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Implementation of Test Bed for Dynamic Channel Selection In WLANs. Communications Laboratory TKK/HUT. WLANs – Increasing Popularity. Growing Popularity of WLANs Inexpensive and Flexible Growing Trend in ad hoc networking Easy to configure. WLANs – Shortfalls and Issues. - PowerPoint PPT Presentation
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Implementation of Test Bed for Dynamic Channel Selection In
WLANs
Communications Laboratory TKK/HUT
WLANs – Increasing Popularity
Growing Popularity of WLANsInexpensive and FlexibleGrowing Trend in ad hoc networkingEasy to configure
WLANs – Shortfalls and Issues
Intrinsic unreliable nature of the wireless channel
Unreliable and unpredicable Transmission medium
Speeds less than wired networksSecurity
WLAN Standards
IEEE 802.11 - 1 Mbit/s and 2 Mbit/s, 2.4 GHz RF and IR standard (1997)
IEEE 802.11a - 54 Mbit/s, 5 GHz standard (1999, shipping products in 2001)
IEEE 802.11b - Enhancements to 802.11 to support 5.5 and 11 Mbit/s (1999)
IEEE 802.11g - 54 Mbit/s, 2.4 GHz standard (backwards compatible with b) (2003)
IEEE 802.11h - Spectrum Managed 802.11a (5 GHz) for European compatibility (2004)
Contribution of Thesis
Comparative Study of DFS in 802.11b Vs Static Channels In Ad hoc Networks Multiple radio interferences on a limited
Bandwidth Multilple networks on a Single Channel Degradation in Throughput Inflexibility of Channel allocation Better quality link possible of unused channel
The Solution
Creating a Dynamic Channel Selection (DSC) Mechanism for WLANs in the 2.4GHz band
Providing a testbed to obsreve the Improvements offered by the use of a DSC Application
Analyse the improvement in Throughput
Dynamic Frequency Selection in WLANs
Provided by the IEEE 802.11h extention to the IEEE 802.11a standard
No mechanism currently being employed in IEEE 802.11b/g WLANs
A Simple DFS Algorithm
Channel Deployment Issues in the 2.4GHz band
A total of 11 channels in both IEEE 802.11b and IEEE 802.11g standards
Limited to 3 usable channels due to the interchannel interfernces
Limits the DSC scheme to effectively only switch between 3 channels
Channelization scheme for IEEE 802.11b
Setting Up Test Enviornment
Pentium III Desktop PCs with Realtek 802.11b/g wireless lan cards
Ubuntu v 5.10 linuxwireless_tools.28 toolkit from IBMTraffic Generator IPerfShell Scripting Knowledge Patience to install WLAN drivers on linuxConfiguring WLANs
Lab enviornment iwlist wlan0 scan wlan0 Scan completed : Cell 01 - Address: 00:14:BF:E6:53:5E ESSID:"dtn_demo" Mode:Master Frequency:2.412 GHz (Channel 1) Quality=37/100 Signal level=12/100 Noise level=0/100 Encryption key:off Bit Rates:54 Mb/s Cell 02 - Address: 00:16:B6:5B:E4:A4 ESSID:"aalto" Mode:Master Frequency:2.412 GHz (Channel 1) Quality=38/100 Signal level=13/100 Noise level=0/100 Encryption key:off Bit Rates:54 Mb/s Cell 03 - Address: 00:16:B6:5B:CB:FB ESSID:"aalto" Mode:Master Frequency:2.437 GHz (Channel 6) Quality=32/100 Signal level=5/100 Noise level=0/100 Encryption key:off Bit Rates:54 Mb/s Cell 04 - Address: 42:DC:B9:77:91:7B ESSID:"wrt54gs" Mode:Ad-Hoc Frequency:2.437 GHz (Channel 6) Quality=36/100 Signal level=11/100 Noise level=0/100 Encryption key:off Bit Rates:11 Mb/s Cell 05 - Address: 6E:FF:7B:87:23:1B ESSID:"adhoc_test" Mode:Ad-Hoc Frequency:2.412 GHz (Channel 1) Quality=62/100 Signal level=47/100 Noise level=0/100 Encryption key:off Bit Rates:22 Mb/s
DSC Application
Node-A Start
Channel Quality Monitoring
Quality < Threshold
Channel Change Procedure
Send Channel No. to Peer Node
Probe Channel for Change Request
Change Channel& Send ACK
Received
ACK
Received
Wait for Confirmation
Send Confirmation
Channel Quality Measurements
Start Again/Stop
Delay
Self Channel Change Procedure
Yes
Yes
No
No
No ACK within a Time Frame
Node-B
Node-A
Node-A
Text based signallingClient Server3-way AcksLink Quality analysis
and selection AlgorithmApplication Layer
Implementation
Sequence Diagram for the DCS tool
Test Case – 1
Comparison of channel performance in a bad channel versus a channel selected by using the Channel Selection Utility for TCP traffic
Intervals of 300, 900, 3600, 7200, 10800, 21600
Data sheet – 1.1
TCP Traffic Without Channel Selection Utility
Time (sec) Data Transferred (Kbytes) Throughput (Mbits/sec)
240 42086.4 1.43
300.5 52428.8 1.43
600.5 104448 1.43
900.5 157696 1.43
3600.5 624640 1.42
7200.5 1139160 0.158
10800.7 1866465 1.42
21600.5 3718705 1.42
Data Sheet – 1.2
TCP Traffic With Channel Selection Utility
Time (sec) Data Transferred (Kbytes) Throughput (Mbits/sec)
240.5 18124.8 0.617
300.4 30617.6 0.833
600.4 82227.2 1.12
900.5 142336 1.3
3600.6 615424 1.4
7717 1290824 0.167
10800.8 1939865.6 1.47
21600.4 3845923 1.46
Results
Time consumed in the execution of DCS degrades throughput at smaller intervals due to the silent period
Improvement only seen in times greater than one hour
Test Case – 2
Comparison of channel performance in a bad channel versus a channel selected by using the Channel Selection Utility for UDP traffic with a continuous data transfer.
Intervals of 300, 900, 3600, 7200, 10800, 21600
Data Sheet – 2.1UDP Traffic Without Channel Selection Utility
Time (sec)
Data Transferred
(Kbytes)
Throughput (Kbits/sec)
Jitter (msec)
lost/total %lost
240 30 1.05 1.867 1/21401 0.0046%
300 37 1.05 0.297 0/26751 0%
600 75 1.05 1.117 0/53501 0%
900 113 1.05 0.04 0/80251 0%
UDP Traffic With Channel Selection Utility
Time (sec)Data Transferred
(Kbytes)Throughput
(Kbits/sec)Jitter (msec) lost/total %lost
124 6.98 473 0.554 6219/11198 56%
240 14.3 623 0.069 8689/21401 41%
300 25.7 719 0.261 8403/26751 31%
600 63.2 884 0.014 8398/53501 16%
Results
No retrials so lots of lost packets.Requires a buffer mechanism to be
effective to cater when the silent period occurs.
Test Case – 3
The purpose of this test case is to compare the throughput of the radio interface when burst of traffic is generated instead of continuous traffic.
5 Mbytes of traffic every 5 minutes from 0800hrs to 1800hrs
DCS mechanism initated every 20 minutesAlternatively quality threshold can be used
to initate the DCS Mechanism
Throughput over the time interval of 0600hrs to 1800hrs, where 5Mbytes of data is transferred every 5 minutes on the worst channel. Average Throughput 1.408 Mbits/sec
Throughput on worst channel from 0600hrs to 1800hrs
1.1
1.15
1.2
1.25
1.3
1.35
1.4
1.45
1.5
06:0
0
06:2
0
06:4
0
07:0
0
07:2
0
07:4
0
08:0
0
08:2
0
08:4
0
09:0
0
09:2
0
09:4
0
10:0
0
10:2
0
10:4
0
11:0
0
11:2
0
11:4
0
12:0
0
12:2
0
12:4
0
13:0
0
13:2
0
13:4
0
14:0
0
14:2
0
14:4
0
15:0
0
15:2
0
15:4
0
16:0
0
16:2
0
16:4
0
17:0
0
17:2
0
17:4
0
18:0
0
Time (sec)
Th
rou
gh
pu
t (M
b)
Throughput over the time interval of 0600hrs to 1800hrs, where 5Mbytes of data is transferred every 5 minutes while the Channel Selection Utility is used 2-3 times per hour. Average Throughput 1.467Mbits/sec
Throughput on channel selected after executing the Channel Selection Utility from 0600hrs to 1800hrs
1.32
1.34
1.36
1.38
1.4
1.42
1.44
1.46
1.48
1.5
06:0
006
:2006
:4007
:0007
:2007
:4008
:0008
:2008
:4009
:0009
:2009
:4010
:0010
:2010
:4011
:0011
:2011
:4012
:0012
:2012
:4013
:0013
:2013
:4014
:0014
:2014
:4015
:0015
:2015
:4016
:0016
:2016
:4017
:0017
:2017
:4018
:00
Time (sec)
thro
ug
hp
ut
(Mb
its/
sec)
Comparison of the throughputs when the worst channel is in use versus when the Channel Selection Utility is used to select the best channel.
Comparision of Throughputs with the Utility vs the Worst Channel
1.1
1.15
1.2
1.25
1.3
1.35
1.4
1.45
1.5
1.55
06:0
006
:2006
:4007
:0007
:2007
:4008
:0008
:2008
:4009
:0009
:2009
:4010
:0010
:2010
:4011
:0011
:2011
:4012
:0012
:2012
:4013
:0013
:2013
:4014
:0014
:2014
:4015
:0015
:2015
:4016
:0016
:2016
:4017
:0017
:2017
:4018
:00
Time (Sec)
Th
rou
gh
pu
t (M
bit
s/se
c)
Channel Selected by Utility Worst Channel
Conclusions
Very distinct Improvement in throughput Implementation on application layer is not
efficient Taking advantage of the Draft IEEE 802.11k
standard for development of DCS mechanim Buffer for UDP traffic during silent period Development of selection algorithms Compatibilty of WLAN drivers in Linux
distribution. www.linux-wlan.org Simplification of network configuration needed