How To: Setting up WDS Bridging / Repeating

9. Example 2: Two-hop Repeater Test

In some cases, you may want to chain repeaters together to achieve a longer-distance connection. This method has the disadvantages of providing a slower link for STAs associated to the "far end" repeater (or connected to an Ethernet LAN in bridging applications) and being less robust than a "one-hop" link due to the additional radio.

But given the higher maximum speeds provided by 802.11g-based products, you can still end up with speeds comparable to those provided by a strong 11b signal at the second repeater, which could be just fine for your needs. Figure 6 shows the setup.

Figure 6: "Two hop" WDS Bridge w/ Repeating

To mix things up a little bit, my choice for the third AP in this example is the ASUS WL330 [reviewed here]. I threw in the 11b AP to show what happens when you mix 11g and 11b products in a WDS setup and also to see if WDS would work with products based on different chipsets.

Even though the WL330 is based on Marvell's Libertas 802.11b Access Point Solution vs. Broadcom technology, I found it worked fine in my setup. It probably helped, however, that I had two ASUS products making the WDS link. Table 2 shows the WL330's information added to my AP information summary.

Figure 7 again shows the Bridge setup screen for what is now the middle WDS AP, this time with an additional MAC address entered in the Remote Bridge List.

Figure 7: ASUS WL300g Wireless Bridge setup - two hops

Figure 8 shows the Wireless Distribution System screen for the WL330 (which is strangely located in the Access Control section).

Figure 8: ASUS WL330 WDS setup

Though both products come from ASUS, you can see the difference between the WL300g and WL330's WDS controls. Both have AP only modes, but the 330 only supports "Hybrid", i.e. repeating WDS connections. So you would not be able to use it for Bridge-only applications.

But on a positive note, the 330 doesn't have the separate Connect to APs in Remote Bridge List? and Allow Anonymous? radio buttons. Instead the allowed WDS MAC address list is active when you select "Hybrid-Active" mode and greyed-out when "Hybrid-Passive" is chosen. Since I want to specify the connecting AP's MAC address, I chose "Hybrid-Active" mode and entered the WL300g's MAC address.

After things were up and running I ran another throughput test and generated another composite Chariot plot shown in Figure 9.

Figure 9: Throughput comparison - Base AP and two hops
(click on the image for a full-sized view)

The 1.8Mbps average throughput that I got when associated with the WL330 at the end of the WDS chain (bottom trace) seems low at first glance, but makes sense when you think about it.

Since it's an 11b radio that has a best-case throughput of only around 5 - 6Mbps doing double duty, we should expect at the most only 2.5 - 3Mbps. Add in that the 8Mbps bandwidth available to the WL330 is lower than 11b's maximum 11Mbps raw data rate and we're right in the 1.8Mbps ballpark. What's that old saying about a chain only being as strong as its weakest link?