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OMF 007001
Frequency Planning
ISSUE1.4
OMF 007001
Frequency Planning
ISSUE1.4
Wireless Training Department
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contentcontent
Frequency planning
Tight frequency reuse
Frequency hopping
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Content of Frequency planningContent of Frequency planning
Frequency resource of GSM system
Requirement for interference and carrier-to-
interference ratio
Signal quality grade coding
Concept of frequency reuse
4*3 frequency reuse
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GSM 900 :
GSM 1800 : 1710 1785 1805 1880
Duplex distance : 95 MHz
890 915 935 960
Duplex distance : 45 MHz
Frequency Resource of GSM SystemFrequency Resource of GSM System
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Frequency Band ConfigurationFrequency Band Configuration
GSM900:
BTS receiver (uplink ): f1 (n) =890.2+ (n-1)*0.2 MHz
BTS transmitter (downlink ): f2 (n) =f1 (n) +45 MHz
GSM1800:
BTS receiver (uplink ): f1 (n) =1710.2 + (n-512) * 0.2 MHz
BTS transmitter (downlink ): f2 (n) =f1 (n) +95 MHz
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All useful signals carrier
All useless signals interference=
GSM standard: C / I >= 9 dB
In practical projects: C / I >= 12dB
Useful signal Noise from environment
Other signals
Requirement for Interference and Carrier-
to-Interference Ratio
Requirement for Interference and Carrier-
to-Interference Ratio
C/I =
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Requirement for Interference and Carrier-
To-Interference Ratio
Requirement for Interference and Carrier-
To-Interference Ratio
All useful signals carrier
All useless signals interference=
GSM standard: C / I >= 9 dB
In practical projects: C / I >= 12dB
Useful signal Noise from environment
Other signals
C/I =
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RXQUAL Mean BER BER rangeclass (%) from... to
0 0.14 < 0.2%
1 0.28 0.2 ... 0.4 %
2 0.57 0.4 ... 0.8 %
3 1.13 0.8 ... 1.6 %
4 2.26 1.6 ... 3.2 %
5 4.53 3.2 ... 6.4 %
6 9.05 6.4 ... 12.8 %
7 18.1 > 12.8 %
Fairly good
Intolerable
Good
Acceptable
Signal QualitySignal Quality
Receiving quality (RXQUAL parameter)
Level of receiving quality (0 ... 7)
Bit error rate before decoding and error correction
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{fi,fj..fk}
{fi,fj..fk} {fi,fj..fk} {fi,fj..fk}.. ..
Macro-cell system
d
Micro-cell system
Concept of Frequency ReuseConcept of Frequency Reuse
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The Reason of Frequency ReuseThe Reason of Frequency Reuse
Frequency resource is limited. If there is 8MHz frequency
resource, 8 MHz = 40 channels * 8 timeslots = 320
==> max. 320 users can access the network at the same
time.
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Looser reuse
Higher frequency reuse
efficiency, but interference
is serious. More technique
Is needed.
Tighter reuse
0 10 20
Little interference, but frequency
reuse efficiency is low.
Reuse DensityReuse Density
Reuse density is the number of cells in a basic reuse cluster.
4*312
n*mn*m
n: BTS number in a basic reuse cluster
m: Frequency group number in a BTS
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[fn]
[fn]
D
[fn]
R
Reuse of a frequency causes the co-channel interference
Problem of Frequency ReuseProblem of Frequency Reuse
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Interference (C/I) EstimationInterference (C/I) Estimation
6
1K
!
q
I
C
/
/R ( k )
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R
D
This old-fashioned frequency distribution
mode is not recommended
Frequency Reuse PatternsFrequency Reuse Patterns
Purpose: to minimize the interference in the whole network with
the final frequency allocation plan
Theoretically
Regular hexagon cell
Regular network distribution
Cell cluster
Multiplexing distance
D = R *sqrt(3*K)
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A1
C1
B1D1
A2
A3B2
B3
C2
C3D2
D3
A1
C1
B1D1
A2
A3B2
B3
C2
C3D2
D3
A1
C1
B1D1
A2
A3 B2
B3
C2
C3
D2
D3 A1C1
B1D1
A2
A3B2
B3
C2
C3D2
D3
A1
C1
B1 D1
A2
A3B2
B3
C2
C3
D2D3
A1
C1
B1D1
A2
A3B2
B3
C2
C3D2
D3
4*3 Frequency Reuse4*3 Frequency Reuse
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A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3
34 35 36 37 38 39
40 41 42 43 44 45 46 47 48 49 50 51
52 53 54 55 56 57 58 59 60 61 62 63
64 65 66 67 68 69 70 71 72 73 74 75
76 77 78 79 80 81 82 83 84 85 86 87
88 89 90 91 92 93 94 95
Illustration of Frequency Allocation of4*3
Frequency Reuse
Illustration of Frequency Allocation of4*3
Frequency Reuse
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OutlineOutline
Frequency planning
Tight frequency reuse
Frequency hopping
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Tight Frequency Reuse TechnologyTight Frequency Reuse Technology
Multi-layer reuse pattern
Underlaid and overlaid cell
1*3
1*1
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Multi-layer Reuse PatternMulti-layer Reuse Pattern
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BCCH: n1
TCH1: n2
TCH2: n3
~
TCHm-1: nm
n1n2n3 n4 ...... nm
And n1+n2+...+nm=n
Multi-layer Reuse PatternMulti-layer Reuse Pattern
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Multi-layer Reuse Pattern Frequency AllocationMulti-layer Reuse Pattern Frequency Allocation
Suppose that the available frequency carrier is 10MHZ,
channel number is 4694, the Multi-layer reuse pattern
should be:
typeAllocatedfrequencies
umber ofavailable
frequencies
H 46~ 1
H1 ~66 9
H 6 ~ 4
H ~
H4 ~ 6
H 9~94 6
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BCC H TCH1 TCH2 TCH3 TCH4
{f1,f3,f5...f23}
{f1,f2,f3,f4,f5...f40}
{f2,f4..f22,f24...f40}
Multi-layer Reuse Pattern Frequency AllocationMulti-layer Reuse Pattern Frequency Allocation
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Capacity increase when reuse density is multiplied: Supposing there are 300 cells
Bandwidth: 8 MHz (40 frequency)
Normal 4*3 reuse: reuse density=12
==> network capacity = 40/12 * 300 = 1000TRX
Multiple reuse:
BCCH layer: re-use =14, (14 frq.)
Normal TCH layer: re-use =10, (20 frq.)
Aggressive TCH layer:re-use = 6, (6 frq.)
==> Network capacity = (1 +2 +1)* 300 =1200 TRX
cap NBW
re use
i
i
.!
Advantages of Multi-layer Reuse PatternAdvantages of Multi-layer Reuse Pattern
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The inner circle covers a smaller area, and the
frequency can be reused more tightly.
Underlaid/Overlaid Frequency AllocationUnderlaid/Overlaid Frequency Allocation
Overlaid-cellUnderlaid-cell
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Super fn
Regular fmRegular fm
Regular fm
Super fn
BCCH 15f Regular 24f Super 12f
BCCH Reuse density: 15
R TCH TRX reuse density: 12
S TCH TRX reuse density: 6
Overlaid/Underlaid Frequency ConfigurationOverlaid/Underlaid Frequency Configuration
Super fn
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BCCH14+TCH36
1BCCH+3TCH
1BCCH+3TCH 1BCCH+3TCH
1BCCH+12TCH
1BCCH+12TCH 1BCCH+12TCH
4*3 1*3
4*3 and 1*3 Reuse Patterns4*3 and 1*3 Reuse Patterns
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TRX1 TRX2 ... TRX7
TRX
8 TRX
9... TRX
14 TRX
15 TRX
16...TRX
21
TRX1 TRX2 ... TRX7
TRX8 TRX9... TRX14 TRX15 TRX16...TRX21
The red items are BCCH RCs
Illustration of1*3 TCH Frequency AllocationIllustration of1*3 TCH Frequency Allocation
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Frequency Planning PrincipleFrequency Planning Principle
There should be no co-channel frequency carriers in one BTS.
The frequency separation between BCCH and TCH in the same cell
should be not less than 400K.
When frequency hopping is not used, the separation of TCH in the
same cell should be not less than 400K.
In non-1*3 reuse mode, co-channel should be avoided between the
immediately neighbor BTS.
Neighbor BTS should not have co-channels facing each other directly.
Normally, with 1*3 reuse, the number of the hopping frequencies
should be not less than twice of the number of frequency hopping
TRX in the same cell.
Pay close attention to co-channel reuse, avoiding the situation that
the same BCCH has the same BSIC in adjacent area.
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An example network in a specific place, BTS are densely located.The topography is plain. The maximum BTS configuration is S3/3/2.
Initial planning:
Example of Frequency PlanningExample of Frequency Planning
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Final frequency planning:
Example of Frequency PlanningExample of Frequency Planning
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Example of1*3 Frequency ReuseExample of1*3 Frequency Reuse
Suppose 900 band: 96124
BTS configuration: S3/3/3
BCCH layer: 96109 reuse pattern: 4*3
TCH layer: 110124 reuse pattern: 1*3
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Group 1 (MA1): 110 111 112 113 114 Cell1
Group 2 (MA
2): 115 116 117 118 119 Cell2
Group 3 (MA3): 120 121 122 123 124 Cell3
TCHConsecutive Allocation SchemeTCHConsecutive Allocation Scheme
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TCH Interval Allocation SchemeTCH Interval Allocation Scheme
Group 1 (MA1): 110 113 116 119 122 Cell1
Group 2 (MA
2): 111 114 117 120 123 Cell2
Group 3 (MA3): 112 115 118 121 124 Cell3
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Comparison Between Multi-layer reuse and 1*3Comparison Between Multi-layer reuse and 1*3
For Multi-layer reuse pattern, either Base band hopping or RF
hopping can be used. But for 1x3 reuse, only RF hopping can be
used.
Multi-layer reuse pattern is a gradual process for TCH frequency
planning. In other words, the reuse is rather loose in TCH1 layer and
it is quite close in the last TCH layer (such as TCH5). The reason for
this pattern is that base band hopping is used in the Multi-layer reuse
pattern. When there are rather few frequency carriers, the hopping
gain is small. Therefore, more frequency carriers should be allocated
for the layer with small TCH and then the reuse coefficient is
relatively large. When RF hopping is used in the Multi-layer reuse
pattern and there are a large number of frequency carriers, the
hopping gain is high and the reuse coefficient can be very small. In
addition, the Multi-layer reuse pattern is of a free pattern. It is
different from base band hopping, in which the reuse must be loose
in the first TCH layer and more close in inner layers.
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Comparison Between Example of Frequency
Planning and 1*3
Comparison Between Example of Frequency
Planning and 1*3
The frequency planning for the 1x3 mode is simple and it is
easy to plan the frequency for new added BTS.
1x3 mode requires a rather regular BTS location distribution.
For the cells with fixed number of TRX, when the traffic is
heavy, the 1x3 provides higher service quality than that of
Multi-layer reuse pattern.
TRX can be easily added to the 1x3 network, but TRX number
of hopping should not exceed the product of the allocatedhopping frequency number and the max RF load ratio.
BCCH of Multi-layer reuse pattern can take part in the
frequency hopping, while BCCH in 1x3 mode can not.
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OverviewOverview
Frequency planning
Tight frequency reuse
Frequency hopping
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Content of Frequency HoppingContent of Frequency Hopping
Class of hopping
Advantages of hopping
Parameter of hopping
Collocation of hopping data
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FrequencyHoppingFrequencyHopping
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Class of HoppingClass of Hopping
Hopping can be implemented in two ways
Base-band hopping
RF hopping
Class according to the min hopping time
unit
Timeslot hopping
Frame hopping
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RF Hopping PrincipleRF Hopping Principle
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Class ofHoppingClass ofHopping
Frame hopping
Frequency changes every TDMA frame. The different channel
of one TRX uses the same MAIO.
Timeslot hopping Frequency changes every timeslot. The different channel of one
TRX uses the different MAIO.
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Advantages ofHoppingAdvantages ofHopping
Get an agreeable radio environment.
Provide a similar communication quality for every user.
Tighter reuse patterns are possible to be used for larger
capacity.
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Smoothen and average the interference
Interference Diversity ofHoppingInterference Diversity ofHopping
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DescriptionHopping ParametersDescriptionHopping Parameters
At the Um interface, the ARFCN on a specific burst is an
element in MA set. MAI is used for indication, referring to a
specific element in the MA set.
When 0< MAI
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DescriptionHopping ParametersDescriptionHopping Parameters
At the air interface, the RC number on a specific burst is an
element in MA set. MAI is used for indication, referring to a
specific element in the MA set.
When 0< MAI
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Description ofHopping ParametersDescription ofHopping Parameters
HSNhopping sequence number063.
HSN=0cycle hopping.
HSN0 random hopping. Every sequence number
corresponds a pseudo random sequence.
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Hopping ParametersHopping Parameters
Hopping mode: the mode used by the BTS system, including
three options: not hopping, base band hopping and RF
hopping.
CA (Cell Allocation Table): refer to all available frequencycarriers in the cell. The allocation should be consecutive
starting from the effective frequency carrier 0. There should be
no empty data item. The frequency carrier configuration
should be in an ascending order.
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Hopping ParametersHopping Parameters
MA (Mobile Allocation Set): the set of available RF bands
when hopping, containing at most 16 frequency carriers. The
frequency being used must be those of the corresponding cell
number in CellA
llocation Table, and no frequency of BCCH channel should be in the set.
HSN (Hopping Serial Number): used to define the actual rule
for hopping. 0 stands for sequence hopping and other values
for pseudo random sequence hopping.
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Hopping ParametersHopping Parameters
MAIO (Mobile Allocation Index Offset): used to define the
initial frequency of the hopping.
The MAIO of all channels of one hopping TRX must be
identical. The MAIO of channels of different hopping TRX in
the same cell must be different.
TSC (Training Sequence Code): used for delay equalization at
the receiver end. TSC must be the same as the BTS color
code. When an MS or BTS receives signals, delay
equalization is started with the specified TSC. But for the co-
channel signals with different TSC, delay equalization is
impossible, so that demodulation can not be received. In this
way, erroneous receiving is prevented effectively and then co-
channel interference is prevented.
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Note: means absolutely same; means absolutely different;
# means uncertain.
Hopping Data Configuration RulesHopping Data Configuration Rules
TSC CA MA HSN MAIO
The same RC
in the cell
Different RC
in the cell
Co-channel
cell
#
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