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WLAN has a major advantage compared to wired communication: You can use your laptop, iphone or android everywhere and don't have to struggle with a cable. Just comare it with wireless and wired phones. There are some disadvantages: WLAN has usually a lower throughput than wired connection. But that's acceptable for normal browsing, eMail processing and chatting. Unfortunately there is another disadvantage: The number of WLAN channels to communicate with the accesspoint is limited. If a neighbour uses the same channel or a channel nearby the throughput of WLAN will decrease significantly.


 There exist 11 (USA) and 13 (Deutschland) channels on the 2.4 GHz Band and 19 Kanäle on the 5 GHz Band. Most of the current WLAN cards can use the 2.4 GHz band only.  The 5 GHz band is new and not pervasie and the cards are more expensive. Don't think now 13 accesspoints can communicate on different channels without any throtteling interferences. Channels interfere if their frequency distance is too small. This means channels have to have a distance of at least  5. Therefore you find the suggestion to use channels 1,6 and 11 only.

In summary this means there are only 3 channels available for accesspoints near your house to work without any interferences. Therfore you should check which channels are used by your neighbours accesspoints and find a channel with the least number of overlapping channels with channels used by neighbours. There exist various tools on Windows (2,3) and some tools on Linux (4). The Linux tools are not that comfortable to use and don't have a nice GUI. But there exist a  standard tool on LInux which can be used to find out which channels are not used:
Just type in the command window
iwlist wlan0 scan | egrep -i "(essid|channel)"
and you get a list of SSIDs and channels which are used by accesspoints by you and your neighbour. Now find your SSID and channel used and compare it with the other SSIDs and their channels.
If you execute this script in a command line you will get a consolidated result of iwlist analyzed for WLAN channel interferences and prints a list of channels which should be used. An example ouput will look like
WLAN channel analysis for SSID 'MyESSID' using channel 6 on wlan0

Channels | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | SSIDs
    1     *01**--------->                                                   Channel1
    2     <----*01**--------->                                              OverlapChannel2
    4          <---------*01**--------->                                    BorderChannel4
    5               <---------*01**--------->                               InbetweenChannel5
    6                    <---------*02**--------->                          * MyESSID, SameChannel6
    9                                   <---------*01**--------->           OverlapChannel9
   13                                                       <---------*01** Channel13

SSIDs with identical channel    : 1 SameChannel6
SSIDs with overlapping channels : 4 BorderChannel4, InbetweenChannel5, OverlapChannel2, OverlapChannel9
Sum of detected SSIDs           : 8
Minimal overlapped channels     : 12

*** Switch your access point channel from 6 to an optimal channel 12
Latest WLAN routers do have the function to scan all WLAN channels for their usage. Some of them switch the channel when they detect the channel is used by too much accesspoints.
Even if the channels don't overlap there can be interferences (1) .
(4) Kismet - Linux Tool 
(2) inSSIDer - Windows Tool 
(3) stumbler - - Windows Tool 
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