Experimental Evaluation of a Novel Fast Beamsteering Algorithm for Link Re-Establishment in mm-Wave Indoor WLANs

Experimental Evaluation of aNovel Fast Beamsteering Algorithm for

Link Re-Establishment in mm-Wave Indoor WLANsAvishek Patra, Ljiljana Simić and Marina Petrova

Institute for Networked Systems, RWTH Aachen University, Aachen, Germany

OUTLINE

INTRODUCTION TO MM-WAVE NETWORKS

BEAMSTEERING PROBLEM

FAST BEAMSTEERING ALGORITHM

EXPERIMENTAL EVALUATION METHODOLOGY

PERFORMANCE RESULTS & ANALYSIS

CONCLUSIONS & FUTURE WORKS

INTRODUCTION TO MM-WAVE NETWORKS

• mm-wave bands for multi-Gbps connectivityFILLER

• Challenge: high attenuation!FILLER

• Solution: directional antennas ⇒increase rangeFILLER

• Further challenges:

1) directional link formation ⇒ only if TX & RX antennas steered to feasible directions

2) link disruptions due to antenna misalignments, link interruption, mobility, . . .

1

FILLER

• State of the Art:

exhaustive sequential scanning of Tx & Rx antenna sectors

⇒ e.g. exhaustive scanning-like algorithm in IEEE 802.11 ad

⇒ high latency, QoS degradation

FILLER•Motivation:

low latency, fast beamsteering to re-establish linksessential for seamless connectivity and maintaining QoS

FILLER 2

CONTD.INTRODUCTION TO MM-WAVE NETWORKS

FILLER• Solutions in literature:

• dependent on:

• focus only on static networksFILLER• Untackled problem:

• UE mobility ⇒ induces frequent link disruptionsFILLER

3


- additional hardware,- secondary link knowledge,- environmental information . . .

• Our work: FILLER

• we propose a generic, fast beamsteering algorithm that:- doesn’t depend on extra hardware or information,- addresses UE mobility-induced disruption,- uses available last valid link information only!

FILLER

• performance evaluation in real indoor environment using 60 GHz packet radio transceiver

4


user equipment

(UE)

S4

S3S2S1

S I

S i...

S4

S j

S2 S3S1

...

i

jAPΘ = 360°

I

UEΘ = 360°J

Θ

...

access point (AP) AP

Pair 1 = {S , S }3 1AP, f UE, f

Feasible sector

Pair 2 = {S , S }4 2AP, f UE, f

Feasible sector

S J...ΘUE

AP

AP

AP AP

AP

AP

UE

UE

UE

UE

UE

UE

access point (AP)

user equipment

(UE)

• if RSS > RX Sensitivity Threshold for AP-UE sector:

FILLER ⇒ link established

FILLER ⇒ feasible sector pair

FILLERe.g.

FILLER• multiple feasible sector pairs

for a AP-UE location

5

BEAM STEERING PROBLEM

LOS Link NLOS Link

3 1 4 2{S ,S } & {S ,S }AP UE AP UE

BEAM STEERING PROBLEM

• re-establishing link ⇒ search until feasible sector pair foundFILLER

FILLER

FILLER

• for exhaustive sequential scanning

⇒ # sector pairs searched = total # sector pairs

• finds optimal sector pair . . . but high latency

• latency increases with antenna directionality increase

6

CONTD.

re-establishment latency ∝ # of sector pairs

searched


• Algorithm idea: “…initiate search in vicinity of the previously valid (i.e., before disruption) sector pair…”

FILLER

→ start search from the previous feasible sector pair

→ increase search space till new feasible sector pair found

→ AP-UE coordination? Before start, sort all sector pairs such that sector pairs nearest to previous feasible sector pair checked first

→ stop as soon as a new feasible sector pair foundFILLER

7

[1]

[1] – Patra et al. “Smart mm-Wave Beam Steering Algorithm for Fast Link Re-Establishment under Node Mobility in 60 GHz Indoor WLANs”

8

CONTD.

access point(AP)

user equipment (UE)

p1

p7p6p5

p3p4

p2

p8

q5q4

q2

q7 q6q8q1

q3

UE mobility causes link disruption

p1p8

p7p6p5

p3

q5q4

q2

q7 q6q8

p4p2

q1q3

p1p8

p7p6p5

p3

q5q4

q2

q7 q6q8

p4p2

q1q3

M = [ {p0, q0},1 1 {p0, q0},2 1 {p0, q0},8 1{p0, q0},1 2 {p0, q0},1 8 {p0, q0},3 1{p0, q0},7 1 {p0, q0},2 2 {p0, q0},8 2{p0, q0},2 8 {p0, q0},8 8 {p0, q0},1 3

{p0, q0}, . . .1 7

S

{p0, q0} ]5 5

Sorted sector pairs

Searched sector pairs

New feasible sector pairs

Previous feasible AP sector

Previous feasible UE sector

Searched AP sector

Searched UE sector

Feasible AP-UE links

New feasible AP sector

New feasible UE sector


AP AP AP

UE

UE UE

Established link Link disrupted Link re-established→→


9

experimental evaluation in real indoor environment using 60 GHz packet radio transceivers

FILLER• UE mobility along ‘walks’

• link disruption along walks ⇒ algorithm triggered

• re-establish link using (i) previous feasible sector pair knowledge and (ii) derived feasible sector pair information

FILLER

RSS measured for various UE locations ⇒ AP-UE feasible sector pairs

determined

Measurement points

60 GHz AP60 GHz UE


10

CONTD.

Indoor environment:

AP Concrete

Plasterboard

Brick

Glass

Wood

Metalized Glass

T U VCEFGH

IJK L M N O P

QRSD

AB

Concrete

Plasterboard

Brick

Glass

Wood

Metalized Glass

indoor environment with UE locations (A – V) for RSS measurement


11

CONTD.

60 GHz packet radio transceiver:FILLER

• SiversIMA mm-wave converter + USRP platform (GNU Radio) • USRP (Baseband ↔ IF) ↔ SiversIMA (IF ↔ RF)• Turntable → change antenna orientationFILLER

• For our measurement…IF freq. 1.5 GHzRF freq. 60 GHzAP TX power –10 dBmRX sensitivity threshold –78 dBm

SiversIMA mm-wave up/down converter

USRP

Turntable module

Horn antennaGain = 15 dBi,

Beamwidth = 30°

0 2 4 6 8 10 124

5

6

7

8

9

10

11

12

AP

12

CONTD.

RSS measurement:

FILLER

• RSS measured for all UE locations & AP-UE sector pair

• if RSS > RX Sensitivity Threshold

⇒ Feasible sector pair

Feasible sector pairs for indoor environment



AP

CDEFGH

IJ

OK

RQP

ST

NL

13

CONTD.

Performance evaluation:FILLER

• UE moves along walks ⇒ link disruption

• link re-establishment using:

1. previous feasible sector pair

2. feasible sector pairs (from RSS measurement)

• algorithm evaluated in non-real time

⇒ real-time evaluation highly time consuming ⇒ mechanical beamsteering

AP

ABCDEFGH

IJ

ONMLK

RQP

SVUT

AP

ABC

ONM

RQP

SVUT

Walk I

Walk II

Walk III


• Performance metrics:

1. #. of sector pairs searched (|P|)

2. search space reduction* (in %)

3. RSS difference*

4. data rate

14

* Comparing our algorithm with exhaustive sequential scanning

Search space and latency reduction

Re-established link quality

0 2 4 6 8 10 12 14 16 18 20 22

-90

-80

-70

-60

-50

-40

-30

UE Positions

RS

S [d

Bm

]

0 2 4 6 8 10 12 14 16 18 20 220

24

48

72

96

120

144

|P|


Walk I

15

Receiver sensitivity threshold

|P|RSS

|P|RSS

exhaustive sequential scanning

fast beamsteering algorithm

AP

ABCDEFGH

IJ

ONMLK

RQ

P

SVUT

Avg. # sector pairs searched = 15.6

Avg. search space reduction = 84%

Avg. RSS difference = drop by 5.8 dB

CONTD.

0 2 4 6 8 10 12 14 16 18 20 22

-90

-80

-70

-60

-50

-40

-30

UE Positions

RS

S [d

Bm

]

0 2 4 6 8 10 12 14 16 18 20 220

24

48

72

96

120

144

|P|

AP

ABC

ONM

RQ

P

SVUT


Walk II

16

CONTD.





|P|RSS

|P|RSS



0 2 4 6 8 10 12 14 16 18 20 22

-90

-80

-70

-60

-50

-40

-30

UE Positions

RS

S [d

Bm

]

0 2 4 6 8 10 12 14 16 18 20 220

24

48

72

96

120

144

|P|

AP

CDEFGH

IJ

OK

RQ

P

ST

NL


Walk III

17

CONTD.





|P|RSS

|P|RSS




• Overall results:

FILLERFILLER

• link re-establishment latency highly reduced

• re-established link not always optimal ⇒ data rate reduces

• tradeoff between re-establishment latency and link quality!

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CONTD.

# sector pairs searched

search space reduction

RSS difference

Data rate*

Average 14 89% 07 dB (less) – Worst case 24 83% 25 dB (less) 2.1 Gbps

* Considering IEEE 802.11 ad OFDM PHY

CONCLUSIONS & FUTURE WORKS

FILLER

• generic, low latency beamsteering algorithm; tackles UE mobility issue

• experimental evaluation in indoor using 60 GHz packet radio transceivers

• 89% (avg.) reduction in link search & re-establishment latency

• link RSS 7 dB (avg.) less than best case link RSS⇒ worst case data rate of 2.1 Gbps

FILLER

• presently investigating trade-off between data rate drop and link re-establishment latency

19

QUESTIONS?

For queries, please mail us at:

Avishek Patra [email protected]

Ljiljana Simić [email protected]

Marina Petrova [email protected]

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mailto:[email protected]



Engineering

Experimental Evaluation of a Novel Fast Beamsteering Algorithm for Link Re-Establishment in mm-Wave Indoor WLANs