ETCP 5G RAN Architecture and Deployment 2 — Questions and Answers
Question 1: What is the difference between TDD and FDD in Ericsson 5G NR spectrum usage?
- TDD uses separate frequencies for uplink and downlink; FDD uses the same frequency with time slots
- FDD uses separate paired spectrum for UL/DL simultaneously; TDD uses the same frequency alternating UL/DL over time (Correct answer)
- TDD supports only voice; FDD supports only data
- FDD requires Massive MIMO; TDD does not
Correct 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.
Question 2: In Ericsson's 5G deployment, what is the midhaul network?
- The transport between the core and the internet peering point
- The transport link between the CU and the DU in a disaggregated RAN (Correct answer)
- The link between the RU and the DU
- The link between two gNBs for coordinated scheduling
Correct 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).
Question 3: What is Dynamic Spectrum Sharing (DSS) in Ericsson's 5G strategy?
- A method to share a single antenna among 4G and 5G radios physically
- A software feature allowing 4G and 5G NR to dynamically share the same frequency spectrum simultaneously (Correct answer)
- A spectrum auction process for national regulators
- A roaming agreement framework between operators
Correct 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.
Question 4: In Ericsson's 5G RAN, what is the Xn interface used for?
- Connecting the gNB to the UPF
- Inter-gNB communication for handover and dual connectivity coordination (Correct answer)
- Connecting the RU to the DU via fronthaul
- Carrying timing signals between gNBs
Correct 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.
Question 5: What is Ericsson's 'Integrated Access and Backhaul (IAB)' technology?
- A solution that allows a gNB node to simultaneously serve UEs and wirelessly relay backhaul traffic for other nodes (Correct answer)
- An indoor antenna system for enterprise deployments
- A fiber backhaul product for dense urban areas
- A joint product with a third-party ISP for backhaul provisioning
Correct 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.
Question 6: What numerology feature in 5G NR allows Ericsson's RAN to support both low-latency and wide-area use cases?
- Multiple subcarrier spacings (µ = 0 to 4) that scale OFDM parameters to different frequency bands and latency needs (Correct answer)
- Fixed 15 kHz subcarrier spacing inherited from LTE
- Variable coding rate selection per frame
- Adaptive modulation between QPSK and 256-QAM only
Correct 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.
ETCP 5G RAN Architecture and Deployment 2
What is the difference between TDD and FDD in Ericsson 5G NR spectrum usage?