2GSM Radio Network Tuning_Handover (Day 2)

GSM Radio Network Tuning

Babak Kardel

Mehrdad Sedaghat

March 2008

Introduction

• Network Mode

• Operation In Idle Mode

• Operation In Active Mode

• Radio Resource Administration

4/8/2008GSM Radio Network Tuning Course2

DUAL BAND SPECIFIC PARAMETERS




Dual Band Cell (DBC), YesDual Band Cell (DBC), Yes

� When the option dual band is activated, all the cells under the dualband BSC

broadcast sysinfo 2ter in idle mode.

Early Classmark Sending (ESI), YesEarly Classmark Sending (ESI), Yes

� By default, the ESI is set to yes, even when the option Dualband is not

activated

� All the dualband phones send the CM3 IE to the network

� In the dedicated mode and if the mobile is Dualband, the Early classmark

sending procedure will be triggered that tells the BSC to add the system

information 5ter containing the frequencies of the other band to be measured

for this call

Multi Band Reporting (MBR), 1Multi Band Reporting (MBR), 1

� The network tells the mobile to report 1 frequency of the other band if it can

find any.Then the mobile will complete the report with frequencies of the

same band. If still less than 6 neighbors, the mobile tries to report

frequencies of the other band.



6.82 multiband cell reporting (MBR)

Q3 name: multiBandCellReporting

Modification: Online

Range: 0..3

MML default: 1

Description: With this parameter you define the number of adjacent cells

from the other frequency band that the MS will report in the RX level report.

Related command(s): EQM, EQO

Note: OPTIONAL (Dual Band GSM/DCS)

Multi Cell Reporting

• Multi_Cell_Rep : Number of neighbour cells the MS will report from each band

900

900 900

1800

1800

900 900

1800

900

1800 1800

1800

Measure 32

neighbours 6Report 6 best

measurements

Mobile can.....

3 3

1 5

1800 900

1800 900

Strongest


•EarlySendingIndication : The parameter defines the requirements

for an MS in sending the Classmark 3 in call setup phase to the

network.

• Range : Yes (Early classmark sending accepted) / No (Early

classmark sending is forbidden)

• Recommended value : Yes in a Dual Band network

BTS Parameters - 2



Q3 name: multiBandCell

Range: Y/N

MML default: Y for Dual Band cells

N for cells that do not belong to the frequency bands of the Dual

Band

Description: With this parameter you 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.

Related command(s): EQF, EQO

Note: OPTIONAL (Dual Band GSM/DCS)

adjacency on other band (DBC)

System Information MessagesSystem Information Messages

• Sys_Info Messages 2ter and 5ter tell the dual band MS about the adjacent cells allocated from the other

frequency band

• 2ter in idle mode• 5ter during a call

• Single band MS will ignore Sys_Info 2ter and 5ter

Idle mode

900Sys_Info_2

Sys_info_2bis

Sys_info_2ter

Sys_Info_2

Sys_info_2bis

1800 1800

1800

900

900 900

900

900 900

Single band MS Dual band MS


Dual Band Protocol


Multi-layer Dual Band Network


Call setup Strategy


Call setup with 900 Band

Traffic handover to 1800 Band

2G Type RXP

Macro 900 -105 dBm

Macro 1800 -84 dBm

Micro outdoor -80 dBm

Micro Metro -105 dBm

Micro indoor -105 dBm

C1 ( 900) = Rxl-RXP = -70-(-105) = 35

C1 ( 1800) = Rxl-RXP = -70-(-84) = 14

C1 (Micro outdoor) = Rxl-RXP = -70-(-80) = 10

C1 (Pico) = Rxl-RXP = -70-(-105) = 35

Handover



Synchronized Handover

• If source and target cells are controlled by the same BCF, these are

synchronized to each other.

• Thus the MS does not need timing advance information from the network.


Non Synchronized Handover

If original and target cells are controlled by different BCFs, the MS needs

timing advance information from the network. This is transferred by a socalled

physical info message.

To ensure a successful transmission, it can be repeated a certain number of

times. This is controlled by the parameter maxNumberOfRepetition

(NY1)(SEG)(5..35)(5).

Furthermore, there is a restricted time between the first handover access and the

last physical info message. This timer always is set to 320 ms, it is fixed in

GSM specifications. Usually any handover is a non synchronized

handover. The


Handover Failure

If the signalling timer mentioned above expires or the radio link within

the target cell cannot be established, the MS returns to the old cell

HANDOVER PROCESS Causes

Timing Advance

Adjacent Cells

Downlink Quality

Uplink Quality AV_RXQUAL_UL_HO

AV_RXQUAL_DL_HO

Downlink Level

Uplink Level AV_RXLEV_UL_HO

AV_RXLEV_DL_HO

AV_RANGE_HO

AV_RXLEV_NCELL(n)

QUALITY&

INTERFERENCE

QUALITY&

INTERFERENCE

LEVELLEVEL

DISTANCEDISTANCE

PERIODICCHECKS

UMBRELLAUMBRELLA

POWER BUDGETPOWER BUDGET

IMPERATIVE HO

CHANNEL ADMINISTRATIONCHANNEL ADMINISTRATION

DIRECTED RETRYDIRECTED RETRY

THRESHOLD COMPARISON

RAPID FIELD DROPRAPID FIELD DROP

Others:

Intelligent Underlay Overlay

Traffic Reason

……….

MS SPEEDMS SPEED

MS Speed AV_MS_SPEED

upper layer (macro)

same layer (serving

layer)

lower layer (micro)

HANDOVER PROCESSmultilayer networks

N (not in use)

Parameter

adjacentCellLayer(ACL)


Handover Parameters


Target Cell Selection

If handover shall be carried out, a suitable target cell must be found. The

standard selection process uses as criteria the traffic loads, priorities

and RX levels of the adjacent cells.

Standard Selection• First of all, the traffic load of all adjacent cells is verified. If it exceeds the

threshold defined by the parameter (the unit is %) btsLoadThreshold

(BLT)(SEG)(0..100)(70), the cell is overloaded.

• Next the cell priorities are considered. These are defined by the

parameter hoPriorityLevel (PRI)(ADJC)(0..7)(3)

• If a cell is overloaded, the priority is reduced by a certain value which is

defined by the parameter hoLoadFactor (OF)(ADJC)(0..7)(1).

• Now the cells are ranked according their corrected priority. If two cells

have the same priority, they are ranked according their RX level.


Source Target PRI OF ACL SL AUCL

Macro 900 Macro 900 3 1 Same

- 95

dBm - 47dBm

Macro 900 Macro 1800 4 1 Lower

- 84

dBm - 80dBm

Macro 900 Micro outdoor 4 1 Lower

- 80

dBm - 75dBm

Macro 900

Micro

Metro&indoor 4 1 Same

- 95

dBm - 47dBm


Handover Parameters



Macro 900 Macro 900 3 1 Same - 95 dBm

-

47dBm

Macro 900 Macro 1800 4 1 Lower - 84 dBm

-

80dBm

Macro 900 Micro outdoor 4 1 Lower - 80 dBm

-

75dBm

Macro 900

Micro

Metro&indoor 4 1 Same - 95 dBm

-

47dBm



Macro 1800 Macro 900 3 1 Upper

- 95

dBm

-

47dBm

Macro 1800 Macro 1800 4 1 Same

- 84

dBm

-

47dBm

Macro 1800 Micro outdoor 4 1 Lower

- 75

dBm

-

75dBm

Macro 1800

Micro

Metro&indoor 4 1 Same

- 95

dBm

-

47dBm


Handover Execution

After a target cell has been found, the BSC tries to move the MS to it. To

avoid repetitive handovers or handover attempts in case of a failure,

certain time limits can be set by the parameters minIntBetweenHOReq

(MIH)(HOC)(0..31)(5) and minIntBetweenUnsuccHOAttempt

(MIU)(HOC)(0..31)(3) (the unit is s).


MIH : The first parameter sets the minimum time between two handovers

related to the same connection.

MIU : The second one indicates the time the MS has to wait after an

unsuccessful handover attempt, before it can try a handover again.

Further important time scales are controlled by the parameters

hoPeriodPBGT (HPP)(HOC)(0..63)(6) and hoPeriodUmbrella

(HPU)(HOC)(0..63)(6) (the unit is SACCH periods). These indicate the

time interval between consecutive estimations of the RX levels of the

adjacent cells for power budget and umbrella handover.


handover period power budget (HPP)

GSM reference: No ref.

Q3 name: hoPeriodPBGT


Range: 0..63

MML default: 6 (SACCH Periods)


Handover Parameters


Handover :

1- periodic Handover

1-1 : power budget Handover

1-2 : Umberla Handover

2- trigger Handover

2-1 : Interference

2-2 : Quality ( rxlevel adj > rxlev source + QMRG)

2-3 : Level (rxlev > SL , rxlevel adj > rxlev source + LMRG)


Ranking

The condition has to be fulfilled by any kind of handover, except the

umbrella handover

(1a) AV_RXLEV_NCELL (n) > rxLevMinCell (n) (SL)

. The condition has to be fulfilled priodical After 6 SACCH (3S)

(1b) AV_RXLEV_NCELL (n) > hoLevelUmbrella (n) (AUCL)

The parameter hoLevelUmbrella (AUCL)(ADJC)(-110..-47)(-47) defines


(2a) PBGT > hoMarginPGBT(n) PMRG

PBGT =(AV_RXLEV_DL_HO - AV_RXLEV_NCELL (n))

For handover due to RX level or RX quality also the handover margins

for the RX level and the RX quality are used. This leads to the modified

Condition

(2b) PBGT > hoMarginLevel/Qual(n) (PMRG , QMRG)


rxLevMinCell (SL) (ADJC)(-110..-47)(-100) hoLevelUmbrella (AUCL) (ADJC)


Handover due to Interference


t1:

hoThresholdQualDL > 4

hoThresholdInterferenceDL > -85

N HO triggered (not triggering attempt counter)

AV_RXLEV_NCELL–AV_RXLEV_DL_HO < hoMarginQual (=0)

N No suitable target cell -> Intra HO not possible -> HO fail

(not triggering the failure counter)

t2:

hoThresholdQualDL > 4

hoThresholdInterferenceDL > -85

N HO triggered

AV_RXLEV_NCELL–AV_RXLEV_DL_HO > hoMarginQual (=0)

N HO successful


enable HO margin lev qual (MRGS)


Q3 name: enableHoMarginLevQual

Range: Y/N

MML default: Y

Description: With this parameter you define whether the handover margins

for

signal level and quality will be taken into account in the handover

decision algorithm.

Related command(s): EAM, EAO

Interference handover


HO preference order interference DL (HDL)


Q3 name: hoPreferenceOrderInterfDL

Range: INTER, INTRA

MML default: INTER

Description: With this parameter you define the order of preference between

intra-cell and inter-cell handovers when the cause of the handover

is downlink interference.

Related command(s): EEM, EEO

a network with frequency hopping. The preferred handover type is set by the parameter

hoPreferenceOrderInterDL/UL (HDL/HUL) (BSC) (INTER,INTRA) (INTER).

The intra cell handover must be enabled using the parameter

enableIntraHOInterDL/UL (EIH/EIC)(HOC)(Y/N)(Y).

Handover due to Interference


Handover Parameters


Now only inter cell handover is possible, so that the handover fails,

if no suitable adjacent cell can be found.


Handover Parameters


rxLevMinCell (SL) (ADJC)(-110..-47)(-100) hoLevelUmbrella (AUCL) (ADJC)


Rxlev sourse < LDR OR LUR


Handover Parameters


threshold level uplink Rx level (LUR), Px (LUP), Nx(LUN)

Q3 name: hoThresholdsLevUL


Range: Rx level: -110..-47 (dBm)

Px: 1..32

Nx: 1..32

MML default: Rx level: -95

Px: 1

Nx: 1

Description: The parameters compare the averaged values of signal strength

uplink measurements for triggering the handover process.

Px: Number of averages that have to be upper/lower than the

threshold.

Nx: Number of averages that have to be taken into account when

making a handover decision.

Related command(s): EHC, EHO, EHS


Handover Parameters


Pure Power Budget Handover

This kind of handover is executed, if an adjacent cell offers a better power budget than the

serving cell, even if the averaged measurements for the serving cell do not exceed a threshold


enable power budget handover (EPB)

Q3 name: enablePwrBudgetHandover

Range: Y/N

MML default: Y

Description: With this parameter you indicate whether the BTS power

budget

handover control is enabled.

Related command(s): EHC, EHG, EHO


Handover Parameters


handover period power budget (HPP)

Q3 name: hoPeriodPBGT

Range: 0..63

MML default: 6 (SACCH Periods)

Description: With this parameter you define the interval between power budget

handover threshold comparisons.

Related command(s): EHC, EHG, EHO


This kind of handover is used for multi layer networks, especially for

such ones with macro and micro cells. Its purpose is to move the MS to

a suitable layer in dependence on its power class. Umbrella handover

must be enabled by setting the parameter enableUmbrellaHandover

(EUM)(HOC)(Y/N)(N) to Y. Than the RX levels of the adjacent cells are

checked periodically, according the value of the parameter hoPeriodUmbrella

Pure Umbrella Handover


1. Than the RX levels of the adjacent cells are

checked periodically, according the value of the parameter HPU(6SACCH)

2. RXLEV ADJ > AUCL

3. Better target selection

4. Algoritm pri,of,rlev adj

5. Rxlev adj > rxlev serv + LMRG

Condition of Umberella Handover


After the ranking of the adjacent cells, further conditions must be

checked. First the average signal level AV_RXLEV_NCELL is

considered, which must follow the condition

(1a) AV_RXLEV_NCELL (n) > rxLevMinCell (n) (SL)

(1b) AV_RXLEV_NCELL (n) > hoLevelUmbrella (n) (AUCL)

The parameter hoLevelUmbrella (AUCL)(ADJC)(-110..-47)(-47) defines

the minimum signal level to be allowed for an umbrella adjacent cell.


Handover Parameters


� All Types: 33 dbm

Handover Parameters



Handover Parameters


General Parameters

� All Types: 80


All Types: 0

General Parameters



General Parameters


� All types: 1

General Parameters

Power Control



• In the dedicated mode, both the BTS and the MS transmit with a power

as low as possible for the following reasons.

• On the uplink, the power consumption of each MS is decreased and

thus a longer service time for the rechargeable battery is achieved.

• Both on the uplink and downlink interference is reduced, so that the

network capacity and the spectral efficiency are improved.

This power control is carried out independently for uplink and downlink,

and also independently for each call.


Power Control Motivation

Power Control Parameters

2GSM Radio Network Tuning_Handover (Day 2)

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