Chalmers University of Technology
Vehicles(and(Internet(of(Things:(
Antenna(Systems(for(Robust(
Connec<vity((
Keerthi%Kumar%Nagalapur ,%Erik%G.%Ström ,%Fredrik%Brännström ,%%
Jan%Carlsson‡,%and%Kris9an%Karlsson‡%
%
Chalmers%Univ.%of%Technology,%Dept.%of%Signals%and%Systems,%Gothenburg,%Sweden%
‡%SP%Technical%Research%Ins9tute%of%Sweden,%Dept.%of%Electronics,%Borås,%Sweden%%
%
%
Erik%G.%Ström%!%Antenna%Systems%for%Robust%Connec9vity ! EuCNC%2016%!%June%29,%2016%
1
Chalmers University of Technology
Modern(Cars(are(Important(Things(
RKE/TPMS RF
RKE LF × 6
Alarm sensor
GNSS
3G/4G
Bluetooth
WLAN bgn
Radar
GNSS (Sat nav.)
3G/4G MIMO
DAB L-band/SDARS
WLAN 802.11bgn
WLAN 802.11p × 2
TPMS × 4
DAB III/DVB-T × 4
Broadcasting
AM/FM1/FM2/TMC
Radar (obstacle) × 2
In(a(Modern(Car(
(
Approximately%
•  40%antennas%
•  100%sensors%
•  100%ECUs%(computers)%
•  2%km%cable%harness%
•  125%kHz%–%100%GHz%
•  Volume:%5%x%2%x%1.5%m%
%
Erik%G.%Ström%!%Antenna%Systems%for%Robust%Connec9vity ! EuCNC%2016%!%June%29,%2016%
2
Chalmers University of Technology
Coopera<ve(Intelligent(Transport(Systems((CAITS)(
Traffic(Safety(
• 
• 
• 
• 
Traffic(Efficiency(
Coopera9ve%"%V2X%communica9on%
State`of`the%art:%ITS`G5,%DSRC%based%on%IEEE%802.11p%MAC%and%PHY%
Data%traffic:%periodic%broadcast%transmission%of%status%messages%
Time%scales:%packet%lengths%<%1%ms,%packet%periods%≥%100%ms%
Image%sources:%Car`2`Car%Communica9on%Consor9um,%FP7%project%SARTRE%
Erik%G.%Ström%!%Antenna%Systems%for%Robust%Connec9vity ! EuCNC%2016%!%June%29,%2016%
3
Chalmers University of Technology
Propaga9on%
Antenna%System%
E1 (✓1 , t)
g1 (✓)
y10 (t)
E2 (✓2 , t)
g2 (✓)
y20 (t)
0
gNe (✓) yN
(t)
e
EM (✓M , t)
Receiver%
y1 (t)
CN
RX
yNp (t)
•  Propaga9on:%%%%%%plane%waves%incident%in%horizontal%plane%with%AOA%%
M
✓
Ne
•  Antenna%system:%%%%%%%antenna%elements%combined%with%a%linear,%9me`
Np
varying%network%into%%%%%%%antenna%port%signals%
M
X
yl0 (t) =
ETm (✓m , t)gl (✓m ), n = 1, 2, . . . , Ne
m=1
yn (t) =
Ne
X
cn,l (t)yl0 (t),
n = 1, 2, . . . , Np
l=1
cn,l (t) = complex%gain%from%antenna%element%%%to%port%%
n
l
Erik%G.%Ström%!%Antenna%Systems%for%Robust%Connec9vity ! EuCNC%2016%!%June%29,%2016%
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Chalmers University of Technology
Challenges(and(Mo<va<on(
•  Antenna%elements%far`field%func9ons%depend%on%placement%on%vehicle%
and%can%be%vary%significantly%with%the%AOA%(very%far%from%isotropic)%
•  To%achieve%acceptable%performance,%we%probably%need%mul9ple%
antenna%element%mounted%on%different%parts%of%the%vehicle%(front,%%
back,%sides,%etc.)%"%%Ne > 1
•  Advanced%mul9port%receivers%with%channel`state%dependent%
combining%(e.g.,%selec9on%combining,%maximal%ra9o%combining)%could%
be%too%costly%"%it%is%likely%that%%Np < Ne
•  Designing%a%fixed%combining%network%for%robustness%relies%on%
accurate%knowledge%of%antenna%far`field%func9ons%gl (✓), l = 1, 2, . . . , Ne
•  Ques9on:%can%we%design%a%<meAvarying%combining%network%that%is%
robust%against%AOA%and%does%not%require%detailed%knowledge%of%
channel%state%informa9on,%SNR%and%antenna%far`field%func9ons?%%
Erik%G.%Ström%!%Antenna%Systems%for%Robust%Connec9vity ! EuCNC%2016%!%June%29,%2016%
5
Chalmers University of Technology
Problem(Statement(
Design combining network for robustness%
•  Assump9ons%
–  Periodic%data%traffic%(e.g.,%CAM/BSM)%
K
–  Outage%criteria:%loss%of%%%%%consecu9ve%packets%
–  Bad%propaga9on:%single%plane%wave%with%worst`case%AOA%
–  No%access%to%channel%state%informa9on%in%combining%network%%
•  Simplified%scenario%in%this%paper%
–  Two%antenna%elements%Ne = 2
–  One%receiver%port%Np = 1
–  Combining%network:%one%phase%shiper,%one%adder%
c1,1 (t) = 1,
c1,2 (t) = exp( j(↵t + ))
%%
Objective: find best phase slope (↵) for worst-case scenario%
Erik%G.%Ström%!%Antenna%Systems%for%Robust%Connec9vity ! EuCNC%2016%!%June%29,%2016%
6
Chalmers University of Technology
Combining(Network(under(Study(
%
E(✓, t)
(t) = ↵t +
✓
g1 (✓)
d
y1 (t)
T
T
T
⌧
g2 (✓)
e
j(↵t+ )
↵
Find%best%slope%(%%%)%%
for%worst`case%offset%(%%%)%and%AoA%(%%%)%
✓
Erik%G.%Ström%!%Antenna%Systems%for%Robust%Connec9vity ! EuCNC%2016%!%June%29,%2016%
7
Chalmers University of Technology
E(✓, t)
✓
•  Assuming%phase%ship%approximately%
constant%over%one%packet,%the%average%
k
SNR%for%packet%%%%%is%
g1 (✓)
d
y1 (t)
g2 (✓)
Pr
¯ (✓, ↵, , kT ) =
|g(✓, ↵, , kT )|2
e j(↵t+
2Pn
✓ ✓
◆◆
2⇡
g(✓, ↵, , t) = g1 (✓) + g2 (✓) exp
j
d sin ✓ + ↵t +
)
•  Outage:%loss%of%%%%%consecu9ve%packets%"%outage%probability%is%
K
Pout (✓, ↵, , K) =
K
Y1
Pe (¯ (✓, ↵, , kT ))
Packet%error%prob.%%
for%packet%%k
k=0
•  Task:%find%op9mum%slope%of%phase%ship%func9on%for%worst`case%%✓,
↵⇤ = arg min
↵ 0
max
✓, 2[0,2⇡)
Pout (✓, ↵, , K)
Erik%G.%Ström%!%Antenna%Systems%for%Robust%Connec9vity ! EuCNC%2016%!%June%29,%2016%
8
Chalmers University of Technology
Experiments(
•  Two%monopole%antennas%
placed%on%the%roof%of%a%Volvo%
XC90%(SUV)%
•  Radia9on%paqerns%measured%
in%a%semi`anechoic%chamber%
Erik%G.%Ström%!%Antenna%Systems%for%Robust%Connec9vity ! EuCNC%2016%!%June%29,%2016%
9
Chalmers Univ. of Technology, Dept. of Signals and Systems, {kee
University of Technology
‡ SP Technical Research Institute ofChalmers
Sweden,
Dept. of Electron
✓=0
Power gain in dBi
10
330
30
0
10
300
60
20
30
40
270
90
240
|g1 (✓)|2
|g2 (✓)|2
120
210
SNR of
is given
Pr /N0 =
observe
antenna
very low
AOAs c
imized b
combini
from all
using th
individu
is optim
150
180
In t
Fig. 1. Measured radiation patterns of two monopoles
mounted
theb roof
•  Packet%error%probability%is%approximated%as%
Pe (¯ ) =
ae b¯on
, a,
> 0 combine
vehicleof a vehicle. The monopoles exhibit⇤ non isotropic power gains.
↵ = 2⇡/(KT )
g1 (✓), g2we
(✓) have
%%%%%%%"%the%op9mum%phase%slope%is%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%independent%of%%
K cons
100
Erik%G.%Ström%!%Antenna%Systems%for%Robust%Connec9vity ! EuCNC%2016%!%June%29,%2016%
The 10co
|g1 (✓)|
|g2 (✓)|2
210
150
Chalmers University of Technology
180
In this pape
combine the out
Fig. 1. Measured radiation patterns of two monopoles mounted on the roof
vehicle-to-vehic
of a vehicle. The monopoles exhibit non isotropic power gains.
Worst`case%outage%
we have designe
Pout (✓, ↵⇤ , , K)
K consecutive p
100
The combining
Ant. 1
gain%
Ant. 2
instantaneous co
1
10
Combined
each antenna bra
of the antennas
2
10
the scheme.
10
3
10
4
10
5
10
The propose
nodes with strict
low cost antenna
K=5
and combined u
Pr /Pcommunications
n = 15 dB
(1/5)¯
Pe (¯ ) =
e
In this paper
⇤
have
two anten
↵
= 2⇡/(KT
)
6
0
50
100
150
200
✓ [deg]
250
300
350
Erik%G.%Ström%!%Antenna%Systems%for%Robust%Connec9vity ! EuCNC%2016%!%June%29,%2016%
Fig. 2.
Outage probability as a function of AOA ✓ for individual antennas
extend the deve
and receiver por
11
Chalmers University of Technology
Conclusions(and(Outlook(
•  Presented%a%general%framework%for%op9mizing%combining%network%for%
robust%connec9vity%for%systems%with%two%antenna%elements,%one%
antenna%port%receivers,%i.e.,%%Ne = 2, Np = 1
•  When%the%packet%error%probability%is%exponen9ally%decaying%with%SNR,%
↵⇤ = 2⇡/(KT )
the%op9mum%phase%slope%is%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
–  independent%of%the%antenna%element%far`field%func9ons%
•  Method%evalua9on%with%prac9cal%antenna%elements%mounted%on%a%
Volvo%XC90%shows%promising%gains%
•  Future%work%include%
–  Solve%general%case%for%mul9port%receivers%1 < Np < Ne
–  Quan9fy%the%robustness/average%performance%trade`off%
Erik%G.%Ström%!%Antenna%Systems%for%Robust%Connec9vity ! EuCNC%2016%!%June%29,%2016%
12