"In a highly illuminating presentation, Adam Gould, director of CDMA technology creation for Nokia Mobile Phones, quantified the increased gate count that 3G phones would require from ASICs, and the consequent impact on battery life. The 8- and 16-bit systems (with 16 Mbits of memory) that were once clocked at 10 MHz will become 16- and 32-bit systems (with 64 Mbits of memory) clocked at a battery-draining 100 MHz, Gould said. While speech coding will still require 30 Mips, radio channel processing will leap from 30 Mips with a 2G phone to more than 200 Mips for 3G. Video coding, moreover — something that did not exist in 2G — will take another 200 Mips of processing power in the third generation. Meanwhile, the logic gate count of ASIC devices will have risen from about 100,000 gates in 1997 to 500,000 in 2002 and more than 1.5 million to support 3G phones."
Batteries take on wireless challenge
By Stephan Ohr
EE Times
(10/06/00, 1:11 p.m. EST)
SAN DIEGO — The changing needs of Internet phones and wireless PDAs will drive rechargeable-battery development, plenary speakers said at September's Arthur D. Little Power2000 conference.
Speakers including Michael Mace, chief competitive officer for Palm Inc., and Curtis Sasaki, director of marketing for consumer and embedded products at Sun Microsystems Inc., spoke of the challenges to battery life posed by third-generation (3G) cell phones, integrated MP3 and multimedia, as well as Bluetooth and other forms of wireless connectivity.
The needs of 3G phone and multimedia players — even the addition of global positioning system (GPS) capability — will create a need for new battery chemistries and form factors, charge controllers and voltage regulators, the speakers said.
Palm's Mace, for example, asked for battery form factors that resembled credit cards in thickness and weight; while Keven Coats, a system designer with Texas Instruments Inc.'s Internet audio group, spoke of the power savings that could accrue — 11 mW to be precise — if the clock on a C54-based MP3 decoder could be cranked back from 52 to 35 Mips, just what is needed to get the job done.
Sasaki of Sun said that the proliferation of wireless devices like smart phones, two-way pagers and connected PDAs will elevate the volume of data traffic. Demonstrating an early-generation handheld Internet phone from LG Electronics that offered downloadable animated games, Sasaki argued that embedded Java could minimize the code requirements for mobile processors, which would clip their cycle time and power consumption. On the device side, color LCDs and multifunction connectivity (Bluetooth wireless and MP3 players in cell phones, for example), along with increased voice and data traffic, will continue to tax battery life.
A consortium of 23 companies supporting Java recently approved the "wireless profile," a graphical user interface and persistent-data-storage model for Java, Sasaki said. But future developments such as location-based services and "impulse" service delivery will have an impact on battery life.
Java follows the Internet business model, in which the necessary code to run an application on your computer or handset is downloaded from the site you are visiting, Sasaki explained. While there is a need to involve the operating system of the handheld device, there is nothing yet in Java that would serve as a fuel gauge — though its minimal code space can be employed to minimize clocks.
In a highly illuminating presentation, Adam Gould, director of CDMA technology creation for Nokia Mobile Phones, quantified the increased gate count that 3G phones would require from ASICs, and the consequent impact on battery life. The 8- and 16-bit systems (with 16 Mbits of memory) that were once clocked at 10 MHz will become 16- and 32-bit systems (with 64 Mbits of memory) clocked at a battery-draining 100 MHz, Gould said. While speech coding will still require 30 Mips, radio channel processing will leap from 30 Mips with a 2G phone to more than 200 Mips for 3G. Video coding, moreover — something that did not exist in 2G — will take another 200 Mips of processing power in the third generation. Meanwhile, the logic gate count of ASIC devices will have risen from about 100,000 gates in 1997 to 500,000 in 2002 and more than 1.5 million to support 3G phones.
What saves the day is the decreasing power per gate that comes with shrinking CMOS geometries, said Gould. From a whopping 1 microwatt per MHz per gate in 1994, power consumption has shrunk to roughly 0.1 microwatt per MHz per gate today. But since so much logic is required by today's cell phones, the overpower requirement has appeared to rise. The trick will be squeezing out increased battery life, when the 3G phone — embodying MP3 player, FM radio, videogame player and PIM database — will see increasing usage even without an active call.
Individuals will still expect 50 to 300 hours of standby time with 3G, Gould said. But they will demand from four to six hours of talk time, two to four hours of Web browsing, 20 to 40 hours of MP3 music playback, 200 hours of FM radio play, three hours of videogame time and over 15 hours' access to a GPS locator.
If the same phone gets used as a source of electronic cash (like a bank portal) or a PIM, then the battery must never go down, Gould said. Users will never accept a dead battery as the reason they can't access their cash, he said.
The convergence of services may pave the way for a lot of oddball battery sizes. Avoid them, said David DeMuro, manager of advanced product realization for Motorola's Energy Systems Group.
The need for new configurations, sometimes embodying new chemistries, will mean significant choices for chargers, power supplies and voltage regulators, he said. Battery chargers and regulators will likely embody one type of power management intelligence; voltage regulators and fuel gauges within the portable handset will embody a different kind of intelligence. In terms of system partitioning, secondary voltage regulators will increasingly be included within the case of the battery pack, DeMuro projected, though the main issue will be costs.
DeMuro's observations underlined introductions of smart battery products by Texas Instruments and SmartPower, and a lithium-ion charging circuit from Dallas Semiconductor. The Dallas part simplifies design with a built-in current-sense resistor, a built-in temperature sensor and a voltage-measuring A/D converter. It uses a one-wire asynchronous protocol rather than an SMBus to report battery status to a host.
Other speakers hammered on the 3G power issue. Peter Loomis, staff scientist for Trimble Navigation Ltd., described the "time to first fix" as the primary cost to battery power in global positioning systems. While GPS systems are as small as 0.4 ounce and cost under $100, the 135 battery-munching seconds — about 220 mW — it takes to triangulate a new position among satellites can be quite costly to battery life.
Rather than initiate a new search on every refresh, Loomis recommended minimizing searches — and processor clocks — by storing a "previous position" in battery-back RAM. This "warm start" would reduce the amount of time for a positional fix to 38 seconds, and bring the amount of power it takes down to 43 mW.
Thus, with extended battery life, GPS can support not only 911 emergency services but also can be used to track animals in the wilderness. One example Loomis cited is the collar on a grizzly bear. "Let me tell you," said Loomis, emphasizing the need for GPS power conservation, "nobody wants to service the battery on that."
Although the conference has traditionally focused on portable power consumption, the new attention to the power requirements of rechargeable PDAs, MP3 players and Internet phones provided additional interest at this year's event, the eighth annual, which drew more than 1,000 engineers and technical managers. |
