This paper presents the design and use of reconfigurable stream processors for the physical layer processing in wireless base-stations. Stream processors, traditionally used for high performance media processing, use clusters of functional units to provide support for hundreds of functional units in a programmable architecture. We provide hardware support for reconfiguration in stream processors, enabling them to be power-efficient by adapting to the compute requirements of the application. We demonstrate the real-time implementation of a 32-user wireless base-station, employing multiuser channel estimation, multiuser detection and Viterbi decoding physical layer algorithms, supporting a data rate of 128 Kbps/user. The reconfigurable stream processor runs at 1.2 GHz and has an estimated power consumption of 12.38 W at full workload. However, basestations rarely operate at full capacity. When the base-station workload decreases, the reconfigurable stream processor adapts the number of clusters, functional units, voltage and frequency dynamically for power efficiency. When the application workload changes to 4 users, the reconfiguration support reduces the power to 300 mW at 433 MHz, providing a 41.27X decrease in power consumption. The cluster reconfiguration yields an additional 15-85% power savings over a stream processor with dynamic voltage and frequency scaling.