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Cellphones eye wireless video

Posted: 23 Jul 2007 ?? ?Print Version ?Bookmark and Share

Keywords:Ultrawideband? UWB? Certified Wireless USB? WiMedia? Bluetooth?

By Billy Brackenridge
Staccato Communications

Ultrawideband or UWB has been around for nearly half a decade as a demonstrable technology and is now appearing in the form of ICs that will be used to implement Certified Wireless USB in PCs and peripherals. How long will it be before UWB is deployed in mobile phones?

Power consumption
UWB has been promoted as a low-power wireless technology suitable for battery-powered devices. From a theoretical viewpoint, UWB is the most efficient technology for wirelessly transmitting a large number of bits over short distances. In terms of joules per bit transferred, UWB is the most efficient technology employed today.

The combination of low power consumption and high bandwidth suggests UWB can support compelling applications. Not only can one download a feature-length motion picture in a minute or so, but there will be plenty of battery power left to play it and pass it along to others, ensuring payment for new copies.

Theoretical efficiency does not automatically translate into practical systems that can live within a mobile-phone power budget, but practical experience to date suggests WiMedia systems will evolve to deliver on what theory is promising.

No one should be surprised that WiMedia radios can transmit using very little power, but it isn't obvious that WiMedia radios require a bit more power to listen than they do to transmit. WiMedia receivers work by digitizing the incoming signal and applying computationally intensive signal-processing routines to look for patterns in the signal.

The Bluetooth SIG has taken the tack that WiMedia will be used as an accelerator for the existing Bluetooth system. Bluetooth will use its narrowband 2.4GHz radio to discover devices, make a connection and establish a security relationship. The WiMedia radio will be used as a fast encrypted pipe to accelerate existing Bluetooth profiles.

This approach will let existing Bluetooth vendors get to market with a WiMedia solution with a minimum investment in new software, but equally important, it finesses power management issues. The next-gen Bluetooth will keep the WiMedia radio turned off unless it is actively transferring bits.

WiMedia on handsets
The most likely first application for WiMedia in a mobile phone is for synchronizing and downloading of media files from PCs. This will exploit Certified Wireless USB. This is a relatively simple application to implement, as wired USB is already used for this purpose. The necessary software for the PC side is under development by Microsoft for Vista and chip vendors and independent software houses such as Stonestreet One are supporting XP and other operating systems.

For wireless USB hubs, this display and a pushbutton will be built into the hub. This allows USB devices to get a wireless connection with no changes to firmware. The devices have no way of knowing that their connection to the host is via a wireless link. This solution would be clumsy for use in a mobile phone. (It is a great solution for a phone-charging stand.) The human interface is more usable when integrated into the phone display.

The USB Implementers' Forum defined detailed hardware interface specifications for USB hosts, since standardized software is expected to work with many vendors' devices, but did not specify a device interface. To make it easy to implement Certified Wireless USB devices, Staccato Communications has defined the Ripcord Control Library. This RCL abstracts the hardware interface such that Staccato's Ripcord 3500x WiMedia device can connect via USB or SDIO and the software interface looks the same. RCL ships with ANSI C source code that ports easily to any OS environment. The included sample code implements first-time association and allows the embedded system designer to optimize resources such as USB buffer space to best support the application.

The first application for WiMedia on mobile phones will be cable replacement for existing USB connections. System designers seek the lowest-cost, smallest-package, easiest-to-port hardware that meets WiMedia and Certified Wireless USB specifications.

Designers should also consider the flexibility of the interface and richness of the software runtime environment as the exciting future applications must move beyond USB cable replacement.

WiMedia will be integrated with Bluetooth and Certified Wireless USB and Bluetooth may be operating at once.

As 3G and WiMAX applications evolve, the mobile phone may become the Internet access point. Cameras, laptops and phones will form personal-area networks sharing resources locally while accessing the Internet.

WiMedia can support the bandwidth needed to display video on a PC or TV. Processors on phones are getting more powerful and storage capacities are running to tens of gigabytes. Phone displays won't get any bigger and many applications could exploit larger displays.

These applications are speculative and depend more on market conditions than technical factors, but the reality is that WiMedia devices will be selling this year in the form of Certified Wireless USB peripherals for PCs. It's time to start evaluating product and chip vendors in the context of how well WiMedia systems will port to mobile devices.

About the author
Billy Brackenridge
is a product systems architect at Staccato Communications, where he finds innovative uses for WiMedia devices in customer applications.

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