CENTRE FOR TELECOMMUNICATIONS-TRANSMISSION AND RADAR
. .
~ngs
of the IRCTR Colloquium on
Indoor Communications
Delft, 24
October 1997
"
K
Proceedings of the IRCTR colloquium on
Indoor Communications
in cooperation with IEEE Vehicular Technology
/
Communications Society Joint Chapter in Benelux
Delft, 24 October 1997
Bibliotheek
TU
Delft
IIIII
I
IIII
I
II
III
II
I 11"1
II
IIIII I
11
C
0003813899
Papers presented at the International Colloquium held in Delft,
The Netherlands, 24 October 1997
2414
545
... _--_._----_ ... -. _
-On the organisations
~rJl
IRCTR is established as a centre of expertise in the fields of
U~
Telecommunications-transmission and Radar. IRCTR operates as a
non-profit making institute, based within the Faculty Information Technology
and Systems of the Delft University of Technology in The Netherlands. IRCTR is a project
driven research institute. The pre-competitive project are supported by the NWO (National
Science research Council), the STW (Foundation for Technical Sciences), the Dutch ministry
of Education, Culture and Sciences, the GTI's and industries. IRCTR provides the essential
interface to promote international research advancement.
At the IRCTR the fundamental and experimental research projects are being carried out in
four sectors
.
The research areas in some keywords:
Sector Antennas and Propagation: time domain measurement, hybrid reflector systems,
wide band antennas, modeling of propagation.
Sector Radar: radar system design, wide band radar, multi-parameterlDoppler polarimetric
radar, integrated radar communications.
Sector Transmission
:
hybrid multiple access schemes, broadband multi-media
communications, wireless ATM, networking, smart antenna and coding
.
Sector Remote Sensing
:
study of the atmosphere, especiaJly on cIouds, physical parameters
in the scattering process of radar waves, extraction of these parameters.
IEEE -
the Institute of Electrical and Electronics Engineers
~
lEE -
the Institution of Electrical Engineers
lEE
Programme committee:
Prof.Dr. R. Prasad (IRCTR)
Prof.Dr.Ir. L.P
.
Ligthart (IRCTR)
W
.
L.M. van der Voort-Kester (IRCTR)
The contents of the publication has been reproduces directly from the material supplied by the
authors
.
Uitgegeven
en gedistribueerd door:
Delft University Press
Mekelweg4
2628
CD Delft
telefoon: +31 15 278 3254
fax:
+31 152781661
:
DUP@DUP.TUDelft.NL
CIP-GEGEVENS KONINKLIJKE BIBLIOTHEEK, DEN HAAG
Indoor Communication
s
Indoor Communications - Delft: Delft University Press. - Illustrations.
ISBN 90-407-1549-1
NUGI 841
Trefw.: Indoor, Communications
Copyright
©1997 by Delft University Press
All
rights reserved.
No
part
of
the material protected by this
copyright
notice may be
reproduced
or
utilized in
any
form
or
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any
mean
s,
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mech
a
nical, inc1uding
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information
storage and
retrieval
system,
without permission
from
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Press,
Mekelweg 4
,2628
CD Delft
,
The Netherlands.
Centre for Wireless Personal Communications (CEWPC)
Considering the multidisciplinary
activity
in the
field of wireless
personal
communications
,
the Board
of
the
Faculty of
Information Technology
and Systems of
Delft
University of
Technology
(DUT),
The
Netherlands,
has the intention to
establish
the
"
Centre for Wirele
s
s
Personal Communications
(CEWPC)"
under the umbrella
of
the International Research
Centre
for Telecommunications-transmission
and
Radar
(IRCTR).
The Centre
will
be
a centralized
research and
development
(R&D) activity of
the
experts of Electromagnetics (EM),
Telecommunications
and
Remote Sensing Technology
(TTT)
,
Telecommunications
and
Traffic-Control Systems (TVS)
,
Computer
Architecture and
Digital
Techniques (CARDIT)
,
Information Theory (IT)
& Circuits and
Systems
(C&S)
Laboratory, Delft Institute
for
Microelectronics
and
Submicron Technology
(DIMES) and other faculties of
DUT
(e.g
.
Faculty
of
Mathematics
&
Informatics).
The Centre
wil! conduct
R&D in four major
areas,
namely, Systems,
Networks
,
Technology
,
Services
and Applications.
The Centre
will
have
six
major
activities,
namely
i)
Long-Term
research, ii) Funded R&D projects, iii) Refresher
training
programmes by
conducting
workshops
and
tutorials, iv) Annual Symposium, v)
Teaching
Programme
(M
.
Sc.
& Ph.D.
thesis,
Undergraduate
and
Graduate Courses)
and vi)
International Conferences
.
The CEWPC
will
be
opened
to
all industries. Finally,
the
CEWPC will
be
open
to develop
international cooperation
with
universities based on the
selected
criteria
and other Centres for
Wireless Communications
.
The Centre
wiU offer an opportunity for
industry to receive
significant valued
information
from
the research
work carried out
at the
Faculty
of Electrical
Engineering
.
The
Centre will
offer
industry
a very cost
effective
solution
to
funding
long
term
research
.
The Centre further
will
offer
a good
platform
for getting a group of
industries/companies to
fund an application
oriented
research programme
on a shared cost
basis
.
The
Centre will
provide
an effective
mechanism for
carrying out such a
programme. Let us hope the industries
come forward to
use
this opportunity to work together to
achieve
the objectives
of
the Global
Communications
Village.
The Centre
will
need
support from
the Government and
other
nationallinternational
funding
agencies
to
shape
the direction
of
the Centre for
Wireless
Personal Communications.
Contents
Session 1: CEWPC
(Chairman:
Dr.
H.
Huomo, Nokia Research
Centre,
Helsinki, Finland)
1. Welcome address
by ProfDr.Ir. E. Backer
(TU
Delft)
2. Introductory speech
by ProfDr.Ir. L.P. Ligthart
(TU
Delft)
3.
ConcIuding remarks
by ProfDr. R. Prasad
(TU
Delft)
Session 2: Key-note speech
(Chairman
:
Dr
.
K.
Fa
z
el
,
DLR
,
Germany)
4.
Wireless Personal
&
Multimedia Communications
by Dr.
S.
Kato
(Uniden Corporation,
Japan)
paper
not
available at
the time
of
printing
Session
3: Indoor Propagation and Systems
(Chairman:
Dr.
Eisuke
Fukuda
,
Fujitsu
Europe,
UK)
S.
Indoor Radiowave Propagation Measurements and Stochastic Channel Modelling
by Prof.Dr. P. Leuthold
(ETH
Zurich, Switzerland)
"'
6. Multi-rate Wideband DS-CDMA: Promising Radio
A~cessTechnology for Wireless
Multimedia Communications
.
by Dr.
F.
Adachi (NTT DOCOMO
, Japan)
7. Performance of
DE
CT
Receivers with Burst-to-Burst Adaptive Synchronisation
by Prof.Dr. E. Bonek
(TU Wien, Austria)
Session 4: Indoor Services and Application
(Chairman: Dr. R
.
-H. Yan, Lucent Technologi
e
s, UK)
8. Indoor and Proximity Communications in the MTS context
by Mr.
J. Rapeli (Philips Consumer Communications, France)
paper not available at the time of printing
9. DECT and its Applications
by Ir. R. van Kemenade (Siemens Nederland, The Netherlands)
10. Wireless Broadband Communications at the Millimeter Waveband: Differences &
Similarities between WLANS & MBSs
by Prof.Dr. L.M. Correia (Inst.Sup.Tecnico
,
Portugal)
Session 5: Indoor Networks
(Chairman: Dr
.
K.
Sabatakakis
,
CSEM, Switz
e
rland)
11. Wireless ATM via the Spatial Domain
by Dr. M. Beach (Univ. of Bristol
,
United Kingdom)
12. Wireless LANs Today & Beyond
by Dr. B
.
Tuch (Luc
e
nt Technologie
s
, The Neth
é
rl
a
nds
)
13. European R&D in Mobile and Personal Communications: Indoor to Full Mobility
by Dr. 1. Pereira (European Commission
,
Belgium)
Indoor
Radiowave Propagation Measurements and
Stochastic Channel Modelling
Peter E.
L
e
uthold
a
nd Pascal Truff
e
r
Swiss Federal Institut
e
of
Technology (ETH)
,
Communication T
ec
hnolo
gy
Laboratory
ETH Zentrum
,
CH-8092 Zurich
,
Switzerland
e
-mail:
leuthold@nari.ee
.
ethz
.
eh
August 29, 1997
Abstract
Mod
e
lling
of
indoor radio
c
hannels in
the
UHF
,
SHF
and
EHF r
a
n
ge
i
s a
k
ey
issue
for th
e
design of
modern wir
e
l
ess
lo
ca
l
a
re
a co
mmuni
cat
i
on systems.
Stochas-tic
radio
channe
l
mod
e
ls
(
SRCM) rev
ea
l
to
b
e a
dv
a
nt
ageo
us
com
p
a
r
ed to ot
h
e
r
simu
l
ation schemes
.
In
order
to
ca
lculat
e
th
e
par
ame
t
e
r
set
o
f
the
diff
e
r
ent
target
functions for the r
a
ndom v
a
ri
ab
l
es
in
the
SRCM, i.
e
.
path
lo
ss,
path d
e
l
ay,
in
ci-dence dir
ec
tions
and
Doppi
e
r
s
hift
of the wave components, the measurem
ent
of the
co
mplex
c
h
a
nnel impul
se
r
espo
n
se
of
th
e
dominant p
at
h
s
i
s
n
ee
d
ed.
A
nov
e
l
c
hannel
sounder
co
ncept bas
e
d
on
optic
a
l millim
e
t
e
r wave
ge
n
e
r
a
tion h
as
b
ee
n
developed to
so
lve this problem
a
t
ex
trem
e
l
y
high fr
eq
u
e
nci
es.
Math
e
m
a
ti
ca
l method
s s
uitabl
e
for
the
extra
ction
of
import
a
nt par
a
m
ete
r
s
from
the
m
eas
ur
ed
data
a
r
e
di
sc
u
ssed
briefty.
1
Introduction
Efficient wir
e
l
ess
indoor tr
a
nsmission repres
e
nts a key t
ec
hnology to pave th
e
way
tow
a
rd
the
realization
o
f univ
ersa
l p
e
rson
a
l
te
l
ecommun
i
cations (UPT)
[1]. Cordl
ess
t
e
l
ep
hon
y
and
d
ata
services on
r
ad
i
o
loc
a
l
a
r
ea
n
e
twork
s
(R
LA
N) are
alr
ea
d
y
weU
estab
lish
ed.
To-day
,
indoor
com
muni
cat
i
o
n
s
without wirin
g e
volve from voice
a
nd low d
a
t
a
r
ate
services
tow
a
rd high
bit
rat
e se
rvi
ces, e
.
g
. videophony
a
nd
e
ven multi-medi
a, ca
u
s
in
g an
in-creasing
dem
a
nd
of
mobil
e
ISD
N an
d B-ISD
N
term
in
a
l
s
(Bro
ad
b
a
nd-Int
egrate
d S
erv
i
ces
Di
g
it
a
l
Netw
ork
) as
weU
as
the
n
ee
d
of
l
a
r
ge
r interconn
ect
ion
ca
p
ac
ity b
etwee
n m
ova
bl
e
p
e
r
so
n
a
l
computers or workstations
,
resp
ect
iv
e
ly
,
and
th
e
ir
se
rv
e
rs
.
In
order to
ac
hi
eve
compat
ibilit
y
with wir
ebo
und
ed
n
etwo
rk
s, e.g.
Eth
ernet
(
10
Mbit
/s)
,
FDDI
(
Fib
e
r
Di
s
-tributed
D
ata
In
te
rf
ace,
100
Mbit
/s
)
a
nd B-ISD
N
(155 Mbit/s), radio
t
r
ansm
i
ss
ion
of
bit
r
ates
hi
g
h
e
r
t
h
a
n
1
Mbit/s
up
to the
ran
ge of
100 Mbit/
s
is r
e
quir
e
d.
Correspondingly
,
transceiver
structures
using
complex
modulation schemes,
e.g. subband
transmission or
spread spectrum techniques
combined
with interference
cancellation
methods
and
mul-tiuser detection
.
Moreover, the need of wider bandwidths up to
a
few 100 MHz leads
to a
gradual displacement of
the exploited
frequency bands toward the millimeter-wave range.
During the forthcoming decade the development of new powerful wireless indoor
com-munication systems can be
expected according
to
already
introduced
standards,
i.e. IEEE
802.11
(1.
..
2 Mbit/s)
and
HIPERLAN (20 Mbit/s) or taking
account
of
specific
nor-malization
activities
performed within the frame of European UMTS (Universal
Mobile
Telecommunication Systems) or MBS programs (Mobile Broadband Systems)
.
Indoor
RLAN have to cope with the frequency
and
time selective channel characteristics mainly
because of multipath propagation
and
movements of the terminals
and
reflectors or
scat-terers, respectively. Hence
,
the detailed knowledge of the radiowave propagation
effects
within
buildings is inevitable for the development, performance
assessment
and design of
such wireless transmission systems. Global channel parameters like delay spread
,
coher-ence
bandwidth,
coherence
time, number of dominant paths, path loss
etc. are
needed
to
achieve a
first
approach
of
optimum
parameters. In the design phase
a
simulation of
the whole system induding
a channel
model which
accurately
imitate the transmission
constellation
by means
of synthesized channel
impulse responses (CIR) in
accordance with
the real
environment allows
the necessary performance
evaluation.
The model parameters
have to be
either calculated or extracted
from measurements.
Three principal
solutions
have been proposed to
simulate
the radio
channel
[2] : (1)
stored CIR
,
(2) ray-tracing
techniques applied
in the reference
environments
to
compute
the CIR
and
(3)
stochast
ic parametric models for the CIR
or stochastic
radio
channel
models (SRCM), respectively.
The SRCM
approach seems
to be
advantageous compared
to the two ot hers due to
the following properties:
• relatively low
computational complexity
•
small storage
capacity
•
adaptive to a
high
variability
of
the environments
• handy basis for theoretical
considerations
This paper
gives some
insight into the research activities in wireless indoor
communi-cations at
the Communication Technology Laboratory of ETH Zurich.
It
deals with the
indoor SRCM
as a
parametric model
and
describes the way how to
acquire
the
appro-,\..
priate parameter set.
The
second section
presents the dependence of the model
scheme
on various
effects of the operationscenario,
dispersion
and
transceiver
characteristics and
considers the
possibilities
of
reducing
the
model
complexity.
Subsequently
,
the model
parameters b
e
ing
random to some extent and
the
relationship
to the previously
men-tioned physical and technical
influences
are explained.
The
third
section introduces
a
nov
e
l
channel sounder concept
based
on optical
millimeterwave
generation
which permits
the
measurement of the complex envelop es of
the impinging waves
and
deals
with the
mat
h
ematica
l
prob
l
em how to
extract
significant parameters,
e.g. comp
l
ex
amp
li
tude,
path delay,
i
ncidence direction
etc
.
Fina
ll
y
,
conclusions
are
given
in the last
section.
2
S
t
och
ast
ic
Ch
a
nnel
M
o
delling
2
.
1
M
od
e
l
C
o
nce
p
ts
In princip
l
e, three different domains determine the radio
signal
transmission: the opera
-tion scenario, dispersion phenomena
of
wave propagation
and transceiver characteristics.
Table
1
shows a gener
ic
scheme
of
a
ll
the effects
which have
to
be
considered
with regard
to the set
-
up of the SRCM
[
3
]
.
Operation
Dispersion
Transceiver
Scenario
Mu
l
tipat
h
Short-term
Long-term
Characteristics
Propagation
F
l
uctuations
Fluctuations
- Frequency
-
Number of
For
each
path:
For
each
path:
-
Trajectory
r
ange
paths
- Fast fad
i
ng
- Path loss
- Ve
l
ocity
- Bandw
i
dth
For
each
path:
- S
h
adowing
- Antenna
-
Type
of
-
Mean power
- Transit
i
ons
configuration
environment
-
De
l
ay
- De
l
ay
dr
i
ft
-
Dopp
l
er
-
Direction
shift
drift
-
I
ncidence
direct
i
on
- Scattering
function
-
Polarization
Tab
l
e
1:
Generic
scheme of effects to
be
considered
for SCRM
Of
course, the
deterioration of the
transmiss
i
on quality is
strongly
depending
on the
signa
l
processing,
i.e. modulation,
coding,
detection
etc
.
,
but these
aspects are beyond
the scope of
a
me re
channe
l
model.
T
he operation
scenario
implies
some
fundamental data
l
ike frequency range
,
system
bandw
i
dth and
env
i
ronments, i.e. urban, rura
l
,
indoor
etc.
wh
i
ch
even
i
mpress the
gene
r
al
character
of a wire
l
ess
transm
i
ssion
link due to
the
relationship between the topographica
l
features
and
the wave
l
ength
or
the
time reso
l
ution, respectively.
Dispersion
i
n frequency,
time, direction
and
po
l
arization
is
a crucial aspect
of radio
communication.
We have to
distinguish between mu
l
tipath propagat
i
on where
each
path
suffers from a
multiplicity of
we
ll-
known
effects
as we
ll
as temporal
fluctuations which can be split off in
short
-
term or
sma
ll
-sca
l
e
fluctuations (fast fading)
and
l
ong-term
or
l
arge-scale
fluctuations compr
i
sing
gradual
and sudden
changes of path parameters mainly because of movements either of
the
contributing
to the SCRM
are the
parameters which describe the MT move ment
and
the
antenna configuration with
it
s
radiation pattern and
diversity properties
.
Concluding
from
Table
1
the
co
nsider
atio
n
of
a
ll
aspects
l
eads to a
r
at
h
er
hi
gh
com-putation
al complex
ity
of the SRCM. The ded
i
cat
i
on of the
SRCM
to a certa
in
class
of
operation scenario
,
i.e.
the delivery of
indoor
services
with
a given maximum
bit rate
(bandwidth)
at a
prescribed frequency
range,
i
s a
first
step
toward
a simplified
model
approach. Moreover, the
identification
of a
few types
of
env
ironment
a
ll
ows a
remarkable
comp
l
exity
r
ed
uction
.
Thus
,
four
important indoor
situations
have been
chosen
[2J:
•
sm all rooms
•
l
arge rooms
• f
actory
h
a
ll
s
•
corridors
Obviously,
the a
ll
ocated
frequency range plays
a
key role with respect to the path
loss
while the
room
dimensions
influence
direct
l
y
the
delay spread (DS).
Referring
to
the
uncer
ta
int
y
rel
at
ion
the system bandwidth
is inversely
proportional to the time
resolution
and
,
therefore, determines the
necessary
sampling rate of the
model.
Furth
ermore,
the question arises
if it
would be possible to
negl
ect
those effects
that
are expected to
have
only
little impact
on the system performance
.
lndeed, different
levels
of model complexity
can
be
introduced
according
to
the
transmission
co
n
ste
ll
ation
or the needed
acc
uracy
,
respectively. As an
exa
mpl
e,
two reduced comp
l
exity
l
evels are
proposed
[2]:
a) Minimum comp
l
exity :
• fr
equency
rang
e
• bandwidth
•
type of
e
nvironment
•
path
l
oss
•
multipath
prop
agat
ion
1• f
as
t fading
2•
MT mobility
21must contain at least number of paths, mean power and delay 2not necessary if MT are at fixed positions during operation
b) Medium complexity :
Minimum
comp
l
ex
it
y accord
in
g
to a)
plus
• shadowing
• transitions
Th
e evaluation of future generations of indoor RLAN
eq
uipp
ed with smart antennas
and
int
ended for
unrestrict
ed mobile operation will
require
full complexity channel modelling.
2.2 Determination
of
the Parameter Set
In
this paper the universal description of the dispersive radio channel
i
s
based on the
electric field delay-direction
spread vector
.E.(z., T,
D)
defined in
[4].
The vector
Z.denotes
the MT
antenna
lo
cation, and
Tand
D
are the delay and incidence direction variables
,
respectively
,
where D
is
determined by the azimuth 'P and the coelevat
ion
e
in
a spherical
coordinate system.
The vector
.E.(Jd.
,
T,
D)
can be decomposed
into
a s
um
of M components each originating
from a
hypothetical impinging
wave:
M('!.
)
.E.(z.,T,
D)
=
:L
.E.m(z.
,
T,
D).
(1)
m=l
The notation
M
=
M(z.)
means
that the number of
act
iv
e paths or dominant waves
varies with the
location
wh en the MT
i
s
moving
a
long
the trajectory. Under far field
conditions the vector
.E.(z., T,
D)
has two
components which correspond to the vertical and
horizont
al polarization. Considering
simp
l
y
on
e
polarization component we define the
scalar
field delay-direction spread function E(z., T,
D)
called FDDSF. The CIR follows by
h(Jd., T)
=
J
f(D)E(z., T, D)dD
,
(2)
where
f(D)
is proportional to the field pattern of the MT antenna for the considered
polarization
.
We now assume
that over a
sufficiently small area
A
the wave
incid
ence conste
ll
ation,
i.
e.
the number of active
paths
,
relative delay, angle of arrival
and amplitude,
remains
approximately constant.
Consequently
,
the spatial variations of the FDDSF mainly result
from the changes of the phase of the wave components.
Within the area
A
the wave incidence constellation
is
characterized by the
lo
ca
l
power
delay-direction profile
(PDDP)
PA(T,
D)
=
E'!.EA{IE(Jd., T
,
DW},
which may be presented
in
the SCRM
as
the product
(3)
(4)
In
this equation,
1/
P(d
A ) denotes the path loss for the distanced
Afrom the transmitter
station to
the
area
A
and
SA(T,
D) is the local
delay-direction scattering function
(DDScF)
in
A.
Sinc
e
the components
in (1)
are
regarded
as
independent we
obtain
with (4) the
exp
r
ess
ion
M M
PA(T
, D)
=
2:
Pm(T
, D)
=
2:
PmSA(T -
Tm,
D - Dm)
,
(5)
m=l m=l
that means
eac
h
term
is
determined
by
the
mean power Pm
,
the m
ea
n delay Tm
,
the
mean
in
cidence
direction
Dm
and alocal scattering
function SA(T
,
D)
which is
considered
to
b
e
id
ent
i
ca
l
for
all compone
nts.
Obviously, the variables
M
,
Pm,
Tm,
and
Dm
are
random vari
a
bles.
Random Variabie
Distribution Type
Int
erva
l
Remarks
M
Pois
so
n
M>O
M
~ (7TTm
uniform
0:::;
T
:::;
Tma
x
T max -- ---=L(7 logeT (COST 207)
<{Jm
uniform
- 7r :::; <(J<
7rD
e
m
8(e
-
7r/2)
rr2
horizont
al
pro-pagation
on
ly
Table 2:
D
esc
ription
of the
primary
random
vari
ab
les
M
,
Tm
,
Dm
(delay spread
(7T)Their
specificat
i
on
is
given
in Tabl
e
2
[2] with
the exception of
Pm
which will be
discussed
l
ater
on.
~ -5 E ~ -10 .~ E B -15
.
.•
~ -20î
~ -25 -30 300 60 30 Delay(ns)Figure
1:
Loc
a
l PDDP
ge
nerated
with the
SRCM
case
as
well
as
for
the
next Figur
es
2 to 6 the
following
parameters have
b
ee
n
chosen:
carrier frequency
5.2
GHz,
MT v
e
lo
c
ity 1 m/s
,
delay spread
(fT =5
0
ns.
Such
a
situation
is typic
a
l
for a small room
environ
m
e
nt
.
T
ak
in
g
the expectation of the lo
ca
l DDS
c
F
over a class
C
of e
nvir
onme
n
ts,
i.
e
.
a
l
a
r
ge
room,
y
i
e
ld
s
the global DDS
c
F
Sc(r
,
n)
=
E
AEc{
SA(r
, n)}.
(6)
In accordance with the
ass
umptions in T
ab
l
e
2 this function
takes t
h
e
form
1
7rSc(r,
n)
=
S
c
(r)-2 8(B - -)
,
7r
2
(7)
where
the global
d
e
lay
scattering
function
Sc(r) (DScF) foll
o
w
s
int
eg
r
at
ing
Sc(r,
n)
with respect to
n.
It is reasonabl
e
to
c
hoose the global DScF
as a
n
exponentia
lly dec
ay
in
g
function
(8)
th
a
t
means the scattered power
decreases with
in
c
r
eas
in
g
delay.
With regard
to
the
channel simulation
the
global
DDS
c
F
acco
rding to
(7)
a
nd
(8)
can
be
cons
id
e
r
ed
as
a
target function which repr
ese
nts the
expectat
ion of G
a
us
s
i
a
n processes with the
standard
d
e
viation
D.r
and
D.
I.p,
r
es
p
ect
iv
e
ly
.
,o~--,---,--"r====~====~==~====~ iD :!!. E g -5 .~
i
-'0
g
-15j
e -20~
..
-25 -30 50 '00 150 200 Oelay (ns)local OScF (one realizatIon) average of 1000 local DScF global DScF (theory)
250 300
Fi
g
ur
e 2:
Global
a
nd loc
a
l DS
c
F
350
Figure 2 shows the
successive
a
pproxim
a
tion
of
th
e
global
DS
c
F
by the average of
loc
a
l DScFs
.
2.2.1
Short-term Fluctuations
Following
(1) each component
Em(;r
,
T, D)can
be written
as a sum
of numerous plane
waves with r
a
ndom
characteristics.
In the SRCM the
amplitude,
delay
and
incidence
direct ion
are
r
a
ndomly
chosen
in
such
a
way that the resulting PDDP is close
to
Pm(T
,
D)
.
As
a
lr
eady
mentioned the short-term fiuctuations
of
the FDDSF
origin exclusively
in the
phase
changes that appear
during the MT
antenna
movement
along
the trajectory.
[0.8
.
~ 0.6 Co ~ ~O.4 ~ 0.2 Detay (ns)Figure
3:
Short-term fiuctuation of the CIR
Figure 3 presents
a
fiuctuating
CIR sample
generated with the SRCM
.
2.2.2 Long-term Fluctuations
Different important
effects giving
rise to
lon
g-term
fiuctuations have been implemented
in the
SRCM
:
• path
lo
ss
depending on the distance
•
variation of the number of active
paths
•
transitions wh ere
waves
ar
i
se and
vanish
• fiuctuation
of the
propagation delays
The simulation of path loss is based on the
extended
linear model
as
proposed in [5]:
L(d)
=
Lo
+
lOnlog(djm)
+
ad,
(9)
where Lo means the free-space loss
at
1 m distance
and
d denotes
the distance
between
the transmitter station
and
the MT
.
A power decay
exponent
of
n
=
2
and a
path
attenuation of
a
=
0.2
.
..
0
.
6
dBjm
reveal to be in good
agreement
with
experiment al
results.
Following [6] the locations
along
the trajeetory where paths become
active
form
a
Poisson process with
a certain
occurrence rate. The length of
the active segments
is
exponentially
distributed.
Time(s)
Figure 4: Variation
of
the number of
active
paths
The number of
active
paths
M(x.)
along
the trajeetory is then
a
Poisson process
with
the mean
M.
Figure 4 illustrates the variation of the number
of
dominant impinging
waves
.
The power
variation
of the multipath
components
in transit ion
situations
is
simulated
by means
of smooth
monotone functions
as suggested similarly
in [7] .
MT move ment will
also cause
fiuctuations of the delay
and
the incidence direction
of
the wave
components.
The location depend
e
ncy is described in [2]
.
No
model has be
en
d
e
velop
ed
yet to characterize the spatial
dependency
of the
varying incidence
directions
due to
a
lack
of experiment
a
l data.
Figure 5
shows
the infiuence of
adynamie
incidence
constellation
resulting in
Oela)'(III)
Figure 5: Long-term ftuctuations of
the
power
and
de1ay
of the waves
For
sake of comp1eteness
it
shou1d be
mentioned that because
of the simulation of the
changing number
of
active
paths
as
previous1y described
the so-called
shadowing
usually
represented
by a
lognormal
process
in
classic channe1
mode1s is inherent1y
embodied in
the
SRCM.
Figure 6: Path 10ss (shadowing)
Figure
6 presents this fact
in form
of a successive approximation of
the
target
func-tion
(9).
As
an examp1e,
Tab1e
3 shows the parameter set of
the SRCM
deve10ped
for
the
European ACTS project AC085 WAND (Wire1ess ATM Network Demonstrator) [2].
Ob-vious1y
,
the de1ay spread is re1ated to the
room
si
ze
while
M
as well as
D..r
and
D..t.p
Delay
Local PDDP
Pa th Loss
Environment
Spread
O"'T[ns]
MLh
[ns]
b.<p[o]
n a[dB/m]
Small Rooms
50
103
20
2
0.4
Large Rooms
100
20
1020
2
0.4
Factory Hall
150
30
20
30
2
0.4
Table 3: Parameter set for the WAND-SRCM
at
5.2 GHz [2]
are
determined by the
comp
l
exity
of the furniture
and equipme
nt
and
their geometry,
respectively.
3
Parameter Extraction from Measurements
3.1
A Novel Channel Sounder for the SRF and ERF Range
The wideband
channe
l
sounder ca
ll
ed
ECHO
24
(Enhanced Channel SQunder operating
at
24
GHz)
measures highly time-variant CIR's by
employing a correlation
method
.
It
achieves a
2 ns path delay resolution.
For
a coherent
demodulation of the transmitted signal the receiver has to be provided
with a
reference
signal at the carrier
frequency
fo. The intolerable frequency offset which
occurs wh en
using
different
local
oscillators
in the transmitter
and
receiver
can
be
over-come
by
a
remote
antenna
feeding in
conjunction
with
a common carrier
generated in
the
contro
l
station.
The problem of line
attenuation
in
coaxia
l
cab
le
s
is
circumvented
by
the
generation of appropriate opt
i
ca
l
signals
which
are
fed to the transmitter
and
receiver
via
thin
and
flexible fibers.
ECHO
24
us
es a
novel optical microwave
generation
princi-ple [8]. Furthermore
,
the absence
of mixers
and
frequency multipliers
yie
ld
s
rather small
and
handy units
which
diminish the distortion of the
electromagnetic
field that is to be
investigated
.
The block diagram of the
sounder
system which consists of a transmitter (Tx)
and a
receiver
(Rx)
module as
well
as of
a
cont
r
o
l
station,
is depicted in Figure 7
.
The optical
part
of the
contro
l
station contains a
l
aser
diode (LD)
and
two Mach-Zehnder
int
erfer-ometers
(MZI),
which are
used
as
li
ght
wave modulators. A quadrature modulation (I/Q
Mod)
i
s
performed by means
of a
PN
code
impressed on the local oscillator
signa
l
(LO).
The r
es
ul
ting
signal controls the first MZI which generates
a
double
sideband
suppressed
carrier (DSSC) modulation of the
laser light for the Tx module.
Th
e
l
aser
light supplied
to the
Rx
module
is modulated
at the second MZI
by the l
oca
l oscillator
signa
l only
.
Real
and
im
aginary
parts of the received
signa
l
are
returned to
the contro
l
station
by means
of
two standard coaxial cables
where
they are samp
led
for data
acquisition
purposes. The
subsequent offiine
data processing requires the knowledge of the PN sequence.
Both, the
Rx
and
the Tx module
are equipped
with
a
wideband
>"/4
monopole
antenna
Al
and
A
2.PN Code
Generator
r---~----~
~
Rx
Figur
e
7: Blo
c
k diagr
a
m of the
sounder system
(=
optical
fib
e
r)
Th
e
m
eas
ur
ed
CIR
of a
time-variant
ind
oo
r
c
h
an
n
e
l is
shown
in Fi
g
ur
e
8
.
Th
e
Tx
and the
Rx
module
are set
up in
a
di
sta
n
ce
of
fiv
e
meters. Af
ter
one minute
a
pers
on
e
nt
e
rs in b
etwee
n for
a
n
ot
her
minute.
Th
e
lin
e
of
s
i
g
ht (LOS) p
at
h i
s atte
nu
ated,
while
the
indir
ec
t p
at
hs
a
r
e
not influ
e
n
ce
d by
that
p
e
rson.
A
det
a
il
ed
description of
ECHO
24
i
s g
iv
e
n in [9]
.
o.l"y[nll
3.2 Evaluation Algorithms
As described in
the
previous
section
the
channel sounder
delivers a series of
complex
CIR
hm(;r,
T)
or
hm(t,
T)
,
respectively,
evoked
by the wave
component
impinging from different
directions
rl
m .The
extraction
of the data which is necessary to
calculate
the parameters of
the target functions
used
in the SRCM represents
a
fastidious task.
Numerous algorithms
are
available
which
can
be used to determine
either
single wave component parameters or
at once a collection
of them with
satisfying
precision.
The important wave
component
parameters
are as
follows:
• Am
complex
envelope (amplitude
Am
and
phase
qym)
• Tm
delay
• Um
Doppler
shift
A
global channel
parameter is the number
M
of active
paths which should
also
be
known in
order to assure
the
efficiency of
the
algorithms.
A
crucial task
is
the
determination
of
the incidence directions
of
the wave
components.
Beamforming
and
Fourier
algorithms
[10]
are
widely
applied
techniques to
estimate
the
angle of arrival.
In
the
past decade, high resolution
algorithms
have been
developed
to
extract the azimuth and even
the delay
of the
impinging waves
.
They
are based on spectral
or
non-parametric
estimation
principles like ESPRIT (Estimation
of
Signal Processing via
Rotational Invariance Techniques) [11]
and
MUSIC (Multiple Signal
Classification)
[12]
.
The latter
algorithm can
be
extended to
resolve not only the delay
and
the incidence
direction
but
also the
Doppler
shift.
Rel. Amplitude o laYrnaxlCIl [dB] ·10 20 30 ... 0 600 LOS., Azimut.;. I") 60 30
