The number of mobile broadband subscribers (using W-CMDA, EV-DO,
HSPA, LTE, and Mobile Wimax) is expected to surpass two billion by
2013, with LTE alone reaching 440 million subscribers by
2015.
This growing demand for next-generation wireless broadband
introduces a new level of complexity. 4G networks are intended to
provide users with data rates of more than 100Mbit/s.
Compared to current W-CDMA networks that support data rates of
2Mbit/s with additional rates improvements for HSPA, 4G modems will
require almost a twenty-fold increase in processing
horsepower.
In spite of the significant increase in complexity, handset OEMs
are still allocating the same power budget for 4G designs in order
to fit into battery-powered devices.
Designing a powerful and cost-effective communications IC that
meets these stringent power constraints poses a fundamental
challenge to the SoC designers.
Routes to 4G baseband
Although the term 4G is widely used to describe the next step in
wireless communication, we are still lacking a precise definition
of the architecture and its deployment path.
Analysing the routes to 4G wireless baseband, there are two
evolving technologies that are competing for the leading position:
LTE and Wimax.
Wimax has emerged as the technology of choice for computing devices
such as notebooks, netbooks and MIDs. It is heavily promoted by the
Wimax Forum, led by Intel and other companies. The deployment of
Wimax has already begun but its success is far from being
secured.
LTE is evolving as the “GSM” direction towards cellular broadband
and is promoted by the 3rd Generation Partnership Project (3GPP).
Consequently, it appears to be the preferred choice for mobile
handsets and smartphones as it is widely promoted by baseband OEMs
and operators including: Qualcomm, Ericsson, Verizon, Vodafone and
others.
It is unclear which 4G standard will prevail, and it is possible
that both standards will coexist and serve different uses in
different geographies.
The changing standards increase risk with a traditional,
hardware-based design approach. IC designers using such an approach
can either find themselves betting on the wrong standard and end up
with an obsolete product before even being launched, or getting
into costly investment by developing dedicated chips for each of
the two standards, with no guarantee of a return on
investment.
To ensure that both standards are supported in 4G modems, a
flexible approach is preferred, and this means a programmable
engine capable of delivering the required performance.
Multiple interfaces
The evolution of mobile modems is not restricted to the complexity
increase of wireless standards. Today’s smartphones already need to
support multiple wireless air interfaces. 4G mobile devices will
need to support, alongside Wimax and LTE, a large number of
wireless air interfaces, including GSM, GPRS, EDGE,
W-CMDA, HSPA, Wi-Fi, Mobile TV (DVB-H) and Bluetooth.
Traditional hardwired solutions require multiple dedicated baseband
modules, each targeting a different standard. For addressing
multiple standards, such hardwired solutions require the
duplication of large silicon areas, making them very costly. Hence
such an approach cannot economically keep pace with the growing
number of evolving standards.
A software-based approach that offers multimode systems support and
can replace multiple dedicated baseband systems seems to be the
right direction. In addition, this rapid evolution requires a more
efficient development process. Reusing the same platform over
multiple product generations is essential.
A programmable approach enables the required reusability and
ensures fast time-to-market.
As we move to 4G, the cost of development and the changing
standards increase the risk of a traditional, hardware-based design
approach. This naturally leads to looking at a programmable
multimode solution. Still, there is a huge challenge in providing a
programmable system that is capable of handling the tremendous
processing demands of 4G standards under stringent power
consumption constraints.
Standard programmable architectures cannot efficiently address
these challenges. The best approach is a specialised communications
processor that is optimised for the most demanding wireless
standards.
Such a communication-specific programmable approach can address
these performance and flexibility challenges and enable efficient
4G modem designs.
Eyal Bergman is director of product marketing at Ceva.