A DSP based descrambler for digital satellite TV receiver

In this paper we implement a DSP based descrambler for digital satellite TV receiver. The descrambler is the core of the conditional access subsystem responsible of viewing restricted content broadcasted in received transport streams. We implement the descrambler algorithm in accordance with the common scrambling algorithm, which is used in scrambling digitally broadcasted transmissions, in native C programming language. Using DSP device TMS320C6713 @ 225 MHz and starting from the native C implementation of the algorithm, we propose multi-level compiler optimization guidelines to be applied on DSP based consumer electronic devices implementations in time critical applications. The proposed guidelines goal is to boost the processor performance up for achieving maximum processing speeds. The optimization guidelines proposed resulted in a performance enhancement of 58.6% when applied on our DSP based descrambler, as compared with the initial native C implementation for the algorithm.