4G/LTE - Basic Procedures  




Downlink Subframe Decoding

This procedure will explain the overall procedure to decode user data (PDSCH). It assumes that Initialization, Synchronization, IB decoding, Registration is already done and UE is in connected mode. This process happens on UE's PHY Decoding process.

    i) Process the first OFDM symbol of the first slot within a subframe.

    ii) Detect PCFICH channel and figure out how many symbols are used for PDCCH.

    iii) Decode PHICH channel (PHICH is also at the first symbol of the first slot). This gives you ACK/NACK for PUSCH

    iv) Based on the result of step i),ii), UE will calculate CCE index for PDCCH (Refere to PDCCH Decoding for detail)

    v) Decode PDCCH and find DCI (DCI1 or DCI1A) which is destined to the UE.

    vi) From the DCI, figure out the physical resource information (e.g, location, modulation scheme etc) for PDSCH which is allocated for the UE.

    v) Decode PDSCH