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In Use and UWB USB Performance Primer

Setting up the product was uneventful. I just loaded the CD onto my notebook, installed the drivers and plugged in the dongle. The Cable Free Hub client application appeared in the System tray, showing a yellow icon (dongle enabled, but no connection). But once I plugged the power wall-wart into the hub and entered the "Product ID" from a label on the hub bottom into the client app, the icon turned green and I was connected up and ready to go.

Note: There are two labels on the bottom of the hub, each with numbers that could be the "Product ID". The Product ID is actually listed as the "ID Number:" on the serial # label above a bar code. The format of the number reveals its real identity, the hub MAC address.

Figure 4 shows the client application screen, with a connection up and running. The Product ID was entered in the area that has the Un-Register button in the screenshot.

Figure 4: Cable Free Client Application

Before I present my performance test results, let me equip you with some information you'll need to be an informed consumer of UWB/USB products. Belkin provided the handy diagram in Figure 5 in its reviewer's guide, which while instructive, still bears some translation.

Figure 5: The Pyramid of wireless USB throughput truth

What the diagram is trying to say is that no real UWB/USB device will ever reach the pinnacle of the advertised 480 Mbps PHY rate. The best that a "highly optimized" solution could reach would be ~320 Mbps, with a more realistic expectation being the ~270 Mbps of a "standard (wired) USB solution. This isn't really a shocker since we all know by now that the number on the product box is usually a lie.

The Belkin product falls into the bottom "HWA > DWA" area of the pyramid that represents a connection that has the UWB radio connecting to the CPU via a USB 2.0 connection on each end of the connection. You can see that the additional interface slows things down considerably to a 30 - 45 Mbps range—over a factor of 10 reduction from the advertised number. Note that this will be the performance range of any of the UWB/USB "hub+dongle" products that are expected out over the next year—Wireless USB flavor included.

The next step up in performance to the 80-120 Mbps range will be products having "Native" host and/or device interfaces. An example of a "Native" device could be a Wireless USB printer—if it doesn't actually hide a "Wired" (additional USB 2.0) intermediate interface inside. So you'll have to be on your toes and pay attention to the specification details that manufacturers will hopefully provide when Wireless USB devices start appearing.

Even when those devices do hit the stores, you won't get the best possible (~200 Mbps) throughput until computers with "Native" Wireless USB host adaptors start appearing. If what I heard at CES is true, you shouldn't expect to see those until 2008 at the earliest.