Inside a Wireless Access Point

Typically when working with a technology, I like to go beyond the theory and practical aspect and see how things actually work and look like on the inside. In wireless it’s no different…

I had a faulty Cisco 3502E series AP come back to my office from one of our locations that had replaced it for a new 2700 series AP. It was DOA and as we stopped using the 3502E series, it was meant to be disposed of. I decided to open it up and simply take a peak to get a better understanding of what is inside this shell that provides the world with this amazing piece of technology we call Wi-Fi.

Cisco AP’s, specifically the external models, come with a rugged metal housing as they are ideal for factories, warehouses and other indoor industrial environments. The housing is solid and it would take a pretty large amount of force to really damage this thing.

3502E

The 3502E is a dual-band (2.4GHz and 5GHz) access point supporting 802.11n.

Antenna specification: 2×3:2 MIMO
2 x Transmit (Tx), 3 x Receive (Rx), 2 x Spatial Streams

  • Each band has 3 antenna.
  • On the left side there are 3 antenna for the 2.4GHz band.
  • On the right side there are 3 antenna for the 5GHz band.
  • In both bands, Antenna A and B are used for Tx and Rx.
  • In both bands, Antenna C is used for Rx only.

 

Access Point (External)

ap-outside

 

Access Point (Internal)

img_0183

img_0165

img_0167

 

Access Point System Board

img_0181

 

Radios

radios

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img_0179

img_0174

 

Connectors and cables

radio-to-antenna

img_0169

 

External Antenna

When designing Wi-Fi, you have a plethora of external antenna to choose from.
The antenna you choose will depend upon the requirements, which include the environment, coverage and density needs.

Choosing the right antenna based on the requirements is key.

A great document from Cisco lists their external antennas.
In this document you’ll also get some good explanations on how different types of antenna work and their radiation patterns.

Cisco Aironet Antennas and Accessories Reference Guide

The environment this AP came back from was a large space with high ceilings. Dipole antenna were used:

2.4GHz – AIR-ANT2422DB-R
2.2dBi Omnidirectional Dipole

external-antenna-2-4

 

5GHz – AIR-ANT5135DB-R
3.5dBi Omnidirectional Dipole

external-antenna-5

 

RP-TNC Connector (Female)
External antenna use female RP-TNC type connectors which screw on to the access point.

rp-tncf2

References

Cisco Aironet 3500 Series Access Point Data Sheet
Getting Start Guide for Cisco 3500 Series Access Points
Cisco Aironet Antennas and Accessories Reference Guide
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