The digital part of the radio consists of three main sub-domains: Modem (MDM), Packet Build Engine (PBE), and RF Engine (RFE). Each of these sub-domains have their own internal processor and program memories for storing FW images (MCERAM, PBERAM, RFERAM). They also have separate register blocks for configuration of HW and various HW accelerators. The different sub domains have different responsibilities:
Modem (MDM)
The MDM domain is responsible for:
- Conversion from information/data bits to TX-symbols including:
- Preamble and sync word insertion
- Direct Sequence Spread Spectrum (DSSS)
- Forward Error Correction (FEC) encoding
- Demodulation including:
- Timing recovery
- Frequency offset estimation/compensation
- Rate offset estimation/compensation
- FEC decoding
Packet build engine (PBE)
The PBE domain is responsible for:
- Packet timing
- Composition and decomposition of radio packets
- FIFO handling
- Packet Handling Accelerator (PHA) for CRC and whitening
- Address checking
RF Engine (RFE)
The RFE domain is responsible for:
- Sequencing of analog modules
- PLL calibration algorithm
- Modulation/Shaping of the transmitted data
- Received Signal Strength Indication (RSSI) estimation
- Automatic Gain Control (AGC) algorithms