ABSTRACT
Three processors usually exist in a communication terminal system: the digital signal processing (DSP) baseband processor (BBP), the DSP application processor (APP), and the microcontroller (MCU).
Baseband signals are all signals in a radio system, which are not modulated onto the carrier wave. In a cellular phone, this means all signals except those in the radio frequency (RF) part of the phone. This chapter discusses processors for digital baseband signal processing, known as digital baseband DSP processors (DBBP). Figure 23.1 defines the basic partitioning of a radio communication system from both functional and hardware points of view. A DBBP plays an important role in both the transmitter and the receiver. In a transmitter, the DBBP converts the data from application sources to a format adapted to the radio channel. In a receiver, a DBBP recovers symbols from the distorted analog baseband signal and translates them to a bit stream with acceptable bit error rate (BER) for applications. Figure
23.1(b) describes functions in a DBBP. The most power-consuming parts are in the receiver, with functions such as synchronization, demodulation, and forward error correction. This chapter introduces the implementation of low-power DBBP. Detailed theory and knowledge of DSP for digital communications may be found elsewhere [2].
