Analog Devices, Inc. announced the SoftCell Multicarrier Transceiver Chip set, which allows smaller, more powerful base stations to be optimized for cellular/PCS, Wireless Local Loop (WLL), Micro/Pico Cell, and Smart Antenna systems. SoftCell is a functionally complete end-to-end, IF-to-digital transceiver chip set that enables true "software radios" to be deployed for wireless infrastructure applications.

ADI's SoftCell chipset addresses key issues for wireless operators including the cost of coverage, flexibility and size, as well as quality of service. Base stations containing the SoftCell chip set will be easy to modify in terms of adding services, additional channels, and changing wireless standards incrementally. In effect, operators will have the ability to use and move between any air interface standard (e.g., GSM, PHS, D-AMPS), deploy a higher number of channels and offer frequency plans with greater efficiency. The new architecture also eliminates redundant channel radios for both transmitters and receivers.

The SoftCell chip set is optimized for four RF carrier channels and is easily expandable. The solution enables equipment manufacturers to create highly scalable multicarrier, multi-mode base stations at a fraction of the cost of traditional multi-channel base stations. Implementing a single 4-channel receiver with SoftCell results in a 36 percent savings, with the cost per channel savings increasing dramatically for higher channel designs. For example, operators can realize a 2:1, or 60 percent savings, when implementing the SoftCell solution in a 10-carrier base station.

"At Analog Devices, we are committed to developing leading-edge silicon solutions to help the wireless industry create smaller, yet more powerful base stations in order to quickly expand the global wireless infrastructure," said Thomas Gratzek, Product Line Director for Analog Devices' Digital Radio Group. "The SoftCell chip set brings us significantly closer to reaching this goal, and positions us as a leading provider of next-generation infrastructure technology for third-generation wireless systems."

The decrease in size and cost savings associated with SoftCell means base stations can be deployed in higher numbers and in tighter locations. The result is better coverage, better quality, and fewer busy signals for users. The deployment capability also makes the SoftCell chip set well-suited for wireless office applications. In addition, the "software radio" technology implemented in the chip set enables new applications such as Smart Antenna or phased-array antenna services that enable power efficiencies and cost savings, and small "picocell" installations for additional coverage capacity and in-building wireless systems.

The speed of high resolution ADCs and DACs has reached a point where all sorts of interesting combinations of parts will be seen in the development of base stations making the direct conversion from baseband to IF and back. This approach by Analog Devices is one of the first to address the multiple channel base station and will be an immediate hit. I rather dislike the SoftCell moniker that has been given to the series.

The heart of the system are the converters. The receiver ADC -- the AD6644 -- is capable of handling 100 dB of dynamic range and offers a 77-dB signal-to-noise ratio with 14-bit 80-MHz sampling. The transmit DAC -- the AD8754 -- is also 14-bit and is the latest in the Analog Devices' series in this field. The processors on both the receive and transmit channels provide the filtering and tuning for all four channels, and provide the channel-fashioning for the particular standard of transmission/reception. Because of adjacent-channel interference the receive process filtering is more complicated than the transmit. Both processors are controlled by the local DSP. The receive processor is a multi-channel version of the AD6620 which has been available for some time. As most base stations operate in multiples of four channels the four-channel approach is the right way to go. The flexibility of the parts will allow for some considerable cross-fertilization of design talent over the various wireless industry standards.

Although in many cases there seems to be an over-specifying trend by the wireless industry, not understanding that the RF side of both the receiver and transmitter are more of a problem than the converters now are, the quality of these parts will allow even wider channel use in the near future.