UMTS Radio Planning : Fundamentals UMTS Standards : Brief Historical Overview on 3GPP, IMT2000, etc. Mathematical background of SS-CDMA Systems Multiple Access Spread Spectrum Modulation Properties of Spread Spectrum System Tolerance of Narrow-band interference DS-Spread Spectrum Modulation Example Processing Gain in BPSK DS-SS Systems Tolerance to Wide-Band interference WCDMA in Cellular Radio Networks Multipath Environment characteristics Soft, Softer, and Hard Handover Power Control : Inner-loop, outer-loop, etc. WCDMA Load Equation : Definition of Eb/No
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UMTS Radio Planning : Fundamentals UMTS Standards : Brief Historical Overview on 3GPP, IMT2000, etc. Mathematical background of SS-CDMA Systems
Multiple Access Spread Spectrum Modulation Properties of Spread Spectrum System Tolerance of Narrow-band interference
DS-Spread Spectrum Modulation Example Processing Gain in BPSK DS-SS Systems Tolerance to Wide-Band interference
WCDMA in Cellular Radio Networks Multipath Environment characteristics Soft, Softer, and Hard Handover Power Control : Inner-loop, outer-loop, etc. WCDMA Load Equation : Definition of Eb/No
UMTS RF Fundamentals
Dr. Hatem MOKHTARI
UMTS Radio Planning : Dimensioning UMTS System Dimensioning
General Guidelines Dimensioning Workflow Link budget Parameters
Eb/No for different Multipath Radio Propagation Channels Load Factor Bit Rates as defined in the ETSI Recommendations WCDMA Spectral Efficiency (throughputs in kbps per carrier per cell) Orthogonality HO Gains BTS Static Sensitivity : TMA, Antenna Gain, Sectorization Gain,
SOHO Overhead, Signaling Overhead, Link budgets and Coverage Efficiency of WCDMA
Cell Ranges Selection Process Dimensioning Guidelines
Guidelines for Traffic-per-cell computation
UMTS Radio Planning : Dimensioning Dimensioning Rules
UMTS Radio Planning : Site Consideration Interference Checking :Per Environment basis Background noise interference notion Site clearance and roof-top selection UMTS/UMTS and UMTS/GSM co-location issues from RF standpoint Site-sharing : Practical guidelines Results of Isolation measurements between antennas in collocation in
the UMTS frequency band : Vertical Polarization results Dual Polarization results Conclusions
CDMA Fundamentals W/R : Defined as the system processing gain
In CDMA, the Reverse Link Capacity is often the limiting link in terms of capacity
In CDMA : Uplink Receive Power is equal from all MSs. Per user : S/N = 1/(M-1) M : Total Number of users in the cell S = S (The wanted signal) N = (M-1)S => S/N = 1/(M-1) Example : If M=7 then S/N = 1/7
if M>>1 then
M : The Number of simultaneous users a CDMA cell can supporto
b
NERW
M
CDMA Multiple Access : Principal of Spread Spectrum (SS)
Each User encodes its signal Code Signal Bandwidth (W) > Information Bandwidth
The Receiver knows the code sequence
Transmission
Spread Spectrum
f f
f
P
f
Reception
Despreading
CDMA Multiple Access : Principal of Spread Spectrum (SS)
Eb = Signal Power / Bit Rate = S/Rb
No = Noiser Power / Bandwidth = N/W bo
b
RW
NS
NE
Signal to Noise Ratio
Processing Gain
Example :Given a Demodulator Performance
Bit rate Rb = 8 kpbsBandwidth W = 1.2 Mbps => G = W/Rb = 150 = 21 dB
dBNE
o
b 6
dBdBdBRW
NE
NS
dBbdBo
b
dB
15216
CDMA Multiple Access PrincipleShannon Theorem
NSWC 1log2
Channel Capacity C (Bit/s) given by Shannon Theorem :
W : System Bandwidth (Hz)S/N : Signal to Noise Ratio (numerical value)C : System Capacity (bit/s)
Same Capacity
Wide W and Low S/N (such as in WCDMA)
Narrow W and Large S/N (such as in GSM)
CDMA Multiple Access Advantages : Multiple Access Features
1. All Users’ Signals overlap in TIME and FREQUENCY2. Correlating the Received Signal despreads ONLY the WANTED SIGNAL
Correlation Narrowband Interference Spread the power
CDMA Principles
Radio PropagationChannel
D/AA
A
B1
B2
m1(t)
m2(t)
c1(t)
c2(t)
c1(t)
c2(t)
c1(t) and c2(t) are Orthogonal Codes : 0)()(0
21 T
dttctc
m’1(t)
D/A
m’2(t)
Transmitter Receiver
CDMA Principles Cross-Correlation Rxy() :
Cross-correlation if =0 :
If x and y are discrete sequence (binary signals):
Example of orthogonal codes :
T
xy dttytxR0
)()()(
T
xy dttytxR0
)()()0(
iIii
T yxYXRxy
1
.)0(
1111
X
1111
Y 01111
1111
.1111)0(
xyR
CDMA Principles To be used in DS-SS CDMA Codes must satisfy the
following conditions : Zero Cross-correlation Number of +1s and -1s must be the same Dot Product must be equal to 1
Example : Dot product of the previous example is :
14/)1111(4/. XX T
CDMA Principlesm1(t)
Tb 2Tb
1 -1 1
3Tb
f
M1(f)
1/Tb
Tc 4Tc
f
C1(f)
1/Tb
c1(t)
1/Tc
Tc : Chip Rate of the PN CodeTb : Information rate (voice/data)
f
C1(f)* M1(f)
1/Tb 1/Tc
m1(t).c1(t)
CDMA Principles
/2Mobile
distance
Am
plitu
de
The MS crosses 2 fades in v2
Example : @ 900 MHz and v = 90 km/h (25 m/s)MS crosses fades every 6.67 ms
@ 1800 MHz MS crosses fades every 3.335 ms
CDMA Principles : Delay Spread
t
Received Power
Time (s)
1= 3s2= 4s
3
Inter Symbol Interference can occur if the delay spread n is greater than
one symbol period : The higher the bit rate, the more ISI occur
Example 1: Let us consider a Mobile Communications System that uses Rb = 270.83 kbps The bit period is thus Tb = 1/270830 = 3.69 s Conclusion : bit period almost equal to 4 s as shown on the delay spread
power profile => ISI would normally exist ! Without use of EQUALIZER
Example 2: Let us consider a Mobile Communications System that uses Rb = 1.2288 Mbps
= 1228800 bps The bit period is thus Tb = 1/ 1228800 = 1 s Conclusion : bit period is much LESS than 4 s as shown on the delay spread
power profile => ISI would normally exist ! Important note : CDMA Rake Receive uses a special form of Time Diversity to
recover the signal. CDMA Rake receiver combines multipath components and suppresses phase differences provided that delays are not very small
CDMA Principles : Delay Spread
The Principal of Maximum Ratio Combining in CDMA Rake Receiver
Transmitted Symbol- Amplitude- Phase
Received Signalat each time delay
Modified SignalUsing Channel Estimator
CombinedSymbol
Figure #1
Figure #2
Figure #3
Block Diagram of CDMA Rake ReceiverCorrelator Phase
RotatorDelay
Equalizer
CodeGenerator
ChannelEstimator Finger # 1
Matched Filter
I
Q
I
Q
Correlator Phase Rotator
DelayEqualizer
CodeGenerator
ChannelEstimator Finger # 2
Correlator Phase Rotator
DelayEqualizer
CodeGenerator
ChannelEstimator Finger # 3
Combiner
Timing (finger allocation)
Input RF SignalQ
I
Digitized input samples are received from RF Front-end in the form of I and Q components
Code Generator and Correlator : Perform despreading and integration to user data symbol
Channel estimator : Uses the Pilot symbols to estimate the channel state
Phase Rotator : aligns the symbols to the initial phase (phase cancellation)
Delay Equalizer : Compensates the Delay in the arrival times of the symbols in each finger
Rake Combiner : Sums up the channel-compensated symbols, thereby providing MULTIPATH DIVERSITY against Fading.
Matched Filter : Determines and Updates the Current Multipath Delay Spread. This is used to assign the Rake fingers to the largest Peaks (Maximum Combining)
CDMA Rake Receiver : Components
CDMA Principles: Delay Spread In Multipath Environment :
Received power can be written as :
Fourier Transfer Function :
N
n
N
nnnnn fjafSfRtsatr
1 1
).2exp()()()()(
N
n
fjn
neafSfRfH
1
.2
)()()(
CDMA Principles : Delay Spread
f
H(f
)
Example with two-equal amplitude paths : a1=a2=A
2A
21
1
23
2
)cos(2)( ffH
1. Frequency-Selective Fading is evident in the nulls of the Magnitude Spectrum
2. WCDMA is more advantageous than CDMA when the delays are small such as 0.4 s (Dense Urban and Urban Environments)
3. WCMA using 5 Mbps (bit period of 0.2 s) better than IS-95 CDMA using only 1.2288 Mbsp (bit period 1 s) when ISI are to be considered in Dense Urban areas
11..
11
RW
MNE
o
b
CDMA FundamentalsIf other users from other cells are considered, the actual cell becomes loaded and :
where is the loading factor (0 < < 1)We define F as the Frequency reuse :
11F
CDMA Fundamentals
Cell B
Cell A
Cell C
B1
B2
C1
C2
Interference Introduced by Users in the Neighboring Cells
CDMA Fundamentals
Cell B
Cell A
Cell C
Sectorization Reduces Interference and addsa Gain to the system : Sectorization Gain
Unwanted interferersrejected by antennapattern of Cell A
Sectorization Gain :
Tri-Sectors : = 3 (2.5 in practice)
6-Sectors : = 6 (5 in practice)
Sectorization Gain = = Total Interfering Power from all Directions/ Perceived Interference Power by the sector antenna. G is the antenna pattern in given direction
CDMA Fundamentals
2
0
2
0
)()0()(
)(
dIGG
dI
Voice Activity Factor : Interference is reduced when the user is not transmitting
The final value for M :
CDMA Fundamentals
vRW
MNE
o
b 1..1
1..1
1
vNERW
M
o
b
.1
1.
UMTS Standards : Brief Historical Overview
ITU has advanced 3G Telecoms Standards The European Standard : IMT2000 for International
Mobile Telecommunications in year 2000 or UMTS The Northern American Standard is CDMA2000 Features :
Adds Multi-media capabilities to 2G standards (GSM, IS-136, IS-95, etc.)
Support for higher data rates Packet data networking IP Access
3G Standard Proposals WCDMA (up to 20 MHz bandwidth)
Rake Reception possible in both UL and DL CDMA IS-95 is 1.25 MHz of bandwidth
Dedicated Pilot Channels associated with each dedicated data channels intended for adaptive antenna techniques, interference
cancellation, coherent demodulation Variable rate transmission for the data channels Forward Link spreading uses Orthogonal variable spreading factor
(OVSF) codes Asynchronous cell specific signature sequences (UL)
3G in Europe : 3G ETSI will be dual-mode GSM/WCDMA 3G in USA : Smoother migration from IS-95 to CDMA2000
UMTS Standards : Brief Historical Overview
IMT2000 formerly FPLMTS (Future Public Land Mobile Telecommunications System)
World-wide Roaming Small, Low-cost pocket terminals High rate data services Advanced Multimedia services : interactivity Data Services Delivery :
TDD Unpaired bands : 1900 – 1920 MHz and 2010 – 2025 MHz for TDD CDMA systems
IMT2000 Frequency Allocation for UMTS
IMT2000 Frequency Allocation for UMTS
MSSUL
MSSDL
TDDUL/DL
TDDUL/DL
1900 1920 1980 2010 2025 2110 2170 2200
FDDUL
FDDDL
FDL
FUL
FDD Mode TDD Mode
FDL/UL
Radio Access : GSM vs UTRA and TDD vs FDD
Frequency
Time
Power / Code
UTRA/FDD
5 MHz
16 Timeslots per frame : 10 ms
UTRA/TDD
5 MHz625 s
0.2 MHz 577 s
GSM
W-CDMA Air Interface
W-CDMA = Frame structure of 72 frames
1 frame = 15 Time slots corresponding to one Power Control period (or a rate of 1500 Hz)
The Slot structure UPLINK is different from the DOWNLINK
Each Link comprises a Data Channel = DPDCH and a Control Channel = DPCCH
UMTS Frame Structure10 ms (one frame)
S1 S2 Si S15
DATADPDCH
PILOT TFI FBI TPCDPCCH
TFI : Transport Format combination IndicatorFBI : FeedBack InformationTPC = Transmit Power Control
Spreading and Modulation : Uplink
X
X
IQMUX
I
Q
X
Cd
DPDCH
DPCCH
Cc
Cscramble
To QPSK Modulator
Example of UMTS Spectrum Allocation : United Kingdom
One licence reserved for a new Operator 2*15 MHz paired spectrum + 5 MHz of unpaired spectrum (for TDD component)
One licence for 2*15 MHz paired spectrum
Three licences for 2*10 MHz paired spectrum + 5 MHz of unpaired spectrum
UMTS Radio Planning : Maximum Bit Rates Rural Outdoor :
384 kbps has been evaluated Up to 500 km/h is supported (SMG2 Q&A Workshop)
Suburban Outdoor : 384 kbps at the required velocity
Indoor and low-range outdoor : 2048 kbps
Range of bit rates : 100 bps to 2048 kbps with a granularity of 100 bps
Note :Transmitted bit rate can change during a call on a 10ms (frame) basis for efficient spectrum usage, i.e. variable rate due to nature of speech
UMTS Parameters for UDD Services in DL
SourceRate
64 kbps 144 kbps 384 kbps 2048 kbps
Informationbit rate
30.4 kbps 60.8 kbps 243.2kbps
486.4kbps
PhysicalChannelRate
64 kbps 128 kbps 512 kbps 1024 kbps
AntennaReceiverDiversity
ON ON ON ON
Radio Access Network Planning WCDMA System operates with a frequency reuse of 1
Common Radio Resource in WCDMA for all users is Power
WCDMA Supports different bearer services
Bearer Services characterized by : Bit Rate, Delay and BER
Different Settings for different Services
No need need for planning of code or code phase
Asynchronous Operation : No need for inter-base synchronization
UMTS System Characteristics W-CDMA : 5 MHz or more can be offered Carrier Spacing : multiples of 200 kHz W-CDMA spreading rate = 3.84 Mchip/s Information bit rate = between 8 kbit/s and 2 Mbit/s
78-189 kbps/MHz/Cell depending on type of propagation and mobile speed. Numbers are higher than in GSM
Connection Oriented Service (384 kbps @BER=10-6) at 120 km/h : 85-250 kbps/MHz/Cell depending on antenna diversity
Packet Service (384 kbps) in pedestrian environments : 470 to 565 kbps/MHz/cell, UL and DL respectively
Packet Service (2048 kbps) in Indoor environments : 230 to 500 kbps/MHz/cell, depending on DL antenna diversity
Coverage and Capacity in UMTS Trade-off between Capacity and coverage
Lower Capacity means a larger cell
New Cells can be inserted to facilitate capacity expansion as no frequency re-planning is needed
Extend coverage in case od asymmetric data traffic (more DL than UL) as UL is limited by MS power and interference is less
Simplified UMTS Network Architecture
IurIubi
sGb
IuCS
IuPSIubis
Abis
RNC
RNC
Node B
Node B
Node B
SGSN
BSCBTS
BTS
MSC
AbisA
Iubis IuPS
PCUTRAU
Ater
UMTS RNS
GSM BSS
UMTS Radio Network Planning : Dimensioning WCDMA Network dimensioning uses the following
inputs : Coverage :
RF Propagation Environments (urban, suburban, rural) Area Type information (Clutter, terrain shape, etc.) Coverage Regions : need for Marketing input
Capacity : Traffic Density Data Available Spectrum Subscriber Profile and Growth forecast
QoS : Coverage Probability (Area) Outage/Blocking Probability End User Requirements : Throughput, speed, etc.
Dimensioning involves : Radio Link Budget Analyses Coverage Analyses Required Capacity Estimation Cell-count estimation in terms of number of sites
required Number of RNCs (Radio Network Controller)
required Equipment at different Interfaces Core Network Elements : Circuit Switched and
Packet Switched Domain Core Networks
UMTS Radio Network Planning : Dimensioning
Three Main additional Link Budget Parameters have to be considered when designing UMTS Networks :
Interference Margin : Due to the Loading of the cell from MSs that are in other cells. The higher
the loading allowed, the larger interference margin to be added. Between 20 to 50 % require 1 to 3 dB of interference margin, respectively.
Fast Fading (=PC headroom) : Slow-moving pedestrian mobiles need fast power control to compensate the
fast fading (2 to 5 dB are needed). No Fast Fading Margin is required for high speed mobiles because no Fast Power control is able to compensate for Fast moving mobiles.
SOHO Gain (or SOft HO) : SOHO is a kind of Reception Diversity, which brings an additional gain to the
UMTS System. Generally called : MACRO DIVERSITY COMBINING (2 to 3 dB)
UMTS Radio Network Planning : Link Budget
Assumptions for the MS : Speech Terminal
Maximum Transmit Power = 21 dBm Antenna Gain = 0 dBi Body Loss = 3 dB
Data Terminal Maximum Transmit Power = 24 dBm Antenna Gain = 2 dBi Body Loss = 0 dB
Note : No body loss for Data Terminal as the MS is used away from the body for Fax, Internet, etc…unlike the Speech terminal where the body effect is straightforward ! Antenna gain is also affected by the body effect, which justifies the 0 dBi for Speech Terminals …
UMTS Radio Network Planning : Link Budget
Assumptions for the Base Station :
Noise Figure = 5 dB (without TMA of course !)
Antenna Gain = 18 dBi (tri-sector BS)
Eb/No requirement : 12.2 kbps Speech = 5 dB 144 kbps Real-Time Data = 1.5 dB 384 kbps non-Real-Time Data = 1 dB
Cable Loss = 3 dB
UMTS Radio Network Planning : Link Budget
The following parameters are needed :
Effective Eb/No :
where : IM = Implementation Margin, PCerror = Power Control Error
Thermal Noise Spectral Density = k*T = -174 (dBm/Hz)
Information Rate R(dBHz) = 30 + log(R(kpbs))
BTS Noise Figure NF = 5 dB (or less using a TMA)
BTS Receiver Noise N = R(dBHz) + NF
BTS RX Sensitivity S :
UMTS Radio Network Planning : Link Budget
Erroro
b
Effectiveo
b PCIMNE
NE
NNES
Effectiveo
b
UMTS Radio Network Planning : Link Budget Cable, Combiner and Connector Loss LCCC = 3 dB BTS Rx Antenna Gain GRX_Ant = 18 dBi BTS RX Sensitivity @ Air Interface :
Log-Normal Fade Margin (@ 98 % Area Probability) LNF = 9 dB Handover Gain (Macro Diversity Gain) GHO = 3 dB Penetration Loss Table :
AntRxCCCceAirInterfa GLSS _
In-building penetration loss dense urban 20In-building penetration loss Urban 15In-building penetration loss SubUrban 12Low In-building penetration loss Rural 7In-car penetration loss 6Outdoor 0
Interference Margin (@ 50% Load) INT_Margin = 3 dB This margin is in fact a tolerance of a load of 50 % due to interference from MSs
in neighboring cells
Maximum Allowed Path Loss MAPL(dB) :
Cell Radius : MAPL = A + B*Log(r) from Okumura-Hata extended to 2.2 GHz
A and B are frequency, antenna height and environment - dependent
UMTS Radio Network Planning : Link Budget
inMINTLGLNFLEiRPdBMAPL npenetratioHObody arg_)(
UMTS Radio Network Planning : Cell Count
r Surface of a tri-sectorial cell :
Number of Sites = Number of Cells /3
2
23 rASector
Example :
if MAPL = 127 dB (typical for Dense Urban) A = 137.67 for f = 1980 MHz and Hb = 30 m and 3 dB Correction factor for
a Metropolitan Environment (cf. Extended Okumura-Hata) B = 35.22
then r = 0.409 km and Asector = 0.144 km2
We assume Stotal = 100 km2 for Belgium (Dense Urban) : the Number of Sectors required is thus 100/0.144 = 690 leading to 230 tri-sectorial Sites.