For the WorldSpace satellite broadcast system the PC based Feederlink Station (FLS) provides a down sized solution for small or mobile broadcast studios. It performs all the necessary processing for one WorldSpace broadcast channel that can be feed into a Uplink terminal via a direct connection (e.g. local X.21 network) or for example telephone lines. The input of the station can be one analog or digital audio signal and / or one digital data stream. These inputs are processed into a maximum of two Service Components (SC) according to the WorldSpace digital format. MPEG 2.5 layer-3 encoding is used for the audio input. The SC are embedded into one Broadcast Channel (BC) that is provided at the Broadcast Channel Transport Interface (BCTI) output of the station.

For the PC based FLS the Fraunhofer IIS has developed a PCI PC extension card with three Motorola DSP56301 signal processors for the baseband processing. Using this card a standard PC running WindowsNT can be used without the need for high performance PC components (CPU, memory) or a realtime operation system. The card also provides all the necessary interfaces, as A/D converters, AES/EBU and S/PDIF receiver and digital input / output interfaces (e.g. RS232, X.21).

The software splits into two parts: The first one is the processing software running on the DSPs of the PCI card. It performs the realtime MPEG 2.5 layer-3 audio encoder and the necessary baseband processing for the Service Components and the Broadcast Channel multiplexing. The second part is the software package running on the PC containing a WindowsNT Service, low level system drivers and a Control Panel Application. The task of the Service is configuration and monitoring of the PC based FLS. For this purpose it interfaces via Ethernet to the WorldSpace Local Monitoring and Controlling System and performs the necessary operations via the low level system drivers to the DSP software. The status of the processing and the active configuration can be observed by the Control Panel application.