5G RAN Architecture and Deployment Flashcards

What is the difference between TDD and FDD in Ericsson 5G NR spectrum usage?

Answer: FDD uses separate paired spectrum for UL/DL simultaneously; TDD uses the same frequency alternating UL/DL over time

FDD uses paired spectrum bands (separate UL and DL frequencies) operating simultaneously, while TDD uses a single band and switches between UL and DL in time.

In Ericsson's 5G deployment, what is the midhaul network?

Answer: The transport link between the CU and the DU in a disaggregated RAN

Midhaul refers to the transport segment connecting the gNB-CU (often centralized) to the gNB-DU, as distinct from fronthaul (DU to RU) and backhaul (CU to core).

What is Dynamic Spectrum Sharing (DSS) in Ericsson's 5G strategy?

Answer: A software feature allowing 4G and 5G NR to dynamically share the same frequency spectrum simultaneously

DSS allows LTE and NR to coexist on the same carrier, dynamically allocating radio resources between 4G and 5G users without requiring dedicated 5G spectrum.

In Ericsson's 5G RAN, what is the Xn interface used for?

Answer: Inter-gNB communication for handover and dual connectivity coordination

The Xn interface connects neighboring gNBs (or gNB and ng-eNB) to support handover signaling, dual connectivity bearer setup, and interference coordination.

What is Ericsson's 'Integrated Access and Backhaul (IAB)' technology?

Answer: A solution that allows a gNB node to simultaneously serve UEs and wirelessly relay backhaul traffic for other nodes

IAB nodes use 5G NR air interface for both access (serving UEs) and backhaul (relaying traffic to the network), enabling rapid dense deployment without fiber to every site.

What numerology feature in 5G NR allows Ericsson's RAN to support both low-latency and wide-area use cases?

Answer: Multiple subcarrier spacings (µ = 0 to 4) that scale OFDM parameters to different frequency bands and latency needs

5G NR defines multiple numerologies with subcarrier spacings of 15, 30, 60, 120, and 240 kHz, allowing the RAN to adapt slot durations for different latency and frequency band requirements.