System Architecture

The processing flow of an LTE physical downlink shared-channel (PDSCH) which is the major part of a LTE receiver is illustrated in Figure 1. Note the modem implementation presented in this paper only includes the physical layer assuming higher layers (e.g., Radio Link Control and Media Access Control) are handled by one or two microprocessors. However, in this paper, higher layers are out of the scope of the presented work. The key modules in the flow are presented in the following sections.

Digital Front-End (DFE)

The DFE unit is the bridge between the Analog Front-End (AFE) and Digital BaseBand (DBB) part in the wireless systems. The function of DFE is usually gain control, sample rate conversion, pulse shaping, matched filtering and sometimes phase adjustment. Generally speaking, it is mainly a block of digital filters. Although from a functionality perspective the DFE is rather simple compared to other baseband blocks which diversify according to various standards, it still consumes a significant portion of the die area and power. A configurable DFE which supports multiple standards is included in the baseband processor.