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To better understand WiFi Speeds and SpeedTest results Please Read This:

Performance (speed)
Most people want to know how fast their internet is, and their first surprise after testing is that they're not getting the speeds their ISP says they should be getting, or that the speeds seem low. WAP's (Wireless Access Points or routers) are slower to start with, may not use their fastest speed, and on top of that, have higher overhead (overhead degrades speed) than the routers used for the internet connection alone. Most WAP's only specify their highest speed rate (also called bitrate). The speed rate is the speed the bits are send over the air (802.11b is up to 11mbps, 802.11g is up to 54mbps, and 802.11n goes up to 100mbps) but those speeds do not account for all the overhead of the various protocols.

Wireless protocols have multiple rates (b, g and n) and adapt the signalling rate depending on the quality of the link (for example 802.11b can run at 1, 2, 5.5 and 11 Mb/s). When the link is clear and reception is strong (i.e. when you're standing in the room with the WAP), the WAP uses the fastest rate, but when there is interference or the WAP's are further away, it downgrades to a slower, more reliable rate. The throughput that you will get will depend on which rate you are using. For example the highest speed might be only usable within line-of-sight. Environmental conditions constantly change so most WAP's adjust their rate continuously, and the throughput (speed) can be unpredictable.

The WAP protocols also have a much higher overhead than their wired counterpart (i.e. ethernet) because of technological limitations and to improve the reliability and the coverage of the WAP (called optimization trade-off's). Wireless protocols have a lot more protocol overhead, such as contention, large headers, encryption, management frames. Retransmissions are needed to overcome various radio conditions (walls, garage door openers, baby monitors, microwaves, Smart TV's, etc.). Part of the protocol overhead is fixed and does not scale with the bit rate, which means that at the highest rate this overhead is becoming proportionally larger. Because of all this added overhead throughput can be reduced by 50% or more.

As said earlier, people get excited about speed, and they often don't realise that the main measure of performance of a WAP is the coverage and not the speed, and by a wide margin. This includes maximum distance between nodes, resistance to interferences, and the ability to maintain connectivity in a wide range of conditions.
The propagation of radio transmissions is influenced by many factors. Walls and floors tend to decrease and reflect the signal, and background frequencies (microwaves, garage door openers, etc.) make it more difficult for the radio signals to populate (i.e. interference). The channel quality can vary quite a lot depending on the distance from the WAP- what is called fading.

Depending on the quality of reception, the error rate will change (forcing packet retransmissions), or the system may switch to a more robust (and slower) mode to account for fragmentation or modulation or both, so the actual throughput will vary from good, to fair, to bad.

Because of the way radio transmission are affected by the environment, it is difficult to predict the condition of your system and to define a range. You will have some good, fair and bad areas- period. The closer you are to the WAP the more likely you are to have the best results.

What is the coverage area of a WiFi signal within the home?
The wireless signal of a standard Wireless Access Point (WAP) will cover a radius of 150 feet using 20db (decibels) of power in the home or office environment but you must deduct 50 feet for every wall the signal passes through. Beyond 150 feet wireless signal strength will become weaker and data rates will drop. Actual performance may vary depending on the conditions at the location where the Access Points are installed. There are newer Long Range Access Points (LR WAPs) that can cover 300 feet but you still need to deduct 50 feet per wall. You may need more than one LR WAP to get the best coverage.
Here are the signal losses from typical homes/businesses. Remember that WAP's start out at 20db of power which can cover 150 feet of open space but lose decidels according to the list below:

Human body 3
Cubicles 3 to 5
Window, Brick Wall 2
Brick Wall next to a Metal Door 3
Glass Window (tinted) 3
Clear Glass Window 2
Office Window 3
Plasterboard wall 3
Marble 5
Glass wall with metal frame 6
Metal Frame Glass Wall Into Building 6
Metal Frame Clear Glass Wall 6
Metal Screened Clear Glass Window 6
Wired-Glass Window 8
Cinder block wall 4
Dry Wall 4
Cinder Block Wall 4
Sheetrock/Wood Frame Wall 5
Sheetrock/Metal Framed Wall 6
Office Wall 6
Brick Wall 2 to 8
Concrete Wall 10 to 15
Wooden Door 3
Metal door 6
Metal Door in Office Wall 6
Metal door in brick wall 12 to 13

Note that each time the WiFi signal goes through one of the above you must deduct the loss, and then the next, and so on. A typical WiFi Access Point (WAP) transmits 20dB of power so as the signal passes through the above in your home or office deduct the loss and soon you will see why you may need more than one WAP. Once a WAP is at about 10db the speed is very slow due to the reasons stated previously and especially retransmissions.
Using the above can also help you with WAP placement in your home or office.

How to properly perform a Speed Test?

The speedtest allows you to measure the speed of downloading and uploading data, as well as the delay in the transmission of packets (latency). The test results are shown in megabits per second (mbps). Before running the test remember to close all applications running on your PC or MAC.

This is AT&T's Speed Test server, which is a free, public, speed test server.
You do not need to fill in your email address on the next page. Simply click Start Test:

or you can use this speed test server:

Both these speed test sites are "public" and sometimes they get overloaded by people testing their speeds which can cause some wild discrepancies in results. Please test a few times and at different times of the day to obtain a more accurate result.

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