It will be assumed the objective is to extend one home LAN to a second house that is a few km away - up to 25km. This creates one virtual Local Area Network (LAN), spread over two houses. If one of those has an Internet connection, then PCs in both houses will be able to surf the Internet via the one shared Internet connection.
You will need at each house:
- Externally mounted antenna
- A WiFi 'radio'
- Connection between radio and home LAN
- A high quality cable connecting the antenna to the radio
Each of these is discussed below.
(1) EXTERNALLY MOUNTED ANTENNA
Because of the distance, you will need a pair of high gain antennas. The question is: How high? To answer that, the first big question is: Will there be Line Of Sight (LOS) between the antennas? LOS implies that on a very clear night, a strong light at one antenna location would be seen with binoculars at the other location. That means: no trees, no hills, no buildings. In the cases below, I am assuming 802.11b equipment (11 Mbps) with a 30mW transmitter (most are this or better). If you are using a stronger transmitter, you MAY get by with smaller antennas. If you are using 802.11g (54 Mbps) add 12 dBi to the combined gain, as 802.11g needs a stronger signal to go full speed.
Case 1: LOS = Yes.
This is easy. The combined gain of the two antennas must be:
0-1 km = 12 dBi combined (eg two 6 dBi antennas, eg BRICK)
0-4 km = 24 dBi combined (eg two 12 dBi antennas, eg AntCap)
0-25km = 38 dBi combined (eg two 19 dBi antennas, eg Parabolic)
Case 2: LOS = 'A few straggly trees in the way'
Hard to say. You can assume that if you use the "LOS = YES" guidelines, that you will get either no link, or a lower than full speed link (eg 1 Mbps instead of 11 Mbps). So, best to use stronger antennas. The table below MAY work in your case.
0-1 km = 24 dBi combined (eg two 12 dBi antennas, eg AntCap)
0-4 km = 38 dBi combined (eg two 19 dBi antennas, eg Parabolic)
0-25km = 50 dBi combined (eg two 25 dBi antennas, eg Satenna)
Case 3: LOS = 'Lots of trees in the way'
Buy a new house, build a huge mast, or find a 3rd person whose house CAN see the two original houses and relay via that house.
(2) WIFI RADIO
There are many radio options - all of which can be used.
- Stand-alone Access Point (AP). An AP can be thought of an ethernet wireless modem.
- PCI card. Careful - as you want to keep the antenna cable short, this limits where the PC can go.
- USB 'client'. Careful - USB cable lengths are limited, so this limits how far the PC can be from the antenna.
The most flexible recommendation is to use a pair of STAND ALONE APs, that can talk to each other.
Just make sure that whatever WiFi radios you choose for the two ends of the link, that they have these properties:
- detachable antenna
- can communicate with the WiFi radio across town. As it is always a good idea (but not required) to use a pair of identical brand/model WiFi radios at each end of the link, look for APs that support 'Client or Station' mode, and/or 'Bridge' mode.
(3) CONNECTION BETWEEN RADIO AND HOME LAN
It is assumed you have a home LAN! Usually this is a network of PCs/Printers - wired together via CAT5 ethernet cables and a HUB or SWITCH (which may be built into the back of a broadband Internet router).
If you buy a stand alone AP, this is very easy: simply run some standard CAT5 ethernet cable between the AP and the home LAN.
If your radio plugs into a PC (eg. PCI or USB), then you will need to route/bridge through your PC to connect the LAN and the wireless together. That is beyond the scope of this tutorial.
(4) ANTENNA CABLE
As a rule, you should always minimise the length of the cable between the radio and the antenna. 3 metres is usually OK for typical antenna cables. Up to 10-15m is possible, but higher quality cable (more $$$) is required. If you have purchases a stand alone AP, then you have the option of locating the AP in the dry roof space, and running a short cable to the external antenna, and a long CAT5/Ethernet cable to the home LAN....and this is the recommended way of doing things.
