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GSM Frequency Planning 101
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571572 580
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Prepared by Tarik Ouazzani
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Contents
I) Introduction : BCCH vs. TCH
II) Frequency Planning
Why do we use frequency planning?
Channel Numbering
Reuse Factor
C/III) BSIC Planning
Why do we use frequency planning?
BSIC Numbering
III) Neighbors List
IV) Frequency Hopping
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Frequency Planning
Part I
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Why d
owe use frequency planning?
Efficient use of the frequency spectrum
Minimize interference
Improvement in voice quality
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Uplink Vs D
ownlink
Radio tower Cell phone
DOWNLINK
UPLINK
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450 (Tetra): Being Introduced
GSM 850 : 2*25 MHz Bands, 20 MHz Duplex spacing, 125Carriers.
GSM 900 : 2*25 MHz Bands, 45 MHz Duplex spacing, 125Carriers.
DCS 1800 : 2*75 MHz Bands, 95 MHz Duplex spacing, 375Carriers.
PCS 1900 : 2*60 MHz Bands, 80 MHz Duplex spacing, 300 Carriers.
PCS
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Channel Numbering
GSM 900(n) = 890 MHz + (0.2 MHz) x n
(n) = (n) + 45 MHz
GSM 1800
(n) = 1,710 MHz + (0.2 MHz) x (n-511)
(n) = (n) + 95 MHz
GSM 1900
(n) = 1,850.2 MHz + (0.2 MHz) x (n-512)(n) = (n) + 80 MHz
1241 ee n
810512 ee n
885512 ee n
dF
dF
uF
uF
uF
dF
uF
uF
uF
uF
dF
= uplink frequency
= downlink frequency
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Channel Numbering
Block E: 1885-1890 and 1965-1970
The Channel Numbers : 586 to 611.
Fl(N)=1850.2+0.2*(N-512)
N=[(Fl(N)-1850.2)/0.2]+512
N=[(1885-1850.2)/0.2]+512=687
N=[(1889.8-1850.2)/0.2]+512=711
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Carrier Need to know which carriers are available in the project
Put the frequency range that the FCC allow
Band Channel Number
A 512-586
D 587-611
B 612-686
E 687-711
F 712-736
G 737-811
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Reuse Factor Low power transmitters to allow frequency reuse at much smaller
distances. Maximizing the number of times each channel may be reused in a
given geographic area is the key to an efficient cellular system design.
q= reuse factor
R= center-to-vertex distanceD= Co-channel separation
q= D/R
D=
i= along any chain of hexagons
j= counter clockwise turn
ijji 22
R
A
A
o60
i=3
j=2
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Reuse Factor (contd )
f2
f2
f3
f1
f1f3
f2
f3
f1
Frequency Reuse factor =
f2
f3
f1
3x9
f1
f3
f1
f2
f2f1
f3
f1
f3
f2
f2
f3
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Reuse Factor ( contd)
f1
f2
f3
f4
f1
f3
f4f2
4x12
f1
f2
f3
f4
f1
f3
f2f4
f2
f1
f3
f4
f1
f2
Frequency Reuse Factor =
f3
f4
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C/I Co-channel Interference
fo
Desired signal
Interfering signal
9 dB
F (MHz)
Power(dBm)
Between the cells having the same BCCH
More than 9 dB difference doesn't effect
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C/I (contd) Co-channel Interference example
515
515-70 dBm
A1
A2
dBI
C9u
9u
C= -70 dBm
79eI dBm
Lower or equal than 79 dBm is acceptable
[-79, -80,]
I
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C/I (contd) Adjacent Interference
fo Fo+200 KHz F ( MHz)
9 dB
Power( dBm)
Between the adjacent cells
Interfering signal can have signal level difference up to 9 dB
for the 1st Adjacent channel.
(for 1st Adjacent Interference)
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C/I (contd) 1st Adjacent Interference example
515
516
-70 dBm
A1
A2
dBI
C9u
9u
C= -70 dBm
61eI dBm
Lower or equal than 61 dBm is acceptable
[-61, -62,]
I
(for 1st Adjacent Interference)
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C/I (contd)
Relation Name Spacing ( kHz) Protection (dB )
Co-channel C/I 0 9
1 st adjacent channel C/A1 200 -9
2 nd adjacent channel C/A2 400 -41
3 rd adjacent channel C/A3 600 -49
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Block E Channels
Calculation for a BTS Configuration Of 2/2/2:
Reuse Factor N=4
Block E has 5 MHz = 25 Channels. (Channel 687 to 711).
687 used as a Guard Band.
A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3
BCCH 688 689 690 691 692 693 694 695 696 697 698 699
A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3
TCH 700 701 702 703 704 705 706 707 708 709 710 711
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Pattern N=4
f1
f4
f3
f2A1
C1
A2A3
D1
D2
D3
C2C3 B1
B2B3
688
690
692696
691
694
699
694698 689
693697
BCCH planning first, Then we match it with the TCH
Planning.
A B A B A B
B
A B A B A B
T
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Interference Table
List of all the Frequencies that can cause interferences for a cell.
Several steps are required:
Best Server
C/I plots
Drive test Data : RXQual (0 to 7) Need to be 0.
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Possible Interferences
690
694
698
689
693
697
691
695699
688
692
696
Adjacent
Interference
Adjacent
Interference
Adjacent
Interference
Site A Site C
Site BSite D
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Frequency Plan For 1 PatternBSC: TBD
National Color Code: 3
Site Id Orientation BCCH TCHSite A 0 688 700
120 692 704
240 696 708
Site B 0 689 701
120 693 705
240 697 709
Site C 0 690 702
120 694 706
240 698 710
Site D 0 690 703120 694 707
240 698 711
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Pattern N=4
f1
f2
f3
f4
f1
f3
f4f2
f1
f2
f3
f4
f1
f3
f2f4
f2
f1
f3
f4
f1
f2
f3
f4
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BSIC Planning
Part II
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BSIC BSIC: Base Transceiver Station Identity Code
used to distinguish neighboring base
stations two components: Network Color Code (NCC) Base Station Color Code (BCC) directly adjacent PLMN and BS must have
different colorcodes
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BSIC Allocation
BSIC=NCC+BCC
NCC : (0 to 7 ) predefined for a Carrier ( AWS can be 3 , VT 4)
BCC: (0 to 7 ) Planned by the RF Engineer.
Helps the mobile stations to distinguish between two neighboring
cells sharing the same BCCH
BSIC combination has to be unique for all cells that are defined in
the neighbor list.
The Mobile Recognize the BTS as it Neighbors or as the one it is
connecting to by the Combination BSIC+BCCH
BSIC=Base Station Identity Code
NCC= Network Color Code
BCC= Base Station Color Code
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BSIC Allocation
Rad i
t
rRad i
t
r
If a Mobile receives 2 same BCCH with the Same BSIC. It will be impossible for him
to make the difference between the 2 BTSs. ----> Drop Call
BSIC is the way the mobile make the difference between the 2 BTSs.
BCCH = A1
BSIC = 30
BCCH = A1
BSIC = 30
Radi
t
rRadi
t
r
BCCH = A1
BSIC = 30
BCCH = A1
BSIC = 31
Best Server
Same BSIC + Same BCCH = Drop Call
Different BSIC + Same BCCH = Call onthe best server (9 dB better)
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BSIC Plan
F1 30
f2
f3
f4
F1 31
f3
f4
f2
F1 34
f2
f3
f4
F1 35
f3
f2
f4
f2
F1 33
f3
f4
F1 32
f2
f3
f4
F1 36f2
f3
f4
F1 37
f3
f4
f2
f3
f4
F1 30
f2
f3
f4
Reuse of BSIC 30 Far Enough
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BSIC PlanBSC: TBD
National Color Code: 3
Site Id Orientation BSIC BCCH TCH
Site A 0 30 688 700
120 30 692 704240 30 696 708
Site B 0 31 689 701
120 31 693 705
240 31 697 709
Site C 0 32 690 702
120 32 694 706
240 32 698 710
Site D 0 32 690 703
120 32 694 707
240 32 698 711
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BSIC Plan For Every BSC
Optimization Purposes: you can check with this table what is the Interferer
BSIC Planning : Help Choosing the BSIC Available.
BCCH 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711
BSIC
30 Sit
1 Sit
2 Sit
3
31 Sit
1 Sit
2 Sit
3
32 Sit
1 Sit
2 Sit
3
33S
it
1 Sit
2 Sit
3
34
35
36
37
BSIC PLA FOR BSC XX
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Neighbors Planning
Part III
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Neighbors Planning Find ALL the possible HO
If one Neighbor is Missing ---> Possible Drop
Call
Put in the List the Maximum numbers of
Neighbors (most vendors have 20 neighbors in the
NL). Check Stats Monthly (BSC Dump).
When a HO occurs the mobile get a new NL from
the New Sector.
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Possible HO
Site A Site C
Site BSite D
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