How SDRs can make 4G and white spaces usable

Caroline Gabriel, Rethink Research
19 Dec 2008

In the developed mobile world, new technologies like Wimax and LTE will have to live alongside several other systems, and consumers will increasingly want to be able to roam seamlessly across different networks according to cost and availability - especially if open-access models start to take off in earnest. This will place new momentum behind the bid to make multimode devices more complex, and yet cheaper and less power hungry.

Packing more and more radios on to a single chip is one approach, as pursued by Qualcomm (though no support for Wimax yet). A stage beyond that comes the software programmable processor, which can be tweaked in software, by the handset maker or operator, to support a flexible combination of network connections. Sandbridge Technologies this week announced its contribution to this nascent market, with its SB3500, a 65nm reprogrammable software-based baseband processor, which can be adapted to LTE, HSPA, Wimax, W-CDMA, Wi-Fi,


and the mobile TV standard DVB-H.

Configurable baseband

The Sandbridge processor is entirely software-based, and points to the vision of a fully cognitive radio in future - a single radio that can move intelligently between different networks, according to parameters such as cost or signal strength. Indeed, a workshop hosted by Intel last week demonstrated how much progress has already been made towards that dream.

Because the Sandbridge platform is programmable, cellphone makers can use a single architecture to support phones with different combinations of radios, reducing their costs. Sandbridge's technology will also reduce the number of chips needed in a phone, which should cut cost, time to market and complexity. The company claims the cost savings can amount to 15% across design and production, and the figure could grow as consumers look for more and more functions to be packed into one low power unit.

Another advantage that Sandbridge claims for its technology is that handset makers can respond more quickly to standards changes - such as the next wave of 802.16e, or even the shift to 802.16m - testing and adding new functions rapidly in software rather than waiting for the chipmaker to deliver upgraded hardware. Changes in standards can also be easily accommodated, so operators could move to new networks even before standards are finalized, with reduced risk.

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