Baseband design boom fuelled by cutting edge and emerging markets
A smorgasbord of new chips aims to feed market-wide demand for smartphones
The uptake of smartphones is driving rapid innovation in the chips that enable them. At the low end, handset makers want affordable devices for emerging markets. At the high end, demand for advanced features such as 3D HD playback is seeing chipmakers push manufacturing processes to the limit. Meanwhile, there have been key advances in the air interface and control of the modem design.
At the 2011 Mobile World Congress (MWC) in Barcelona, Paul Jacobs, chairman and CEO of Qualcomm, said five factors were driving market growth.
The first is smartphones, which accounted for 440 million of the 1.4 billion handsets sold in 2010. The second is devices such as tablets and e-readers. The third is advanced air-interface technologies such as HSPA+ (aka Evolved High Speed Packet Access). Fourth is the global shift from 2G to 3G: of 1.4 billion handsets sold in 2010, 650 million were 3G models; in 2011, 775 million of 1.5 billion handsets will support 3G. The fifth is emerging markets: there were 842 million mobile subscribers in China last year, and just 15 per cent are so far on 3G networks.
'If you tie the smartphone and emerging markets together you see why we are trying to drive the cost point down,' Jacobs said.
Jacobs isn't alone in spotting the opportunities offered by emerging markets.
MediaTek, a Taiwanese fabless semiconductor company, is launching a low-cost chip that supports mainstream 3G smartphone functions. Although priced for emerging markets, the design does not skimp. The MT6573 forms the basis of a Google Android OS handset and includes a quad-band, 3G/HSPA modem; a 650MHz ARM11 core; 3D graphics support from Imagination Technologies' POWERVR5 core; support for a touchscreen of up to 854 x 480pi (FWVGA) resolution; video capture and playback at 30frame/s; and support for an 8Mpi camera.
'We see a huge appetite for lower-cost smartphones but it is being addressed by sacrificing user experience and features,' said Jeffrey Ju, general manager of MediaTek's smartphone business unit. 'We believe our MT6573 platform enables our customers to meet this consumer demand and bring unprecedented levels of performance to lower-priced smartphones.'
Broadcom has come to the same conclusion and launched another variation on the theme, a 3G baseband processor for Android handsets based on an ARM Cortex A9 core and its own 3D graphics. The BCM21654 includes a 3G/HSPA modem; support for 12Mpi cameras; 30frame/s H.264 video recording and playback; and dual SIM support. It is built on a 40nm manufacturing process.
Even as established suppliers target emerging markets, local > < players are setting their sights on the leading edge of the global market. Xincomm, in Hefei, China, is developing a dual-mode long-term evolution (LTE) baseband chip to work with both the time-division (TDD) multiplexing scheme favoured at home and the frequency-division scheme (FDD) used elsewhere. The company says its chip will support 4 x 2 and 2 x 2 multiple-input/multiple-output (MIMO) antenna schemes. With two receive antennas and one transmit antenna, a handset would achieve 100Mbit/s downloads and 50Mbit/s uploads.
Integration is key
These new chips are based on the rapid integration of standard, or de facto standard, functions on leading-edge manufacturing.
'In mobile, the people who voted against integration have lost,' said Jacobs. 'The work we have done in integration for emerging markets has come back to Western markets in chips for machine-to-machine communications.'
Many baseband chip vendors use ARM cores to handle general-purpose computing. At MWC, ARM launched two variants of its Cortex family, the R5 and R7, optimised for LTE and LTE-Advanced devices.
The differentiators, for vendors of all sizes, are how many cores they use, of which type, and how well they are implemented.
Broadcom has aimed to ensure it gets the most out of its commitment to ARM by signing a licence agreement that gives it access to the company's range of current and future cores.
For Qualcomm, it is all about implementation. The company's Snapdragon family is based on an optimised ARM core and has found favour in Windows 7 handsets. Qualcomm says it has 60 design wins for the dual-core version.
Steve Mollenkopf, executive vice-president and group president of its chipset business, said his was the first company to introduce a 1GHz implementation of the ARM core: 'It is virtually impossible to sell a high-end chipset without 1GHz performance.'
Qualcomm has updated Snapdragon with the core microarchitecture on a new process: 'The cores are capable of going up to 2.5GHz – a brand new bar for the industry.'
Mollenkopf claims the core will offer the same performance at 65 per cent of the energy consumption, or 50 per cent greater performance at the same consumption, which could lead to chips that need fewer cores.
The new Snapdragons are available with one, two or four cores in variants with up to four 3D graphics units. The single and dual-core versions have an integrated multi-mode (FDD and TDD) LTE modem, while the quad-core part works with a separate modem chip. All include Wi-Fi, GPS, Bluetooth, FM and near-field communication support, as well as stereoscopic 3D video and photo capture and playback. They will be built on the latest 28nm process.
ST-Ericsson's response is its Nova application processors, Thor modem chips and integrated NovaThor devices.
The flagship Nova A9600 is based on what the company claims is 'the industry's best and most efficient low-power implementation' of a dual ARM Cortex A15 core, running at up to 2.5GHz 'thanks to innovative power-saving techniques to be disclosed later this year'. It will also be built on a 28nm process.
The chip will use a next- generation POWERVR Rogue graphics core from Imagination, and play back full-HD video at 120 frames per second, supporting professional camcorder-quality capture in 3D.
The need for speed is driving development of advanced air interface technologies, such as dual and multimode versions of HSPA+, and multimode LTE modems.
ST-Ericsson's Thor modem chips boast both those specific capabilities and are backwards compatible with 2G and 3G. They support up to eight frequency bands and will handle calls either by falling back to a circuit-switched network or the voice-over-LTE standard some operators have chosen.
Broadcom's top-of-the-range smartphone baseband chip, the BCM28150, is used in Nokia's N8 handset. It includes an HPSA+ modem capable of 21Mbit/s download. The part illustrates another trend in baseband chip design, with heavy use of coprocessors to offload specialist tasks from the dual 1.1GHz Cortex A9 cores. The chip's ARM Neon 128bit SIMD (single instruction, multiple data) coprocessor deals with applications such as Adobe Flash and a proprietary graphics core handles 3D rendering.
Qualcomm released a modem chipset that supports Release 9 of HSPA+, which enables download speeds of up to 84Mbit/s. The MDM8225 supports MIMO antennas and the aggregation of HSDPA carriers on different frequencies. This gives operators more flexibility in how they use their spectrum. The part supports dual-carrier uplinks for faster uploads.
The chip also includes Qualcomm's Interference Cancellation and Equalization (Q-ICE) receiver, which improves the radio's performance in multicell environments. Again, it will be built on a 28nm process.
Although advanced process technologies make highly integrated baseband chips and high-speed modems possible, there is no getting away from the fact that sending more data requires more RF energy.
According to Mollenkopf at Qualcomm, some of its latest modem chipsets will use an envelope-tracking technology to adjust the power provided to the RF section to match the instantaneous power it is using.
'Qualcomm has its own envelope tracking technology called Q-POET,' Mollenkopf said. 'It allows you to stay within the thermal envelope to get into smaller devices.'
Envelope tracking is not new, although its implementation is based on improvements to the technology that cut the energy it demands of basestations.
Maturing the envelope
Nujira, based in Cambridge, has been delivering its Coolteq envelope-tracking technology for a couple of years and continues to develop test chips for phones.
Nujira says its envelope-tracking power modulators can save over 1W in an LTE terminal, enabling a single multiband, multi-mode power amplifier to transmit 20MHz 4G signals using less power than single-band 3G power amplifiers. The technology has been licensed to an unnamed 'tier one' semiconductor vendor that is developing an envelope tracker to replace the DC-DC converter in handsets.
'4G terminals will not work without envelope tracking,' claimed Tim Haynes, CEO of Nujira. 'Using standard power architectures, 4G terminals will use 75 per cent more power than today's 3G terminals, and require up to seven PA modules to cover the allocated spectrum. With envelope tracking, terminals will use 30-50 per cent less power and require just two PAs.'
Nujira set up the OpenET Alliance, a group committed to a standard interface for envelope tracking and NXP Semiconductors has launched a pair of DACs and ADCs that use it.
Analogue specialist Maxim is also looking at managing RF power amplifiers in this way.
'We have an envelope-tracking device that is now sampling. It is a complex high-bandwidth part and has to be sited close to the PA,' said Jon Horner, its executive director. 'Envelope tracking needs high bandwidth to get the full linearity necessary to avoid the distortion that would undermine advanced modulation schemes.'
Maxim sells a less complex power-management device that does power tracking for multimode and multiband PAs, in which the collector voltage through the PA is adjusted based on the peak transmit power. According to Horner, the device is simpler because it does not need to work at such a high bandwidth as a true envelope tracker.
Technologies from consumer electronics and communications are being brought together in the latest smartphones. Running the latest air interfaces demands tens of billions of operations a second. The 3D graphics that we are seeing on gaming consoles and top-of-the-range TVs will soon go everywhere with us in our pockets or bags. The tri-band global GSM handset will soon be replaced by LTE products supporting up to 17 bands.
The common enabling threads of these rapid advances are leading-edge manufacturing processes, proven design tools and flows that enable rapid integration and, of course, the engineers who bring them all together. *
ARM's DIY spin-off
Buying baseband chips from leading providers gives you highly integrated designs on the latest manufacturing processes. In return, you give up choice and control.
Cognovo, a spin-off from ARM, is trying to persuade OEMs to design their own baseband chips using its software-defined modem core.
According to Pascal Herczog, chief technology officer, the problem with baseband silicon is that the air interface function is cast into the chip and the only person who can write software is the original designer.
The Cognovo approach gives users control of how they want to implement the hardware and the software.
'If something is wrong then you don't have your future in your own hands,' said Herczog. 'A separation of software and hardware opens up the game.
'Any number of semiconductor companies could now do a baseband chip because they don't need 500 people to make an equaliser. OEMs will want this for control and profitability. For semiconductor makers it allows them entry to the market and enables them to offer OEMs more flexibility.'
Herczog sees his customers as 'companies who are selling millions of handsets and don't want to pay Qualcomm prices'.
The heart of the Cognovo approach is the Ardbeg vector signal processor. Its instruction set and architecture comes from an analysis of the mathematical functions necessary to implement the algorithms used in the wireless standards.
Herczog says running the LTE air interface takes 50 to 60 billion multiply-accumulate operations per second. LTE-Advanced could take 10 times as many.
Cognovo has taken the basic core and wrapped it in sequencers, controllers and interfaces to build a 'modem compute engine'. Software development tools enable engineering teams to work on implementing air interfaces from the top down.
If you want to know what's will happen next in wireless chip design, one good place to look is imec, the nanoelectronics research centre based in Leuven, Belgium.
It has already commercialised a configurable processor array that offers enough on-chip computing power to handle complex air-interface algorithms. The centre used this year's MWC to show off the kind of spectrum-sniffing chip that will be essential to future 'white space' radios that will seek out unused spectrum in their local environment and use it for as long as it remains clear.
Liesbet van der Perre, director of green radio programs at imec, said: 'We think the chip will be important for use in white-space spectrum from the TV bands, and for coexistence in the ISM bands.'
She added that the spectrum sniffing chip will also be important for good channel selection in femtocells, and for LTE, which could be implemented on up to 17 different frequency bands: 'If an operator wants to get the most out of their spectrum, this is going to be huge.'
The DIFFS digital front-end chip can perform both flexible synchronisation and spectrum sensing for high-throughput WLAN (802.11a-n), cellular (including the recent 3GPP-LTE), and digital broadcasting standards.
It connects to imec's reconfigurable analogue radio chip (SCALDIO) and its programmable digital baseband platform to form COBRA, imec's take on a 'cognitive radio baseband architecture' (COBRA), which is designed to multimode communication with efficient use of the available spectrum.
The DIFFS chip is built in a 65nm process and will migrate to 40nm. The SCALDIO design, which is an update of a previous version, can sense bands from 100MHz to 6GHz, and when sensing draws only 'milliwatts', according to van der Perre.
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