irat presentation rev b_claro

IRAT(U2G and G2U)

1 - Vamos ativar os processos em Idle para toda a rede (2G->3G e 3G -> 2G)2 - Vamos ativar os processos com continuidade (HO-CS) somente no sentido 3G -> 2G para garantir continuidade de cobertura a partir da borda3 - Vamos ativar os processos com continuidade (HO-PS) nos dois sentidos somente nas células de borda

GSM_preferred GSM_preferred

GSMGSMGSMGSM GSM GSM GSMGSM GSM

UTRANGSMIdle modeConected mode

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IRAT (U2G and G2U)Email 14/08 - Claro

WCDMA and GSM are to be seen as complementary systems, where GSM contributes with a well built-out coverage, and WCDMA adds new services and higher bit-rates. Inter-working between these systems enables subscribers with IRAT capable terminals to reach WCDMA services on WCDMA while using GSM as a fallback access technology outside WCDMA coverage.

The IRAT handover and cell reselection between WCDMA <->GSM, reduces the number of dropped connections where WCDMA coverage is limited, border cells of the WCDMA coverage or larger coverage holes inside the WCDMA system.

Costs associated with IRAT:

• Compressed Mode (higher power usage or decreased Packet data throughput).• Increased drop risk with unnecessary start/stops of compressed mode.

With careful introduction of IRAT in the system the overall gain with IRAT handover is beneficial for the system performance.

IRAT (U2G and G2U)

IRAT (U2G and G2U)The IRAT function enables the operator to distribute the traffic between the GSMand the WCDMA systems, according to a pre-determined strategy.

The strategies described here are divided into three parts:• Idle mode,• Connected mode for CS services, • PS services

UE STATES AND TRANSITIONS FOR IRAT

IDLE MODE STRATEGY

A subscriber will camp and set up a call when both systems (GSM or WCDMA) are available. Idle mode parameter settings also steers the PS traffic behavior in the CELL_FACH state in WCDMA.

A proper setting of the idle mode parameters will reduce the number of unnecessary IRAT handovers and cell reselections and is the foundation for a good working inter-working system between 2G and 3G.

The main strategy:

Making subscribers camp in WCDMA whenever WCDMA coverage is available >> full advantage of the initial WCDMA coverage and its new services (ex: video call).

IDLE MODE STRATEGY

A UE in Idle mode or in CELL_FACH or URA_PCH will start to measure GSM neighbors:

1) Serving cell CPICH Ec/No is less or equal to the thresholds below:

Qqualmeas = qQualMin + sRatSearch = -18 + 4 = -14 dB- sRatSearch: CPICH Ec/N0 (Default: 4dB)- qQualMin: Min. required quality for selection criteria in the cell (SIB3 for the serving cell and SIB11 for adjacent cells)

OR2) Serving cell CPICH RSCP is less or equal to the thresholds below:

Qrxlevmeas = qRxLevMin + sHcsRat = -115 + 3 = -112 dBm- sHcsRat: Defined per cell (UE support for CR130 on 3GPP TS 25.304 Rel 5 is needed in order to trigger on this parameter); To disable this trigger: sHcsRat = -105 dB - qRxLevMin: Min. required signal strength for cell selection criteria in the cell.

IDLE MODE STRATEGY (U2G)

When measurements are started, the GSM cells are included in the cell ranking. The cells are ranked according to the R criteria, comparing signal strength:

R(serving) = Qmeas(s) + qHyst(s) (4dB)R(neighbor) = Qmeas(n) - qOffset1(s,n)

If a GSM cell is ranked as the strongest cell through the R criteria duringtreSelection, an IRAT cell reselection to GSM takes place.

The setting of qOffset1sn = 7 dB for GSM neighbors aims at making the RSCP signals from WCDMA cells and the RSSI signals from the GSM cells comparable in the ranking procedure.

IDLE MODE STRATEGY (U2G)

When the UE is camping in GSM, the decision when to start measurements onWCDMA is based on parameter QSI.

QSI = 7: Always make measurements on the WCDMA system (recomended in most cases) – To be used for Claro

QSI = 15: Not to measure on WCDMA and prolong UE standby time (If no WCDMA coverage exists)

QSI = 8-14: Make measurements on WCDMA when GSM signal strength RSSI is above a certain threshold

QSI = 0-6: : Make measurements on WCDMA when GSM signal strength RSSI is below a certain threshold.

IDLE MODE STRATEGY (G2U)

If the following criteria’s are fulfilled a Multi-RAT capable MS will reselect a suitable WCDMA cell (criteria must be fulfilled for 5 seconds):

1) CPICH Ec/No > FDDQMIN (Recommended = -12dB) • FDDQMIN > qQualMin + sRatSearch (U2G criteria: Def. -14dB) can prevent the UE for making cell reselection to a weak quality WCDMA cell, and to prevent too early cell reselection measurements on GSM.• An increase of FDDQMIN will make the UE camp longer in GSM before selecting WCDMA in idle mode and stay longer in GSM packet transfer mode.And2) CPICH RSCP > RLA(s+n) + FDDQOFF• RLA (Received Level Average): Average of the received signal levels measured in dBm for all monitored GSM frequencies in the BA list.• FDDQOFF = 0 will disable the criteria. A negative value must be set if cell reselection is to be possible when GSM coverage is good. Drawback: cell reselection to a weak WCDMA cell could be made when GSM coverage is moderate.


The parameter FDDRSCPMIN is a RSCP threshold parameter that is used in feature Combined Cell Reselection Triggering to WCDMA. This parameter threshold can also be used in the cell reselection criteria.

If the combined Ec/No and RSCP criteria.s are fulfilled a Multi-RAT capable MS will reselect a suitable WCDMA cell (criteria must be fulfilled for 5 seconds):

CPICH RSCP > RLA(s+n) + FDDQOFF (0)AndCPICH Ec/No > FDDQMIN (-12dB) – FDDQMINOFFAndCPICH RSCP > FDDRSCPMIN (-102dBm) - min((P_MAX-21 dBm), 3dB)

This new RSCP parameter however needs support of Release 5 or later of 3GPP 44.018 in the UE, otherwise it is not used.


GSM to UMTS (G2U) Parameter Entity1) Start/stop measurements QSI always, never or RSSI

2) CRS evaluation FDDQMIN Ec/No and FDDQOFF RSCP vs RSSI Comparsion

UMTS to GSM (U2G) Parameter Entity 1) Start/stop measurements sRatSearch Ec/No

or sHcsRat RSCP

2) CRS evaluation cell ranking RSCP vs. RSSI Comparsion

(qOffset1Sn)

The UE measures and makes the decision when to transfer

PS: (UE support for CR130 on 3GPP TS 25.304 Rel 5 is needed in order to trigger on RSCP)

IDLE MODE STRATEGY Inter-RAT Cell reselection

IDLE MODE STRATEGY Considerations

The main issue to monitor in idle mode performance is the unnecessary changes between the systems that results in ping-pong Location Area and Routing Area updates (increased processor load in the core network and it can also impact the paging success rate).

It is important to coordinate the parameter settings in both WCDMA and GSM to achieve the wanted inter system handover behavior.

The main strategy is to make sure that there is a delta in CPICH Ec/No between the thresholds in WCDMA and GSM. The minimum recommended delta in Ec/No is 2dB and is achieved by setting sRatSearch to 4 (-14 dB) and FDDQMIN to 5 (-12 dB).

Connected mode for CS services Strategy (IRAT HO)

CS connected mode strategy concerns the criteria for changing of systemwhen in connected mode (speech calls). This strategy is supported byconnected mode parameters, Service Based Handover to GSM and theDirected retry to GSM function for speech service.

Strategy: Avoid any unnecessary start of compressed mode usage in areas where the call can be kept in WCDMA for the major part of the cell, “WCDMA as far as possible”.

The IRAT handover should in the ideal case be used to save ongoing calls when the WCDMA coverage is getting poor and where there is GSM coverage to continue the call.

In the system the IRAT handover function for connected mode can be turned On/Off on a cell level, using the parameter hoType (GSM_PREFERRED, IF_PREFERRED or NONE).

Connected mode for CS services Strategy IRAT HO (U2G)

There are three cases:

• If all cells in the AS have hoType (or defaultHoType) set to "NONE" >> no IF or GSM HO attempts shall be done and no GSM or IF measurements shall be started.

• If at least one cell in the AS has hoType (or defaultHoType) set to "GSM_PREFERRED" and no cell in the AS has hoType (or defaultHoType) set to "IF_PREFERRED" >> preferred HO type is GSM.

• If at least one cell in the AS has hoType (or defaultHoType) setto "IF_PREFERRED" >> preferred HO type is IF. For more info onIFHO.

The activation of IRAT by hoType and defaultHoType should also be used to minimize GSM measurements and IRAT handover in the network.


Strategy: WCDMA as far as possible >> as long as the quality or signal level is above a certain level. When the UE moves into an area with deteriorating radio conditions: >> start measurements on GSM frequencies using compressed mode.The handover evaluation criteria are:

• Start of compresssed mode measurements:if any of these conditions fulfilled for best AS cellCPICH Ec/No < event 2d Ec/No threshold ORCPICH RSCP < event 2d RSCP threshold ORUeTxPower reaches max Tx Power event 6d

• Stop of compressed mode measurements:if all conditions below fulfilled for best AS cellCPICH Ec/No > event 2f Ec/No threshold ANDCPICH RSCP > event 2f RSCP threshold AND UeTxPower < event 6b threshold


Trigger of IRAT handover attempt:

if CPICH Ec/No 2d event triggered CPM (compressed mode)GSM RSSI with BSIC verified > gsmThresh3a andCPICH Ec/No < event 3a Ec/No threshold

if CPICH RSCP 2d event triggered CPM (compressed mode)GSM RSSI with BSIC verified > gsmThresh3a andCPICH RSCP < event 3a RSCP threshold

if Ue Tx power event 6d triggered CPM (compressed mode)GSM RSSI with BSIC verified > gsmThresh3a andCPICH RSCP < event 3a UE Tx Power 2 threshold

The strategy is implemented by setting the lowest possible parameter values without causing the connections to drop prior to a handover.


Connected mode for CS services Strategy U2G HO triggered by RSCP

When the UE is in the GSM connected mode, there are two different strategies when to handover to the WCDMA system. The strategy is determined by the parameters ISHOLEV, MRSL and QSC.

• QSC specifies when WCDMA measurements should be started.• ISHOLEV (percentage of idle TCH time slots) specifies the load level in GSM that has to be fulfilled before a handover is initiated.• MRSL is an Ec/No threshold for the measured CPICH.

The setting of MRSL is somewhat depending on what WCDMA triggering criterion that is chosen for event 2d and 3a.A sufficient high level on MRSL prevents ping-pong behavior, and the UEwill avoid getting into compressed mode immediately after being handed over to WCDMA.

Connected mode for CS services Strategy IRAT (G2U)

Strategy 1 : Handover when WCDMA quality is fulfilled. This call is kept in WCDMA as long as possible.

QSC = 7: always perform WCDMA measurements the setting;

ISHOLEV = 99: Initiate a handover request when the measured WCDMA quality level is above quality parameter MRSL regardless of the load in the GSM system.

ISHOLEV = 20: Initiate handover when the load in GSM is above 80% (that is, idle channels are less than 20%).

MRSL is the Ec/No threshold for the measured CPICH


Strategy 2: Terminate the call in GSM – To be used in Claro.

This strategy aims at keeping the call in GSM until the call is terminated, and then let idle mode behavior control in which system the UE camps. The number of IRAT handovers during a call is minimized. This will minimize ping-pong IRAT handovers.

QSC = 15: disable G2U HO

ISHOLEV = 0: never initiate a WCDMA handover request in connected mode unless the load in the GSM system is 100%, irrespective of the value of MRSL (this strategy does not consider parameter MRSL).

After the call has been terminated, the mobile is guided by the idle mode parameter setting and camping behavior to select the system in which to camp.


GSM to UMTS (G2U) Parameter EntityStart measurements QSC always, never or RSSIHO trigger MRSL Ec/No

ISHOLEV GSM load %

UMTS to GSM (U2G) Parameter EntityStart CPM measurements ’2d’ or ’6d’Ec/No or RSCPStop CPM measurements ’2f’’ and ’6b’ Ec/No and RSCPHO trigger ’3a’ Ec/No or RSCP and

gsmThresh3a RSSI

The UE measures, but the system decides when to transfer

Connected mode for CS services Strategy Inter-RAT Handover

PS connected mode strategy in WCDMA is supported by a combination of CS connected mode and idle mode parameter settings, depending on which PS state CELL_DCH (dedicated) or CELL_FACH (common) the UE is in. In GSM, the idle mode parameters will steer the PS connected mode user.

When the user is on CELL_DCH (HS), hsToDch transition can, if poor quality detected is enabled, trigger the HS user to a CELL_DCH (dedicated) and enable IRAT transition.

PS Services Strategy

The IRAT radio network parameters in WCDMA and GSM have a clear impact on the cell change/cell reselection decision when the UE is transferred between the radio accesses technologies.

The IRAT radio network parameters have very limited to no impact on the outage time following an IRAT cell change or cell reselection for a PS data connection. This outage time is dependent on the application used, the used UE and how the network is configured.

In WCDMA, a PS user can be on either dedicated channel CELL_DCH (R99) or on a common channel CELL_FACH, URA_PCH to be subject for IRAT transition attempt.

PS Services Strategy IRAT CELL CHANGE / CELL RESELECTION

WCDMA to GSM in CELL_DCH (R99) The WCDMA state decides which set of parameters that are valid in this direction. In the CELL_DCH (R99) state the connected mode parameters are used and cell change is performed.

The most important strategic decision to be made for U2G cell change for PS traffic is whether or not to enable the function for cell change from WCDMA to GSM. Ericsson recommends that a poor radio environment shall be handled by down-switches to a 64 kbit/s radio bearer.

Thereafter, if the WCDMA radio conditions continue to deteriorate, an IRAT cell change over to GSM shall take place.

PS Services Strategy IRAT CELL CHANGE / CELL RESELECTION (U2G)

GSM to WCDMA:

When a UE in GSM is in packet transfer mode, it is the idle mode cell reselection parameters that control when the IRAT cell reselection to WCDMA will take place.

Therefore, it is of importance that the idle mode parameters are correctly chosen to support the intended strategy for speech, PS services and idle mode camping.

PS Services Strategy IRAT CELL CHANGE / CELL RESELECTION (G2U)

UMTS to GSM * (U2G) Parameter EntityStart CPM measurements ’2d’ Ec/No or RSCPStop CPM measurements ’2f’ Ec/No and RSCPHO trigger ’3a’ Ec/No or RSCP

gsmThresh3a RSSI

A combination of IRAT Handover and Cell reselection.

* Dedicated mode

PS Services Strategy IRAT CELL CHANGE

GSM to UMTS (G2U) Parameter Entity1) Start/stop measurements QSI always, never or RSSI

2) CRS evaluation FDDQMIN Ec/No and FDDQOFF RSCP vs RSSI Comparsion

What to monitor in PS data performance is the unnecessary changes between the systems, for example, ping-pong between the systems that result in poor PS throughput due to several sequential outage times.

PS Services Strategy Considerations

HSDPA Mobility Phase 2

When a UE is on CELL_DCH (HS), no GSM measurements or IRAT handover are supported. To provide mobility via connected mode for IRAT users, in case an IRAT neighbor can provide a better coverage, the HS to DCH transition can be triggered by poorQualityDetected (event 2d or 6d).

• Benefit is reduced outage time through IRAT cell change compared to IRAT cell reselection for PS services.

• Drawback is reduced HSDPA coverage and decreased user experienced PS data throughput.

Additional Features (RNC R5)

• Service Based Handover to GSM

Enables operators to restrict or promote IRAT handovers for speech services. Not activated during network rollout.

• Directed Retry to GSM

Off-load traffic from a WCDMA cell to a co-sited GSM cell. Speech call with no ongoing packet connection is the only service that is diverted to GSM. Not activated during network rollout.

IRAT Parameters

IRAT - Claro Parameters

IRAT parameter setting_Claro_RevA

irat presentation rev b_claro

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