Documenting existing network characteristics

  • Quite often the reason you are conducting a WLAN site survey is that you have been called in as a consultant to fix an existing deployment.
  • What are the current problems with the existing WLAN?
    • Are they throughput related?
    • Are there frequent disconnects?
    • Is there any difficulty roaming?
    • In what part of the building do the problems occur most often?
    • Is the problem happening with one WLAN device or multiple devices?
    • How often do the problems occur, and have any steps been taken to duplicate the troubles?
  • Are there any known sources of RF interference?
    • More than likely the customer will have no idea, but it does not hurt to ask.
    • Are there any microwave ovens?
    • Do people use cordless phones or headsets?
    • Does anyone use Bluetooth for keyboards or mice?
    • After asking these interference questions, you should always perform a spectrum analysis, which is the only way to determine whether there is any RF interference in the area that may inhibit future transmissions.
  • Are there any known coverage dead zones?
    • This is related to the roaming questions, and areas probably exist where proper coverage is not being provided.
    • Remember, this could be too little or too much coverage. Both create roaming and connectivity problems.
  • Does prior site survey data exist?
    • Chances are that an original site survey was not even conducted.
    • However, if old site survey documentation exists, it may be helpful when troubleshooting existing problems.
    • It is important to note that unless quantifiable data was collected that shows dBm strengths, the survey report should be viewed with extreme caution.
  • What equipment is currently installed?
    • Ask what type of equipment is being used, such as 802.11a (5 GHz) or 802.11b/g (2.4 GHz), and which vendor has been used.
    • Is the customer looking to upgrade to an 802.11n or 802.11ac network?
    • The customer might have no idea, and it will be your job to determine what has been installed and why it is not working properly.
    • Check the configurations of the devices, including service set identifiers (SSIDs), WEP or WPA keys, channels, power levels, and firmware versions.
    • Often issues can be as simple as all the access points are transmitting on the same channel or there is a buffer issue that can be resolved with the latest firmware update.
  • Depending on the level of troubleshooting that is required on the existing wireless network, a second site survey consisting of coverage and spectrum analysis will often be necessary.
  • After the new site survey has been conducted, adjustments to the existing WLAN
    equipment typically are adequate.
  • However, the worst-case scenario would involve a complete redesign of the WLAN. Keep in mind that whenever a second site survey is necessary, all the same questions that are asked as part of a survey for a new installation (Greenfield
    survey) should also be asked prior to the second site survey.
  • If wireless usage requirements have changed, a redesign might be the best course of action.
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