Design of Programmable Baseband Processors
Abstract: The world of wireless communications is under constant change. Radio standards evolve and new standards emerge. More and more functionality is put into wireless terminals. E.g. mobile phones need to handle both second and third generation mobile telephony as well as Bluetooth, and will soon also support wireless LAN functionality, reception of digital audio and video broadcasting, etc.These developments have lead to an increased interest in software defined radio (SDR), i.e. radio devices that can be reconfigured via software. SDR would provide benefits such as low cost for multi-mode devices, reuse of the same hardware in different products, and increased product life time via software updates.One essential part of any software defined radio is a programmable baseband processor that is flexible enough to handle different types of modulation, different channel coding schemes, and different trade-offs between data rate and mobility.So far, programmable baseband solutions have mostly been used in high end systems such as mobile telephony base stations since the cost and power consumption have been considered too high for handheld terminals.In this work a new low power and low silicon area programmable baseband processor architecture aimed for multi-mode terminals is presented. The architecture is based on a customized DSP core and a number of hardware accelerators connected via a configurable network. The architecture offers a good tradeoff between flexibility and performance through an optimized instruction set, efficient hardware acceleration of carefully selected functions, low memory cost, and low control overhead.One main contribution of this work is a study of important issues in programmable baseband processing such as software-hardware partitioning, instruction level acceleration, low power design, and memory issues. Further contributions are a unique optimized instruction set architecture, a unique architecture for efficient integration of hardware accelerators in the processor, and mapping of complete baseband applications to the presented architecture.The architecture has been proven in a manufactured demonstrator chip for wireless LAN applications. Wireless LAN firmware has been developed and run on the chip at full speed. Silicon area and measured power consumption have proven to be similar to that of a non-programmable ASIC solution.
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