Se ha denunciado esta presentación.
Utilizamos tu perfil de LinkedIn y tus datos de actividad para personalizar los anuncios y mostrarte publicidad más relevante. Puedes cambiar tus preferencias de publicidad en cualquier momento.

Why Direct Transmission of 5G Radio over Optical Fiber?

An argument for replacing CPRI in mobile wireless fronthaul links with high performance analog optical transceivers that directly transmit high order modulation, spread spectrum OFDM radio signals over optical fiber and meet 3GPP E-UTRA specs. Replacing CPRI with an RF over Fiber link enables the consolidation of the radio and the virtualization of the remote radio head (RRH) within the baseband unit (BBU). In turn, this can reduce the network complexity, power consumption, CAPEX and OPEX while increasing bandwidth and improving bandwidth efficiency. If BBU processing time could be reduced to less than 2.3 ms, fronthaul reach could be extended up to 70 km.

Why Direct Transmission of 5G Radio over Optical Fiber?

  1. 1. 1© Copyright APIC Corporation 2017 A Business Case for Employing Direct RF Transmission over Optical Fiber In Place of CPRI for 4G and 5G Fronthaul Presented by APIC Corporation 5800 Uplander Way Culver City, CA 90230 www.APICHIP.com sales@apichip.com Revised 10/25/2017
  2. 2. 2© Copyright APIC Corporation 2017 Introduction  In the last 20 years mainstream opto-electronics was driven by 2 goals: – Increase transmission data rate based on 2 level modulation (recently PAM4 is being considered, 4 levels) – Reduce cost of transmitters  The above objectives were achieved at the expense of: – Optical links noise floor - Typical digital links operate at > 30dB above the electronics shot noise limit. – Linearity - In order to achieve lower cost modulation for two level states, linearity was not a priority, because it was compensated with limiting amplifiers.  In contrast, wireless transmissions have taken the approach to use the spectrum as efficiently as possible and apply high order modulation, lower data rates and densely spaced carriers. This requires low noise and high linearity from the link components.  Therefore, in order to carry wireless signals in fiber the options are: – High linearity, low noise optical components (APIC’s solution) – Convert to digital using oversampling, inefficient data rate payload, added latency and back conversion to RF as implemented by CPRI  Legacy optical components are not the optimal solution for future 5G
  3. 3. 3© Copyright APIC Corporation 2017 What is “Fronthaul?” Fronthaul: In a classic cell tower there is a base transceiver station (BTS) adjacent to the tower. The BTS is contained in an enclosure which requires significant power for radio amplifiers and environmental conditioning. To improve network efficiency the BTS has been split between the remote radio head (RRH) at the antenna and the baseband unit (BBU) which is located further away from the antenna. The RRH and the BBU communicate through a “fronthaul” link currently using Common Public Radio Interface (CPRI) or Open Base Station Architecture Initiative (OBSAI) standards. Backhaul Backhaul Fronthaul Remote Radio Head (RRH) Base Band Unit (BBU) Conventional Tower Evolution of DAS, 5G and Cloud RAN centralizes and virtualizes the BBU By Luděk Hrušák, CC BY-SA 3.0 BTS
  4. 4. 4© Copyright APIC Corporation 2017 The Fronthaul Link with CPRI 4 Conceptual explanation of REC/RE functional split1 1. Graphic is from Antonio de la Oliva, et. al., “An overview of the CPRI specification and its application to C-RAN based LTE scenarios,” IEEE Communications Magazine • February 2016 Very efficient spectrally efficient high bandwidth OFDM radio signals with high-order modulation are digitized with low-order modulation (QPSK) and serially streamed using CPRI between the BBU and RRH and then demodulated to reconstruct the original OFDM radio signal. Fronthaul link CPRI is a tradeoff to leverage existing telecom digital transceivers. CPRI processes and link BBU RRH
  5. 5. 5© Copyright APIC Corporation 2017 Fronthaul Link with Direct Transmission of 5G RF over Fiber 5 RFoFRFoF PA BBU RRH BBU Instead of digitizing the RF signal (as in CPRI or OBSAI) transport the RF signal in its native OFDM form via light through fiber – Direct Transmission of RF over Fiber (RFoF) RRH Proposed solution: direct transmission of high order modulated RF signals over fiber Shift to BBU all RRH processing including PA DPD – Virtualize the RRH Leave only passives and PAs
  6. 6. 6© Copyright APIC Corporation 2017 Issues with CPRI/Digitized RF for Fronthaul 6 • Bandwidth Efficiency: • High order modulation OFDM spread spectrum radio waveform vs CPRI encapsulated serial data • Channel data rate vs payload throughput • Bandwidth inefficiency impacts capacity and OPEX • Latency • Time required for CPRI processing vs processor speed • Impact of increased bandwidths on CPRI latency • Higher performance processors to improve latency impacts CAPEX • OPEX • Complexity of RRH and reliability in harsh environment increases CAPEX & OPEX • Power Consumption of CPRI processors • Life expectancy of CPRI Transceivers with 100% duty Cycle • CAPEX • Complexity & Cost of RRH with CPRI • Successive upgrades to match future bandwidth requirements
  7. 7. 7© Copyright APIC Corporation 2017 Complexity: CPRI vs. Directly Transmitted RF over Fiber 7 Conceptual explanation of REC/RE functional split1 with CPRI RFoF With RFoF, Radio is consolidated in the BBU; Less complicated; virtualized RRH RFoF PA Minimal electronics and power consumption at the antenna – just passive components and PAs BBU RRH BBU CPRI Solution RRH Solution: replace CPRI processors and algorithms with high-linearity link RRH
  8. 8. 8© Copyright APIC Corporation 2017 Latency: CPRI Processing vs. Directly Transmitted RF over Fiber 8 Solution: no time needed for CPRI processing; direct transmission of the RF signal 4G HARQ round trip time is 3 ms. 5G may tighten the round trip time specifications a) CPRI Processing in BBU c) CPRI Processing in RRH b) Signal Propagation in Fiber Total time = a + b + c a’ = 0 c’ = 0b’) Signal Propagation in Fiber BBU RRH Total time = b’ Time saved (a + c) can be reallocated to extend the reach of the link; 10 µs = 1 km Less Processing Time = Longer Fronthaul Reach* W/ CPRI RRH BBU • *If BBU processing budget could be reduced to less than 2.3 ms, a fronthaul reach up to 70 km is feasible • Longer fronthaul reach = greater consolidation of BBUs
  9. 9. 9© Copyright APIC Corporation 2017 CAPEX: CPRI vs. Directly Transmitted RF over Fiber 9 Example FPGAs: • Altera Stratix IV GX = $2,610 • Altera Stratix V = $5,700 • Altera Arria V1 = $1,6352 SFP Optical Transceiver ~ $150 APIC Optical Transceiver < $500 (ROM) CPRI digital sampling of high order modulation RF signals requires expensive processors such as FPGAs and DSPs Solution: Less than half the cost of CPRI link, interfaces and processors BBU RRH BBU • Consolidation of the radio and virtualization of the RRH in the BBU reduces the complexity and cost of the network electronics • RFoF physical link is decoupled from the waveform which makes it compatible with future waveforms – future proof Complex and expensive! CPRI Solution RRH
  10. 10. 10© Copyright APIC Corporation 2017 OPEX: CPRI vs. Directly Transmitted RF over Fiber 10 Solution: Consolidate of the radio and virtualize of the RRH in the BBU • More electronics and power required at the RRH for CPRI processing and signal conditioning • Transceivers operate at 100% duty cycle; impacts power consumption and lifespan • Greater complexity for reliability, diagnostics and repair • Need to future bandwidth upgrades BBU RRH BBU • Less electronics and power required at the antenna. • Transceivers only operate when RF signal is present; energy efficient • Simpler, more robust, easier to diagnose and repair • Same transceiver works with up to 2 GHz of aggregated adjacent signals Consolidation of the radio and virtualization of the RRH in the BBU conserves power and improves overall reliability and maintainability CPRI Solution RRH
  11. 11. 11© Copyright APIC Corporation 2017 APIC’s Technology Is a commercial application of high performance analog transceivers developed over a period of 10 years for the Department of Defense. • Ultra low noise lasers operate at shot noise levels, below -160 dB • Highly linear and responsive photo detectors, above 0.9 responsivity • Links have a high dynamic range, above 112 dBHz-2/3 • Links have a high IIP3 of 36 dBm y = 0.9879x - 19.975 y = 3.1478x - 97.437 -200 -150 -100 -50 0 50 100 -100 -50 0 50 100 OutputRFPower(dBm) RF Power (dBm) Fundamental IMD3 Linear (Fundamental) Linear (IMD3) IIP3 measurement for the RFoF link at 1 GHz. Similar results were measured at 3 GHz.Laser RIN (noise) of -170 dB measured from 0.5 to 20 GHz APIC 4 GHz Direct Mod transmitter developed for the US Navy, used for testing.
  12. 12. 12© Copyright APIC Corporation 2017 Network Implementation: Direct Transmission of OFDM Signals on RF-PON Consolidate the Baseband Units (BBUs) for multiple towers (macro-, micro-, pico-cell clusters) in centralized location – BBU “hotel” or “pool” • Improve network efficiency, timing and synchronization • Significantly lower CAPEX & OPEX costs • Reduce number and locations for maintenance calls • Prepare network for emerging 5G and Cloud-RAN deployments 12 RF-PON RF-PON based on ITU grid of 50 or 100GHz separation
  13. 13. 13© Copyright APIC Corporation 2017 Initial Testing Validates Directly Transmitted RF over Fiber Technology 25 km SMF-28 25 km SMF-28 20 km SMF-28DM Transmitter DC-5 GHz Photo Detector Anritsu MS2830A 6GHz Signal analyzer with: 6GHz Vector Signal Generator; bandwidth extension to 125MHz; software modules for LTE-Advanced IQ Producer; Vector Modulation Analysis; and LTE-Advanced FDD Downlink Measurement. • For all testing we use E-UTRA Downlink Test Model 3.1 (E-TM3.1) with 64QAM modulation, initially with a single 20 MHz carrier and then with 5 aggregated 20MHz carriers for 100MHz transmission bandwidth. • Performance metrics: • Total EVM (rms) ≤ 8% • ACP (ACLR) ≤ -44.2 dBm.
  14. 14. 14© Copyright APIC Corporation 2017 Test Summary: Single 20 MHz Channel  One 20 MHz, 64QAM OFDM signal transmitted over 25 km of fiber  3GPP LTE ACLR Spec: ≤ -44.2 dBm Full report is available at http://www.apichip.com/rfof-5-lte-advanced-carriers-70km/ • 3GPP LTE EVM Spec: ≤ 8% Measured ACLR is -45.81 dBc Measured EVM is 0.72%
  15. 15. 15© Copyright APIC Corporation 2017 Test Summary: Five aggregated 20 MHz Channels Full report is available at http://www.apichip.com/rfof-5-lte-advanced-carriers-70km/  5 x 20 MHz, 64QAM OFDM signals transmitted over 50 km of fiber  3GPP LTE ACLR Spec: ≤ -44.2 dBm • 3GPP LTE EVM Spec: ≤ 8% 5 Adjacent 20 MHz Channels Measured EVM is 2.58%
  16. 16. 16© Copyright APIC Corporation 2017 For More Information  Refer to the APIC website: www.apichip.com  Additional information on the direct transport of 4&5G Radio signals over fiber: http://www.apichip.com/5g-c-ran-fronthaul/  Follow APIC on LinkedIn:  For Business and sales contact Bob Walter directly at: walter@apichip.com  For technical questions contact Anguel Nikolov at: Nikolov@apichip.com

×