Challenges in Data-Center Technologies for Distributed Radio Signal Processing. Raymond Knopp EURECOM, Communication Systems Department

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1 Challenges in Data-Center Technologies for Distributed Radio Signal Processing Raymond Knopp EURECOM, Communication Systems Department

2 Some visions of 5G and beyond 5G and beyond is not only New Radio and verticals It is also evolution in computing for wireless networks Central offices becoming data-centers (see CORD / M-CORD projects in USA as an example) High-performance fronthaul networks for distributed computing Fixed network to support advanced radio Centralized computing and storage using More general-purpose equipment (Intel servers) More and more software technologies from cloud-computing (NFV,SDN,MEC, etc.) jointly with radio signal processing Applicable to lesser extent for existing and evolving 4G radio Fusion of Information and Cellular technologies OAI - CRAN Playground

3 ITU IMT2020 FG Vision Source: OAI - Project 4

4 ITU-Vision for Open-source and 5G Source: OAI - Project 4

5 NGFI (IEEE 1914) Fronthaul Vision Main target of EURECOM deployment OAI - Project 4

6 Considered RAN Splits in 3GPP evolution MME 5G CORE Capacity-Limited Backhaul High capacity Backhaul Fronthaul Lowlatency FH Highlatency FH MME LTE-RLC LTE-MAC LTE-PHY LTE-PHY Radio RRC 5G-RLC 5G-MAC 5G-PHY Low latency FH Split 5G-PHY Radio Heterogeneous PDCP 5G-RLC 5G-MAC 5G-PHY MEC RAN Cloud Higher latency FH Split LTE-RLC LTE-MAC LTE-PHY WIFI MAC WIFI PHY 6

7 OpenAirInterface Software Alliance Project 4 Short-term goal: Manual for up to 50 RRUs and BBU pool align with ITU/NGFI/3GPP architectures for fixed network and data center RAN/CORE Replication of this test network globally to carry out PoCs / Research in the following areas: Network Slicing Study split of PHY Data Center / RRU (IEEE, NGMN, specs) Interface with commercial RRHs over CPRI Orchestration of BBU pool in Intel/ARM based cluster using automated virtualization tools Address real-time, HW abstraction issues when running future RAN in containers and KVM. Work closely with other open source groups (OSM, JuJu, OpenStack, OpNFV and ONOS) make it replicable (open-access to technology) and based on current OAI RAN and EPC Interoperable with COTS UEs Commercial EPC Evolve towards 5G as 3GPP progresses (below 6 GHz access) Generic cloud computing equipment and new architecture (XEON + FPGA) 100% open-source Reference Platform for 3GPP/IEEE/ETSI/NGMN Based on Open Source tools (OAI + others) + Proprietary HW/SW IP Blocks OAI - Open-Source Solutions for 5G

8 NGFI fronthaul splits today in OAI Current OAI implementation (RRU/RCC) supports either IF5 time-domain fronthaul (> 1 GbE required) IF4.5 split (FFTs) (280 Mbit/s/antenna port fronthaul 20 MHz carrier) per carrier/sector Under development mixed IF1 / IF4.5 IF1 for super-pdcp OAI - Project 4

9 Why split? TX Full L1 TX in RRH => fronthaul link is 150 Mbit instead of 2 Gbit/s MAC (scheduler) must provide Transport channel SDUs (common and dedicated) Any precoding information (issue if massive precoding is used, just a second ) RX RX split is less clear Depends on number of UEs / RE / RRH (i.e. MU detection per RE) And on models for realistic uplink resources (average MCS) in dense deployments FFT output (32-bit / RE) (576 Mbit/s (100 PRB) / RRH antenna port (TX or RX) Common signal processing User-specific signal processing I[n] Digital Baseband Q[n] Inputs Prefix Extraction FFT I[k] Q[k] Channel Compensation I[k] Q[k] LLR Unit Channel Decoding Current CPRI RRH (30-bit / IQ sample Time-domain) ~922 Mbit/s / RRH antenna port (TX or RX) Channel Estimation Pilot extraction LLR only (8-bit / coded bit / UE) 804 Mbit/s (100 PRB mcs19), 538 Mbit/s (100 PRB mcs 11) OAI - CRAN Playground

10 OAI - CRAN Playground

11 OAI - CRAN Playground

12 Example: Massive MIMO RRS OAI - CRAN Playground

13 Example: Indoor DAS RRS OAI - CRAN Playground

14 OAI - CRAN Playground

15 EURECOM RRH to Datacenter Architecture Main CLOUD (Legacy Services) EPC + ClearWater IMS, FreePCRF (OpenStack + JuJu) Some issues Distributed computation Cheap synchronization Loosening of control/userplane coupling Real-time I/Q over Eth links (copper, low-cost fiber) S1APGTPu S1APGTPu enb enb enb LOCAL CLOUD (Low-latency Services) S1APGTPu 20 GbE (switched) 10GbE (IF4) CPRI GW CPRI Small-cell RRU L1L 1GbE (IF4) macro-cell RRH L1L Small-cell RRU L1L Small-cell RRU L1L Atomic Clock OAI - Project 4

16 CRAN Equipment Deployment of CRAN playground at EURECOM 50 Low cost RRU Dense servers x86-64 Xeon (today) Optical (10/20/100 GbE) and copper (1 Gbe) distribution RCC/RAU (COTS Intel Server Technology) RRU Example Radio Cloud Processing units OAI - Project 4

17 RRUs (Experimental) Band 7(FDD),38 (TDD),42/43 (TDD) Up to 25 dbm output 20 MHz BW 1 or 2 antennas per RRU <1000 euros / RRU Pico-ITX form factor (100mm x 72 mm) Intel Atom E3845 or X7-8300, <10W TDP PoE from aggregation switch 10 MHz reference from clock distribution at aggregation switch 1GbE front-haul per RRU MIMO/MU-MIMO done via multiple RRU OAI - Project 4

18 Targeted Indoor deployment (1 outdoor RRH) OAI - CRAN Playground

19 Conclusions We want people to take this, experiment and enrich in a community-driven effort Contribute to the software Replicate the hardware Integrate with other hardware Push to standards bodies (e.g. ITU, ETSI, 3GPP) and upstream in other communities (e.g. OPNFV) Use for PoC demonstrators (5GPPP and other project programs) OAI - CRAN Playground