Mobile Phones Evolve Toward Pocket HDTV

Mobile phones are continuing to evolve at a furious pace, heightening value by incorporating a growing range of functionality: texting, E-mail, browsing, digital cameras, TV tuners, and more. The next step is high-definition TV (HDTV). At last, mobile phones will be able to handle HDTV content.

The day is not so far off when people will be able to hook their mobile phones up to the TV, and enjoy downloaded content on the big screen; use a miniature internal projector to show high-definition imagery on walls, ceilings or other surfaces; or record HDTV programming to a mobile phone while on the road.

Component manufacturers are already swinging into action, developing a host of new products aimed specifically at HDTV applications. In mobile phone application processors, for example, it will be possible to process 1,280 x 720 pixel (720p) video as early as 2009, and if the pace continues it would not be surprising to see products offering support for 1,920 x 1,080 pixel (1080p) video by about 2011.

The countdown has begun, equipping handsets with pins for high-definition multimedia interfaces (HDMI), capable of handling HDTV video uncompressed. TV tuners for terrestrial digital broadcasting are getting ready for an upgrade to "full-segment" design, capable of receiving the same HDTV content displayed on the home tube, far beyond the current one-segment receivers today for quarter video graphics array (QVGA) size display. The role of mobile phones themselves is likely to change significantly when they can handle HDTV video content. Specifically, they will evolve to interconnect more with the TV and other equipment.

There are limits to handset size: there is little point in displaying a high-definition HDTV video stream on only a tiny screen. People really want to view HDTV content on a big screen. HDTV capability will demand that mobile phones are provided with functions to connect to large-screen TVs and other audio-visual (AV) equipment to swap content.

Equipping handsets with functions for interconnecting with TVs and other pieces of equipment will cause mobile phones to evolve in new directions. For example, it is quite possible that some products will come without much display area, being instead designed to display content on external devices. Bold innovation, unfettered by existing concepts, is becoming more important than ever in handset product planning, application development and other areas.

Application Processors: Support for 1080p Before End of 2008
Evolution of application processors will guide the direction of HDTV support in handsets. The first products supporting 720p HDTV video streams will ship in the second half of 2008, and 1080p-capable products are clearly on the way in 2009.

The central processing unit (CPU) core operating frequency for handset application processors has been steadily rising, driven by shrinking semiconductor manufacturing geometry. The pace of progress is steady, and the first chips with operating frequencies over 1GHz will appear as early as the second half of 2008. High-end application processors are also beginning to provide support for HDTV video streams exceeding 1,980 x 1,080 pixels (1080p), three-dimensional (3D) graphics processing capable of drawing over 10 million polygons/s, and more.

When processing HDTV video, these processors use custom circuits to handle the majority of coding and decoding. According to Hiroaki Tabuchi, Wireless Terminals Business Unit Japan of Texas Instruments Japan Ltd (TIJ), "Custom circuits will handle common processing, while the digital signal processor (DSP) core handles encoding-specific processing." This approach is used to flexibly handle a wide range of encoding schemes, such as MPEG-4 AVC/H.264, MPEG-2 and Video Codec 1 (VC-1). It is possible that multiple CPU cores will become more common to ensure that HDTV video streams can be processed efficiently.

Overseas manufacturers have the lead when it comes to HDTV video support in application processors. Broadcom Corp of the US announced such an application processor in October 2007, followed by NVIDIA Corp and Texas Instruments Inc (TI), both of the US, in February 2008. These products all handle HDTV video encode/decode processing at 30 frame/s (fps) for 720p.

Renesas Technology Corp of Japan, with the second-largest global revenue share for application processors, is also planning to release products supporting HDTV. The reason, according to Kazuhiko Yoshimatsu, department manager, Mobile Product Marketing Dept, System Solution Business Group of Renesas Technology, is that "Home-use digital equipment is packed with 1080p image content." Application processors handling 1080p at 30 fps are scheduled to be announced before the end of 2008.

Broadcom, TI and other firms are also announcing plans to develop application processors supporting 1080p. Many integrated circuit (IC) manufacturers are likely to release chips supporting 1080p in 2009.

The three firms that have developed 720p application processors have assumed connection to TVs. For example, Broadcom's BCM2727 and NVIDIA's APX2500 already come with HDMI interface processing functions for exactly that reason. "Feedback from handset makers is excellent. Mobile phones, smartphones and other terminals mounting the chips could appear as soon as 2009," revealed Robert Nalesnik, marketing director, Mobile Platforms Group at Broadcom.

Interfaces: Onboard HDMI in 2009; Miniature Connectors a Key Issue
The debate is heating up over whether or not to implement HDMI as an external interface in handsets. If the handset is connected to the TV using HDMI it would be possible to view HDTV content downloaded to the handset on the TV's large screen. HDMI includes a copyright protection function for High-bandwidth Digital Content Protection (HDCP)-compliant content, so HDTV imagery could be swapped securely.

The target for implementation in mobile phones is 2009 to 2010 (Table 1). Some manufacturers already offer miniature control ICs designed for mounting in handsets. Industry is gearing up for a full-scale approach to an enormous market, including connectors, cables and other components as well.

One major problem in implementing HDMI is connector shape. The HDMI 1.3 specification defines a Type C connector, which is smaller than the current standard-size Type A connector. Connectors, cables and other components for Type C are already on the market.

Users are likely to demand even smaller handsets in the future, though. An engineer at a key company behind the HDMI interface said, "Implementing HDMI in mobile phones will require a dedicated connector only about half the size of the current Type C design." An engineer at a connector manufacturer added, "The target for handset HDMI connectors is about the size of the audio output connectors used in handsets now."

A group of firms leading the HDMI initiative has launched what they refer to as "HDMI mobile", a project to standardize HDMI specifically for mobile phones. The project appears to be considering two proposals for a miniature connector, one with a smaller shape but the same 19 pins as the current HDMI design, and the other with a smaller shape and only 11 pins. The former is supported by AV equipment manufacturers, and the latter by handset makers.

The person in charge of the 19-pin proposal at one manufacturer stressed, "The 19-pin approach is the only realistic choice if we're to maintain compatibility with existing equipment. I think maybe the only people who say it can't be done with 19 pins are companies lacking the requisite technical expertise." Manufacturers pushing the 11-pin solution, on the other hand, point to the fact that functions not implemented in mobile phones require no pins at all. Both sides, however, plan to use transition minimized differential signaling (TMDS) in the physical layer.

Displays: Internal Projectors so Everyone can Enjoy the Show
Many engineers working on liquid-crystal display (LCD) and organic light-emitting diode (OLED) panels 10-inches and smaller, for use in products such as handsets and game systems, agree that the limits have already been reached for critical mobile phone display characteristics including size and pixel count.

More and more handsets available in Japan now are offering 3-inch LCD panel displays with about 800 x 480 pixel (wide video graphics array, or WVGA) resolution. If the display is expanded to 3.5 inches or larger, it becomes difficult to operate the handset in one hand. Also, human vision really can't detect much difference in image quality even if the definition and pixel count are further improved.

As a result, even if mobile phones become able to support HDTV, they may not be able to display HDTV imagery as-is. One possible solution to this problem is connecting handsets to TVs or other equipment for display. Another possibility is the ultra-miniature projector expected to show up in handsets in 2009 or beyond.

Putting a projector in the handset will change the way mobile phones are used. "The restrictions on display size in mobile phones have limited them to personal use until now. A handset capable of projecting an image of about 20-inch size, though, will be an entertainment system capable of storing photos, video and other media for enjoyment by groups of people," said Kazuhiro Ohara, senior manager, Product Marketing, Technical Support Center, DLP Products Japan of TIJ.

A variety of miniature projector prototypes targeting portable devices such as handsets have already appeared. A number of manufacturers are interested, including companies involved in projectors and display devices. The display devices used in these prototypes can be grouped into three general categories, namely (1) micro-electromechanical system (MEMS) mirrors, (2) digital micromirror devices (DMD), and (3) LCD panels. The LCD panel category can be further divided into transmissive LCD panels and reflective LCD panels, specifically liquid crystal on silicon (LCOS).

The MEMS mirror designs are in the lead when it comes to miniaturization. The smallest projector module currently available is the PicoP, developed with MEMS mirrors by Microvision Inc of the US. The company adopted a laser light source and MEMS mirror display device to pack the whole module, including projection lens and control circuits, into a volume measuring only 20 x 40 x 7mm, or 5,600mm3. The laser light source is scanned across the screen under MEMS mirror control, projecting the image. Unlike DMDs, LCD panels and similar technologies, the display device does not have pixels in MEMS mirror designs. In addition, the laser light source has excellent linearity and brightness.

This means that the optics are much simpler than those used with light-emitting diode (LED) light sources. Jacques Lincoln, product manager, Head-Up Displays at Microvision, said, "The simple structure is what makes miniaturization possible. For implementation in a mobile phone we'll make the control circuits into an ASIC chip, and build it into the application processor for an even smaller design."

By Hiroki Yomogita, TechOn