Oct. 4th., 2001Dr. Helmut Schaeffer; ICM N PG GSM SE 2Handover GSM <-> UMTS

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Supported in BR6.0:

- HO from UMTS to GSM (FRS 488)

Additionally supported in BR7.0:

- HO from GSM to UMTS (FRS 490)

- “Better Cell HO” (Power-Budget HO)

- “Sufficient UMTS Coverage HO“

- “Imperative HO (Emergency HO)”

- Directed Retry from GSM to UMTS

- IE “Service Handover” in HANDOVER REQUEST and in ASSIGNMENT REQUEST on A-Interface (MSC -> BSC) is supported. It indicates to the BSS whether a HO to UMTS “should”, “should not” or “shall not” be performed.

Handover (circuit switched) GSM <-> UMTS

Oct. 4th., 2001Dr. Helmut Schaeffer; ICM N PG GSM SE 2Handover GSM <-> UMTS

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The MSC sets the IE “Service Handover” (MSC -> BSC) (Release 1999):

- “Handover to neither UTRAN nor cdma2000 shall not be performed”:

The MS/UE is kept within the GSM system. The BTS generates a Target Cell List TCL without UMTS target cells.

- “Handover to neither UTRAN nor cdma2000 should not be performed”:

The MS/UE is kept within the GSM system as long as possible. Only “Imperative HO (Emergency HO)” to UMTS performed, and only if no GSM cells are available.

- “Handover to either UTRAN or cdma2000 should be performed”:

The MS/UE is handed over to UMTS as soon as possible. I.e. the BTS initiates a “Sufficient UMTS Coverage HO” from GSM to UMTS when the “sufficient threshold” condition is met: RXLEV_NCELL(n) > UMTS_SUFFICIENT

Usage of the IE “Service Handover” in GSM BSS

Oct. 4th., 2001Dr. Helmut Schaeffer; ICM N PG GSM SE 2Handover GSM <-> UMTS

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In BR7.0 the IE “Service Handover” (MSC -> BSC) (Release 1999) is supported.(s. FRS 490)

Apart from this IE “Service Handover”, no additional service based GSM to UMTS handover features are standardized in Release 1999.

No additional service based GSM to UMTS handover features are realized in BR7.0.

GSM to UMTS HO beyond IE “Service Handover” ?

Oct. 4th., 2001Dr. Helmut Schaeffer; ICM N PG GSM SE 2Handover GSM <-> UMTS

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The “3G_MSC” supports the Iu-Interface (UMTS) and the A-Interface (GSM).

Overview: Combined UMTS / GSM Network Architecture

Oct. 4th., 2001Dr. Helmut Schaeffer; ICM N PG GSM SE 2Handover GSM <-> UMTS

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Message flow

Handover from UMTS to GSM

UE/MS UE/MSRNS-A 3G_MSC-A BTS-B

Iu-Relocation-RequiredA-Handover-Request

A-Handover-Request-AckIu-Relocation-Command

RRC-HO-CommandRI-HO-Access

A-Handover-Detect

RI-HO-CompleteA-Handover-Complete

Iu-Release-Command

Iu-Release-Complete

BSC-B

Channel Activation-Ack

Channel Activation

Handover Detection

Oct. 4th., 2001Dr. Helmut Schaeffer; ICM N PG GSM SE 2Handover GSM <-> UMTS

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Message flow

Handover from GSM to UMTS

BTS-A 3G_MSC-A RNS-B

A-Handover-RequiredIu-Relocation-Request

Iu-Relocation-Request-AckA-Handover-Command

RI-HO-Command

Iu-Relocation-DetectRRC-HO-Complete

Iu-Relocation-Complete

A-Clear-Command

A-Clear-Complete

UE/MS UE/MSBSC-A

Meas. Report HO Cond. Indication

Oct. 4th., 2001Dr. Helmut Schaeffer; ICM N PG GSM SE 2Handover GSM <-> UMTS

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Message flow

Directed Retry from GSM to UMTS

BTS-A 3G_MSC-A RNS-B

A-Handover-RequiredIu-Relocation-Request

Iu-Relocation-Request-AckA-Handover-Command

RI-HO-Command

Iu-Relocation-DetectRRC-HO-Complete

Iu-Relocation-CompleteA-Clear-Command

A-Clear-Complete

UE/MS UE/MSBSC-A

Meas. Report HO Cond. Indication

Forced HO Request

A-Assignment-Request

A-Assignment-Failure

Oct. 4th., 2001Dr. Helmut Schaeffer; ICM N PG GSM SE 2Handover GSM <-> UMTS

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Triggers for GSM to UMTS Handover (1)

Better Cell HO (Power - Budget HO)

PRIO_PBGT > 0 with the definitions:

PRIO_PBGT := PBGT - HOMARGIN - UMTS_ADJUST

PBGT := [ Min(MS_TXPWR_MAX(s), P) - RXLEV_DL - PWR_C_D ]

- [ Min(MS_TXPWR_MAX(n), P) - RXLEV_NCELL(n) ]

In addition the following minimum condition must be fulfilled for the UMTS neighbour cell:

RXLEV_NCELL > RXLEVMIN + Max (0, Pa)

with the definition Pa := (MS_TXPWR_MAX - P)

Oct. 4th., 2001Dr. Helmut Schaeffer; ICM N PG GSM SE 2Handover GSM <-> UMTS

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Triggers for GSM to UMTS Handover (2)

Sufficient UMTS Coverage HO

For RSCP reporting: RXLEV_NCELL > UMTS_SUFFICIENT_RSCP + Max (0, Pa)

For Ec/No reporting: RXLEV_NCELL > UMTS_SUFFICIENT_Ec/No + Max (0, Pa)

with the definition Pa := (MS_TXPWR_MAX - P)

For UMTS FDD cells, the parameter FDD_REP_QUANT in the SI2quater and in the MEASUREMENT INFORMATION message tells the MS/UE whether to report RSCP (FDD_REP_QUANT = 0) or Ec/No (FDD_REP_QUANT = 1).

Oct. 4th., 2001Dr. Helmut Schaeffer; ICM N PG GSM SE 2Handover GSM <-> UMTS

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Triggers for GSM to UMTS Handover (3)

Imperative HO (Emercency HO)

Inclusion of UMTS cells in Target Cell List (TCL) if the following minimum condition is met:

For RSCP reporting: RXLEV_NCELL > RXLEVMIN + Max (0, Pa)

For Ec/No reporting: RXLEV_NCELL > UMTS_MIN_Ec/No + Max (0, Pa)

with the definition Pa := (MS_TXPWR_MAX - P)

An ”Imperative" HO is initiated because for the GSM serving cell the received level is too low or the quality is too low or the MS-BTS distance is too large or because of an

Directed Retry.

Oct. 4th., 2001Dr. Helmut Schaeffer; ICM N PG GSM SE 2Handover GSM <-> UMTS

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Triggers for GSM to UMTS Handover (4)

Initiation of GSM to UMTS Directed Retry

The BSC initiates a Directed Retry:

- if the GSM serving cell is congested

or

- if the IE “Service Handover” in the ASSIGNMENT REQUEST (MSC -> BSC) is set to“Handover to either UTRAN or cdma2000 should be performed”.

Of course, a Directed Retry from GSM to UMTS can only be performed if at least one UMTS neighbour cell fulfills the minimum condition which is needed to include an UMTS cell in the TCL (s. Imperative HO / Emercency HO).

Oct. 4th., 2001Dr. Helmut Schaeffer; ICM N PG GSM SE 2Handover GSM <-> UMTS

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Abbreviations (1)

HOMARGIN(n): is a threshold which can be used to prevent handover oscillations between the serving GSM cell and neighbour cells (GSM or UMTS neighbour cell).

MS_TXPWR_MAX(n): is the maximum RF TX power an MS/UE is permitted to use in the neighbour cell (GSM or UMTS neighbour cell).

MS_TXPWR_MAX(s): is the maximum RF TX power an MS/UE is permitted to use on a traffic channel in the GSM serving cell.

P: is the maximum TX power capability of the MS/UE

PWR_C_D: is the difference between the maximum downlink RF power permitted in the GSM serving cell and the actual downlink power due to the BSS power control.

RXLEV_DL: is the GSM serving cell received level (downlink) measured by the MS/UE.

Oct. 4th., 2001Dr. Helmut Schaeffer; ICM N PG GSM SE 2Handover GSM <-> UMTS

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Abbreviations (2)

RXLEVMIN(n): defines the minimum received level which is required to perform a handover to the neighbour cell (GSM or UMTS neighbour cell).

RXLEV_NCELL(n): is the neighbour cell received level (GSM or UMTS neighbour cell) measured by the MS/UE. It contains the neighbour cell measurement quantity (received level for GSM cells; RSCP or Ec/No for UMTS FDD cells; RSCP for UMTS TDD cells).

TCL: Target Cell List

UMTS_ADJUST(n): is an inter-system adjustment parameter in order to have the flexibility to adjust the RXLEV_NCELL(n) of the UMTS neighbour cells (n) to the RXLEV_DL of the GSM serving cell. For UMTS neighbour cells (n), the UMTS measurement quantity RSCP, which the MS/UE reports in its Measurement Report, is used for RXLEV_NCELL(n).

UMTS_MIN_Ec/No: defines the minimum Ec/No threshold which is required to include an UMTS FDD cell into the target cell list TCL in case of an "imperative" HO (this parameter is only used for UMTS FDD cells and only in case of Ec/No reporting).

Oct. 4th., 2001Dr. Helmut Schaeffer; ICM N PG GSM SE 2Handover GSM <-> UMTS

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Abbreviations (3)

UMTS_SUFFICIENT_RSCP(n) and UMTS_SUFFICIENT_Ec/No(n): these are new "sufficient" threshold parameters which are used for GSM to UMTS "Sufficient UMTS coverage" HO and not used for GSM to GSM handover. They define the "sufficient" threshold which is required to perform a handover to the neighbour UMTS cell.