We present an open source LTE receiver framework. Using GNU Radio’s block-based signal processing capabilities, various LTE baseband specific functionality has been implemented in dedicated easily reconfigurable blocks. These can be used to decode and analyze arbitrary channels in the LTE downlink signal. As an example we decode the Master Information Block (MIB) transmitted on the Broadcast Channel (BCH) and the Physical Control Format Indicator Channel (PCFICH). Our work is focused on the software receiver design in GNU Radio and on performance measurements in order to identify critical processing operations on a General Purpose Processor (GPP). By optimizing critical components, e.g. channel estimation, synchronization, we can improve the overall performance and therefore the system’s real-time capabilities.