Dead Spots and Slow Zones

Many users of Wi-Fi experience poor connectivity and slow speeds. In one room it doesn’t work at all, and in another the speeds may crawl. To achieve a dependable wireless connection, Wi-Fi has to overcome many barriers and obstacles – some of which can’t be fixed by purchasing a newer wireless router.

Diminishing Signal Strength:

A high signal strength measurement is quite often a good indicator that the Wi-Fi connection will be fast and reliable instead of slow and intermittent. We can compare this to hearing other people talk– in a quiet, open area, you can hear someone’s voice fairly well. On the other hand, in a building with thick walls, listening becomes increasingly more difficult. The same is true for indoor Wi-Fi. As distance increases, the wireless signal strength decreases, and different types of walls and other obstructions will further impede the signal strength

Wi-Fi Signal Strength Loss From Indoor Walls

Wi-Fi Signal Strength Loss From Indoor Walls

Free Space Path Loss With No Attenuation from Walls

Free Space Path Loss With No Attenuation from Walls

This example shows what Wi-Fi signal strength would look like with and without building walls. The red colors represent a signal strength too low for good Wi-Fi connectivity.

Use the following guidelines to gauge how different materials in your home affect the signal strength of Wi-Fi. Keep in mind that a 3 dBm drop is equivalent to a 50% reduction in power!

  • Dry Wall: 3 dB
  • Hollow Wood Door: 4 dB
  • Brick Walls: 6 dB
  • Concrete: 8 dB
  • Refrigerator: 19 dB

What To Do:

Changing the location of a wireless router can improve the speed and connectivity for most users. You should try to put the wireless router in a more centralized location.

Take that Wireless Router out of the cabinet in the laundry room and find the right spot for it!

  1. Decide which rooms need Wi-Fi the most and measure their signal strength using inSSIDer for Home
  2. To improve the signal strength for every room, find a central location for the wireless router with as few brick walls and metal objects in the way as possible.
  3. Verify you’re getting higher signal strength with inSSIDer for Home.

Slow Zones from Competing Networks

Slow connectivity in an area can be caused by competing networks on the same or overlapping channel. When a Wi-Fi channel has a lot of active users on several networks, the speeds decrease for everyone. Unfortunately, the channel doesn’t belong to just you, and you can’t stop other networks from using it.

Your best option is to use a channel with no overlapping networks or share a channel that has networks with low signal strength. There are two types of Wi-Fi interference that can slow you down:

Co-Channel Interference – Networks sharing a channel cooperate and take turns talking. Channel bandwidth is shared between every Wi-Fi device.

Overlapping Interference – Networks on non-standard or overlapping channels are unable to cooperate, and will cause interference on neighboring networks. They share bandwidth with networks on standard channels.

Network Strength compared to Co-Channel and Overlapping Interference

Network Strength compared to Co-Channel and Overlapping Interference

inSSIDer for Home’s algorithm only measures the signal strength of a single wireless router and assumes each competing network is equally active. (For more accurate interference assessments, you will need to use more advanced tools like Spectrum and Packet Analyzers).

To avoid Wi-Fi slowness, find a channel that has the least amount of co-channel and overlapping interference. That means you want the fewest networks to be on your channel – and if they are, you want them to be relatively quiet (lower signal strength).

What To Do:

This exercise assumes you have already found an ideal central location for your wireless network. It also requires you to know how to configure and change the channel of your wireless router. If you do not know how, please consult your user manual.

inSSIDer for Home will display a link score for your network, which is a number that accounts for signal strength as well as the level of co-channel and overlapping interference. The Link Score is an estimation, and it assumes that each network is equally active.

Follow these steps to find the best channel:

  1. Use inSSIDer for Home to measure the link score in each room.
  2. Try channel 1, then 6 and 11 of your wireless router
  3. Measure the link score in each room.
  4. Choose the channel with the best aggregate link score for each room.

Dead Spots from Non-Wi-Fi devices

Sometimes you may have excellent signal strength, but little to no connectivity. These dead spots can be caused by competing wireless devices that use the same frequencies as Wi-Fi, but do not cooperate with Wi-Fi. Here are a few common devices that cause dead spots in the home:

  • Cordless Phones
  • Baby Monitors
  • Wireless Audio Systems
  • Nanny Cams
  • Microwave Ovens
  • Wireless Security Systems
Wi-Fi Networks experiencing from Non-Wi-Fi Transmitters

Wi-Fi Networks experiencing from Non-Wi-Fi Transmitters

Interference from Non-Wi-Fi Transmitters as displayed by a Wi-Spy Spectrum Analyzer

Interference from Non-Wi-Fi Transmitters as displayed by a Wi-Spy Spectrum Analyzer

Many wireless devices have an auto-channel selection algorithm in order to provide a better connection, but this can cause more headaches than it solves. Auto channel selection is blind to non-Wi-Fi sources, and makes its selection only on the number of interfering networks sharing the same channel. It may also put your wireless network on a non-standard channel, which introduces even more interference from multiple sources. In the end, auto channel selection does not solve any problems. If anything, it makes the problem more intermittent and extremely difficult to troubleshoot.

What To Do:

Without a Spectrum Analyzer it is difficult to definitively conclude anything regarding non-wi-fi interference. Learn more about Spectrum Analysis.

The following steps will help you systematically test other wireless devices for Wi-Fi interference:

  1. Download TamoSoft Throughput Test Utility, and install it on two computers
  2. Set up the first computer as a Server, and the second as a Client
  3. Begin the Test
  4. Turn on and use the non-Wi-Fi device in question to see if it affects the performance.
  5. Restart the wireless device to see if it changed its channel. Try this a few times, until you have determined whether or not your Wi-Fi is affected by the device.

The More You Know

Slow zones and dead spots can occur for a variety of reasons. You can avoid these pitfalls by moving your wireless router to a central location and choosing a better channel, which we’ve learned about this this lesson.

Utilizing proper Wi-Fi knowledge and troubleshooting tools as you build out into the future will ensure you are able to identify what may be the root cause of poor Wi-Fi performance. Stay tuned for our next Wi-Fi Tips and Tricks update!

4 comments for “Dead Spots and Slow Zones

  1. WhatIsDisqusWhoAmI
    April 15, 2013 at 5:35 pm

    Great article, thanks guys.

    • Trent Cutler
      April 22, 2013 at 2:22 pm

      you’re welcome!

  2. Judith
    August 12, 2013 at 4:00 pm

    How can you edit the channel? Can’t find in the user guide for Inssider…

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