Download - 08 - Intrafrequency HO Signalling.ppt

8/14/2019 08 - Intrafrequency HO Signalling.ppt

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Soc Classification level

1 Nokia Siemens Networks 3GRANSIG/Phichet

Intrafrequency Handover3G RANSIG


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Arises when inter-RNC SHO is not possible:

Iur interface (between neighbouring RNCs)

not implemented, or congested, or not

supporting user plane, or due to whatever

reason inhibiting inter-RNC SHO

Soft/er handover Hard handover

Intra-frequency handover

Mobile Evaluated Handover

UE simultaneously connected to many cells(maximum 3):

Cells belonging to same site (intra-BTS),SOFTER HANDOVER

Cells belonging to different sites (inter-BTS),SOFT HANDOVER

The group of serving cells is called ACTIVE SET


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Cell 1 Cell 2

UE enters the SHO area,

where coverage area ofcell 1 and 2 overlap

1

1

Cell 2 has available resources,

so its added to the AS. UE is

connected both to cell 1 and 2.

2

2

UE exits SHO

area. Theres no

reason for

remaining

connected to cell 1.

3

3

Soft Handover


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Intra-frequency handover

SHO need detection (internal in UE)

(based on RNP parameters)

1

Measurement reporting (from UE to RNC)

(based on RNP parameters)

2

Active Set update

(commanded from RNC to UE)

3


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EVENT 1C REPLACEMENT

EVENT 1B DELETION

EVENT 1A ADDITION

Intra-frequency handover is said to be mobile evaluated, because its up to the mobile

to recognise the need to perform a soft-handover SHO events

The following SHO events are currently implemented:

A monitored CPICH is good enough to be added in the active set

A serving CPICH is no more good enough to stay in the active set

AS is full, a monitored CPICH becomes better than a serving one

Intra-frequency handover: Mobile Evaluated Handover


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Intra-frequency handover: Measurements

The handover measurement is based on CPICH Ec/No.

RSSI

RSCPNoEc /

CPICH Ec/No is the received energy per chip divided by the power density in the WCDMAcarrier band:

The accuracy of pilot Ec/No measurements is important for handover performance.

Measurement accuracy depends on the filtering length and mobile speed.

When a UE moves slowly or is stationary, filtering length (in ms) has to be long just enough toavoid fast fades leading to errors and causing unnecessary handovers within a short period.

On the other hand long filtering length will cause handover delays to fast moving UEs.

received signal code power

received signal strenght ind icator


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What is meant by good enough?

A monitored adjacent cell is ADDED to the Active Setwhen its good enough to bring a gain.

A serving cell is DELETED from the Active Setwhen its no more good enough.

Intra-frequency handover: Events 1A and 1B


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Event 1A reporting range [dB] (RNP

parameter, default 4dB )

Ec/No

Time

Initial cell=CPICH1

Monitored cell=CPICH 2

Reporting Period

(RNP parameter, default 0.5s )

CPICH 2 is good enough!

Event 1A : Addition


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Ec/No

Time

CPICH 1

CPICH 3

Monitored cell= CPICH 4

Event 1C margin [dB](RNP parameter, default 4dB )

CPICH 2

Active set is FULL

Event 1C : Replacement


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UE Node B(SRNC)

Node B(DRNC)

1. Measurement Report

RRC RRC

SRNCDRNC

2. Radio LinkSetup Request

RNSAP RNSAP

3. Radio Link Setup Request

C-NBAP C-NBAP

4. Radio Link Setup Response

C-NBAP C-NBAP

RNSAP RNSAP

5. Radio LinkSetup Response

AAL2SIG

6.EstablishRequest

AAL2SIG

Soft Handover: Radio Link Addition (1/3)


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UE Node B(SRNC)

Node B(DRNC)

SRNCDRNC

14. Active Set Update

RRC RRC

15. Active Set Update Complete

RRC RRC

Soft Handover: Radio Link Addition (3/3)


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UE Node B(SRNC)

Node B(DRNC)

SRNCDRNC

Soft Handover: Radio Link Deletion (1/2)

1. Active Set Update

RRC RRC2. Active Set Update Complete

RRC RRC3. Radio Link

Deletion Request

RNSAP RNSAP

4. Radio Link Deletion Request

D-NBAP D-NBAP

5. Radio Link Deletion Response

D-NBAP D-NBAP6. Radio LinkDeletion Response

RNSAP RNSAP


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UE Node B(SRNC)

Node B(DRNC)

SRNCDRNC

Soft Handover: Radio Link Deletion (2/2)

AAL2SIG

7. ReleaseRequest

AAL2SIG8. Release

Confirm

9. Release Request

10. Release Confirm

AAL2SIG AAL2SIG

AAL2SIG

AAL2SIG

AAL2SIG

AAL2SIG