WSEC Lab1 IBSS RF Catchment Zone Student __________________________________________
The purpose of this Lab is to determine the RF
catchment zone of an IBSS
PC with a WNIC is stationary while a second portable PC is moved to map out the
catchment area. This is repeated for several different physical topologies to
see the effect of construction materials (walls, floors, metal barriers, etc)
upon the size of the catchment area. Mapping the catchment zone by taking
signal-to-noise (S/N) measurements (via Cisco ACU) is crucial to securing a WLAN.
Mapping the catchment zone by taking signal-to-noise (S/N) measurements (via Cisco ACU) is crucial to securing a WLAN.
Required devices: Two laptops: each with a Cisco Aironet 350 WNIC properly installed. More laptops needed if all students are to fully participate simultaneously.
1. Open the Aironet Client Utility (ACU) on each PC. The ACU should indicate, “Your 350 Series is in Ad Hoc Mode” (bottom line of ACU). If it doesn’t indicate Ad Hoc mode you must troubleshoot. Make sure that all access points (APs) and wireless bridges (WGBs) in the vicinity are off.
2. With both PCs in close proximity, open the ACU “Status” menu. You should see indicators for signal strength, noise level, and signal to noise ratio (S/N). Write in the values that you observe: Signal strength ___________dbm, noise level __________dbm, and S/N ratio ______________ dB. A S/N ratio of at least 20dB is acceptable (10dB is a limit).
3. Which RF channel is used (check each PC)? __________ ____________
4. What is the automatically pre-established data rate? ____________Mbps
5. What is the status mode? ___________________________
6. Is CAM being used? ________
7. What is the beacon period setting? ____________ms
8. What is the WNIC firmware version? _________________________
9. What is the MAC address of each WNIC?
10. What is the RF broadcast power level? _________mW. Is it adjustable? ___________
11. Open the “Link Status Meter” menu. What does this utility provide? _______________________________________________________________________
12. Open the “Site Survey” menu. What information is indicated here? __________________
_________________ _________________ _________________ _________________
___________________________ __________________________ ______________________
13. You will now perform a walk-away test to determine the catchment zone in your particular environment. With the stationary PC in a far corner, move the portable PC (on a cart) while monitoring the “Site Survey” menu.
14. Continue moving away from the stationary PC (down the hall, etc) until the S/N ratio drops to about 10dB. Now measure the distance traveled between the 2 PCs ______ ft. This distance should be the straight-through distance from PC to PC. This distance is the radius of the catchment zone (r). The catchment area is (pi)(r)(r). Calculate the catchment area _____________________________ ft squared.
15. Repeat steps 13 and 14 again using a different direction (different hall direction, down/up the stairwell, etc). How different are the catchment areas? ____________________ _________________________ ____________________________. How does the wall(s) affect the catchment area? ____________________________. Floor? __________________________________________. Describe the physical topology and building materials encountered. Sketch layout below. __________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
16. Sketch a graph of distance vs S/N ratio (dB) for the worst-case scenario.
17. Speculate what you think the catchment zone would be for a three-PC IBSS WLAN (one stationary and two mobile PCs). Sketch here.
18. What can happen to communication between the end PCs as the distance increases? ___________________________________________________________________.
19. Is it possible for one PC to act as a repeater for another PC? _____________.
20. What other WLAN device(s) should be used to extend the distance between end users? _________________________ __________________________________