments are presented in this paper.
Index Terms—WiMAX, IEEE 802.16-2004, experiments, field
tests, measurements
WiMAX was formally introduced in 2004, with the pub-
lishing of the IEEE 802.16-2004 standard [1], which specifies
the air interface, including the medium access control (MAC)
layer and multiple physical (PHY) layer specifications for
Fixed Broadband Wireless Access (FBWA) systems support-
ing not only higher data rates over larger geographical areas
but also claiming QoS support capability matching its wired
counterparts. WiMAX is a wireless alternative to wired Cable
and DSL technology for last-mile solutions and a Wireless
Metropolitan Area (WMAN) solution for providing backhaul
services by aggregating traffic emanating from various other
wireless hotspots, thereby filling in the gap between the high
data rates but small area of coverage provided by wireless
LAN (WLAN) and high-mobility and large area of coverage
but lower data rate support provided by cellular technologies.
Due to lack of deployment not enough information is
available that would provide quantitative and qualitative data
in terms of the performance and operational capabilities of
the WiMAX link, that could be used as a benchmark by
telecommunication engineers and researchers to develop accu-
rate mathematical and simulation models that could compare
more realistically to the actual performance behavior of the
WiMAX link, and thereby develop and recommend better and
efficient algorithms and solutions in terms of Next Generation
Wireless Access Networks. This lack of real empirical data
was the main motivation behind conducting field experiments
over an actual 3.5 GHz WiMAX test-bed established at Com-
munication Networks Institute (CNI), University of Dortmund
to better understand the performance of the WiMAX link in
terms of data throughput and link stability versus distance.
Although some performance data is available but that is
mostly based on analytical and/or simulation models [2].
Also some experimental results are provided in [3], but the
experiments were conducted by emulating the WiMAX link
using different channel models. The experiments performed in
[3] were conducted with multirate support enabled in which
the Subscriber Station (SS) is allowed to choose a specific
modulation scheme according to its SNR and the experiments
were conducted for a limited range of modulation schemes.
There is no mention of the transmit power of the base station
or the type of the antennas used, a factor crucial to the
correct understanding of the system’s scope, and the maximum
distance over which the tests were conducted was around 3000
meters (around 2 miles).
In our experiments, the multi-rate support was disabled to
correctly ascertain the throughput and link quality of each of
the eight available modulation schemes (please see table 1)
over distances ranging from 220 meters to 9400 meters (9.4
km) with minimum transmit power of 13dBm from the base
station (BS). The link was tested for both the TCP and UDP
data in both uplink and downlink direction, thereby providing
data relating to a case of real customer deployment.
In terms of testing the QoS support in WiMAX, exper-
imental measurements have been made in [4] targeting the
residential broadband access scenario, in which multiple sub-
scriber stations (SS), each having the same QoS configuration,
communicate with a single base station in a point to multi-
point (PMP) configuration. In our tests we have targeted a
SOHO/SME broadband access scenario in which a single SS
will be providing services to hundreds of users and/or multiple
departments, each with a possibly unique QoS requirements,
in a Virtual LAN (VLAN) configuration environment, where
subscribers sharing the same QoS class are mapped onto the
same service pipe, a virtual connection between a subscriber’s
application and the network resources, over the WiMAX link.
IEEE International Symposium on Wireless Communication Systems, Trondheim, 2007
Micro Base Station
Client 1:
Traffic Generator
Client 2:
SU & AU Configuration
d (0.4, 5.4, 9.4 km)
Fig. 1. Measurement Setup
For the field experiments an IEEE 802.16d [1] compliant
Alvarion’s BreezeMax equipment operating in a 3.5 GHz
licensed band was selected. As the WiMAX link is tested
in terms of its capacity and its ability to provide QoS to
multiple simultaneous applications services, two different test
beds were composed and configured. Both the test beds had
the same generic setup as shown in figure 1 but differed in
terms of the equipment configuration.
On the subscriber side, the Client1 laptop is used for
generating user traffic in the uplink direction and captures
and analyses data in the downlink direction whereas client2
laptop is running scripts for remote access and configuration
of the WiMAX base station (AU-IDU) and the Customer
Premises Equipment (CPE) (SU-IDU). The two client laptops
and the Subscriber Unit Indoor Unit (SU-IDU) are connected
via an Ethernet Interface (Ieth) to the VLAN switch, where the
VLAN feature is disabled except for the QoS testing, described
later. The SU-IDU in turn is connected to the Subscriber
Unit Outdoor Unit (SU-ODU), which is a vertically polarized
directional antenna with an 18dBi gain.
On the base station side, the Server is used for generating
traffic in the downlink, over the LUT (Link Under Test), and
capturing and analyzing data in the uplink. The Access Unit
Indoor Unit (AU-IDU) is connected via an IF cable (Iradio)
to the Access Unit Outdoor Unit (AU-ODU), which consists
of a 10.5 dBi gain omni-directional antenna and a high-power,
full-duplex multi-carrier radio unit. The AU-IDU consists of
two RJ45 ports namely; management port and data port, for
micro base station remote configuration and the latter for data
communication. These two ports are connected to the Server
via Ethernet. The detailed radio specifications of the IDU and
the ODU is given in table I.
The tests were divided into two categories: Link Capac-
ity/Throughput Testing, in which the ability, reliability and the
robustness of the WiMAX link was tested in both the uplink
and downlink direction for all eight modulation schemes by
transmitting TCP and UDP traffic and real time video streams
at different distances from the BS, and QoS Testing, in which
the inherent QoS support feature of the WiMAX was tested.
To attain reliable results with an appreciable level of
confidence, each test run was conducted ten times and the
duration of each test run was 60 seconds, accounting to a
Frequency Uplink (MHz) Downlink (MHz)
AU-ODU 3399,5 - 3453,5 3499,5 - 3553,5
SU-ODU 3399,5 - 3500 3499,5 - 3600
Ch. Bandwidth 3,5 MHz
Operation Mode AU-ODU FDD, Full Duplex
SU-ODU FDD, Half Duplex
Modulation OFDM Modulation, 256 FFT points;
TX Power AU 13 dBm (20 mW) -
28 dBm (631 mW)
SU 20 dBm (100 mW)
Bit Rate Modulation Net Physical
and Coding Bit Rate (Mbps)
BPSK 1/2 1,41
BPSK 3/4 2,12
QPSK 1/2 2,82
QPSK 3/4 4,23
QAM16 1/2 5,64
QAM16 3/4 8,47
QAM64 2/3 11,29
QAM64 3/4 12,71
Fig. 2. Test Locations
total approximate test duration of 260 minutes excluding the
time for initializing the test scripts and making necessary
configurations on the equipment. The throuput of the uplink
and the downlink were measured seperately in order to exclude
interference effects.
The amount of traffic generated was always equal to the
net physical data rate for each respective modulation scheme
(see table 1) and corresponding packet losses were obviously
measured. The link capacity was tested for both Line Of Sight
(LOS) and Near-LOS scenarios, but Non-LOS (NLOS) was
not possible. The CPE were stationed away from the BS at
the following distances and locations:
d = 220 meters; North Campus, University Dortmund
d = 5400 meters (5.4 km); Auf dem Schnee, Dortmund.
LOS (Figure 2(a))
d = 9400 meters (9.4 km); Radiotower Schwerte, Dort-
mund. Near-LOS (Figure 2(b))
Table 2 summarizes the relevant test configuration of the
To stress-test the link the transmit power of the AU was
set to the minimum of 13 dB and the Automatic Transmit
Power Control (ATPC) feature was enabled for the SU and AU.
Although the maximum transmit power of the BS is 28dBm
(6.918 Watts EIRP incl. 10.5dBi antenna gain), but the limit
Multi Rate Support (BS) Disable
ATPC Support (BS) Enable
TX Power (at BS antenna port) Minimum = 13 dBm (20mW)
Maximum = 20 dBm (100mW)
TX Frequency (BS) Downlink: 3501.25 MHz
Uplink: 3401.25 MHz
VLAN support Yes
QoS Profile Real Time (RT), Non Real
Time (NRT), Best Effort (BE)
of 20dBm (1.096 Watts EIRP incl. 10.5dBi antenna gain) was
imposed by the terms and conditions of the 3.5GHz research
As a QoS-Profile a non real-time setting with a Committed
Information Rate (CIR) of 12Mbps is chosen.
The Multirate support in the AU was disabled, as mentioned
earlier, in order to set the modulation scheme manually for
each measurement to validate the link behavior for each
specific modulation scheme.
The outdoor tests were carried out by mounting the antenna
on the roof of a car and powering the whole SU by a portable
DC to AC power supply, which also powers the switch and
the client PC.
A. Uplink and Downlink Test Configurations
For both the uplink and downlink tests, TCP and UDP traffic
was generated using IPerf [5], which reported bandwidth,
delay jitter and datagram loss, and captured on the receiver
end by Ethereal [6] to capture and analyze the received
data. In case of uplink capacity tests, the Client1 runs the
IPerf server instance whereas the Server runs the IPerf client
instance and Ethereal application and this arrangement is
reversed for the downlink capacity tests. The Client2 machine
is used primarily to manage and configure the AU remotely
by establishing an SSH session and is also used to monitor the
configuration and connection statistics of the SU (for example,
RSSI, SNR, Modulation scheme, transmit and receive power
level of the SU). This automatic management, configuration
and monitoring of the AU and the SU is controlled by a custom
Perl Test Processing scripts.
The captured data is then fed to the custom Perl Test Pro-
cessing scripts where it is analysed for various parameters and
mean values are calculated. The results are then graphically
depicted using the GNU-Plot application.
B. QoS Test Configurations:
In order to test the inherent ability of the WiMAX protocol
to support QoS over the broadband wireless links the general
set up is the same as in figure 1 with the exception that
the VLAN feature in the switch is now enabled and the
two client machines (client 1 and client 2) are placed in
two separate VLANs. Client1 is generating UDP traffic with
transmission parameters emulating a real time VoIP service,
whereas Client2 is generating TCP traffic streams emulating a
non-real time service application such as HTTP etc. The two
VLANs are mapped onto two different service pipes, where
the service pipe designated to carry the real time applicaiton
data is configured with a Real Time Polling Services (rtPS)
service class and the second service pipe carrying the non-real
time application data is configured with a Best Effort (BE)
service class. The two clients generate simultaneous traffic
using the QAM64 3/4 modulation scheme over the maximum
bandwidth of the link so that the effect of these two interfering
traffic streams over the QoS enabled WiMAX link can be duly
This section will provide the measurement results for the
test configurations discussed above and also discuss the effect
of transmit power on the overall link quality.
A. Throughput Tests
Table III shows the TCP and UDP average throughput mea-
sured, which can be compared to the net physical bit rates for
the corresponding modulation scheme given in table I, for the
eight modulation schemes at reference distances of 220 meters,
5400 meters and 9400 meters and the transmit power was set
at a constant minimum of 13dBm. In the downlink direction
Downlink Throughput in Mbps
Modulation 220 meters 5400 meters 9400 meters
BPSK 1/2 1.08 1.13 1.08 1.12 1.08 1.12
BPSK 3/4 1.65 1.74 1.64 1.73 1.65 1.73
QPSK 1/2 2.21 2.32 2.20 2.32 2.20 2.32
QPSK 3/4 3.37 3.53 3.35 3.53 3.35 3.53
QAM16 1/2 4.50 4.74 4.48 4.73 4.48 4.74
QAM16 3/4 6.80 7.11 6.41 7.11 6.41 7.10
QAM64 2/3 8.88 9.40 8.31 9.51 8.31 9.51
QAM64 3/4 9.58 10.55 8.34 10.71 8.34 10.69
Uplink Throughput in Mbps
Modulation 220 meters 5400 meters 9400 meters
BPSK 1/2 0.98 0.98 0.97 1.03 0.97 1.03
BPSK 3/4 1.51 1.54 1.46 1.57 1.50 1.58
QPSK 1/2 2.03 2.14 2.03 2.13 2.03 2.14
QPSK 3/4 3.09 3.24 3.08 3.23 3.08 3.23
QAM16 1/2 4.16 4.33 4.14 4.33 4.14 4.33
QAM16 3/4 6.24 6.52 6.22 6.52 6.22 6.52
QAM64 2/3 8.28 8.67 8.22 8.64 8.25 8.65
QAM64 3/4 9.25 9.67 9.22 9.69 9.22 9.67
(see figure 3) TCP throughput remains almost stable but shows
greater inconsistency especially at higher modulation schemes
(QAM64). It has been experimentally verified and observed
that the TCP throughput stability is dependent on distance and
transmit power. In terms of distance, the higher modulation
schemes shows greater consistency at 220 meters (figure 3
(a)) than at 5400m (figure 3 (b))or 9400m (figure 3 (c)). The
effect of transmit power on the TCP downlink throughput is
subsequently discussed. The TCP throughput in the uplink
direction is more stable at all the three reference distances and
0 5 10 15 20 25 30 35 40 45 50 55 60
(a) TCP Downlinkatd=220m
0 5 10 15 20 25 30 35 40 45 50 55 60
(b) TCP Downlinkatd=5400m
0 5 10 15 20 25 30 35 40 45 50 55 60
(c) TCP Downlinkatd=9400m
Fig. 3. TCP Downlink Throughput at d = (a)220m, (b)5.4km, (c) 9.4km
for all the modulation schemes and is similar, in performance,
to figure 3 (a).
In contrast to TCP downlink traffic, UDP has shown more
throughput stability for all the modulation schemes in both the
uplink and downlink direction at all three reference distances
and the stability in throughput is similar to figure 3 (a)). The
average UDP throughputs is given in table III.
B. QoS Tests
To test the QoS support, every test was conducted by send-
ing TCP background traffic through a non real-time connection
at full capacity of the bandwidth throughout the duration of
the test. A 12 Mbps UDP traffic is sent in periodic durations of
10 seconds through a real-time connection with a committed
bit rate of 5 Mbps and 10 Mbps the result of which is shown
in figure 4.
It is evident that the TCP background traffic will occupy
only that portion of the bandwidth which is not utilized
by the UDP traffic and upon greater demand for bandwidth
by the real-time traffic, the system ensures the guaranteed
provisioning of the demanded bandwidth by claiming it from
non-real time traffic, which in turn will experience bandwidth
reduction, and this behavior is consistent with the overall QoS
Fig. 4. QoS Measurement with (a) 5Mbps and (b) 10Mbps UDP traffic and
TCP Background Traffic
C. Effects of the Distance and Power Control Level on the
As the link was stress tested by keeping the transmit power
of the base station to the minimum value of 13dBm at all
distances and for all tests, in order to evaluate the effect of
0 5 10 15 20 25 30 35 40 45 50 55 60
TCP Uplinkatd=9400m
Fig. 5. Effect of Transmit Power
transmit power on the overall link quality, a second set of tests
at 20dBm transmit power was carried at d=9400m by transmit-
ting TCP traffic in the downlink direction using QAM64 3/4,
as that was more critical in terms of throughput stability (see
figure 3(c)) . As seen in figure 5, there is marked improvement
in terms of link and throughput stability, especially for TCP
traffic, which earlier had shown considerable instability.
With the results gained from this pilot project, and
within the given limits, resources and distance limitations
the WiMAX test arrangement, the field tests conducted at
the CNI’s WiMAX test bed can be regarded as meeting
the functional specification and requirements of a wireless
broadband access network as per the IEEE 802.16-d standard.
The measurements and results gathered through stress testing
the WiMAX link demonstrates satisfactory throughput and
level of services at different distances for both LOS and
Near-LOS, even at the lowest transmission power (13dBm)
at distances as far as 9.4km. One important observation is
that Non Line of Sight (NLOS) operation is not possible and
the correct operation depends on the accurate adjustment of
the CPE in order to get the best possible receive signal. It
has been observed that even one centimeter change of the
vertical or horizontal orientation could have a strong influence
on the RSSI and the SNR and with this the quality of the link,
adversely affecting the throughput.
Considerable degradation of service was observed during
adverse weather conditions, such as during rain fall, resulting
in delay, jitter and inconsistent service due to packet losses.
Such weather conditions will prohibit the use of bandwidth
intensive streaming multimedia services over the WiMAX link.
As part of the future work, more field tests are being
planned at distances beyond 9.4 km and by introducing a
second SS. More tests with the TCP traffic in the downlink
direction will be conducted so as to be able to make precise
recommendations for TCP settings when operating over a
WiMAX link.
Further investigation into the effect of transmit power on
the link throughput and extensive testing of the QoS feature is
also planned, particularly in terms of interference of different
traffic types through traffic flow using all available service
classes simultaneously.
The authors wishes to acknowledge Mr. Christian Mueller
for his efforts and technical assistance in conducting these
[1] IEEE 802.16-2004, “IEEE standard for Local and Metropolitan Area
Networks — Part 16: Air Interface for Fixed Broadband Wireless Access
Systems”, October 2004.
[2] Christian Hoymann, Analysis and performance evaluation of the
OFDM-based metropolitan area network IEEE 802.16”,The International
Journal of Computer and Telecommunications Networking ,Volume 49
, Issue 3, October 2005
[3] Schwengler, T. Pendharkar, N., “Testing of fixed broadband wireless
systems at 5.8 GHz”,Technical, Professional and Student Development
Workshop, 2005 IEEE Region 5 and IEEE Denver Section.
[4] Francesco De Pellegrinin et al, “QoS Support in WiMAX Networks:
Issues and Experimental Measurements”, Create-Net Technical Report
N.200600009, June 16, 2006.
[5] IPerf. [Online]. Available:
[6] Ethereal. [Online]. Available:
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In the last few years, there has been an increasing awareness of the need to evaluate new mobile applications and protocols in realistic wireless settings, and platforms such as the GENI WiMAX testbeds have been developed to fulfill this need. However, wireless testbed users have experienced frustration when straightforward usage scenarios do not consistently agree with the high data rates that are advertised by the wireless technology. This work seeks to clarify the performance characteristics of two GENI WiMAX testbeds under various wireless signal conditions and network traffic patterns. By measuring the performance of several popular wireless Internet applications in two very different wireless environments, we gain a deeper understanding of how a researcher may expect the GENI WiMAX platform to behave. Our findings include some counterintuitive results, e.g. that increasing signal quality can reduce application throughput, and that applications using a single TCP flow may achieve as much as 72% less throughput than an application in an identical setting that uses multiple TCP flows. With this work, we hope to help other researchers design realistic experiments on wireless Internet systems, understand the perceived shortcomings of the GENI WiMAX platform, and interpret their experimental results in the context of the wireless setting in which the experiment was conducted.
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This paper addresses aspects of design and planning of a WiMAX Wireless networks to establish a point-to-point, PTP, link from the Health Sciences Faculty of University of Beira Interior (FCS/UBI) to Hospital Sousa Martins (Guarda), and also presents a field trial with pre-WiMAX PTP equipment. The design of the link had into consideration the carrier to noise ratio, C/N, and the minimum carrier to noise ratio with fading, C/N min_fad . The use of relays is needed to guarantee LoS conditions. The use of BreezeNET B equipment from Alvarion was assumed. From the dimensioning process, it was verified that with γ = 2, for the second clause, the three types of modulations can be used. Field trials results were compared with the theoretical model, and very similar conclusions were achieved. PTM field trials are also being performed in the licensed bands.
Wireless last mile technology is becoming a challenging competitor to conventional wired last mile access systems like DSL and cable modems or even fiber-optic cables. The Institute of Electrical and Electronics Engineers has developed a standard for fixed broadband wireless access systems namely IEEE 802.16. Its OFDM mode targets frequency bands below 11 GHz.This paper gives an overview of the OFDM-based transmission mode of the IEEE 802.16 standard. The medium access control (MAC) and the physical layer are described in detail. Especially the MAC frame structure is elaborated. An analytical performance evaluation of an example scenario is performed which results in overall system performance measures. Especially the interaction of fragmentation and padding of OFDM symbols and its effect on the system capacity is evaluated. Furthermore, different MAC layer configurations with different levels of robustness are analyzed. Optional features to resist challenging channel conditions are outlined. Their trade off, i.e., a reduced MAC layer capacity is pointed out. It is shown that the system can be optimized while maintaining the necessary robustness against environmental challenges. A prototypical IEEE 802.16 protocol stack including a sophisticated channel model has been implemented. By means of this stochastic event-driven computer simulator, downlink and uplink delay as well as throughput evaluation is performed. Thus, performance results based on meaningful MAC configuration examples are provided. Simulative and analytical results are compared.
Conference Paper
ABSTRACT Among several first mile solutions proposed so far, the key advan- tage of the IEEE 802.16 standard, widely known as WiMAX, is to ensure large area coverage and rather inexpensive equipment,at the subscriber side. Modern requirements to wireless connectivity include mandatory,QoS guarantees for a wide set of real-time appli- cations: this is the case of the ever growing trend of VoIP calls. To this aim, WiMAX supports natively real-time traffic. In this paper, we report on the results of measurements,performed,on a WiMAX Alvarion testbed, located in Turin, Italy. In particular, through syn- thetic VoIP traffic generation, we obtained the corresponding E- model figures, thus tracing the system operation intervals. Categories and Subject Descriptors C.2.1 [COMPUTER-COMMUNICATION NETWORKS]: Network Architecture and Design General Terms
Conference Paper
The advent of 802.16-2004 standard for wireless metro area network (MAN) has created interest amongst telecom service providers. Equipment manufacturers are already marketing point-to-point and point-to-multipoint broadband wireless systems in the 5.8 GHz unlicensed band for fixed applications. Before deploying on a large scale, a precise estimate of capacity and coverage of these systems is needed. This report gives an insight on expected throughput and performance for equipment based on 802.16-2004, using TDD, OFDM, 256 FFT, and many of the WiMAX choices made for use at 5.8 GHz. Tests are setup in different environments, in the lab and outdoors: we first report on a study in a controlled lab environment, where radio multipaths and fades are generated by a channel emulator, simulating Stanford University Interim (SUI) channel models; then the same radio system is tested for throughput in a suburban area in Denver. The two experiments are compared.
Professional and Student Development Workshop
  • Ghz
GHz ", Technical, Professional and Student Development Workshop, 2005 IEEE Region 5 and IEEE Denver Section.
Available: http://dast.nlanr
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IEEE standard for Local and Metropolitan Area Networks-Part 16: Air Interface for Fixed Broadband Wireless Access Systems
IEEE 802.16-2004, "IEEE standard for Local and Metropolitan Area Networks-Part 16: Air Interface for Fixed Broadband Wireless Access Systems", October 2004.
Testing of fixed broadband wireless systems at 5.8 GHz",Technical, Professional and Student Development Workshop
  • T Schwengler
  • N Pendharkar
Schwengler, T. Pendharkar, N., "Testing of fixed broadband wireless systems at 5.8 GHz",Technical, Professional and Student Development Workshop, 2005 IEEE Region 5 and IEEE Denver Section.