NB-IoT random access — NPRACH and attach

NPRACH — Narrowband Random Access

The Narrowband Physical Random Access Channel uses single-tone preambles at 3.75 kilohertz subcarrier spacing, hopping across the available subcarriers in a defined pattern to provide diversity. A cell can configure up to three NPRACH resource sets — one per Coverage Enhancement Level. CE Level 0 uses the fewest repetitions and is for UEs in good coverage. CE Level 2 uses the most repetitions for UEs in the deepest coverage. The UE measures the downlink reference signal power, estimates its path loss, and selects the appropriate CE level and matching NPRACH resource. This staircase design…