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Next-gen handsets call for balance

Posted: 16 Apr 2007 ?? ?Print Version ?Bookmark and Share

Keywords:cellphone design? integration of features in cellphones? power consumption of mobile phones?

The one constant in cellphone design is change. One of the latest examples is the assortment of new creative cellphones being designed and envisioned to be in vogue around the world. These include a cellphone that enables CD-quality music at an entry-level cellphone price, a necklace-shaped handset with beads lighting up to signal an incoming call, and cellphones that look like macaroons and cakes.

These new designs are changing the way handset designers tackle some of the most difficult challenges, including:

? Providing faster digital and analog processing speeds;

? Dealing with convergence of services, technologies and applications;

? Keeping power consumption low;

? Whether to integrate DSP and RF technology on the same design.

Dedicated vs. shared
A hot issue in designing creative cellphones is how to partition chip functions to maximize horsepower without increasing power consumption. One architectural approach involves an entry-level cellphone that comes with CD-quality music. This design integrates the DSP and MCU functions in a single chip. The MCU functions have separate duties. Integrated with the DSP, it is an engine that handles communications processing such as for the voice signals. Its other responsibility is handling applications processing, such as music, multimedia and Internet access.

Using a dedicated applications processor separate from the communications engine reduces cellphone manufacturers' product development costs and boosts overall processing speed. This segmentation allows each processor to be fully dedicated to its particular function and eliminates complications such as increased integration and debug times that often occur with designs combining communications and applications processors. The segmentation also eliminates the interdependencies that result when domains share processing and memory space. In addition, the boosted horsepower provided by the dedicated applications processor enables several key benefits such as:

? Making phone calls and data downloads possible while playing music or video games;

? Easing of applications software code development, test and verification for handset makers;

? Reducing power consumption;

? Allowing handset makers to focus on developing applications and man-machine interfaces without worrying about impacting the communications engine.

Function convergence
There has been much debate on what device will ultimately be the center of convergence. Cellphones, PDAs, Blackberries, WLANs and PMPs are the top bets. The question is: Will the PMP become a cellphone or will the cellphone become a PMP? Both will probably happen.

From an engineering perspective, however, architectural planning will definitely be centered on the cellphone. "The cellphone continues to be the physical and market magnet pulling in the functionality of digicams, MP3 players, GPS navigators, Bluetooth, FM radio, DTV and even cordless phones, and is quickly becoming the dominant market for each and all of these functions," said Carter Horney, principal author of a Forward Concepts cellphone study called Cellular Handset and Chip Markets '06. With cellphone applications convergence continuing at a frantic pace, designers will have to be quick at deciding what to integrate and what to leave as separate chips. They will have to continue focusing on building higher-performance, lower-cost and lower-power-consuming devices.

Using a dedicated applications processor separate from the communications engine reduces cellphone manufacturers' product development costs and boosts overall processing speed.

Designers will have to figure out how to integrate GPS navigators onto cell phones, because that market is gathering momentum. But gaining particularly fast momentum is the design of CD-quality music capability into cell phones is also picking up with the popularity of small and easy-to-use music devices among consumers. Cell phones can already store hundreds of songs. To enable this, high-quality digital acoustics hardware and software will have to be developed to make the quality of the music CD quality so these cell phones will be appealing to consumers. In addition to requiring CD-quality music, finding the right song, the exact one the user wants quickly and easily, among the hundreds stored on the cell phone will be an important, differentiating feature.

The cellphone's power consumption lies at the heart of the architectural design trade-off issue. This trend will continue as new, more creative designs come to market. Cellphones need extended battery life without burning up the phone. They also need faster processing speed to handle higher-bandwidth multimedia services, such as mobile TV and music.

The solution to this problem no longer focuses on the silicon chip at the circuit level. It's crucial to address this problem from a system-level architectural platform perspective because the cellphone's hardware and software aspects must be factored into the design analysis to get more accurate solutions. This system-level approach opens more possibilities for design innovations to keep power low and bandwidth high.

Power-consumption design issues relate to an emerging trend in which reducing the number of features on a cellphone is considered wise. The notion is that cellphones should be designed only with the features and functions most widely used thus consuming less power. A growing number of handsets are being custom-designed and segmented to play high-quality music, browse with high-speed Internet or take digital camera photos, but not necessarily do all three on one cellphone.

The IC industry has been conceptualizing and working to deliver a cellphone architectural nirvana: combining RF and DSP silicon into one SoC. This integration has already begun to happen in the ultralow-cost cellphone segment. This has been made possible by the SoC benefits of fewer components, lower costs and lower power consumption. Achieving this SoC is probably too much to ask in the next few years, given the design complexity of new cellphones. No single-chip solution is likely to materialize in the market before 2008.

Other factors will push out this integration. A company that has cellphone basebands, but has no RF may consider buying silicon from RF chip providers. So far, however, that doesn't look financially feasible because RF prices are too high. If prices go down, the baseband provider would most likely collaborate with the RF provider, thus accelerating the development of the single-chip wonder.

- Roman Polz
Senior Manager, Mobility Division
Agere Systems Inc.

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