Introduction:
The document covers the purpose of wireless survey, different types of wireless surveys and their part in planning good wireless network architecture.
Why survey?
The most prominent issues faced in wireless network are slowness and disconnections which are indirectly the impacts of interference and signal overlap. A survey can help us identify all the factors responsible for bad wifi.
What do we achieve?
The purpose of a site survey is to have a solid understanding of the radio frequency behavior on site. It reveals the possible areas of interference and identify any dead zones.
Before implementing or attempting to optimize a WLAN, we have to understand all the possible areas of interference, AP placements, power considerations, and wiring requirements.
Solution:
The long term solution for these issues is properly designing the wireless network.
Three main steps for a good wireless network:
- Site survey
- AP positioning plan
- Post-deployment survey
Three types of survey
- Passive
- Active
- Predictive
Passive:
Passive site survey are those in which surveyed adapters listens to existing access points and other signal sources for signal strength, interference, and access point (AP) coverage. Here surveyed adapters don’t need to associate to the AP/SSID, it just listens to the AP for signal strength, interference, AP coverage and gives a good overall picture of the RF characteristics of existing network.
Commonly used during post deployment surveys and when upgrading existing wireless networks such as adding additional APs.
Active:
During active site surveys the surveyed adapter is associated the AP/SSID and exchanges packets. This allows to gather detailed information on actual network traffic, throughput, packet loss, physical rate, etc.
Commonly performed in conjunction with a passive site survey at start of a new wireless network deployment.
Predictive:
Predictive site surveys are those which are done without any field measurements. All the required measurement values are predicted and heat maps are generated with those values.
Commonly used when the site/building is not yet built and for budgeting purposes.
Benefits of survey:
- Site surveys helps to determine signal coverage in the entire surveyed space.
- Throughput requirements can be studied in the ambiance with a survey.
- Interfering sources which are part of the network and other interfering sources which are not a part of the network (may be an external source eg: microwave oven).
- Site survey assists in identifying the Dead spots where the wireless signal is almost dead (i.e unusable).
- Potential roaming in the network can be determined which helps us in fine-tuning the areas of random disconnections.
- No of Access Points required for the space can be determined with a survey, so that excessive or inadequate number of access point’s complications can be neglected.
- Access Point’s placement which is prominent part of any wireless design can be properly planned with a good survey done in the premises.
- Signal penetration capabilities or attenuation of objects blocking the signal can be identified which is very important source of information in calculating parameters such as interference and number of access points.
- Power setting required on Access Points can be studied by performing a proper survey.
- Channel planning parameters can be considered with a properly managed survey.
- Packet re-transmission rates in the existing network can be preconceived by performing a survey which help in identifying the maximum distance the signal traveled from a particular access point and the capability of the end devices to re-transmit the signal back to the access point.
- Packet loss in the network can be intended by performing a survey while we keep our surveying device connected to the existing wireless network.
- Data rates of the existing network can be determined.
- Channel width of access points in regions can be identified.
- Survey helps us determine RSSI threshold of the devices.
- Signal to Noise Ratio of the environment can be studied.
- Survey helps us identify the Spectrum utilization
- Network capacity of the infrastructure with the existing network devices and design can be identified.
- Most importantly the actual Access point model suitable for the network can be identified.
Conclusion:
Without a wireless survey, small networks such as networks with 2 or 3 access points may work as required but larger networks such as bigger organisation with more than 10 access points will suffer a lot with many issues such as interference, less SNR, lower data rates, too much signal overlap, dead spots, etc which might lead to disconnections, signal drops, slowness and roaming issues. Wireless survey will help us avoid all of these issues.
