How to Build a Wireless Network Without Using a Broadband Router

Introduction
A lot of people don’t know that if you run Windows XP or Windows Vista it is possible to build your own wireless network at home or office without using a wireless broadband router or a wireless access point, saving some bucks. In this tutorial we will show you step-by-step how to build this kind of wireless network, also known as ad-hoc.
More and more people are willing to assemble their own wireless network. With a wireless network set at your home or office, you will be able to share files, use the printer and access the Internet without the need of connecting a network cable to your computers. This is great if you have desktop computers located in places where is hard to install a network cable or if you want to have the freedom to access your network and the Internet using your laptop anywhere inside your home or office: you can carry your laptop from your bedroom or office to your living room and it will still be connected with no cables attached.
Of course we are talking about laptops with wireless network capability – all new laptops have this feature. If you are using desktops or laptops without wireless capability, you will need first to buy a wireless network card for each computer you want to connect to your network and to the Internet wirelessly.
In order to build your own wireless network you will need the following:

• A broadband Internet connection;
• A wireless network card installed on each computer that you want to connect to your wireless network;
• A wireless broadband router (optional).

Usually a piece of hardware called wireless broadband router or access point is required. In this tutorial we will teach you how to setup a wireless network without this device, allowing you to save some bucks. However, you need to know beforehand what are the disadvantages of not having a wireless router:

• The only encryption scheme supported in Windows XP is WEP, which is not secure: a hacker with the right knowledge can have access to your network. Thus if you are building      an ad-hoc network the way we are describing the host computer (the one with the Internet connection) must be running Windows Vista or greater so you can enable WPA2, which is a secure encryption system. The client computers can be running Windows XP, this requirement is only for the host computer.
• The computer that has the broadband Internet connection will need to be always turned on. If you turn it off the other computers will lose their connection to the Internet.
• Your network will be less safe, as broadband routers integrate a hardware-based firewall.
• Your network speed will be limited to 11 Mbps, even if you only use 54 Mbps or faster cards on your network.

You can also configure an ad-hoc network even if you already have a broadband router without wireless capability. If this is your case, please forget about the second item listed above, but the other items will still be true. Also, there is something very important if you have a broadband router already installed on your network: you will need to change the IP address range of your network if it is configured to use the 192.168.0.x range to 192.168.1.x because the Windows Internet sharing service also uses the 192.168.0.x range and you will have conflicting IP addresses on your network. This configuration is done by entering the router’s setup program (usually by opening http://192.168.0.1 from any computer connected to it).

Wireless Network Cards

As we mentioned, you will need to buy one wireless network card for each computer that you want to connect to your wireless network. Wireless network cards are compatible with at least one IEEE 802.11 protocol. There are several protocols and the most common are IEEE 802.11b, 802.11g, 802.11a and 802.11n. From now one we will refer to these protocols simply as b, g, a and n, respectively. The main difference between them is speed: b can transfer data up to 11 Mbps, while g and a can transfer data up to 54 Mbps (the difference between g and a is the frequency of the spectrum that they operate). IEEE 802.11n allows several different speeds starting from 65 Mbps and going all the way up to 600 Mbps. The actual speed depends on the number of antennas, the frequency from the spectrum used and the channel size. The most common speeds for this standard are 130 Mbps, 150 Mbps, 270 Mbps and 300 Mbps, and both the router and the wireless cards must be compatible with the intended speed.
Some network cards are rated as 108 Mbps, but they are in fact 54 Mbps cards using data compression technique and in order for them to achieve this speed your broadband router and the card installed on the computer must have this technology and must be from the same manufacturer, otherwise they will work as a regular b, g or a card. This technology doesn't work on ad-hoc networks, i.e., networks not using a broadband router.
In theory the best scenario is to have all your computers using 54 Mbps or faster cards. However, you are limited by the speed of your Internet connection. So if you don’t use your network for transferring files between the computers, buying 54 Mbps cards doesn’t make sense, simply because the speed of your Internet connection will be far lower. For example, if you have a 1 Mbps connection, you will have a network capable of transferring data 54 times faster than your Internet connection. An 11 Mbps network will work just fine for you (and it will still be 11 times faster than your Internet connection). So you can save some bucks buying 11 Mbps cards – they will work just fine for the average user. Also, ad-hoc networks are not capable of transferring data above 11 Mbps, so using 54 Mbps cards on this type of network is simply a waste of money. If you really want to have 54 Mbps (or faster) capability, you will need to build your wireless network using a router.
Just to clarify, if you have a 1 Mbps or even a 2 Mbps Internet connection, you will still navigate at this speed using 11 Mbps or 54 Mbps wireless cards.
If even with our tip you decided to buy a 54 Mbps or faster wireless card, make sure to buy one that is compatible with 802.11b standard, so you can build your wireless network without using a router, since ad-hoc networks only work at 11 Mbps. It is also interesting that you buy all cards using the same 54 Mbps standard (a or g), so if in the future you decide to upgrade your network by installing a wireless router all cards will be capable of transferring data at 54 Mbps.
There are two types wireless network cards available: USB and add-on. Usually add-on cards are more stable. Add-on cards for desktops are provided for the PCI slot (and probably for the PCI Express x1 slot in the future) and add-on cards for laptops are provided for the PC Card (a.k.a. PCMCIA) slot or for the Express Card slot. If your laptop does not have an embedded wireless card, you will need to check whether it has an expansion slot  (PC Card or Express Card) and buy one add-on network wireless for it (PC Card will probably be the choice, as Express Card slots also accept PC Card devices).
In Figure 1, you can see a PCI add-on wireless network card for desktops, in Figure 2 a USB wireless network card, which can be used by desktops and laptops, and in Figure 3 a PC Card add-on wireless network card for laptops.

Figure 1: A PCI add-on wireless network card.

Figure 2: A USB wireless network card.

Figure 3: A PC Card wireless network card.

The installation of the card should be done following the card manual. Usually it is very simple step: just connect the device to your computer (if you are installing a PCI card on a desktop computer, you will need to turn it off and open its case), turn it on and install its drivers.
Just a tip, with our PCI card portrayed in Figure 1 (a D-Link DWL-G510) we needed to install the drivers before installing the card to the PC.
Install the wireless network card to the computers that will be connected to your wireless network. The next step is configuring the host computer, i.e., the computer that has the broadband Internet connection. If you are sharing your Internet connection using a regular broadband router (i.e., without wireless capability) any computer connected to the router can be configured as host. In this case just remember what we’ve said earlier: you will need to change the IP address range of your network if it is configured to use the 192.168.0.x range to 192.168.1.x because the Windows Internet sharing service also uses the 192.168.0.x range and you will have conflicting IP addresses on your network. This configuration is done by entering the router’s setup program (usually by opening http://192.168.0.1 from any computer connected to it).

Configuring The Host Computer

Now you will need to configure the host computer, i.e., the computer that has the broadband Internet connection. As explained in the introduction, Windows XP supports only WEP encryption, which is very weak, so the host computer needs to be running Windows Vista or greater in order for you to enable WPA2, which is a secure encryption method. You can, at your own risk, build your ad-hoc network using a host computer running Windows XP, but don't get back to us complaining that your network got hacked. This requirement is only for the host computer. Client computers can run Windows XP without any security risk.
If you are sharing your Internet connection using a regular broadband router (i.e., without wireless capability) any computer connected to the router can be configured as host, as long as it is running Windows Vista or greater. As we already mentioned, you cannot turn off this computer or all other computer will lose access to the Internet.
The step-by step to configure the host computer using Windows Vista is as follows. 
1. Go to Start menu, Control Panel, Networking and Sharing Center. On the window that will show up, click on the item "Manage Wireless Networks" present on the menu on the left-hand side.
2. The window shown in Figure 4 will appear. You need to click on "Add".

Figure 4: Managing wireless networks.

3. The menu shown in Figure 5 will appear. Choose "Create an ad hoc network".

Figure 5: Choose "Create an ad hoc network".

4. On the next window simply click on "Next".

Figure 6: Click on "Next".

5. Now Windows Vista will ask you the properties of the network you are creating (see Figure 7). You will need to fill out the following:

• Network name: This will be the name of your network. This is how your computers will call your network. In our case, we called our network “Gabriel.” We suggest you to use a specific name instead of a generic one (e.g., your name or your business name), so you will be able to easily recognize your own network from the list of available wireless networks.
• Security type: Select "WPA2-Personal".
• Security key/Passphrase: Users willing to connect to your network wirelessly will need to configure this key (think of it as a password to access your network) on their computers. You need to create a random key containing 63 alphanumeric characters. It can be shorter, but we don’t recommend. Just go crazy pressing random characters on your keyboard, don’t feel tempted in actually typing something that make sense (see example in Figure 7; obviously don’t use the example we are giving). After typing this random 63-character word, click on the box "Display characters" and select your key, copy it to Notepad and then print it.
• Check the "Save this network" box.
• Click on "Next" after you are done.

Figure 7: Creating our own wireless network.

6. On the next window you have to click on "Turn on Internet connection sharing", so other people will be able to access the Internet wirelessly.

Figure 8: Click on "Turn on Internet connection sharing".

Configuring The Other Computers

Now that you have configured the host computer, it is time to configure the other computers that will have access to your wireless network. This configuration is very simple. As already explained, the requirement to have Windows Vista or greater is only for the host computer; client computers can have Windows XP running and in fact our example below is for a client computer running this operating system.
For that, simply click on the wireless network icon on the task bar (one of the small icons near the computer clock) and select your network from the list that will be shown (see Figure 9). To make sure the correct kind of encryption is enabled, double check to see if “WPA2” is listed for your network. In our case, our network was called “Gabriel,” see how WPA2 is being listed for this network.

Figure 9: Selecting the network.

After selecting your network and clicking on “Connect,” the operating system will ask you to enter the network key (that random 63-character word) two times. You only have to do this on the first time the computer connects to your network, after that the computer memorizes the key.

Figure 10: Entering the encryption key.

Source "HARDWARE secrets"

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