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OpenAirInterface Overview and Lab Session 1

OpenAirInterface Overview and Lab Session 1. www.openairinterface.org. Provides open-source (hardware and software) wireless technology platforms target innovation in air-interface technologies through experimentation We rely on the help of

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OpenAirInterface Overview and Lab Session 1

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  1. OpenAirInterface Overview and Lab Session 1

  2. www.openairinterface.org • Provides open-source (hardware and software) wireless technology platforms • target innovation in air-interface technologies through experimentation • We rely on the help of • Publicly-funded research initiatives (ANR,ICT,CELTIC) • Direct contracts with industrial partners • Widespread collaboration with a network of partners using open-source development and tools • LINUX/RTAI based SW development for PCs • LEON3/GRLIB-based HW and eCos/MutexH-based SW development for FPGA targets • LINUX networking environment • Experimental Licenses from ARCEP (French Regulator) for medium-power outdoor network deployments • 1.9 GHz TDD, 5 MHz channel bandwidth • 2.6 GHz FDD (two channels), 20 MHz channel bandwidth • 800 MHz FDD (two channels) : 10 MHz channel bandwidth

  3. OpenAirInterface Development Areas OPENAIR3 : Wireless Networking All-IP, Mobility Management, 802.21, Cellular/Mesh Routing Protocols, Mesh Topology Management, Multimodal Radio Resource Management Cognitive Technologies Wideband RF, Agile Spectrum Management, Interference Management and Control, Distributed/Collaborative techniques, Spectrum Sensing, Cognitive and Flexible Radio Architectures, Ambient Networking OPENAIR2: Medium-Access Protocols Cellular topologies, single-frequency resource allocation, cross-layer wideband scheduling, Mesh topologies, distributed resource control OPENAIR1: Baseband/PHY Advanced PHY (LTE), Propagation Measurement and Modelling, Sensing and Localization Techniques, PHY Modeling Tools OPENAIR0: Wireless Embedded System Design Agile RF design, Reconfigurable High-end Transceiver Architectures, FPGA prototyping, Simulation Methodologies, Software development tools, low-power chip design

  4. Collaborative Web Tools • OpenAirInterface SVN Repositories • All development is available through www.openairinterface.org’s SVN repository (openair4G) containing • OPENAIR0 (open-source real-time HW/SW) • OPENAIR1 (open-source real-time and offline SW) • OPENAIR2 (open-source real-time and offline SW) • OPENAIR3 (open-source Linux SW suite for cellular and MESH networks) • TARGETS : different top-level target designs (emulator, RTAI, etc.) • Partners can access and contribute to our development • OpenAirInterface TWIKI • A TWIKI site for quick access by partners to our development via a collaborative HOW-TO • Soon • Sourceforge distribution of stable code

  5. Equipment and SW

  6. Prototype Equipment Timeline Planned replacement for CBMIMO1 ExpressMIMO2 AgileRF/Express MIMO CBMIMOI – V1 CBMIMOI – V2 PLATON/RHODOS 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Cellular, AdHoc and P2MP Topologies FPGA SoC (Virtex 5)+ Interface for partner Processing Engines Agile Tuning module (0.2 – 7 GHz) Maximum Channel BW 20 MHz OFDM(A)/WCDMA AdHoc/Mesh and Cellular Topologies FPGA-SoC (Virtex 2) 2x2 OFDM(A) @ 2 GHz, 5MHz channels Cellular (towards LTE) Cellular Systems Pure Software Radio WCDMA-TDD All-IPv4/v6

  7. Software Roadmap OpenAirDAB OpenAir.11p OpenAir4G OpenAirInterface (WIDENS/CHORIST) WIRELESS3G4FREE 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 LTE compliant waveform Mesh extensions from WIDENS/CHORIST Partial 3GPP protocol stack (openair2) AdHoc/Mesh and Cellular Topologies In-house MIMO-OFDMA TDD waveform (WiMAX 2004 like) Distributed Signal Processing and Mesh-Topology functions (L2.5 relaying) TD-SCDMA SDR IPv6 interconnect No longer supported

  8. CardBus MIMO 1 • Current platform for application experimentation and test network deployments • 5 MHz channel bandwidth TDD@1900 MHz • PCMCIA-CardBus form-factor • 2x2 MIMO-OFDMA, LTE waveform • Two-way communications • Full Software Radio under RTAI/Linux on x86 architectures

  9. Current CBMIMO1 V2 Designs • CBMIMO1 provides • A Leon3-based embedded processing engine on a Xilinx XC2V3000 FPGA • 52 MHz processor speed • 64 kByte embedded memory (16 Mbyte SDRAM not used currently) • DMA engine for PCI/CardBus burst transfers • AD9862 acquisition engine • LTE TDD/FDD framing (7.68 Ms/s) • LTE 5 MHz baseband filtering (TX) • Digital Frequency-correction • LTE FFT (TX, 512-point), regular cyclic-prefix processing (TX/RX) – 2009 firmware • Note: For LTE, limited to OFDMA transmission formats (i.e. no SC-FDMA, true SRS, etc.) and extended prefix mode • Generic SDR TX – 2011 firmware • No limitations for LTE, except dual-antenna TX on some PCI configurations (laptops) • Will not work properly in TX direction with off-the-shelf CardBus<->ExpressCard adapters because of insufficient upstream reads • RF control (gains, frequencies, timing of RF) • CBMIMO1 allows for 2x2 MIMO operation in either FDD (with external RF) or TDD • Embedded software handles LTE framing and transfers of signals to/from PC memory along with synchronization events for RTAI scheduling • PC configures CBMIMO1 with memory regions for signals and frame parameters on init and card does the rest • Special frame resynchronization for two-way operation is provided (timing drift adjustments)

  10. ExpressMIMO Baseband Prototyping Board • FPGA-based baseband platform • One Virtex 5 LX330, One Virtex 5 LX110T (PCIexpress) • 4x AD9832 (dual 14-bit 128 Ms/s D/A, dual 12-bit 64 A/D 64Ms/s) • Up to 8x8 MIMO capacity with low-IF, 4x4 I/Q Baseband • Low-jitter clock generation for converters • 128 Mbytes/133 MHz DDR (LX110T) • 1-2 Gbytes DDR2 (LX330) • CompactFlash (SystemACE), JTAG Configuration • PCIexpress 8-way interconnect (4-way in practice) • LVDS expansion interface (daughter boards) • RF interface (micro-coax and parallel I/O for Microwire busses)

  11. ExpressMIMOSoC Target (cont’d)

  12. ExpressMIMO/ExpressMIMO2 Application Development • A software application (MODEM + MAC) is a C program running on a micro-controller (LEON3) with HW API for DSP • SW library is available (libembb), developped and maintained by LabSoC, TelecomParisTech (openair0) • Same approach as x86 SDR (CBMIMO1) but on an embedded system • More difficult to validate functionality -> Software models for HW required • Current testcases • DAB/DMB (MODEM implementation by TUM/BMW) • OpenAir.11p : full PHY and multicast/broadcast component of MAC • Dual-mode receiver (i.e. both MODEMS share the same HW, two threads in SW) • Next step • Port of OpenAir4G to ExpressMIMO • Training • Acropolis Winter School 2011 (OAI2)

  13. ExpressMIMO2 Platform • Recall • CBMIMO1 platform : cheap, fixed band, 5 MHz channels, 3G EVM (RF) characteristics (2 bits/s/Hz limit), SDR/x86, good for networking experiments, many fabricated for EURECOM and partners • ExpressMIMO + AgileRF : very expensive, arbitrary band, 20 MHz channels, SDR/MPSoC, good for architecture exploration, few fabricated for internal use only • Objectives for new platform • Low-cost of CBMIMO1 (<2k€ for baseband board) • Networking experiments (tens of nodes) • As frequency agile as possible (for multimodal operation and CR/DSA experiments) but not total flexibility like AgileRF (low cost) • High performance RF (LTE compliant performance) for state-of-the-art MODEM design • Interconnection possibilities with high-power RF for basestation deployment • Optimize partition of x86 and FPGA DSP for rapid-prototyping

  14. Elements • Baseband/RF engine (first prototypes imminent) • Spartan 6 LX150T FPGA (PCIexpress like ExpressMIMO) • Derived from Xilinx/Avnet evaluation board (but smaller, medium-sized PCIe format) • Used for FFT and Turbo/Viterbi decoders (key processing bottlenecks) • Control of RF and acquisition from converters • 4 LIME Semiconductor zero-IF RF chipsets • TX, RX and A/D, D/A on single-chip (1.5cm x 1.5cm) • 300 MHz – 3.8 GHz tuning bandwidth • FDD or TDD operation • LTE UE, RN RF compliance (EVM), even better (this is really good) • 0 dBm output power

  15. Elements

  16. Elements • PC • PC runs RTOS (RTAI) like CBMIMO1 • MAC + remainder of PHY (low-complexity components) • Linux kernel network interface • Low-end x86, embedded x86 • RF front-ends (PA/LNA, duplexing, filtering) – External boards developped by InsightSIP (local company) • Extra frequency transposition to go to 4-6 GHz • 21 dBm PAs (5-6 GHz, 2 GHz, UHF) • FDD with standard Duplexer solution for 2 GHz • TDD with tunable filters (Hittite) and TX/RX switch for all other bands (focus on 3.5 GHz, 5-6 GHz, 1.9 GHz) • Existing EURECOM basestation front-ends (1.9 GHz, 2.6 GHz and UHF)

  17. OpenAir4G MODEM

  18. Purpose • Develop an open-source baseband implementation of a subset of LTE Release-8/9 on top of OpenAirInterface.org SW architecture and HW demonstrators • Goals • Representative of LTE access-stratum • Full compliance of LTE frame (normal and extended prefix) • Full Downlink shared channel compliance • Support for a subset of transmission modes (2x2 operation) • Modes 1,2,4,5,6 (Mode 3 to be studied for inclusion) • Support for up to 3 sectors in eNB • Useful for measurement campaigns • Useful as starting point for research-oriented extensions (to justifiably claim potential impact on LTE-A) • Provide realistic (and rapid) LTE simulation environment for PHY/MAC (OAI3 lab session)

  19. OpenAirLTE PHY/MAC Protocol Stack (partial 3GPP, openair1, openair2) Linux networking device (IPv4/IPv6, classification/routing Services for DRB) 36-331 ASN.1 messages Compliance Subset of LTE-only procedures PDCP is an empty box 3GPP Compliance 36-322 Rel-9 3GPP Compliance 36-321 (v 8.6) Openair1 3GPP Compliance (v8.6) 36-211,36-212,36-213

  20. Current Status (LTE/LTE-A) • PHY (36.211,36.212,36.213) • LTE softmodem for 5 MHz (1.5, 10 + 20 too, but not completely functional yet) • Subset of 36-211,36-212 and 36-213 specifications • Mode 1, Mode 2 and Mode 6 support • Enhanced-Mode 5 and Mode 4 under integration (SAMURAI) • Missing elements (the rest is largely supported) • User-selected feedback (not planned) • Modes 3,7 (not planned) • Rel-9/10 enhancements (Carrier Aggregation, Modes 8,9) under integration • MAC (36.321) • Full random-access procedure, Scheduling Request, Buffer Status Reporting • eNB scheduler is incomplete (to be built per application) • UE Power headroom under integration • RLC (36.322) • Complete UM/AM implementation, SRB interfaces with RRC for the moment

  21. Current Status • PDCP (36.323) • Currently just provides DRB interface for linux networking device • No security and compressions features • New implementation under integration (PDCP headers, SRB interfaces, opensource ROHC integration) • RRC (36.331) • Two separate actions, RRC LITE and Cellular • LITE • is LTE only, with ASN.1 messages (asn1c C code generator) and subset of LTE RRC procedures (RRCConnectionRequest/Setup,ReconfigurationRequest) • Empty security context establishment will be added • Currently integrating measurement reporting and MobilityControlInfo (handover) • Extendable for Mesh networks (LOLA) • No SAE NAS support currently, but could be added … • Cellular • Inherits RRC from W3G4Free (IP/UMTS) • Automatic code generation using Esterel Studio • “hand”-compressed messages and research-oriented NAS extensions for IPv6 interconnect (QoS and mobility management)

  22. OpenAir4G Lab Session 1

  23. Objectives • Familiarization of OpenAir4G Development Environment through a simple example • Insertion of kernel modules for CBMIMO1/ExpressMIMO hardware • Control of HW with OCTAVE (signal acquisition) • Basic DSP example • LTE Initial synchronization • Control of HW with user-space C programs (signal acquisition) using OpenAir4G x86-based DSP • Basic principles of Real-time operation under RTAI with CBMIMO1

  24. Directories • targets • Specific SW targets (SIMU,RTAI) for instantiating OpenAir4G components • openair1 • Basic DSP routines for implementing subset of LTE specifications under x86 (36.211, 36.212, 36.213 3GPP specifications) • Channel simulation, sounding and PHY abstraction software, • openair2 (not for this lab session) • MAC/RLC/PDCP/RRC • openair3 (not for this lab session) • L3 IP-based Networking elements and applications

  25. Compiling and Loading the kernel modules • Start from $OPENAIR1_DIR • Kernel modules for CBMIMO1 and ExpressMIMO are made as • make oai_user.ko (ExpressMIMO) • make openair_rf_cbmimo1_softmodem.ko OPENAIR2=0 (CBMIMO1) • This creates one module (as well as other things …) • openair_rf.ko • Interfaces for openair1 running in user-space • PCI/PCIe driver for CBMIMO1/ExpressMIMO • RTAI threading interfaces • LINUX character device interfaces (open,close,ioctl,mmap)

  26. Compiling and Loading the kernel modules • Loading can be done with scripts found in $OPENAIR1_DIR • Try • make install_oai_user • Make install_cbmimo1_softmodem OPENAIR2=0 • sudo (if not root) because insmod is needed (do cat start_rf.sh) • The module should now be attached to the kernel (do lsmod) and the leds on CBMIMO1 should be moving (ExpressMIMO nothing …) • Identifying the HW • To see that the HW is identified by Linux you can do lspciand you should see either • “European Space Agency …” which is the identifier for the GRLIB (Gaisler) embedded system in CBMIMO1 • “Xilinx Corporation …” which is the identifier for the Xilinx PCIe endpoint on ExpressMIMO • To see that the HW is identified by the openair_rf driver do dmesg and you should see traces of one of the two cards

  27. PC Environment at this point • SW in the PC looks (looked!) like Linux char device interface for control / non-real-time acquisition and generation

  28. PC Environment at this point • SW in the PC looks like Linux char device interface for control / non-real-time acquisition and generation LXRT (user-space real-time)

  29. User-space applications • Dialogue with driver through • open/close (access device through fileops) • ioctl : basic instructions to control HW / RTAI • mmap : access shared memory buffer (signals, measurement information, etc.) • Dialogue with RTAI threads through • RT-fifos (/dev/rtfXX) • Two methods • OCTAVE .oct files (like MATLAB .mex) with ioctl interfaces for OCTAVE users (note: GPIB .oct files available too using libgpib to control measurement equipment, e.g. signal generator, spectrum analyzer) • C/C++ programs

  30. Build an OCTAVE Application • The OCTAVE scripts and .oct files are in • cd $OPENAIR1_DIR/USERSPACE_TOOLS/OCTAVE/CBMIMO1_TOOLS • To compile the .cc to .oct files (note: octave-headers needs to be installed), do make oarf OPENAIR_LTE=1 (and make gpib if you want gpib) • Examine rx_spec.m as an example (or rx_spec_exmimo.m)

  31. OCTAVE example dual_tx=0; oarf_config(0,1,dual_tx) gpib_card=0; % first GPIB PCI card in the computer gpib_device=28; % this is configured in the signal generator Utilities->System cables_loss_dB = 6; % we need to account for the power loss power_dBm = -95; %gpib_send(gpib_card,gpib_device,['POW ' int2str(power_dBm+cables_loss_dB) 'dBm']); %gpib_send(gpib_card,gpib_device,'OUTP:STAT ON'); % activate output oarf_set_calibrated_rx_gain(0); % turns off the AGC oarf_set_rx_gain(80,85,0,0); oarf_set_rx_rfmode(0); s=oarf_get_frame(0); f = (7.68*(0:length(s(:,1))-1)/(length(s(:,1))))-3.84; spec0 = 20*log10(abs(fftshift(fft(s(:,1))))); spec1 = 20*log10(abs(fftshift(fft(s(:,2))))); clf plot(f',spec0,'r',f',spec1,'b') axis([-3.84,3.84,40,160]); %gpib_send(gpib_card,gpib_device,'OUTP:STAT OFF'); % activate output legend('Antenna Port 0','Antenna Port 1'); grid Init card (freq 0, tdd, 1 TX antenna) If GPIB is used RF configuration Get 10ms of signal from RX chains

  32. LTE Initial Synch Example • Need a few basics in LTE DL Transmission (OFDM + QAM) • Frame formats • Synchronization signals • Primary Synchronization Signal (PSS) • Secondary Synchronization Signal (SSS) • Physical Broadcast Channel (PBCH) • Cell-specific Reference Signals (CSRS)

  33. Resource blocks • LTE defines the notion of a resource block which represents the minimal scheduling resource for both uplink and downlink transmissions • A physical resource block(PRB) corresponds to 180 kHz of spectrum

  34. Common PRB Formats • PRBs are mapped onto contiguous OFDMA/SC-FDMA symbols in the time-domain (6 or 7) • Each PRB is chosen to be equivalent to 12 (15 kHz spacing) sub-carriers of an OFDMA symbol in the frequency-domain • A 7.5kHz spacing version exists with 24 carriers per sub (insufficiently specified) • Because of a common PRB size over different channel bandwidths, the system scales naturally over different bandwidths • UEs determines cell bandwidth during initial acquisition and can be any of above

  35. OFDMA/SC-FDMA Mapping • OFDMA/SC-FDMA Sub-carriers are termed “Resource Elements” (RE) • DC carrier (DL) and high-frequencies are nulled • Spectral shaping and DC rejection for Zero-IF receivers • Half the bandwidth loss w.r.t. WCDMA (22%)

  36. Example: 300 REs, 25 RBs (5 MHz channel) PRB13 PRB24 “Normal” Cyclic Prefix Mode (7 symbols) PRB23 PRB22 PRB21 PRB20 PRB19 PRB18 PRB17 “Extended” Cyclic Prefix Mode (6 symbols) PRB16 PRB15 PRB14 PRB13 PRB12 PRB12 NRBDL/NRBUL PRB11 PRB10 PRB9 PRB8 PRB7 PRB6 PRB5 PRB4 NSCRB PRB3 PRB2 PRB1 PRB0 PRB11 l=0 l=6 NULsymb /NULsymb

  37. Sub-frame and Frame One frame = Tf =307200Ts= 10ms Tslot= 15360Ts=500ms 0 1 2 3 18 19 One subframe 71.3ms 71.9ms Normal Prefix 5.2ms 4.69ms Frequency Domain View 83ms Extended Prefix Time-domain View 13.9ms

  38. LTE UE Synchronization Procedures • Cell Search comprises • Timing and frequency synchronization with the cell using the primary synchronization reference signal. This also gives the Cell ID group NID(2) (0,1,2) • Cell ID NID(1) (0,…,167) and Frame type (FDD/TDD, Normal/Extended Prefix) determination from secondary synchronization reference signals • Demodulation of PBCH (using NIDCell=3NID(1) + NID(2)) to receive basic system information during steady-state reception • NRBDL (cell bandwidth) • PHICH-config (to allow PDCCH demodulation, for system information) • Frame number (8 bits from payload, 2 bits from redundancy version) • Antenna configuration (1,2,4 from CRC mask)

  39. Initial Timing/Frequency Acquisition (Synchronization Signals, FDD Normal CP) 10 ms Subframe 4 Subframe 1 Subframe 0 Subframe 5 Subframe 9 Frequency (PRBs) Time (symbols) Primary(Y) and Secondary(B) Synchronization Signals (2nd half) Primary (Y) and Secondary B) Synchronization Signals (first half) PBCH

  40. Primary Synchronization • Zadoff-Chu root-of-unity sequence has excellent auto-correlation properties and is very tolerant to frequency-offsets Autocorrelation sequence Real component (time-domain u=25) Imag component (time-domain, u=25)

  41. Primary Synchronization RX • Correlation of 3 primary sequences (d*u(-n)) with received signal. Each eNB (or sector) has different sequence => Reuse pattern of 3 for different eNB or sectors (NID(2)) Threshold d*u(-n) ()2 ↓M r(n) Received Frame Decimating correlator + non-coherent thresholding • Primary Purpose: Determine start of frame • Alternate purposes: Channel estimation for SSS/PBCH and frequency offset estimation • Implemented as Zadoff-Chu sequence of length 62 REs around DC (i.e. same resource block as PBCH, but only 62 out of 72 REs)

  42. Secondary Synchronization • Purpose: determine frame type and cell ID NID(1) • Implemented as BPSK-modulated interleaved sequence of two length-31 binary m-sequences (m=31) with cyclic shifts m0and m1. and scrambled by the two different scrambling sequences • Results in 167 possible BPSK sequences for each of subframe 0 and 5 • The receiver must perform correlations with all 167 sequences and find the most likely transmitted sequence. It can use the output of the primary sequence correlation as a rough channel estimate to improve detection probability • Position relative to PSS allows for frame type determination

  43. Secondary Synchronization RX • Hypothesis : one of 4 frame types TDD/FDD, normal/extended prefix => gives position in samples of SSS with respect to PSS detected in primary synchronization • Use channel estimate (partially coherent) from PSS and quantized uniform phase offset to compensate residual frequency offset (PSS/SSS not in same symbol) and amplitudes in SSS symbol • Correlate with 167 out of 167 * 3 sequences (167 per PSS NID(2)) of length 62 in each of slots 0 and 10 • Choose sequence which has highest coherent correlation • This has to be done with 2 different assumptions (subframe 0 or subframe 5 is first in RX buffer), or we just wait until we receive an RX frame in the correct order (i.e. when subframe 0 falls in the first 5 ms of the RX buffer)

  44. Secondary Synchronization RX H*0(k) D*sss,0,n(k) e2pjD/N D=-3,…,3, N=8 S Rsss,0(k), k=0,...,62 X X Re H*5(k) D*sss,5,n(k) X Rsss,5(k), k=0,...,62 X X H*0(k)=Dpss,0,u(k) Rpss,0*(k), k=0,...,62 H*5(k)=Dpss,5,n(k) Rpss,5*(k), k=0,...,62 PSS-based channel estimates

  45. Building the PSS/SSS Part First • OCTAVE files for PSS generation can be found here • $OPENAIR1_DIR/PHY/LTE_REFSIG/primary_synch.m • OCTAVE files for SSS generation can be found here • $OPENAIR1_DIR/USERSPACE_TOOLS/OCTAVE/CBMIMO1_TOOLS/sss_gen.m • Start an editor and create a file based on rx_spec.m, in the same directory so you have the OpenAir4G .oct files

  46. Steps • Correlate received signal with time-domain PSS sequence and square (use conv and abs) • Search for peaks (both) separated by 38400 samples (5 ms @ 7.68 Ms/s) • Do above SSS procedure according to 4 potential SSS positions (assume extended prefix and FDD) • FDD/Normal CP : SSS is (512+40) 552 samples before PSS • FDD/Extended CP: SSS is (512 + 128) 640 samples before PSS • TDD/Normal CP: SSS is (512+40+512+36+512+36) 1648 samples before PSS • TDD/Extended CP: SSS is (512+128+512+128+512+128) 1920 samples before PSS

  47. PBCH Detection • Detection of the PBCH requires the following steps • Generation of the cell-specific reference signals based on the cell ID derived from SSS detection • Performing channel estimation for the 4 symbols of the PBCH • Extracting the PBCH reference elements • Applying the conjugated channel estimates to the received reference elements • Channel decoding

  48. Cell-Specific Reference Signals p={0,1,2,3} p={0},p={0,1} p=0 p=0 p=0 p=1 p=1 (if active) p=1 (if active)

  49. Cell-Specific Reference Signals • Pseudo-random QPSK OFDM symbols • Based on generic LTE Gold sequence • Different sequence for different cell IDs • Different in each symbol of sub-frame • Different in each sub-frame, but periodic across frames (10ms) • Evenly spaced in subframe to allow for simple and efficient least-squares interpolation-based receivers • Between REs in frequency-domain • Across symbols in time-domain

  50. Channel Estimation in LTE (simple) • Recall that receiver sees • Must get channel estimate for channel compensation Estimation error PRB1 PRB0 Interpolation Extrapolation Interpolation Extrapolation NO pilots here

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