SDR-BASED TEST BENCH TO EVALUATE ANALOG CANCELLATION TECHNIQUES FOR IN-BAND FULL-DUPLEX TRANSCEIVER

Transcription

1 SDR-BASED TEST BENCH TO EVALUATE ANALOG CANCELLATION TECHNIQUES FOR IN-BAND FULL-DUPLEX TRANSCEIVER Patrick Rosson, David Dassonville, Xavier Popon, Sylvie Mayrargue CEA-Leti Minatec Campus Cleen Workshop, Torino, June 22 nd 2017

2 OUTLINE Introduction to In-Band Full-Duplex Architecture SDR Test bench Results SDR transceiver evaluation for In-Band Full-Duplex Analog cancellation performance Conclusion 2

3 Frequency Frequency Frequency INTRODUCTION TO IN-BAND FULL-DUPLEX (1/3) Current cellular standards Access mode : Frequency Division Duplex (FDD) / Time Division Duplex (TDD) Capacity improvements : MIMO solution and/or relaying techniques In-Band Full-Duplex (IBFD) Transmitting and receiving at the same time on the same frequency band FDD TDD IBFD DL UL D L U L UL DL Time Time Time Advantages: Potential capacity gain, relax TDD latency and FDD frequency constraint Drawbacks: Self-interference and extra-interference 3

4 INTRODUCTION TO IN-BAND FULL-DUPLEX (2/3) General scenarios showing potential interest of IBFD In-Band Full-Duplex link In-Band Full-Duplex transceiver Extra-interferences Backhaul Self-Backhaul Macro Cell <-> Small Cells Basic requirements for IBFD Data traffic IBFD requires 2 way data flows Channel properties IBFD requires low path loss IBFD? Transceiver Self-Interference cancellation capability from 60 db to 100 db or more 4

5 INTRODUCTION TO IN-BAND FULL-DUPLEX (3/3) Major Challenge Self-interference cancellation Pioneering works on cancellation solutions Rice solution (2011) Hybrid active (digital-rf) canceller Digital canceller Stanford solution (2013) Digitally controlled RF canceller Digital canceller Note: the two antennas can be replaced by one antenna with a circulator Analog cancellers are mandatory to avoid ADC saturation This paper focuses on analog cancelation techniques 5

6 ARCHITECTURE Architecture adapted to analog cancellation RFSIC It cancels the strong part of the SI (narrow band filter) Slow adaptation process based on received power HSIC It cancels the remaining part of the SI (linear broadband filter) Mid-speed adaptation process based on channel estimation outputs Transmit signal Tx1 RFSIC CTRL HSIC Linear filter x 1 Cmd 1 & 2 x 2 DAC Slow Slow DAC DAC 1 2 DAC Main Tx RF chain V1 & V2 Auxiliary Tx RF chain y t RFSIC Coupler Tx 10 db Coupler SIC Tx Circulator & antenna emulator Receiver Rx1 y d ADC Main Rx RF chain y r Coupler Rx 10 db Rx Note: RFSIC and HSIC can be complemented with a DSIC (after the DAC) 6

7 TEST BENCH (1/3) Test bench overview IP frame over USB Digital Board Zynq (dual core ARM + Programmable Logic) Linux OS / AD9361 Driver RFSIC Ctrl RFSIC Front-end Ctrl Digital IQ Tx Rx Tx0 Rx0 DC Voltages I/Q PA Tx RMS power up to 20 dbm Antenna emulator with circulator HSIC Tx1 SDR RF transceiver Board Based on with AD9361 RFSIC Board Note Band-pass filters are not represented Spectrum analyser 7

8 TEST BENCH (2/3) Circulator with antenna emulator Objective Fixed set of S parameters to debug analog part Characteristic Controlled reflection Non flat frequency response Adapted for 900 MHz Port C Custom RFSIC board 2 x Couplers 10 db To pick up a image of the Tx signal To mitigate the self-interference Fixed delay RF vector modulator Digitally controlled Port C Port A Port C Limitations Adapted for the 900 MHz BW Non-linearity Noise 8

9 TEST BENCH OVERVIEW (3/3) SDR RF transceiver board Based on AD9361 chip DAC/ADC 12 bits Fs MHz RF BW 56 MHz 70 MHz to 6 GHz 900 MHz selected for the test Custom digital board Based on Zynq ARM processor Programmable Logic Dual DAC RFSIC Control Both boards need to be synchronised (time/frequency) Digital converters Up/down frequency conversion 9

10 RESULTS (1/2) SDR RF transceiver evaluation for In-Band Full-Duplex Txi/Rx0 isolation Isolation (db) Between Tx0 and Rx0-70 Between Tx1 and Rx0-92 Different output powers WGN 40MHz Transmitter linearity Near principal spectrum Transmission noise NL Transmitter linearity with or w/o external PA Far principal spectrum with PA w/o PA Main conclusions Chip isolation can be increased using external PA Additional pass-band filters are mandatory (to avoid aliasing phenomena) Tradeoff between linear versus nonlinear Tx power components 10

11 RESULTS (2/2) Self-Interference cancellation performance without presence of received signal After the PA After the circulator After the RFSIC After the HSIC Power (dbm) Cancellation (db) Transmitted power after the PA 12 Leaked power after the circulator After the RFSIC After the HSIC Total Cancellation 71 11

12 CONCLUSION AND PERSPECTIVE SDR RF transceiver based on AD9361 has been characterized for In- Band Full-Duplex scenario SDR Test bench with antenna isolation emulation shows around 71 db analog cancellation over 40 MHz at 900 MHz on real signal Test bench will evolve to support 3.5 GHz frequency band RFSIC will be redesigned to address 3.5 GHz frequency band and generate less noise HSIC will evolve to have fast tracking capability 12

13 Thank you for attending CLEEN Patrick ROSSON June 22 nd 2017 Leti, technology research institute Commissariat à l énergie atomique et aux énergies alternatives Minatec Campus 17 rue des Martyrs Grenoble Cedex France

14 SCENARIOS «Point to point» scenario IBFD Channel Reciprocity if same antenna Tx et RX Rx1, Rx2 equal? Tx1, Tx2 equal? SNR1 et SNR2 equal if same antenna, same Tx power and same NF Self-interference In-Band Full-Duplex Transceiver Point to point Link Full-Duplex Signal A 1 2 Signal B Self-interference Advanced scenario Additional external interferences SINR1 SINR 2 different Self-interference In-Band Full-Duplex Transceiver Point to point Link Full-Duplex Signal A 1 2 Signal B Interferences Self-interference Interferences 14

15 Multipath or Interference Multipath or Interference SCENARIOS «Point to multipoint» scenario Classic 2 possible cases Signal A and signal B with same information Signal A et signal B with different information In-Band Full-Duplex Transceiver Advanced Additional external interferences In-Band Full-Duplex Transceiver 1 3 Interferences 15