Contents 1.
CALL DROP DEFINITION and MEASUREMENT POINTS ............................................................................................................ 2
2. CALL DROP COUNTERS ................................................................................................................................................................ 3 2.1 CALL DROP COUNTERS RELATIONS ....................................................................................................................................... 3 2.2 CALL DROP COUNTERS DEFINITIONS .................................................................................................................................... 4 2.3 CALL DROP COUNTERS INCREMENT LOGIC .......................................................................................................................... 4 3. CALL DROP TROUBLESHOOTING ................................................................................................................................................. 5 3.1 CALL DROP CAUSE ANALYSIS ................................................................................................................................................ 5 3.2 CALL DROP REASONS for GENERAL CALL DROP TYPES ......................................................................................................... 6 3.3 TROUBLESHOOT STEPS FOR CALL DROP ............................................................................................................................... 6 3.3.1 PARAMETER PROBLEMS ................................................................................................................................................ 6 3.3.2 PATH BALANCE PROBLEMS ............................................................................................................................................ 7 3.3.3 COVERAGE GAPS PROBLEMS ......................................................................................................................................... 8 3.3.4 QUALITY and INTERFERENCE PROBLEMS .................................................................................................................... 11 3.3.5 MISSING NEIGHBOR PROBLEMS .................................................................................................................................. 15
1. CALL DROP DEFINITION and MEASUREMENT POINTS Generally TCH Drop Formula is like below; TCH call drop rate=TCH call drops / Successful TCH seizures (all) Measurement points of TCH Drop are showed in below sketch.
TCH serves as traffic channel, BSC receives ERROR INDICATION message from BTS. TCH is seized as traffic channel, BSC receives CONNECT FAILURE INDICATION message from BTS. In assignment procedure and handover procedure, failure of decoding HANDOVER DETECTION and HANDOVER COMPLETE message. TCH serves as traffic channel, incoming BSC handover initiated and the timer for the target cell to wait for HANDOVER COMPLETE message expires. TCH serves as traffic channel, outgoing BSC handover initiated and the timer for the source cell to wait for CLEAR COMMAND message from MSC expires (T8 expires). In intra-BSC handover procedure, the target cell sends Inter Clear Request to the source cell when the timer for the target cell to wait for HANDOVER COMPLETE from MS expires, in this case this item is measured in the source cell. In Intra-BSC handover procedure, the source cell, excluding the source cell for directed retry, measures the item when the timer for the source cell to wait for Inter Clear Request with cause value HANDOVER COMPLETE from the target cell expires. In Intra-BSC handover procedure, when the target cell AM/CM net-drive fails (due to timeout or negative acknowledgement), the target cell sends Inter Clear Request to source cell, in this case, this item is measured in the source cell. In the case that MS reverses to the original channel after intra BSC handover fails, the source cell first releases the terrestrial connection but the AM/CM re-net-drive fails (due to timeout or negative acknowledgement). In this case this item is measured in the source cell. The resource of the lower_priority call will be preempted by the higher_priority call if MSC and BSC both support preemption, which will cause call drop. This item is measured when the RSL link of the TRX that the call is using disconnects, which will cause call drop.
2. CALL DROP COUNTERS 2.1 CALL DROP COUNTERS RELATIONS Call Drop has a set of counters which related to each other like below schema
CM33
CM33C
CM332
CM330
CM331
H3027Ca CM3300
CM3301
CM3302
H3028Ca H3127Ca
M3100A
M3101A
M3102
H3128Ca
M3100B
M3101B
M3202
H3327Ca
M3100C
M3101C
M3200A
M3101D
M3200B
M3101E
M3200C
M3201A M3201B M3201C M3201D M3201E
H3328Ca
CM333
CM334
CM335
2.2 CALL DROP COUNTERS DEFINITIONS These Call Drop counters meaning are below.
CM330
CM33C
Call Drops on Radio Interface in Stable State (Traffic Channel)
CM3300
Call Drops on Traffic Channel in Stable State (Error Indication)
CM3301
Call Drops on Traffic Channel in Stable State (Connection Failure)
Call Drops on Radio Interface (Traffic Channel) CM3302
CM33
Call Drops on Traffic Channel
H3027Ca H3028Ca Call Drops on Radio H3127Ca Interface in Handover CM331 State (Traffic H3128Ca Channel) H3327Ca H3328Ca CM332 CM333 CM334 CM335
Call Drops on Traffic Channel in Stable State (Release Indication) Failed Internal Intra-Cell Handovers (TimerExpired) (TCHF) (TrafficChannel) Failed Internal Intra-Cell Handovers (TimerExpired) (TCHH) (TrafficChannel) Number of Unsuccessful Outgoing Internal Inter-CellHandovers (Timer Expired)(TCHF) Number of Unsuccessful Outgoing Internal Inter-CellHandovers (Timer Expired)(TCHH) Failed Outgoing External Inter-Cell Handovers (T8 Expiry)(TCHF) (Traffic Failed Outgoing External Inter-Cell Handovers (T8 Expiry)(TCHH) (Traffic
M3100A M3100B M3100C M3200A M3200B M3200C M3101A M3101B M3101C M3101D M3101E M3201A M3201B M3201C M3201D M3201E M3102 M3202
Call Call Call Call Call Call Call Call Call Call Call Call Call Call Call Call Call Call
Drops due to ERR IND Received on TCHF (Traffic Channel) in Stable State (T200 Expired) Drops due to ERR IND Received on TCHF (Traffic Channel) in Stable State (Unsolicited DM Response) Drops due to ERR IND Received on TCHF (Traffic Channel) in Stable State (Sequence Error) Drops due to ERR IND Received on TCHH (Traffic Channel) in Stable State (T200 Expired) Drops due to ERR IND Received on TCHH (Traffic Channel) in Stable State (Unsolicited DM Response) Drops due to ERR IND Received on TCHH (Traffic Channel) in Stable State (Sequence Error) Drops due to CONN FAIL Received on TCHF (Traffic Channel) in Stable State (Radio Link Failure) Drops due to CONN FAIL Received on TCHF (Traffic Channel) in Stable State (HO Access Failure) Drops due to CONN FAIL Received on TCHF (Traffic Channel) in Stable State (OM Intervention) Drops due to CONN FAIL Received on TCHF (Traffic Channel) in Stable State (Radio Resource Unavailable) Drops due to CONN FAIL Received on TCHF (Traffic Channel) in Stable State (Other Causes) Drops due to CONN FAIL Received on TCHH (Traffic Channel) in Stable State (Radio Link Failure) Drops due to CONN FAIL Received on TCHH (Traffic Channel) in Stable State (HO Access Failure) Drops due to CONN FAIL Received on TCHH (Traffic Channel) in Stable State (OM Intervention) Drops due to CONN FAIL Received on TCHH (Traffic Channel) in Stable State (Radio Resource Unavailable) Drops due to CONN FAIL Received on TCHH (Traffic Channel) in Stable State (Other Causes) Drops due to REL IND Received on TCHF (Traffic Channel) Drops due to REL IND Received on TCHH (Traffic Channel)
Call Drops Due to No MR from MS for a Long Time (Traffic Channel) Call Drops due to Abis Terrestrial Link Failure (Traffic Channel) Call Drops due to Equipment Failure (Traffic Channel) Call Drops due to Forced Handover (Traffic Channel)
2.3 CALL DROP COUNTERS INCREMENT LOGIC Radio Link Timeout increasing and decreasing in below sequence. As seen, when uudecoded SACCH occurs, RLT decreased by one, decoded SACCH occurs increased by two. If RLT becomes zero than Radio Link will be released. It is calculated continuously for both uplink and downlink. Also if ERROR INDICATION message sent to BSC, reasons like; T200 expired : If BTS could not receive any acknowledge message to send I Frame till T200 expired, it repeats sending I Frame for N200+1 times. At the end if BTS still could not get acknowledge for I Frame, it sends ERROR INDICATION with cause of timer T200 expired (N200+1) times (0x01) to BSC. M3100A or M3200A are incremented according to suitable channel type (TCHF or TCHH). Unsolicited DM Response : If BTS gets unexpected DM Frame, it sends ERROR INDICATION with cause unsolicited DM response (0x05) to BSC. M3100B or M3200B are incremented according to suitable channel type (TCHF or TCHH). Sequence Error : If BTS gets I and S Frames not in correct order, it sends ERROR INDICATION with cause sequence error (0x07). M3100C or M3200C are incremented according to suitable channel type (TCHF or TCHH). If CONECTION FAILURE message sent to BSC;
In Uplink, if BTS could not decode SACCH then it sends to BSC CONNECTION FAILURE message with reasons Radio Link Failure, HO Access Failure, OM Intervention, Radio Resource Unavailable and Other Causes. According to reason and suitable channel type, one of the M3101A, M3101B, M3101C, M3101D, M3101E, M3201A, M3201B, M3201C, M3201D and M3201E are incremented. If Multi Frame link established and BTS gets DICS Frame from MS, than BTS sends RELEASE INDICATION to BSC according to suitable channel type.
3. CALL DROP TROUBLESHOOTING 3.1 CALL DROP CAUSE ANALYSIS For troubleshooting, first thing to do search about what kind of drops occurs generally. Get stats for all call drop counters for a period. As seen in one day total drop numbers; % 99,7 of drops occurs in Radio Interface, % 90,2 of Radio Interface Drops occurs in Stable State, % 34,1 of Stable Drops occurs in Error Indication and % 65,9 in Connection Failure, All of Error Indication drops occurs in T200 expired, All of Connection Failure drops occurs in Radio Link Failure, So generally, we should focus on T200 expired drops, Radio Link Failure drops. Also Failed Outgoing Internal Inter-Cell Handovers (Timer Expired) drops are should be touched. Drop counters
Values Level 1 Level 2 Level 3 Level 4
Sum of CM33:Call Drops on Traffic Channel(times) Sum of CM33C:Call Drops on Radio Interface (Traffic Channel)(times) Sum of CM330:Call Drops on Radio Interface in Stable State (Traffic Channel)(times) Sum of CM3300:Call Drops on Traffic Channel in Stable State (Error Indication)(times)
16135 16081 14505 4947
100,0
Sum of M3100A:Ca l l Drops due to ERR IND Recei ved on TCHF (Tra ffi c Cha nnel ) i n Stabl e State (T200 Expi red)(times ) Sum of M3100B:Ca l l Drops due to ERR IND Recei ved on TCHF (Tra ffi c Cha nnel ) i n Stabl e State (Uns ol i ci ted DM Res pons e)(times ) Sum of M3100C:Ca l l Drops due to ERR IND Recei ved on TCHF (Tra ffi c Cha nnel ) i n Stabl e State (Sequence Error)(times ) Sum of M3200A:Ca l l Drops due to ERR IND Recei ved on TCHH (Tra ffi c Cha nnel ) i n Stabl e State (T200 Expi red)(times ) Sum of M3200B:Ca l l Drops due to ERR IND Recei ved on TCHH (Tra ffi c Cha nnel ) i n Stabl e State (Uns ol i ci ted DM Res pons e)(times ) Sum of M3200C:Ca l l Drops due to ERR IND Recei ved on TCHH (Tra ffi c Cha nnel ) i n Stabl e State (Sequence Error)(times )
4554 0 1 392 0 0
92,1 0,0 0,0 7,9 0,0 0,0
Sum of CM3301:Call Drops on Traffic Channel in Stable State (Connection Failure)(times)
9553
100,0
Sum of M3101A:Ca l l Drops due to CONN FAIL Recei ved on TCHF (Tra ffi c Cha nnel ) i n Stabl e State (Ra di o Li nk Fa i l ure)(times ) Sum of M3101B:Ca l l Drops due to CONN FAIL Recei ved on TCHF (Tra ffi c Cha nnel ) i n Stabl e State (HO Acces s Fa i l ure)(times ) Sum of M3101C:Ca l l Drops due to CONN FAIL Recei ved on TCHF (Tra ffi c Cha nnel ) i n Stabl e State (OM Intervention)(times ) Sum of M3101D:Ca l l Drops due to CONN FAIL Recei ved on TCHF (Tra ffi c Cha nnel ) i n Stabl e State (Ra di o Res ource Una va i l a bl e)(times ) Sum of M3101E:Ca l l Drops due to CONN FAIL Recei ved on TCHF (Tra ffi c Cha nnel ) i n Stabl e State (Other Ca us es )(times ) Sum of M3201A:Ca l l Drops due to CONN FAIL Recei ved on TCHH (Tra ffi c Cha nnel ) i n Stabl e State (Ra di o Li nk Fa i l ure)(times ) Sum of M3201B:Ca l l Drops due to CONN FAIL Recei ved on TCHH (Tra ffi c Cha nnel ) i n Stabl e State (HO Acces s Fa i l ure)(times ) Sum of M3201C:Ca l l Drops due to CONN FAIL Recei ved on TCHH (Tra ffi c Cha nnel ) i n Stabl e State (OM Intervention)(times ) Sum of M3201D:Ca l l Drops due to CONN FAIL Recei ved on TCHH (Tra ffi c Cha nnel ) i n Stabl e State (Ra di o Res ource Una va i l a bl e)(times ) Sum of M3201E:Ca l l Drops due to CONN FAIL Recei ved on TCHH (Tra ffi c Cha nnel ) i n Stabl e State (Other Ca us es )(times )
9079 6 0 0 0 468 0 0 0 0
95,0 0,1 0,0 0,0 0,0 4,9 0,0 0,0 0,0 0,0
Sum of CM3302:Call Drops on Traffic Channel in Stable State (Release Indication)(times)
5
100,0
Sum of M3102:Ca l l Drops due to REL IND Recei ved on TCHF (Tra ffi c Cha nnel )(times ) Sum of M3202:Ca l l Drops due to REL IND Recei ved on TCHH (Tra ffi c Cha nnel )(times )
5 0
100,0 0,0
Sum of CM331:Call Drops on Radio Interface in Handover State (Traffic Channel)(times)
1576
100,0
Sum of H3027Ca :Fa i l ed Sum of H3028Ca :Fa i l ed Sum of H3127Ca :Fa i l ed Sum of H3128Ca :Fa i l ed Sum of H3327Ca :Fa i l ed Sum of H3328Ca :Fa i l ed
1 4 1472 97 2 0
0,1 0,3 93,4 6,2 0,1 0,0
Interna l Intra -Cel l Ha ndovers (Ti mer Expi red) (TCHF) (Tra ffi c Cha nnel )(times ) Interna l Intra -Cel l Ha ndovers (Ti mer Expi red) (TCHH) (Tra ffi c Cha nnel )(times ) Outgoi ng Interna l Inter-Cel l Ha ndovers (Ti mer Expi red) (TCHF) (Tra ffi c Cha nnel )(times ) Outgoi ng Interna l Inter-Cel l Ha ndovers (Ti mer Expi red) (TCHH) (Tra ffi c Cha nnel )(times ) Outgoi ng Externa l Inter-Cel l Ha ndovers (T8 Expi red) (TCHF) (Tra ffi c Cha nnel )(times ) Outgoi ng Externa l Inter-Cel l Ha ndovers (T8 Expi red) (TCHH) (Tra ffi c Cha nnel )(times )
Sum of CM332:Call Drops due to No MRs from MS for a Long Time (Traffic Channel)(times) Sum of CM333:Call Drops due to Abis Terrestrial Link Failure (Traffic Channel)(times) Sum of CM334:Call Drops due to Equipment Failure (Traffic Channel)(times) Sum of CM335:Call Drops due to Forced Handover (Traffic Channel)(times)
2 0 45 7
100,0 34,1
100,0 90,2
100,0 99,7
65,9
0,0
9,8
0,0 0,0 0,3 0,0
3.2 CALL DROP REASONS for GENERAL CALL DROP TYPES Other drops like Abis Terrestrial Link Failure drop caused by Transmission Link broken, Equipment Failure drops caused by HW problems and Forced Handover drops caused by OM Intervention. These drops should be handled by separately. For these two general drop cause Radio Link Timeout and T200 Expired, the reasons are;
Coverage gaps, Quality or Interference problems, Unbalanced Path Losses, HW Fault or Installation faults, Parameter definition and OSS problems, Missing Neighbor Relations.
Also for other big percent of drop cause Failed Outgoing Internal Inter-Cell Handovers (Timer Expired), the reasons are;
Wrong or missing neighbor definitions, Wrong cell to cell neighbor parameters or timers, Coverage gaps, Quality or Interference problems, HW Faults or Installation faults.
3.3 TROUBLESHOOT STEPS FOR CALL DROP 3.3.1 PARAMETER PROBLEMS
First of all for a problematic cell, we should check general parameters of this cell and also this cell’s neighbor cells. Cells general parameters like; In Basic Attributes Parameter set; LAC, Layer of Cell, Cell Priority, Cell Extension Type, Cell IUO Type, MAX TA, RXLEV_ACCESS_MIN, TCH/F Uplink DTX, TCH/H Uplink DTX, Encryption Algorithm, UL PC Allowed, DL PC Allowed, Direct Retry, TCH/F Use Downlink DTX, TCH/H Downlink DTX should be checked. These would affect general quality of serving cell. If cell is a border cell or have external definitions in other BSCs or RNCs. All external definitions should be checked also. In Idle Mode Parameter set; BS-PA-MFRAMS, T3212, CRH, PI, CRO, TO, PT, NCC Permitted should be checked. These would affect service area of cell. In Other Attributes Parameter set; MS_TXPWR_MAX_CCH, STIRC Allowed, T3101, T3103A, T3103C, T7, T3107, T3121, T8, T3109, T3111, T3122 should be checked. These would affect general quality of serving cell. In Call Control Parameter set; Paging Times, MS MAX Retrans, SACCH Multi-Frames, AFR SACCH Multi-Frames, AHR SACCH Multi-Frames, AFR Radio Link Timeout, AHR Radio Link Timeout, Radio Link Timeout, T200 SDCCH, T200 FACCH/F, T200 FACCH/H, T200 SACCH TCH SAPI0, T200 SACCH TCH SAPI3, T200 SACCH SDCCH, T200 SDCCH SAPI3, Use LAPDm N200, N200 of Establish, N200 of Release, N200
of SACCH, N200 of SDCCH, N200 of FACH/Half rate, N200 of FACCH/Full rate should be checked. These would affect deciding time of drop events. In Handover Data Parameter set; Pathloss Ho. Enable, Co-BSC/MSC Adj, Intracell HO Allowed, Intracell F-H HO Allowed, Load HO Allowed, MS Fast Moving HO Allowed, Rx_Level_Drop HO Allowed, PBGT HO Allowed, Level HO Allowed, Fringe HO Allowed, BQ HO Allowed, TA HO Allowed, Concentric Circles HO Allowed, Interference HO Allowed, Quick Handover Enable, UtoO Traffic HO Allowed, Penalty Allowed, MR.Preprocessing, No Dl Mr.HO Allowed should be checked. These would affect HO performance and decision of serving cell. Also the parameters related with Watch Time/Valid Time should be checked. These would affect deciding faster or slower of HO. Also Cell to Cell neighbor definitions should be checked. Timer, hysteresis and thresholds between cells would affect HO performance between these cells.
3.3.2 PATH BALANCE PROBLEMS
COUNTER NUMBER S462A S462B S462C S462D S462E S462F S462G S462H S462I S462J S462K
COUNTER NAME Number of MRs (Uplink-and-Downlink Number of MRs (Uplink-and-Downlink Number of MRs (Uplink-and-Downlink Number of MRs (Uplink-and-Downlink Number of MRs (Uplink-and-Downlink Number of MRs (Uplink-and-Downlink Number of MRs (Uplink-and-Downlink Number of MRs (Uplink-and-Downlink Number of MRs (Uplink-and-Downlink Number of MRs (Uplink-and-Downlink Number of MRs (Uplink-and-Downlink
Balance Level Balance Level Balance Level Balance Level Balance Level Balance Level Balance Level Balance Level Balance Level Balance Level Balance Level
= = = = = = = = = = =
1)(times) 2)(times) 3)(times) 4)(times) 5)(times) 6)(times) 7)(times) 8)(times) 9)(times) 10)(times) 11)(times)
Path Balance is a statistic considering Uplink Path Loss and Downlink Path Loss. It is TRX based, so we could see unbalanced TRX or have an opinion about feeder connections. On left these counters are shown.
Formula is UL Path Loss- DL Path Loss. By counter meaning, “6” means difference is zero. So it is expected to be all samples in “6” ideally. More samples less than “3” means there is a DL Path Loss problem more samples greater than “8” means there is a UL Path Loss problem. These differences generally points out; HW Problems, TRX Power parameters differences, Cross-connections of feeder between sectors, RXU definitions, Send mode and Receive mode definitions problems. You should keep in mind that, if there is a TMA installation in sector path balance would shift to “1” or in use of PBT (Power Boost Technology) path balance would shift to “11” because of power changes. Also if there is a Power difference between TRXs of cells, it would affect path balance. In TRX definitions; Power Level, Power Fine Tune, Power Type parameters would decide maximum TRX output power.
There are sample stats of TRX based path balance statistic. As seen on the left for TRX1343 there is a Uplink path loss problem. HW Check should be done.
3.3.3 COVERAGE GAPS PROBLEMS
For finding coverage gaps;
”Numbers of MRs based on TA per TRX”, “Radio Link Failure Measurement based on TA per TRX”, “TCHF Receive Level Measurement per TRX”, “TCHH Receive Level Measurement per TRX” measurement sets should be used.
“Numbers of MRs based on TA per TRX” counters are shown below; These counters are MR samples in each TA based on TRX. COUNTER NUMBER S4400A S4401A S4402A S4403A S4404A S4405A S4406A S4407A S4408A S4409A S4410A S4411A S4412A S4413A S4414A S4415A S4416A S4417A S4418A S4419A S4420A S4421A S4422A S4423A S4424A S4425A S4426A S4427A S4428A S4429A S4430A S4432A S4434A S4436A S4438A S4440A S4445A S4450A S4455A S4463A
COUNTER NAME Num ber of MRs (TA = 0)(tim es ) Num ber of MRs (TA = 1)(tim es ) Num ber of MRs (TA = 2)(tim es ) Num ber of MRs (TA = 3)(tim es ) Num ber of MRs (TA = 4)(tim es ) Num ber of MRs (TA = 5)(tim es ) Num ber of MRs (TA = 6)(tim es ) Num ber of MRs (TA = 7)(tim es ) Num ber of MRs (TA = 8)(tim es ) Num ber of MRs (TA = 9)(tim es ) Num ber of MRs (TA = 10)(tim es ) Num ber of MRs (TA = 11)(tim es ) Num ber of MRs (TA = 12)(tim es ) Num ber of MRs (TA = 13)(tim es ) Num ber of MRs (TA = 14)(tim es ) Num ber of MRs (TA = 15)(tim es ) Num ber of MRs (TA = 16)(tim es ) Num ber of MRs (TA = 17)(tim es ) Num ber of MRs (TA = 18)(tim es ) Num ber of MRs (TA = 19)(tim es ) Num ber of MRs (TA = 20)(tim es ) Num ber of MRs (TA = 21)(tim es ) Num ber of MRs (TA = 22)(tim es ) Num ber of MRs (TA = 23)(tim es ) Num ber of MRs (TA = 24)(tim es ) Num ber of MRs (TA = 25)(tim es ) Num ber of MRs (TA = 26)(tim es ) Num ber of MRs (TA = 27)(tim es ) Num ber of MRs (TA = 28)(tim es ) Num ber of MRs (TA = 29)(tim es ) Num ber of MRs (TA = 30 or 31)(tim es ) Num ber of MRs (TA = 32 or 33)(tim es ) Num ber of MRs (TA = 34 or 35)(tim es ) Num ber of MRs (TA = 36 or 37)(tim es ) Num ber of MRs (TA = 38 or 39)(tim es ) Num ber of MRs (TA = 40 to 44)(tim es ) Num ber of MRs (TA = 45 to 49)(tim es ) Num ber of MRs (TA = 50 to 54)(tim es ) Num ber of MRs (TA = 55 to 63)(tim es ) Num ber of MRs (TA greater than 63)(tim es )
As seen in below graph, cells have some overshooting and coverage gaps.
COUNTER NUMBER COUNTER NAME S4400B
Ra di o Li nk Fa i l ures (TA = 0)(ti mes )
S4401B
Ra di o Li nk Fa i l ures (TA = 1)(ti mes )
S4402B
Ra di o Li nk Fa i l ures (TA = 2)(ti mes )
S4403B
Ra di o Li nk Fa i l ures (TA = 3)(ti mes )
S4404B
Ra di o Li nk Fa i l ures (TA = 4)(ti mes )
S4405B
Ra di o Li nk Fa i l ures (TA = 5)(ti mes )
S4406B
Ra di o Li nk Fa i l ures (TA = 6)(ti mes )
S4407B
Ra di o Li nk Fa i l ures (TA = 7)(ti mes )
S4408B
Ra di o Li nk Fa i l ures (TA = 8)(ti mes )
S4409B
Ra di o Li nk Fa i l ures (TA = 9)(ti mes )
S4410B
Ra di o Li nk Fa i l ures (TA = 10)(ti mes )
S4411B
Ra di o Li nk Fa i l ures (TA = 11)(ti mes )
S4412B
Ra di o Li nk Fa i l ures (TA = 12)(ti mes )
S4413B
Ra di o Li nk Fa i l ures (TA = 13)(ti mes )
S4414B
Ra di o Li nk Fa i l ures (TA = 14)(ti mes )
S4415B
Ra di o Li nk Fa i l ures (TA = 15)(ti mes )
S4416B
Ra di o Li nk Fa i l ures (TA = 16)(ti mes )
S4417B
Ra di o Li nk Fa i l ures (TA = 17)(ti mes )
S4418B
Ra di o Li nk Fa i l ures (TA = 18)(ti mes )
S4419B
Ra di o Li nk Fa i l ures (TA = 19)(ti mes )
S4420B
Ra di o Li nk Fa i l ures (TA = 20)(ti mes )
S4421B
Ra di o Li nk Fa i l ures (TA = 21)(ti mes )
S4422B
Ra di o Li nk Fa i l ures (TA = 22)(ti mes )
S4423B
Ra di o Li nk Fa i l ures (TA = 23)(ti mes )
S4424B
Ra di o Li nk Fa i l ures (TA = 24)(ti mes )
S4425B
Ra di o Li nk Fa i l ures (TA = 25)(ti mes )
S4426B
Ra di o Li nk Fa i l ures (TA = 26)(ti mes )
S4427B
Ra di o Li nk Fa i l ures (TA = 27)(ti mes )
S4428B
Ra di o Li nk Fa i l ures (TA = 28)(ti mes )
S4429B
Ra di o Li nk Fa i l ures (TA = 29)(ti mes )
S4430B
Ra di o Li nk Fa i l ures (TA = 30 or 31)(ti mes )
S4432B
Ra di o Li nk Fa i l ures (TA = 32 or 33)(ti mes )
S4434B
Ra di o Li nk Fa i l ures (TA = 34 or 35)(ti mes )
S4436B
Ra di o Li nk Fa i l ures (TA = 36 or 37)(ti mes )
S4438B
Ra di o Li nk Fa i l ures (TA = 38 or 39)(ti mes )
S4440B
Ra di o Li nk Fa i l ures (TA = 40 to 44)(ti mes )
S4445B
Ra di o Li nk Fa i l ures (TA = 45 to 49)(ti mes )
S4450B
Ra di o Li nk Fa i l ures (TA = 50 to 54)(ti mes )
S4455B
Ra di o Li nk Fa i l ures (TA = 55 to 63)(ti mes )
S4463B
Ra di o Li nk Fa i l ures (TA grea ter tha n 63)(ti mes )
“Radio Link Failure Measurement based on TA per TRX” counters are shown on the left;
From “Radio Link Failure Measurement based on TA per TRX” counters, you would have an idea of where cells drop generally occurs. If it is gathered to one TA, it could be said that in that TA area there is a coverage problem. “TCHF Receive Level Measurement per TRX ” counters are shown below. There are 128 counter for each RxLevel between 07 (-110 dBm—47 dBm), RxQuality between 0-7. COUNTER NUMBER S4100B S4101B S4102B S4103B S4104B S4105B S4106B S4107B S4110B S4111B S4112B S4113B S4114B S4115B S4116B S4117B S4120B S4121B S4122B S4123B S4124B S4125B S4126B S4127B S4130B S4131B S4132B S4133B S4134B S4135B S4136B S4137B S4140B S4141B S4142B S4143B S4144B S4145B S4146B S4147B S4150B S4151B S4152B S4153B S4154B S4155B S4156B S4157B S4160B S4161B S4162B S4163B S4164B S4165B S4166B S4167B S4170B S4171B S4172B S4173B S4174B S4175B S4176B S4177B
COUNTER NAME Number of MRs on Downlink TCHF (Receive Level Rank 0 and Receive Quality Rank 0)(times) Number of MRs on Downlink TCHF (Receive Level Rank 0 and Receive Quality Rank 1)(times) Number of MRs on Downlink TCHF (Receive Level Rank 0 and Receive Quality Rank 2)(times) Number of MRs on Downlink TCHF (Receive Level Rank 0 and Receive Quality Rank 3)(times) Number of MRs on Downlink TCHF (Receive Level Rank 0 and Receive Quality Rank 4)(times) Number of MRs on Downlink TCHF (Receive Level Rank 0 and Receive Quality Rank 5)(times) Number of MRs on Downlink TCHF (Receive Level Rank 0 and Receive Quality Rank 6)(times) Number of MRs on Downlink TCHF (Receive Level Rank 0 and Receive Quality Rank 7)(times) Number of MRs on Downlink TCHF (Receive Level Rank 1 and Receive Quality Rank 0)(times) Number of MRs on Downlink TCHF (Receive Level Rank 1 and Receive Quality Rank 1)(times) Number of MRs on Downlink TCHF (Receive Level Rank 1 and Receive Quality Rank 2)(times) Number of MRs on Downlink TCHF (Receive Level Rank 1 and Receive Quality Rank 3)(times) Number of MRs on Downlink TCHF (Receive Level Rank 1 and Receive Quality Rank 4)(times) Number of MRs on Downlink TCHF (Receive Level Rank 1 and Receive Quality Rank 5)(times) Number of MRs on Downlink TCHF (Receive Level Rank 1 and Receive Quality Rank 6)(times) Number of MRs on Downlink TCHF (Receive Level Rank 1 and Receive Quality Rank 7)(times) Number of MRs on Downlink TCHF (Receive Level Rank 2 and Receive Quality Rank 0)(times) Number of MRs on Downlink TCHF (Receive Level Rank 2 and Receive Quality Rank 1)(times) Number of MRs on Downlink TCHF (Receive Level Rank 2 and Receive Quality Rank 2)(times) Number of MRs on Downlink TCHF (Receive Level Rank 2 and Receive Quality Rank 3)(times) Number of MRs on Downlink TCHF (Receive Level Rank 2 and Receive Quality Rank 4)(times) Number of MRs on Downlink TCHF (Receive Level Rank 2 and Receive Quality Rank 5)(times) Number of MRs on Downlink TCHF (Receive Level Rank 2 and Receive Quality Rank 6)(times) Number of MRs on Downlink TCHF (Receive Level Rank 2 and Receive Quality Rank 7)(times) Number of MRs on Downlink TCHF (Receive Level Rank 3 and Receive Quality Rank 0)(times) Number of MRs on Downlink TCHF (Receive Level Rank 3 and Receive Quality Rank 1)(times) Number of MRs on Downlink TCHF (Receive Level Rank 3 and Receive Quality Rank 2)(times) Number of MRs on Downlink TCHF (Receive Level Rank 3 and Receive Quality Rank 3)(times) Number of MRs on Downlink TCHF (Receive Level Rank 3 and Receive Quality Rank 4)(times) Number of MRs on Downlink TCHF (Receive Level Rank 3 and Receive Quality Rank 5)(times) Number of MRs on Downlink TCHF (Receive Level Rank 3 and Receive Quality Rank 6)(times) Number of MRs on Downlink TCHF (Receive Level Rank 3 and Receive Quality Rank 7)(times) Number of MRs on Downlink TCHF (Receive Level Rank 4 and Receive Quality Rank 0)(times) Number of MRs on Downlink TCHF (Receive Level Rank 4 and Receive Quality Rank 1)(times) Number of MRs on Downlink TCHF (Receive Level Rank 4 and Receive Quality Rank 2)(times) Number of MRs on Downlink TCHF (Receive Level Rank 4 and Receive Quality Rank 3)(times) Number of MRs on Downlink TCHF (Receive Level Rank 4 and Receive Quality Rank 4)(times) Number of MRs on Downlink TCHF (Receive Level Rank 4 and Receive Quality Rank 5)(times) Number of MRs on Downlink TCHF (Receive Level Rank 4 and Receive Quality Rank 6)(times) Number of MRs on Downlink TCHF (Receive Level Rank 4 and Receive Quality Rank 7)(times) Number of MRs on Downlink TCHF (Receive Level Rank 5 and Receive Quality Rank 0)(times) Number of MRs on Downlink TCHF (Receive Level Rank 5 and Receive Quality Rank 1)(times) Number of MRs on Downlink TCHF (Receive Level Rank 5 and Receive Quality Rank 2)(times) Number of MRs on Downlink TCHF (Receive Level Rank 5 and Receive Quality Rank 3)(times) Number of MRs on Downlink TCHF (Receive Level Rank 5 and Receive Quality Rank 4)(times) Number of MRs on Downlink TCHF (Receive Level Rank 5 and Receive Quality Rank 5)(times) Number of MRs on Downlink TCHF (Receive Level Rank 5 and Receive Quality Rank 6)(times) Number of MRs on Downlink TCHF (Receive Level Rank 5 and Receive Quality Rank 7)(times) Number of MRs on Downlink TCHF (Receive Level Rank 6 and Receive Quality Rank 0)(times) Number of MRs on Downlink TCHF (Receive Level Rank 6 and Receive Quality Rank 1)(times) Number of MRs on Downlink TCHF (Receive Level Rank 6 and Receive Quality Rank 2)(times) Number of MRs on Downlink TCHF (Receive Level Rank 6 and Receive Quality Rank 3)(times) Number of MRs on Downlink TCHF (Receive Level Rank 6 and Receive Quality Rank 4)(times) Number of MRs on Downlink TCHF (Receive Level Rank 6 and Receive Quality Rank 5)(times) Number of MRs on Downlink TCHF (Receive Level Rank 6 and Receive Quality Rank 6)(times) Number of MRs on Downlink TCHF (Receive Level Rank 6 and Receive Quality Rank 7)(times) Number of MRs on Downlink TCHF (Receive Level Rank 7 and Receive Quality Rank 0)(times) Number of MRs on Downlink TCHF (Receive Level Rank 7 and Receive Quality Rank 1)(times) Number of MRs on Downlink TCHF (Receive Level Rank 7 and Receive Quality Rank 2)(times) Number of MRs on Downlink TCHF (Receive Level Rank 7 and Receive Quality Rank 3)(times) Number of MRs on Downlink TCHF (Receive Level Rank 7 and Receive Quality Rank 4)(times) Number of MRs on Downlink TCHF (Receive Level Rank 7 and Receive Quality Rank 5)(times) Number of MRs on Downlink TCHF (Receive Level Rank 7 and Receive Quality Rank 6)(times) Number of MRs on Downlink TCHF (Receive Level Rank 7 and Receive Quality Rank 7)(times)
COUNTER NUMBER S4100A S4101A S4102A S4103A S4104A S4105A S4106A S4107A S4110A S4111A S4112A S4113A S4114A S4115A S4116A S4117A S4120A S4121A S4122A S4123A S4124A S4125A S4126A S4127A S4130A S4131A S4132A S4133A S4134A S4135A S4136A S4137A S4140A S4141A S4142A S4143A S4144A S4145A S4146A S4147A S4150A S4151A S4152A S4153A S4154A S4155A S4156A S4157A S4160A S4161A S4162A S4163A S4164A S4165A S4166A S4167A S4170A S4171A S4172A S4173A S4174A S4175A S4176A S4177A
COUNTER NAME Number of MRs on Uplink TCHF (Receive Level Rank 0 and Receive Quality Rank 0)(times) Number of MRs on Uplink TCHF (Receive Level Rank 0 and Receive Quality Rank 1)(times) Number of MRs on Uplink TCHF (Receive Level Rank 0 and Receive Quality Rank 2)(times) Number of MRs on Uplink TCHF (Receive Level Rank 0 and Receive Quality Rank 3)(times) Number of MRs on Uplink TCHF (Receive Level Rank 0 and Receive Quality Rank 4)(times) Number of MRs on Uplink TCHF (Receive Level Rank 0 and Receive Quality Rank 5)(times) Number of MRs on Uplink TCHF (Receive Level Rank 0 and Receive Quality Rank 6)(times) Number of MRs on Uplink TCHF (Receive Level Rank 0 and Receive Quality Rank 7)(times) Number of MRs on Uplink TCHF (Receive Level Rank 1 and Receive Quality Rank 0)(times) Number of MRs on Uplink TCHF (Receive Level Rank 1 and Receive Quality Rank 1)(times) Number of MRs on Uplink TCHF (Receive Level Rank 1 and Receive Quality Rank 2)(times) Number of MRs on Uplink TCHF (Receive Level Rank 1 and Receive Quality Rank 3)(times) Number of MRs on Uplink TCHF (Receive Level Rank 1 and Receive Quality Rank 4)(times) Number of MRs on Uplink TCHF (Receive Level Rank 1 and Receive Quality Rank 5)(times) Number of MRs on Uplink TCHF (Receive Level Rank 1 and Receive Quality Rank 6)(times) Number of MRs on Uplink TCHF (Receive Level Rank 1 and Receive Quality Rank 7)(times) Number of MRs on Uplink TCHF (Receive Level Rank 2 and Receive Quality Rank 0)(times) Number of MRs on Uplink TCHF (Receive Level Rank 2 and Receive Quality Rank 1)(times) Number of MRs on Uplink TCHF (Receive Level Rank 2 and Receive Quality Rank 2)(times) Number of MRs on Uplink TCHF (Receive Level Rank 2 and Receive Quality Rank 3)(times) Number of MRs on Uplink TCHF (Receive Level Rank 2 and Receive Quality Rank 4)(times) Number of MRs on Uplink TCHF (Receive Level Rank 2 and Receive Quality Rank 5)(times) Number of MRs on Uplink TCHF (Receive Level Rank 2 and Receive Quality Rank 6)(times) Number of MRs on Uplink TCHF (Receive Level Rank 2 and Receive Quality Rank 7)(times) Number of MRs on Uplink TCHF (Receive Level Rank 3 and Receive Quality Rank 0)(times) Number of MRs on Uplink TCHF (Receive Level Rank 3 and Receive Quality Rank 1)(times) Number of MRs on Uplink TCHF (Receive Level Rank 3 and Receive Quality Rank 2)(times) Number of MRs on Uplink TCHF (Receive Level Rank 3 and Receive Quality Rank 3)(times) Number of MRs on Uplink TCHF (Receive Level Rank 3 and Receive Quality Rank 4)(times) Number of MRs on Uplink TCHF (Receive Level Rank 3 and Receive Quality Rank 5)(times) Number of MRs on Uplink TCHF (Receive Level Rank 3 and Receive Quality Rank 6)(times) Number of MRs on Uplink TCHF (Receive Level Rank 3 and Receive Quality Rank 7)(times) Number of MRs on Uplink TCHF (Receive Level Rank 4 and Receive Quality Rank 0)(times) Number of MRs on Uplink TCHF (Receive Level Rank 4 and Receive Quality Rank 1)(times) Number of MRs on Uplink TCHF (Receive Level Rank 4 and Receive Quality Rank 2)(times) Number of MRs on Uplink TCHF (Receive Level Rank 4 and Receive Quality Rank 3)(times) Number of MRs on Uplink TCHF (Receive Level Rank 4 and Receive Quality Rank 4)(times) Number of MRs on Uplink TCHF (Receive Level Rank 4 and Receive Quality Rank 5)(times) Number of MRs on Uplink TCHF (Receive Level Rank 4 and Receive Quality Rank 6)(times) Number of MRs on Uplink TCHF (Receive Level Rank 4 and Receive Quality Rank 7)(times) Number of MRs on Uplink TCHF (Receive Level Rank 5 and Receive Quality Rank 0)(times) Number of MRs on Uplink TCHF (Receive Level Rank 5 and Receive Quality Rank 1)(times) Number of MRs on Uplink TCHF (Receive Level Rank 5 and Receive Quality Rank 2)(times) Number of MRs on Uplink TCHF (Receive Level Rank 5 and Receive Quality Rank 3)(times) Number of MRs on Uplink TCHF (Receive Level Rank 5 and Receive Quality Rank 4)(times) Number of MRs on Uplink TCHF (Receive Level Rank 5 and Receive Quality Rank 5)(times) Number of MRs on Uplink TCHF (Receive Level Rank 5 and Receive Quality Rank 6)(times) Number of MRs on Uplink TCHF (Receive Level Rank 5 and Receive Quality Rank 7)(times) Number of MRs on Uplink TCHF (Receive Level Rank 6 and Receive Quality Rank 0)(times) Number of MRs on Uplink TCHF (Receive Level Rank 6 and Receive Quality Rank 1)(times) Number of MRs on Uplink TCHF (Receive Level Rank 6 and Receive Quality Rank 2)(times) Number of MRs on Uplink TCHF (Receive Level Rank 6 and Receive Quality Rank 3)(times) Number of MRs on Uplink TCHF (Receive Level Rank 6 and Receive Quality Rank 4)(times) Number of MRs on Uplink TCHF (Receive Level Rank 6 and Receive Quality Rank 5)(times) Number of MRs on Uplink TCHF (Receive Level Rank 6 and Receive Quality Rank 6)(times) Number of MRs on Uplink TCHF (Receive Level Rank 6 and Receive Quality Rank 7)(times) Number of MRs on Uplink TCHF (Receive Level Rank 7 and Receive Quality Rank 0)(times) Number of MRs on Uplink TCHF (Receive Level Rank 7 and Receive Quality Rank 1)(times) Number of MRs on Uplink TCHF (Receive Level Rank 7 and Receive Quality Rank 2)(times) Number of MRs on Uplink TCHF (Receive Level Rank 7 and Receive Quality Rank 3)(times) Number of MRs on Uplink TCHF (Receive Level Rank 7 and Receive Quality Rank 4)(times) Number of MRs on Uplink TCHF (Receive Level Rank 7 and Receive Quality Rank 5)(times) Number of MRs on Uplink TCHF (Receive Level Rank 7 and Receive Quality Rank 6)(times) Number of MRs on Uplink TCHF (Receive Level Rank 7 and Receive Quality Rank 7)(times)
As seen above, in that TRX there is some Uplink signal level problem. Cross connection, VSWR may be problem. As a result, according to TA distribution, RLT over TA distribution and TCH Receive Level measurements; If cell’s TA distribution shows cell covers a big area with overshoots, coverage gap related call drop may occur. If cell’s RLT over TA and TA distribution shows together, cell cover a big area and drop gathers in one TA (or some of TA), coverage gap related call drop may occur. If cell’s TCH Receive Level measurements shows cells have unbalanced uplink and downlink RxLevels, it means cell is a dragon cells with overshoot service areas or have HW problem. For solutions of coverage gaps and overshoot problems, cells antenna direction, height, mechanic and electric tilt degree may be changed or cell addition may be done. For HW problems, HW check should be done detailed.
3.3.4 QUALITY and INTERFERENCE PROBLEMS
For finding quality and interference problems;
“Interference Band Measurement per Cell”, “Neighbor Cell Level Measurement per Cell”, “TCHF Receive Level Measurement per TRX”, “TCHH Receive Level Measurement per TRX” measurement sets should be used.
“Interference Band Measurement per Cell” counters are shown below;
COUNTER NUMBER AS4200A AS4200B AS4200C AS4200D AS4200E AS4207A AS4207B AS4207C AS4207D AS4207E AS4208A AS4208B AS4208C AS4208D AS4208E
COUNTER NAME Mean Number of SDCCHs in Interference Band 1(number) Mean Number of SDCCHs in Interference Band 2(number) Mean Number of SDCCHs in Interference Band 3(number) Mean Number of SDCCHs in Interference Band 4(number) Mean Number of SDCCHs in Interference Band 5(number) Mean Number of TCHFs in Interference Band 1(number) Mean Number of TCHFs in Interference Band 2(number) Mean Number of TCHFs in Interference Band 3(number) Mean Number of TCHFs in Interference Band 4(number) Mean Number of TCHFs in Interference Band 5(number) Mean Number of TCHHs in Interference Band 1(number) Mean Number of TCHHs in Interference Band 2(number) Mean Number of TCHHs in Interference Band 3(number) Mean Number of TCHHs in Interference Band 4(number) Mean Number of TCHHs in Interference Band 5(number)
With these counters, BTS measure uplink interference according to below signal level table. If there is interference, it means that Band5 counters should be incremented. Interference Band Interference band 1 Interference band 2 Interference band 3 Interference band 4 Interference band 5
Level Threshold of the Interference Band -105 dBm to -98 dBm -98 dBm to -90 dBm -90 dBm to -87 dBm -87 dBm to -85 dBm -85 dBm to -47 dBm
As seen above, generally this TRX has less interference If Band5 numbers is high, it means cell have uplink interference and frequency change should be considered. (Keep in mind that BB Hopping will affect this result, for test hopping should be closed)
“Neighbor Cell Level Measurement per Cell” counters are shown below.
COUNTER NUMBER COUNTER NAME S363
Number of MRs in Which the Signal Strength Difference Between the Serving Cell and the Neighbor Cell is Smaller Than the Neighbor Cell Interference Level Threshold 1(number)
S364
Number of MRs in Which the Signal Strength Difference Between the Serving Cell and the Neighbor Cell is Greater Than the Neighbor Cell Interference Level Threshold 1(number)
S365
Number of MRs in Which the Signal Strength Difference Between the Serving Cell and the Neighbor Cell is Greater Than the Neighbor Cell Interference Level Threshold 2(number)
S366
Number of MRs in Which the Signal Strength Difference Between the Serving Cell and the Neighbor Cell is Greater Than the Neighbor Cell Interference Level Threshold 3(number)
S367
Number of MRs in Which the Signal Strength Difference Between the Serving Cell and the Neighbor Cell is Greater Than the Neighbor Cell Interference Level Threshold 4(number)
S368
Number of MRs in Which the Signal Strength Difference Between the Serving Cell and the Neighbor Cell is Greater Than the Neighbor Cell Interference Level Threshold 5(number)
S369
Number of MRs in Which the Signal Strength Difference Between the Serving Cell and the Neighbor Cell is Greater Than the Neighbor Cell Interference Level Threshold 6(number)
S370
Number of MRs in Which the Signal Strength Difference Between the Serving Cell and the Neighbor Cell is Greater Than the Neighbor Cell Interference Level Threshold 7(number)
INNER PARAMETER Name Neighbour Cell Interference Level Neighbour Cell Interference Level Neighbour Cell Interference Level Neighbour Cell Interference Level Neighbour Cell Interference Level Neighbour Cell Interference Level Neighbour Cell Interference Level Neighbour Cell Interference Level
Value Threshold 0 Threshold 1 Threshold 2 Threshold 3 Threshold 4 Threshold 5 Threshold 6 Threshold 7
0 49 55 61 64 67 73 79
According to inner BSC parameter settings, these counters incremented when measured Neighbor Cell signal level and serving cell signal level difference greater than related threshold. These thresholds are shown on the left.
As seen below, serving cell measures all BCCH in its active Ba List and decodes BSIC (not needed to be neighbor, but BCCH frequency should be in active Ba List). According to thresholds, co-channel and adjacent channel interferer of serving cells could be found.
“TCHF Receive Level Measurement per TRX” counter may be used for detecting interference problem also. Quality problems like high Rxquality may be caused by low signal level. But interference means quality is bad in good signal level also. As seen below with these counters, quality in good and bad signal levels for uplink and downlink could be detected.
As seen upper graph shows uplink RxLevel-RxQual distribution, lower graph shows downlink RxLevel-RxQual distribution. From the graphs, it could be said that, there is an uplink signal level problem but no interference problem.
As a result, if quality problems exist in a cell, with help of above stats we should define is there an adjacent or cochannel frequency or is it related with signal level. If it is frequency, with help of neighbor cell level measurement we could find the best frequency for cell. If it is a signal level problem we should analysis for coverage gap and HW problems.
3.3.5 MISSING NEIGHBOR PROBLEMS
Another cause of high drop rate is missing neighbor. Missing neighbor may be a real closer cell to serving cell or because of serving cell overshoot there is a far away cell that should be neighbor. Best way to find missing neighbor is analysis with help of “Neighbor Cell Level Measurement per Cell” counters. These counters collects all BCCH-BSIC reported by MS in MRs for serving cell. By thresholds in BSC Parameters, related counter is incremented according to signal level difference between serving cell and measured BCCH-BSIC. For finding missing neighbor, we should collect “Neighbor Cell Level Measurement per Cell” for a period (keep in mind that active ba list of serving cell should be modified as contain all BCCHs). Than with help of MRs on TCHs counter, you could find which BCCH-BSICs are measured above a certain threshold. Than in these measured BCCH-BSICs, which ones are defined as neighbor which ones are not, you could find. (Keep in mind that same BCCH-BSIC in an area may affect reliability of result. So try to give same BCCH-BSIC to cells that distance between them are as far as you can). For example from analysis this cell should be defined as neighbor with serving cell.
