Planning AP Coverage

Question 1

What are the 2 ways to effect the size of an AP’s cell?

Answer 1

Change the transmitter power

Change the available data rates

Question 2

What is the potential problem of increasing the cell size by increasing the AP’s transmitter power?

Answer 2

You might have an assymmetric power problem. A client on the outer edge of the cell may not have enough transmitter power for the AP to hear the client.

Question 3

Is the decision to roam driven by the AP or the client?

Answer 3

A client decides to roam based on its vendor specific roaming algorithm.

Question 4

AP assisted roaming was defined in 802.11k. What does it do?

Answer 4

The client can ask the AP for a list of other potential candidate AP’s so it doesn’t have to spend time scanning and sending probe requests.

Question 5

What percentage of overlap between cells does Cisco recommend for data and voice?

Answer 5

10 -15% for data

15 -20% for voice

Question 6

Laying out the cells in a honeycomb fashion has what benefits?

Answer 6

It leaves no holes and it allows for a better alternating channel pattern.

Question 7

Alternating channels to avoid overlap is commonly called what?

Answer 7

Channel reuse

Question 8

What is RTLS and how would it change your placement of APs?

Answer 8

Real-Time Location Services

Outermost APs should be placed near the perimeter of the building to better triangulate devices.

Question 9

What are the three basic categories of site survey tools?

Answer 9

Standalone (usually installed on a laptop)
Server-based (usually part of a larger integrated management tool)
Cloud-based (for designing and predicting survey results without collecting RF data)

Question 10

What are the three basic types of site surveys and what interaction do they have with APs?

Answer 10

Predictive survey (also called planning survey)
    None: all measurement are calculated
Passive survey
    Listening only
Active survey
    Full association and roaming

Question 11

One survey method is commonly called AP-on-a-stick. What type of site survey uses this method?

Answer 11

Active survey

Question 12

A survey client can be configured for one of two active survey methods. What are they?

Answer 12

BSSID method
    Client stays associated to a 
    single AP to measure a single cell
SSID methon
    Client can associate and roam to
    any AP over a consistent SSID

Question 13

What are the three distinct phases of a wireless network deployment?

Answer 13

Pre-deployment
Deploy the APs
Post-deployment

Question 14

What would be the 4 types of surveys to perform during a pre-deployment phase?

Answer 14

Predictive or planning survey
Passive survey (gauge existing WiFi)
Spectrum analysis (gauge interference)
AP-on-a-stick (gauge cell size)

Question 15

What would be the 2 types of surveys to perform during a post-deployment phase?

Answer 15

Passive survey
   Verify that network is operational
Active survey
   Verify client operation, roaming,
   performance

Question 16

How many dB may be lost on the other side of the elevator shaft?

Answer 16

30 dB

Question 17

When doing a predictive survey, how many dB loss would you expect for light objects, like cubicles and bookshelves?

Answer 17

2 dB

Question 18

When doing a predictive survey, how many dB loss would you expect for thick walls with brick or concrete?

Answer 18

10 - 12 dB

Question 19

When doing a predictive survey, how many dB loss would you expect for thin walls with drywall?

Answer 19

3 dB