Wireless USB: Real, Ready and Slow
Since the WiMedia Alliance's catchphrase for the show was "Real & Ready", I dropped by to see if they could explain why Wireless USB products still aren't shipping and why reviewers have found that the technology that hypes a "480 Mbps" transfer rate has real throughput of around 8 Mbps.
None of the chip manufacturers in the WiMedia area were going to speak to the first point, but I got both confirmation and explanation of the slow data rate of at least the Belkin Cable-Free USB Hub from the folks at Wisair (which makes the chipset used in the Belkin product).
The main throughput killer for the Belkin product was explained to be the "USB 2.0 host" (Wireless USB module connected via USB 2.0) adapters at both ends of the connection. Even though USB 2.0 has the same 480 Mbps maximum data rate as Wireless USB, the overhead and inefficiencies in the bus-to-bus transfers take their toll. The other throughput-eater was said to just be the fact that the tuning required to maximize performance hasn't yet been done.
The Elusive Belkin Cable-Free USB Hub
The Wisair rep said that the best case throughput that could be expected with USB host adapters at both ends of the connection is around 50 Mbps (or 6.25 MBytes/sec) If one end is able to be a "native" device, i.e. with the Wireless USB module interfacing with an internal processor bus like PCI, throughput could rise to around 100 Mbps. Best case throughput will be seen with native-to-native device transfers, which are expected to come in around 200 Mbps.
Real world testing done by Craig Ellison for PC Magazine using flash memory cards showed much lower throughput than estimated by Wisair. The summary table below from Craig's article shows throughput with the Belkin product to be around 8X lower than a wired USB 2.0 connection and 6X lower than the numbers offered by Wisair. At any rate, paying almost $200 for what amounts to a wireless USB extender that is significantly slower than a wired connection doesn't seem like a very good deal to me.
USB 2.0 vs. Wireless USB transfer speed
of PC Magazine)
This "year of Wireless USB" will see primarily hub-and-dongle products like the Belkin (assuming it starts shipping at some point). The latter half of the year might start to see some "native" Wireless USB solutions integrated into PCs, but I wouldn't hold my breath. And when might we see devices like cameras, cell phones and media players with native Wireless USB? Try next year... if PC manfs hold up their end of the deal with integrated native Wireless USB.