Software Defined Radio: Baseband Technologies for 3G Handsets and Basestations

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DSP for Basestations – The TigerSHARC

Michael J. Lopez, Rasekh Rifaat and Qian Zhang

Analog Devices, Inc., Norwood, MA

Cellular basestations are extremely complex systems that possess a different set of software-defined radio requirements than mobile terminals. A baseband board inside a basestation may have to process a hundred or more data streams and handle additional tasks such as multiantenna beamforming, mobility management, and interaction with the network infrastructure. This can lead to extremely high computational loads and data throughput. It also creates many difficult system design problems, including the issue of scheduling all of these tasks, probably among a number of different processors. A processing platform, therefore, must not only be able to handle the high number of computations, but also have sufficient memory and I/O bandwidth, and work seamlessly in a multiprocessor environment. Even size and power dissipation, while somewhat less constrained than in terminals, are still limited by board area, power supply, and thermal issues.

In the bigger picture, the long life and high development cost of basestations means that a given baseband architecture may need to support multiple generations along the cellular roadmap. For example, a service provider may transition from GSM to 3G, add advanced features such as multi-user detection, or switch to an OFDM-based system. This illustrates the attractiveness of a software-defined radio solution, as long as performance ...