Implementing Wi-Fi Successfully
From the installation, to the configuration and monitoring, there are many things to keep your eye on with Wi-Fi implementations.
Many think of implementing a Wi-Fi network as easy because they did it at home. The home installation has far fewer problems and considerations when compared to an enterprise installation covering offices and work areas.
In my previous blog, Wi-Fi Planning: Do It Right the First Time, I discussed the planning process and the questions that need to be addressed. In this blog, I will take a closer look at the installation, configuration, and monitoring of the Wi-Fi installation. The inspiration for this blog was a one-day seminar on Wi-Fi I attended that was put on by Adtran, a provider of telecommunications networking equipment and internetworking products.Installation Recommendations and Requirements
If you have performed an adequate Wi-Fi network design, then you need to install the access points (APs), arrange the channel assignments, and adjust the power settings. Position the antennas for maximum coverage. Install the APs above room furniture and office partitions. If the AP is on the ceiling, make sure that the antennas point downward. By properly grounding the APs, you reduce the noise level that interferes with the APs. Grounding is especially important if the APs are outdoors.
The ADTRAN seminar provided some tips on ensuring that your onsite survey is accurate:
- Calibrate the site drawings accurately. Guessing is not enough. Think of it as a drafting project.
- If you test in advance, ensure you use the right frequency(s), 2.4Ghz and/or 5 Ghz.
- Perform a signal propagation assessment. Your signal reach may be shorter than anticipated.
You will be cabling to the APs. Allow 20 to 30 ft. of extra cabling especially for ceiling installations. It is unlikely that you will use 802.11b, therefore disable this function. When you name and locate the APs, use the building and room numbers combined with a visual setting (on the ceiling or the wall next to room #xx). Logical names will still have to be translated in real locations. Save the time involved in locating APs by using descriptive names.Design Validation and Verification
You may have confidence in your or your VAR's design, but you will not know how well it works until you try it.
- Perform an active and passive site survey after installation.
- Verify the signal coverage and the throughput available throughout the site.
- Use some of the customers' devices to spot check the deployment.
- Look for electronic noise producers. The Wi-Fi signal to noise ratio should exceed 20dB.
- There are co-channels in Wi-Fi. They can interfere with each other, thereby reducing the number of simultaneous users.
- Don't verify through doorways; test through the walls.
- Test inside and outside the rooms and building. Let the test run for a minute or more to stabilize the measurements.
- Don't skip any location that will or may have a user device. Stairwells are usually missed. A user may walk in the stairwell or closet with their laptop, tablets, or phone and lose a connection.
- Validate that the signal strength, signal-to-noise ratio, and interference areas are designed to satisfy.
- When verifying the installation, think of what a user would do, not what they should do.
- Go back and alter the design to compensate for any discovered problems.
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It is uncommon that the initial installation is the final configuration. The materials of the walls and the furniture may be inaccurate or some of the furniture, like metal cabinets may have been moved. The plasterboard wall may actually be covering a concrete or cinder block load bearing wall.
The wireless needs of the users can change. Offices and rooms may be modified. The number of users could increase or decrease or change their locations.
Interference can change. New wireless Internet of Things devices may be added for environmental control or security that use the same frequencies as Wi-Fi. Wireless devices transmit lower power signals at two to four times their normal frequency range, creating harmonics and thereby causing interference for Wi-Fi signals.
A spectrum analyzer is a device that captures and displays raw RF signals both in and out of the Wi-Fi frequency range. The analyzer displays the competing signals in the Wi-Fi signal spectrum. The spectrum analyzer is probably not worth buying unless there are a number of Wi-Fi deployments planned. The analyzer could be provided by a consultant or VAR for temporary use.Troubleshooting the Network
Wi-Fi networks cover the bottom two layers of a network. Layer 1 is the RF medium. Layer 2 is the data link layer. You need to troubleshoot each separately. For Layer 1, RF medium tools include Wi-Fi scanners and spectrum analyzers. These tools can detect other devices using the same frequencies as Wi-Fi such as cordless phones and detect interference.
Layer 2, the data link layer, generates and transports the data packets. The main function is successful packet delivery, detect and correct transmission errors, and retransmit lost packets. Layer two is a version of Ethernet protocol designed for wireless operation. This version acknowledges the packets. The error and packet loss are far greater with Wi-Fi than on cat 5 and 6 cable or fiber. The packet loss can be as high 30%. The end result is that the useful Wi-Fi speed is about half the rated speed. A protocol analyzer is the tool to use for diagnosing layer 2 problems.