Coexistence with MIMO and Potential in Legacy LTE Systems Potential - PowerPoint PPT Presentation

Coexistence with MIMO and Potential in Legacy LTE Systems Potential in Legacy LTE Systems Mohammad A. (Amir) Khojastepour 1 , Ehsan Aryafar 2 , Karthik Sundaresan 1 , Rajesh Mahindra 1 , Sampath Rangarajan 1 1 NEC Laboratories America Princeton NJ 1 NEC Laboratories America, Princeton, NJ 2 Princeton University, Princeton, NJ

Background Background AP AP p 2 p 1 • Current wireless radios are half duplex C t i l di h lf d l Amir Khojastepour NEC Laboratories America

Background Background AP AP p 2 p 1 • Current wireless radios are half duplex C t i l di h lf d l • Same band Full duplex is hard – Self interference is very high: ≈ 75 dB for 15 dBm Tx power Self interference is very high 75 dB for 15 dBm Tx power – Transmitted signal is known  self interference cancellation – Self interference can be significantly reduced by adding a g y y g cancellation circuit: e.g., a cancelling antenna Amir Khojastepour NEC Laboratories America

Background Background AP AP p 2 p 1 • Current wireless radios are half duplex C t i l di h lf d l • Same band Full duplex is hard – Self interference is very high: ≈ 75 dB for 15 dBm Tx power Self interference is very high 75 dB for 15 dBm Tx power – Self interference can be significantly cancelled by adding a cancellation circuit: e.g., a cancelling antenna Can full duplex wireless double the capacity? Amir Khojastepour NEC Laboratories America

Outline Outline • Background • Related works • Design of MIDU • Experimental Evaluation • Real world implementation • Legacy ‐ LTE Basestation • Half duplex clients • Conclusion Amir Khojastepour NEC Laboratories America

Related Work Related Work • Single ‐ antenna full duplex Single antenna full duplex – M. Knox, “Self ‐ jamming for full duplex” Enhanced Circulator design for full duplex wireless Enhanced Circulator design for full duplex wireless Tx Signal Tx Signal Tx Output Tx Output Rx Input Rx Inp t Interference Interference + Cancellation Circuit Cancellation Circuit Cancellation Circuit Cancellation Circuit Rx Signal Amir Khojastepour NEC Laboratories America

Related Work Related Work • Single ‐ antenna full duplex Single antenna full duplex – M. Knox, “Self ‐ jamming for full duplex” • Antenna Cancellation • Antenna Cancellation – A. Khandani, “Two ‐ way (true full duplex) wireless” • Asymmetric Antenna cancellation • Asymmetric Antenna cancellation – J. Choi, et. al., “Achieving single channel full duplex” • Analogue cancellation A l ll ti – M. Jain, et. al., “Practical full duplex” – M. Durate, et. al., Full duplex with off ‐ the ‐ shelf radios M Durate et al “Full duplex with off the shelf radios" Amir Khojastepour NEC Laboratories America

Full Duplex vs. MIMO Full Duplex vs. MIMO • Hardware complexity, performance, size, cost metrics Amir Khojastepour NEC Laboratories America

Full Duplex vs. MIMO Full Duplex vs. MIMO • Hardware complexity, performance, size, cost metrics • • Antenna Conserved (AC): Same Antenna Conserved (AC): Same # antennas Amir Khojastepour NEC Laboratories America

Full Duplex vs. MIMO Full Duplex vs. MIMO • Hardware complexity, performance, size, cost metrics • • Antenna Conserved (AC): Same Antenna Conserved (AC): Same # antennas • RF ‐ Chain Conserved (RC): Same # chains Amir Khojastepour NEC Laboratories America

Full Duplex vs. MIMO Full Duplex vs. MIMO • Hardware complexity, SI loss: 6 dB Ant Correlation: 0.1 performance, size, cost metrics  = 0.01  0.01 • • Antenna Conserved (AC): Same Antenna Conserved (AC): Same 100 FD-RC # antennas HD el use) 80 • FD-AC RF ‐ Chain Conserved (RC): Same # chains ity (bit/chann 60 40 • Significant FD gains in RC model Significant FD gains in RC model Capaci • Limited FD gains with small # 20 antennas in AC model higher 0 0 0 5 5 10 10 15 15 20 20 gains with more antennas gains with more antennas Number of Antennas Amir Khojastepour NEC Laboratories America

Full Duplex vs. MIMO Full Duplex vs. MIMO • Hardware complexity, SI loss: 6 dB Ant Correlation: 0.1 performance, size, cost metrics   = 0.01 0.01 • • Antenna Conserved (AC): Same Antenna Conserved (AC): Same 100 FD-RC # antennas Regions of pronounced full duplex gains in HD el use) 80 • FD-AC RF ‐ Chain Conserved (RC): Same both RC and AC models b th RC d AC m d ls # chains ity (bit/chann 60 40 • Significant FD gains in RC model Significant FD gains in RC model Capaci • Limited FD gains with small # 20 antennas in AC model higher 0 0 0 5 5 10 10 15 15 20 20 gains with more antennas gains with more antennas Number of Antennas Amir Khojastepour NEC Laboratories America

MIDU: MImo full DUplex MIDU: MImo full ‐ DUplex • Symmetric antenna R1 T1 T'1 1 1 1 placement d d d d π Input Signal Input Signal Amir Khojastepour NEC Laboratories America

MIDU: MImo full ‐ DUplex MIDU: MImo full DUplex • Symmetric antenna RX Chain placement R1 • 2 level of antenna • 2 ‐ level of antenna cancellation T'1 T1 – Tx cancellation followed by π Rx cancellation Rx cancellation – Proved in theory to have additive gains under R'1 imbalanced gains/phase or imbalanced gains/phase or imprecise placement π TX Chain Amir Khojastepour

MIDU: MImo full ‐ DUplex MIDU: MImo full DUplex • Symmetric antenna placement R3 R2 • 2 level of antenna • 2 ‐ level of antenna R1 cancellation – Tx cancellation followed by Rx cancellation Rx cancellation – Proved in theory to have T'1 T'2 T'3 T1 T2 T3 additive gains under imbalanced gains/phase or imbalanced gains/phase or R'1 imprecise placement R'2 • Easy scalability to MIMO l b l R'3 Amir Khojastepour NEC Laboratories America

Experimental Evaluations Experimental Evaluations • WarpLab implementation – Narrow ‐ band 625 KHz – Open space environment – MIDU vs MU ‐ MIMO MIDU vs. MU MIMO Virtex ‐ IV Pro FPGA Amir Khojastepour NEC Laboratories America

Experimental Evaluations Experimental Evaluations • WarpLab implementation – Narrow ‐ band 625 KHz – Open space environment – MIDU vs MU ‐ MIMO MIDU vs. MU MIMO • Performance metric: SNR and the corresponding Shannon capacity di Sh i Virtex ‐ IV Pro FPGA Amir Khojastepour NEC Laboratories America

Experimental Evaluations Experimental Evaluations • WarpLab implementation – Narrow ‐ band 625 KHz – Open space environment – MIDU + MU ‐ MIMO MIDU + MU MIMO • Performance metric: SNR and the corresponding Shannon capacity di Sh i Virtex ‐ IV Pro FPGA • Spectrum analyzer based • Spectrum analyzer based measurement or the SNR reported by WARP Amir Khojastepour NEC Laboratories America

Experimental Evaluations Experimental Evaluations • Feasibility – Channel–distance relationship R3 – Stability R2 – Impact on far ‐ field users Impact on far field users R1 • Cancellation – Single ‐ level T'1 T'2 T'3 T1 T2 T3 – 2 ‐ level and MIMO • Comparison with MIMO R'1 – Single link R'2 – Single cell Single cell R'3 Amir Khojastepour NEC Laboratories America

Impact of MIDU on Far ‐ Field Users ld • Issue: How does symmetric y antenna placement impact the far ‐ field users? Amir Khojastepour

Impact of MIDU on Far ‐ Field Users ld 13 14 • Issue: How does symmetric y antenna placement impact the far ‐ field users? 12 15 3 4 2 5 16 11 TX 6 1 7 10 8 9 17 20 20 <3m> 19 18 Amir Khojastepour

Impact of MIDU on Far ‐ Field Users ld • Issue: How does symmetric y antenna placement impact the far ‐ field users? • Achieved SNR can be up to 4 dB higher/lower Outer Circle Inner Circle Amir Khojastepour

Impact of MIDU on Far ‐ Field Users ld • Issue: How does symmetric y antenna placement impact the far ‐ field users? • Achieved SNR can be up to 4 dB higher/lower • In far ‐ field antenna I f fi ld t cancellation has very limited effect due to signal scattering (fading) g ( g) • Similar results hold for RX cancellation Outer Circle Inner Circle Amir Khojastepour

Experimental Evaluations Experimental Evaluations • Feasibility – Channel–distance relationship R3 – Stability R2 – Impact on far ‐ field users Impact on far field users R1 • Cancellation – Single ‐ level T'1 T'2 T'3 T1 T2 T3 – 2 ‐ level and MIMO • Comparison with MIMO R'1 – Single link R'2 – Single cell Single cell R'3 Amir Khojastepour NEC Laboratories America

Cancellation Cancellation R1 T1 • T'1 Issue: Is 2 ‐ level cancellation 1 1 1 additive? Is MIDU scalable? • • Connect the receiver to a Connect the receiver to a d d d d spectrum analyzer π Input Signal Input Signal Amir Khojastepour NEC Laboratories America

Cancellation Cancellation • Issue: Is 2 ‐ level cancellation additive? Is MIDU scalable? • • 22 22 – 30 dB cancellation on each 30 dB cancellation on each level separately • Cancellation remains relatively unchanged with Tx power Amir Khojastepour NEC Laboratories America

Cancellation Cancellation RX Chain • Issue: Is 2 ‐ level cancellation additive? Is MIDU scalable? R1 Θ • • Phase shifter on each path to Phase shifter on each path to Θ + π T'1 T1 handle insertion loss and delay R'1 Θ Θ + π TX Chain Amir Khojastepour NEC Laboratories America