D-Link TN230 User Manual

TN230

Off-the-Shelf Solutions for 802.11b

Wireless Networking

This document describes some off-the-shelf solutions for using wireless networking with Rabbit products.
Although these solutions have certain limitations, they may be useful in some circumstances.

What Wireless Solutions Exist?

Currently, the most popular methods for achieving wireless networking are with 802.11b and 802.11a.
Bluetooth is another common alternative, although it is generally shorter-range and has not achieved the
widespread commercial success of 802.11b. 802.11b operates in the 2.4 GHz spectrum and offers data
rates of up to 1 1 Mbps. 802. 1 1 a opera tes in the 5 GHz spectr um and has dat a rates of up to 54 Mbps. Some
vendor-specific solutions offer higher data rates, but these rates are usually not interoperable with other
vendors’ products. 802.11b products usually claim ranges of up to 300 feet indoors and about 1000 feet
outdoors, but these figures are subject to such concerns as number of obstructions and interference.

802.11a’s range tends to be slightly less (although it is capable of higher bandwidth). Bandwidth will
decrease as th e range increases. Unfortunate ly, there is no substitute for experimentation i n testing the
range of a wireless solution.

Wireless Bridging

A number of wireless networking products are currently on the market that can be used with Rabbit solu­tions. In particular, some, but not all, wireless access points are capable of “wireless bridging,” which
allows the bridging of two wired networks with a wireless connection. Unfortunately, it can be difficult to
determine which products support wireless bridging. Even looking for the term “bridging” in the product
documentation is not always helpful, since wireless access points are often described as bridging a wired
and a wireless network. If the documentation explicitly discusses bridging two wired networks via a wire­less connection, then the product should work for the purposes of connecting one or more Rabbits wire­lessly. If the product is advertised as a wireless broadband router (usually with a 4 or 8 port hub included),
it probably does not support wireless bridging.

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Some other devices are now being released that are designed specifically to connect a wired Ethernet
device to a wireless network. These are called “wireless bridges” or “802.11b Ethernet media converters.”
It is importan t to note that you cannot use two of these devices to create a wireless bridge between the
device and an existing wired network. Instead, these devices must communicate with a wireless access
point. These devices are smaller and slightly cheaper than access points .

At the current writing, the following access points are examples that support wireless bridging:

• Linksys WAP11

• Netgear ME102

• D-Link DWL-900AP

• D-Link DWL-900AP+

In general, these devices will not perform wireless bridging with competing devices—that is, don’t expect
to be able to mix and match. Some examples of the new wireless bridges are:

• Linksys WET11

• D-Link DWL-810

• Buffalo Technology WLI-T1-S11G

These can be used with any standards-compliant 802.11b access point. Note, how ever, that the Linksys
WET11 has a physical layer compatibility problem with Realtek RTL8019AS Ethernet devices (the
chipset used by many Rabbit devices) that causes the WET11 device to repeatedly reboot or lock up. We
have tested the D-Link DWL-810, and it does not exhibit the same problem. Hence, it is recommended
over the Linksys WET11.

When Is a Wireless Solution Useful?

Currently, inexpensive wireless access points that perform wireless bridging cost about $100 to $200.
Since two are needed to complete a wireless bridge, this is an expensive solution for wirelessly connecting
a Rabbit device. The range and susceptibility to interference also limit the usefulness of wireless bridging,
particularly in industrial settings. However, wireless bridging may be useful for connecting two wired net­works when it is inc onv enient to connect them via a wir e. Al s o, if a number of Rabbit products c an be con­nected via a traditional wired Ethernet, but they need to communicate with another server or the global
Internet, then a shared wireless connection for all of them can be convenient.

It is possible to extend the range of some wireless access points with a custom antenna. For instance, the
Linksys WAP11 (and most other Linksys wireless products) feature replaceable antennae. However, care
should be taken that FCC regulations are obeyed if the devices are modified.

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How Do I Set Up a Wireless Connection?

Rabbit Semiconductor has tested Rabbit products with Linksys WAP11 access points and the D-Link
DWL-810 wireless bridge. The following explanation on how to set up a wireless connection will be cen­tered around using two WAP11s, but othe r acc es s poi nt s and wir el es s bri dg es may be set up simi la r ly.

In general, you will need a pa ir of acces s points o f the s ame model to perf orm wir eless br idgi ng, unl ess t he
documentation states that it is compatible with other products. Connect one access point to an existing
wireless network, and the other to a Rabbit device via a crossover Ethernet cable, as detailed in Figure 1.
Some access points have a crossover switch that allows you to flip the switch to the crossover se tting and
use a normal straight-through cable rather than a crossover cable. The access point connected to the Rabbit
can be replaced with one of the wireless bridge products, but the other side will need to be an actual wire­less access po int.

Figure 1. Connecting a Single Rabbit Wirelessly to an Existing Ethernet Network

Existing Ethernet network

Wireless

Straight-through cable

Access Point

Wireless
Access Point

Hub

Crossover cable

Note that it is possible that the “Existing Ethernet network” above is a single PC so that in effect you are
wirelessly connecting a PC and a Rabbit. In this case, the cable connecting the PC and the wireless access
point should be a crossover Ethernet cable (or, if your access point has it, you should use the crossover
switch).

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