experimental evaluation of a novel fast beamsteering algorithm for link re-establishment in mm-wave...
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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, . . .
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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
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CONTD.INTRODUCTION TO MM-WAVE NETWORKS
- 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
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CONTD.INTRODUCTION TO MM-WAVE NETWORKS
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
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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
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CONTD.
re-establishment latency ∝ # of sector pairs
searched
FAST BEAMSTEERING ALGORITHM
• 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
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[1]
[1] – Patra et al. “Smart mm-Wave Beam Steering Algorithm for Fast Link Re-Establishment under Node Mobility in 60 GHz Indoor WLANs”
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CONTD.
access point(AP)
user equipment (UE)
p1
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p3p4
p2
p8
q5q4
q2
q7 q6q8q1
q3
UE mobility causes link disruption
p1p8
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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
FAST BEAMSTEERING ALGORITHM
AP AP AP
UE
UE UE
Established link Link disrupted Link re-established→→
EXPERIMENTAL EVALUATION METHODOLOGY
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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
EXPERIMENTAL EVALUATION METHODOLOGY
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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
EXPERIMENTAL EVALUATION METHODOLOGY
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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
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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
EXPERIMENTAL EVALUATION METHODOLOGY
EXPERIMENTAL EVALUATION METHODOLOGY
AP
CDEFGH
IJ
OK
RQP
ST
NL
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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 RESULTS & ANALYSIS
• Performance metrics:
1. #. of sector pairs searched (|P|)
2. search space reduction* (in %)
3. RSS difference*
4. data rate
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* 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|
PERFORMANCE RESULTS & ANALYSIS
Walk I
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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
PERFORMANCE RESULTS & ANALYSIS
Walk II
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CONTD.
Avg. # sector pairs searched = 23.3
Avg. search space reduction = 84%
Avg. RSS difference = drop by 6.3 dB
Receiver sensitivity threshold
|P|RSS
|P|RSS
exhaustive sequential scanning
fast beamsteering algorithm
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
PERFORMANCE RESULTS & ANALYSIS
Walk III
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CONTD.
Avg. # sector pairs searched = 3.9
Avg. search space reduction = 97%
Avg. RSS difference = drop by 9.3 dB
Receiver sensitivity threshold
|P|RSS
|P|RSS
exhaustive sequential scanning
fast beamsteering algorithm
PERFORMANCE RESULTS & ANALYSIS
• 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
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QUESTIONS?
For queries, please mail us at:
Avishek Patra [email protected]
Ljiljana Simić [email protected]
Marina Petrova [email protected]
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