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

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

Oct 17, 2023 180 likes •639 views

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

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SLIDE 1

Coexistence with MIMO and Potential in Legacy LTE Systems Potential in Legacy LTE Systems

Mohammad A. (Amir) Khojastepour1, Ehsan Aryafar2, Karthik Sundaresan1, Rajesh Mahindra1, Sampath Rangarajan1

1NEC Laboratories America Princeton NJ 1NEC Laboratories America, Princeton, NJ 2Princeton University, Princeton, NJ

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SLIDE 2

Background Background

AP C t i l di h lf d l

p1 p2

AP

  • Current wireless radios are half duplex

Amir Khojastepour NEC Laboratories America

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SLIDE 3

Background Background

AP C t i l di h lf d l

p1 p2

AP

  • Current wireless radios are half duplex
  • 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

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SLIDE 4

Background Background

AP C t i l di h lf d l

p1 p2

AP

  • Current wireless radios are half duplex
  • 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

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SLIDE 5

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

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SLIDE 6

Related Work Related Work

  • Single‐antenna full duplex

Single antenna full duplex

– M. Knox, “Self‐jamming for full duplex” Tx Signal Tx Output Enhanced Circulator design for full duplex wireless Enhanced Circulator design for full duplex wireless Tx Signal Tx Output Rx Inp t Interference Cancellation Circuit Interference Cancellation Circuit Rx Input

+

Amir Khojastepour NEC Laboratories America

Cancellation Circuit Cancellation Circuit Rx Signal

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SLIDE 7

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”

A l ll ti

  • Analogue cancellation

– 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

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SLIDE 8

Full Duplex vs. MIMO Full Duplex vs. MIMO

  • Hardware complexity,

performance, size, cost metrics

Amir Khojastepour NEC Laboratories America

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SLIDE 9

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

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SLIDE 10

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

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SLIDE 11

Full Duplex vs. MIMO Full Duplex vs. MIMO

  • Hardware complexity,

SI loss: 6 dB Ant Correlation: 0.1 performance, size, cost metrics

  • Antenna Conserved (AC): Same

 = 0.01

  • Antenna Conserved (AC): Same

# antennas

  • RF‐Chain Conserved (RC): Same

80 100 el use)

0.01 FD-RC HD FD-AC

# chains

  • Significant FD gains in RC model

40 60 ity (bit/chann

Significant FD gains in RC model

  • Limited FD gains with small #

antennas in AC model higher gains with more antennas

5 10 15 20 20 Capaci

gains with more antennas

Amir Khojastepour NEC Laboratories America

5 10 15 20 Number of Antennas

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SLIDE 12

Full Duplex vs. MIMO Full Duplex vs. MIMO

  • Hardware complexity,

SI loss: 6 dB Ant Correlation: 0.1 performance, size, cost metrics

  • Antenna Conserved (AC): Same

 = 0.01

  • Antenna Conserved (AC): Same

# antennas

  • RF‐Chain Conserved (RC): Same

80 100 el use)

0.01 FD-RC HD FD-AC

Regions of pronounced full duplex gains in b th RC d AC m d ls

# chains

  • Significant FD gains in RC model

40 60 ity (bit/chann

both RC and AC models

Significant FD gains in RC model

  • Limited FD gains with small #

antennas in AC model higher gains with more antennas

5 10 15 20 20 Capaci

gains with more antennas

Amir Khojastepour NEC Laboratories America

5 10 15 20 Number of Antennas

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SLIDE 13

MIDU: MImo full‐DUplex MIDU: MImo full DUplex

  • Symmetric antenna

T1 R1 T'1

placement

1 1 1

d d d d π

Input Signal Input Signal

Amir Khojastepour NEC Laboratories America

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SLIDE 14

MIDU: MImo full‐DUplex MIDU: MImo full DUplex

  • Symmetric antenna

RX Chain

placement

  • 2 level of antenna

R1

  • 2‐level of antenna

cancellation

– Tx cancellation followed by Rx cancellation

T1 T'1

π

Rx cancellation – Proved in theory to have additive gains under imbalanced gains/phase or

R'1

imbalanced gains/phase or imprecise placement

π

Amir Khojastepour

TX Chain

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SLIDE 15

MIDU: MImo full‐DUplex MIDU: MImo full DUplex

  • Symmetric antenna

placement

  • 2 level of antenna

R2 R3

  • 2‐level of antenna

cancellation

– Tx cancellation followed by Rx cancellation

R1

Rx cancellation – Proved in theory to have additive gains under imbalanced gains/phase or

T1 T2 T3 T'1 T'2 T'3

imbalanced gains/phase or imprecise placement

l b l

R'1 R'2

  • Easy scalability to MIMO

Amir Khojastepour NEC Laboratories America

R'3

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SLIDE 16

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

NEC Laboratories America Amir Khojastepour

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SLIDE 17

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

di Sh i corresponding Shannon capacity

Virtex‐IV Pro FPGA

NEC Laboratories America Amir Khojastepour

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SLIDE 18

Experimental Evaluations Experimental Evaluations

  • WarpLab implementation

– Narrow‐band 625 KHz – Open space environment – MIDU + MU‐MIMO MIDU + MU MIMO

  • Performance metric: SNR and the

di Sh i corresponding Shannon capacity

  • Spectrum analyzer based

Virtex‐IV Pro FPGA

  • Spectrum analyzer based

measurement or the SNR reported by WARP

NEC Laboratories America Amir Khojastepour

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SLIDE 19

Experimental Evaluations Experimental Evaluations

  • Feasibility

– Channel–distance relationship – Stability – Impact on far‐field users

R2 R3

Impact on far field users

  • Cancellation

R1

– Single‐level – 2‐level and MIMO

T1 T2 T3 T'1 T'2 T'3

  • Comparison with MIMO

– Single link Single cell

R'1 R'2

– Single cell

Amir Khojastepour NEC Laboratories America

R'3

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SLIDE 20

Impact of MIDU on ld Far‐Field Users

  • Issue: How does symmetric

y antenna placement impact the far‐field users?

Amir Khojastepour

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SLIDE 21

Impact of MIDU on ld Far‐Field Users

  • Issue: How does symmetric

14 13

y antenna placement impact the far‐field users?

3 4 15 12

TX

1 2 5 6 16 11 9 10 7 8 20 17

<3m>

20 19 18

Amir Khojastepour

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SLIDE 22

Impact of MIDU on ld Far‐Field Users

  • Issue: How does symmetric

y antenna placement impact the far‐field users?

  • Achieved SNR can be up to 4

dB higher/lower

Amir Khojastepour

Inner Circle Outer Circle

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SLIDE 23

Impact of MIDU on ld Far‐Field Users

  • Issue: How does symmetric

y antenna placement impact the far‐field users?

  • Achieved SNR can be up to 4

dB higher/lower I f fi ld t

  • In far‐field antenna

cancellation has very limited effect due to signal scattering (fading) g ( g)

  • Similar results hold for RX

cancellation

Amir Khojastepour

Inner Circle Outer Circle

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SLIDE 24

Experimental Evaluations Experimental Evaluations

  • Feasibility

– Channel–distance relationship – Stability – Impact on far‐field users

R2 R3

Impact on far field users

  • Cancellation

R1

– Single‐level – 2‐level and MIMO

T1 T2 T3 T'1 T'2 T'3

  • Comparison with MIMO

– Single link Single cell

R'1 R'2

– Single cell

Amir Khojastepour NEC Laboratories America

R'3

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SLIDE 25

Cancellation Cancellation

  • Issue: Is 2‐level cancellation

T1 R1 T'1

additive? Is MIDU scalable?

  • Connect the receiver to a

1 1 1

d d

  • Connect the receiver to a

spectrum analyzer d d π

Input Signal Input Signal

Amir Khojastepour NEC Laboratories America

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SLIDE 26

Cancellation Cancellation

  • Issue: Is 2‐level cancellation

additive? Is MIDU scalable?

  • 22

30 dB cancellation on each

  • 22 – 30 dB cancellation on each

level separately

  • Cancellation remains relatively

unchanged with Tx power

Amir Khojastepour NEC Laboratories America

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SLIDE 27

Cancellation Cancellation

  • Issue: Is 2‐level cancellation

RX Chain

additive? Is MIDU scalable?

  • Phase shifter on each path to

R1

Θ

  • Phase shifter on each path to

handle insertion loss and delay

T1 T'1

Θ+π

R'1 TX Chain

Θ+π Θ

Amir Khojastepour NEC Laboratories America

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SLIDE 28

Cancellation Cancellation

  • Issue: Is 2‐level cancellation

additive? Is MIDU scalable?

  • Phase shifter on each path to
  • Phase shifter on each path to

handle insertion loss and delay

  • RX cancellation on top of TX

cancellation is additive

Amir Khojastepour NEC Laboratories America

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SLIDE 29

Cancellation Cancellation

  • Issue: Is 2‐level cancellation

additive? Is MIDU scalable?

  • Phase shifter on each path to
  • Phase shifter on each path to

handle insertion loss and delay

  • RX cancellation on top of TX

cancellation is additive

  • 4 dB decrease in cancellation

for the first added pair, 5 dB with 3 total pairs with 3 total pairs

Amir Khojastepour NEC Laboratories America

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SLIDE 30

Experimental Evaluations Experimental Evaluations

  • Feasibility

– Channel–distance relationship – Stability – Impact on far‐field users

R2 R3

Impact on far field users

  • Cancellation

R1

– Single‐level – 2‐level and MIMO

T1 T2 T3 T'1 T'2 T'3

  • Comparison with MIMO

– Single link Single cell

R'1 R'2

– Single cell

Amir Khojastepour NEC Laboratories America

R'3

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SLIDE 31

Comparison with MIMO Comparison with MIMO

  • Compare MIDU to MU‐MIMO

R

– RF‐Chain conserved model – Multi‐user beamfoming/filtering for MU‐MIMO in each direction UL  DL interference in MIDU

R1 R2 MIDU BS

– UL  DL interference in MIDU

  • Metric: Shannon capacity of the

measured SNR

R5 R6

measured SNR

R3 R4

2m Amir Khojastepour NEC Laboratories America

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SLIDE 32

Comparison with MIMO Comparison with MIMO

  • Compare MIDU to MU‐MIMO

M: #UL Streams N: #DL Streams – RF‐Chain conserved model – Multi‐user beamfoming/filtering for MU‐MIMO in each direction UL  DL interference in MIDU – UL  DL interference in MIDU

  • Full duplex gains diminish as

the number of streams is scaled the number of streams is scaled

Amir Khojastepour NEC Laboratories America

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SLIDE 33

Comparison with MIMO Comparison with MIMO

  • Compare MIDU to MU‐MIMO

3 DL Streams Var UL Streams – RF‐Chain conserved model – Multi‐user beamfoming/filtering for MU‐MIMO in each direction UL  DL interference in MIDU – UL  DL interference in MIDU

  • Full duplex gains diminish as

the number of streams is scaled the number of streams is scaled

  • For maximum full duplex gains,

the number of streams the number of streams between UL and DL should be dis‐proportionate

Amir Khojastepour NEC Laboratories America

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SLIDE 34

Comparison with MIMO Comparison with MIMO

  • Compare MIDU to MU‐MIMO

3 DL Streams Var UL Streams – RF‐Chain conserved model – Multi‐user beamfoming/filtering for MU‐MIMO in each direction UL  DL interference in MIDU – UL  DL interference in MIDU

  • Full duplex gains diminish as

the number of streams is scaled

Full duplex has great potential in practical single cell MU-MIMO schemes in which the

the number of streams is scaled

  • For maximum full duplex gains,

the number of streams

s ng c M M MO sch m s n wh ch th number of UL streams is small

the number of streams between UL and DL should be dis‐proportionate

Amir Khojastepour NEC Laboratories America

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SLIDE 35

FD for Legacy‐LTE FD for Legacy LTE

  • Is it possible to enable FD in legacy LTE

Is it possible to enable FD in legacy LTE systems?

– What changes are required? – What changes are required?

  • Handset sides and network (base‐station) side

– New hardware? New hardware? – New firmware? Change in standard? – Change in standard?

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SLIDE 36

Challenges Challenges

  • SI cancellation

SI cancellation

– Is analog cancellation sufficient? – What range/data rate could be achieved? What range/data rate could be achieved? – Passive cancellation or need for Active cancellation?

  • Integration with legacy BS equipment

Integration with legacy BS equipment

– Can we keep the BS hardware and/or firmware unchanged? g – Handling multiple frequency bands

  • Transparency to half‐duplex client

a spa e cy to a dup e c e t

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SLIDE 37

Frequency Converter Circuit Frequency Converter Circuit

  • We use the

f ll i i it t following circuit to enable FD without modifying basestation, user , equipment or standards

  • A circuit has to be

used in the basestation as well as a as a complementary circuit at the user equipment

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SLIDE 38

Full Duplex LTE Testbed Full Duplex LTE Testbed

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SLIDE 39

SI Cancellation at BS SI Cancellation at BS

  • SI power without any

p y cancellation ‐42dBm

  • SI after antenna

cancellation ‐64dBm

  • SI after antenna

cancellation and using g antenna shielding ‐ 73dBm

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SLIDE 40

Indoor SI Cancellation Evaluation Indoor SI Cancellation Evaluation

  • AO: antenna separation only
  • AC: antenna cancellation
  • AS: antenna cancellation plus

antenna shielding

  • AP: antenna cancellation plus

polarization ASP ll i

  • ASP: antenna cancellation

plus polarization plus shielding

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SLIDE 41

Outdoor SI Cancellation Evaluation

  • AO: antenna separation only
  • AC: antenna cancellation only
  • AS: antenna cancellation plus

antenna shielding

  • AP: antenna cancellation plus

polarization ASP ll i l

  • ASP: antenna cancellation plus

polarization plus shielding

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SLIDE 42

Experiment Layout Experiment Layout

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SLIDE 43

UDP Throughput UDP Throughput

  • DL FD outperforms

DL FD outperforms DL HD for almost all locations

  • UL FD outperforms

UL FD outperforms UL HD for about 60% locations with an average gain of 23%

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SLIDE 44

CDF of Total FD (UL+DL) to Total HD h h Throughput

  • In about 65% of

In about 65% of the locations FD has gain over HD has gain over HD I b 40% f

  • In about 40% of

the locations the i i b gain is between 20%‐40%

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SLIDE 45

In Summary In Summary

  • Designed and implemented MIDU, the first MIMO full

duplex wireless system

  • Enabled two stages of antenna cancellation with
  • Enabled two stages of antenna cancellation with

additive gains that provided as high as 45 dB self‐ interference cancellation

  • Built a prototype of MIDU with joint operation of 3x3

MIMO + Full Duplex in practice p p

  • Implementation using Legacy‐LTE basestation and

possibility to use half duplex clients possibility to use half‐duplex clients

Amir Khojastepour NEC Laboratories America