Tuesday 17 May 2011

wireless networks


What You Need

If you're still using a dial-up modem to access the Internet, it's time to consider broadband. Depending on where you live, you can either opt for a cable or ADSL/DSL solution. A cable solution uses a cable modem such as the Motorola SB4200 SURFboard to connect to an access point, such as those used for cable TV. On the other hand, an ADSL/DSL modem uses the phone line to connect to the Internet.
The advantage of using a cable modem is that the connection is always on; there is no need to dial up to a server. The same can be true for ADSL/DSL, though it still takes a short while to reestablish a connection after it has been disconnected due to inactivity. Speed-wise, you could possibly achieve speeds from 256Kbps to 512kbps for an ADSL/DSL connection, while the cable modem can achieve a speed of 1.5Mbps. Note that speed depends on your service provider.
The Motorola SB4200 cable modem
Figure 1. The Motorola SB4200 cable modem
The cable/ADSL/DSL modem usually comes with two types of interfaces that you connect directly to your computer--USB or Ethernet. But doing so only allows one computer to connect to the Internet. Instead, by using a router, more than one computer can have access (in this case, your modem must support the Ethernet connector). Since most ISPs provide only a single IP address for a cable/ADSL/DSL connection, you need a router that is able to perform Network Address Translation (NAT). NAT translates multiple IP addresses on the local network to a single IP address that is sent out onto the Internet.
But the point of this endeavor is going wireless, so we need to find a wireless access point (AP) that comes with a router. The Linksys BEFW11S4 is a good example; it's an 802.11b wireless access point with a four-port switch. 802.11b devices can transmit data at a maximum data rate of 11Mbps, with an effective range of about 150 feet. But don't be misled by these numbers--in practice, you can expect a much lower data rate, and the effective range is dependent on the obstructions placed between your AP and your receiver.
The Linksys BEFW11S4 Wireless Access Point with 4-port switch
Figure 2. The Linksys BEFW11S4 Wireless Access Point with 4-port switch
You connect your cable/ADSL/DSL modem to the WAN port of your wireless access point (plus up to four computers with Ethernet cables to the four-port switch). I like to place my wireless access point near my desktop computer so that I can connect it directly using an Ethernet cable.
Rear of Linksys BEFW11S4
Figure 3. Rear View of the Linksys BEFW11S4
With the above setup, all of your computers, connected directly to the access point via Ethernet cables, can now surf the Internet! Check the IP address of each computer connected; they should all be different.
Now let's turn to the wireless portion of things. First, you might have a notebook computer that you want to connect to your home network. For this purpose, you can easily get a wireless PCMCIA card for your notebook, such as the Linksys WPC11.
The Linksys PCMCIA 802.11b Wireless Adapter
Figure 4. The Linksys PCMCIA 802.11b Wireless Adapter
If you want to enable wireless access for your desktop, you have two choices of adapters--PCI or USB. The Linksys WMP11 is an 802.11b PCI card that allows your desktop to connect to the network wirelessly:
The Linksys WMP11 802.11b PCI Wireless Adapter
Figure 5. The Linksys WMP11 802.11b PCI Wireless Adapter
If you do not want to open up your computer casing, or you simply want to share a wireless adapter among many computers, the Linksys WUSB11 is a good choice. Simply connect the USB wireless adapter to the USB port on your computer and you can get on the network.
The Linksys WUSB11 USB Wireless Adapter
Figure 6. The Linksys WUSB11 USB Wireless Adapter
Figure 7 shows a typical wireless network setup:
A Typical Wireless Network Setup
Figure 7. A Typical Wireless Network Setup

Configuring Wireless Devices

Once all of the necessary devices are installed, it's not difficult to test the wireless connection. Your wireless adapter comes with utilities to change its settings. In my case, I'm using the software that came with the Linksys PCMCIA card.
Examining the Link Quality and Signal Strength of the Wireless Connection
Figure 8. Examining the Link Quality and Signal Strength of the Wireless Connection
Under the Link Info tab, it shows that my link quality and signal strength are pretty good. In general, the closer the wireless adapter is to the wireless access point, with a clear line-of-sight, the better the signal quality.

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