Re: GPRS - GPRS Chipsets
>> Laying The Groundwork For The Next Generation
Electronic Buyers News
Dec 11 2000
Demand for higher-speed wireless data services shows no signs of letting up, even though regulatory bodies are struggling to build a consensus for a 3G air interface and rollout dates are beginning to slide as service providers face the daunting task of migrating from current protocols.
The market for devices capable of providing faster access to e-mail and delivering wireless information services such as online banking, shopping, audio/video applications, and fast database access remains solid, according to vendors.
"Of the 1.8 billion phones in use by 2006, we expect over 50% will be using 2.5G or 3G technology," said Ashi Majid, group product marketing manager for wireless ICs at Infineon Technologies AG in San Jose.
However, with the migration to 3G technology proving more challenging than expected, 2.5G promises to play an important role as an intermediate step up in data rates. While a number of technologies are competing in this arena, General Packet Radio Services (GPRS) is looking increasingly attractive as the lowest-risk path to next generation data services for a growing number of wireless-service providers.
"It's quickly emerging as the wireless datapipe of choice at this point," said Doug Grant, director of business development for RF and wireless systems at Analog Devices Inc., Norwood, Mass.
Unlike most wireless voice networks, which are based on circuit-switched topologies, GPRS uses a packet-switched approach to give wireless users access to significantly higher data-transmission speeds. In a traditional circuit-switched network, any connection for data transmission is dedicated and the user is billed by minutes of use. Moreover, the service provider cannot offer that channel to anyone else while the connection is operational.
"If you do a circuit-switched connection, you tie up the capacity for the length of the transaction," Grant said.
Packet-switched approaches take advantage of the burst-oriented nature of data transmissions by routing packets through a shared medium to their destination. By sharing channels across multiple users, service providers can sell the same channel to a broader customer base.
And since the technology allows users to be billed on a cost-per-packet basis independent of the time spent online, it offers users a better deal. With GPRS, users can transmit data at rates in excess of 100 Kbits/s, significantly faster than current capabilities, and fast enough to provide a wealth of new Internet-based services over a wireless connection.
Phones with packet switching offer another key benefit: they're always connected, so users don't have to make a call every time they want to get online.
"The WAP phones are taking off, and the primary reason is that every time you want to surf the Web, you have to go through a complex call-setup routine," said Behrooz Abdi, general manager of Motorola Inc.'s RF/IF Division in Austin, Texas. "That's very annoying. With GPRS, you're always connected, similar to the i-mode phones that have proven very popular in Japan."
But the most attractive feature of GPRS systems is its conformity with existing GSM networks. Designed as an extension to the existing GSM system, GPRS services use the same channels, modulation scheme, and network backbone of current networks, significantly simplifying implementation.
"It's a pretty easy upgrade from the existing GSM network," Grant said. "The hardware is essentially the same on the infrastructure side, and it uses the overall network backbone that GSM uses already. It's primarily a software exercise in billing."
Leading wireless-IC and handset manufacturers are already developing the devices and partnerships needed to deliver this capability to markets around the world. In October, China's Ministry of Information announced a number of GPRS design wins for U.S. companies.
GPRS development efforts include a partnership between Lucent Technologies Inc., Murray Hill, N.J., and Konka Group in Shenzhen, China, as well as Motorola's joint venture with Hangzhou City, China-based Eastern Communications Ltd. Texas Instruments Inc., Dallas, is working with China's ZTE Corp. and Xiamen Overseas Chinese Electronic Co. Ltd. in a similar venture.
In Hong Kong, service providers are rolling out GPRS systems and expect as many as 30% of all subscribers to use the technology by the end of 2001. And Lucent has begun trial operation of new GPRS systems in Australia, Germany, and Malaysia.
The impact of GPRS on baseband-IC performance varies significantly, depending on the application, according to Grant. GPRS regulatory organizations have defined a slew of classes for GPRS-compliant devices based on voice and data requirements, how easily it will be to switch from one to the other, and how many slots are used.
At the higher classes, performance requirements can have a significant impact on handset design. GPRS classes 13 through 18, for example, require full-duplex operation and therefore a radio chip capable of simultaneously transmitting and receiving.
Classes 19 through 29 require that the system be capable of using most of the slots at the same time and therefore place additional burden on the power amplifier and other handset functions. For these reasons, no OEMs to date have developed handsets to meet these stringent requirements, according to Grant.
"From what we can see, Class 12 is pretty much the sweet spot, and the configuration most people seem to be going for is four slots down, one slot up, for a total of five, which is the most you can do in Class 12," he said.
Given the plethora of features OEMs will be able to offer in this market, IC manufacturers are taking a highly programmable approach to baseband solutions.
One example is Analog Devices' SoftFone AD20msp430 chipset. The two-chip set includes the AD6522 digital baseband processor based on the ADSP-218xx DSP core and an ARM7TDMi RISC processor with Thumb extension, and the AD6521 baseband converter, which provides the interface to the radio. Completely RAM-based, the chipset is designed to enable phone manufacturers to easily customize features.
Typically, an OEM could load different software versions to support an entire family of handsets-ranging from high- to low-end-using the same hardware platform. The chipset was selected earlier this year by Novatel Wireless Inc., a San Diego-based developer of wireless systems, as the platform of choice for a new GSM/GPRS network.
Texas Instruments is supporting development of GPRS devices with its Open Multimedia Applications Platform. A completely programmable environment, the OMAP architecture integrates a software infrastructure, an ARM RISC processor, TI's TMS20C55x DSP, and a shared memory architecture on a single piece of silicon.
The software architecture is designed to support advanced operating systems and applications through standard application programming interfaces, while a DSP/BIOS bridge allows developers to partition tasks between the RISC processor and DSP to maximize performance.
"While a DSP for a traditional GSM phone will typically run at a clock rate of 39 MHz, when you go to GPRS, you really need something that is running in excess of 100 MHz," said Michael McMahon, director of R&D at TI's wireless business unit. "OMAP has processing resources well beyond what GPRS requires."
TI and Microsoft are collaborating on an integrated GSM/GPRS solution for handsets and portable devices based on a derivative of OMAP and optimized for Microsoft's smart-phone platform. The so-called "Stinger" devices will integrate a third processor, an ARM9 core, into TI's dual-processor baseband IC to run applications.
"It's the most highly integrated implementation of a smart-phone architecture that's out there today," McMahon said.
TI's OMAP baseband IC has also been selected to run in a number of leading 3G wireless applications, including next-generation handsets from Ericsson, Nokia, and the Visor handheld computer from Handspring Inc., Mountain View, Calif.
A high degree of programmability was also a key design goal in Motorola's DSP56690, a baseband device the IC supplier introduced last year for 2.5G applications. Designed for TDMA, CDMA, GSM, iDEN, and satellite applications, the dual-core IC combines a 100-mips, 104-MHz 56600 DSP with a 30-mips, 52-MHz MCore microcontroller. Future derivations of the baseband chip are expected to add Bluetooth and HomeRF capabilities.
In October, Philips Semiconductors, Eindhoven, Netherlands, extended its OneC family of baseband devices with its own GPRS solution. The OneC-GPRS+ supports Class 12 and worldwide GSM roaming capability.
Packaged in a 180-contact flip-chip plastic BGA, the device adds embedded SRAM to enable its ARM processor to run at 39 MHz internally and optimize performance of built-in peripherals such as UARTs. The new baseband chip is compatible with Philips' UAA3535, a triple-band GPRS Class 12 RF transceiver announced last year.
At the same time, Philips added a power amplifier designed for GPRS handsets to its product portfolio. The CGY2015 is a triple-band GSM900/1800/1900 GaAs MMIC power amplifier designed to operate from a nominal 3.6-V battery. The new IC only requires a 30-dB harmonic low-pass filter to comply with the transmit spurious specification.
Market Race
As service providers race to deliver higher-performance data transmission to their customers, time-to-market is crucial to success in the GPRS market.
Some smaller handset manufacturers are looking for chip suppliers that offer solutions that are as highly integrated as possible. This is particularly the case in China and other emerging countries, where cell-phone makers may need help with reference designs, board layout, relationships with contract manufacturers, and other value-added services.
"We deal with a couple of handset manufacturers who are looking for a cookie-cutter approach to developing a basic phone," said Dennis Schlaht, technical marketing manager responsible for wireless products at Insight Electronics in San Diego. The distributor works with basestation manufacturers on component selection, design test, and other development issues.
Component manufacturers are also offering more complete turnkey services. Lucent Technologies' Microelectronics Group, for instance, provides a complete GPRS reference design that the company claims can shorten development time for handsets by up to four months.
The multiband platform can support GPRS up to Class 8 technology in a footprint as small as 100 x 40 x 8 mm. The tiny design uses Lucent's Sceptre 3 system-on-a-chip technology, based on the company's DSP16000 architecture, to integrate a microcontroller and mixed-signal functions on chip. It also features the W3020 GSM RF chip.
The GPRS protocol stack and related software are provided by Optimay GmbH, a Lucent subsidiary in Germany. The platform includes Full Type Approval for the module, including the baseband, radio, power-management functions, and user interface.
"Wireless-handset manufacturers are keenly interested in delivering GPRS products to market to support data-intensive applications such as Internet browsing, but most of them would rather not spend time and resources to work on the design and FTA approvals," said Lance Hiley, strategic marketing manager of the Mobile Appliances Division at Lucent's Microelectronics Group.
That's particularly true for OEMs providing phones for Far Eastern markets like China, Majid said.
Infineon recently announced Full Type Approval for a dual-band GSM/GPRS reference design developed by its subsidiary, Danish Wireless Design. The system platform is built around three Infineon chips: the E-Gold baseband controller, the Smarti+ RF transceiver, and the E-power power-management IC. Supporting software was developed by Comneon.
"With this reference design, an OEM can basically purchase our solution, wrap plastic around it, and have a product," Majid said.
A longtime leading supplier of GSM silicon, Infineon announced at the same time the shipment of its 100 millionth GSM baseband chipset.
Garnering RF support
Key to meeting low-cost, low-power consumption targets for next-generation GPRS devices will be enhanced RF capabilities. As the market gradually makes the transition from second- to third-generation technologies, the ability to support multiple bands and multiple modes will likely be crucial.
The stakes are high.
The worldwide market for RFICs in cell phones will jump from just below $5 billion this year to $7.7 billion by 2004, according to market researchers at Strategies Unlimited.
GSM handsets represent the largest market for RF semiconductors, followed by CDMA, IS-136 TDMA, Personal Digital Cellular, and analog chipsets, according to the Mountain View, Calif., research firm.
In late September, Motorola introduced a digital-transceiver IC with those applications in mind. The software-programmable BiCMOS MC13760 functions over a range of input frequencies to support multiple wireless standards, including AMPS, DCS, GPRS, GSM, and TDMA. The device links directly to Motorola's baseband processors through a common programming and data interface. Motorola expects to see the IC used not only in cellular handsets, but PDAs, satellite phones, iDEN, and TETRA radios as well.
The MC13760 introduces a high-performance BiCMOS process that allows the device to operate at 2.75 V and provide a deep-sleep mode with drain current as low as 50 microamps. In addition, the MC13760 features fractional-N synthesizers, a reconfigurable zero IF receiver with programmable bandwidth, receive A/D conversion, a multirate data interface to the baseband DSP, a direct-launch digital modulator, and full transmit support circuits. By supporting operation at VHF and UHF bands, the device allows designers to develop innovative architectures that combine cellular and conventional two-way or trunked radio.
The chip's zero-IF-type architecture enables it to support multiple protocols, Abdi said. "While most receivers perform a dual conversion, this IC does a single conversion down to 400 MHz and then goes directly baseband through an IQ channel," he said. "At that point, the filtering becomes baseband filtering and it's all integrated into the chip. You no longer have to be switching filters on the board; it's all programmed internally."
Analog Devices is pursuing a different path. The analog specialist claims its Othello chipset is the first open-market direct-conversion RF device. <<
- Eric - |
