Software radio increasingly becomes a powerful tool for academic wireless research as well as industry prototyping due to its flexibility and programmability. Implementing wireless protocols on software radio in practice, however, remains a challenging task. It is mainly due to the lack of an efficient modular software architecture for high-performance digital signal processing (DSP). This document describes Brick, a modular software architecture for creating baseband processing programs on Sora software radio platform. The Brick programming model is designed for synchronized data flow processing, where fine-grained components are interconnected to form a directed processing graph. The Brick library is highly flexible and efficient. It has been integrated on Microsoft Research Software Radio (Sora) platform.