explain m07 - 1 capacity planning
DESCRIPTION
Capacity PlanningTRANSCRIPT
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1 NOKIA 6-90204/ CAPACITY PLANNING/ v 1.0
CapacityCapacityPlanningPlanning
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Objectives
9 DESCRIBE TRAFFIC THEORY PRINCIPLES
9 CALCULATE CAPACITY OF DIFFERENT CONFIGURATIONS
9 DESCRIBE SIGNALLING CHANNELS AND CALCULATE SIGNALLING CAPACITY
9 DESCRIBE MAIN FEATURES OF CAPACITY ENHANCEMENT
At the end of this module you will be able to
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Content of Capacity Planning
9 TRAFFIC
9 SIGNALLING
9 CAPACITY ENHANCEMENTS
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Capacity Planning
9 TRAFFIC9 SIGNALLING9 CAPACITY ENHANCEMENTS
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TrafficTraffic Estimations
Estimate number of subscribers over time Long-term predictions Numbers available from marketing people?
Expected traffic load per subscriber Different subscriber segments? Expected behaviour of user segments
Particular phone habits of subscribers e.g. mainly heavy indoor usage Phoning while in traffic jams?
Busy hour conditions Time of day Traffic patterns
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TrafficTraffic Patterns
Traffic is not evenly spread across the day (or week)
Dimensioning must be able to cope with peak loads busy hour is typically twice the average hour load
0102030405060708090
100
0 2 4 6 8 10 12 14 16 18 20 22 24 hr
%peak timeoff-peak
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Cell loaddt
12 12.2 12.4 12.6 12.8 130
2
4
6
8The cell load
Time / hours
N
u
m
b
e
r
o
f
r
e
s
e
r
v
e
d
t
i
m
e
s
l
o
t
s
.
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M potential customers
m available resourcesM >> m
Problem: many customers, limited number of resources
How many resources do we need to satisfy the demand?
Trunking Basics
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Trunking Trunking Effect
Trunking increases effective usage of limited resources When we increase the traffic, we may not need that many new lines
Main parameter: accepted blocking probability
Blocking depends on Number of available resources Traffic statistical distribution
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time
CH 1CH 2CH 3CH 4
CH ...CH 5
CH n-2CH n-1CH n
Offered newtraffic
Trunking Trunking Effect
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ErlangDefinition
Erlang is the unit of traffic Definition
2 formulas Erlang B: for systems that support no queuing Erlang C: for systems that support queuing
Seconds 3600)()( Erlangs timeonconversatiaveragehourpercallsx =
Agner Krarup Erlang (1878-1929)
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Erlang Erlang Formulas
Erlang B No queuing: blocked calls are dropped Depends on call lengths & statistical distribution of calls Applicable in mobile systems (e.g. air interface)
Erlang C Queuing Applicable in trunking systems
=
=
M
i
i
k
k
i
kp
0!/
!/
=
+=> 1
0 !1!
)0(Pr C
k
kC
C
kA
CACA
Adelayob
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Blocking Probability Blocking ProbabilityChannels 1% 2% 3% 5% Channels 1% 2% 3% 5%
1 0,01 0,02 0,03 0,05 21 12,80 14,00 14,90 16,202 0,15 0,22 0,28 0,38 22 13,70 14,90 15,80 17,103 0,46 0,60 0,72 0,90 23 14,50 15,80 16,70 18,104 0,87 1,09 1,26 1,52 24 15,30 16,60 17,60 19,005 1,36 1,66 1,88 2,22 25 16,10 17,50 18,50 20,006 1,91 2,28 2,54 2,96 26 17,00 18,40 19,40 20,907 2,50 2,95 3,25 3,75 27 17,80 19,30 20,30 21,908 3,13 3,63 3,99 4,54 28 18,60 20,20 21,20 22,909 3,78 4,34 4,75 5,37 29 19,50 21,00 22,10 23,80
10 4,46 5,08 5,53 6,22 30 20,30 21,90 23,10 24,8011 5,16 5,84 6,33 7,08 31 21,20 22,80 24,00 25,8012 5,88 6,61 7,14 7,95 32 22,00 23,70 24,90 26,7013 6,61 7,40 7,97 8,83 33 22,90 24,60 25,80 27,7014 7,35 8,20 8,80 9,73 34 23,80 25,50 26,80 28,7015 8,11 9,01 9,65 10,60 35 24,60 26,40 27,70 29,7016 8,88 9,83 10,50 11,50 36 25,50 27,30 28,60 30,7017 9,65 10,70 11,40 12,50 37 26,40 28,30 29,60 31,6018 10,40 11,50 12,20 13,40 38 27,30 29,20 30,50 32,6019 11,20 12,30 13,10 14,30 39 28,10 30,10 31,50 33,6020 12,00 13,20 14,00 15,20 40 29,00 31,00 32,40 34,60
Erlang Erlang B Table
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Cell CapacityTraffic
Traffic capacity of a cell is determined by the number of available traffic timeslots
Trunking effect gives significant gains
TCH
SDCCH
BCCH/CCCH
TRX 1 1 2 3 4 5 6 7BCCH + CCCH 0,5 0,5 0,5 0,5 0,5 0,5 1 1SDCCH 1,5 0,5 1,5 1,5 2,5 2,5 3 3TCH 6 7 14 22 29 37 44 52Erl (2% blocking) 2,27 2,93 8,20 14,89 21,04 28,25 34,68 42,12
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Capacity Planning
9 TRAFFIC9 SIGNALLING9 CAPACITY ENHANCEMENTS
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Logical ChannelsDefinitions
TDMA Frame = 8 Time Slots (0.577 ms each)
Physical Channel = 1 TS of the TDMA Frame on 1 specific carrier
Logical Channel = the "purpose" a physical channel is used for
0 0
TDMA frame 4.615 msBURST PERIOD
0 7 0
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0 7
TDMA frame 4.615 ms
26 Multiframe = 120 ms 51 Multiframe 235 msTCH SIGN.0 1 2 24 25 0 1 2 49 50
Hyperframe = 2048 Superframes 3.5 h
Superframe = 26x51 or 51x26 Multiframes= 6.120 sec
Logical ChannelsStructure
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Same in GSM900 and GSM1800
FCH
Traffic Channels(TCH)
TCH/9.6FTCH/ 4.8F, HTCH/ 2.4F, H
Dedicated Channels(DCH)
Broadcast Channel(BCH)
Control ChannelsCommon ControlChannel (CCCH)
SCH BCCH(Sys Info)
TCH/FAGCH RACH SDCCH FACCH/ Bm
FACCH/ Lm
TCH/HPCH
Common Channels(CCH)
Logical Channels
SACCH
Logical ChannelsOverview of Logical Channels
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Logical ChannelsBroadcast Channels (BCH)
Frequency Correction Channel (FCCH) Unmodulated carrier: like a flag for the MS which enables it to find the frequency
among several TRXs
Synchronisation Channel (SCH) Contains the Base Station Identity Code (BSIC) and a reduced TDMA frame
number
Broadcast Control Channel (BCCH) Contains detailed network and cell specific information as: Frequencies,
Frequency hopping sequence, Channel combination, Paging groups, Information on neighbour cells
Careful frequency plan needed BCCH is not allowed to involve in FH, PC
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Logical ChannelsCommon Control Channels (CCCH)
Paging Channel (PCH) It is broadcast by all the BTSs of a Location Area in the case of a mobile
terminated call
Random Access Channel (RACH) It is used by the mobile station in order to initiate a transaction, or as a response
to a PCH
Access Grant Channel (AGCH) Answer to the RACH. Used to assign a mobile a SDCCH
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Logical ChannelsDedicated Channels (DCH)
Stand Alone Dedicated Control Channel (SDCCH) System signalling: call set-up, authentication, location update, assignment of
traffic channels and transmission of SMS
Slow Associated Control Channel (SACCH) Transmits measurement reports (UL) Power control, time alignment, short messages (DL)
Fast Associated Control Channel (FACCH) Mainly used for handover signalling It is mapped onto a TCH and replaces 20 ms of speech
Traffic Channels (TCH) Transfer user speech or data, which can be either in the form of Half rate traffic
(6.5 kbit/s) or Full rate traffic (13 kbit/s).
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FCCHSCH
SDCCH
PCH
AGCH
BCCH
CCCH
Common Channels
Dedicated Channels
Logical ChannelsDownlink
SACCHFACCH
SDCCH
TCH/F
TCH/H
DCCH
TCH
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RACH CCCHCommon Channels
SDCCHSACCH
FACCH
TCH/F
TCH/H
DCCH
TCH
Dedicated Channels
Logical ChannelsUplink
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Search for frequency correction burst FCCHSearch for synchronisation sequence SCHRead system informations BCCH
Listen for paging PCHSend access burst RACHWait for signalling channel allocation AGCHCall setup SDCCH
FACCHTraffic channel is assigned TCHConversation TCHCall release FACCH
idle mode
'off' state
dedicatedmode
idle mode
Logical ChannelsUse
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Beware of "home-made" bottlenecks
Logical ChannelsMapping - 1 Example
Example of mapping: combined CCCH/SDCCH/4 configuration
Downlink 51 TDMA frames = 235 ms
1. 2. 3. 4.
f s bb b b c fc fc s c c c c cc c c fc fs t t t t tt t t f ft t t t tt t t fs fs s s s ss s ss i
t t tt r r s fs ss s s s r r rr r r rs fr r r r r rr r r r fr r r r tr t t tr ft t t r tr t tt t
Uplink 51 TDMA frames = 235 ms
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Mainly realised by Stand-alone Dedicated Control CHannel (SDCCH)
SDCCH is mainly used in 5 cases: Call set-up SMS Location updates Emergency call Call re-establishment
SDCCH channel is key in achieving successful & efficient call set-up
Cell CapacitySignalling
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Cell CapacitySDCCH Configurations
TS0 of BCCH TRX always for BCCH + CCCH
TS0 may be configured to carry DCCH
SDCCH channels may be configured in any other TS. Convention (but not law!) is to put it on TS1
2 basic configurations Combined Non-combined
Combined configuration
0 7
ts0=bcch/sdcch/4/pch/agch
Non-combined configuration
0 7
ts0=bcch/pch/agchts1=sdcch/8
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Cell CapacitySDCCH Dimensioning
Efficient network design is required to achieve 2 goals An appropriate signalling dimensioning strategy, on a cell per cell basis An appropriate upgrade philosophy
SDDCH channels may be dimensioned in 3 ways On a cell per cell basis On a generic macro layer (not linked to macro/ micro cell layer definitions) On both of the above
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1 TRX and 7 Traffic channels means that There can be 7 simultaneous GSM data or speech calls
The total traffic over a hour period (=busy hour) is 2.5 Erl and 1% of call attempts is blocked
Extra capacity of 64% (= (7-2.5)/7) is needed to guarantee 1% blocking
(compare to the situation of 2 TRX => trunking effect!!)
1 TRX and 1 signalling channel means that All signalling channels (BCCH, PCH, AGCH, SDCCH) are sent on the 1st time slot
PCH and SDCCH capacities are the possible bottlenecks!
Capacity Planning Conclusion: Traffic and Signalling Channels
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Traffic channel capacity need is calculated / estimated
1. Based on the average traffic per subscriber (= 25 mErl = 90 s) and number of subscribers (250 Subs) and the total traffic need = 250 Subs x 25 mErl/Subs = 6.25Erl
2. Next the required number of traffic channels will be found from the Erlang-B table based on the quality criteria that is usually 1% blocking in GSM.
3. Erlang-B shows that 13 channels give 6.61 Erl @ 1% blocking which exceeds the capacity demand 6.25 Erl.
4. Next it can be noted that 2 TRX equals 14 TCHs and 2 SCHs (= 7.35 Erl = 6.25 + 1.1 extra capacity for the future).
5. 2 TRX will be implemented to the cell!
Capacity Planning Example: to estimate the Service for Subscribers
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Capacity Planning
9 TRAFFIC9 SIGNALLING9 CAPACITY ENHANCEMENTS
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COVERAGE BUILDING
CAPACITY
TIME
ADDING TRX, CELL SPLITTING
NOKIA INTELLIGENT CAPACITY
DUAL BAND
INDOOR
MICROCELLULAR
NOKIA SOFT CAPACITY,
FREQUENCY HOPPING
SUBS
CRIB
ER
GROW
TH
IntroductionCapacity Evolution Scenarios
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Measure for network spectral efficiency: Erl/ (MHz * sq.km)
A function of Bandwidth Frequency efficiency of technology Frequency re-use Cell sizes Trunking gains
Frq. hoppingFrq. hopping
DTXDTX
DirectedRetry
DirectedRetry
PowerControl
PowerControl
IUOIUO
Half-rateHalf-rate
Use all available BSS featuresbefore going into microcells
Loaddistribution
Loaddistribution
Trafficreason HO
Trafficreason HO
multiple cellcoverage
multiple cellcoverage
IntroductionNetwork Capacity
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Large Cells2 .. 30 km
Small Cells1.. 5 km
Microcells100m.. 1 km
Indoor cells10m .. 100 m
Layered networkMacro cells
IntroductionCell Size Evolution
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Macro cell
Micro cell
Micro cellIndoor cell
IntroductionLayered Network
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Ways to increase capacity Increase spectrum More bandwidth: up to the authorities, not in operators control Decrease cell Area Microcellular solution: larger number of sites; very expensive Reduce reuse factor Intelligent Underlay Overlay, Frequency Hopping (software capacity): investments in new sites can be delayed
Network Capacity SpectrumChannel Bandwidth Cell Size useFactor C I
Re ( / )
IntroductionFactors
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EXPLAIN Software Capacity
IUO FH IFH
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IUOBasics
Intelligent Underlay-Overlay implements a 2-layer network by using different RuFs
Conventional RuF is applied to regular layer (coverage) Aggressive RuF is used in super layer (capacity)
IUO is a Nokia feature but works with any mobile
Can be combined with other concepts, e.g. microcells
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Super layer (RuF = e.g. 7)
Regular layer (reuse = 12)
Super layer (RuF = e.g. 7)
Regular layer (reuse = 12)Regular layer (RuF = e.g. 12) Regular layer (RuF = e.g. 12)
Service region of super layer is controlled by interference
Calls are handed over from super layer to regular layer when interference becomes excessive
The super reuse frequencies are intended to serve MS close to the BTS
Regular frequency is used when the MS is further away from the BTS
IUOFeature Description
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IUOThe Functionality
Call set-up and inter-cell HO always to regular TRX
C/I is constantly calculated while call continues according to IUO algorithm
If C/I is better than good_C/I_threshold, the call is handed over to super layer If C/I decreases below bad_C/I_threshold, the call is handed back to regular layer
The intelligence of IUO is in the dynamic measurement of interference of every MS
Call is always kept under affordable conditions
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IUOExample
Measured server, C0 = -75 dBmMeasured interferer, I0 = -90 dBm
Ratio between server and interferer = (C0/I0)linear = (C0I0)dB = 15 dB
Defined conditions for handover:good_C/I_threshold = 14 dB bad_C/I_threshold = 11 dB
the call is handed over to super layer!
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IUOResults
Normal network Reuse 12
3 TRXs/cell
Capacity: 14,9 Erl/cell
IUO network Reuse 12 in regular layer
Reuse 6 in super layer
2 regular + 2 super TRXs/cell
Capacity: 19,7 Erl/cell
Available bandwidth 7,2 MHz (=36 channels)
Capacity gain of more than 30 %
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IUOIn Practice
Use a separate band for super layer Easier to maintain an overview Manual allocation also possible
Do not use adjacent channel in the same cell If adjacent channel has to be used on the same site
Interference free area reduced Quality not affected (C/I control)
Finding a frequency on super layer is easier than on regular layer Generate interferer lists for co-channel and adjacent channel
Manually time consuming
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What is Frequency Hopping?
Changing the carrier frequency in the radio link between mobile station and base station during the connection.
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FHBasics
Frequency Hopping is a sequential change of carrier frequency on the radio link between BS and MS
It averages the interference (interference diversity) and Minimizes the impact of fading (frequency diversity)
This quality improvement allows a tighter RuF And a bigger RuF means an enhanced capacity
It is a standardised feature it is supported by all mobilesFrequency
Time
F1
F2
F3
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BRTSL 0 1 2 3 4 5 6 7
TRX-1
TRX-2
TRX-3
TRX-4
f1 B = BCCH timeslot. It does not hop.
f2
f3
f4
Time slot 0 of TRX-2,-3,-4 hop over f2,f3,f4.
Time slots 1...7 of all TRXshop over (f1,f2,f3,f4).
The TRXs operate at fixed frequencies: consecutive bursts in each time slot are switched through different TRXs
The 1st time slot of the BCCH TRX is not allowed to hop
The number of frequencies to hop over is determined by the number ofTRXs (biggest limitation!)
FHBase-Band Frequency Hopping
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BTRX-1
Non-BCCH TRXs are hopping overthe MA-list (f1,f2,f3,...,fn) attached to the cell.
TRX-2
B = BCCH timeslot. TRX does not hop.
f1,f2,f3,fn
f1,f2,f3,fn
. . . .
All the TRXs except the BCCH TRX change their frequency for every TDMA frame
Thus the BCCH TRX doesnt hop at all
The number of frequencies to hop over is limited to 63, which is the maximum length of the Mobile Allocation (MA) list
FHSynthesised Frequency Hopping
BB-FH is feasible with large configurationsRF-FH is viable with smaller configurations
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Issues in Frequency Hopping
Frequency and interference diversity gains? Gain vs. reuse BB or RF FH? Cyclic or random sequence? Channel separation? Frequency allocation strategy? Minimum Effective Reuses? The Best Frequency Allocation reuse Maximum frequency load? PC / HO gain with FH? PC / HO parameters? Support of planning and optimisation tools? KPIs vs. subjective speech quality
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FH ImplementationFH Implementation
MSC
PSTN
BB-FH F1(+ BCCH)
F2F3
Dig. RF
TRX-3
TRX-1
RF-FH
F1, F2, F3
Dig. RF
TRX-1
TRX-2
BSCTCSM
BCCH
Frequency
Time
F1F2F3
MS does not seeany difference
BB-FH is feasible with large configurations RF-FH is viable with all configurations
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Average TRXs/cell : 3.3
Site Ce ll TRX countA 1 2
2 3B 1 4C 1 4
2 43 3
D 1 32 43 2
E 1 32 4
F 1 42 33 4
G 1 42 3
HoppingTRXs
1233322312332332
Average frequency load 7.4 % (max. 9.9 %) OK
Average frequency load 7.4 % (max. 9.9 %) OK
21 frequencies reserved for non-BCCH TRXs
21 frequencies reserved for non-BCCH TRXs
Effective reuse = 21 frequencies / 2.4 hopping TRXs per cell = 8.8 OKEffective reuse = 21 frequencies / 2.4 hopping TRXs per cell = 8.8 OK
Network layout:Network layout:
Average hopping TRXs/cell : 2.4
A B
C
DE
F G
1
2 11
1 1
1
1
2
2
2
2
2
3
3
3
Average frequency load: 7.4%
Single MA List Planning Case(1/1 Frequency allocation reuse)
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Site C
The sectors share the same HSN
The sectors share the same HSN
MAIO Offset determines the MAIO of the first hopping TRX in each sector
MAIO Offset determines the MAIO of the first hopping TRX in each sector
MAIOs for the rest of the hopping TRXs are determined by adding MAIO Step to the MAIO of the previous hopping TRX
MAIOs for the rest of the hopping TRXs are determined by adding MAIO Step to the MAIO of the previous hopping TRX
MAI value for each TDMA frame is calculated by BTS and MS by using HSN and TDMA frame number
MAI value for each TDMA frame is calculated by BTS and MS by using HSN and TDMA frame number
No co- or adjacent channel interference between sectors
No co- or adjacent channel interference between sectors
Transmitted frequencies for each TRX during each TDMA frame
Transmitted frequencies for each TRX during each TDMA frame
Single MA List Planning Case (1/1 Frequency allocation reuse) MAIO Example
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Combined FH + IUO High capacity gain
Average 70% increase compared to a conventional network
FH allows to use lower C/I threshold for IUO Same IUO RuF better traffic absorption Smaller IUO RuF more TRX/cell
BSS 7 offers FH on both layers at the same time; separate FH parameters for regular and super layers
RF FH is more flexible Can be used with smaller configurations More frequencies larger hopping gain
Evolution from FH or from IUO networks
IFHIntelligent Frequency Hopping
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EXPLAINMicrocell Planning
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More capacity required
Increase reuse
Make smaller cells
Microcells
Depends on: spectrum, environment, antenna location, reducing interference.
Make cells smaller, increase TRX => need better isolation between cells (reduce interference).
Increasing Capacity
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Microcells make sense just in urban areas
Use urban building structures to separate microcells
Keep microcell antennas well below the rooftop level
f 1
f 2 f 2
Microcell PlanningSite Location
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Hot Spots
Maximum capacity relief Targeted capacity First phase of capacity increment Frequency division does not affect
Continuous Layer
MetroSite BTSs are optimal for continuous layer within cluster area Additional capacity with:
cell splitting add TRXs
Capacity increment depends on frequency division
Microcell PlanningDifferent Approaches
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Paper map Bus stations, railway stations, hotels, shopping malls, etc
NMS performance data from an existing network Traffic, blocking, timing advance, average field strength
level Visualise by plotting the traffic data to a geographical
information system
Test transmitter Placed where hot spot is expected to be NetHawk measuring the abis of the serving cell
Microcell PlanningHot Spot Analysis
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27 ch Macro
9 ch Micro
Bulk Frequency Division
27 ch Macro
9 ch Micro
Interleaved Frequency Division
21 ch Macro
Multi Layer Super Reuse6 Sup
6 Sup
9 ch Micro
Microcell PlanningFrequency Division Strategy
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Bad quality samples on also high field strength levels Level distribution concentrated around -80 dBm
Network QualityMacrocells
-
100
300
500
700
900
1100
1300
1500
112 -109 -106 -103 -100 -97 -94 -91 -88 -85 -82 -79 -76 -73 -70 -67 -64 -61 -58 -55
LEVEL dBm
Bad QualityGood Quality
No Of Samples
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100
300
500
700
900
1100
1300
1500
-108 -105 -102-99 -96 -93 -90 -87 -84 -81 -78 -75 -72 -69 -66 -63 -60 -57
Level dBm
No Of Samples
Bad QualityGood Quality
Less bad quality samples with high field strength levels Number of high field strength samples increased
Network QualityMicrocells
-110-112
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CoverageBefore Microcells
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CoverageAfter Microcells
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CoverageStreet Channel Effect
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CoverageOvershooting Microcells
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Important Parameters for Microcells
BTS TX power
Antenna type Horizontal/Vertical beamwidth
Diversity configuration Space/Polarisation diversity
Frequency hopping Achievable gain
=> TARGET to BALANCE POWER BUDGET!
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Microcell Antennas
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Diversity in Microcellular Environment
Both space and polarisation diversity give good gain in microcellularenvironment
Large angular spread Random polarisation in NLOS
Diversity gain from frequency hopping small due to large coherence bandwidth
Interference averaging from frequency hopping
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Planning Tools for Microcells
Propagation prediction in microcell environment difficult Ray-tracing
Accurate information about surrounding environment needed Computationally very demanding
Measurements Use of test transmitters for site selection
Experience
Maps with high resolution
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Antenna Installation and Site Selection
Nominal site locations: According to area survey results Possible sites Propagation environment
BTS site configuration: BTS type TX power Sectorised sites TRX/cell
Antenna planning: Height Controlled coverage area
city structures antenna positioning
Low antennas instead of downtilting Antenna hiding Directional on walls Short cabling
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Antenna Installation Restrictions
Antenna height >10m Interference with other operators minimised BTS at low antenna heights might block receiving end of mobile at other
operators band (if difference above 40 dB ) If height lower, low transmission powers needed
Minimum distances due to EMR and EMC requirements Fresnels first zone should be free from obstacles
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EMC Safety Distance
Field strength versus distance
02468
1012141618
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
distance [m]
field strength[V/m]
0 dBi5 dBi7 dBi
Antenna gain [dBi]
Power: 1 W
Equipment Class: Immunity requirement:[V/m] RMS
Industrial 10Medical 3Medical in X-rayshielded environment
1
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72 NOKIA 6-90204/ CAPACITY PLANNING/ v 1.0
EXPLAIN Dual Band
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Dual Band means combining both GSM 900 and GSM 1800 (previously DCS) in the same network
GSM 900 and GSM 1800 are twins from the technical point of view
BSCGSM900/1800
GSM1800
GSM900/1800
GSM900
Dual Band NetworkBasics
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Capacity with GSM900 is limited: Subscriber growth Increased usage
Quality and capacity required: New services
WLL Wireless Office Data Services
Roaming: High revenue from roaming traffic
Dual Band NetworkBasics
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Traffic management First priority is to camp on GSM 1800 cells Transferring the Dual Band mobiles from GSM 900 cells to GSM 1800 cells is the
key process Setting special BSS parameters.
Planners should pay more attention to: Careful set of HO parameters Dualband network configuration LAC planning
Dual Band NetworkEffect on RNP
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Idle Mode Parameters
MS will calculate the C1 and C2 for the serving cell, every 5 s
MS will calculate the C1 and C2 for the six best neighbor cells,
every 5 s
Cell re-selection is needed if
Path Loss criterion C1 < 0 for cell camped on, for more than 5 seconds.
Any of the neighbors have a higher C1 after 5 seconds.
There is DL signaling failure.
The cell camped on has become barred.
There is a better cell in terms of C2 criterion
A random access attempt is still unsuccessful after "maxNumberRetransmission"
repetitions.
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C1 Algorithm
Radio Criteria
C1 = (A - Max(B,0))
A = Received Level Average - p1 B = p2 - Maximum RF Output Power of the Mobile Station p1 = rxLevelAccessMin Min. received level at the MS required for access to the system p2 = msTxPowerMaxCCH Max. Tx power level an MS may use when
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C2 Algorithm
Three different equation depending on penalty time value. If penalty time = 640 s, eq. 3 is in use, otherwise eq. 1 and 2.
1) C2 = C1 + cellReselectOffset temporaryOffset T penaltyTime
OR3) C2 = C1 cellReselectOffset, when penaltyTime = 11111(640s)
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C1/C2 Parameter Example Microcells
High RxLevAccessMin, -85/-90 dBm High CellReselectOffset, +20 dB Temporary offset 0 dB Penalty time NOT 640!! When cell above RxLevAccessMin, high (permanent) positive offset
Macrocells
RxLevAccessMin -105 dBm Penalty time = 640 CellReselectOffset 10 dB Decreases individual macrocell range by CellReselectOffset (if needed) Affects on GPRS cell selection!!!!!
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80 NOKIA 6-90204/ CAPACITY PLANNING/ v 1.0
LAC/BSC Borders Typically BSC and LAC areas are compact and bounded to
geographical location Microcells connected to same BSC with surrounding macrocells Compact BSC areas enable the effect use of Nokia features e.g.
AMH and traffic reason HO Intra BSC HO success rate better than Inter BSC HO success
rate Better candidate evaluation in Intra BSC HO
Optimised LAC borders decrease signalling load User mobility Highways and railroads Geographical areas
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Dual Band Network Same LAC and BSC
MSC
BSCa BSCb
GSM900
GSM1800
GSM900
GSM1800
GSM900
GSM1800
GSM900
GSM1800
LACa LACb
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Exercises / Questions
9 If you need to provide capacity for 20 Erlangs, 2 % blocking, how many TRXs do you need?
9 How many TRXs do you need to provide capacity for 10 Erlangs, 1 % blocking?9 How many subscribers can you serve with 2 TRX/cell, 1% blocking, with average
usage 20 mErl?
9 How many cells would you therefore need to give capacity for Helsinki area (49.2 % penetration, population 1 million)?
9 In China the average usage is 30 mErl. How many subscribers can you serve with 2 TRX/cell (1% blocking)?
9 In a small town A, with 1000 residents, the collected statistic data shows that the average air-time in busy hour is 90 seconds. If we want to cover this town by onecell, how many TRXs do we need to achieve the blocking probability of 1%?
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References
1. W.C.Y. Lee, Mobile Communications Design Fundamentals, John Wiley & Sons, 1993.
2. J. Lempiinen, M. Manninen, Radio Interface System Planningfor GSM/GPRS/UMTS, Kluwer Academic Publishers 2001.