Performing a WLAN Site Survey

1. Performing a WLAN Site Survey • Define the need for and the use of a manual site survey tool and differentiate between the following manual site survey types • Active surveys • Passive surveys • Define the need for and use of a spectrum analyzer in a manual site survey • Identification and location of interference sources • Differentiation of Wi-Fi and non-Wi-Fi interference sources • Differentiate between manual and predictive site surveys • Advantages and disadvantages of each site survey methodology • Define the need for and use of a protocol analyzer in a manual site survey as it relates to the following • Identifying, locating, and assessing nearby WLANs • Differentiate between site surveys involving networks with and without a mesh access layer

2. Performing a WLAN Site Survey • Define and differentiate between the following WLAN system architectures and understand site survey concepts related to each architecture. Identify and explain best practices for access point placement and density. • Multiple Channel Architecture (MCA) • Single Channel Architecture (SCA) • Identify limitations on hardware placement • Areas where APs or antennas cannot be placed • Areas beyond Ethernet distance limitations • Understand industry best practices for optimal use of directional and omni-directional antennas in site surveys

3. Exam Essentials • Understand the need for an RF spectrum analysis and how to locate sources of interference. • Know that an RF spectrum analysis will allow you to "see" RF in an area proposed for a wireless LAN. Identify different types of RF interference that can have an effect on a wire­less network. • Know the differences between manual and predictive site surveys. • Know that a manual site survey typically requires a complete walkthrough and testing throughout the proposed area where a wireless LAN will be deployed. A predictive site survey may require minimal time on-site and is a software-based analysis solution. • Identify two different types of manual site surveys. • Know that manual site surveys can be passive or active and the differences between each.

4. Exam Essentials • Know how a protocol analyzer can be used as part of wireless LAN site survey. • Explain how a wireless protocol analyzer can be used to help identify existing wireless networks and how they may have an impact on the site survey. • Understand the importance of identifying existing wireless networks. • Know the impor­tance of existing wireless networks and how they may have an effect on a new wireless LAN deployment. • Be familiar with the limitations of placement regarding wireless infrastructure devices. • Explain some of the limitations regarding placement of wireless LAN devices, including access points, bridges, and antennas. • Understand the factors regarding proper antenna use. • Identify the different uses of anten­nas based on the customer requirements and characteristics of the environment.

5. Performing a WLAN Site Survey • Previous Chapter was about paperwork and planning • This chapter about components and operations • RF Interferance • WiFi and Non-WiFi • Manual vs. Predictive • Manual Surveys • Active and Passive • Tools • Wireless Protocol Analyzers and Scanners • Different Channel Architectures • Multiple (MCA) • Single (SCA) Pg 285

6. The Physical Site Survey Process • Up front work of gathering info, business requirements, site specific docs, defining physical and data security, user interviews • Now do the site survey Pg 285

7. The Physical Site Survey Process • Up front work of gathering info, business requirements, site specific docs, defining physical and data security, user interviews • Now do the site survey • Subjective and there are different opinions of how to do it. Pg 285

8. The Physical Site Survey Process • Arrange a walkthrough of the entire location • Take thorough notes • Perform RF spectrum analysis • Determine preliminary placement of infrastructure devices • Perform on-site testing • Determine actual placement of infrastructure devices • Install infrastructure hardware as specified • Perform on-site verification testing and make adjustments • Deliver final report Pg 286

9. RF Spectrum Analysis Pg 286

10. RF Spectrum Analysis • Spectrum Analyzer • Shows frequency band usage • Physical layer hardware/software tool that analyzes radio frequency waveforms • Can be stand alone device or integrated into something else • USB or PC Card tools • Software that runs on existing wireless network card Pg 286

11. RF Spectrum Analysis Pg 286

12. RF Spectrum Analysis • Find dead spots as well as interference • Regular analysis can be an important part of keeping a WLAN working at expected performance levels Pg 288

13. Wi-Fi and Non-Wi-Fi Interference Sources • Lots of devices operate in the uinlicesend 2.4 Ghz Ism and 5 Ghz UNII bands • Other WLANs • Non Wi-Fi examples • Microwave Ovens • Cordless Telephones • Bluetooth Devices • Medical Equipment • Manufacturing or industrial equipment • Wireless Security Cameras • Radar Systems • Etc Pg 289

14. Spectral Analysis • Chanalyzer on the CD

15. Wi-Fi Interference • Co-Channel • Same channel • Adjacent Channel • Channel that overlaps • FHSS 2.4 Ghz • DSSS 2.4 Ghz • ERP-OFDM 2.4Ghz • OFDM 5 Ghz • HT-OFDM 2.4 Ghz and 5 Ghz Pg 294

16. Wi-Fi Interference • WLANs that interfere could be ad-hoc or infrastructure • RF Spectrum Analysis can give you some indication of where the interference is Pg 294

17. Wi-Fi Interference

18. Wi-Fi Interference

19. Wi-Fi Interference • CWNP defines • Adjacent Overlapping • Channels 1 and 2 • Adjacent Non-Overlapping • Channels 1 and 6 • Co-Channel • Two APs using same channel in same physical area Pg 298

20. Performing a Manual Site Survey • Provides accurate results • Requires a physical walk through • Record information to determine the performance of clients and devices • Record • Signal Strength • Signal to Noise Ratio (SNR) • Data Rate of connected devices Pg 298

21. Performing a Manual Site Survey • Can use inexpensive tools or commercially designed software • Used to determine placement of hardware infrastructure • Can be time consuming and expensive • Especially at larger sites Pg 299

22. Obtaining a Floor Plan or Blueprint • Review floor plan • Often acquired during planning phase • Note AP placement • Note SNR readings and coverage Pg 300

23. Identifying Existing Wireless Networks • ID existing WLANs • Note coverage and RF interference • Can use free software like NetStumbler • Can use commercial software Pg 300

24. Testing Access Point Placement • Typically done with a mobile AP on a pole and a powered cart • The AP is moved from one location to another while the Site Surveyor takes measurements with RF Site Survey software. • Associate to device from site survey computer • Can even test actual devices and applications in some cases Pg 301

25. Analyzing the Results • Analyze results • Determine final placement • Make adjustments • Add access points • Different antenna choices Pg 303

26. Advantages and Disadvantage of Manual Site Surveys • Advantage • Very accurate • Physical characteristics are tested • Verification of actual RF coverage • Can mark exact installation locations • Disadvantages • Time consuming • Usually only one access point Used for testing • Requires walkthrough of entire location • May require an escort Pg 303

27. Software Assisted Manual Site Survey • Manual Surveys can often be done with basic open source tools • Can also be performed with additional software that can help with • Performing active or passive surveys • Import floor plans • Automatically record data • Give a visual representation of RF signal • Perform post-survey analysis Pg 303

28. Passive Site Survey • Monitoring the air and recording RF data from all access points and stations in “hearing range” • No association to AP • No traffic is passed between survey station and AP Pg 304

29. Active Site Survey • Survey machine associates to an AP to take readings • Some believe it is more accurate • Send and receive RF signals • Can record signal strength Pg 305

30. Active& Passive Site Survey • Both require many of the same tools • Difference is often features/capabilities of software • Better documentation and automation Pg 305

31. Manual Site Survey Toolkit • Floor Plan • Spectrum Analyzer • Access Points • Client Device • Battery packs/Extension Cords • Antennas • Temporary Mounting Hardware • Measuring Device (Tape or Wheel) • Digital camera • Pens, Paper, Pencil • Ladder • Cart Pg 306

32. Performing a Predictive Site Survey • Done without on-site survey • Can use commercial software • Sometimes functions are built in to wireless LAN Controller/Switch • Often called “Virtual” site surveys because they are performed off-site with computer-aided modeling software. Software predicts how RF signals will travel from each AP. • Require the use of imported vector or raster graphics • Use databases of loss values for RF obstacles such as doors, walls, and windows • Can accurately predict where to place APs for best coverage/throughput • Output information is only as good as input information (it’s a computer after all) • When used in concert with a manual site survey, accuracy is significantly improved Pg 308

33. Performing a Predictive Site Survey • Cant take into account interference from existing sources Pg 308

34. Protocol Analysis • Often used for wired networks • Many tools available • Watches all wireless frames to let you view details and do analysis • Used to • Troubleshoot network problems • Gather security information • Optimize performance Pg 308

35. Protocol Analysis • Can help locate • Access points • Ad-hoc networks • Wireless bridges • Mesh Networks • Client Devices Pg 308

36. Protocol Analysis Pg 308

37. Documenting Existing Network Characteristics • Understanding current infrastructure is important • What frequency range will the new WLAN work on? • Are there any existing LANs in RF space? • Will all or part of the existing WLAN be utilized in new deployment? • What effect will the neighboring wireless networks have on the deployment? Pg 318

38. RF Coverage Requirements • Size of area • Number of users • Obstacles • Signal Propagation • RF range • Bandwidth requirements of applications • Frequency Band of WLAN hardware Pg 318

39. Infrastructure Hardware Selection and Placement • Survey helps determine location of hardware based on • RF Coverage • Bandwidth • Aesthetics • Applications • Cell Overlap • Channel Reuse Pg 320

40. Infrastructure Connectivity and Power Requirements • Need to know the existing wired infrastructure • Distribution • Power availability • POE is an option Pg 320

41. Received Signal Strength • Goal is two way communications • Reliable connectivity • Receiver must have enough signal to determine what was sent • Use the received Signal strength to show the amount of power received in a transmission Pg 321

42. Received Signal Strength • Amount of received signal strength required is affected by type of applications and RF noise • Noise is interference • Signal to Noise Ration (SNR) is difference between signal and noise floor • Signal is -65dBm and noise floor is -95dBm • SNR is 30 dB Pg 321

43. Received Signal Strength Pg 322

44. Antenna Use Considerations • Omnidirectional • Dipole • Semidirectional • Patch • Panel • Sector • Yagi • Highly Directional • Parabolic Pg 323

45. Testing Multiple Antenna Types • During Survey, you may want to try and document different antennas • Aesthetics can affect choice • Other site requirements Pg 323

46. Channel Architectures • Two main architectures • Multiple Channel • APs are set to different channels that don’t overlap to minimize interference • Can be manually set or automatically chosen • Single Channel • Fairly New technology • Controller can manage all APs in same channel • Not everyone transmits at same time Pg 325

47. Single Channel Architecture (SCA) • Stacking, Spanning, Blanketing • Each floor in a building has a channel Pg 326

48. Installation Limitations • May be limited in where you can install APs • May be limited in antenna choice • Mounting • Cabling • Aesthetics • Height • Ethernet/POE • Max cable run Pg 326

49. Site Survey Report • Typically a Microsoft Word or Adobe PDF formatted document that includes: • AP locations, configurations, and mounting considerations • Documentation exported from a predictive or manual RF Site Survey software tool • Deployment recommendations

50. Exam Essentials • Understand the need for an RF spectrum analysis and how to locate sources of interference. • Know that an RF spectrum analysis will allow you to "see" RF in an area proposed for a wireless LAN. Identify different types of RF interference that can have an effect on a wire­less network. • Know the differences between manual and predictive site surveys. • Know that a manual site survey typically requires a complete walkthrough and testing throughout the proposed area where a wireless LAN will be deployed. A predictive site survey may require minimal time on-site and is a software-based analysis solution. • Identify two different types of manual site surveys. • Know that manual site surveys can be passive or active and the differences between each.