Thursday, April 28, 2016
Why is my network so SLOW?
This article hopes to give the average user a simple understanding of how the wireless network (WLAN) works and some key things that affect how fast it is (or not).
There are two key parts to a WLAN… the device (a laptop, iPad, or smart phone) and the access point (AP). The AP is usually connected to the rest of the network by a wire, but communicates with the devices via radio waves. Whenever your device comes near an AP, there is a series of messages exchanged between them that establishes an association between the two that includes the name of the network you want to use (aka the SSID) such as SAD6-Wireless, along with the speed (data rate) of the communications, and any password and encryption that might be used. At this point your device gets a network address (aka IP address).
Your device and the AP chose a data rate based on how strong the radio signal is. Radio signals lose strength just going through the air, but lose a lot of strength going through walls. So, Rule #1: the closer you are to the access point the faster your device will communicate with it. The data rate is important because if you are trying to load a web page that is 1 MB in size, and device #1 has a data rate of 300 Mbps and device #2 is running 100 Mbps, the device #2 will take three times longer to load the same page as the device #1.
The kind of device that you use also affects the signal strength, and therefore the data rate. The stronger the radio transmitter and receiver, the more power it uses. So generally, laptops have stronger radios because they have bigger batteries. Smart phones and iPads have weaker radios, so that they can extend the battery life. So, Rule #2: the WLAN will be faster on a laptop, then it will be for a smartphone or an iPad.
The next thing to remember is that, just like a walkie-talkie, if two or more people key up the microphone and talk at the same time, it all comes out garbled. Well, a WLAN is the same way…. only one device can communicate with an AP at a time. This is known as air time. When you are at home, you are usually the only device using the wireless and you have all of the air time to yourself. But in the classroom, you might have 20 students with a device. So the air time is now shared by the 20 devices. Each device gets a smaller portion of air time. So Rule #3: The more devices using the same AP, the slower the network will be.
A general rule is that more than 25 devices on one AP will result in a slower WLAN. This is not a hard limit, as it depends highly on what each user is doing. But keep in mind that smartphones, iPads, and iPods all connect to a WLAN automatically if they are turned on…. even if they are not being used. So your classroom might only have 20 students with laptops, but if each student also has a phone or iPod, then there are really 40 devices connected to one AP. This will make things seem slower.
So, if you are in the classroom and the WLAN seems slow, just what can you do?
1. If the site you are trying to use seems slow, try a different one. If a different site loads faster, then it
might just be the site that is slow.
2. You can also test the network speed. Open your browser and go to speedtest.net. Press the Begin
Test button. After a few minutes, it will report three numbers. The important numbers are the
upload and download speeds. If you were alone in the classroom, standing right under the AP, you
might see numbers in the 80’s or 90’s. But normally you will see speeds in the 40 to 60 Mbps. If
you see numbers under 20 Mbps, then you can expect that web pages will load slowly.