Call Setup Time

Call setup Time – Preamble PRACH

• During drive testing can be noted that there are call setup failures where the network does not seem to respond to RRC Connection Requests with RRC Connection Setup –message.These are problems due to the spiky UL noise and due to that the power ramping is not aggressive enough to provide high enough Tx power for the terminal during open loop PC

Downlink / BSDownlink / BS

Uplink / UEUplink / UEPreamble 1 Message part

…. ….

UEtxPowerMaxPRACH

Preamble n

PRACH_preamble_retrans: The maximum number of preambles allowed in one preamble ramping cycle

RACH_tx_Max: # of preamble power ramping cycles that can be done before RACH transmission failure is reported,

L1ACK/AICH

RACH

PowerOffsetLastPreamblePRACHmessage

PowerRampStepPRACHpreamble

PtxAICH

PRACHRequiredReceivedCI

Note: The power ramp-up process will continue until

1) A positive or negative AI is received from the network

2) RACH_tx_MAX value is reached

3) UE reaches UEtxPowerMaxPRACH value

Call setup Time – Preamble PRACH

Ptx = CPICHtransmissionPower-RSCP(CPICH) +RSSI(BS) + PRACHRequiredReceivedCI (-20dB)Example:

CPICH = 33dBm (Parameter per Node-B)

RSCP = -80dBm (Measured by UE)

RSSI = -85 dBm

UL_Required_C/I = -25 dB (Parameter per Node-B)

UE PRACH First Preamble Power = 33 dBm – (-80 dBm) + (-85

dBm) + (-25 dB) = 8 dBm

Ptx = CPICHtransmissionPower-RSCP(CPICH) +RSSI(BS) + PRACHRequiredReceivedCI (-20dB)Example:

CPICH = 33dBm (Parameter per Node-B)

RSCP = -80dBm (Measured by UE)

RSSI = -85 dBm

UL_Required_C/I = -25 dB (Parameter per Node-B)

UE PRACH First Preamble Power = 33 dBm – (-80 dBm) + (-85

dBm) + (-25 dB) = 8 dBm

The parameters affecting to open loop power control are, in brackets are the recommended values:• PRACH_preamble_retrans (7)• RACH_tx_Max (16) • PowerOffsetLastPreamblePRACHmessage (2 dB)• PowerRampStepPRACHpreamble (2dB)

The PRACHRequiredReceivedCI (-20dB) allow to calculate the UEpower for the fist preambleas in thefollowing:

The parameter PRACHRequiredReceivedCI can be set to -18…-20dB instead of the default -25dB (typically -20dB is enough)

Call setup Time – Preamble PRACH

100%

0% 0% 0%

88%

2% 5% 6%

0%

20%

40%

60%

80%

100%

1 2 3 4

# RRC Connection Request Messages per call setup

%

PRACH req. C/I = -20dB PRACH req. C/I = -25dB

Clear improvement in number of needed RRC Connection Request messages per call. For –20dB 100% of established calls are setup with only 1 RRC Connection Request message

Clear improvement number of sent preambles per RRC Connection Request for –20dB case. For –20dB 50% of cases the needed number of preambles is <=4 where as for –25dB it is ~6.5

0%

10%

20%

30%

40%

50%60%

70%

80%

90%

100%

1 2 3 4 5 6 7 8

PRACH req. C/I = -25dB PRACH req. C/I = -20dB

There should be significant improvement also for call setup delay

Typical improvement passing from -25dB to -20dB:

Call setup Time – Preamble PRACH

The average number of acknowledged PRACH preambles during the RRI period can be calculated based on the KPI below

RACH load due to preamble can then be calculated by dividing the above further by the max number preambles can be received during RRI

• For example if RRI period is 200ms the are 10 20ms RACH frames and in each 20ms RACH frame there are 15 RACH sub slots within each it is possible to receive and decode max 4 preambles -> therefore in 200ms it is possible to receive 15*4*10=600 preambles

BLES_ACK_PREAMDENOM_RACH M1000C177

ESCK_PREAMBLSUM_RACH_A M1000C176

BLES_ACK_PREAMDENOM_RACH M1000C177

ESCK_PREAMBLSUM_RACH_A M1000C176

% 100*/600BLES_ACK_PREAMDENOM_RACH M1000C177

ESCK_PREAMBLSUM_RACH_A M1000C176 % 100*/600

BLES_ACK_PREAMDENOM_RACH M1000C177

ESCK_PREAMBLSUM_RACH_A M1000C176

Call Setup Time – SRB Rate

Why 13.6kbit/s?

Use of 13.6 kbit/s SRB also in highly loaded networks

Decreased setup times (PDP context activation minimum 0.7s lower)

Improved Iub efficiency

Typical improvement passing from 3.4 to 13.6

0

1

2

3

4

5

6

7

3G-3G CS call setup PS call setup DCH allocation

Se

con

ds

Nokia RAN1.5 (3.4 kbps) + M11

Nokia RAN04 (13.6 kbps) + M12

Nokia RAN target

Call setup Time – KPI

In RN2.2 the following counters are available to monitor the Call Setup Time

RRC Setup TimeM1001C221/M1001C222

RAB Setup TimeM1001C223 / M1001C224 for CSM1001C235 / M1001C236 for DATA BACKGR

In detail we have:

M1001C221 - SUM OF RRC SETUP TIMES Sum of RRC setup times. This counter divided by the DENOMINATOR - M1001C222 gives the averageRRC setup time. RRC setup time is defined as the time between the RRC: RRC CONNECTION REQUESTmessage and the RRC: RRC CONNECTION SETUP COMPLETE message.

M1001C223/235 - SUM OF RAB SETUP TIMES FOR CS VOICE/FOR DATA BACKGRSum of RAB setup times. This counter divided by the DENOMINATOR - M1001C224/236 gives the averageRAB setup time. RAB setup time is defined as the time between the RANAP: RAB ASSIGNMENTREQUEST and RANAP: RAB ASSIGNMENT RESPONSE messages during RAB establishment.

Call setup Time – Annex1

MO-UE MT-UEMobile-to-mobile CS call setup on common channelsDelay CumulativeRRC connection request UE RNC 0 0RRC connection setup RNC UE 40 40RRC connection setup completeUE RNC 100 140CM service request UE CS 200 340Security mode command RNC UE 100 440Security mode complete UE RNC 200 640Setup UE CS 300 940Call proceeding CS UE 100 1040 Paging RNC UE 400 1340Radio bearer setup RNC UE 100 1140 RRC connection request UE RNC 50 1390Radio bearer setup complete UE RNC 300 1440 RRC connection setup RNC UE 40 1430

RRC connection setup completeUE RNC 100 1530Paging response UE CS 100 1630Security mode command RNC UE 100 1730Security mode complete UE RNC 200 1930Setup CS UE 300 2230Call confirmed UE CS 100 2330Radio bearer setup RNC UE 100 2430Radio bearer setup complete UE RNC 300 2730

Alerting CS UE 250 2980 CS UE 250 2980

Parallel RB setup for MO-UE and paging of MT-UE

(CS core feature)

<3.0 s mobile-to-mobile AMR call setup time

Average paging delay

of 320 ms assumed (640

ms paging cycle)

RA

CH

/FA

CH

RA

CH

/FA

CH

Typical value for CS Call Setup Time

Call setup Time – Annex2

RRC + PDP on common channels Delay CumulativeRRC connection request UE RNC 0 0RRC connection setup RNC UE 40 40RRC connection setup complete UE RNC 100 140GPRS service request UE PC 200 340Security mode command RNC UE 100 440Security mode complete UE RNC 200 640PDP context activation request UE PC 250 890Radio bearer setup RNC UE 150 1040Radio bearer setup complete UE RNC 300 1340PDP context activation accept PC UE 200 1540

Common channels used for setup to

avoid slow synchronized

reconfigurations later

Parallel RB setup and RL/AAL2 setups (or pre-

reserved Radio links)

RA

CH

/FA

CH

<1.6 s PS call setup time

Initial bit rate DCH allocated directly together

with SRB

Typical value for PS Call Setup Time