Extend the Reach of Wireless Networks

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In this recipe, I'll show you how to build a network with cable-modem Internet access that is shared by two wireless access points, extending beyond the normal reach of a wireless local area network (WLAN). Such an extended WLAN is useful in situations where either you cannot run wired Ethernet connections, or you require the flexibility provided by network access without a tether.

As I'm sure you know, WLANs have become popular for sharing files and Internet connections. WLANs are easier to set up than conventional wired Ethernets, since there are no cables involved, an important consideration for residential applications and some small-business settings. Also, WLANs offer flexibility. Network users are no longer tied to a desk near an Ethernet outlet. With a WLAN, they can roam around the office or home.

But WLANs have their downsides, too. For one, network speeds on standard WLANs are generally lower than those on commonly available and inexpensive wired Ethernet LANs. While the forthcoming 802.11n wireless standard will enable greatly improved WLAN speeds, the standard is not expected to be approved before 2008. True, "pre-n" wireless gear is currently available, but using these devices to implement a network remains risky. You could end up buying gear that turns out to be a technological dead end, especially if software upgrades to 802.11n for your chosen equipment are not made available.

For another, unless you use expensive Tier-1 wireless networking gear, each device will have only one radio inside of it. This means the same radio that enables computers to access the WLAN also has to retransmit data to and from the other wireless bridge. This further reduces throughput.

Finally, WLANs are inherently less secure than wired Ethernet LANs. That's because wireless network signals are broadcast through the air, where they are relatively easy to detect and grab.

Despite these drawbacks, sometimes a WLAN is still the best--or even the only--way to build a local area network. So let's get started by setting up a WLAN using the Wireless Distribution System (WDS) for the purpose of sharing a cable-modem Internet connection. WDS is a protocol that allows wireless access points to connect directly to one another, extending a WLAN.

INGREDIENTS

Aside from the end-user PCs, to build this setup, you will need the following hardware:

• Cable modem: You can use one that does not require any configuration other than being provisioned by the Internet Service Provider (ISP). I've had good results with Motorola cable modems, which can be purchased for under $100 at many electronics retailers. The principles discussed in this recipe can be used to share a DSL or T1 connection, too.

• Router: This acts as the network's firewall and enables multiple hosts to access the Internet. Any of the sub-$100 routers sold as Internet gateways by SMC, Linksys, Netgear or D-Link should work fine.

• Wireless access points (WAPs): You will need two of these, which support a Wireless Distribution System (WDS). The WAPs I use and recommend for this recipe are SMC 2586W-G. Other vendors, including Netgear, make similar devices. WAPs that support WDS tend to be more expensive than those you can pick up at your local electronics mart, and they are often part of the maker's "professional products" line. Prices are in the range of $150 to $300, and you may need to order them online (NewEgg.com, for example).

• Ethernet patch cords: You will need two of these. One to connect the router to the cable modem, and one to connect WAP1 to the router.

• Surge protectors or battery backups: I recommend battery backups (aka uninterruptible power supply or UPS), which also function as line conditioners. These offer better protection for the devices they power than plain surge protectors. I've had good luck with UPS units from APC, but units from any major vendor should work just as well. Because the network elements discussed in this recipe don't draw a lot of power, if the UPS will not be powering other equipment, then smaller units selling for around $100 should work fine.

For best performance, all wireless clients should support the 802.11g standard. If even one 802.11b client connects, the entire network will slow to "b" speeds. Also, if you have access to a laptop with a wireless card, using that will be easier than trying to configure all the network elements with multiple desktop PCs.

Here's a diagram of the network we'll be building in this Recipe:

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