Tomorrow's teardown

What will portable wireless devices look like in the future? E&T looks into his high-technology crystal ball.

The launch of the 3G version of Apple's iPhone revealed a fundamental weakness in handset makers' plans. The launch showed that there is pent-up demand for mobile access to the Internet, but that the wireless data connections which make it possible empty the battery much more quickly than expected.

"It is the constant stream of data going back and forth. That is the largest drain," says Doug McEuen, senior analyst at ABI Research.

Apple has been able to resolve some of the power issues with a software update. But the Cupertino company and its competitors now know how vital power consumption will be to the future of their designs. And life is not going to get any easier.

Francis Sideco of market analyst iSuppli says: "Battery technology just plods along: it's not really catching up. Until we close that gap, which won't be for the foreseeable future, you have to do what you can to improve power efficiency."

McEuen says: "Not just in the iPhone and similar phones but in the next generation of mobile Internet devices, power becomes a gigantic issue. People want to leave their house and be mobile without needing a charge."

Ted Vucurevich, chief technology officer of design software company Cadence Design Systems, says the demands of the next generation of handsets mean that designers will have to take into account how the device will be used: "Now we have to talk about the modality. Designing for low power goes up to the highest level of behaviour in the system."

Power will have an increasing impact on how hardware and software are put together, he says: "Fortunately for Apple a lot could be done in the software. Imagine what would happen if the problem was in the hardware."

The need to do more with roughly the same amount of power will see increasing emphasis on designs that can shut down any part of a system when it is not being used, and which take account of the energy demands of specific protocols. Sideco sees a bright future for multicore systems.

"We are seeing that with laptops using quad-core processors. But to get the benefits you have to have software engines that are smart enough to throttle back the processors when you don't need the performance."

These considerations have driven two looks into the future of the mobile handset. They are a synthesis of ideas from phonemakers such as Nokia and technology suppliers such as chip-in-PCB company Imbera and touch-screen company Sharp Microelectronics. Although the designs are conceptual, they are constructed from technologies and ideas that have already been demonstrated, rather than pure concept designs such as the Nokia Morph.

So, welcome to tomorrow's teardowns.

The Clamshell

The core concept for Clamshell, the first of our pair of devices, comes from a Nokia video called 'Achieve' (http://bit.ly/kLog8 [new window]), which describes how a portable communicator - a possible successor to today's E90 - is used to plan an architectural project. Using a design reminiscent of the Psion Series 5 handheld computer, the machine has a small OLED display on the outside, showing simple messages such as the number of new emails and battery status. Opening the device reveals not just one but two flat-panel displays - an approach that the One Laptop Per Child organisation is considering for a future version of its portable computer.

Both the displays register multiple touches at once, with one used to provide a programmable keypad. Menus and icons provide access to the main functions, and a virtual keyboard can be pulled up when needed. Although capacitive touch-screens could provide the touch sensing, Sharp has an alternative proposal - build light sensors into the display matrix. Not only can the display register multiple fingers, it can also detect the difference between fingers and a stylus and even perform fingerprint recognition to work out whether the device is being used by its owner. The image sensors also enable the display to scan business cards and notes.

Like the Psion Series 5, physical buttons are built into the central hinge but they are programmable, using small OLED displays to show context-sensitive functions. Internally, the changes are more subtle, but represent the way in which device trends are likely to go. Multiprocessing is now a fundamental part of the product's design.

A move to soft-radio implementations means that the wireless base-band processor is a massively parallel multiprocessor that switches between different radio standards on the fly. For communication with computers in the cloud, it supports everything from GSM through 3G to Wi-Fi and LTE. A lot depends on where the machine is roaming, but it defaults to switching to the most power-efficient wireless standard wherever possible. For high data-rates it will attempt to use Wi-Fi, but move to GSM or a more efficient radio standard if the device is not being actively used for data and only has to check for push-email or social-networking status updates.

The main computer portion borrows concepts from the desktop PC but with a much stronger power-saving slant. Graphics processing units (GPUs) offload a lot of work from the host processor. Like the PC versions, the mobile GPU has many cores inside it, each one able to switch off when not in use. Instead of talking directly to a large bank of high-speed memory, as in a PC GPU, each mobile GPU has a large scratchpad memory on chip. The software is designed to load whatever it can into this area, only going to off-chip memory when large blocks are to be read or written.

Power consumption has a big effect on where the chips are placed on the two system boards. Because the display memory is much smaller than that needed to create 3D scenes, the GPUs are also the display controllers. Once a scene has been computed, the information passes through a display processor that takes into account ambient light to build the image. All the time it is tuning the light produced by the LED backlights. To minimise the distance between processors and memory and the power-sucking capacitive load of the buses, the GPUs and the host processor are buried inside the PCB. The memories sit on either side of the PCB, directly over these buried processors. The chip at the centre of the system is itself a multiprocessor - each processor onboard running at a comparatively low speed and off when not in use.

The processors talk to each other using low-voltage serial buses along the lines of the Unipro specification, being put together by the Mobile Industry Processor Interface (MIPI) group. MIPI is creating standards that use serial communications to link the major components in a handset. To enable designs to be assembled quickly to order, the serial buses enable chips to interrogate each other as to their functions. The handset, in effect, builds a picture of itself each time it is turned on.

The Powermiser

The same core architecture underpins Powermiser, a candybar-style handset that contains many of the same board-level components as Clamshell.

It has the host processor, soft-radio processor and GPU, but its peripherals are quite different. The main display is an e-paper screen. In some designs it rolls out to allow the handset to be used as an e-book. In low-end variants, it is a simple paper-like display that renders a colourful pattern when not in use. An LED-driven light-strip along the top illuminates the display in the dark.

The Powermiser is always looking for the most power-efficient way of sending data, even if it is slow, unless overridden by the user. So that it can be used as a computer on the move, users can add a portable keyboard and battery-driven wireless display. The keyboard is entirely self-powered, using the kinetic energy from keystrokes to send weak radio signals the few inches needed to reach the phone.

Rather than the Bluetooth of today's wireless keyboards, it uses a one-way protocol derived from work on wireless light-switches and sensors. It only uses Zigbee or Bluetooth to pair with the device in the first instance, using a small lithium cell to provide just enough energy for the job.

The display is powered by its own batteries and uses e-paper or OLEDs to keep the consumption down. The phone uses a low-power, short-distance protocol such as ultrawideband to send commands to a second GPU. The protocol makes heavy use of compression to limit the RF power needed.

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