1. Overview of the ORBIT Radio Grid Testbed for Evaluation of Next-Generation Wireless Network Protocols D.Raychaudhuri, M.ott, S.Ganu, K.ramachandran, H.Kremo, R.Siracusa, H.Liu, Singh WINLAB Reviewed by Lee YoungSoo

2. Motivation  There is great deal of research activity on future wireless/sensor networks and application.  Do not capture real physical layer effects.  ORBIT aims to provide a flexible, open-access multi-user experimental facility to support research on next-generation wireless networks.

3. Difference from wired testbed  Radio channel properties depend on specific wireless node locations and surroundings.  Physical layer bit-rates and error-rates are time- varying.  Shared medium layer-2 protocols on the radio link have a strong impact on network performance.  There are complex interactions between different layers  User’s exhibit random mobility and location.

4. ORBIT testbed’s goal  Scalability  Reproducibility  Open-access flexibility  Extensive measurements capability  Remote access

5. 2-Tier ORBIT system architecture

6. ORBIT system architecture

7. Hardware components  ORBIT radio nodes  1-GHz VIA C3 processor with 512 MB of RAM & 20GB local hard disk  Two wireless mini-PCI 802.11 a/b/g interfaces  Integrated chassis manager : remotely monitor the status of each radio node’s hardware.  Instrumentation subsystem  Provide capabilities for measurement of radio signal levels & create artificial RF interference.

8. Hardware components  Independent WLAN monitor system  Provide MAC/network layer view of radio grid’s components  Support severs  Front-end servers for web services and backend server for experimentation and data storage.

9. Software components  Management/ Control software.  Software for Radio nodes.

10. Management/Control software  Node Handler  Disseminate experiment scripts using multicast to the Node Agent.  Node Agent  Reports back the state of experiment command execution to the Node Handler.  Disk-Loading Server  Enable to quick re-imaging of hard disks on the nodes as per the requirements of the user.

11. Measurement collection software  ORBIT Measurement Library(OML)  Filters to be applied to each measured metric.  Collection Server(CS)  Collect the reported measurements

12. Lifecycle of an Experiment  The experiment details are translated into a script.  The information is disseminated by Node Handler.  The Node Agent executes the script.

13. Lifecycle of an Experiment  Performs the experiment which may involves statistics collection done by OML library.  A separate run-time and post-experiment database allows users to quickly view results.

14. Sample Experiment Results.  Ex.1) To study the effect of 802.11b interference on the performance of a link under test.  Consist of 8 nodes, send UDP packets.  6 interfering nodes, send UDP packets.

15. Sample Experiment Results.

17.  Ex.2) Effect of varying transmit power of sender on the performance in the presence of interferers.  Demonstrate the effect of changing the transmit power of sender-receiver link.  One sender-receiver pair.  6 interferers.

18. Sample Experiment Results.

19.  Ex.3) Multi-hop experiment with dual interface forwarding node(FN)  Measure the improvement in network performance for a multi-hop network with and without using a dual interface forwarding node.

20. Sample Experiment Results.

21. Conclusion  Present the design of a novel radio grid emulator testbed that facilitate a broad range of experimental research on next-generation protocols & applications.  Proof-of-concept validation of the testbed design.