Modul 5 bss parameter

GSM-GPRS Operation
BSS Parameter
Module 5

2
Outline
 BSS Parameters Structure
 BTS Parameters
 MS Mode
 Idle Mode
 Cell Selection
 Cell Reselection
 Dedicated Mode
 Handover
 Power Control
 BSC parameters
kris.sujatmoko@gmail.com

GSM-GPRS Operation
BSS Parameters
BTS Parameters
BSC Parameters

4
BSS Parameters Structure

5
BSS Parameters Structure (2)
 Base Station Controller (BSC)
 The BSC object contains BSC-specific radio network data.
 BCCH Allocation Frequency List (BA)
 The BA object contains data for building the BCCH allocation.
 Mobile Allocation Frequency List (MA)
 The MA object contains data for building the mobile allocation for RF
hopping.
 Base Control Function (BCF)
 The BCF object contains data that is specific for the O&M functions of the
BTS.
 Base Transceiver Station (BTS)
 The BTS object contains BTS-specific radio network data.
 Handover Control (HOC)
 The handover control object contains parameters which control the handover
procedure.

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BSS Parameters Structure (3)
 Power Control (POC)
 The power control object contains parameters which control the power
control procedure.
 Adjacent Cell (ADJC)
 The adjacent cell object contains a description of the adjacent cell of the
BTS.
 Transceiver (TRX)
 The TRX object contains TRX-specific data.
 Radio Time Slot (RTSL)
 The radio time slot object contains parameters for the physical radio time
slot.
 Frequency Hopping System (FHS)
 The frequency hopping system object contains hopping parameters for the
BTS.

GSM-GPRS Operation
BTS Parameters

8
BTS - Parameter

GSM-GPRS Operation
Parameter Related To Idle Mode

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MS Mode
Search for Frequency Correction Burst
Search for Synchronisation sequence
Read System Informations
listen for Paging
send Access burst
wait for signalling channel allocation
Call setup
traffic channel is assigned
Conversation
Call release
FCCH
SCH
BCCH
PCH
RACH
AGCH
SDCCH
FACCH
TCH
FACCH
idle mode
“off” state
dedicated
mode
idle mode

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Idle Mode – Cell Selection
 Radio constraints:
 The MS uses a "path loss criterion" parameter C1 to
determine whether a cell is suitable to camp on [GSM
03.22]
 C1 depends on 4 parameters:
 Received signal level (suitably averaged)
 The parameter rxLevAccessMin, which is broadcast on the
BCCH, and is related to the minimum signal that the
operator wants the network to receive when being initially
accessed by an MS
 The parameter msTxPwrMaxCCH, which is also broadcast
on the BCCH, and is the maximum power that an MS may
use when initially accessing the network
 The maximum power of the MS.

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Idle Mode – Cell Selection (2)
 Path loss criterion parameter C1 used for cell
selection and reselection is defined by :
 C1 = (A - Max(B,0))
 where
 A = Received Level Average - rxLevAccessMin
 B = msTxPwrMaxCCH – P
 Except for the class 3 (4 watts) DCS 1 800 MS
where :
 B = msTxPwrMaxCCH + POWER OFFSET - P

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 rxLevAccessMin = Minimum received level at the
MS required for access to the system.
 msTxPwrMaxCCH = Maximum TX power level an
MS may use when accessing the system until
otherwise commanded.
 POWER OFFSET = The power offset to be used in
conjunction with the MS TXPWR MAX CCH
parameter by the class 3 DCS 1 800 MS.
 P = Maximum RF output power of the MS.

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 Procedure

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 Example
 C1(cell_A) = AV_RXLEV - rxLevAccessMin - Max(0,
msTxPwrMaxCCH – max output power of MS)
 C1(cell_A) = -80dBm – (-100dBm) – max(0, 36dBm – 33dBm)
 C1(cell_A) = 17 > 0
 C1(cell_B) = -82dBm – (-105dBm) – max(0, 33dBm – 33dBm)
 C1(cell_B) = 23 > C1(cell_A)
 Thus MS camps on cell_B

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Idle Mode – Cell Reselection
 Why C2 ?
 Cell Prioritisation
 As a means of encouraging MSs to select some
suitable cells in preference to others
 Example:
 In dualband network--to give different priorities for
different band
 In multilayer--to give priority to microcell for slow
moving traffic
 Any other special case where specific cell
required higher priority than the rest

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Idle Mode – Cell Reselection (2)
 How the MS knows?
 cellReselectOffset, penaltyTime,
temporaryOffset are cell reselection parameters
 These parameters are broadcast on the cell
BCCH when cellReselectparamInd is set to yes
 Cell Reselection Strategy:
 Positive offset--encourage MSs to select that cell
 Negative offset--discourage MSs to select that
cell for the duration penaltyTime period

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Idle Mode – Cell Reselection (3)
 MS will calculate the C1 and C2 for the
serving cell, every 5 s
 MS will calculate the C1 and C2 for the
neighbour cells, every 5 s
 Cell re-selection is needed if :
 Path Loss criterion C1 < 0 for cell camped on, for
more than 5 sec
 There is DL signaling failure
 The cell camped on has been barred
 The is a better cell in terms of C2 criterion

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Idle Mode – Cell Reselection With C2 (1)

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 For penaltyTime = 640 seconds,
 C2 = C1 – cellReselectOffset
 For penaltyTime < 640 seconds,
 C2 = C1 + cellReselectOffset – temporaryOffset for T <=
penaltyTime
 C2 = C1 + cellReselectOffset for T > penaltyTime

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Cell Selection Case Study
 A dualband network, 1800 layer is preferred during
call setup
 Why?
 To relieve blocking in 900 layer
 To absorb traffic from 900 layer
 Strategy?
 Use C2 parameters
 How?
 Minimising massive BSS parameters change in the existing
900 layer
 Traffic is increase in a control manner
 Only 1800 layer required BSS parameter change

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Cell Selection Case Study (2)
 How to set?
 Cell Reselection Parameters activated in 1800
layer
 900 layer remain unchanged--operation as normal
 What value?
 reselectOffset is initial set at low value during
initial stage and further optimised in later stage

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 The Rationale?
 cellReselectParamInd--YES
 No C2 parameters will be broadcast on cell BCCH if this
parameter is not turned on
 cellReselectOffset = 8 dB
 The 1800 layer having a C2 of 8 dB higher than C1 of 900
after the penaltyTime expires
 PenaltyTime = 20 seconds
 Assume 1800 cell radius 400 meters
 Fast moving traffic speed 80 km/h
 A MS takes approximately 20 seconds to cross a cell 1800
cell
 Because the initial coverage for 1800 is not contiguous, the
fast moving traffic is not allowed to move to 1800 layer

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 The Rationale?
 PenaltyTime = 20 seconds
 During the penaltyTime period, the fast moving MS
will set up call on 900 layer
 Slow moving traffic will set up call on 1800 layer
 temporaryOffset = 10 dB
 This value should be set higher than
cellReselectOffset value
 In order to have a negative offset (with reference to
1800 C1 value) during the penaltyTime period

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 The Rationale?
 cellBarQualify = NO
 Cell selection priority is normal status
 If set to YES, cellBarred parameter can be overwrite
and cell selection priority will become low

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 The Scenario:
 GSM900: rxLevAvg = -75dBm; rxLevAccessMin =
-97dBm
 DCS1800: rxLevAvg = -80dBm; rxLevAccessMin =
-95dBm
 For serving GSM900 cell,
 C2 = C1 = rxLev – rxLevAccessMin – max
([msTxPowerMaxCCH - max RF output of MS], 0)
 C1 = -75dBm – (-97dBm) – max([33 – 33], 0)
 C1 = 22 dB

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 The Scenario:
 For non-serving DCS1800 cell,
 C1 = rxLev – rxLevAccessMin – max
([msTxPowerMaxCCH – maxRF output of MS], 0)
 C1 = -80dBm – (-95dBm) – max([30 – 30], 0)
 C1 = 15 dB
 During the penalty time period of 20 seconds;
before the penalty time expires
 C2 = C1 + cellReselectOffset – temporaryOffset = 15 + 8 –10
= 13dB < C2 for GSM900 cell (= 22dB)
 MS stays in GSM900 layer during this period

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 The Scenario:
 After the penalty time period of 20 seconds
expires
 C2 = C1 + cellReselectOffset = 15 + 8 = 23dB > C2
for GSM900 cell (= 22dB)
 MS reselects DCS1800 layer after penalty time
expires

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Idle Mode – Cell Reselection Hysteresis
 Cell Reselection Hysteresis
 MS is moving in a border area between location areas
 MS might repeatedly change between cell of different location
areas
 Each change of location area requires a location update
 LU causes
 Causes heavy signalling load
 Increases risk of paging message being lost
 To prevent this, cell reselect hysteresis is used
 How this parameter works?
 A cell in a different location area is only selected if it is “better”
than all the cell in the current LA by at least the value of
cellReselectHysteresis
 In term of path loss criterion

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Idle Mode – Cell Reselection Hysteresis(2)
 Cell Reselection Hysteresis
 What value to set?
 Typical value is 6~8 dB
 Example:
 A static class 4 MS camping on cell 1 in idle
mode.
 The MS monitor the BCCH of cell 1 and cell 2 and
measures the following levels
 rxLevAvg = -80dBm in cell 1
 rxLevAvg = -86dBm from neighbour cell 2
 The following parameters are set:

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 Does the MS perform cell reselect?
 If cell 1 and cell 2 belong to the same LA
 If the cell 1 and cell 2 belong to different LAs

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 What are the conditions?
 For the same LA:
 C1 (cell 2) > C1 (cell 1)
 For the different LA:
 C1 (cell 2) > C1 (cell 1) + cellReselectHysteresis
 C1 (cell 1) = rxLevAvg – rxLevAccessMin – max
([msTxPowerMaxCCH – max RF output of MS], 0)
 C1 (cell 1) = -80dBm – (-100dBm) – max([36 – 33], 0)
 C1 (cell 1) = 17 dB
 C1 (cell 2) = rxLevAvg – rxLevAccessMin – max
([msTxPowerMaxCCH – max RF output of MS], 0)
 C1 (cell 2) = -84dBm – (-104dBm) – max([33 – 33], 0)
 C1 (cell 2) = 20 dB

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 C1 (cell 2) = 20 dB > C1 (cell 1) = 17 dB
 For the same LA:
 C1 (cell 2) > C1 (cell 1)
 cell reselection
 For the different LA:
 C1 (cell 2) < C1 (cell 1) + cellReselectHysteresis
 No cell reselection

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GSM-GPRS Operation
Parameter Related To Dedicated
Mode

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Dedicated Mode
 Handover
 Power Control

GSM-GPRS Operation
Handover Parameters

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Handover Parameter

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Handover Design (1)
 Handover definition:
 A mechanism that transfers an ongoing call from
one cell to another as a user moves through a
coverage area of a GSM system
 Trends:
 Smaller cells to meet the demands for increased
capacity  number of cell boundary crossing
increase
 Impact:
 Network Resource: switching load
 Delay  Quality of Service

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Handover Design (2)
 Network resource:
 Minimising number of HO  minimising switching
load
 QoS :
 Minimising delay  minimises co-channel
interference
 Challenge  optimium HO parameters
settings using the existing HO algorithm so
that the perceived QoS does not degrade

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Handover Design (3) – Guidelines
 General HO Design Guidelines
 HO design involves setting of:
 HO parameters
 GenHandoverRequestMessage in BSC parameter
 MsTxPwrMax in BTS parameter
 PcLowerThresholdLevDL/UL in power control parameter
 hoMargin in adjacency parameter
 HO objectives:
 maintenance of connection in case of cell change
(movement)
 channel change in case of severe disturbance
(interference)
 design of cell borders and radio network structure

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Handover Design (4)
 HO is divided into several sub processes

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Handover Design (5)

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Handover Design (6)
 HO Sub Processes Flow

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Handover Design (7)
 Handover performance metrics used to evaluate HO
performance:
 Call blocking probability -the probability that a new call
attempt is blocked
 Handover blocking probability - the probability that a
handover attempt is blocked
 Handover probability - the probability that, while
communicating with a particular cell, an ongoing call
requires a handover before the call terminates. This metric
translates into the average number of handovers per call
 Call dropping probability - the probability that a call
terminates due to a handover failure. This metric can be
derived directly from the handover blocking probability and
the handover probability

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Handover Design (8)
 Probability of an unnecessary handover - the probability
that a handover is stimulated by a particular handover
algorithm when the existing radio link is still adequate
 Rate of handover - the number of handovers per unit time.
Combined with the average call duration, it is possible to
determine the average number of handovers per call, and
thus the handover probability.
 Duration of interruption - the length of time during a
handover for which the mobile terminal is in communication
with neither base station. This metric is heavily dependent
on the particular network topology and the scope of the
handover
 Delay -the distance thc mobile moves from the point at
which the handover should occur to the point at which it
does

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Handover Design (9)

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Handover Design (10)
 Relative signal strength:
 HO triggered at point A
 Unnecessary HO when the serving cell signal is
still adequate
 Relative signal strength with threshold:
 If threshold set at T1, same as relative signal
strength trigger point A
 If threshold set at T2, HO is delayed, occurs at
point B
 If threshold set at T3, delay too long# may result
in dropped call and suffers co-channel
interference

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 Relative signal strength with margin:
 Triggered only when the target cell signal strength is
stronger than the serving cell by a margin h, point C
 Prevent “ping-pong” effect  repeated HO between two
cells due to rapid fluctuations in received signal from both
cells
 Unnecessary HO may occur if the serving cell is sufficiently
strong
 Relative signal strength with margin and threshold
 Triggered when the serving cell signal drop below
threshold and the target cell signal is stronger by a margin
 Occurs at point C if the threshold is set at T1 and T2
 Occurs at point D if threshold is set at T3

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 HO initiation criteria based on 4 variables:
 Averaging window size
 Measurement value weighting
 Threshold level
 Margin

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 Parameter to enable different type Of HO :

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Handover Design (14) – HO Priority
 RR-radio resource:
 target cells are ranked according to radio link
properties and
 priority levels
 Imperative:
 target cells are ranked according to radio link
properties
 priority levels are not used

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Handover Design (15) – HO Priority

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Handover Causes And Decisions (1)

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Handover Causes And Decisions (2)

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Handover Regions (1) – Threshold Setting

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Handover Regions (2) – Handover Level Threshold

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Handover Flow

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Handover Scenario (1)
 HO Thresholds:
 Set to meet the optimum HO performance
 2 Scenarios to be considered:
 Noise Limited
 Interference Limited
 MS behaves differently in the above 2
scenarios

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Handover Scenario (2)
 HO Thresholds parameters and values

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Handover – Noise Limited Scenario
 Noise Limited Scenario
 Large cell with low traffic load, specially in rural area
 rxLev at cell border is just a few dB higher than receiver
reference sensitivity
 Main Handover criteria is level criteria
 Receiver Reference Sensitivity according to GSM 05.05

67
Handover – Noise Limited Scenario (2)
 Noise Limited Scenario
 Imperative to set the optimum values to avoid
“forward-back” HO
 General guideline:
 rxLevMinCell – hoThresholdsLevDL = level hysteresis
> 0 (+4dB..10dB)
 rxLevMinCell > hoThresholdsLevDL + level hysteresis
and
 hoThresholdsLev > MS sensitivity + 3 dB
 only DL is mentioned for illustration; in actual
parameters planning, both UL/DL

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Handover – Interference Limited Scenario (1)
 Interference Limited Scenario
 Small cell with high traffic load, especially in urban area
 rxLev at cell border is significant higher than the receiver
sensitivity
 C/I is not much higher than the reference interference level
 Main Handover criteria is power budget criteria
 Receiver Reference Interference Level according to
GSM 05.05

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 Interference Limited Scenario
 Better cell criteria should be the main HO criteria
 Power budget HO guarantee that the MS is
served by the cell with lowest path loss
 Thus, higher chance for power control to reduce
interference

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 hoMarginPBGT (cell1 cell2) + hoMarginPBGT (cell2 cell1) =
PBGT hysteresis > 0 (+6dB..12dB)
 Normally hoMarginPBGT is set symmetrically
 Low hoMarginPBGT values  high “forward-backward” HO rate
 High hoMarginPBGT values  low “forward-backward” HO rate
 Unsymmetrical hoMarginPBGT value is set to adapt cell service
area to traffic load
 Increases one cell service area and at the same time reducing its
corresponding neighbour cell service area

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 Power Budget Hysteresis

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 Symmetrical hoMarginPBGT = 6dB: point x and a
 Unsymmetrical hoMarginPBGT (cell1  cell2) = 9dB
and hoMarginPBGT (cell2  cell1) = 3dB
 PBGT hysteresis = 12dB
 Point y and b
 Cell2 service area reduced from point x to y
 Cell1 service area increased from point a to b

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Other HO Types And Features

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Umbrella Handover
 The Objective:
 To serve the target traffic more efficiently
 Umbrella HO has priority over power budget HO
 The mapping table for gsmMacrocellThreshold
and gsmMicrocellThreshold

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Umbrella Handover (2)
 What does the table mean?
 Example:
 If you set the gsmMocrocellThreshold** smaller than the MS
class maximum output power, the MS is only allowed to HO to
macrocell
 At the same cell, its adjacency parameter msTxPwrMaxCell(n)
should be set smaller than gsmMacrocellThreshold
Note ** gsmMacrocellThreshold is a BSC parameter, it need additional adjacency
parameter to control per adjacency basis

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Umbrella HO Algorithm

83

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 When AV_RXLEV_NCELL(n) = -75dBm
 A MS class 4 in dedicated mode is in macrocell
 1’ AV_RXLEV_NCELL(n) > hoLevUmbrella(n)
 (MS class 4 = 33dBm) <= (gsmMicrocellThrsehold =
33dBm) and
 (MsTxPwrMaxCell(n) = 33dBm) <=
(gsmMicrocellThreshold = 33dBm)
 Umbrella HO to microcell occurs
 When MS is at microcell border, av_rxLev = -98dBm and
av_rxLev_cell(n) = - 82dBm
 1. av_RxLevUL/DL < hoThresholdsLevUL/DL
 2. AV_RXLEV_NCELL(n) – av_RxLevDL –
(btsTxPwrMax – BTS_TXPWR) > hoMarginLev(n)

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 When MS is at microcell border, av_rxLev =
-98dBm and AV_RXLEV_NCELL(n) = -82dBm
 1. av_RxLevDL < hoThresholdsLevDL -98 dBm
< -95 dBm
 2. AV_RXLEV_NCELL(n) – av_RxLevDL –
(btsTxPwrMax – BTS_TXPWR) >
hoMarginLev(n) -82 – (-98) – (0 – 0) = 16 dB > 3
dB
 HO due to level

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Handover Due To Fast/Slow MS Speed
 2 possibilities:
 MS speed in relation to cell size
 Measured MS speed
 Both need AdjCellLayer(n) and hoLevelUmbrella(n)
parameters **
Note ** see detail HO due to fast/slow moving MS algorithm

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Handover Due To Fast/Slow MS Speed Algorithm

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Handover Due To Fast/Slow MS Speed (2)

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 MS speed in relation to cell size
 Parameters are set per adjacency basis
 From Macro to micro
 Counter for each adjacent microcell
 +2 for each measurement >= rxLevMinCell(n)
 –1 for each measurement < rxLevMinCell(n) or no measurement

90
 How to set fastMovingThreshold?
 if microcell radius is about 200 meters, taking 2.5 m/s as slow
moving limit; thus
 total time to cross the microcell is 200/2.5 = 80 seconds
 if averaingWindowSizeAdjCell is set to 6 SACCH, this equal to
about 3 seconds for each measurement
 it take 5 seconds to decode an adjacent cell BSIC, thus total
measurements is (5 + 3* measurements) = 80 seconds
 thus total measurements are (80-5)/3 = 25 number of
measurements
 the fastMovingThreshold = 25*2 = 50 (because counter
increases by 2 for each measurement)

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 When the counter > fastMovingThreshold =
50; and
 AV_RXLEV_NCELL(n) > hoLevUmbrella (n)
= -80dBm
 Umbrella HO due to slow moving MS
 ? what is the speed limit if
fastMovingThreshold = 24 for a cell radius of
205 meters ?
 24 = 12 measurements; 12*3 + 5 = 41 seconds;
200 meters/ 41 = 4.8 m/s

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 Measured MS speed
 Related parameters:
 Slow moving MS to lower layer adjacent cells (lowerSpeedLimit)
 Fast moving MS to upper layer adjacent cells (upperSpeedLimit)
 One unit value of lowerSpeedLimit upperSpeedLimit equal to
2km/h

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Handover – MS-BTS Distance
 To prevent MS from exceeding cell boundary
 Related Parameters:
 msDistanceBehaviour
 0 : Release immediately
 1 - 60 : Release after certain time 1 - 60 s, try imperative
handover during that time
 255 : No release, only imperative handover attempt

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Handover – MS-BTS Distance (2)
 msDistanceHoThresholdParam
 1 step size correlates to 550 meters
 this parameter value depends on the designed
cell radius
 if the value is set to 2, the maximum cell radius for
the MS is 2*550 = 1100meters before the
imperative HO is attempted in the 30 seconds
period set in the parameter
msDistanceBehaviour; if HO execution fails; the
call will be terminated
 enableMSDistanceProcess
 Set to yes to activate this feature

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Traffic Reason Handover
 TRHO effectively
 reduces the service area of a congested cell and
 Increases the service area of the under-utilised
target cells
 HO is triggered with amhTrhopPbgtMargin
instead of hoMarginPBGT
 Target cell minimum access level should be set higher
to avoid bad DL rxQual after HO
 amhTrhoPbgtMargin should be much lower than
hoMarginPBGT

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TRHO Algorithm

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Traffic Reason Handover (2) – TRHO Parameter
 BSC Parameter
 BTS Parameter

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Traffic Reason Handover (3) – TRHO Parameter
 Adjacency Parameters
 amhTrhoPbgtMargin(n) should be set lower
than hoMarginPBGT
 trhoTargetLevel(n) should be set higher than
rxLevMinCell(n) to ensure only good adjacent
cell is used

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Traffic Reason Handover (4)

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Directed Retry (DR)
 A transition (handover) from a SDCCH in one
cell to a TCH in another cell during call setup
due to unavailability of an empty TCH within
the first cell
 To control traffic distribution between cells to
avoid a call rejection
 Can be used for both MOC and MTC
 Setting guidelines:
 drThreshold should be higher than rxLevMinCell;
else the improved target cell selection criteria will
be ignored even drMethod = 1

102
Directed Retry (2) – Parameter Related

103
Directed Retry (2) - Algorithm

104
Directed Retry (3)
 Example

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Directed Retry (4)
 the BSC cannot start the target cell evaluation within 2
seconds period from the start of directed retry procedure
is triggered
 after 2 seconds, the BSC continues to evaluate the
target cell until 6 seconds period expires and if no
suitable target cells are available, directed retry will be
aborted **
 ** MS need at least 5 seconds to decode the
neighbouring BSIC. Thus minimum
maxTimeLimitDirectedRetry should be 5 seconds
 cellType will be set based on the macro or micro cell in
the network

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Intelligent Directed Retry (IDR)

107
Queuing
 Queuing Parameters :
 If both queuePriorityUsed and
msPriorityUsedInQueueing are used, queuePriorityUsed
will be dominant factor
 TimeLimitCall should be shorter than
(maxTimeLimitDirectedRetry +
minTimeLimitDirectedRetry)

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Queuing (2)
 MaxQueueLength: The parameter specifies the number of call
attempts and handover attempts that can wait for a TCH release
in a BTS. The value is the percentage of TRXs times 8
 For a 4 TRXs cell, maxQueueLength = 50%, 50%*4*8 = 16 call
attempts and HO attempts can wait for a TCH release in a cell
 queuingPriorityHandover should be set higher than
queuingPriorityCall
 queuingPriorityCall should be set higher than
queuePriorityNonUrgentHo
 Non urgent HO: power budget HO, umbrella HO, slow moving
MS HO and traffic reason HO
 Urgent HO: quality and level reason HO

109
Queuing And Directed Retry

110
Queuing And Directed Retry (2)
 Reference to Figure in previous slide,
 Timing Diagram for Queuing and Directed
Retry
 the call setup will not be able to handover to
directed retry if the timeLimitCall is longer
than maxTimeDirectedRetry and the call will
be terminated when the timeLimitCall expires

GSM-GPRS Operation
Power Control parameters

112
Power Control (1)

113
Power Control (2)
 Objective:
 To adapt the transmit power of MS & BTS to
reception conditions

114
Power Control (3)
 Power control advantages:
 reduction in MS average power consumption
 reduction in overall network interference level
 Power control is applied separately:
 for uplink and downlink
 each logical channel
 Power control is not applied to:
 downlink burst using the BCCH frequency

115
Power Control (4) - Algorithm

116
Power Control (5) - Regions

117
Power Control (6) - Implementation

118
Power Control (7)
 Measurement preprocessing for power control:
 for each call
 UL and DL received signal level
 UL and DL received signal quality
 The measurements are made over each SACCH
multiframe
 104 TDMA frames (480 ms) for a TCH
 102 TDMA frames (470,8 ms) for an SDCCH
 every SACCH multiframe, MS sends in the next
SDCCH message block the DL measurement on
dedicated channel via the Measurement report
message to the serving TRX of the BTS
 serving TRX performs UL measurements on the
dedicated channel

119
Power Control (8) – General POC Parameters

120
Power Control (9) – Step Size

121
Power Control (10) – Step Size Or Variable

122
Power Control (11) – POC Range

123
Power Control (12) – POC Range
 If optimumRxLevUL feature is activated; i.e. set to –85
dBm;
 alternative power control algorithm for MS will be used
 pwrDecrLimitBand0
 pwrdecrQualFactor

124
Power Control (13) - Power Decrement Band
Setting

125
Setting
 TRX parameter: optimumRxLevUL = -85 dBm
 POC parameter:
 pcUpperThresholdQualUL = 1
 pwrDecrLimitBand0 = 10 dB
 av_rxLev_UL = -80 dBm and av_rxQual_UL = 0
 Power reduction is MS is 10 dB

126
Setting

127
Power Control (16) - Power Decrement Band Setting
 TRX parameter: optimumRxLevUL = -85 dBm
 POC parameter:
 pcUpperThresholdQualUL = 1

128
 Averaging
 Weighting is used when DTX is activated in the network

129
 Weighting:
 Window size = 8, weighting = 2

130
Power Control (19) - Power Control Averaging
 PC Priority:
 PC due to Lower quality thresholds (UL and DL)
 PC due to Lower level thresholds (UL and DL)
 PC due to Upper quality thresholds (UL and DL)
 PC due to Upper level thresholds (UL and DL)

131
Power Control (19) - Threshold

132
Power Control (20) - Threshold
 Guideline:
 thresholds setting is imperative to avoid
undesirable ping pong effect of power control
 if the pcUpperThresholdsLev is set too low, power
down due to level at low rxlev will casue rxqual to
deteriorate and subsequently power up occurs
due to rxqual
 rxqual improvement will lead to power down due
to level again and the loop recurs

133
Power Control (21) - Regions

134
Power Control (22) - POC Threshold Values Example

135
Power Control (23) - MS Power Optimization
 MS Power Optimisation
 2 scenario:
 During call setup
 During handover
 Use the optimized MS output power to
reduce the uplink interference

136
 Without MS Power Optimisation, MS access the cell with maximum Tx
power as specified by msTxPwrMaxCCH
 During Call Setup:
 Related Parameters: per TRX
 Example:
 MS_TXPWR_ OPT = MsTxPwrMax - MAX ( 0, (RXLEV_UL
- OptimumRxLevUL) )
 When RXLEV_UL = -80dBm
 MS-TXPWR_OPT = 33 – max(0, (-80 + 85) = 28dBm
 compare to maximum power 33 dBm

137
 During Handover:
 Related Parameters: per Adjacency
 Indicates the optimum UL RF signal level after
Handover
 Only for intra-BSC HO
 When BSC calculates the optimized MS output
power, it presumes that the UL signal level is equal to
downlink signal level measured by MS
 If the DL is stronger than UL by 6 dB, msPwrOPtLevel
should be set 6 dB than the desired UL signal level

138
 During Handover:
 If AV_RXLEV_NCELL(n) = -75dBm, and Set
msPwrOptLevel = -80dBm
 MS_TXPWR_ OPT(n) = msTxPwrMax(n) - MAX ( 0,
(AV_RXLEV_NCELL(n) - msPwrOptLevel) )
 MS_TXPWR_ OPT(n) = 33 – max ( 0, (-75 + 80) = 28
dBm
 Thus MS uses 28 dBm output power instead of 33
dBm

139
Power Control And Handover Control
 Rule of thumb:
 POC should happen before HOC
 2 ways to make this happens
 Thresholds
 Averaging windows size
 RxLev Thresholds for POC > RxLev Thresholds for
HOC
 RxQual Thresholds for POC >= RxQual Thresholds
for HOC
 Window size (POC) <= window size (HOC)

140
Power Control And Handover Control (2)
 Rxlev timing diagram

141
Power Control And Handover Control (3) - Example
 RxLev Thresholds and window size:
 For UL (refer to the figure in previous slide)
 POC:
 pcUpperThresholdsLevDL = -75 dBm, px = 2, nx
= 3
 pcLowerThresholdsLevDL = -89 dBm , px = 2, nx
= 3
 HOC:
 hoThresholdsLevDL = -95 dBm, px = 3, nx = 4
 What these setting mean?

142
Power Control And Handover Control (4) - Example
 MS will power down if the 2 out of 3 av_RxLev_UL
measurement samples is better than –75dBm
 MS will power up if the 2 out of 3 av_RxLev_UL
measurement samples is worse than –89dBm
 If after powering up, the av_RxLev_UL is still lower than
–95dBm with measurement sample 3 out of 4, HO will
take place**
**Note: this happen when the MS is at the cell border and is
transmitting at the maximum power

143
 RxQual timing diagram

144
 POC And HO relationships

145
Power Control And Handover UL

146
Power Control And Handover UL (2)

147
Power Control And Handover DL

148
Power Control And Handover DL (2)

GSM-GPRS Operation
TRX parameters

150
TRX Parameter

151
TRX Parameters

152
TRX parameters (2)
 preferredBCCHMark:
 BCCH is automatically configure to its original state after the TRX
fault has been eliminated
 Benefit of using TRX output power within a common cell
 optimumRxLevUL:
 Used in conjunction with POC –MS power optimisation
 ETRX:
 Extended TRX
 A cell radius of an ordinary cell is 35 km.
 Extended TRX can serve up to about 70 km
 The implementation is based on one-BCCH (broadcast control
channel) and two-TRX (transceiver) solution.
 The normal coverage area is served with different TRXs than the
extended coverage area.

153
TRX Parameters (3)
 ETRX:
 Timing of the TRXs which serve the extended
coverage area is delayed so that they can serve
the area beyond 35 km
 Effectively 2 cell radius for a single cell
 floatingMode:
 TRX can be dynamically switched to operate in
any of the sectors within a BTS
 Automatically replaces a faulty BCCH TRX

GSM-GPRS Operation
Adjacency Parameters

155
Adjacency Parameters

156
Adjacency Parameters (2)
 Used to control dedicated mode MS for HO purpose
 These parameters play only the support role to HO or
any other optional features

157

158
 hoTargetArea:
 indicates whether the adjacent cell is an extended range
cell or a normal cell
 If the adjacent cell is an extended cell, it determines which
TRX (extended or normal) of the adjacent cell from where
the BSC will allocates a TCH during an intra-BSC HO
attempt
 0 = Normal cell
 1 = Extended range cell, a TCH is allocated from a normal
TRX
 2 = Extended range cell, a TCH is allocated from an
extended range TRX.
 3 = Extended range cell, a TCH is allocated from a TRX
whose type (extended range or normal range) is the same
as the type of the serving TRX.

159
Dualband Parameters
 multibandCell
 define whether adjacent cells with a BCCH allocated from a
different frequency band than the serving cell BCCH are
taken into account in handovers and in idle mode cell
selection or reselection
 earlySendingIndication
 accept or forbid the early sending of the MS Classmark 3
message in call setup phase to the network
 multiBandCellReporting
 define the number of adjacent cells from the other
frequency band that the MS will report in the RX level
report

GSM-GPRS Operation
MS Mobility Management

161
Mobility Management
 Dual-band MS:
 Idle mode
 Dedicated mode
 Objectives:
 To manage traffic more efficiently
 To increase call setup success rate
 Strategies:
 Accommodate both single and dualband MS in both dedicated
and idle mode with existing network configuration and traffic
volume
 How to design?
 Using existing BSS parameters
 Dualband parameters

162
MM (2) – Idle Mode

163
MM (3) – Case Study
 Case study as follows:
 Network access preference:
 GSM900 layer
 DCS1800 layer
 Justification?
 GSM900 is a contiguous coverage layer
 DCS1800 is a capacity relief layer
 How to design?
 Idle Mode:
 Make DCS1800 layer less attractive by setting negative
offset to C2
 Only singleband (1800) MS is allowed to access the
DCS1800 layer
 Dualband and singleband(900) access GSM900 layer

164
MM (4) – Dedicated Mode

165
MM (5) – Case Study
 Case study as follows:…continue
 Dedicated Mode:
 Depending on the cell traffic and cell
configuration
 HO preference:
 G900 to D1800 (negative power budget margin)
 D1800 to D1800 (normal power budget with
higher priority)
 G900 to G900 (normal power budget with lower
priority)
 D1800 to G900 (large positive power budget
margin)

166
MM (6)
 Case study as follows:…continue
 The good and the bad of this strategy
 Advantage:
 Simple parameter modification (only C2 required change
for idle mode MM)
 DCS1800 traffic load can be managed based on cell-by-
cell basis
 Disadvantage:
 GSM900 may suffer call setup blocking (both dualband and
G900 MS access network directly)
 High HO rate

167
MM (7) – Idle Mode

168
MM (8) – Dedicated Mode

169
Dual Band Network Operation
 Idle Mode For Dualband Mobile Management

170
MM (9)
 A dual-band multi-layer network design
 Design criteria:
 GSM band layer consideration
 Macro-micro layer consideration
 Idle mode preference:
 GSM900->DCS900
 Micro followed by macro for slow moving
 Macro followed by micro for fast moving
 Dedicated mode preference:
 DCS1800->GSM900

171
MM (10)
 A dual-band multi-layer network design…continue
 Network topology consideration
 Neighbour relationships
 Adjacency parameters set

GSM-GPRS Operation
BSC Parameters

173
BSC Parameters

174
BSC Parameters (2)
 Cell Definition For Multilayer Network

175
BSC Parameters (3) – Cell Definition
 How to set?
 MsTxPwrMaxCell(n) >= gsmMacrocellThreshold–
adjacent cell type is macrocell
 MsTxPwrMaxCell(n) <= gsmMicrocellThreshold–
adjacent cell type is microcell
 BSC Parameters:
 gsmMicrocellThreshold = 33 dBm
 gsmMacrocellThreshold = 35 dBm
 Cell Parameter:
 msTxPwrMax(n) = 33 dBm

176
BSC Parameters (4) – Cell Definition
 What these values mean?
 (MsTxPwrMax(n) = 33dBm) <= (gsmMicrocellThreshold
= 33dBm)
 the adjacent cell type is microcell

177
BSC Parameters (5) – MSC HO

178
 How to set disableIntHo?
 Set to YES – not all HO is controlled by MSC
 Only inter-BSC HO requires MSC
 Intra-BSC HO will not require MSC
 To reduce MSC load
 Set to NO - all HO is controlled by MSC

179
 How to set genHandoverRequestMessage?
 Typical values is 3
 3 preferred cells are included in the HANDOVER
REQUIRED message
 The message is sent from BSC to MSC
 Only for inter-BSC HO scenario

180
BSC Parameters (8) – Directed Retry
 How to set disableExtDr?
 Set to YES – external directed retry HO will not be
allowed
 Set to NO – external directed retry HO will be
allowed when it is necessary
 Inter-BSC directed retry HO will take place for cells at
the BSC boundary

181
BSC Parameters (9) – Handover Type
 How to set hoPreferenceOrderInterfDL?
 Set to inter – intercell HO is preferred when
HO is due to DL interference
 Set to intra - intracell HO is preferred when
HO is due to DL interference

182
 How to set msDistanceBehaviour?
 Action taken after timing advance has exceeded the
threshold
 Value = 255 – no channel release, only HO attempts
 Value = 0 – release channel immediately, no HO
attempts
 Value = 10
 HO attempt within 10 seconds after the timing advance has
been exceeded
 Channel will be released if HO does not succeed during the
10 seconds window period

183
 How to set rxLevBalance?
 This parameter is used for the purpose of
uplink interference level calculation
 Typical value = 6 dB

184
BSC Parameters (12) – MS Speed Detection
 How to set msSpeedC11?
 This parameter for MS speed related HO
 If you decide maximum MS speed for slow moving traffic is 20
km/h
 The value should be set to 10
 Any MS speed exceeds the 20 km/h threshold will be considered
fast moving traffic

185
BSC Parameters (13) – Advanced Multilayer
Handling

186
BSC Parameters (14) Advanced Multilayer Handling
 How to set amhUpperLoadThreshold?
 This parameter defines the maximum cell
traffic load
 When the the cell traffic load exceeds the
threshold, intra-BSC traffic reason HO will
occur
 Example: amhUpperLoadThreshold = 70%
 If the cell traffic load is 75%, Traffic Reason HO
will be initiated

187
 How to set amhLowerLoadThreshold?
 This parameter defines the minimum cell
traffic load
 If the traffic load of the serving cell does not
exceed the amhLowerLoadThreshold, the
IUO handover or the Direct Access to super-
reuse TRX are not allowed

188
 How to set amhMaxLoadOfTargetCell?
 This parameter defines the maximum
adjacent cell traffic load
 If the adjacent cell traffic load is below this
threshold, the cell can be the target for Traffic
Reason HO
 Example: amhMaxLoadOfTargetCell = 80%
 If the adjacent cell traffic load is 60%, this cell can
be the target cell for Traffic Reason HO

189
 How to set amhTrhoGuardTime?
 This parameter defines the guard time before
Handover back to original cell is allowed
 If set to 10 seconds
 BSC-controlled or MSC-controlled Traffic Reason
HO occurs
 During this 10 seconds period, HO back to the
original cell is NOT allowed
 Handover back to original cell can only be allowed
after the 10 seconds period expires

190
BSC Parameters (18) – Dynamic Hotspot
 What these parameters mean?
 badQualLimit:
 define the limit for bad signal quality in term of proportion of bad
samples in all samples in signal quality measurement.
 goodQualLimit:
 define the limit for good signal quality.
 The value of the parameter has to be equal to or smaller than the
value of the signal quality limit 2 (SQL2) parameter.

191
 sigQualLimit1:
 define the lower limit for adequate signal quality in adjacent
cells.
 the value of the parameter has to be equal to or smaller
than the value of the bad quality limit (BQL) parameter.
 sigQualLimit2:
 define the upper limit for adequate signal quality in
adjacent cells.
 The value of the parameter has to be equal to or smaller
than the value of the signal quality limit 1 (SQL1)
parameter.
 GQL<=SQL2<=SQL1<=BQL

192
 tchProbability1: define the probability of TCH
allocation when signal quality in the adjacent cell, x
signal quality limit 1 (SQL1) <= x < bad quality limit
(BQL) .
allocation when signal quality in the adjacent cell, y
signal quality limit 2 (SQL2) <= y < signal quality
limit 1 (SQL1) >= TCH probability 1 (TCP1)
parameter.
allocation when signal quality in the adjacent cell, z
good quality limit (GQL) <= z < signal quality limit 2
(SQL2). >= TCH probability 2 (TCP2) parameter.

193
 Operator defined probability table
 The probability is set by operator

194
BSC Parameters (22) – Dynamic Hotspot Example

195
BSC Parameters (23) – Dynamic Hotspot Example
 The probability to allocate TCH in cell A is 51%
 The probability to allocate TCH in cell B is 80%
 The average probability is 51%*80% = 40% < fixed reference = 50%
 Reject resource request

GSM-GPRS Operation
End of Section 5
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