ece6604 personal & mobile...
TRANSCRIPT
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ECE6604
PERSONAL & MOBILE COMMUNICATIONS
Prof./Dr. 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
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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
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Figure 1.6.6-1. Default Protocols 2
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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
USARTsSSCUSIFCamera
IFDisplay
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
Q
CLK
DAT
ENA
AFC
RF Control
26 MHz
Car Kit
Earpiece
Ringer
Headset
MU
X
0* #
321
8
54
7
SDC
MMC
6
9
Note: TEAKLite® is a registered trademark of ParthusCeva, Ltd.ARM® is a registered trademark of ARM, Ltd.
A p p l i c a t i o n sn E-GPRS/GPRS/GSM multimedia phones with tomorrow's
multimedia requirementsn Minimum space E-GPRS/GPRS data modules supporting up
to multislot class 12n WCDMA phone and data module applications (in
combination with a WCDMA co-processor)
K e y B e n e f i t sn High integration level of key multimedia features allowing for
minimum cost system solutions with the right feature setn Proven leading-edge modem technology with second
generation E-GPRS evolvementn Feature flexibility through upgrade options with multimedia
chips via standardized interfacen Connectivity to Bluetooth, FM Radio, WLAN, A-GPS and other
modules n Software compatibility to other members of the S-GOLD®
family
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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) 922-925/867-870
Carrier 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.
• 2010 — GSM is deployed in 219 countries, 4B 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)
• future — HSPA+ (UL: 11 Mbps, DL: 42 Mbps), LTE-A (UL: 50Mbps, DL: 100 Mbps), cdma2000 1xEV-DO Rev B (UL: 5.4 Mbps,DL: 14.7 Mbps)
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2G 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.– 2Q 2009: 494M CDMA2000 and 410M WCDMA subscribers
– 4B GSM and WCDMA subscribers
• LTE: OFDMA considered revolutionary by cellular operators. Widespreaddeployment is still some years away.
– 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)
– As of August 2009 there were 12 HSPA+ networks in the worldrunning at 21 Mbps (DL). More are expected.
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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 has a relatively slow start– 3.5M subscribers worldwide 400K WiMax and 50M 3G subscribers
added in 1Q 2009.
– Competing solutions:
∗ Digital Subscriber Line (DSL), Coax Cable Networks∗ Satellite DSL∗ 3G cellular with HSDPA/HSUPA or cdma2000 1X EVDO
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WIRELESS REGIONAL AREA NETWORKS (WRANs)
• IEEE 802.22 provides wide area radio access using Cognitive Radio– Coexistence in (6, 7, 8 MHz) unused DTV bands on a non-
interfering basis.
– Air interface is similar to IEEE802.16, but supports spectrumsensing and dynamic bandwidth management not found in IEEE802.16
• Essential elements include– Databases and spectrum sensing to detect incumbent signals
(DTV and wireless microphone).
– Dynamic spectrum management to transmit in unused DTVchannels.
– Transmit power control to limit interference.
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IEEE802 Family of Standards -Summary
• IEEE 801.11b/a/g/n is a success– Femtocells integrate WiFi with 3G cellular.
∗ Frees up cellular capacity and reduces BS power consumption.∗ Handheld power drain due to WLAN searching.∗ Fast WLAN-to-cellular handoff is needed.
• IEEE 802.16-2009 (sometimes branded as 4G) had a slow start– 3.5M subscribers worldwide
– 400K WiMax and 50M 3G subscribers added in 1Q 2009.
– Competing solutions ADSL, Satellite, Cable, 3G cellular,Licensed proprietary systems, Power line communications.
• IEEE 802.15 sees moderate success– Bluetooth widely deployed - no longer an IEEE 802.15 standard.
– Ultra Wideband Fullerton (Time Domain Systems) 1980s patents.
• IEEE 802.22 Wireless Regional Access Network - Cognitive Radio
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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.
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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
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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.
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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 .
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PROPAGATION OVER A FLAT SPECULAR SURFACE
d1
d2
BS
MS
d
hb
hm
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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 stations
hb = base station antenna height
hm = 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 =2π
λc(d2 − d1)
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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(2πλc∆d)
∣
∣
∣
2
= Ωt
(
λc
4πd
)2 ∣∣
∣
∣
1− cos(
2π
λc∆d
)
− j sin(
2π
λc∆d
)∣
∣
∣
∣
2
= Ωt
(
λc
4πd
)2 [
2− 2cos(
2π
λc∆d
)]
= 4Ωt
(
λc
4πd
)2
sin2(
π
λc∆d)
)
where ∆d = (d2 − d1).
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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
∆d ≈ d(
1+(hb + hm)
2
2d2
)
− d(
1+(hb − hm)2
2d2
)
=2hbhm
d.
• Finally, the received envelope power is
µΩp ≈ 4Ωt(
λc
4πd
)2
sin2(
2πhbhm
λcd
)
• Under the condition that d ≫ hbhm, the above reduces to
µΩp ≈ Ωt(
hbhm
d2
)2
where we have invoked the small angle approximation sin x ≈ x forsmall x.
• Propagation over a plane reflecting surface differs from free spacepropagation 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
)2
4 sin2(
2πhbhm
λcd
)
]−1
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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) 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.
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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.
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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).
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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 noise.– External noise sources include atmospheric noise (e.g, lightning
strikes), galactic noise, man made noise (e.g, automobile ignitionnoise).
– 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.
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Link Budget
• The link budget can be expressed in terms of the following param-eters:
Ωt = transmitted carrier power
GT = transmitter antenna gain
Lp = path loss
GR = receiver antenna gain
Ωp = received signal power
Ec = received energy per modulated symbol
To = receiving system noise temperature in degrees Kelvin
Bw = receiver noise equivalent bandwidth
No = white noise power spectral density
Rc = modulated symbol rate
k = 1.38× 10−23 = Boltzmann’s constantF = noise figure, typically about 3 dB
LRX = receiver implementation losses
LI = losses due to system load (interference)
Mshad = shadow margin
GHO = handoff gain
SRX = receiver sensitivity
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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)|2dfH2(0)
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• The effective received carrier power is
Ωp =ΩtGTGR
LRXLp.
• 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 =Ωp
N=
ΩtGTGR
kToBwFLRXLp.
• The carrier-to-noise ratio, Γ, and modulated symbol energy-to-noiseratio, Ec/No, are related as follows
Ec
No= Γ× Bw
Rc.
• Hence, we can rewrite the link budget asEc
No=
ΩtGTGR
kToRcFLRXLp.
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-
• Converting into decibel units givesEc/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 asSRX = LRXkToF (Ec/No)Rc
or converting to decibel units
SRX (dBm) = LRX (dB) + kTo(dBm/Hz) + F(dB) +Ec/No(dB) + Rc (dB Hz) .
• All parameters are usually fixed except for Ec/No. The receiver sen-sitivity (in dBm) is determined by the minimum acceptable Ec/No.
• Substituting the determined receiver sensitivity SRX (dBm) into (1) andsolving for Lp (dB) gives the maximum allowable path loss
Lmax (dB) = Ωt (dBm) +GT (dB) +GR (dB) − SRX (dBm) .
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