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ECE6604
PERSONAL & MOBILE COMMUNICATIONS
GORDON L. STÜBER
School of Electrical and Computer EngineeringGeorgia Institute
of TechnologyAtlanta, Georgia, 30332-0250
Ph: (404) 894-2923Fax: (404) 894-7883
E-mail: [email protected]:
http://www.ece.gatech.edu/users/stuber/6604
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TOPICAL OUTLINE
1. INTRODUCTION TO CELLULAR RADIO SYSTEMS
2. MULTIPATH-FADING CHANNEL MODELLING AND SIMULATION
3. SHADOWING AND PATH LOSS
4. CO-CHANNEL INTERFERENCE AND OUTAGE
5. SINGLE- AND MULTI-CARRIER MODULATION TECHNIQUESAND THEIR
POWER SPECTRUM
6. DIGITAL SIGNALING ON FLAT FADING CHANNELS
7. MULTI-ANTENNA TECHNIQUES
8. ADVANCED TOPICS
• MULTICARRIER TECHNIQUES• SPREAD SPECTRUM TECHNIQUES• CELLULAR
ARCHITECTURES AND RESOURCE MANAGE-
MENT
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ECE6604
PERSONAL & MOBILE COMMUNICATIONS
Week 1
Introduction,
Path Loss, Co-channel Interference, Link Budget
3
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WIRELESS INFRASTRUCTURE
1. Satellite Networks
2. Broadcast Networks
3. Cellular Telephony Systems
4. Paging Networks
5. Fixed Wireless Access Systems
6. Wireless Local Area Networks
7. Personal Area Networks
8. Sensor Networks
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Overview 3GPP2 C.S0024 Ver 4.0
Air LinkManagement
Protocol
OverheadMessagesProtocol
PacketConsolidation
Protocol
InitializationState Protocol
Idle StateProtocol
ConnectedState Protocol
Route UpdateProtocol
SessionManagement
Protocol
SessionConfiguration
Protocol
StreamProtocol
SignalingLink
Protocol
Radio LinkProtocol
SignalingNetworkProtocol
ControlChannel MAC
Protocol
Access ChannelMAC Protocol
Reverse TrafficChannel MAC
Protocol
Forward TrafficChannel MAC
Protocol
ConnectionLayer
SessionLayer
StreamLayer
ApplicationLayer
MACLayer
SecurityLayer
PhysicalLayer
SecurityProtocol
AuthenticationProtocol
EncryptionProtocol
Default PacketApplication
Default SignalingApplication
LocationUpdateProtocol
AddressManagement
Protocol
KeyExchangeProtocol
Physical LayerProtocol
FlowControlProtocol
1
Figure 1.6.6-1. Default Protocols 2
3
5
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P r o d u c t B r i e f
A p p l i c a t i o n E x a m p l e Q u a d - B a n d E G P R S
S o l u t i o n
Power BusPeripherals
I2CInterface
Power BusBaseband
I2C
AC-Adaptor
Charger
Pre-Charge
VBB2
VRTC
VBB1
VMemory
VBB USB
VBB Analog
VBB I/O Hi
VUSB Host
SM-POWER(PMB 6811)
Control
BB (LR)/Mem/CoproStep down 600 mA
On-chipReference
VBT BB
VRF3 (BT)
VRF Main
VRF VCXO
AmpVDD
LEDDriver
MotorDriver
M
NiMH/LiIonBattery
Power BusBluetooth
Power BusRF
S-GOLD2(PMB 8876)
DA
A
AD
D
I2S / DAII2S SSC
TEAKLite®
GPTU IR-Memory
GSMCipher Unit
RFControl
Speechand Channel
DecodingEqualizer
DA
AD
Speechand Channel
Encoding
8 PSK/GMSKModulator
DA
AD
SRAM
MOVE Copro
DMAC ICUKeypad
USB FSOTG
FastIrDA
MMC/SDIF
CAPCOM
GPTU
RTC
I2C
JTAG
AUXADC
SCCU
FCDP
EBU
GSMTimer
GEA-1/2/3 CGUAFC
GPIOs
ARM®926 EJ-SUSIM
USARTsSSCUSIF CameraIFDisplay
IF
Multimedia IC IF
FLASH/SDRAM
SMARTi DC+(PMB 6258) GSM 900/1800
GSM 850/1900
AtomaticOffset
Compensation
ControlLogic
SAMFast PLL
850
900
1800
1900
Rx/Tx
Multi ModePA
850900
18001900
I
QCLKDATENA
AFC
RF Control
26 MHz
Car Kit
Earpiece
Ringer
Headset
MUX
0* #
321
8
54
7
SDCMMC
6
9
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1G Cellular Technologies
• 1979 — Nippon Telephone and Telegraph (NTT) introduces
thefirst cellular system in Japan.
• 1981 — Nordic Mobile Telephone (NMT) 900 system introduced
byEricsson Radio Systems AB and deployed in Scandinavia.
• 1984 — Advanced Mobile Telephone Service (AMPS) introducedby
AT&T in North America.
Feature NTT NMT AMPSFrequency Band 925-940/870-885 890-915
824-849RL/FLa 915-918.5/860-863.5 917-950 869-894(MHz)
922-925/867-870Carrier Spacing 25/6.25 12.5b 30(kHz) 6.25
6.25Number of 600/2400 1999 832Channels 560
280Modulation analog FM analog FM analog FMaRL = reverse link,
FL = forward linkb frequency interleaving using overlapping
channels, where the channelspacing is half the nominal channel
bandwidth.
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2G Cellular Technologies
• 1990 — Interim Standard IS-54 (USDC) adopted by TIA.
• 1991 — Japanese Ministry of Posts and Telecommunications
stan-dardized Personal Digital Cellular (PDC)
• 1992 — Phase I GSM system is operational (September 1).
• 1993 — Interim Standard IS-95A (CDMA) adopted by TIA.
• 1994 — Interim Standard IS-136 adopted by TIA.
• 1998 — IS-95B standard is approved.
• 2011 — GSM is deployed in 219 countries, 5.2B subscribers,
covers80% of world population. IS-95A/B is deployed in 121
countries,IS-54/136 is extinct, PDC is nearly extinct.
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2G Cellular Technologies
Feature GSM/DCS1800/PCS1900 IS-54/136Frequency Band GSM:
890-915/ 824-829/RL/FLa 935-960 869/894(MHz) DCS1800: 1710-1785/
1930-1990/
1805-1880 1850-1910PCS1900: 1930-1990/1850-1910
Multiple Access F/TDMA F/TDMACarrier Spacing (kHz) 200
30Modulation GMSK π/4-DQPSKBaud Rate (kb/s) 270.833 48.6Frame Size
(ms) 4.615 40Slots/Frame 8/16 3/6Voice Coding (kb/s) VSELP(HR 6.5)
VSELP (FR 7.95)
RPE-LTP (FR 13) ACELP (EFR 7.4)ACELP (EFR 12.2) ACELP (12.2)
Channel Coding Rate-1/2 CC rate-1/2 CCFrequency Hopping yes
noHandoff hard hard
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2G Cellular Technologies
Feature PDC IS-95Frequency Band 810-826/ 824-829/RL/FLa 940-956
869-894(MHz) 1429-1453/ 1930-1990/
1477-1501 1850-1910Multiple Access F/TDMA F/CDMACarrier Spacing
(kHz) 25 1250Modulation π/4-DQPSK QPSKBaud Rate (kb/s) 42 1228.8
Mchips/sFrame Size (ms) 20 20Slots/Frame 3/6 1Voice Coding (kb/s)
PSI-CELP (HR 3.45) QCELP (8,4,2,1)
VSELP (FR 6.7) RCELP (EVRC)Channel Coding rate-1/2 BCH FL:
rate-1/2 CC
RL: rate-1/3 CCFrequency Hopping no N/AHandoff hard soft
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3G Cellular Technologies
• 1998 — A group called 3GPP (Third Generation Partnership
Project)is created to] produce a common 3G standard based on
WCDMA.
• 1999 — The group 3GPP2 is created to harmonize the use of
multi-carrier cdma2000
• 2000 — South-Korean Telecom (SKT) launches cdma2000-1X
net-work (DL/UL: 153 kbps)
• 2001 — NTT DoCoMo deploys commercial UMTS network in Japan
• 2002 — cdma2000 1xEV-DO (UL: 153 kbps, DL: 2.4 Mb/s)
• 2003 — WCDMA (UL/DL: 384 kbps)
• 2006 — HSDPA (UL: 384 kbps, DL: 7.2 Mbps)
• 2007 — cdma2000 1xEV-DO Rev A (UL: 1.8 Mbps, DL: 3.1 Mbps)
• 2010 — HSDPA/HSUPA (UL: 5.8 Mbps, DL: 14.0 Mbps),
cdma20001xEV-DO Rev A (UL: 1.8 Mbps, DL: 3.1 Mbps)
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• 2011 — 1 in 4 HSPA networks have HSPA+ (UL: 11 Mbps, DL:42
Mbps), LTE is currently deployed by 16 carriers with 57
moredeployments committed
• future — LTE-A (UL: 50 Mbps, DL: 100 Mbps), cdma2000 1xEV-DO
Rev B (UL: 5.4 Mbps, DL: 14.7 Mbps)
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3G Cellular Technologies
Feature W-CDMA cdma2000Multiple Access DS-CDMA DS-CDMAChip Rate
(Mcps) 3.84 1.2288Carrier Spacing (MHz) 5 1.25Frame Length (ms) 10
5/20Modulation FL: QPSK FL: BPSK/QPSK
RL: BPSK RL: BPSK64-ary orthogonal
Coding rate-1/2, 1/3 rate-1/2, 1/3, 1/4,K = 9 conv. code 1/6 K =
9 conv. coderate-1/3 rate-1/2, 1/3, 1/4,K = 4 turbo code 1/5, K = 4
turbo code
Interleaving inter/intraframe intraframeSpreading FL: BPSK
complex
RL: QPSKInter BS asynchronous synchronoussynchronization
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3G & 4G Cellular Technologies
• Cellular operators are heavily invested in 3G
infrastructures.– 1Q 2011: 5.2B GSM and 577 cdmaOne subscribers;
575M
CDMA2000 and 717M WCDMA subscribers
• LTE: Currently seeing some deployment (700 MHz band in
NorthAmerica), sometimes branded as 4G but does not meet 4G
require-ments.
– Develop LTE-A (4G) in parallel with evolved 3G.
• Evolved HSPA (HSPA+) is evolutionary– Can achieve the data
rates as LTE-A in 5 MHz with HSPA+
∗ Receiver diversity∗ Equalization and Interference
cancellation∗ MIMO (2 x 2)∗ High-order signal constellations (64
QAM)
– In August 2009 there were 12 HSPA+ networks in the
worldrunning at 21 Mbps (DL). Today 1 out of 4 HSPA networkshave
HSPA+ in commercial operation.
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WIRELESS LANs (WiFi)
• IEEE 802.11 – Direct Sequence Spread Spectrum (1-and-2
Mb/s,2.4GHz)
• IEEE 802.11b – Complimentary Code Keying (CCK)
(5.5-and-11Mb/s, 2.4GHz)
• IEEE 802.11g/a – Orthogonal Frequency Division Multiplexing
(OFDM)(6-to-54 Mb/s, 2.4/5GHz)
• IEEE 802.11e – MAC enhancements for Quality of Service
(QoS)
• IEEE 802.11i – Security
• IEEE 802.11n – MIMO physical layer
• Femtocells: integrate WiFi with cellular.– Benefit: Frees up
cellular capacity and reduces BS power con-
sumption.
– Drawback: MS power drain due to WLAN searching.
– Drawback Fast WLAN-to-cellular handoff is needed to
preventdropped calls.
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WIRELESS PANs
• IEEE Std 802.15.1-2002 - 1Mb/s WPAN/Bluetooth v1.x
derivativework - uses frequency hop spread spectrum.
– Today Bluetooth is managed by the Bluetooth Special
InterestGroup.
• P802.15.2- Recommended Practice for Coexistence in
UnlicensedBands
• P802.15.3 - 20+ Mb/s High Rate WPAN for Multimedia and
DigitalImaging
• P802.15.3a - 110+ Mb/s Higher Rate Alternative PHY for
802.15.3- Ultra wideband (UWB)
• P802.15.4 - 200 kb/s max for interactive toys, sensor and
automa-tion needs
• Applications include (mobile) ad hoc networks, sensor
networks
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WIRELESS MANs (WiMax)
• IEEE 802.16 addresses the ”first-mile/last-mile” connection in
wire-less MANs.
– focuses on the efficient use of bandwidth between 10 and 66
GHz(the 2 to 11 GHz region with PMP and optional Mesh
topologies)
– defines a medium access control (MAC) layer that supports
mul-tiple physical layer specifications customized for the
frequencyband of use.
• IEEE 802.16e - mobility extension of IEEE802.16.
• IEEE802.16-2009 had a relatively slow start - 250 trials and
networkstoday.
– 17.25M subscribers worldwide in 1Q 2011; 400K WiMax and50M 3G
subscribers added in 1Q 2009.
– Competing solutions:
∗ Digital Subscriber Line (DSL), Coax Cable Networks∗ Satellite
DSL∗ 3G cellular with HSPA+ or cdma2000 1X EV-DO Rev A
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FREQUENCY RE-USE AND THE CELLULAR
CONCEPT
CD
B
A
4-Cell
C
AB
3-Cell 7-Cell
A
C
F
D
GE
B
Commonly used hexagonal cellular reuse clusters.
• Tessellating hexagonal cluster sizes, N, satisfyN = i2 + ij +
j2
where i, j are non-negative integers and i ≥ j.– hence N = 1, 3,
4, 7, 9, 12, . . .
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B
G
F
G
D
B
C
G
A
F
B
G
D
E
C
A
E
C
A
F
B
A
F
G
D
D
E
C
A
F
G
B
Cellular layout using seven-cell reuse clusters.
• Real cells are not hexagonal.
• Frequency reuse introduces co-channel interference and
adjacentchannel interference.
18
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CO-CHANNEL REUSE FACTOR
A
AD
R
Frequency reuse distance for 7-cell clusters.
• For hexagonal cells, the co-channel reuse factor isD
R=
√3N
19
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RADIO PROPAGATION MECHANISMS
• Radio propagation is by three mechanisms– Reflections off
objects larger than a wavelength
– Diffraction around the edges of objects
– Scattering by objects smaller than a wavelength
• A mobile radio environment is characterized by three nearly
inde-pendent propagation factors
– Path loss attenuation with distance.
– Shadowing caused by large obstructions such as buildings,
hillsand valleys.
– Multipath-fading caused by the combination of multipath
propa-gation and transmitter and/or receiver movement.
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FREE SPACE PATH LOSS (FSPL)
• Equation for free-space path loss is
LFS =
(4πd
λc
)2.
and encapsulates two effects.
1. The first effect says that spreading out of electromagnetic
energyin free space is determined by the inverse square law,
i.e.
Ωr(d) = Ωt1
4πd2,
where
– Ωt is the total transmit power
– Ωr(d) is the received power per unit area or power spatial
den-sity (in watts per meter-squared) at distance d. Note that
thisterm is not frequency dependent.
21
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FREE SPACE PATH LOSS (FSPL)
• Second effect2. The second effect is due to aperture, which
determines how well
an antenna picks up power from an incoming electromagneticwave.
For an isotropic antenna, we have
Ωp(d) = Ωr(d)λ2c4π
,
where Ωp(d) is the received power. Note that this is entirely
de-pendent on wavelength, λc, which is how the
frequency-dependentbehavior arises.
• For free space propagation the path loss is
LFS (dB) =Ωt
Ωp(d)= 10log10
{(4πd
λc
)2}
= 10log10
{(4πd
c/fc
)2}
= 20log10fc +20log10d− 147.55 dB .
22
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PROPAGATION OVER A FLAT SPECULAR SURFACE
d1
d2
BS
MS
d
hbhm
1
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• The length of the direct path is
d1 =√
d2 + (hb − hm)2
and the length of the reflected path is
d2 =√
d2 + (hb + hm)2
d = distance between mobile and base stationshb = base station
antenna heighthm = mobile station antenna height
• Given that d � hbhm, we have d1 ≈ d and d2 ≈ d.
• However, since the wavelength is small, the direct and
reflectedpaths may add constructively or destructively over small
distances.The carrier phase difference between the direct and
reflected pathsis
φ2 − φ1 = 2πλc
(d2 − d1)
2
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• Taking into account the phase difference, the received signal
poweris
μΩp = Ωt
(λc
4πd
)2 ∣∣∣1+ ae−jbej(φ2−φ1)∣∣∣2 ,where a and b are the amplitude
attenuation and phase change in-troduced by the flat reflecting
surface.
• If we assume a perfect specular reflection, then a = 1 and b =
π forsmall θ. Then
μΩp = Ωt
(λc
4πd
)2 ∣∣∣1− ej(2πλcΔd)∣∣∣2= Ωt
(λc
4πd
)2 ∣∣∣∣1− cos(2π
λcΔd
)− j sin
(2π
λcΔd
)∣∣∣∣2
= Ωt
(λc
4πd
)2 [2− 2cos
(2π
λcΔd
)]
= 4Ωt
(λc
4πd
)2sin2
(π
λcΔd)
)where Δd = (d2 − d1).
3
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• Given that d � hb and d � hm, and applying the
approximation√1+ x ≈ 1+ x/2 for small x, we have
Δd ≈ d(1+
(hb + hm)2
2d2
)− d
(1+
(hb − hm)22d2
)=
2hbhmd
.
• Finally, the received envelope power is
μΩp ≈ 4Ωt(
λc
4πd
)2sin2
(2πhbhm
λcd
)
• Under the condition that d � hbhm, the above reduces to
μΩp ≈ Ωt(hbhm
d2
)2where we have invoked the small angle approximation sin x ≈ x
forsmall x.
• Propagation over a flat specular surface differs from free
space prop-agation in two respects
– it is not frequency dependent
– signal strength decays with the with the fourth power of
thedistance, rather than the square of the distance.
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10 100 1000 10000Path Length, d (m)
10
100
1000
Path
Los
s (d
B)
Propagation path loss Lp (dB) with distance over a flat
reflecting surface;hb = 7.5 m, hm = 1.5 m, fc = 1800 MHz.
LFL =
[(λc
4πd
)24 sin2
(2πhbhm
λcd
)]−1
5
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• In reality, the earth’s surface is curved and rough, and the
signalstrength typically decays with the inverse β power of the
distance,and the received power at distance d is
μΩp(d) =μΩp(do)
(d/do)β
where μΩp(do) is the received power at a reference distance
do.
• Expressed in units of dBm, the received power isμΩp (dBm)(d) =
μΩp (dBm)(do)− 10β log10(d/do) (dBm)
• β is called the path loss exponent. Typical values of μΩp
(dBm)(do) andβ are have been determined by empirical measurements
for a varietyof areas
Terrain μΩp (dBm)(do = 1.6 km) β
Free Space -45 2Open Area -49 4.35North American Suburban -61.7
3.84North American Urban (Philadelphia) -70 3.68North American
Urban (Newark) -64 4.31Japanese Urban (Tokyo) -84 3.05
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Co-channel Interference
Worst case co-channel interference on the forward channel.
7
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Worst Case Co-Channel Interference
• For N = 7, there are six first-tier co-channel BSs, located at
dis-tances {√13R,4R,√19R,5R,√28R,√31R} from the MS.
• Assuming that the BS antennas are all the same height and all
BSstransmit with the same power, the worst case
carrier-to-interferenceratio, Λ, is
Λ =R−β
(√13R)−β + (4R)−β + (
√19R)−β + (5R)−β + (
√28R)−β + (
√31R)−β
=1
(√13)−β + (4)−β + (
√19)−β + (5)−β + (
√28)−β + (
√31)−β
.
• With a path loss exponent β = 3.5, the worst case Λ is
Λ(dB) =
⎧⎨⎩
14.56 dB for N = 79.98 dB for N = 47.33 dB for N = 3
.
– Shadows will introduce variations in the worst case Λ.
8
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Cell Sectoring
Worst case co-channel interference on the forward channel with
120o cellsectoring.
9
-
• 120o cell sectoring reduces the number of co-channel base
stationsfrom six to two. For N = 7, the two first tier interferers
are locatedat distances
√19R,
√28R from the MS.
• The carrier-to-interference ratio becomes
Λ =R−β
(√19R)−β + (
√28R)−β
=1
(√19)−β + (
√28)−β
.
• Hence
Λ(dB) =
⎧⎨⎩
20.60 dB for N = 717.69 dB for N = 413.52 dB for N = 3
.
• For N = 7, 120o cell sectoring yields a 6.04 dB C/I
improvementover omni-cells.
• The minimum allowable cluster size is determined by the
thresholdΛ, Λth, of the radio receiver. For example, if the radio
receiver hasΛth = 15.0 dB, then a 4/12 reuse cluster can be used
(4/12 means4 cells or 12 sectors per cluster).
10
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Receiver Sensitivity
• Receiver sensitivity refers to the ability of the receiver to
detectradio signals. We would like our radio receivers to be as
sensitive aspossible.
• Radio receivers must detect radio waves in the presence of
noiseand interference.
– External noise sources include atmospheric noise (e.g,
lightningstrikes), galactic noise, man made noise (e.g, automobile
ignitionnoise), co-channel and adjacent channel interference.
– Internal noise sources include thermal noise.
• The ratio of the desired signal power to thermal noise power
beforedetection is commonly called the carrier-to-noise ratio,
Γ.
• The parameter Γ is a function of the communication link
parametersincluding transmitted power (or effective isotropic
radiated power(EIRP)), path loss, receiver antenna gain, and the
effective input-noise temperature of the receiving system.
• The formula that relates the link parameters to Γ is called
the linkbudget.
11
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Link Budget
• The link budget can be expressed in terms of the following
param-eters:
Ωt = transmitted carrier powerGT = transmitter antenna gainLp =
path lossGR = receiver antenna gainΩp = received signal powerEs =
received energy per modulated symbolTo = receiving system noise
temperature in degrees KelvinBw = receiver noise equivalent
bandwidthNo = white noise power spectral densityRc = modulated
symbol ratek = 1.38× 10−23 = Boltzmann’s constantF = noise figure,
typically about 3 dB
LRX = receiver implementation lossesLI = losses due to system
load (interference)
Mshad = shadow marginGHO = handoff gainΩth = receiver
sensitivity
12
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Noise Equivalent Bandwidth, Bw
• Consider an arbitrary filter with transfer function H(f).
• If the input to the filter is a white noise process with power
spectraldensity No/2 watts/Hz, then the noise power at the output
of thefilter is
Nout =No
2
∫ ∞−∞
|H(f)|2df
= No
∫ ∞0
|H(f)|2df
• Next suppose that the same white noise process is applied to
anideal low-pass filter with bandwidth Bw and d.c. response H(0).
Thenoise at the output of the filter is
Nout = NoBwH2(0)
• Equating the above two equations give the noise equivalent
bandwdith
Bw =
∫∞0 |H(f)|2df
H2(0)
13
-
• The effective received carrier power is
Ωp =ΩtGTGRLRXLp
.
• The total input noise power to the detector isN = kToBwF
• Very often the following kTo value at room temperature of 17
oC(290 oK) is used kTo = −174 dBm/Hz,
• The received carrier-to-noise ratio defines the link
budget
Γ =ΩpN
=ΩtGTGR
kToBwFLRXLp.
• The carrier-to-noise ratio, Γ, and modulated symbol
energy-to-noiseratio, Es/No, are related as follows
Es
No= Γ× Bw
Rc.
• Hence, we can rewrite the link budget asEs
No=
ΩtGTGRkToRcFLRXLp
.
14
-
• Converting into decibel units givesEs/No(dB) = Ωt (dBm) +GT
(dB) +GR (dB) (1)
−kTo(dBm)/Hz −Rc (dB Hz) − F(dB) − LRX (dB) − Lp (dB) .
• The receiver sensitivity is defined asΩth = LRXkToF
(Es/No)Rc
or converting to decibel units
Ωth (dBm) = LRX (dB) + kTo(dBm/Hz) + F(dB) + Es/No(dB) +Rc (dB
Hz) .
• All parameters are usually fixed except for Es/No. The
receiver sen-sitivity (in dBm) is determined by the minimum
acceptable Es/No.
• Substituting the determined receiver sensitivity Ωth (dBm)
into (1) andsolving for Lp (dB) gives the maximum allowable path
loss
Lmax (dB) = Ωt (dBm) +GT (dB) +GR (dB) −Ωth (dBm) .
15