Wifi Wireless Network

    This page explains the setup and configuration of my home wireless network.  I discontinued my contract with my ADSL ISP because they were pirates but that's a rant better left for another time.  A neighbor agreed to give me access to his wireless network and I would pay him a small amount every month.  This is not only cheaper for me but I also avoid having to deal with the ISP pirates. 
    I have several computers and, rather than connect each computer directly to the neighbor's network what I have done is keep my network separate and connect my own network to the neighbor's network which is the gateway out to the Internet.  This has several advantages, as we shall see.  The first advantage is that I have not had to change the configuration of any of my computers which remain connected to the same network as before.  My network continues to work as before, with all my computers interconnected and with a common gateway out to the Internet.  No need to reconfigure each computer's network connection.  Also, my network is totally separate from the neighbor's who has no access to my network or my computers. 
    Before we go any further I want to clarify the nomenclature.  A wireless network has two kinds of complementary devices.  We have access points (AP) to which clients connect.  A client can connect with only one AP at a time but several clients can be connected to one AP. 
    Normally we would have a device which includes three different things: ADSL modem, router and access point.  The access point and router and be used separately from the modem.  There are devices which are solely access points and some can be configured as clients (but you have to be sure because I bought a Linksys WAP54G believing I could use it as a client but it does not work that way).  Wireless clients which plug into USB ports are commonly called "wireless USB adapters" and clients which use ethernet are sometimes called "wireless bridges" although this is misleading.  There is some confusion and you need to clarify and be sure of the capabilities of each device.
    Having separate networks means being able to set different permissions, access, resources, etc.  This is useful in my case but can also be useful for households which have a separate network for the children or similar situations.  For instance: My LAN (192.168.0.X) -> Neighbor's LAN (192.168.1.X) -> Internet
Children's LAN -> Main LAN -> Internet
    This way my packets have to go through the neighbor's LAN to go out to the Internet but we are still on separate networks and the neighbor has no access to my network.  The following graphic illustrates this.  The parabolic reflectors on the wireless antennas improve the quality of the link and extend the range. 

    In my particular case I have a combined router / access point TP-Link WR340G while the wireless-ethernet adapter client which connects to the neighbor's wireless network is a Sparklan WCM100 which I bought on eBay quite cheaply and which works surprisingly well.   Unfortunately I have not been able to find another one to have as a backup.  Wireless to ethernet adapters (clients) tend to be rather expensive because wireless to USB is what most people use and they are much cheaper but an ethernet client can be connected directly to the router which cannot be done with a USB unit.  This way the computers an be connected to the router using ethernet which is simpler and more stable. 
    Some access points can also be configured as clients or bridges but there is some confusion in this terminology and both words do not describe the exact same thing.  What we need is, strictly speaking, client mode.  What I have not found, and it is a pity, is an ADSL-router-access point where the access point could be configured as a client.  This would be really good because I have several of these units unused.  All these devices implement their firmware using Linux and it would probably be possible for someone with the necessary knowledge to modify the firmware so the wireless part could function as a client. 
    One advantage of my setup is that the access point - router - client combination act as a repeater which greatly extends the range compared to connecting to the neighbor's wireless directly.  My computer is located at one end of the building and the neighbor's access point is located at the opposite end of the building and one floor down.  With many thick walls in the way my computer could not directly connect to the neighbor's wireless network but with the wireless router placed half way there is never any problem connecting because it acts as a repeater. 
   Parabolic antenna reflector
    To improve the quality of the connection I tried fitting the antennas with parabolic reflectors and the improvement is quite noticeable.  Not only does the focused signal improve but others which caused interference are now out of focus and weakened. 
    it is easy to find instructions on the Internet to build a parabolic reflector but it is very easy and I did it on my own just by drawing the parabola to my own size. . I drew the two parabolas on cardboard from a cereal box and left some tabs around the edges to secure the reflector later.  At the focal points I cut holes through which the antenna would pass.  This was a quick-'n-dirty experiment and it worked well but after some time the cardboard started curling and sagging, especially affected by humidity.  If you want something durable which will stand up to time and weather then you might want to use PVC or other plastic. 
    I glued some aluminum foil over the cardboard which would be the reflector and then secured it to the parabolas.  The aluminum foil is a bit wrinkled but still works.  probably a better result would be obtained using aluminum or other metal sheet with plastic parabolas to give it the correct curvature.  For quick experiments any metal foil will do, including juice or milk containers made with plastic and metal film.  Pretty much anything can be made to work, the main consideration is how durable you want it to be. 
    By placing reflectors on both antennas of a link and have them facing each other the range and quality are improved considerably but even placing a reflector only in one of them the quality and range improvements will be noticeable. 
    You can find on the Internet projects for the building of wifi directional antennas but they require modifying the electrical part which carries certain risk while parabolic reflectors are very simple and require no modification of the electrical parts. 
    Most wifi signals are polarized vertically because most access points have their antennas placed vertically.  This means the link will be better if the client's antenna is also placed vertically.  If the client's antenna is placed horizontally we can see the signal loses power and the link quality degrades.  In general terms it is best to place the access point antenna vertically because this radiates mostly in the horizontal plane which is where the clients will be located.  Much less power will be radiated upwards or downwards.  This is the best design when clients will be randomly located in the same horizontal plane. 
    But is our aim is to improve communication in one single direction we can place the antennas horizontally which helps filter out other wifi signals which have vertical polarization and which could cause interference. 
    If we want to optimize the link between two wifi antennas we should:
1- Place the antennas so there is a minimum of obstacles directly between them.
2- Position the antennas parallel to each other and perpendicular to the line that links them.
3- Position the antennas horizontally in order to minimize interference from other sources.
4- Provide parabolic reflectors mutually oriented.