The one constant in mobile-phone design is change. Recently, this fact was underscored with the introduction of an assortment of creative new phones designed and envisioned to be in vogue around the world.

These novel phone designs are changing the way designers tackle some of the most difficult challenges: How do you provide faster digital and analogue processing speeds? How do you deal with all sorts of convergence of services technologies and applications? How do you keep power consumption low? Should you integrate digital signal processing (DSP) and radio-frequency technology on the same design?

Dedicated versus shared processing

A hot issue in mobile-phone design centres on how to partition chip functions to maximise horsepower without increasing power consumption. One architectural approach involves an entry-level mobile phone with CD-quality music. This design integrates the DSP and microcontroller functions on a single chip (see box, next page). The microcontroller functions have separate duties. One, integrated with the DSP, is an engine that handles communications processing, such as the actual mobile-phone voice signals. The other microcontroller's sole responsibility is handling the processing of, music, multimedia, and Internet access.

Using a dedicated applications processor separate from the communications engine reduces mobile phone manufacturer's 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 offering combined communications and applications processors. In addition, segmentation purges the interdependencies that result when domains share processing and memory space.

Also, the horsepower from the dedicated applications processor delivers several benefits:

• Facilitates phone calls and data downloads while playing music or video games
• Simplifies applications software code development, test, and verification for mobile phone manufacturers because it doesn't impact the core communications engine
• Reduces power consumption because the more power-hungry applications processor can be powered down most of the time a phone is on
• Liberates mobile-phone manufacturers to focus on developing applications and man-machine interfaces without worrying about impacting the communications engine

Mobile-phone convergence

Widespread debate has heated up in recent months about what device will ultimately be the centre of the most mobile-phone convergence. Devices being considered include mobile phones, PDAs, Blackberries, wireless LANs, and music players.

One question is whether the music-player handheld device will become a mobile phone, or will the mobile phone become a music handheld device? The truth is, both will probably happen. From an engineering perspective, however, there should be no doubt that much architectural planning going forward will be centred on the mobile phone.

With all of the mobile-phone application convergence continuing at a frantic pace, the phone designer must be nimble and smart in deciding what to integrate and what to leave as separate chips. They will have to keep their sights set on building higher-performance, lower-cost, and lower-power-consuming devices.

Mobile phones are stealing communications and entertainment functions from PCs. Therefore, the designer would benefit by being familiar with the latest PC design trends and apps.

Designers will have to figure out how to integrate GPS navigators onto mobile phones, because that market is gathering momentum. Also rapidly picking up steam is the design of CD-quality music capability on mobile phones, tracking with the amazingly popular small and easy-to-use music devices among consumers. Mobile phones can already store hundreds of songs.

For consumers to bite on these phones, though, high-quality digital acoustics hardware and software must be developed to make CD-quality music. In addition to CD-quality music, consumers need to be able to find a specific song quickly and easily.