Electronic Design
Watch Out, Bluetooth— Wi-Fi Is Targeting Peripherals

Watch Out, Bluetooth— Wi-Fi Is Targeting Peripherals



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The latest Wi-Fi peripheral products from Seagate and HP remind me of Mad magazine’s Alfred E. Neuman signature phrase, “What, me worry?”

Bluetooth has been the wireless peripheral interface since it came out. The Bluetooth Special Interest Group was formed back in 1998. The Bluetooth 1.0 specification was released a year later. Version 1.2 has a 1-Mbits/s data rate and Version 2.0 kicked that up to 3 Mbits/s, which translates to an application throughput of 2.1 Mbits/s.

Low-power operation was one of the driving factors behind Bluetooth. There are three power-related classes. Class 1 has a maximum power of 100 mW with a range under 100 m. Class 2 tends to be the most common, delivering 2.5 mW and a 10-m range. Class 3 offers 1 mW.

Version 3 and 4 maintain the Version 2 speeds but have cooperative Wi-Fi support. In these cases, Bluetooth is used for initial collaboration, and high-speed interfacing is then handed off to Wi-Fi. This requires a Wi-Fi stack that cooperates with the Bluetooth stack. It essentially utilizes the Bluetooth security and pairing for Wi-Fi that has been notoriously hard to synchronize.

Low Power Wi-Fi

Changes in Wi-Fi chips have pushed down the power requirements while maintaining the advantages such as high performance. Seagate’s GoFlex Satellite (Fig. 1) and HP’s Wi-Fi Mobile Mouse (Fig. 2) highlight these changes.

The GoFlex Satellite is a specialized, wireless network access storage (NAS) device paired with an Apple iOS-based platform like the Apple iPad and iPad 2. Unlike conventional NAS devices that use network protocols like NFS or CIFS, the GoFlex Satellite only works with the matching app.

Likewise, the wireless hard drive is paired with a host, as are most Bluetooth devices. Unlike Bluetooth 3 or 4, the GoFlex Satellite handles all negotiation and handshaking using Wi-Fi only. Actually, the system supports up to three iPads at one time, pushing it closer to a NAS device.

Low power is a requirement because the GoFlex Satellite runs off its own battery. It is charged and accessible via USB, but normal operation is wireless. It can stream audio and video so users can watch movies on the road without an Internet connection. Priced at $199, the 500-Gbyte hard drive runs up to five hours.

HP’s Wi-Fi Mobile Mouse pairs with a Windows 7 laptop with Wi-Fi support. Recent laptops will have Bluetooth and Wi-Fi support, but it is rare to find one without Wi-Fi. The Wi-Fi Mobile Mouse requires a special driver that works with the Windows 7 Wi-Fi stack. It handles pairing like a Bluetooth device would use.

The $49.99 five-button device is a top-of-the-line 1600 CPI optical mouse. The pair of batteries lasts up to nine months, which is twice as long as many other wireless mice. It can operate from as far away as 10 m.

A host could save power if it didn’t have to run Bluetooth and Wi-Fi. The Bluetooth SIG has done a wonderful job maintaining interoperability. For now, the GoFlex Satellite only works with iPads, and the Wi-Fi Mobile Mouse works only with Windows 7. Both would be useful on other platforms like Linux/Android. The Wi-Fi Alliance has a number of standards. We will have to see how it fares in the peripheral arena.

Harald “Bluetooth” Gormsson is probably rolling over in his grave.



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