Upload
raedapu
View
219
Download
0
Embed Size (px)
Citation preview
8/18/2019 Radio Propagation.ppt
1/44
Radio Propagation -
Large-Scale Path Loss
8/18/2019 Radio Propagation.ppt
2/44
EEE5302
Basics - Propagation
Radio waves are Easy to generate Can travel long distances Can penetrate bildings
!hey are both sed "or indoor and otdoor co##nication !hey are o#ni-directional$ can travel in all directions !hey can be narrowly "ocsed at high "re%encies &greater
than '00()*+ sing parabolic antennas &li,e satellite dishes+ Properties o" radio waves are "re%ency dependent
t low "re%encies. they pass throgh obstacles well. bt thepower "alls o"" sharply with distance "ro# sorce
t high "re%encies. they tend to travel in straight lines andbonce o" obstacles &they can also be absorbed by rain+
!hey are sb/ect to inter"erence "ro# other radio wave sorces
8/18/2019 Radio Propagation.ppt
3/44
EEE5303
Basics - Propagation t VLF, LF, and MF bands. radio
waves "ollow the grond ( radiobroadcasting ses (1 band
t HF bands. the grond
waves tend to be absorbed by the
earth !he waves that reach ionosphere
&'00-500,# above earth sr"ace+.are re"racted and sent bac, to
earth
absorption
re"lection
Ionosphere
8/18/2019 Radio Propagation.ppt
4/44
EEE530
Basics - Propagation
LS path
Re"lected 4ave
-Directional antennas are used-Waves follow more direct paths
- LOS Line-of-Si!ht "ommunication- #eflected wave interfere with the
ori!inal si!nal
VHF $ransmission
8/18/2019 Radio Propagation.ppt
5/44
EEE5305
Basics - Propagation
4aves behave #ore li,e light at higher
"re%encies i""iclty in passing obstacles
(ore direct paths
!hey behave #ore li,e radio at lower
"re%encies Can pass obstacles
8/18/2019 Radio Propagation.ppt
6/44
EEE5306
Propagation (odels
4e are interested in propagation
characteristics and #odels "or waves with
"re%encyy in range$ "ew ()* to a "ew 7)*
(odeling radio channel is i#portant "or$ eter#ining the coverage area o" a trans#itter
eter#ine the trans#itter power re%ire#ent
eter#ine the battery li"eti#e
1inding #odlation and coding sche#es to i#prove the
channel %ality
eter#ine the #a8i## channel capacity
8/18/2019 Radio Propagation.ppt
7/44EEE5309
Radio Propagation (odels
s the #obile #oves away "ro# the trans#itter overlarger distances. the local average received signalwill gradally decrease !his is called large-scalepath loss
!he #odels that predict the #ean signal strength "oran arbitrary-receiver trans#itter &!-R+ separationdistance are called large-scale propagation #odels
:se"l "or esti#ating the coverage area o" trans#itters
8/18/2019 Radio Propagation.ppt
8/44
8/18/2019 Radio Propagation.ppt
9/44EEE530=
S#all-Scale and Large-Scale 1ading
' '6 '; 20 22 2 26 2;
!-R Separation eters+
-90
-60
-50
-0
-30
Received Power &dB#+
!his "igre is /st an illstration
to show the concept
8/18/2019 Radio Propagation.ppt
10/44EEE530'0
4hat is ecibel &dB+
4hat is dB &decibel+$ logarith#ic nit that is sed to describe a ratio
Let say we have two vales P' and P2 !he di""erence &ratio+
between the# can be e8pressed in dB and is co#pted as
"ollows$ '0 log &P'>P2+ dB
E8a#ple$ trans#it power P' ? '004.
received power P2 ? ' 4
!he di""erence is '0log&'00>'+ ? 20dB
8/18/2019 Radio Propagation.ppt
11/44EEE530''
dB
dB nit can describe very big ratios withn#bers o" #odest si*e
See so#e e8a#ples$
!8 power ? '004. Received power ? '4 !8 power is '00 ti#es o" received power i""erence is 20dB
!8 power ? '004. Received power ? '#4 !8 power is '00.000 ti#es o" received power
i""erence is 50dB !8 power ? '0004. Received power ? '#4
!8 power is #illion ti#es o" received power i""erence is 60dB
8/18/2019 Radio Propagation.ppt
12/44EEE530'2
dB#
1or power di""erences. dB# is sed to denote
a power level with respect to '#4 as the
re"erence power level Let say !8 power o" a syste# is '004 @estion$ 4hat is the !8 power in nit o" dB#A
nswer$ !8power&dB#+ ? '0log&'004>'#4+ ?
'0log&'004>000'4+ ? '0log&'00.0000+ ? 50dB#
8/18/2019 Radio Propagation.ppt
13/44EEE530'3
dB4
1or power di""erences. dB4 is sed to
denote a power level with respect to '4 as
the re"erence power level Let say !8 power o" a syste# is '004 @estion$ 4hat is the !8 power in nit o" dB4A
nswer$ !8power&dB4+ ? '0log&'004>'4+ ? '0log&'00+ ?
20dB4
8/18/2019 Radio Propagation.ppt
14/44EEE530'
1ree-Space Propagation (odel
:sed to predict the received signal strengthwhen trans#itter and receiver have clear.nobstrcted LS path between the#
!he received power decays as a "nction o"!-R separation distance raised to so#epower
Path Loss$ Signal attenation as a positive%antity #easred in dB and de"ined as thedi""erence &in dB+ between the e""ectivetrans#itter power and received power
8/18/2019 Radio Propagation.ppt
15/44EEE530'5
1ree-Space Propagation (odel
1ree space power received by a receiver antennaseparated "ro# a radiating trans#itter antenna by adistance d is given by 1riis "ree space e%ation$
Pr &d+ ? &Pt7t7r λ2+ > &&π+2d2L+ E%ation 'D
Pt is trans#ited power Pr &d+ is the received power 7t is the tras#itter antenna gain &di#ensionless %antity+ 7r is the receiver antenna gain &di#ensionless %antity+ d is !-R separation distance in #eters L is syste# loss "actor not related to propagation &L ? '+
L ? ' indicates no loss in syste# hardware &"or or prposes wewill ta,e L ? '. so we will igonore it in or calclations+
λ is wavelength in #eters
8/18/2019 Radio Propagation.ppt
16/44EEE530'6
1ree-Space Propagation (odel
!he gain o" an antenna 7 is related to its a""ective
apertre e by$
7 ? π e > λ2 E%ation 2D
!he e""ective apertre o" e is related to the physical si*e o"the antenna.
λ is related to the carrier "re%ency by$
λ ? c>" ? 2πc > ωc E%ation 3D
" is carrier "re%ency in )ert*
ωc is carrier "re%ency in radians per second
c is speed o" light in #eters>sec
8/18/2019 Radio Propagation.ppt
17/44EEE530'9
1ree-Space Propagation (odel
Path loss. which represents signal attenationas positive %antity #easred in dB. is de"inedas the di""erence &in dB+ between the e""ective
trans#itted power and the received power
PL&dB+ ? '0 log &Pt>Pr + ? -'0log&7t7r λ2+>&π+2d2D E%ation D
&Fo can drive this "ro# e%ation '+
8/18/2019 Radio Propagation.ppt
18/44EEE530
';
1ree-Space Propagation (odel G
Re"erence istance d0
8/18/2019 Radio Propagation.ppt
19/44EEE530
'=
1ree-Space Propagation (odel
E8pressing the received power in dB# and dB4 Pr &d+ &dB#+ ? '0 log Pr &d0+>000'4D H 20log&d0>d+
where d ? d0 ? d" and Pr &d0+ is in nits o" watts
E%ation 9D
Pr &d+ &dB4+ ? '0 log Pr &d0+>'4D H 20log&d0>d+where d ? d0 ? d" and Pr &d0+ is in nits o" watts
E%ation ;D
Re"erence distance d0 "or practical syste#s$ 1or "re%ncies in the range '-2 7)*
' # in indoor environ#ents
'00#-',# in otdoor environ#ents
8/18/2019 Radio Propagation.ppt
20/44EEE530
20
E8a#ple @estion
trans#itter prodces 504 o" power + E8press the trans#it power in dB#
B+ E8press the trans#it power in dB4
C+
8/18/2019 Radio Propagation.ppt
21/44EEE530
2'
Soltion
+ Pt&4+ is 504
Pt&dB#+ ? '0logPt+>'#4+D
Pt&dB#+ ? '0log&508'000+Pt&dB#+ ? 9 dB#
B+
Pt&dB4+ ? '0logPt&4+>'4+DPt&dB4+ ? '0log&50+
Pt&dB4+ ? '9 dB4
8/18/2019 Radio Propagation.ppt
22/44EEE530
22
Soltion
Pr &d+ ? Pr &d0+&d0>d+2
Sbstitte the vales into the e%ation$ Pr &'0,#+ ? Pr &'00#+&'00#>'0,#+2
Pr &'0,#+ ? 00035#4&'0-+
Pr &'0,#+ ? 358'0-'04
Pr&'0,#+ dB#D ? '0log&358'0-'04>'#4+
? '0log&358'0-9
+ ? -65dB#
8/18/2019 Radio Propagation.ppt
23/44EEE530
23
!wo #ain channel design isses
Co##nication engineers are generally concernedwith two #ain radio channel isses$
Lin, Bdged esign Lin, bdget design deter#ines "nda#ental %antities sch as
trans#it power re%ire#ents. coverage areas. and battery li"e
8/18/2019 Radio Propagation.ppt
24/44
EEE5302
Lin, Bdged esign :sing Path Loss
(odels Radio propagation #odels can be derived
By se o" e#pirical #ethods$ collect#easre#ent. "it crves
By se o" analytical #ethods (odel the propagation #echanis#s #athe#atically and
derive e%ations "or path loss
Long distance path loss #odel
E#pirical and analytical #odels show thatreceived signal power decreases logarith#icallywith distance "or both indoor and otdoorchannels
8/18/2019 Radio Propagation.ppt
25/44
EEE53025
Long distance path loss #odel
!he average large-scalepath loss "or an arbitrary !-
R separation is e8pressed
as a "nction o" distance by
sing a path loss e8ponent
n$
!he vale o" n depends on
the propagation
environ#ent$ "or "ree space
it is 2I when obstrctionsare present it has a larger
vale
)log(10)()(
)()(
0
0
0
d
d nd PLdB PL
d
d d PL
n
+=
∝
dB)in(denotedddistanceaat
loss pathscale-largeaveragethedenotes)(d PL
E%ation ''
8/18/2019 Radio Propagation.ppt
26/44
8/18/2019 Radio Propagation.ppt
27/44
EEE53029
Selection o" "ree space re"erence
distance
8/18/2019 Radio Propagation.ppt
28/44
EEE5302;
Log-nor#al Shadowing
E%ation '' does not consider the "act thesrronding environ#ent #ay be vastlydi""erent at two locations having the sa#e !-R
separation !his leads to #easre#ents that are di""erent
than the predicted vales obtained sing theabove e%ation
(easre#ents show that "or any vale d. thepath loss PL&d+ in dB# at a particlar locationis rando# and distribted nor#ally
8/18/2019 Radio Propagation.ppt
29/44
EEE5302=
X σ is a *ero-#ean 7assian &nor#al+ distribted rando# variable &in dB+
with standard deviation σ &also in dB+
Log-nor#al Shadowing- Path Loss
)(d PL
σ
σ
X d
d nd PLdBd PL
X d PLdBd PL
++=
+=
)log(10)(][)(
)(][)(
0
0
!hen adding this rando# "actor$
denotes the average large-scale path loss &in dB+ at a distance d
)( 0d PL is sally co#pted ass#ing "ree space propagation #odel between
trans#itter and d0 &or by #easre#ent+
E%ation '2 ta,es into accont the shadowing a""ects de to clttering on the
propagation path
8/18/2019 Radio Propagation.ppt
30/44
EEE53030
Log-nor#al Shadowing- Received
Power !he received power in log-nor#al shadowing
environ#ent is given by the "ollowing "or#la
&derivable "ro# E%ation '2+
!he antenna gains are inclded in PL&d +
++−=
−=
][)log(10])[(][])[(
])[(][])[(
0
0 dB X d
d ndBd PLdBm P dBmd P
dBd PLdBm P dBmd P
t r
t r
σ
E%ation '2
8/18/2019 Radio Propagation.ppt
31/44
EEE5303'
Log-nor#al Shadowing. n and σ
!he log-nor#al shadowing #odel indicatesthe received power at a distance d isnor#ally distribted with a distance
dependent #ean and with a standarddeviation o" σ
8/18/2019 Radio Propagation.ppt
32/44
EEE53032
E8a#ple o" deter#ining n and σ
ss#e Pr &d0+ ? 0dB#
and d0 is '00#
ss#e the receiver
power Pr is #easredat distances '00#.
500#. '000#. and
3000#.
!he table gives the#easred vales o"
received power
Distance from$ransmitter
#eceived %ower
'00# 0dB#
500# -5dB#
'000# -''dB#
3000# -'6dB#
8/18/2019 Radio Propagation.ppt
33/44
EEE53033
E8a#ple o" deter#ining n and σ
4e ,now the #easred vales Lets co#pte the esti#ates "or received
power at di""erent distances sing long-
distance path loss #odel &E%ation ''+ Pr &d0+ is given as 0dB# and #easred vale
is also the sa#e #eanPr &d+ ? Pr &d0+ G #eanPL&"ro#d0 tod+
!hen #eanPr &d+ ? 0 G '0logn&d>d0+ :se this e%ation to co#pter power levels at
500#. '000#. and 3000#
8/18/2019 Radio Propagation.ppt
34/44
EEE5303
E8a#ple o" deter#ining n and σ
veragePr &500#+ ? 0 G '0logn&500>'00+ ? -6==n
veragePr &'000#+ ? 0 G '0logn&'000>'00+ ? -'0n
veragePr &3000#+ ? 0 G '0logn&3000>'00+ ? -'99n
Jow we ,now the esti#ates and also #easred
actal vales o" the received power at di""erent
distances
8/18/2019 Radio Propagation.ppt
35/44
EEE53035
8/18/2019 Radio Propagation.ppt
36/44
EEE53036
8/18/2019 Radio Propagation.ppt
37/44
EEE53039
Path Loss E8ponent and Standard eviation
(easred "or i""erent Bildings
&uildin! Fre'uenc( )MH*+ n )d&+
Retail Stores =' 22 ;9
7rocery Store =' '; 52
""ice. hard partition '500 30 90
""ice. so"t partition =00 2 =6
""ice. so"t partition '=00 26 ''
Factor( LOS
!e8tile>Che#ical '300 20 30
!e8tile>Che#ical 000 2' 90
Paper>Cereals '300 '; 60
(etalwor,ing '300 '6 5;
Sbrban )o#e
Che#ical 000 2' =9
(etalwor,ing '300 33 6;
8/18/2019 Radio Propagation.ppt
38/44
EEE5303;
8/18/2019 Radio Propagation.ppt
39/44
EEE5303=
Partition Losses
!here are two ,ind o" partition at the sa#e
"loor$ )ard partions$ the walls o" the roo#s
So"t partitions$ #oveable partitions that does notspan to the ceiling
!he path loss depends on the type o" the
partitions
8/18/2019 Radio Propagation.ppt
40/44
EEE5300
Partition Losses
Material $(pe Loss )d&+ Fre'uenc( )MH*+
ll #etal 26 ;'5
l#ini# Siding 20 ;'5
Concerete Bloc, 4all 3= '300
Loss "ro# one 1loor 20-30 '300
!rning an ngle in a Corridor '0-'5 '300
Concrete 1loor '0 '300
ry Plywood &3>in+ G ' sheet ' =600
4et Plywood &3>in+ G ' sheet '= =600
l#in# &'>;in+ G ' sheet 9 =600
verage signal loss #easre#ents reported by varios researches
"or radio paths obscrcted by so#e co##on bilding #aterial
8/18/2019 Radio Propagation.ppt
41/44
EEE530'
Partition Losses between 1loors
!he losses between "loors o" a bilding are
deter#ined by E8ternal di#ensions and #aterials o" the bilding
!ype o" constrction sed to create "loors E8ternal srrondings
J#ber o" windows
Presence o" tinting on windows
8/18/2019 Radio Propagation.ppt
42/44
EEE5302
Partition Losses between 1loors
&uildin! FF )d&+ )d&+
Office &uildin!
!hrogh ' 1loor '2= 90
!hrogh 2 1loors ';9 2;
!hrogh 3 1loors 2 '9
!hrogh 1loors 290 '5
Office &uildin! .
!hrogh ' 1loor '62 2=
!hrogh 2 1loors 295 5!hrogh 3 1loors 3'6 92
verage 1loor ttenation 1actor in dB "or ne. !wo. !hree and1or 1loors in !wo ""ice Bildings
8/18/2019 Radio Propagation.ppt
43/44
EEE5303
Signal Penetration
8/18/2019 Radio Propagation.ppt
44/44
Signal Penetration