Frequency_Planning.ppt

© SIEMENS Limited 1999
ICN PLM CA NP
s
Frequency Planning

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ICN PLM CA NP
Main Topics
Frequency planning - task definition 2
Specturm efficiency 2
Frequency assignment methods 3
Frequency reuse 4
Frequency reuse clusters 5
Frequency reuse distance 5
Interference types 6
Reference interference performance 6
Co-channel interference factor 7
Cluster size and co-channel interference 7
Comparison between omni/sectorised cells 8
Sectorisiation methods 8
Calculation example 9
Factors affecting the C/I ratio 9
Effect of fading 10
Fading margin - C/I 10
Simulations of cell configurations 11
Interference analysis 12
Interference plots 12
Channel assignment 13
Frequency reuse chain 13
Frequency groups 14
Base station identity code (BSIC) 14
Interference analysis - aim and method 15
Downlink and uplink interference 15
Radio link control options 16
Power reduction (power control) 17
Discontinuous transmission 18
Frequency hopping 18
Simulation results 20
System quality in FH-GSM 20
Frequency planning strategies 21
Frequency reuse with RLO 21
Frequency planning HCS 22
Multiband operation 22
Concentric cells 23
Adaptive antenna principles 24

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ICN PLM CA NP
S I E M E N S
GSM
S I E M E N S
GSM
S I E M E N S
GSM
F1,F4
F2,F5
F3,F6
Frequency Planning
 Task definition:
 Assign carriers to cells according to traffic demand while in a way as
to minimise interference
Minimise interference
Improve frequency reuse
Enhance capacity

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ICN PLM CA NP







MHz
Km
Erl
F
A
T
S
*
* 2
For a given network
it is an indicator for
the quality of the
network design
(capacity limited
areas)
Spectrum Efficiency
 Definition
 S = Spectral Efficiency
 T = Traffic
 A = Area
 F = Occupied Spectrum
 Objectives:
 use spectrum efficiently in order to maximise capacity for a given
spectrum allocation
 minimise interference

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ICN PLM CA NP
Frequency Assignment Methods
 Dynamic Channel Assignments
 DECT:
 no fixed channels are assigned to each cell.
 any channel in a composite of all radio channels can be assigned to the
mobile unit.
 mobile monitors all channels and chooses a frequency/ timeslot
combination with good signal strength and low interference
 frequency planning not necessary
 GSM:
 directed retry is a form of dynamic channel assignment

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ICN PLM CA NP
Frequency Assignment Methods
 Fixed Channel Assignments (e.g. GSM)
 cells are allocated channels on a permanent basis
 in general: frequency planning is necessary
 exception: allocation of all TCH frequencies to each cell, using frequency
hopping
1/3 reuse pattern
A1 A1
A2
A3 A3
A2
A1
A1
A2
A3
A2
A3
A1
A3
A2
1/1 reuse pattern
A A
A
A A
A
A
A
A
A
A
A
A
A
A
A1
A2
A3 B1
B2
B3
D3
D1 C1
C2
C3
D2
4/12 reuse pattern

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ICN PLM CA NP
R R
D
C1 C2
f1 f1
Concept of Frequency Reuse
 Use of radio channels on the same carrier frequency
covering different areas
fn = Carrier frequency on each cell
Cn = Cell name
D = Distance between reuse cells
R = Cell radius

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ICN PLM CA NP
Frequency Reuse
 Affected by interference between cells
 Type of geographic terrain (radio propagation conditions)
 Antenna height / tilting
 Antenna types
 Omnidirectional antenna
 120 deg Directional (Rhomboidal)
 60 deg Directional (Cloverleaf)
 Transmission output power
 Radio Link Control features
 Frequency Hopping
 Dynamic Power Control
 DTX / VAD
Frequency reuse
efficiency

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ICN PLM CA NP
Frequency Reuse Clusters
Larger cluster size
Longer distance
between interferers
1
3
4
2
1
3
4
2
1
3
4
2
1
3
4
2
1
3
4
2
K=4
1
5
4
3
6
7
2
1
5
4
3
6
7
2
1
5
4
3
6
7
2
1
5
4
3
6
7
2
K=7
1
5
4
3
6
7
2
8
9 1
5
4
3
6
7
2
8
9
1
5
4
3
6
7
2
8
9
1
5
4
3
6
7
2
8
9
K=9
1
5
4
3
6
7
2
8
9
10
11
12 1
5
4
3
6
7
2
8
9
10
11
12
1
5
4
3
6
7
2
8
9
10
11
12
K=12
1
3
2
1
3
2
1
3
2
1
3
2
1
3
2
K=3
Less interference
BUT
Reduced capacity
potential

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ICN PLM CA NP
R
r
D
D
ai
aj
R
3
a
)
60
(
Cos
ija
2
)
aj
(
)
ai
(
D 0
2
2
2


 R
K
D 3

R
r 3
5
.
0

R
a 3

2
2
j
ij
i
K 


Frequency Reuse distance
 Reuse pattern in the Hexagonal grid
 Outer Cell Radius : R
 Inner Cell Radius :
 Distance between adjacent
centers
 Minimum distance between
the centers of reuse cells

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ICN PLM CA NP
Interference Types
 C/Ic - common channel interference
 The ratio of the level of the desired received signal to the level of
unwanted received signals at the same frequency
 Requirement :
 C/Ic > 9 dB.
 C/Ia - adjacent channel intereference
 The ratio of the level of the desired received signal to the level of
unwanted received signals at frequencies n x 200 kHz apart.
 Requirement :
 First adjacent channel interference (200 kHz apart): C/Ia1 > -9dB
 Second adjacent channel interference (400 kHz apart): C/Ia2 > -41dB
 Third adjacent channel interference (600 kHz apart): C/Ia3 > -49dB

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ICN PLM CA NP
Reference Interference Performance
 GSM Recommendation 05.05

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ICN PLM CA NP
Tranmission loss(dB)
Distance
C/I
H
W
N0 
Coverage Guard zone
R D-R
H=Handover margin
Propagation path-loss equation:
where C = Received carrier power
R = Distance from transmitter to receiver
C R
  
 = Constant
 = Propagation path-loss slope
= Frequency reuse distance to cell k
= Number of cochannel interfering cells
in the first tier
I
K
C
I
R
k
k
K
D
I







1
Co-channel Interference Factor
1
1
1
D
D-R
R
k
D

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ICN PLM CA NP
Six effective interfering cells from first tier
1
1
1
1
1
1
1
1
1
1
First tier
Second tier
Cochannel interference reduction factor:
K
R
D
q 3


D
Average C/I : All interferers at D
I
K
k
k
K
q
R
I
C
I
D









1
Worst case C/I : All interferers at D-R
 
I
K
k
k
K
q
R
I
C
I
D



1
1







Only first tier
Cluster Size and Co-channel Interference

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ICN PLM CA NP
1 1
1
1
1
1
1
1
1
1
First tier
Second tier
Omni cells
1
4
3
2
3
2
1
4
3
2
1
4
3
2
1
4
3
2
1
4
3
2
120 deg.
Directional
Antennas
First tier
 for first tier KI = 6 (theoretically)  for first tier KI = 2 - 3
 narrow beam antennas (e.g. 60º)
better than wide beam antennas (e.g.
120º)
Ex.
3x4
Comparison between Omni / Sectorised Cells

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ICN PLM CA NP
120 degree 3 dB beamwidth 60 degree 3 dB beamwidth
Sectorisiation Methods
 Rhomboidal sectorisation
 better sidelobe coverage
 more interference
 Cloverleaf sectorisation
 less interference than
Rhomboidal sectorisation

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ICN PLM CA NP
Omni Sectored
Cluster size C/I
(dB)
average
C/I
(dB)
worst case
Cluster size C/I
(dB)
worst case
7 15.36 14.25 3x3 13.52
9 17.27 16.41 3x4 16.48
12 19.45 18.81 3x7 21.08
21 23.71 23.34
Sectorised sites suffer from less
interference  more capacity
Calculation Example
 C/I for various cluster sizes
 path loss proportional to (distance)-3.5 (as in Hata formula)
 120º antennas assumed in case of sectorised sites
 no fading included

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ICN PLM CA NP
Factors Affecting the C/I Ratio
 Propagation path loss slope
 range
 20 dB/dec for free space
 40 dB/dec for perfect ground reflection
 50 dB/dec for highly attenuating environment
 from Hata: 35 dB/dec
 larger slope  less interference
 Site implementation
 Standard deviation of long term fading
 larger values  more margin needs to be planned for C/I
 Cluster size
 Handover margin

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ICN PLM CA NP
Median level (50 %)
Median level (50 %)
Received
level
Distance moved (within a small area
- constant local mean received level
Worst case C/I
Median C/I
Effect of Fading
 Fading margin required
 both wanted and interfering signals experience variations due to log-
normal fading
C
I

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ICN PLM CA NP
Fading Margin - C/I
 Assumption
 wanted and interfering signals have log-normal distributions
 wanted and interfering signals are uncorrelated
 Example:
2
erferer
int
2
wanted
total 

 

dB
6
erferer
int
wanted 


dB
5
.
8
total 

Cell edge
probability
Cell area
probability
Margin for
 = 8.5 dB
50 % 74 % 0 dB
75 % 90 % 6 dB
87.5 % 95 % 10 dB
90 % 97 % 11 dB
95 % 99 % 14 dB

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ICN PLM CA NP
standard
dev. (dB)
area
coverage
90%
area
coverage
95%
area
coverage
98%
4 3.6 5.6 7.8
5 5.4 7.9 10.5
6 7.4 10.4 13.5
7 9.6 12.9 16.1
8 11.8 15.6 18.4
Fading Margin - C/I
 Required fading margins from simulations
 path loss proportional to (distance)-3.5 (as in Hata formula)
 fading conditions included
 simulation over whole cell
 assume 6 co-channel interferers
Add FM to 9 dB
C/I requirement
Source: Lüders

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ICN PLM CA NP
std. deviation > 5 dB 6 dB 7 dB
cluster: % prob. % prob. % prob.
omni 7 92 87.5 82.5
omni 9 95 92 88
omni 12 (96.5) 95 92
clover leaf 3/9 92.5 89 84
clover leaf 4/12 95.5 93 89
clover leaf 7/21 (98.5) 97.5 95.5
std. deviation > 5 dB 6 dB 7 dB
cluster: reached C/I reached C/I reached C/I
omni 7 10 8 6
omni 9 12 10 8
omni 12 14 12 10
clover leaf 3/9 10.5 8.5 6.5
clover leaf 4/12 12.5 10.5 8.5
clover leaf 7/21 16.5 14.5 12.5
Simulations of Cell Configurations
 Probability for C/Ic  9 dB
 Larger cluster size
 higher probability of
acceptable C/I
 C/Ic-ratio for 90 % probability
 Larger cluster size
 higher C/I achieved

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ICN PLM CA NP
Interference Analysis (I)
 C/I thresholds (dB) for analysis:
 in this way thresholds can be derived for C/I analysis in planning tool
Quality
valuation
calls
affected
%
 =8dB
req. mean
C/Ic
 =7dB
req. mean
C/Ic
 =6dB
req. mean
C/Ic
 =8dB
req. mean
C/Ia
 =7dB
req. mean
C/Ia
 =6dB
req. mean
C/Ia
excellent <=2 >=27.5 >=25 >=22.5 >=14.5 >=12 >=9.5
very good >2-5 24.5-27.5 22-25 19.5-22.5 11.5-14.5 9-12 6.5-9.5
good >5-10 21-24.5 18.5-22 16.5-19.5 9-11.5 6.5-9 3.5-6.5
fair >10-20 18-21 15.5-18.5 13.5-16.5 4.5-8.5 2.5-6.5 0.5-3.5
bad >20 <18 <15.5 <13.5 <4.5 <2.5 <0.5

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ICN PLM CA NP
Interference Plots
 Example: C/I  Example: C/A

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ICN PLM CA NP
Frequency
group
A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3
Channels 1
13
25
2
14
26
3
15
27
4
16
28
5
17
29
6
18
30
7
19
31
8
20
32
9
21
33
10
22
34
11
23
35
12
24
36
- A,B,C,D = Sites within cluster
- 1,2,3 = Sector No.
A1
A2
A3 B1
B2
B3
D3
D1 C1
C2
C3
D2
Channel Assignment
 The allocation of specific channels to cell sites and mobile
units.
 Example: K = 4x3 cell pattern 4/12 Cell pattern
Swap to
avoid C/Ia
between
D3 / A1

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ICN PLM CA NP
A1 B1
C1
D1
A2
B2
C2
D2
A3
B3
C3
D3
A1
B1
C1
A2
B2
C2
A3
B3
C3
K = 3/9
K = 4/12
A1 B1 C1
D1
E1
F1
G1
A2
B2
C2
D2
E2
F2
G2
A3
B3
C3
D
3
E3
F3 G3
K = 7/21
Frequency group denomination for different reuse patterns
Frequency Reuse Chain

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ICN PLM CA NP
A1
A2
A3 C1
C2
C3
B1
B3
3/9 Cell Pattern
A1
A2
A3 C1
C2
C3
B1
B3
A1
A2
A3 C1
C2
C3
B1
B3
A1
A2
A3 B1
B2
B3
D3
D1 C1
C2
C3
4/12 Cell Pattern
A1
A2
A3 B1
B2
B3
D3
D1 C1
C2
C3
A1
A2
A3 B1
B2
B3
D3
D1 C1
C2
C3
D2
B2
B2 B2
D2
D2
Frequency Groups

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ICN PLM CA NP
Base Station Identity Code (BSIC)
BSIC = NCC + BCC
NCC : Network Colour Code (0..7)
BCC : Base Station Colour Code
(0..7)
KO N
FERENZ
?
OK
32
5 23 BA RKM E
Y ER
1
D
E
F
3
GH
I
4
M
N
O
6
P
Q
R
S
7
W
XY
Z
9
TU
V
8
A
B
C
2
JK
L
5
0
R IN T
F
f1
f1
BCCH
(f1,BSIC = 12)
f1
BCCH (f1,BSIC =
22)
BCCH (f1,BSIC = 15)
Different country

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ICN PLM CA NP
Interference Analysis
 The aim:
 Push interference to areas which are not important (e.g. water, forests)
 Reduce interference in high traffic areas (e.g. downtown urban)
 Method:
 Use weighting according to area type
 Traffic Weighting
 Weighting factor between 0 and 1 to each pixel according to the traffic
density
 Clutter Weighting
 Urban : High weighting
 Suburban : Medium weighting
 Open : Low weighting
 Forest, Water : Zero

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ICN PLM CA NP
K
ONFERENZ?
OK
32523 BA
RKMEYER
1
D
E
F
3
G
H
I
4
M
N
O
6
P
Q
R
S
7 W
X
Y
Z
9
TU
V
8
A
B
C
2
JK
L
5
0
R INT
F
K
ON
FEREN
Z?
OK
32523 BA
RKMEYER
1
D
E
F
3
G
H
I
4
M
N
O
6
P
Q
R
S
7 W
X
Y
Z
9
TU
V
8
AB
C
2
JK
L
5
0
R INT
F
Interfering signal UL
f1 f1
Downlink and Uplink Interference
 In general different for a given MS location at a given time
 Uplink interference analysis - complex because the source of
the interference may be moving
 not supported by most tools
 external interference sources generally only affect one link
 co-channel interference
 intermodulation
Non-GSM
interferer

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ICN PLM CA NP
Tighter
Frequency
Reuse
ENHANCEMENT
System Capacity
Limitation
Increase
I n t e r f e r e n c e
AVERAGING
AVERAGING
FH
FH
PC
PC
DTX
DTX
REDUCTION
DIVERSITY
Radio Link Control Options
Source: ÖN MN ER 51, ÖN MN P 31

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ICN PLM CA NP
Reduces interference due to minimum transmission power
Reduces interference due to no transmission during silence periods
Mitigates frequency selective Rayleigh fading for slow MSs
Averages interference due to interference diversity
Capacity Enhancement by RLO
 Power Control (PC)
 Discontinuous Transmission (DTX)
 Frequency Hopping (FH)
 Interference increase by tighter frequency re-use
can be compensated for by combination of FH, PC and DTX
 Capacity increase via tight frequency re-use at moderate cost

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ICN PLM CA NP
 Advantages
 Save MS power
 increase battery usage
time of mobile
 reduce radiation to user
 Reduce interference
 enhanced capacity
BTS
MS 2
MS 1
T
X
P
W
R
T
X
P
W
R
Power Reduction

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ICN PLM CA NP
Power Control Decision
Power Increase
(bad quality)
Power Decrease
(good level)
Power Decrease
(good quality)
Power Increase
(bad level)
RXQUAL
RXLEV
0
7
63
L_RXQUAL_XX_P
U_RXLEV_XX_P
L_RXLEV_XX_P
U_RXLEV_XX_P
2*POW_RED_STEP_SIZE

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ICN PLM CA NP
Discontinuous Transmission
 Why DTX?
 on average people speak about 40 % of the time
 interference is related to traffic on the network  avoid transmitting
when user is not active
 increased frequency and hence capacity possible
 every 480 ms a 20 ms frame containing background noise information is
sent - “comfort noise”
 save MS power
 increase battery usage time of mobile
 reduce radiation to user
 Voice Activity Detection (VAD) needed
 detect when user not active
 PS! No benefit for data communications

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ICN PLM CA NP
Frequency Hopping
 In GSM - slow hopping - 217 hops per second
 cyclic or random
 Advantages
 average out interference between users  plan for average case, not
worst case
 provide frequency diversity  combat flat fading
 mainly relevant for stationary or slow moving users
 improved performance of coder / interleaver
 Implementations
 Baseband hopping:
 Advantage: Can use filter
combiner (low combiner losses)
 Disadvantage: Require 1 TRX
per frequency in hopping sequence
 Synthesised hopping
 Advantage: Can hop over more
frequencies than no. of TRX’s
 Disadvantages: BCCH carrier cannot
hop, cannot use filter combiner

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ICN PLM CA NP
10.0
7.5
6.5
6.0
8 Frequencies
Yes
Yes
Yes
None
None
None
None
Frequency Hopping Diversity TU3 TU50 HT100
None 11.5 6.8
2 Frequencies 6.7
4 Frequencies 8.3 6.6
8 Frequencies 7.5 6.0 6.6
None Yes 6.8 - -
2 Frequencies 5.5 - -
4 Frequencies 4.6 - -
4.1 - -
Frequency Diversity
 Averaging of short term fading
 S/N required to obtain 0.2 % residual BER for class 1b bits

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ICN PLM CA NP
Frequency Hopping
 Cyclic hopping
 Optimum frequency diversity
 Correlated hopping between cells,
but
 C and I channels change in an
uncorrelated way
 unequal no of frequencies for
different cells
 Interference averaging
 Pseudo random hopping
 Poor frequency diversity
 Uncorrelated hopping between
cells
 Good interference averaging
f1
f2
f3
f4
f1
f2
f3
f4
Frame sequence Frame sequence

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ICN PLM CA NP
78.8%
47.0%
29.5%
90.1%
56.6%
52.9%
34.7%
PC on, DTX on
PC off, DTX on
PC on, DTX off
PC off, DTX off
good interference diversity,
but poor frequency diversity
good frequency diversity and
sufficient interference diversity
Random FH Cyclic FH
Simulation Results:
 5 Carriers in High Traffic Network Dedicated Band Planning
Source: ICN CA MR EE6

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ICN PLM CA NP
CH
RH
NH
System Quality in FH-GSM
 With FH:  C/I decreases, raw BER and RXQUAL get worse
 But:  Voice quality (FER) improves
Source:
ICN CA MR EE6
C/I [dB]
per location
probability
FER [%]
probability
RxQual does not reflect
quality as perceived by
the user

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ICN PLM CA NP
total operator bandwidth (8.6 MHz = 43 carriers)
43 carriers for both BCCH and TCH
Common band:
15 BCCH carriers
Dedicated band:
28 TCH carriers
Frequency Planning Strategies
 For the broadcast channel (BCCH) no RLO is possible
 required cluster size BCCH channel > required cluster size TCH
channels
 dedicated band for BCCH channels sometimes used

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ICN PLM CA NP
Frequency Reuse with RLO
 BCCH channel:
 large reuse clusters (in theory 12 is possible, in practice 15 - 21)
 TCH channels
 cluster size 1 x 3 or even 1 x 1 possible
however
 offered traffic may be limited by interference (soft blocking) rather
than by number of TCH channels (hard blocking)
 Offered traffic calculations
 capacity determined by simulations
 real (and not ideal) network simulations are needed

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ICN PLM CA NP
Spectrum GA
Spectrum GB
Spectrum GC
Spectrum GD
Spectrum GE
1/3 pattern
3/9 pattern
4/12 pattern
7/21 pattern
9/27 pattern
Frequency Planning HCS
 Challenge: Avoid
interference between layers
 allocate all frequencies to
all layers
or
 simplify planning /
optimisation task by
providing separate
frequency bands for
different layers

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ICN PLM CA NP
Multiband Operation
GSM900
25MHz
DCS1800
75MHz
e.g. 4MHz
(ca. 20 carriers)
each operator
e.g. 4MHz
(ca. 20 carriers)
each operator
8MHz
(ca. 40 carriers)
each operator
 Different layers consisting of different frequency bands
 GSM900
 GSM1800
 can also include other GSM bands

s
ICN PLM CA NP
Concentric Cells
 TRX’s in cell split
 outer area
 inner area
 BCCH covers both areas
 Very efficient frequency reuse for
inner area
 1 x 3 possible
 Same antennae for both areas
 Handover criteria
 level
 level and distance
 C/I (intelligent overlay / underlay

s
ICN PLM CA NP
Conclusions
 higher capacity potential for hierarchical cells
 concentric cells for special application areas
Comparison with Hierarchical Cells
Concentric Cells
 Advantages
 economical usage of sites &
antennas
 high frequency reuse
 high capacity gain if traffic
concentrated in inner area (Hot
Spot Detection)
 Disadvantages
 limited number of inner "cells"
 small gain for homogeneous
traffic
 inflexible installation:
 no adaptation to traffic
distribution

s
ICN PLM CA NP
Adaptive Antennae Principles
 Adaptation of "antenna diagram"
to reception condition
 Increase of antenna gain and cell
radius by small beams
 Reduction of interference ->
reduction of cluster size ->
capacity gain
 interference notching
 small beams
 (less interference received in UL
/ less interference spread in DL)
 Switching between beams
 Adaptive electronic beam forming
 BCCH carrier has to be transmitted
within the whole cell
 Space Division Multiple Access
SDMA:
 multiple usage of one physical
channel at same site
 additional capacity gain

s
ICN PLM CA NP
Adaptive Antennae Classification
smart
antennas
fixed
beams
single channel
usage per cell
multiple channel
usage per cell
dynamic beams
electronically
dynamic beams
electronically
fixed
beams
sector
antennas
electronically
formed
sector
antennas
electronically
formed
Reduction of Cluster Size
SDMA

s
ICN PLM CA NP
Adaptive Antennae
What is the most appropriate
point to perform beam selection
(combining & distribution) ?
by sector antennas
electronically formed
DSP 1
DSP 2
Combining &
Distribution
DSP 1
DSP 2
Combining &
Distribution
K1 K2 K3
K1
K3
K2
beam forming
coefficients
antenna array
fixed beams
MS
I 1 I 2
I 3
Fixed Beams
Source: ÖN MN ER 51, ÖN MN P 31

Frequency_Planning.ppt

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