1 / 26

Implementation of Test Bed for Dynamic Channel Selection In WLANs

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.

delvaller
Download Presentation

Implementation of Test Bed for Dynamic Channel Selection In WLANs

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Implementation of Test Bed for Dynamic Channel Selection In WLANs Communications Laboratory TKK/HUT

  2. WLANs – Increasing Popularity • Growing Popularity of WLANs • Inexpensive and Flexible • Growing Trend in ad hoc networking • Easy to configure

  3. WLANs – Shortfalls and Issues • Intrinsic unreliable nature of the wireless channel • Unreliable and unpredicable Transmission medium • Speeds less than wired networks • Security

  4. 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)

  5. 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

  6. 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

  7. 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

  8. A Simple DFS Algorithm

  9. 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

  10. Channelization scheme for IEEE 802.11b

  11. Setting Up Test Enviornment • Pentium III Desktop PCs with Realtek 802.11b/g wireless lan cards • Ubuntu v 5.10 linux • wireless_tools.28 toolkit from IBM • Traffic Generator IPerf • Shell Scripting Knowledge  • Patience to install WLAN drivers on linux • Configuring WLANs

  12. 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

  13. Node-A Start Channel Quality Monitoring Quality < Threshold No Yes Channel Change Procedure Node-A Send Channel No. to Peer Node Self Channel Change Procedure Delay Probe Channel for Change Request Yes Received No Change Channel& Send ACK Wait for Confirmation Node-B ACK Received No ACK within a Time Frame Send Confirmation Node-A Channel Quality Measurements Start Again/Stop DSC Application • Text based signalling • Client Server • 3-way Acks • Link Quality analysis and selection Algorithm • Application Layer Implementation

  14. Sequence Diagram for the DCS tool

  15. 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

  16. Data sheet – 1.1

  17. Data Sheet – 1.2

  18. 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

  19. 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

  20. Data Sheet – 2.1

  21. Results • No retrials so lots of lost packets. • Requires a buffer mechanism to be effective to cater when the silent period occurs.

  22. 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 minutes • Alternatively quality threshold can be used to initate the DCS Mechanism

  23. 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

  24. 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

  25. Comparison of the throughputs when the worst channel is in use versus when the Channel Selection Utility is used to select the best channel.

  26. 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

More Related