abis fail call

1 © NOKIA FILENAMs.PPT/ DATE / NN

Statistic: Signaling links in BSS

• about 10% of SDCCH request will be unsuccessful due to A-bis failure (001075, A-bis fail call) and transaction attempt will be drop

• 001075 has 19 different reasons (DX causes)• Call set up picture (MOC.doc)• T3101 expiry (SDCCH reservation)• Retransmission in BTS level

• example: BSC Manila1,2,3,Vito Cruz 1 and 2 under MSCVC4 (1075.xls)


SDCCH_ABIS_FAIL_CALL(1)


SDCCH_ABIS_FAIL_CALL(2)


SDCCH Drop %, S3 (sdr_1a)

Use: To follow up the performance of SDCCH from technical point of view. Experiences on use: 1) High SDCCH drop rates usually result from ghost accesses. A BTS decodes

them from environmental or background noise and filters out most of them. However, all of them cannot be filtered out and the RACH request is passed on to the BSC for processing and for the allocation of a SDCCH channel.

The counter GHOST CCCH RES (3030) is updated each time a CHANNEL REQUIRED is rejected because of an invalid establishment cause. In GSM ph.1 there exist altogether eight establishment causes, three of which are undefined as invalid, for example,resulting in that this counter shows only 3/8 of all the ghost accesses the BTS has decoded. For the rest, a SDCCH is allocated and this will result in SDCCH_ABIS_FAIL_CALL failure. Because of ghost attempts the SDCCH drop ratio is high with low traffic. As the amount of call attempts increases, the influence of ghosts becomes smaller and the drop ratio approaches its real value.

2) The rate of ghosts coming to SDCCH dropped when BTS B9 with improved ghost filtering was

taken into use.


Trigger Point(s)


Trigger Point1


T9103 TIMER


Trigger Point2


T9108 TIMER


Trigger Point3


AUGMENTATION OF COUNTER 1075


T3101 TIMER


T10 TIMER


T3107 TIMER


T3122 TIMER


Random Access

Nbr of RACH slots

ave_rach_slot/res_acc_denom1

Peak RACH load

peak_rach_load

Average RACH busy

ave_rach_busy/res_acc_denom3

RACH slot is counted as busy when level is above -100dBm estimated at the RACH slot

Capacity

Load

BTSTRX

RACH

RACH has to pass- S/N test (pattern)- parity test

BSC

RACH accesses

ave_rach_access

Author: J.Neva 10/96Version: 1.5 17.3.2000PMWG approval.: 1.5 29.3.2000

Average value over the whole measurement period

Higest value of ave_rach_busy during the meas. period

BTS sw B9.0 and DF2.0 has enhanced filtering of ghosts- energy level check with previous burst info- All 41 bits of training sequence used

GHOSTS= SDCCH seizures that do not lead to a useful benefit - thermodynamical type of noise - in band noise from network or environment- MS at the limit of sensitivity

GHOSTSorMS

Before B9 around 10 ghosts per hour to BSC

CCCHLOADIND (every 30s)

After B9 around 1 ghosts per hour to BSC

Max Number Retransmission (RET) (1,2,4,7) defines nbr of repetition by MS

Rach_3 Rach_4*) T3126

*) T3126: In GSM Ph.1 waiting period is not defined (e.g. a Nokia MS has 800ms) but in GSM ph.2 it is defined by a complex algoritmand can be as long as 5 sec.GSM 04.08 says: This timer is started either after sending the maximum allowed number of CHANNEL REQUEST messages during an immediate assignment procedure or on receipt of an IMMEDIATE ASSIGNMENT REJECT message,whichever occurs first.It is stopped at receipt of an IMMEDIATE ASSIGNMENT message, or an IMMEDIATE ASSIGNMENT EXTENDED message.At its expiry, the immediate assignment procedure is aborted.

Immediate Assignment

Number of Slots Spread Trans (SLO) (3..12, 14, 16, 20, 25, 32, 50 TDMA frames between retransmissions) MML default 10.

In BTS sw B12 and DF5 the filtering of accesses with illegal establishment causes will be moved to BTS

Known phenomenom: Handover Access bursts causing SDCCH failures, blocking and Ghosts

Channel Required

NOTE: triggered related to level based RACH detection(not what is accepted as RACH andpassed as Channel Req)

If RACH passed all tests

NOTE: triggered related to what is accepted as RACH

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http://nea.ntc.nokia.com/cgi-bin/cgiwrap/neva/params?103

http://nea.ntc.nokia.com/cgi-bin/cgiwrap/neva/frmls?rach_3

http://nea.ntc.nokia.com/cgi-bin/cgiwrap/neva/frmls?rach_4



http://wwwmsg.ntc.nokia.com/ni/studies/studies.htm


Ghosts Author: J.Neva 12/96Version: 1.0 5.12.96

Level

White noise

1.467282 1.497941 1.225209 1.485909 1.4019451.467282 1.497941 1.225209 1.485909 1.4019451.391514 1.467282 1.385073 1.012121 1.252343

0 1 2 3 4

0

1

2

3

4

5

6

7

8

9

1 6 11 16 21 26 31 36 41 46 51 56 61

In-band Disturbances

Real Mobiles

White Noise


Access Grant capacity (S8-9)

AG BLOCKING (blck_13)

sum(del_ind_msg_rec)100 * ----------------------------------------------------% sum(imm_assgn_rej+imm_assgn_sent)

table = p_nbsc_res_acc

BSC

c3005del_ind_msg_rec

How many times Immediate Assignment orImmediate Assignment Reject have beenlost due to AG buffer overflow.MS needs to send a new Channel Request.

Author: J.Neva 10/96Version: 1.2 1/2000PMWG approval.:1.1 11.2.98

c3001imm_assgn_sent

c3002imm_ass_rej

One message can include 1 - 4 Immediate AssignmentReject -Messages (from S6) !


Immediate Assignment Rejected

OR

MS BTS

Overflow of AG buffer

Parameters:AG = = Number of Blocks Reserved for Access Grant (0..7 if noncombined, 0..2 if combined, 1..7 if SBCH used in SDCCH/8)NOTE: If AG=0, Access Grant has priority over Paging If AG<>0, Paging has priority on PCHIf AG<>0, only Access Grant is sent on AG blocks

Buffer capacity =8 Abis messages


Immediate Assignment Rejected

Delete indication

OR

Sent on AGCH or alternatively on PCHif there is free capacity

Returned for each deleted AGCH message

MS is not allowed to attempt new RR-establishment i.e channel requestuntil T3122 expires

Channel Request (RACH) Channel Required

Channel Activation

Channel Activation Ack

RACH on CCCH/c3004ch_req_msg_rec

/c1007sdcch_assign

Ghosts having valid establishmentcause get trhough even if cell wasbarred.

Abort if T3126 expires T9103

ORChannel Activation Nack

e.g. SCCH blocking

SDCCH released with clearcode 500341.

/c1000 sdcch_seiz_att

CCCH overload

c1155sdcch_unsucc_imm_assign_att

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SDCCH requests (S9)

SDCCH REQUESTS/c1000

sdcch_seiz_att

ASSIGNMENTS FOR CALLS,LU,SS/c1007

sdcch_assign

BLOCKED/blck_15

sdcch_busy_att - tch_seiz_due_sdcch_con

RACH on CCCH/c3004

ch_req_msg_recREJECTED DUE TO ILLEGAL EST.CAUSE (3/8 of ghosts in ph.1´)/c3030ghost_ccch_res

5/8 OF GHOSTS (ph.1) AND OTHER FAILURES BEFORE ESTABL. IND.(incl.IMSI detach):/SD_1ac1007- TRF_25a

MOC (incl.SMS and SS)/c3013succ_seiz_orig

MTC (incl.SMS)/c3012succ_seiz_term

CALL RE-EST./c3020

sdcch_call_re_est

LOCATION UPDATE/c3019sdcch_loc_upd

EMERGENCY CALL/c3021sdcch_emerg_call

SDCCH ACCESSES REJECTED IN BSC

TRUE SDCCH SEIZURES/TRF_25a (not updated in SDCCH HO)

SEIZURES FOR HO/c1006

sdcch_ho_seiz

SDCCH FAILURES/c1075sdcch_abis_fail_call (blocked chan.,corrupted

msgs, failed chan.act.)

Author: J.Neva 5/96Version: 1.5 25.1.2001PMWG approval.: v 1.5 25.1.2001

TRUE SDCCH SEIZURES FOR CALL,SMS, SS/TRF-27

IMSI DETACH /c3033 (S7)imsi_detach_sdcch

TRUE SDCCH SEIZURES FOR CALL /TRF-26

TRF-27- succ_sdcch_sms_est- unsucc _sdcch_sms_est

TRUE SDCCH SEIZURES FOR SMS

succ_sdcch_sms_est+ unsucc _sdcch_sms_est

SDCCH BLOCKING (blck_5a)

SDCCH-SDCCH HO

other than sdcch_abis_* failures

small part of failures

Normal LU

Periodic LU

IMSI attach

MS accessing, noise (ghosts)

NOTE:Triggered also in case ofHO attempt if there are nofree SDCCH

SDCCH-SDCCHHO

TCH

FACCH call setups/c1099

tch_seiz_due_sdcch_con

Distance checking BSS5280 (S5)

REJECTED DUE TO DISTANCE/c3031 (S5)rej_seiz_att_due_dist

SDCCH FAILURES/c57020 (S7)t3101_expired

(Ghosts)

CALL RE-EST. ASSGN./c57022 (S7)sdcch_re_est_assign

SUPPLEMENTARY SERVICE REQUEST /c3044 (S9)succ_seiz_supplem_serv

T3101 adjustable by MMLZEGT:T3101..

BCSU Lower Limit = 34 unhandled reqs/c3039 (S7)bcsu_overload_lower_limit

BCSU Upper Limit =53 unhandled reqs/c3040 (S7)bcsu_overload_upper_limit

Limit per CCCH =20 req.per BTS (CCCH)/c3041 (S7)bcsu_overload_deleted_rach

Call_assign_after_sms /c??? S10.5

ND report 134



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http://nea.ntc.nokia.com/cgi-bin/cgiwrap/neva/frmls?trf_25a



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abis fail call

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