Csfb Final

CSFB optimizationRadio LTE optimization and LTE SON & Site

Integration process workshop

Milan , 26-27 May 2015

C2 – Vodafone Restricted

1. CSFB principle

2. Performance key factors

3. Call phases

– 4G leaving and RAT camping

– Legacy RAT registration

4. Case study: MOC 4G to MTC 3G

Agenda

Insert Confidentiality Level in slide footer C2 – Vodafone Restricted

CSFB principle

3 June 9, 2015

Voice evolution in three steps: From Single radio to Convergence

Source: Qualcomm

• Longer call setup time (+2/3 sec with 3G as landing RAT)

• Additional 3,5s in case of CSFB to 2G

• Worse Call Setup Success Rate (1%)

C2 – Vodafone Restricted

C2 – Vodafone restricted 4 June 9, 2015

Overall call setup time performance strongly depends on the scenario considered and radio/core implementation

- Call scenarios: Mobile-to-Mobile or Mobile to Fixed/ISDN benchmark tests might

have very different performance in terms of call setup time and accessibility.

- Landing radio access technology: preferred technology and radio fallback strategy

are crucial for determining the average call setup time.

- Core Architecture: Overlay MSS or pooling Core CS architecture could significantly

impact call setup time performance.

- NAS procedures: frequency of security procedures (Authentication, Identity,… )

executed during call setup might introduce high variance in the overall setup time.

Performance ¦ key factors

5 June 9, 2015

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Identification of call setup phases

and relevant trigger points

Common phases for MOC and MTC:

1. 4G leaving

2. Legacy RAT camping

3. Legacy RAT registration

4. Setup

5. Alert

Call phases ¦ MOC and MTC

C2 – Vodafone restricted

6 June 9, 2015

RRC Release with Redirect 1. Basic without target RAN System Information (SI) :

Easy implementation and fast deployement, longer call set-up time because SI needs to be fetched by the UE in the target RAN

2. Enhanced CSFB:

i. Deferred Measurement Control Reading (WCDMA)RACH access is performed after reading SIB 1,3,5 and 7 only (SIB11 containing neighbour info are sent in the Measurement control message) . Valid for >Rel7 UE . Gain: hundred ms. SIB caching implementation in the device could prevent the usage of deferred SIB.

ii. SI exchange based on 3GPP RIM procedures (GSM and WCDMA)System Info are provided via LTE redirection message (via core network ). Gain : 0,8s in 3G and 2.5 in 2G

PSHO (Packet Switched Handover)3G cell measurement are performed and if a 3G suitable cell is found, the PS handover to UE is sent (improve call setup time ~0,8s and accessibilty).

4G leaving and RAT camping /1

Operationaleffort

CommercialDrivers

Call Setup Time

Accessibility


7

June 9, 2015

Start Band LANDING TECNOLOGY / BANDS

L1800 U2100 U900 G1800 G900

L2600 U2100 U900 G1800 G900

L800 U900 G900 other


Landing technology strategy is crucial for guaranteeing a good level of accessibility and call setup time

HIGH LOW

• Strategy is based on the footprint of the different

‘coverage’ layers taking into account the propagation

of each layer.

• In case of non-contiguous/homogeneous layer,

hybrid solution with different CSFB implementation

could be adopted.


8 June 9, 2015


Fine tuning of DRX cycle and

paging occasion settings for

saving time in order of tens

milliseconds

CS paging repetition timer (from UE

perspective) has to be carefully set.

Depending on the total number of

repetition available on MSC, paging

repetition on both MME and eNodeB

could be exploited.

In case of Mobile terminated call, paging timer and repetition scheme influence call setup time


Insert Confidentiality Level in slide footer 9 June 9, 2015

Legacy RAT registrationNot-pooled (GMSC) architecture

In a pure not-pooled MSC architecture , fallback

always occurs in MSC that are different from the G-

MSC and Location Update procedure is needed

(inter-MSC scenario with HLR involved) during call

setup.

Pooled MSC architecture

In a pure not-pooled MSC architecture, LAU is not

performed during the call setup Real Combined TA/LA Direct SG interface (MME-MSC)

Fast implementation from operational perspective but longer setup time in CSFB MOC and MTC and lower

reachability in MTC due to a frequent Loc. Upd.

Call setup time improvementCSMT FLAG Essential to avoid the paging lost after LAU and re-

allocate signalling resources on the A-interface. LA Update & call

setup performed in one single radio connection setup

Mobile Terminating Roaming Forwarding (MTRF)Avoid release the call leg to the G-MSC, reducing signalling flow and

MT procedure

Avoidong Location Update, call setup is shorter (500ms) but potential short period of unreachability after the call.

Increased complexity in radio planning and MME TAC/LAC mapping

Each legacy MSC has dedicated “virtual” LAC.

MME is configured with a mapping between

TACs and “virtual” LAC of the MSC. in legacy

MSCs: each “virtual” LAC points to overlay MSC


10 June 9, 2015

Case study: MOC 4G to MTC 3G ¦ Message flow


11 June 9, 2015

All Operators with:• RRC Release with Redirect

• Preferred landing technology: UMTS

• Pooled MSC architecture

-

Case study: MOC 4G to MTC 3G ¦ Typical performance


12 June 9, 2015

0,00%

10,00%

20,00%

30,00%

40,00%

50,00%

60,00%

70,00%

80,00%

90,00%

100,00%

0,2

3

0,4

3

0,5

2

0,6

1

0,7

0,7

9

0,8

8

0,9

7

1,0

6

1,1

5

1,2

4

1,3

4

1,4

3

1,5

2

1,6

1

1,7

1,7

9

1,8

8

1,9

7

2,0

6

2,1

6

2,2

7

2,3

6

2,4

8

2,5

8

2,6

9

2,7

9

2,9

1

3,0

2

3,2

5

3,9

5

4,5

4

5,3

1

Duration [s]

side1(from 4G RRC conn release to 3G RRCconn req)

EE

Telefonica

Three

Vodafone

Operator AOperator BOperator COperator D

Operator C:• More session with UMTS

landing technology• Deferred SIB

Case study: MOC 4G to MTC 3G ¦ Time distribution 1


13

June 9, 2015

0,00%

10,00%

20,00%

30,00%

40,00%

50,00%

60,00%

70,00%

80,00%

90,00%

100,00%

0,0

5

0,5

2

1,1

7

1,7

6

2,0

4

2,2

6

2,4

8

2,7

2,9

2

3,1

4

3,3

6

3,5

8

3,8

4,0

2

4,2

4

4,4

6

4,6

8

4,9

5,1

2

5,3

4

5,5

6

5,7

8 6

6,2

2

6,4

4

6,6

9

6,9

5

7,2

7

7,6

8,0

1

8,4

2

8,7

6

9,3

7

9,9

3

Duration [s]

side1 (from call proceeding to alerting)

EE

Telefonica

Three

Vodafone

Operator AOperator BOperator COperator D

Operator C:• No Authentication/Cyphering

procedures • Early RAB assigment on

Terminated side

Case study: MOC 4G to MTC 3G ¦ Time distribution 2


Documents

Csfb Final