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)
2 © NOKIA FILENAMs.PPT/ DATE / NN
SDCCH_ABIS_FAIL_CALL(1)
3 © NOKIA FILENAMs.PPT/ DATE / NN
SDCCH_ABIS_FAIL_CALL(2)
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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.
5 © NOKIA FILENAMs.PPT/ DATE / NN
Trigger Point(s)
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Trigger Point1
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T9103 TIMER
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Trigger Point2
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T9108 TIMER
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Trigger Point3
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AUGMENTATION OF COUNTER 1075
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T3101 TIMER
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T10 TIMER
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T10 TIMER
15 © NOKIA FILENAMs.PPT/ DATE / NN
T3107 TIMER
16 © NOKIA FILENAMs.PPT/ DATE / NN
T3107 TIMER
17 © NOKIA FILENAMs.PPT/ DATE / NN
T3122 TIMER
18 © NOKIA FILENAMs.PPT/ DATE / NN
T3122 TIMER
19 © NOKIA FILENAMs.PPT/ DATE / NN
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
20 © NOKIA FILENAMs.PPT/ DATE / NN
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
21 © NOKIA FILENAMs.PPT/ DATE / NN
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
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
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
22 © NOKIA FILENAMs.PPT/ DATE / NN
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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