From signal models and reference-signal resource elements to packet flow, QoS, HARQ, random access, protocol conformance and the RF, compute and channel conditions that determine what a real NR modem can achieve.
Follow both user-plane packet flow and the complete control-plane bootstrap from SSB and MIB through SIB1, PDCCH monitoring, PRACH, RAR, Msg3 and contention resolution.
Trace simultaneous video-call and browser packets through QFI, SDAP, PDCP, RLC, MAC multiplexing, the transport block, LDPC and the air interface, then reverse the path at the gNB.
Walk one packet through NR →Separate end-to-end QoS intent from radio implementation, see why multiple QFIs can share one DRB, and understand exactly what SDAP contributes.
Separate QoS from bearer state →Trace initial access end to end: SSB and MIB bootstrap, CORESET#0/SearchSpace#0, SIB1, PRACH resource selection, RA-RNTI, RAR PDCCH monitoring, Timing Advance, Msg3 scheduling, TC-RNTI, Msg4 contention resolution, collisions, timers and retries.
Trace the complete RACH procedure →A four-part implementation-oriented series connecting MAC HARQ processes, DCI control, LDPC parity, soft buffers and long-delay NTN operation.
Why a HARQ process is not a CPU thread, what TX and RX buffers actually hold, how failed decoding preserves soft information, and how LLR combining works.
Open the HARQ state machine →How dynamically scheduled transmissions identify a HARQ process, how NDI distinguishes new data from retransmission, and why RV is not a transport-block identifier.
Decode the control fields →Distinguish CRC bits from LDPC parity, follow the circular-buffer rate-matching process, and see why incremental redundancy is stronger than simply repeating a packet.
Derive incremental redundancy →Separate UE capability from RRC configuration and per-transmission PID selection, then connect HARQ pipeline depth and soft-buffer cost to NTN delay.
Size the HARQ pipeline →These foundations connect signal processing and protocol requirements to what real modem implementations, test laboratories and networks actually verify.
Why orthogonality gives Tu = 1/Δf, why LTE selected 15 kHz, how normal CP produces 14 symbols, and what a complete 10 kHz alternative would change.
Derive the NR time-frequency grid →The MIMO capacity proof, singular spatial modes, DM-RS and CSI-RS inside NR slots, LS/LMMSE estimation, channel aging and hardware-constrained arrays.
Build MIMO from first principles →Why 3GPP writes testable requirements but does not certify products, what regulatory, GCF, PTCRB and operator testing cover, and how a non-conforming modem can still reach users.
Follow the verification chain →