Certified Wireless Technology Administrator - Chapter 11 - Performing an RF Wireless LAN Site Survey
You are a network consultant hired to perform a manual site survey for a small office building. The wireless network to be installed will use data and voice. For backward compatibility, the customer needs to support 2.4 GHz equipment. To provide the highest quality of service for the voice application, you recommend that the received signal strength be a minimum of ________ for a data rate of 54 mbps. A. -20 dBm B. -25 dBm C. -67 dBm D. -76 dBm
-67 dBm
What is considered to be the minimum received signal strength indicator or RSSI when setting up a wireless LAN installation?
-67dBm
If a signal is -65 dBm and the noise level is -90 dBm, what is the signal-to-noise ratio?
25 dB
What is the recommended output power level for access points when performing a wireless LAN site survey?
50%
What is the difference between manual and predictive modeling site surveys?
A manual site survey typically requires a complete walkthrough and testing throughout the proposed area where a wireless LAN will be deployed. A predictive modeling site survey may require minimal time on-site and is a software-based analysis solution.
What is a predictive model wireless LAN site survey?
A software-based solution that simulates the wireless LAN installation, such as access point placement and RF propagation.
What is multiple-channel architecture or MCA?
Access points are set to different nonoverlapping channels to minimize interference.
You have been hired by a company to perform a manual site survey. When explaining the difference between a manual and predictive modeling site survey, you let the customer know the advantages and disadvantages of each. A manual site survey has which advantage? A. Speed B. No hardware required C. Accuracy D. Facility access not required
Accuracy
What type of site survey requires an IEEE 802.11 association from the wireless survey device?
Active
When a device associates to an access point during a site survey, it is performing what type of survey? A. Predictive B. Active C. Passive D. Required
Active
What is unique about single channel architecture (SCA) and wireless LAN site surveys?
All access points are set to the same RF channel.
A main objective of a wireless LAN site survey is to determine _______ and ________. Choose the best two options. A. Areas of RF interference B. Applications to be used C. Access point locations D. Wiring closet locations E. Security implementations
Areas of RF interference and Access point locations
Co-channel interference is caused by access points on __________________. A. Channels 1 and 1 B. Channels 1 and 2 C. Channels 1 and 6 D. Channels 1, 6, and 11
Channels 1 and 1
You have been hired by a company to perform a wireless LAN site survey in a multitenant building. You discover numerous access points on channels 1, 6, and 11. To optimize the new deployment, what recommendation could you make to the customer? Assume that all new hardware will be purchased and backward compatibility is not required. A. Configure the access points to automatic channel selection for the 2.4 GHz ISM band. B. Configure the access points to operate in the 5 GHz band. C. Perform a spectrum analysis to find space in the 2.4 GHz band. D. Perform a predictive modeling site survey to determine which channels to use.
Configure the access points to operate in the 5 GHz band.
You need to perform a site survey for a small real estate office that currently has no wireless network. Which factors must be considered as part of the site survey? A. Spectrum analysis B. Packet analysis C. Environmental conditions D. Correct antenna selection
Correct antenna selection
When performing a manual site survey, choose the best way to identify areas that lack RF coverage. A. Mark them with tape so they can be located at a later time. B. Use a camera to take a photograph and document it in the report. C. Show the site manager the areas that lack coverage. D. Document on the floor plans or blueprints.
Document on the floor plans or blueprints.
A physical walkthrough of the proposed installation location should be performed before what type of wireless LAN site survey?
Either manual or predictive.
What should be documented when performing any kind of site survey?
Everything!
What is received signal strength?
How much of the transmitted signal a wireless client device will receive.
Which of the following is true of a predictive modeling survey? A. It takes more time than a passive survey to get accurate results. B. It takes less time than a passive survey to get accurate results. C. It finds areas of interference from neighboring wireless LANs. D. It helps you choose the manufacturer's equipment to be used for the wireless LAN.
It takes less time than a passive survey to get accurate results.
What is an advantage of a manual wireless LAN site survey?
It's very accurate because it is based on actual readings, allows you to verify actual RF signal coverage, mark exact installation locations of hardware on-site.
What is an advantage of a predictive modeling wireless LAN site survey?
Limited time on-site, does not require physical testing.
What type or types of antennas are commonly used while performing a physical site survey of an indoor office complex?
Low-gain omnidirectional.
When using a predictive modeling site survey approach, which of the following is true about manual verification? A. Manual verification never has to be performed. B. Manual verification is always required. C. Manual verification should be performed only at the customer's request. D. Manual verification should be performed, but it is not required.
Manual verification should be performed, but it is not required.
Non-Wi-Fi interference for an 802.11g network can be caused by _________ and _________. Choose two. A. AM radios B. Microwave ovens C. 802.11b networks D. Cordless phones E. Radar systems F. Digital TV systems
Microwave ovens and Cordless phones
Interference that is not related to IEEE 802.11 wireless LANs. It can be caused by devices that operate in the 2.4 GHz ISM band or the 5 GHz UNII band, such as microwave ovens, cordless phones, and ground radar.
Non-Wi-Fi interference
Microwave ovens can cause what type of interference?
Non-Wi-Fi interference.
You are performing a protocol analysis in order to determine potential interference from other wireless LANs in the immediate area of the site survey. You discover several wireless LANs that can potentially cause interference with the proposed installation. Which technology in use would not have an impact on the 802.11g wireless network you are surveying for? A. FHSS B. OFDM C. DSSS D. ERP-OFDM E. PBCC
OFDM
What type of wireless LAN site survey listens to all access points in the hearing range of the wireless site survey device?
Passive
The manual site survey consists of which possible methods? Choose two. A. Passive B. Scanning C. Active D. Spectrum E. Packet
Passive and Active
Name the two types of manual wireless LAN site surveys.
Passive and active.
What might some fire codes require for cable installation in certain places?
Plenum rated or fire-retardant cable and devices.
_____________ of antennas must be taken into consideration during a manual site survey. __________ of antennas for infrastructure devices is critical, and tests should mimic as closely as possible what will actually be installed.
Polarization
A method for supplying DC voltage and computer data together over a single Ethernet cable.
Power over Ethernet or PoE
A type of site survey that is software-based, requires minimum time on-site, and takes into consideration the attenuation value of materials such as the type of walls and doors is ____________. A. Active B. Passive C. Predictive D. Optional
Predictive
A spectrum analyzer can be used to view what? A. Radio frequency B. Wireless packets C. Data rates D. Association frames
Radio frequency
You are using a wireless client adapter with a site survey utility and a notebook computer to perform a manual site survey in a very small office building. Which values are important to record to verify proper RF coverage for the location? Choose two. A. Signal strength B. SNR C. Packet retries D. Signal loss E. Propagation loss
Signal strength and SNR
What are two values that can be monitored during a manual RF wireless LAN site survey?
Signal strength, signal-to-noise ratio or SNR.
What tool can be used during a wireless LAN site survey to determine sources of RF interference?
Spectrum analyzer
What devices, tools, or programs can be used in a manual site survey? Choose two. A. Spectrum analyzer B. Passive scanning utility C. Predictive site analyzer D. Association analyzer E. Authentication analyzer
Spectrum analyzer and Passive scanning utility
You are a network engineer tasked with performing a site survey for a multiple-channel architecture or MCA system in a three-story building. Which characteristic must be considered while performing a site survey? A. All omnidirectional antennas should be vertically polarized. B. Multiple floors require the same channel. C. Each floor should be treated as an individual site survey. D. The channel plan should take all three floors into consideration.
The channel plan should take all three floors into consideration.
What is the signal-to-noise ratio or SNR?
The difference between the received signal strength and noise floor.
What purpose will a protocol analyzer serve in a wireless LAN site survey?
To determine existing wireless networks that are in the same RF listening area.
What can NetStumbler or InSSIDer be used for during a wireless LAN site survey?
To find existing wireless networks.
What can battery packs be used for in a wireless LAN site survey?
To temporarily power access points.
Which guidelines are recommended when performing a manual site survey? Choose two. A. Walkthrough of location B. Predictive analysis C. Equipment purchase D. Client device configuration E. Spectrum analysis
Walkthrough of location and Spectrum analysis
Interference caused by other IEEE 802.11 wireless networks operating in the 2.4 GHz ISM or 5 GHz UNII bands.
Wi-Fi interference
When considering the use of antennas for wireless LAN deployment during a site survey, which antenna could be tested to verify proper coverage for a long hallway or corridor? A. High-gain omnidirectional B. Low-gain omnidirectional C. Parabolic dish D. Yagi
Yagi
A semidirectional antenna typically used outdoors for short-range bridging or indoors for long hallways and corridors to provide RF coverage to a specific area.
Yagi antenna
A type of manual wireless LAN site survey that requires an association to an access point.
active site survey
A performance condition that occurs when two or more access point radios are providing RF coverage to the same physical area using overlapping frequencies. Simultaneous RF transmissions by two or more of these access point radios in the same physical area can result in corrupted IEEE 802.11 frames due to the frequency overlap. Corrupted 802.11 frames cause retransmissions, which results in both throughput degradation and latency.Also called adjacent overlapping channel interference.
adjacent channel interference
A performance condition that occurs when two or more independently coordinated access point radios are providing RF coverage to the same physical area using the same 802.11 channel. Additional RF medium contention overhead occurs for all radios using this channel in this physical area, resulting in throughput degradation and latency.
co-channel interference
Areas that lack wireless LAN coverage.
dead spots
Internet or web-based predictive modeling wireless site survey programs available. This type of program is based on the assumption that you will be using their equipment in your wireless LAN deployment.
internet-based predictive modeling site survey
A wireless network design in which access points are set to different nonoverlapping channels to minimize interference.
multiple-channel architecture or MCA
A type of manual wireless LAN site survey that monitors all access points in an RF coverage area. No association to an access point is required.
passive site survey
A software-based wireless LAN site survey in which a floor plan or drawing of the area to be surveyed is imported into the program. The program then simulates the RF propagation from access points by using the attenuation properties of obstacles. Accuracy and final results are only as good as the information that was input into the program.
predictive modeling site survey
An application that allows a network engineer to view all wireless frames traversing across the air in the hearing range of the wireless LAN analyzing device.
protocol analyzer
The minimum amount of signal a receiver must be able to receive in order to determine the data that was sent from the transmitter.
received signal strength
The RF noise value in dBm minus the received signal strength in dBm. The minimum recommended value for wireless networking is 20dB to 25dB or higher.
signal-to-noise ratio or SNR
A wireless network design in which all access points operate on the same channel and are managed by a centralized controller to avoid interference.
single-channel architecture or SCA
An instrumentation device or a hardware or software utility used to view radio frequency energy over a range of frequencies. In wireless networking, a spectrum analyzer can be PC card-based, designed specifically for WLAN use, or a separate instrumentation device—a calibrated device that has the capability to view an entire radio spectrum.
spectrum analyzer
A single-channel architecture management technique in which each floor or area of a building is assigned a channel to use. Spanning and blanketing are other terms used to identify managed areas based on channels.
stacking
The design, layout, or channel plan in use. In the 2.4 GHz band, for example, the use of nonoverlapping channels 1, 6, and 11 is a channel architecture. The two common types are multiple-channel architecture or MCA and singlechannel architecture or SCA.
wireless channel architectures
What are some disadvantages of a manual wireless LAN site survey?
• Can be very-time consuming • Usually only one access point is used for testing, so readings will need to be merged • Requires a physical walkthrough of entire location • Many areas require an escort and special clearances for access
What should be included in the main content of the site survey report?
• Customer requirement analysis • Radio frequency interference source analysis • Radio frequency coverage analysis • Device capacity and application analysis • Infrastructure device placement and configuration information
What criteria is the location of wireless infrastructure devices traditionally based on?
• Desired RF coverage • Required bandwidth • Aesthetics requirements • Applications both hardware and software • RF cell overlap • Channel reuse patterns
What factors should be taken into consideration when choosing antennas?
• Manufacturer's Recommendations • Customer Requirements • Environmental Conditions • Aesthetics • Required Coverage • Number of Wireless Access Points • Physical Geometry of Location • Regulatory Agency and Local Codes
What are some examples of devices that can cause non-Wi-Fi interference in the ISM band?
• Microwave ovens • Cordless telephones • IEEE 802.15 Bluetooth devices • Medical equipment • Manufacturing or industrial equipment • Wireless video cameras • Radar systems (5 GHz bands)
A manual site survey can be very accurate because it records actual statistics such as what?
• Signal strength • Signal-to-noise ratio or SNR • Data rate of connected devices • Radio Frequency interference
What are some disadvantages of a predictive modeling wireless LAN site survey?
• Surveyor may be unfamiliar with the location's physical characteristics • Accuracy limited to data input within program • Requires extensive knowledge of physical properties of the installation area including attenuation values
