The important Site Survey

When designing wireless networks, there are many things to have in mind. For example:

• Throughput
• Density
• Supported technology
• Geographical distribution
• Coverage
• Aesthetics
• Application usage
• Client type

An on-site survey helps determine the optimal placement of access points to ensure adequate signal coverage throughout the desired areas. By measuring signal strength, signal-to-noise ratio (SNR), and signal quality at various points in the environment, the survey helps identify potential dead zones or areas with weak coverage.

Software like Ekahau, AirMagnet and Hamina, can be used for Desk Survey as well, where all AP planning are done in software without being onsite. This require knowledge of attenuation in walls etc. and is not as accurate as performing an onsite AP-on-a-stick Survey. With a proffessional Survey kit you alsp have the ability to measure spectrum in both 2,4GHz and 5GHz.

These are important input before performing an onsite Survey

• AP Placement
  • Can AP’s be placed under ceiling “visible”?
  • Ceiling height? (can be verified onsite)
  • Is a cable lenght of maximum 100 meters from rack possible? (min cat5e)?
• Which AP manufacturer should be considered
  • Manufacture/model (Survey will determine)?  
  • Cold/Heat/Environment? 
• Degree of coverage
  • Data, Voice, localization, WiFi-Calling, other….
  • Type of Clients (PC/smartphone(PDA(Terminals, AGV’s etc.)
• Coverage areas
  • Elevators, stairwells, depots, toilets, outside areas etc.
• Density
  • Areas with many clients etc.?
• General
  • attenuation in walls/doors etc, (can be verified onsite)
  • Should rack inspection be included?
  • PoE Capacity?
  • Throughput capacity, mgig etc. ?

Capacity

Channel width on 2.4 GHz is quickly addressed, it is only 20 MHZ. On 5 GHz, there are more options available

By being able to have more non-overlapping channels available at 5 GHz, You have two options for capacity.

1. Lower capacity per. AP using a smaller channel width (typically 20/40 MHz). This allows you to have more access points in the same area without interfering with each other, while distributing the clients apart.
2. Higher capacity per. AP using a larger channel width (typically 40/80 MHz). This means that you can only have fewer access points in the same area, but conversely, you get higher throughput.

Think of channels as a highway, 20 Mhz is one lane, 40 Mhz is two, and 80 MHz has fore lanes. Then think of the cars as data. The more lanes there are, the more data can be pushed through, ind the same amount of time

Challenging locations

In locations like warehouses, production areas etc. Ruggedized AP’s with external antennas are often the the desired choice (high ceiling aisles envirenment etc.), due to the possibility to use directional antennas and higher gain. Some manufactures have AP’s with integrated directional antennas. These AP’s are often more rugged and have higher specification according to temperature range etc.

Wireless Coverage at outside areas requires special AP’s. These AP’s mostly have several power/network options and can be configured as MESH/Bridge to cover diffrent needs.

My experience:

Millions of square meters have been surveyed through i started with wireless in early 00’s. I started up using AirMagnet and later on Ekahau. Also a lot of Surveys have been done using devices like Aircheck. Most important is to use a correct configured ap(s) as AP-on-a-stick.

Requirements are different from customer to customer and its very importnant to clarify needs and expetations. Its recommended to configure survey AP to about 2/3 of maximum power and a static 5GHz channel between 36-48. Disable 2,4GHz to save power on Survey bateri 😉

Recommendations for data

• 10-15% cell overlap
• At each edge, the Received Signal Strength Indication (RSSI) must be at least -70dBm
• Minimum Signat-to-Noise Ration (SNR): 25 dB

Recommendations for Voice

• 5GHz recommended
• At each edge, the Received Signal Strength Indication (RSSI) must be at least -67dBm
• -65 dBm is considered a safe margin to put
• Cisco recommends minimum legacy apeeds of at least 24 Mbps
• Minimum Signat-to-Noise Ration (SNR): 25 dB

Recommendations for localization/positioning

• Mimimum of 4 AP’s required
• AP to AP distance: 40-70 ft.
• Height: below 18 ft.
• -75 dBm Client RSSI on 3 AP’s