2g Radio Network Optimization Training ( Practical Workshop)
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2G Radio Network Optimization Technology Training Network Planning & Optimization Veeresh N
1
© Nokia Siemens Networks
NPO 2G Radio Network Optimization Technology Workshop--veeresh
Course Outline •
DAY 1---CALL FLOW ( MTC& MOC)& Network Optimization Principles( Parameters ,Hoc, Poc, Timers)
•
DAY2- Network Performance Optimization(Counters, KPIs, ND Reports)
•
DAY 3-- AMR TRAINING & FEATURES PRESENTATION(Robust AMR , AMR PPC, SAL)
Soc Classification level 2 © Nokia Siemens Networks
Contents Channels –Basics Mobile Originated Call—MOC Mobile Terminating Call—MTC Handover control ---HOC Power Control –POC Parameters Timers
Soc Classification level 3 © Nokia Siemens Networks
Presentation / Author / Date
Logical Channels on Air interface LOGICAL CHANNELS
DEDICATED CHANNELS
COMMON CHANNELS
COMMON CONTROL CHANNELS
BROADCAST CHANNELS
FCCH
SCH
BCCH
PCH
DEDICATED CONTROL CHANNELS
SDCCH
RACH
AGCH
SACCH
TRAFFIC CHANNELS
FACCH
TCH/F
TCH/H 4
4
© Nokia Siemens Networks
TCH/EFR
GSM Channels GSM Channels Traffic Channels (TCHs)
Control Channels
Broadcast Channels (BCHs) Full rate
Half rate
Common Control Channels (CCCHs)
Dedicated Control Channels (DCCHs) (down uplink)
Downlink
Downlink
Uplink Fast
Slow
TCH /F TCH /HFCCH SCH BCCHPCH AGCH CBCH RACHSDCCH FACCH SACCH Traffic Multiframing Soc Classification level 5 © Nokia Siemens Networks
Signaling Multiframing
Traffic Multiframin 5
The Logical Channels on Radio Interface TS
0123456 7
BTS
MS FCCH
TCH
Frequency correction Synchronization
Traffic (speech-data) SCH
FACCH
Associated Signaling
BCCH Broadcast control RACH Access request Subscriber paging Answer to Access request
PCH
SACCH SDCCH
Radio Measurement + SMS Dedicated Signaling
CBCH Broadcast info
AGCH FCCH CBCH
Broadcast info Dedicated Signaling
SDCCH SACCH
Sys InFo 5, 6 + SMS
SCH
M.S. Pre-synchronization
BCCH RACH Access request PCH
Traffic (speech data) TCH Associated Signaling FACCH Soc Classification level 6 © Nokia Siemens Networks
Subscriber paging AGCH
Answer to Access request
6
Logical Channel Description (1/2) SACCH MESSAGES TCH MESSAGES Measures:
- power level of the communication
• Speech
- quality level of the communication
• Data
- level on the beacon frequency of the
• Handover Access message (uplink)
neighboring cells • Timing Advance
• Power Control • SMS
FACCH MESSAGES • Connection establishment from SDCCH
to TCH SDCCH MESSAGES • Request for a SDCCH assignment • Request for the end of channel
assignment • Order of commutation from SDCCH to
TCH • SMS Soc Classification level 7 © Nokia Siemens Networks
• End validation of a SDCCH-TCH
commutation • Characteristics of the future used BS
after handover • Connection establishment to BS after
handover • Validation of an handover
7
Logical Channel Description (2/2) FCCH MESSAGES
AGCH MESSAGES
• no message is sent (all bits 0)
• For dedicated channel assignment:
SCH MESSAGES • Frame Number
- frequency number - slot number - frequency hopping description - Timing Advance (1st estimation) - MS identification
• Base Station Identity Code (BSIC)
CBCH MESSAGES BCCH MESSAGES
• Specific information
(weather, road information • System Information type 1, 2, 2bis,
2ter, 3, 4, 7, 8 (idle mode)
RACH MESSAGES • Service request:
PCH MESSAGES • messages containing a mobile
identity for a call, a short message or an authentication Soc Classification level 8 © Nokia Siemens Networks
- emergency call - answer to an incoming call - outgoing call - short message - call re-establishment - inscription
8
Mobile Originated Call – – – – – – –
Request for Service Authentication Ciphering Equipment Validation Call Setup Handovers Call Release
Soc Classification level 9 © Nokia Siemens Networks
9
Call establishment from a mobile--MOC Mobile looks for BCCH after switching on RACH send channel request AGCH receive SDCCH
SDCCH send call establishment request SDCCH do the authentication and TMSI allocation SDCCH send the setup message and desired number
SDCCH require traffic channel assignment FACCH switch to traffic channel and send ack (steal bits) FACCH receive alert signal ringing sound FACCH receive connect message FACCH acknowledge connect message and use TCH Soc Classification level 10 © Nokia Siemens Networks
TCH conversation continues
Call establishment from a mobile--MOC csf_1a csf_2e
csf_2e
Soc Classification level 11 © Nokia Siemens Networks
CONTINUE
csf_2e
blck_8d dcr_3i dcr_3j dcr_4e blck_29
dcr_8c dcr_8e
dcr_5a Soc Classification level 12 © Nokia Siemens Networks
dcr_5a dcr_8c dcr_8e
dcr_3i dcr_3j dcr_4e
Soc Classification level 13 © Nokia Siemens Networks
Call establishment to a mobile--MTC Mobile looks for BCCH after switching on Mobile receives paging message on PCH Generate Channel Request on RACH Receive signaling channel SDCCH on AGCH Answer paging message on SDCCH Receive authentication request on SDCCH
Authenticate on SDCCH Receive setup message on SDCCH Receive traffic channel assignment on SDCCH
FACCH switch to traffic channel and send ack (steal bits) Receive alert signal and generate ringing on FACCH Receive connect message on FACCH Soc Classification level 14 © Nokia Siemens Networks
FACCH acknowledge connect message and switch to TCH
Mobile Terminated Call MS Paging Request Channel Req
Imm Assgn Paging Response
Paging Command
Channel Actvn Chan Actvn Ack Imm Assgn Establish ind
Alert Connect Connect Ack Speech
Company Confidential
Paging
Channel Reqd
CM Service Accept Security Procedures Set Up Call Proceeding TCH Assignment
Soc Classification level 15 © Nokia Siemens Networks
MSC
BSC
BTS
CL3 Informant
Paging
Paging is process by which Mobile receives incoming calls Mobile has to monitor the paging channel to receive paging messages Mobile will not monitor all paging channels, it will monitor the channel specific to its CCCH_Group and Paging Group
CCCH_ GROUP
BCCH defines the number of PCHN ( timeslots ) supporting CCCH CCCH can be allocated only to TN 0,2,4,6 CCCH will have the same structure on all allocated timeslots ( 9 blocks ) Each PCHN supporting CCCH is alloted a CCCH_Group No ( range : 0 .. 3 ) Each CCCH_Group carries its own group of Mobiles. Mobiles will listen to paging messages and send RACH's only in their specific group
0 1 2 3 4 5 7 6
B D C T C T C T 9 b l o c k s 9 b l o c k s 9 b l o c k s 9 b l o c k s
Soc Classification level 16 © Nokia Siemens Networks
Company Confidential
Paging Group
Within the CCCH_Group , Mobile listen to paging in specific paging (CCCH) blocks only The block specific to a mobile is its Paging Group
T N
F S B C F S C C F S C C F S C C F S C C I 0 D 1
I S B C I I C C I I C C I I C C I I C C I 2 T 3
I S B C I I C C I I C C I I C C I I C C I 4 T 5
I S B C I I C C I I C C I I C C I I C C I 6 T 7
C C C H _ G R O U P
Soc Classification level 17 © Nokia Siemens Networks
Company Confidential
P a g i n g G r o u p
Paging How to derive CCCH_Group and Paging Group for a mobile ? Let us understand some parameters required to achieve this .
1. BS_CC_CHANS : Total No of PCHN supporting CCCH ( Sys Info Type 3 ) Range : 1 - 4 2. BS_AG_BLKS_RES : Blocks reserved for AGCH 3. BS_PA_MFRMS : Multiframe Repetition rate
4. IMSI : 15 digit Mobile Identity
We will now understand 2 & 3
Soc Classification level 18 © Nokia Siemens Networks
Company Confidential
Paging Available Paging Blocks on 1 CCCH_Group Available Paging Blocks = CCCH Blocks -- bs_ag_blks_res Maximum AGCH Reservation for Non-Combined = 7 Available Paging Blocks = 2 Maximum AGCH Reservation for Combined = 2 Available Paging Blocks = 1 Mimimum AGCH Reservartion for Non-Combined = 0 Available Paging Blocks = 9 Minimum AGCH Reservation for Combined =0 Available Paging Blocks = 3 No of Paging Blocks will have a range of 1 - 9 Soc Classification level 19 © Nokia Siemens Networks
Company Confidential
Paging BS_PA_MFRMS -- No of Multiframes after which Same Paging Group is repeated -- This Parameter is broadcasted on BCCH -- Ranges between 0 -- 9 Multiframes
F S B A F S A A F S A A F S A A F S I P 0 P 1
M F 2
F S B A F S A A F S A A F S A A F S I P 2 P 3
M F 3
F S B A F S A A F S A A F S A A F S I P 0 P 1
Mobile belonging to Paging Group P0 will remain idle during P1 ,P2,P3 Mobile utilizes power only during PO. This is known as DRX Soc Classification level 20 © Nokia Siemens Networks
Company Confidential
Paging Total No of Paging Groups on 1 CCCH_Group ( N )
No of Paging Groups = Paging Blocks x Repitition of Paging BLock N = [ CCCH - bs_ag_blks_res ] x bs_pa_mfrms
Range of Paging Groups on 1 CCCH_Group Minimum Available Paging Groups = Min Pag blocks x Min bs_pa_mfrms = 1 x 1 = 1 Maximum Available Paging Groups = Max Pag blocks x Max bs_pa_mfrms = 9 x 9 = 81
Soc Classification level 21 © Nokia Siemens Networks
Company Confidential
Paging How does a Mobile knows it CCCH_Group Paging Group No ?
CCCH_Group = [ ( IMSI mod 1000 ) mod ( BS_CC_CHANS x N ) ] div N
Pag Grp No = [ ( IMSI mod 1000 ) mod ( BS_CC_CHANS x N ) ] mod N
N = Total Paging Groups = No of Paging Blocks x bs_pa_mfrms
Soc Classification level 22 © Nokia Siemens Networks
Company Confidential
HOW TO WORK OUT WHICH PAGING GROUP AN MS IS ASSIGNED TO • •
The paging group is determined by the following: PAGING GROUP = {(IMSI mod 1000) mod [BS_CC_CHANS*N]} mod N
•
Where N = No of Paging Groups = No of PCH x BS_PA_MFRMS IMSI = International Mobile Subscriber Identity Mod = MODULUS (see additional notes on modulus at the end) BS_CC_CHANS = CCCH (COMBINED (3) or NONCOMBINED (9)) Example: Assuming that the relevant parameters for the calculation are as follows: IMSI= 460003811319045 N = Number of Paging Groups (For this we will assume there are 28 Paging Groups) Mod = Scientific calculation. Full notes at end explaining mod. BS_CC_CHANS = 9 (As we will assume for this that NON-COMBINED Signaling is in use)
Soc Classification level 23 © Nokia Siemens Networks
23
© 2005 Nokia
V1-Filename.ppt / 2005-02-15/ sr
CALCULATION So the calculation {(IMSI mod 1000) mod [BS_CC_CHANS*N]} mod N based on the information in the previous slide would be as follows: {(460003811319045 mod 1000) mod [ 9 * 28 ]} mod 28 STEP1. (IMSI mod 1000) = (460003811319045 mod 1000) 460003811319045 / 1000 = 460003811319.045 mod then requires removing the whole number and multiplying the remainder by the original mod number. This would give 0.045 *1000 = (45) STEP2. From previous slide, (BS_CC_CHANS*N) BS_CC_CHANS = 9 Number of Paging Groups (N) = 28 (9 * 28) = (252) STEP3. {(IMSI mod 100)mod[BS_CC_CHANS*N]} = {(45) mod [252] } 45 / 252 =0.1785 mod requires removing the whole number however as there is no whole number in this case then the remainder is multiplied by 252. This would give 0.1785 * 252 = 44.982 (Round up to 45) STEP4. Result obtained in Step 3, mod 28, therefore: (45) mod 28 45 / 28 = 1.6071 mod requires removing the whole number and multiplying the remainder by the original mod number. This would give 0.6071 * 28 = 17 Therefore we conclude that IMSI 460003811319045 belongs to Paging Group 17. For More information on Paging Groups see GSM Specification 05.02.
Soc Classification level 24 © Nokia Siemens Networks
24
© 2005 Nokia
V1-Filename.ppt / 2005-02-15/ sr
MODULUS EXPLAINED •
What is MODULUS?
• If you divide 14 by 4 you get an answer of 3 plus a remainder of 2. • When using MODULUS the remainder is the important bit, the ‘whole’ number is discarded. • Example 14/4 = 3 remainder 2, discard the whole number (3) leaving the answer 2, the maths for this would be written in the form: [14] mod 2.
Soc Classification level 25 © Nokia Siemens Networks
25
© 2005 Nokia
V1-Filename.ppt / 2005-02-15/ sr
MTC _CALL FLOW •
PSR = (first paging response+ repeated paging response)*100/first paging request The following formula indicates the success rate of paging (call & SMS) 100* sum(succ_page)/sum(fail_page+succ_page) Paging (MSC to BSC ;BSSMAP) • This message is sent by MSC when it has found out the called MS is somewhere under him (= MSC recognises this is a GSM_END -call). This message contains mainly four kind of information: message type, IMSI of the called subscriber, TMSI of the called subscriber and Cell Identifier list. If TMSI -numbers are defined for use these have the priority one, for security reasons and if the network does not use TMSIs then IMSI -number is included only. The paging is sent as an UDT (Unit Data) message to the BSC.
•
•
Paging Command (BSC to BTS ;BTSM) The BSC always calculates so-called paging group. The idea of this calculation is to find out in which radio time slots the BTS can send the Paging Requests out towards the MS. Reason: in the network, there is a possibility to have at least three different kind of BCCH-TRX -radio time slot configurations and thus logical channel PCH can have at least three different kinds of location. If the BSC receives both TMSI and IMSI from the MSC, then it uses always TMSI number when sending paging further on. Paging Request (BTS to MS;PCH) The BTS sends paging on a PCH channel.
Soc Classification level 26 © Nokia Siemens Networks
Presentation / Author / Date
Major Issues that affect Paging Performance SMSC
MSC A - Interface
BSC LAPD (Abis) Interface
LA BTS 1
LA BTS 2
BTS
• •
SMSC Capacity Utilization
• • • •
A Interface( SS7) Signaling Load
• •
BCSU Processor Overload – Lower/Upper Limit Issues
• •
LAPD Load – Against the Signaling Link Used ( 16/32/64Kbps)
• •
Paging Deletion in Cells
• • • •
Cell Reselection Strategy ( HYS - Specially in LA borders)
Page Time Out
Page Time Out VLR Subscriber Capacity BHCA ( SMS & Voice)
Example of smart Network -Philippines
BSC Hardware Utilization
Paging Load ( High Page Volume) Above Capacity Limits
RACH Collisions – Overload
BTS
Air - Interface
Overshooting of Cells beyond the desired boundary Distant & Un-necessary neighbor relations Poor Coverage & Quality
MS MS
Other than Capacity Issues, PAGE TIME OUT is the main reason that is Soc Classification level to be analyzed 27 © Nokia Siemens Networks
Paging Scenario in SMART
Conclusion
• TMSI is used for both INITIAL PAGING & PAGE REPETITION • Re-page Interval ( INT3.5 Sec ) • Re-Paging Attempts is 1 ( PAGE IS REPEATED ONCE) • TMSI Re-Allocation is not done during MT Call & MT SMS
Soc Classification level 28 © Nokia Siemens Networks
Network Element Capacity & Interface Analysis - SMSC SMS Assessment – No Page Response
Clear Code 12 (NO PAGE RESPONSE) - Reasons • Paging time out • Subscriber is not reachable • No response to paging message
Possible reasons • Mobile Station Reason • MS does not give the response to the paging message • Network Availability Issues • Out of Coverage Area • During Location Update Process / LU Update Failure
Detailed analysis of Trace is in next slidex Soc Classification level 29 © Nokia Siemens Networks
Network Element Capacity & Interface Analysis - SMSC B-Subscriber is in Same BSC ( In this case BSC48)
Time Out after
MT SMS to Same Customer But Took 2 RETRY
•DX Cause 0x12 indicates NO PAGE RESPONSE ( Or Page Failure MS in same location – User A sends SMS to User B
• NO PAGE RESPONSE to
1st Attempt Including, REPAGE ( Time
Out after 7 Sec) • PAGE SUCCESFUL in 2nd RETRY , but 5.66 Sec Page Response time Indicates need to increase INT ( Re-page Interval) as MS took long time to RESPOND SMS Assessment – No Page Response
Soc Classification level 30 © Nokia Siemens Networks
Network Element Capacity & Interface Analysis - SMSC SMS Assessment – No Page Response
B-Subscriber switches between 2 BSC Report Time Length 19.07.2009 9:16:20 PM 59 19.07.2009 9:19:06 PM 59
Orig Calling No Msisdn Number 639103106764 639071071672 639103106764 639071071672
Bsc Id 48 145
Lac 12145
Cell 21704
Paging Time Dx Cause 402
0x12 0x0
Finding from Trace file : • B Subscriber switches between 2 LACs. • When the subscriber was paged 1st time, the MS may be under location update process & NO PAGE RESPONSE • Again after 2 min 46 Sec , the customer was again Paged with new LAC / Cell ID • Page was Successful, again the response time was 4.02 Sec.
Main Observations • Location update and/or Cell Reselection process took more time. Observed high setting of Cell Reselect Hyst • However its evident that the Page Response time is high as 4.02 Sec, After 1st SMS delivery attempt failed. • In SMART the Page Response Timer ( INT- Re Page Interval) is set at 3.5 Sec.
1. Need to increase Re- Page interval from 3.5 Sec 4.5 Sec 2. Review Cell Reselect Hysteresis (HYS) in Cells at LAC border. Example in later slides ( Slide 22) Soc Classification level 31 © Nokia Siemens Networks
Paging Success Rate – Snapshot 200,000
100
180,000
90
160,000
80
140,000
70
120,000
60
100,000
50
80,000
40
60,000
30
40,000
20
20,000
10
0
Paging Successful rate
Paging Attempt
Paging Attempt vs. Paging Successful rate (per LAC) MSCG11
0 10145 11145 12145 13145 14145 15145 16145 17145 10048 11048 12048 14048 BSC11145
BSC48 LAC/ BSC
Sum of PAGINGATTEMPTPERLA
Sum of PAGINGSUCCRATE
Source: VLR measurement report, paging per LAC (353/161H), 30 Jun 09 21:00
Average Paging Success Rate is less than 85% in LACs of MSCG11 Page Volume is quite high across all LACs when compared to “No of Cells in LAC” ( L Snapshot of this in the following slide. Soc Classification level 32 © Nokia Siemens Networks
LAPD ANALYSIS—Paging
Soc Classification level 33 © Nokia Siemens Networks
Presentation / Author / Date
Network Element Capacity & Interface Analysis - MSC •
A Interface Signaling Link Load ( MSC BSC)
XVSFDVG
1 0.9 0.8
Erlangs
0.7 0.6 B1148 BS145
0.5 0.4 0.3 0.2 0.1
2009-07-22
2009-07-20
2009-07-19
2009-07-18
2009-07-17
2009-07-16
2009-07-15
2009-07-14
2009-07-13
2009-07-12
2009-07-11
2009-07-10
2009-07-08
2009-07-07
2009-07-06
2009-07-05
2009-07-04
2009-07-03
2009-07-02
2009-07-01
2009-06-30
2009-06-29
2009-06-28
2009-06-27
0
Date
• All of Signaling links towards BSCs (BSC1148 and BSC145) are overload during busy hour. • The average are 0.34 Erlang since before and after new promotion. • NSN recommended Value is 0.2 Erlang. Recommended to change few VLR/PLMN Parameters to reduce the Signaling Load. Ref: Next Slide
Soc Classification level 34 © Nokia Siemens Networks
Network Element Capacity & Interface Analysis – BTS & Air Interface • Cell Overshooting, beyond the expected • Increased number of Adjacency in other LAC ( As a result of more LACs)
Example Case of Cell SH08FTPNR3 is shown in next slide Cell SH08FTPNR3 which is in LAC border , Overshoots to 3.8Km reaching the 2nd neigh This Cell has high RACH deletions and considerable Page Deletions Soc Classification level 35 © Nokia Siemens Networks
ND Report--Paging Deletion--186
Soc Classification level 36 © Nokia Siemens Networks
Presentation / Author / Date
Cell having AG Deletion—ND 202
Soc Classification level 37 © Nokia Siemens Networks
Presentation / Author / Date
BCSU LOAD—ND 184
Soc Classification level 38 © Nokia Siemens Networks
Presentation / Author / Date
Summary of Recommendations – for Improving Paging Performance NSN Recommendation to maintain good Paging Success Rate
Once Paging Success Rate is improved after implementing the recommendations in previous slide, following activities has to be done or monitored to maintain Good Paging Success Rate
• • • • • •
•
Maintain the A Interface (SS7) signaling load below 0.2 Erls ( Currently its above 0.34 Erls) Traffic Migration from MSCG11 to other MSC to reduce the Traffic Load. Remove INACTIVE BSCs ( definition) from MSCs . ( MSCG11 has only 2 BSCs where defined are 7) Monitor & maintain BCSU Load in safe limits – Less than 60% Average Load Reduce the number LACs ( Combine LAC if Page load is less) Paging Load ( LAPD limits). Minimum 32Kbps LAPD signaling is to be used. If LAPD Overload Alarm(2133) is present in few Cells, increase to 64Kbps Implement the Layering Analysis & Recommendation from NSN.
Soc Classification level 39 © Nokia Siemens Networks
Paging Optimisation • Paging is a procedure in which the PLMN attempts to reach a mobile subscriber within the location area in which the subscriber is currently registered. In a mobile-terminated call, the MSC/VLR sends a paging order to the BSCs /RNCs controlling the last location area of the mobile station. To be able to do this, the MSC/MSS has to know which BTSs belong to which location areas and by which BSCs/RNCs they are controlled. Paging can be done either with the TMSI or IMSI of the mobile station. The network operator can define if paging will be repeated in the case in which the first paging is done with TMSI or IMSI and the MS is not found. If the paging is repeated, it is done with the IMSI. • The paging retry mechanism consists of two levels. On the one hand, the Visitor Location Register (VLR) requests the paging first with the Temporary Mobile Subscriber Identity (TMSI) and when there is no response, it can request the paging with the subscriber's International Mobile Subscriber Identity (IMSI). On the other hand, the Mobile Services Switching Centre (MSC) can repeat the paging over the A/Iu interface several times with the actual TMSI or IMSI. Soc Classification level 40 © Nokia Siemens Networks
IMSI paging Successful Paging With IMSI
Soc Classification level 41 © Nokia Siemens Networks
Re-paging
Soc Classification level 42 © Nokia Siemens Networks
Unsuccessful Paging With IMSI
Power Control
Soc Classification level 43 © Nokia Siemens Networks
Power Control Motivation Reduced interference on DL/UL
Longer service time of battery Realization of power class
Activation of DL power control
powerCtrlEnabled Y,N Power control independent
Soc Classification level 44 © Nokia Siemens Networks
for DL and UL for each call
Power Control Parameter Output Power Limits Maximum MS output power
Power Values
Power class dependent range
msTxPwrMaxGSM msTxPwrMaxGSM1x00 1800/1900 TCH msTxPwrMaxCCH msTxPwrMaxCCH1x00
5..39 dBm GSM 900 TCH 0..36/32,33 dBm GSM
5..39 dBm GSM 900 CCH 0..30 dBm GSM 1800 CCH 0..32 dBm GSM 1900 CCH
Minimum MS output power minMSTxPower
Attenuations 30 dB Range
5..39 dBm GSM 900 0..36 dBm GSM 1800 dBm GSM 1900 Maximum BTS output 0..32 power (by minimum attenuation) bsTxPwrMax bsTxPwrMax1x00
0..30 dB GSM 900 0..30 dB GSM 1800/1900
Minimum MS output power (by maximum attenuation) bsTxPowerMin Soc Classification level 45 © Nokia Siemens Networks
0..30 dB
Additional attenuation for super reuse TRx
Power Control Parameters Power Change Step Sizes Desired power level can be achieved in 1 or 2 commands
Yes
No
Fixed step size
Variable step size
Fixed increment step size powerIncrStepSize
2,4,6 dB
Fixed decrement step size powerDecrStepSize
Soc Classification level 46 © Nokia Siemens Networks
2,4,6 dB
Power Control Strategy Triggering
Actual average samples
Nx samples Less than Px samples exceed threshold No power change triggered
threshold Signal level thresholds pcUpperThresholdLevelDL/UL pcLowerThresholdLevelDL/UL
-110..-47 dBm -110..-47 dBm
Signal quality thresholds pcUpperThresholdQualDL/UL pcLowerThresholdQualDL/UL Number of average samples Nx 1..32 Px 1..32 Soc Classification level 47
© Nokia Siemens Networks
0..7 0..7
Nx samples Px samples exceed threshold Power change triggered Power change step size estimation
Power Control Strategy Scenarios
Soc Classification level 48 © Nokia Siemens Networks
Exceeded threshold
Action
Reason
pcUpperThresholdLevelDL pcLowerThresholdLevelDL pcUpperThresholdLevelUL pcLowerThresholdLevelUL
BTS power decrease BTS power increase MS power decrease MS power increase
Signal level Signal level Signal level Signal level
pcUpperThresholdQualDL pcLowerThresholdQualDL pcUpperThresholdQualUL pcLowerThresholdQualUL
BTS power decrease BTS power increase MS power decrease MS power increase
Signal quality Signal quality Signal quality Signal quality
Power Increase Due to Signal Level Actual receive level RXLEV_DL/UL
pcLowerThresholdsLevelDL/UL Power control triggered UL: Power increase of MS DL: Power increase of BTS RXLEV_DL/UL > pcLowerThresholdLevelDL/UL - 2 powerIncrStepSize Yes Fixed step size
No Variable step size
PWR_INCR_STEP = powerIncrStepSize PWR_INCR_STEP = pcLowerThresholdLevelDL/UL – RXLEV_UL/DL Soc Classification level 49
© Nokia Siemens Networks
Power Control Summary Upper Level
Lower Level
Upper Quality
Power increase Power decrease Power decrease 6 dB due to quality due to level due to level or quality
Power increase due to level
No action
Power decrease due to level
Lower Quality Power increase due to level or quality
Soc Classification level 50 © Nokia Siemens Networks
Power increase due to quality
Power increase due to quality
Handover Control and Adjacencies
Soc Classification level 51 © Nokia Siemens Networks
Intra cell ho MSC
BSC
BTS
MS Measurement Report ( SACCH )
Measurement Report/Result
3
1
2 PHYSICAL CONTEXT INFORMATION
Physical Context Request Physical Context Confirmed
4 NEW RESERVATION AND ACTIVATION
Channel Activation
5
Channel Activation Ack.
6
Assignment Command (FACCH )
7
SABM ( FACCH ) Establish Indication
9
SIGNALLING ON FACCH OLD
8
UA ( FACCH )
SIGNALLING ON FACCH NEW
10 Assignment Complete ( FACCH ) DT1 ( HO Performed )
15
Soc Classification level 52 © Nokia Siemens Networks
13
Receiver Ready ( FACCH )
12 RF Channel Release RF Channel Release Ack.
Presentation / Author / Date
HO MEASUREMENTS
14
11 OLD RELEASE
INTRA BSC HO MSC
BSC
BTS 2
BTS 1
MS
Measurement Report ( SACCH ) Measurement Report/Result
3
Channel Activation Channel Activation Ack.
5
2
TCH RESERVATION AND ACTIVATION IN BTS2
4 6 8
HO Command ( FACCH )
HO Access ( FACCH )
9
Establish Indication
11
12
17
15
14
Soc Classification level 53 © Nokia Siemens Networks
Presentation / Author / Date
SIGNALLING ON FACCH IN BTS2
13
Receiver Ready ( FACCH )
RF Channel Release RF Channel Release Ack.
10
UA ( FACCH ) Handover Complete ( FACCH )
Handover Complete
7
SIGNALLING ON FACCH IN BTS1
Physical Info ( FACCH ) SABME ( FACCH )
16
HO MEASUREMENTS
Handover Command
Handover Detect
DT1 ( HO Performed )
1
18
TCH RELEASE IN BTS1
INTER BSC HO OR INTRA MSC HO MSC
DT1 CR
4
BSC1
BSC2
HO Required
BTS 1
Measurement Report/Result
3
2
Measurement Report ( SACCH HO ) 1 MEASUREMENTS AND DECISION
Channel Activation Channel Activation Ack .
CC HO_ Req.Ack HO Command
TCH RESERVATION AND ACTIVATION IN BSS2 HO Command ( FACCH )
9
HandoverDetect HO Detect
6
7 DT1 HandoverCommand HO Command
8
HO Access ( FACCH )
11
12
13
15
16
18
14
UA ( FACCH ) HandoverComplete ( FACCH )
HandoverComplete
10
Physical Info ( FACCH ) SABME ( FACCH )
Establish Indication
DT1
MS
HO_Request)
5
DT1
BTS 2
17
Receiver Ready ( FACCH )
19
HO Complete 20 DT1
21
Clear Command
22
RF Channel Release RF Channel Release Ack .
DT1
Clear Complete
RSLD
(SCCP Released)
RLC
(SCCP Released Ack)
Soc Classification level 54 © Nokia Siemens Networks
24
Presentation / Author / Date
23
DISCONNECTION AND TCH RELEASE IN BSS1
Synchronized Handover Signalling MS
NETWORK ACTIVE CALL HANDO CMD HANDO ACC HANDO ACC HANDO ACC HANDO ACC
Old Channel, Old Cell
New Channel, New Cell
HANDO COM ACTIVE CALL
Original and target cells controlled by same BCF No timing advanced information required for MS Inter cell handover from one sector to another of same BTS Soc Classification level 55 © Nokia Siemens Networks
Handover Strategy Triggering
Actual average samples
Nx samples Less than Px samples exceed threshold No handover triggered
threshold Signal interference thresholds hoThresholdsInterferenceDL/UL
-110..-47 dBm
Signal quality thresholds hoThresholdsQualDL/UL
0..7
Signal level thresholds hoThresholdLevelDL/UL hoThresholdRapidLevelUL
-110..-47 dBm -110..-47 dBm
MS speed thresholds upper/lowerSpeedLimit 2km/h) Number of average samples Nx 1..32
Soc Classification level 56 © Nokia Siemens Networks
0..255 (unit =
Nx samples Px samples exceed threshold handover triggered Target cell selection
Handover Strategy (Handover Reasons) Uplink Quality
Uplink Level
AV_RXQUAL_UL_H O AV_RXQUAL_DL_H O AV_RXLEV_UL_HO
Downlink Level
AV_RXLEV_DL_HO
MS Speed
AV_MS_SPEED
Timing Advance
AV_RANGE_HO
Downlink Quality
INTERFERENCE & QUALITY
LEVEL
THRESHOLD COMPARISON
MS SPEED
DISTANCE
RAPID FIELD DROP Adjacent Cells
AV_RXLEV_NCELL( n)
Others causes (NO TRESHOLD COMPARISON)
CHANNEL ADMINISTRATION
IMPERATIVE HO
DIRECTED RETRY
- Intelligent Underlay/Overlay (IUO) - Traffic Reason Handover (TRHO)
POWER BUDGET
- Direct Access to Desired Layer/Band (DADL/B) UMBRELLA Soc Classification level 57 © Nokia Siemens Networks
PERIODIC RX LEVEL CHECK
Handover Strategy (Standard Target Cell Ranking) Adjacent Cell Load Threshold Can be checked only for cells belonging to the same BSC as the serving one btsLoadThreshold 0..100 % Adjacent Cell Priority hoPriorityLevel
0..7
Overloaded Cell -> Reduction of Priority hoLoadFactor 0..7 Ranking (not for imperative and traffic reason handover) 1) Corrected priority a Cell b c 2) Cells with same priority -> RX level Overloaded? Priority hoLoadFactor Corrected priority Rx level
N/Y 4 2 4/2 -75
No cell overloaded A overloaded
-> priorities 4,3,3 -> cell list a,b,c -> priorities 2,3,3 -> cell list b,c,a
Soc Classification level 58 © Nokia Siemens Networks
N 3 1 3 -80
N 3 1 3 -83
Handover Strategy (Decision due to RX level) Any kind of handover (except umbrella) 1a
AV_RXLEV_NCELL(n) > rxLevMinCell(n) + Max (0, msTxPwrMax(n) – P) P depends on MS power class
Umbrella handover 1b
AV_RXLEV_NCELL(n) > hoLevelUmbrella(n)
Minimum allowed signal level for target cell rxLevMinCell hoLevelUmbrella
Soc Classification level 59 © Nokia Siemens Networks
-110..-47 dBm -110..-47 dBm
any handover (except umbrella) umbrella handover
Rx Level Handover (Example) hoThresholdLevDL /Px: 1, Nx: 1 hoMarginLevel = 3 dB
enableHandoverMarginLevQual =Y BTS output power = Maximum Adjacent cells
= -95 dBm
Level Threshold is exceeded (bad_RxLevel) LEVEL HO
RX Level
-90
evaluation • Conditions 1a and 2b: AV_RXLEV_NCELL – AV_RXLEV_DL_HO > hoMarginLevel fulfilled
RX Level
Serving cell
-90 hoThresholdLevelDL
-95
-95 Adjacent cell(n) HO
100 Soc Classification level 60 © Nokia Siemens Networks
• If no adjacent -> HO Fail
Serving cell
t1
t2
3 dB
-100
t1
t2
Suitable target cell: RxLev(n)≥ RxLev+3dB
Handover Strategy (Decision due to Power Budget) General case 2a PBGT > hoMarginPBGT(n) PBGT = (msTxPwrMax - msTxPwrMax(n)) – (AV_RXLEV_DL_HO - AV_RXLEV_NCELL(n)) (btsTxPwrMax - BTS_TXPWR) Handover due to RX level, RX quality, distance and umbrella handover 2b PBGT > hoMarginLev/Qual(n) PBGT = (AV_RXLEV_NCELL(n) - AV_RXLEV_DL_HO) (btsTxPwrMax - BTS_TXPWR)
Power budget margin to prevent repeated handovers between adjacent cells hoMarginPBGT -24..63 dB general case RX level and RX quality margins to prevent repeated handovers between adjacent cells hoMarginQual -24..24 dB handover due to signal quality Soc Classification level 61 © hoMarginLevel Nokia Siemens Networks -24..24 dB handover due to signal level
Power Budget Handover (Example) Serving Cell:
Best Adjacent Cell:
AV_RXLEV_DL_HO = -90 dBm msTxPwrMax = 33 dBm BTS_TX_PWR = 42 dBm btsTxPwrMax = 42 dBm
AV_RXLEV_NCELL(n) = -80 dBm rxLevMinCell(n) = -99 dBm msTxPwrMax(n) = 33 dBm btsTxPwrMax = 42 dBm hoMarginPBGT(n) = 6 dB
1a
AV_RXLEV_NCELL(n) > rxLevMinCell(n) + Max (0, msTxPwrMax(n) - msTxPwrMax) -80 dBm > -99 dBm + (33 dBm - 33 dBm) = -99 dBm fulfilled
2a
PBGT = (msTxPwrMax - msTxPwrMax(n)) – (AV_RXLEV_DL_HO - AV_RXLEV_NCELL(n)) (btsTxPwrMax - BTS_TXPWR) PBGT = (33dBm - 33dBm) - (-90 - (-80)) - (42dBm - 42dBm) = 10 dB > 6 dB PBGT > hoMarginPBGT(n) fulfilled
Soc Classification level 62 © Nokia Siemens Networks
Interference Handover (Parameters) Thresholds hoThresholdsInterferenceDL/UL hoThresholdsQualDL/UL
-110..-47 dBm 0..7
Intra / inter cell handover hoPreferenceOrderInterDL/UL hopping hopping enableIntraHOInterDL/UL handover
Soc Classification level 63 © Nokia Siemens Networks
INTRA
for network without frequency
INTER
for network with frequency
Y/N
required to enable intra cell
Interference Handover (Execution) AvRX level hoThresholdsInterferenceDL/UL AND AvRX quality value hoThresholdsQualDL/UL Ranking of adjacent cells enableHOMarginLevQual = Y
enableHOMarginLevQual = N
Check of adjacent cells with conditions 1a and 2b
Check of adjacent cells with conditions 1a and 2a
Suitable adjacent cell ? Yes Inter cell handover Soc Classification level 64 © Nokia Siemens Networks
No
If enabled Intra cell handover
Otherwise Handover failure
Interference Handover (Example) hoPreferenceOrderInterfDL = INTER enableHandoverMarginLevQual =Y Adjacent cells BTS output power = evaluation Maximum • Conditions 1a and 2b:
hoThresholdQualDL =4 /Px:4, Nx:6 hoThresholdInterferenceDL = -85 dBm /Px:1, Nx:1 hoMarginQual = 0 dB Threshold is BOTH the Quality and Interference exceeded (bad_RxQuality/good_RxLevel) INTERFERENCE HO
AV_RXLEV_NCELL – AV_RXLEV_DL_HO > hoMarginQual fulfilled Adjacent cell(n)
Adjacent cell(n) RX Level
RX Quality 2
Serving cell
Serving cell
3
-80
4
hoThresholdQualDL -85
• If no adjacent -> Intra HO
hoThresholdInterferenceDL
5
HO
6
t1
Soc Classification level 65 © Nokia Siemens Networks
t2
Suitable HO target cell: RxLev(n)≥ RxLev
-90
t1
t2
RX Quality Handover (Execution) Thresholds hoThresholdsQualDL/UL
0..7
AvRX quality value hoThresholdsQualDL/UL Ranking of adjacent cells enableHOMarginLevQual = Y
enableHOMarginLevQual = N
Check of adjacent cells with conditions 1a and 2b
Check of adjacent cells with conditions 1a and 2a
Suitable adjacent cell ? Yes Inter cell handover Soc Classification level 66 © Nokia Siemens Networks
No Handover failure
PARAMTERS & EFFECTS
Soc Classification level 67 © Nokia Siemens Networks
Presentation / Author / Date
RECOMMENDATION PARAMTERS – 2G Radio
Soc Classification level 68 © Nokia Siemens Networks
Summary of parameters
BTS Parameters - BLT, REO, MADR, MIDR, RE
HOC Parameters - IDR, IDN, IDP, IUN, IUP, LDR, LUR, LDW, LUW, QDW,QUW, EIH & EIC
POC Parameters - LDW, LUW, QDW, QUW, INT, LDR, LUR, LDN, LUN, UDR &
Adjacency Parameter SL to be implemented.
BSC Parameters - ITCF to be implemented.
Increase MFRMS– 4 to 5 in those few cell having Page deletion
RACH DELETION— -Lapd load increase from 32kbs to 64kbs-max load crossing the threshold limit.
Soc Classification level 69 © Nokia Siemens Networks
UUR.
BTS PARAMETERS
HOC PARAMETERS
Soc Classification level 70 © Nokia Siemens Networks
POC PARAMETERS
ADCE PARAMETERS
Soc Classification level 71 © Nokia Siemens Networks
BSC PARAMETERS
Soc Classification level 72 © Nokia Siemens Networks
Default, Specific and Sensitive Parameters 1. Default parameters •
BSC, BTS, HOC, POC, ADCE, TRX tables
Sensitive parameters • • • •
BTS table: HOP, BAR, PLMN, ACC, RXP, TLC, PMAX, DMAX, TRP, IDLE, ACT, RDIV POC table: PMAX, UDR, UUR, LDR, LUD HOC table: EPB, HPP, LDWS, LUWS, QDWS, QUWS, QDR, QDP, QDN, QUR, QUP, QUN, LDR, LDP, LDN, LUR, LUP, LUN, ADCE table: PMRG, LMRG, QMRG, MRGS
2. Specific parameters • • •
BTS table: BSC id, BCF id, SEG id, BTS id, BTS NAME, Cell id, MCC, MNC, LAC, RAC, NCC, BCC, MAL, HSN1, HSN2, MO, MS, CDEF, CDED ADCE table: BSC id, BTS id, N-LAC, N-Cell id, N-BCCH, N-NCC, N-BCC, synchronised TRX table: BSC id, BTS id, TRX id, FREQ, TSC, TSL configuration
Soc Classification level 73 © Nokia Siemens Networks
73 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
Synchronised handover • Non-synchronised Handover • MS sends access bursts (HO_ACCESS) (with varying TA) until it receives PHYSICAL_INFO
• Synchronised Handover • MS sends a few access bursts (HO_ACCESS) and then starts transmission with previous TA
• Non-synchronised handover leads to a longer communication interruption than synchronised handover (200ms vs. 100ms) • Synchronized HO should be activated between sectors of the same site. If activated on inter-site adjacencies the handover can fail
Synchronized HO
Non- Synchronized HO
Site A Soc Classification level 74 © Nokia Siemens Networks
Site B 74 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
Examples of wrong parameter set with impact on network operation/performance – call setup, qual, bands 1. No calls happening in a cell • • •
Cell Barred Non existent (LAC, Cell ID) in MSC DMAX = 0
2. Very few calls happening in a cell • •
RxLevAccesMin Wrong MNC, MCC, LAC declaration
3. Very low traffic in a cell •
msTxPwrMax = 0, bsTxPwrMax = 30
4. Bad quality in UL after rehoming 5. Few traffic in 1800 layer of a dual band 900/1800 network Soc Classification level 75 © Nokia Siemens Networks
75 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
Example 1a • No calls happening in a cell: The cell has been barred Handover
Call Setup
Soc Classification level 76 © Nokia Siemens Networks
76 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
Example 1b • No calls happening in a cell: CI different between MSC and BSC or non existent (LAC, Cell ID) in MSC
Soc Classification level 77 © Nokia Siemens Networks
77 © 2006 Nokia 08-11
MSC does not find (LAC, CI) in its 1. Network Optimization Principles / 2006database
Example 1c • No calls happening in a cell: MsMaxDistanceInCallSetup (DMAX) = 0 Despite the coverage of the cell, no calls will be established!
DMAX = 0
Soc Classification level 78 © 2006 Nokia 1. Network Optimization Principles / 2006-0878 © Nokia Siemens Networks 11
Call Setup
RxLevel = -70 dBm
Example 2b • Very few calls happening in a cell: Wrong MNC, MCC, LAC declaration in network - MNC: 01 ≠ 1 !!! (In OSS correct value)
Soc Classification level 79 © Nokia Siemens Networks
79 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
Example 3 • Very low traffic in a cell: msTxPwrMax = 0,
Parameter value bsTxPwrMax bsTxPwrMaxbsTxPwrMin = 30 minMsTxPower msTxPwrMax
Value_______Default 0 … 30 dB 0 … 30 dB 0 … 36 dBm 0 … 36 dBm
Attenuation Values (dB) BTS Max Power = BTS Power – (bsTxPwrMax = 0 dB) BTS Min Power = BTS Power – (bsTxPwrMin = 30 dB) Power Values (dBm) MS Max Power = (msTxPwrMax = 33 dB) MS Min Power = (minMsTxPower = 13 dB)
Soc Classification level 80 © Nokia Siemens Networks
80 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
0 dB 30 dB 0 dB
Example 4 • Bad quality in UL after rehoming: DiversityUsed parameter not set to yes anymore
After rehoming RDIV parameter was set to default value (No) and UL quality was affected.
Soc Classification level 81 © Nokia Siemens Networks
RDIV = Y
Uplink Diversity improves quality of signal received.
81 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
Example 5 • Few traffic in 1800 layer of a dual band 900/1800 network: Idle Mode: C2 parameters not set properly (temporaryOffset, penaltyTime)
BCCH
BCCH
slow moving mobile 1800: micro-Layer
Soc Classification level 82 © Nokia Siemens Networks
82 © 2006 Nokia 08-11
fast moving mobile 900: macro-layer
1. Network Optimization Principles / 2006-
Examples of wrong parameter set with impact on network operation/performance – upgrade 1. High drop call rate after upgrading a cell from 4 to 6 TRXs • Update MAL, no update of MAIO offset • TRXs with different power without ICE activated
Soc Classification level 83 © Nokia Siemens Networks
83 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
Examples of wrong parameter set with impact on network operation/performance – upgrade 1. High drop call rate after upgrading a cell from 4 to 6 TRXs • Update MAL, no update of MAIO offset • TRXs with different power without ICE activated
Soc Classification level 84 © Nokia Siemens Networks
84 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
Example 1a • High drop call rate after upgrading a cell from 4 to 6 TRXs: Update of the MAL with no update of the MAIO offset
Soc Classification level 85 © Nokia Siemens Networks
85 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
Example 1b • High drop call rate after upgrading a cell from 4 to 6 TRXs: TRXs with different power without ICE activated Coverage BCCH - TRX
Capacity Traffic - TRX
MS in a region covered only by Coverage-TRX, ICE not activated. Result: BTS may allocate a TSL in Capacity TRX. Call will drop.
Soc Classification level 86 © Nokia Siemens Networks
86 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
Example 1b • TRXs with different power TRX RF Units
TX RX
main div
+3dB
LNA
LNA
TX RX
main div
TX RX
main div
TX RX
main div
WBC LNA
WBC LNA
Soc Classification level 87 © Nokia Siemens Networks
87 © 2006 Nokia 08-11
Duplexer
main div
Duplexer
TX RX
Duplexer
main div
X X X
Receive Multicouplers Dual Duplex Unit & Wideband Combiners Duplexer
TX RX
Antennas
1. Network Optimization Principles / 2006-
TX/RX ant
X X X TX/RX-div ant
Examples of wrong parameter set with impact on network operation/performance – frequencies
1. Drop call rate increase after new frequency plan implementation • Double BA List activated
2. Impossibility to unlock some BTS after a RF-frequency hopping implementation
3. Impossibility to unlock some BTS after a frequency retune • NON-EDGE TRX, with GTRX = Y • TRX, with GTRX = Y, not attached to any EDAP pool 4. No handover happening after frequency retune between 2 cells from different BSCs • ADCE table has not been updated for other BSC
Soc Classification level 88 © Nokia Siemens Networks
88 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
Example 1 •
Drop call rate increase after new frequency plan implementation: In the meantime, measurementBcchAllocation has been changed to idle and MA list defined with old BCCH frequency band OLD MA List BCCH
TCH
TCH
BCCH
TCH
OLD FREQUENCY PLAN
NEW FREQUENCY PLAN
These BCCH frequencies will not be measured by old MA Li These TCH frequencies will be wrongly measured
Soc Classification level 89 © Nokia Siemens Networks
89 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
Example 4 • No handover happening after frequency retune between 2 cells from different BSCs: Frequency retune has been done with MML command. ADCE table has not been updated for incoming adjacencies TRX belonging to other BSCs BSC id
BTS id
TRX id
FREQ fA
N-Neighbour
fAB
Cell A
ADCE
Cell B
BSC id
BTS id
N-LAC
fA
Soc Classification level 90 © Nokia Siemens Networks
N-Cell id N-BCCH fAB
90 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
Examples of wrong parameter set with impact on network operation/performance – Handover 1. No handover from a cell towards all its neighbours •
PLMN permitted = No
2. High Handover failures after implementation of new adjacency plan •
SYNC = YES
3. No handover happening from an interfered cell •
hoMarginQual set to 0
4. 100% of handover failures in an adjacency relation •
Co-BSIC co-BCCH declaration
5. High number of handovers •
hoThresholdsLevUL = hoThresholdsLevDL
6. Handover not happening when DL signal level of neighbour much greater than serving cell • POC DL activated Soc Classification level 91 © Nokia Siemens Networks
91 © 2006 Nokia 08-11
1. Network Optimization Principles / 2006-
TIMERS
Soc Classification level 92 © Nokia Siemens Networks
Presentation / Author / Date
GSM TIMERS
Soc Classification level 93 © Nokia Siemens Networks
Presentation / Author / Date
RADIO RESOURCE TIMERS
Soc Classification level 94 © Nokia Siemens Networks
Presentation / Author / Date
RADIO RESOURCE TIMERS
Soc Classification level 95 © Nokia Siemens Networks
Presentation / Author / Date
TIMERS
Soc Classification level 96 © Nokia Siemens Networks
Presentation / Author / Date
IMP TIMERS –T8
Soc Classification level 97 © Nokia Siemens Networks
Presentation / Author / Date
T10
Soc Classification level 98 © Nokia Siemens Networks
Presentation / Author / Date
T3101
Soc Classification level 99 © Nokia Siemens Networks
Presentation / Author / Date
T3103
Soc Classification level 100 © Nokia Siemens Networks
Presentation / Author / Date
T3107
Soc Classification level 101 © Nokia Siemens Networks
Presentation / Author / Date
T200
Soc Classification level 102 © Nokia Siemens Networks
Presentation / Author / Date
General about T200 timer •
When the BTS transmits a DL layer-2 frame on the air (e.g. an I-frame with an embedded layer 3 message) the BTS starts the timer T200 and waits for the acknowledgement frame from the MS.
•
•
The acknowledgement frame can be another I-frame sent by the MS in the UL (if the MS has to transmit a layer-3 DTAP message anyway) as well as RECEIVE READY (RR) (if there is nothing to be transmitted on layer 3). If the acknowledgement from the MS is not received within T200 the transmission of the layer 2 frame is repeated and T200 restarted. The total number of repetitions is restricted to N200, a fixed value specified by GSM which depends on the control channel types: N200(SDCCH)=23, N200(SACCH)=5,
•
N200(FACCH/FR)=34, N200(FACCH/HR)=29
•
If T200 expires after the last layer 2 frame repetition the BTS sends an ERROR INDICATION with cause ‘T200 expired N200+1 times’ (followed by a RELEASE INDICATION) message to the BSC, which releases the associated resources.
T200s Retuning – Soc Classification level 103 © Nokia Siemens Networks
T200—Timer –BSC 94 •
•
ZEFO:
• • • • • • • • • • • • • • • •
BASE CONTROL FUNCTION BCF-0006 DATA SITE TYPE ............................ P - ULTRASITE ADMINISTRATIVE STATE ................. UNLOCKED OPERATIONAL STATE .................... WO
•
D-CHANNEL LINK SET 102 ............. OM006 WO-EX RX DIFFERENCE LIMIT ..........(RXDL).. 10 dB MASTER CLOCK BCF .............(MCBCF). -CLOCK SOURCE .................(CS).... -SYNCHRONIZATION ENABLED ......(SENA).. F SYNCHRONIZATION MODE .........(SM).... UNSYNCH FACCH LAPDM T200 .............(T200F). 0 (BCF PREDEFINED VALUES) SDCCH LAPDM T200 .............(T200S). 0 (BCF PREDEFINED VALUES) BTS UNDER THIS BCF ARE: SEG-0006 S268MRICK3 BTS-0006 SECTOR-006 S268MRICK3 ..... UNLOCKED
Soc Classification level 104 © Nokia Siemens Networks
T200-LAB TEST
Soc Classification level 105 © Nokia Siemens Networks
Presentation / Author / Date
Error Indication: T200 expired •
This sub counter is triggered if the BSC receives an ERROR INDICATION with cause 'T200 expired N200+1 times' from the BTS.
• Explanation: Whenever the BTS transmits a layer 2 frame over the radio interface, it starts the timer T200 (see associated parameter in the command SET BTS PKGBTST) and waits for the corresponding layer 2 acknowledgement from the MS. If this acknowledgement is not received as long as T200 runs, the BTS repeats the transmission of the same layer 2 frame at the maximum N200 times every time T200 expires. N200 represents a fixed number of repetitions and depends on the type of radio channel (SDCCH, FACCH (FR), FACCH (HR) etc.). If after N200 repetitions the acknowledgement still has not been received from the MS the BTS sends an ERROR INDICATION with cause 'T200 expired N200+1 times' to the BSC.
•
Up to a certain degree the occurrence of these ERROR INDICATIONs is normal in every network as it indicates transmission problems on the radio interface possibly due to bad radio conditions for individual mobiles (mobiles roaming indoor or in tunnels etc.). In fact, in a normal network the counts for the ERROR INDICATIONs with this cause make up the biggest part of all ERROR INDICATIONs counted. However, excessive occurrence of these ERR INDs point to severe radio interface problems.
Soc Classification level 106 © Nokia Siemens Networks
SDCCH Radio Failures- Vodafone Network EXAMPLE
SDCCH Radio Failures
300000
250000
200000
150000
100000
50000
0 12/1/2008
12/3/2008
12/5/2008
12/7/2008
sdcch_radio_fail
•T200s new value Implemented in test BSC •T200s new value implemented across network.
T200s Retuning – Soc Classification level 107 © Nokia Siemens Networks
12/9/2008
12/11/2008
sdcch_rf_old_ho
12/13/2008
12/15/2008
SDCCH Completion trend (BBH) – Vodafone Network EXAMPLE
100.00 98.00 96.00 94.00 92.00 90.00 88.00 86.00 84.00 82.00 80.00 78.00 MON
TUE
WED
THU
FRI
SAT
SUN
MON
1-Dec
2-Dec
3-Dec
4-Dec
5-Dec
6-Dec
7-Dec
8-Dec
TUE
WED
THU
FRI
SAT
SUN
MON
9-Dec 10-Dec 11-Dec 12-Dec 13-Dec 14-Dec 15-Dec 16-Dec
SDCCH Completion Rate (BBH) >=98%
•T200s new value Implemented in test BSC T200s Retuning
•T200s new value implemented across network.
Soc Classification level 108 © Nokia Siemens Networks
TUE
Note : No Data on 3rd, 6th Dec08 due to OSS up gradation issues.
SDCCH Enhancement after timer LAPD T200 was fine-tuned appropriately from 0ms to 780ms ( sdcch)—IDEA NETWORK(NW Wide)
SDCCH DROP IMPROVEMENT
EXAMPLE 99.00
Timer --T200 implemented
97.50
97.02 96.25 96.50
96.00 94.45
94.50
SD DROP %
93.12 93.17 93.00
92.24
92.12
91.69
91.59 91.50 90.01 90.00
90.33 89.61
88.50 87.00 85.50
DATE Soc Classification level 109 © Nokia Siemens Networks
97.39
DAY 2.NETWORK PERFORMANCE OPTIMIZATION
Soc Classification level 110 © Nokia Siemens Networks
Presentation / Author / Date
KPI with Counters
Soc Classification level 111 © Nokia Siemens Networks
Presentation / Author / Date
Soc Classification level 112 © Nokia Siemens Networks
Presentation / Author / Date
GHOST CCCH RES Counter ID: 003030
Network element name: GHOST CCCH RES
Version: 2.1
NetAct name: GHOST_CCCH_RES
Description: Number of ghost reservations on a CCCH. See also counter 003031. Updated: When a ghost reservation is detected on a CCCH. This kind of random access can be caused, for example, by white noise or co-channel interference. Note that the ghosts triggering this counter have illegal establishment cause. Ghost accesses with legal establishment cause get on SDCCH and later fail typically causing the triggering of counter 0010075.
Soc Classification level 113 © Nokia Siemens Networks
Presentation / Author / Date
RACH REJECTIONS –ND 134
Soc Classification level 114 © Nokia Siemens Networks
Presentation / Author / Date
Soc Classification level 115 © Nokia Siemens Networks
Presentation / Author / Date
KPI- Rules, SDCCH Blocking SDCCH Blocking >X%
No
ND_211 ND_130 Cngt_2 Blck_5 Blck_5b
Case closed
ND_211 Check sdcch blocking. Can sdcch capacity be added without tch blocking
SDCCH blocking is high ND_139,ND_131 ND_130, uav_22 csf_1a,csf_11 Ava_45a
no
sdcch Blocking is still high
yes Yes Check unavailability in the cells, averarage available sdcch
Yes, make corrections
Yes, add sdcch capacity Availability OK
Is dynamic sddch active
No, activate Dynamic sdcch
ND_211 c1154
yes
No, check parameter Values and make corrections ND_211 c2032 Yes, remove combined sdcch
Yes, Optimize LU area border
No
Is dynamic sdcch reaching max values in some moment
yes
Is combined sdcch used
NetAct Planner P_nbcs_cc_pm
no
Is high sdcch traffic due to Location updates. If yes, can LU area be optimized? Check also PRAU parameter, can the value be increased?
Soc Classification level 116 © Nokia Siemens Networks
No
Add TRX and add Sdcch capacity
BLOCKING—ND Report-182
Soc Classification level 117 © Nokia Siemens Networks
Presentation / Author / Date
SDCCH Blocking • SDCCH avalability
FM
– Check alarms (are TRXs & TSLs in Working State? ), check availability report and RxQuality report to verify whether there is a badly functioning TRX. Fix hardware problem. CM
• SDCCH capacity – Check actual SDCCH configuration ( e.g. Combined BCCH/SDCCH, Number of SDCCH channels). If there is insuficient SDCCH capacity and enough TCH capacity, add SDCCH TSL. Other solution e.g. PM are to add TRX, activate Dynamic SDCCH, activate FACCH Call Setup.
• SDCCH traffic – Verify traffic distribution (LU, SMS and MOC in %); – Cell is covering a region greater than planned. Verify TA statistics. May need to change DMAX, or downtilt. Soc Classification level 118 © Nokia Siemens Networks
118 08-11
© 2006 Nokia
1. Network Optimization Principles / 2006-
SDCCH blocking • SDCCH traffic due to location updates – Bad location area setting (Check MCC, MNC and LAC parameters) – Bad Location area geographical configuration. Too small LA definition will cause many LA updates. Border of LA in a busy avenue will cause many LUs in both location areas! – Low value for CellReselectHysteresis – Low value of periodicTimerLU – Verify if downtilt is needed or an increase in SDCCH capacity (air and Abis interfaces).
• SDCCH traffic due to SMS – Increase SDCCH capacity (air and Abis interfaces). Change Request!
Soc Classification level 119 © Nokia Siemens Networks
119 08-11
© 2006 Nokia
1. Network Optimization Principles / 2006-
SD BLOCK ISSUES • • • • • • • • •
Look into the BSS BBH KPI Reports and find out the list of cells where there is SD congestion See the trend for at least 3 days to ensure that it was not due to any specific reason .if appears for one day then no issue Look into the SD configuration in that cell and try to have proper dimensioning as per the demand. Look into the A-ter status and also the site fluctuations or neighbour site not taking call .escalate the same to OMC and O&M team Look into the cell in LAC boundary andhavin lot of location update signaling due to high traffic flow in LAC boundaries , correct this thro proper optimization to have minimum overlap or introducing selection offset . Look into the coverage foot print and over shooting of the site thro TA report , optimize and ensure the neighbour cells sharing the SD demand for calls in that region. Look into the A-bis signaling load if possible for a high configuration site go for 64K PCM slot for LAP-D signaling thro OMC Engineer. NSS should ensure minimum call re-attempts thro proper POI dimensioning so that the SD usages will be less. Disable Direct retry in that cell and enable Traffic reason
Soc Classification level 120 © Nokia Siemens Networks
HO.
Parameters & features – SD blocking •BSC parameter Dynamic Stand-alone Dedicated Control Channel (SDCCH) enables the configuration of SDCCH resources according to the actual SDCCH traffic situation of a cell. When the BTS temporarily needs larger SDCCH capacity than normally, the BSC configures idle traffic channel (TCH) resources for SDCCH use. When the SDCCH congestion situation is over, the extra SDCCH resources are configured back to the TCH resources
Overview of FACCH Call Set-up When an MS requests a dedicated resource by sending a random access, the BSC tries to allocate an SDCCH for the MS. If there are no SDCCHs available at that moment, the BSC tries to allocate a TCH instead of rejecting the resource request. If there are free TCHs, FACCH Call Set-up is used to assign the MS from the CCCH to the TCH instead of the SDCCH - with the immediate assignment procedure. The FACCH is used for call set-up signalling instead of the SDCCH. The TCH is used for signalling and thus no assignment procedure is needed in the radio interface. Instead, only the mode modify procedure is required to change the channel mode from signalling to, for example, speech or data.
Soc Classification level 121 © Nokia Siemens Networks
Presentation / Author / Date
Soc Classification level 122 © Nokia Siemens Networks
Presentation / Author / Date
KPI- Rules, SDCCH Drop
ND_166
SD DCR > 2% and SD DCRnum > 10
Yes
Drops due to RF Reasons
No
Drops due to Abis Reasons
No
Drops due to A-interface Reasons
No
Drops due to other Reasons
Yes
Yes
Yes
Yes
RF
Abis
A
Other
No No
Soc Classification level 123 © Nokia Siemens Networks
Case Closed
KPI- Rules, SDCCH Drop (RF) P_nbsc_RX_Statistics, Counter (q0...q7)ul and dl all levels ND_204,c1003
RF drops
Yes
Check RX Statistic,qquality level distribution. Any signal level problems = samples in bad signal leve X%
Yes
No
Repair ET lines
No Alarms Are Solved
Any improvements
Investigate alarms.If problems are not solved, activate A trace
Trace was Long enough. Not An problem was found
Investigate log Trace files. Check DX causes, see was document Call not long related DX causes in BSC enough
Any problems found. Trace was long enough
Make corrections
Soc Classification level 126 © Nokia Siemens Networks
No
Still A drops or problems
No
Yes
Case Closed
No Activate
Check ET lines in the BSC and transcoders /TCSM. Any problems
Yes
Yes
KPI- Rules, SDCCH Drop (other)
Other
Case Closed
Check all the alarms
Lapd fails
No
Yes
signalling fails or PCM fails. Check transmissio / parameters
BTS fails
No
No
User Act, bcsu, resets
Yes
Yes
Yes
TRX or BTS fails. Check that BTS/ TRX are working properly
Configuration problems, check configurations Yes
Soc Classification level 127 © Nokia Siemens Networks
Netw Act Fails
Resets or act fail channel failures
No
No
Still lots of other drops
SDCCH Drop • Ghost SDCCH – Double-Access /Multiple reservations due to co-Bsic, co-BCCH. Check and improve frequency plan. – RACH retransmissions/Multiple reservations due to bad coverage or interference and high numberOfRachRetransmissions. Lower RACH retransmission parameter value. Check and improve frequency plan and/or downtilt. – RACH retransmissions/Multiple reservations due to mass paging deleted. During festivals/ holidays/ concerts many subscribers are located at the same LAC, paging and rach load increases considerably. Consider LAC optimization, Abis expansion, paging group optimization, reduce paging repeat & rach retransmission times during busy hour. CM • Radio Fails FM – Check alarms and RxQuality report to verify whether there is a badly functioning TRX. Fix hardware problem. Check antenna line.
Soc Classification level 128 © Nokia Siemens Networks
128 08-11
© 2006 Nokia
1. Network Optimization Principles / 2006-
SDCCH Drop • Radio Fails (cont.) – Coverage. Verify TA report and planning tool. – Interference. Check Frequency Plan. Solution e.g. add sites, downtilt antennas, increase RxLevAccessMin. PM – Extended coverage of cells in location area borders. Check LU parameters and/or downtilt
• 100% ABIS Fails – Failure in BTS software (BCSU reset in BSC).
Change Request!
• 100% AIF Fails – BTS connected to other BSC or BTS is not declared in MSC.
Soc Classification level 129 © Nokia Siemens Networks
129 08-11
© 2006 Nokia
1. Network Optimization Principles / 2006-
ND REPORT__SD DROP--166
Soc Classification level 130 © Nokia Siemens Networks
Presentation / Author / Date
SDCH DROP Issues • • • •
•
•
Check the High SD drop Cells from the BSS KPI reports Look into the Drop Reason whether it is due to RF fail or any HW reason or any Signaling issue .If HW, site fluctuation or Signaling issue escalate the same to O&M/OMC team for rectification Check the proper A-bis link PCM mapping and signaling channel definition thro OMC engineer. Look into the coverage foot print of the same thro TA report and the site Data base if the cell is overshooting to longer distances optimize the same . If SD is configured in BCH carrier then look for the C/I condition for the BCH carrier looking into the reuse patterns. If SD is configured in Hopping TRX then look into the TRX performance and bad samples in that TRX and check the VSWR/Antenna /Combiner connections to the TRX .U can get a hint if you look at the assignment success ration of the cell. Look into the Quality samples in the TRX in which the SD is configured if the TRX is faulty replace the same at the earliest .
• • • • •
Try to reduce the SD usages and reduce the SD load of the cell thro proper optimization. Look into the signaling TS load on A-bis link and try to reduce the same by reconfiguration of PCM slots Check the Rx.P Value set to the cell , Make it -104 dBm . Ensure the T-200 value set to 780 mSec in all cells Correct the SD dimensioning so that there will be minimum no of dynamic SD allocations on TCH .
•
Following the procedures defined above and taking corrective action in time will result into a Quality network with SD DROP KPI maintained
Soc Classification level 131 © Nokia Siemens Networks
PATH BALANCE—208
Soc Classification level 132 © Nokia Siemens Networks
Presentation / Author / Date
Parameter and features 1. BTS : Antenna Hopping, HYS
Soc Classification level 133 © Nokia Siemens Networks
Presentation / Author / Date
Path balance --208 Case1: Jumper from TRX 4 to combiner loose (check connectors at both ends)
Case2: Jumper from Duplexer to TRX 4 (check connectors at both ends)
Case3: Check common feederline from Top of cabinet to Antenna port ( loose connector’s at either end or High VSWR problem, TRX 2&4 in this case use the same feeder) In this case, the Path imbalance (DL-UL) varies between +1.6 to -4dB which doesn’t tell much BUT DL pathloss variations between TRX’s is from 112.8 to 136dB & UL pathloss variations between TRX’s is from 111.2 to 140dB DEFINITELY A PROBLEM! Soc Classification level 134 © Nokia Siemens Networks
134
© 2005 Nokia
V1-Filename.ppt / yyyy-mm-dd / Initials
Use OSS Data to identify & pinpoint HW faults faster Sector A
Path Balance Reports help understand any imbalance between UL and DL
80.00
Whereas
70.00 60.00 50.00
TRX3 TRX4
40.00
TRX5
Eg.Pathloss comparisons between TRX’s of same sector can help identify loose cables or hardware faults, taking other TRX’s as reference case
TRX6
30.00 20.00
Eg. In Sector A:TRX 3 &4 have only 20% of DL SS samples 10dB diff gave a list of 58 cells for UP(West) attached below. Go back to 208 report for detailed analysis
Soc Classification level 136 © Nokia Siemens Networks
136
© 2005 Nokia
V1-Filename.ppt / yyyy-mm-dd / Initials
Soc Classification level 137 © Nokia Siemens Networks
Presentation / Author / Date
Soc Classification level 138 © Nokia Siemens Networks
Presentation / Author / Date
Soc Classification level 139 © Nokia Siemens Networks
Presentation / Author / Date
KPI- Rules, TCH Blocking Blck_8i Trf_1d ND_135 ND_138 ND_139 ND_211
TCH Blocking >X%
No
Case closed
TCH blocking is high
No
Planner, Optmizer ND_072
yes Yes. Check block Trend if it will drop after event
Block due to any events near ?
Check if there are some missing neighbours
Have you checked all capacity features
No
Yes
Tch Blocking is still high
No
Uav_15a ND_139
Yes Yes, make corrections
Check unavailability in the cells, also from adjacent cells Yes, add neighbours Availability OK
alarms Yes, corrections
No
No All correct
Yes,Change broken components
Check RX statistics if there are cells with broken TRX. Alarms are not always sent
NetAct,POC
No broken components
Are POC parameter correct, check also adjacent cells
Soc Classification level 140 © Nokia Siemens Networks
No, optimize dual Band network traffic handling parameters, AUCL(umbrella) Common BCCH param
Add TRX
ND_211
Are there some broken cells, check alarms, also Adjacent cells
P_nbsc_rx_statistics Counter (q0..q7)ul and dl
Make corrections
No. active HR and adjust Parameters Check also Dual Rate Timeslots and if Possible , change TCHF¨ To TCHD
Is Half Rate used and parameter optimized
yes yes
ND_211 Is dual band network optimized
TCH BLOCKING—182-ND REPORT
Soc Classification level 141 © Nokia Siemens Networks
Presentation / Author / Date
TCH blocking •
FM
TCH availability
• Check alarms (are TRXs & TSLs in Working State? ), check availability report and RxQuality report to verify whether there is a badly functioning TRX. Make Loop Tests on TRX. Fix hardware problem.
•
TCH capacity
• Bad TCH capacity dimensioning. Check number of TRXs.
Soc Classification level 142 © Nokia Siemens Networks
142 08-11
© 2006 Nokia
1. Network Optimization Principles / 2006-
CM
TCH blocking •
PM
TCH traffic
• Cell is covering a region greater than planned. Verify TA statistics. Change DMAX, or downtilt. • High traffic in some cells. Solution .eg.: Quality degradation Add Macrocells Add Microcells Add TRXs with new freq Add TRXs without new freq Activate Directed Retry Activate Queuing Activate HR Activate AMR-HR Activate DADL/B Activate AMH Activate C2 parameter Modify hoMarginPBGT
Soc Classification level 143 © Nokia Siemens Networks
143 08-11
no no no no/yes (IUO, FH) no/yes yes yes no no/yes no/yes yes yes
© 2006 Nokia
Change Request!
1. Network Optimization Principles / 2006-
Decongestion and TCH blocking Issues
•
Check the BBH KPI report and find out the cells having utilization more than 90% .
•
Check the blocked TRX report 111 and if TRX blocked found, follow up with O&M team to rectify the same as soon as possible.
•
Look into the A-ter /TRAU status of the BSC in which the congested cell is integrated
•
Look into the GPRS and SD configuration and their usages in the congested cell ,Try to reduce the same and obtain more TS for TCH.
•
Check the site location along with any site nearby to share the traffic and look into the TA report 232 for the coverage foot print of the congested cell, if possible reduce the coverage foot print and let the neighbour cell to share the traffic thro proper optimization
• •
. If decongestion is not possible with the optimization of the nearest site look into the MA list and Fractional Frequency loading(20% in multiple site areas and 30% in single site areas) if any scope for TRX addition is there go for TRX expansion and ensure the MAIO changes properly to avoid co. and adj. channel hitting.
Soc Classification level 144 © Nokia Siemens Networks
•Suggestion ,in multiple site areas first go for nearest low utilized sites optimization to share the traffic from the congested cells and after doing the optimization introduce the Traffic reason HO or Direct Retry between the neighbours . •FRL of 20% and FRU limit of 40% for HR call are allowed to avoid blocking go ahead for the same in TCH blocking cells. Suggestion : If SD block is there in cells never go for Direct Retry between the neighbours better go for Traffic reason HO with the neighbouring cells of the congested cell. •For single site areas if there is spectrum issue we should look for the customized MA list by adding some BCCH carriers carefully looking into BCCH reuse pattern in neighbouring cells and their presence close to the site •If we are unable to add TRX due to Spectrum limitation propose for a new capacity site to share the traffic .
Following the procedures defined above and taking corrective action in time will result into a Quality network with Utilization and blocking KPI maintained
Soc Classification level 145 © Nokia Siemens Networks
Parameters & features 1. 2. 3. 4. 5. 6.
BTS PARAMTER: Directed Retry , FRL & FRU , TRHO, BLT, LSEG, Queuing
Soc Classification level 146 © Nokia Siemens Networks
Presentation / Author / Date
Soc Classification level 147 © Nokia Siemens Networks
Presentation / Author / Date
ASSIGNMENT FAILURES • •
• • •
Look into the BSS BBH KPI reports for High Assignment failure cells Mostly due to HW issues like : TRX faulty, TS issues , Wrong Combiner ,Antenna connections, Wrong Air combing antenna positions , TRX cable loose, VSWR issues ,Wrong PCM mapping ,TRAU issue, Site Fluctuations, Abis link BER . Escalate to O&M and OMC team to rectify the same and follow up till got rectified RF issues : High Coverage foot print of the site , High Dense clutter ,Wrong Antenna positioning . Needs optimization and site visit IMPACT ; High assignment failures in cells contributes to Call drop , HOSR failures, SD drops in dynamic SD , Low call volume etc etc .
Soc Classification level 148 © Nokia Siemens Networks
Soc Classification level 149 © Nokia Siemens Networks
Presentation / Author / Date
KPI- Rules, TCH Drop Call Ratios Dcr_3j TCH DROPS AFTER SEIZURE TCH_RADIO_FAIL /c1013 +TCH_RF_OLD_HO /c1014 +TCH_ABIS_FAIL_CALL /c1084 +TCH_ABIS_FAIL_OLD /c1085 +TCH_A_IF_FAIL_CALL /c1087 +TCH_A_IF_FAIL_OLD /c1088 +TCH_TR_FAIL /c1029 +TCH_TR_FAIL_OLD /c1030 +TCH_LAPD_FAIL /c1046 +TCH_BTS_FAIL /c1047 +TCH_USER_ACT /c1048 +TCH_BCSU_RESET /c1049 +TCH_NETW_ACT /c1050 +TCH_ACT_FAIL_CALL /c1081 -tch_re_est_assign
Dcr_8h Dcr_5a
TCH DROPS AFTER ASSIGNMENT tch_new_call_assign /c57033 +tch_ho_assign /c57034 -tch_norm_release -tch_ho_release
/c57035 /c57036
-tch_re_est_assign
/c57032
CONVERSATION DROPS dropped_calls /c57007
/c57032 (S7)
DROPS 100 * TCH SEIZURES FOR NEW CALL tch_norm_seiz /c1009 +tch_seiz_due_sdcch_con /c1099 (S5) +msc_i_sdcch_tch /c4044 +bsc_i_sdcch_tch /c4057 +cell_sdcch_tch /c4074 -tch_succ_seiz_for_dir_acc /c1165 (S7)
-tch_re_est_assign
% CALLS
TCH ASSIGNMENTS FOR NEW CALL tch_new_call_assign /c57033
-tch_re_est_assign
/c57032
STARTED CONVERSATIONS conver_started /c57015 - msc_i_tch_tch /c4043
TCH RELEASE
/c57032 (S7)
CONVERSATION STARTED
Disconnect from MS
conn_ack to BTS
TCH SEIZED BSC allocates a TCH as a response to TCH request (Channel Activation)
TCH ASSIGNED Assignment_complete from BTS
RF CHN RELEASE Soc Classification level 150 © Nokia Siemens Networks
Rf_channel_release_ack from BTS
MS
BTS
csf_13
BSC
MSC
SDCCH signalling up to TCH seizure Authentication_Request
Authentication_Response
Authentication_Request
Authentication_Response Identification_Request
Identification_Request
Identification_Response
Identification_Response Encryption_Command
Ciphering_Mode_Command
Ciphering_Mode_Command
Ciphering_Mode_Complete
Ciphering_Mode_Complete
Setup
Setup
Call_Proceeding
Call_Proceeding
TCH DROPS AFTER SEIZURE Physical_Context_Requ Assignment_Request TCH_RADIO_FAIL /c1013 est +TCH_RF_OLD_HO /c1014 Physical_Context_Confirmation Start T9108 +TCH_ABIS_FAIL_CALL /c1084 Stop T9108 (TA info) +TCH_ABIS_FAIL_OLD /c1085 csf_14 drops after this point 57028 TCH_CALL_REQ, 57030 SERVED_TCH_CALL_REQ, 57031 SER +TCH_A_IF_FAIL_CALL /c1087 Channel_Activation +TCH_A_IF_FAIL_OLD /c1088 +TCH_TR_FAIL /c1029 Start T9103 +TCH_TR_FAIL_OLD /c1030 Channel_Activation_Ack +TCH_LAPD_FAIL /c1046 Stop T9103 Assignment_Command (SDCCH) +TCH_BTS_FAIL /c1047 Assignment_Command Start +TCH_USER_ACT /c1048 T10,T3107 +TCH_BCSU_RESET /c1049 TCH seized +TCH_NETW_ACT /c1050 +TCH_ACT_FAIL_CALL /c1081
csf_15
SDCCH signalling: MS moves on TCH, SDCCH released
Start T200
SABM (FACCH)
Stop T200
UA (FACCH)
Establish_Indication
Assignment_Complete (FACCH)
MS on TCH TCH DROPS AFTER ASSIGNMENT (Connection Failure from BTS, DX cause >= 300) spare057044 /c57044 (S10.5) drop_after_TCH_assign c1202 Soc Classification level (S11) 151 © Nokia Siemens Networks
Assignment_Complete Stop T10,T3107 Assignment_Complete
drops after this point
Dcr_8e
TCH DROP-ND REPORT—(163)
Soc Classification level 152 © Nokia Siemens Networks
Presentation / Author / Date
TCH DROP—KPI REPORT
Soc Classification level 153 © Nokia Siemens Networks
Presentation / Author / Date
KPI- Rules, TCH Drop
ND_163
DCR > X% and DCRnum > XX
Yes
No
Soc Classification level 154 © Nokia Siemens Networks
Drops due to RF Reasons
No
Drops due to Abis Reasons
No
Drops due to A-interface Reasons
No
Drops due to Transcoder Reasons
No
Drops due to other Reasons
Yes
Yes
Yes
Yes
Yes
RF
Abis
A
TR
Other
Case Closed
No
KPI- Rules, TCH Drop (RF)
RF drops >X% >X count
Yes
Check quality/level distribution. Any Bad Quality problems = Lots of samples in good signal level and bad quality
Case Closed
Check quality/level distribution. Any Bad Level problems = Lots of samples in bad signal level
No
OSS, BTS,Cell parameters
P_nbsc_HO_adj Hfr_58,hfr_59
P_nbsc_RX_Statistics Counters(ul0..ul7,dl0..dl8) ND_204
P_nbsc_RX_Statistics Counters(ul0..ul7,dl0..dl8) ND_204
Check HOs to adjacent cells, Any bad HO problems to any adjacent cells?
No
No
Check cell parameters, discrepancies?
Yes Yes Yes
Yes
Yes, change -TRX -Combiner -broken antenna
TRX is broken (sample distribution is somehow strange, for example only quality 4 samples)
Yes, Change TRX / Combiner
TRX / combiner is broken, for example only X% >X count
Drops are checked and Not real Abis problems
P_nbsc_CC_PM All counters
Case Closed
No
alarms
All Alarms are checked and abis trace is done
Yes
No
alarms
check the BTS release and the timer 3109 expired values. >BTS version 6.1 3109 expires in a BSC while waiting for the Release indication.These are seen as abis drops.These are not real drop not real abis problems
Yes
Alarms Are solved
Any improvements
Investigate alarms. If problems are not solved, activate abis trace
No
No
activate
BTS configurations, Pafile
Investigate log files.
Make corrections
Drops are happening in the release phase
Check CC table, which phase drops are happening
If not long enough, activate another trace
Trace has been measured long enough. Any problems found
Soc Classification level Yes 156 © Nokia Siemens Networks
Yes
No
Check the parameters related to abis. BSC parameters
OSS, BSC parameters Yes
Still high drops in Abis interface
KPI- Rules, TCH Drop (A) Alarms
A interface problems. Alarms are checked and A interface trace is done
A >X% >X count
No
Any improvements
Yes
Check ET lines in the BSC and transcoders /TCSM. Any problems
No
Yes
Yes Check that A parameter values are correct
Investigate alarms.If problems are not solved, activate A trace
No
Are parameters and timers checked
No
Repair ET lines
No Alarms Are Solved
MML commands P_nbsc_et_bsc P_nbsc_et_tcsm All counters
Activate
ZNRI:NA0; ZNNI:1,C;
Check that A timer values are correct
ZNMI:C; Investigate log files.
Trace was Long enough. Not An problem was found
Check if there are
Check that sccp counter values are correct
Trace errors, when MSC assign some pools was not long enough Make corrections
Any protocol error unspecified? Check bug possibility
Any problems found. Trace was long enough
Make corrections
Soc Classification level 157 © Nokia Siemens Networks
Yes
Yes
ZOCI:1;
Still A drops or problems
No
Case Closed
KPI- Rules, TCH Drop (TR) Case Closed Alarms
TR >X% >Xcount
P_nbsc_CC_PM All counters ND_523, ICTF parameter
ND_247
TR problems. Alarms are checked
Check CC table, in which phase TR drops are happening
Yes
Not In Release Phase
Check TR codec specific fails, run
Done
Check TCSM statistics Done No
No
If release phase, not real In release phase drops
Yes Investigate alarms.If problems are not solved, activate abis trace (remote TR failures
Alarms are solved
Any Improvements
No
Trace Was not Long enough
Not done
Investigate
Investigate log files.Check if Trace failures are following some was long PCM either in Abis or A and enough, No fix accordingly. Before Implementing HR in the BSC Any problem was found & cells it is must to reconfigure the A interfacelinks to support Dual Rate. Otherwise it will give rise to high call failures mainly TCH_TR_fail due to mismatch of coding between TCH in Radio & "A" interface.
Make corrections Any problems found
Soc Classification level 158 © Nokia Siemens Networks
Check that TR parameters are correct. If not, correct these
Yes
If drops are happening in some specific codec HR/FR issue investigate or is it more like individual TR problem
Not done If there some problems with TCSM investigate. ICTF, how many fails are ignored
Still TR drops or problems
KPI- Rules, TCH Drop (Other)
Other
Case Closed
Check all the alarms
Lapd fails
No
Yes
signalling fails or PCM fails. Check transmissio / parameters
BTS fails
No
No
User Act, bcsu, act fails
Yes
Yes
Yes
TRX or BTS fails. Check that BTS/ TRX are working properly
Configuration problems, check configurations Yes
Soc Classification level 159 © Nokia Siemens Networks
Netw Act Fails
Resets or act fail channel failures
No
No
Still lots of other drops
TCH Drop and Corrective action • •
Non RF drops : Check the TCH drop reason in BBH stats report. Non RF drops may have two reasons one is TR drop and other A-bis fail . If you find such issues in a site/cell then escalate to O&M team and do continuous follow up till the same got corrected. Hint : If all cells or a single cell in a site is having TR drops then check the PCM mapping and the link stability . If most of the cells /sites in a BSC is having TR drops High then escalate the same to OMC to check TRAU block . For A-bis drop, it is the link or the E1/T1 card which may have issues or any issue in the internal wiring of the BTS .
•
RF Drops : 1. If RF drop is high in cells first step is to check the Air interface clearance (BCCH reuse pattern and C/I, and the database for Hopping, Over shooting sites, neighbour missing and neighbour definitions , call dragging due to congestion in neighbour cells, border cells, VSWR issues or TRX wrong connections). Try to minimize the Overlapping to reduce the co channel hitting and quick HO attempts .
Corrective action : See the path balance reports (208) to find out the VSWR issues , see to the assignment issues in those cells, analyze the neighbour cells resource availability during BBH to take the HO request , Look into the BCCH reuse in the coverage area of the cell , check the overshooting of the cell to longer distances and try to reduce the same thro optimization, check the Hopping pool MA List and MAIO and try to have best offset to avoid co.and adj. interference.Check Fractional Frequency loading in the cell ,restrict over shooting cells( This can be checked thro the report (196) which will give you a clear indication of bad samples and confirms if all TRXs are having bad samples during BBH ) .
Soc Classification level 160 © Nokia Siemens Networks
2. Another reason for RF drop may be due to HW faults in BTS ,like TRX having poor quality TS , wrong antenna connections ,VSWR Issues in sites Corrective action : Check the assignment success rates in those cells where drop rate is high this will give you hint about the wrong connections of the devices ,Antennas . Look into the TRX Quality reports (196) where you can look into the poor quality samples per TRX if some TRX is having high poor UL/DL quality samples and others in the same cells are having good samples then the particular TRX is having some issue ,replace the same thro O&M team 3. Minimize the Hand Over attempts between cells by minimizing the overlapping of source and target cells and also setting the margins and Ping pong rejection timers . 4. Ensure the RLT and ARLT (in AMR environment ) is properly set guidelines we can set RLT 24 Frames and ARLT 36 Frames )
4. If all above you are finding ok still there is high RF drops then have a drive test and site audit to find out any external interference or Antenna issues in field ,check the VSWR thro O&M team . Following the procedures defined above and taking corrective action in time will result into a Quality network with Drop KPI maintained .
Soc Classification level 161 © Nokia Siemens Networks
Parameters & features 1. B TS parameter :Antenna Hopping,;;DMAX,;;STIRC;;BFG 2. BSC parameter:ITCF 3. MSC parameter : Call Re establishment 4. Features : AMR PPC, ROBUST AMR
Soc Classification level 162 © Nokia Siemens Networks
Presentation / Author / Date
Soc Classification level 163 © Nokia Siemens Networks
Presentation / Author / Date
KPI- Rules, HO fail HO Fail
No
Case closed
No
ND_150 ND_153 ND_157
Ho fail is high ND_150 ND_153 ND_150 ND_153 ND_157 Yes, add Capacity, TRX
Check if fails are MSC incoming or MSC outgoing fails
yes
Yes, add neighbours
Check if fails are BSC incoming or BSC outgoing fails
No
No
Check if HO fails are due to blocking HOC
NetAct Planner Optimizer
ND_150 ND_153
Yes
HOC
P_nbsc_RX_st atistics
Yes
Check if HO fails are due to missing neighbours
No, optimize parameters NetAct Planner
Check if adjacent with high fail% are working properly
Are HO parameters correct
No
Optimize MSC / BSC borders
No, optimize HO parameters NetAct Planner
Are HO parameters correct
Yes Change Frequency
Yes Optimize dominance areas, overlapping, overshooting
There are interference in some TSL’s
Any Bad interference in adjacent cells
No interfer
Yes, improve coverage Any bad signal level -new site or LNA problems -New sector -More gain antenna Yes, change These broken No components P_nbsc_rx_statistics alarms Any broken components No, all cells are OK Yes
Soc Classification level 164 © Nokia Siemens Networks
There are interference in some Frequency
P_nbsc_power _control
P_nbsc_rx_statistics
P_nbsc_rx_statistics
yes
No blocking
No
Yes, change Frequency or Tilt interferer cells
Check if fails are Intra HO Fails
No
Ho fail is still high
HO FAILURE REPORT—ND (153)
Soc Classification level 165 © Nokia Siemens Networks
Presentation / Author / Date
HANDOVER ANALYSIS
Soc Classification level 166 © Nokia Siemens Networks
Presentation / Author / Date
HO CAUSES –BSC WISE
Soc Classification level 167 © Nokia Siemens Networks
Presentation / Author / Date
HO CAUSES—CELL WISE--154
Soc Classification level 168 © Nokia Siemens Networks
Presentation / Author / Date
POOR HOSR • • • • • • • • • • •
Look into the 153 report for HOSR between source and target cells List all the neighbours where there is poor HOSR See the sites are performing well and there is no assignment failure issues and TRX HW issues Look into the BCCH and BSIC reuse pattern of the neighbours to ensure good C/I of the BCCH carrier and their definition in neighbour. Do the neighbour audit and check all the neighbours defined with proper database and LAC etc etc Define Sync neighbours between cells in a single site Check the Signaling load on A-bis and A-ter Thro Neighbour audit remove all neighbours which are not with level to retain the call and add all missing neighbours. Check the HO parameters and margins ,rescue hand over settings ,penalty timers from ZEAO and ZEHO logs to ensure less attempts and enhnace the success rate Check the whether Clock shift –DAC ( 1800-2400 ) Check Software mis match( BSC and BTS end
Soc Classification level 169 © Nokia Siemens Networks
If AMR enabled ,NSS team should ensure Proper dimensioning and A-ter link availability for codecs in TRAU . Optimize the Overlap areas between cells to have minimum HO requests in each call . Decongest the target cells to ensure TCH resource availability for a HO request . Try to introduce more Ho margin between cells inter BSC to have less attempts for Inter BSC HO . Allow RX Lev HO between single sites and minimum overlapping neighbours , with a very less HO Margin and penalty timer In an AMR scenario to minimize the quality HO ensure the Threshold level for Quality HO is set RX qual 5 or 6 . Poor HOSR Impact: Enhances TCH drop, TCH Block due to poor mobility management between sites.
Concentrating on reports and following the procedures defined above and taking corrective action in time will result into a Quality network with all KPIs maintained
Soc Classification level 170 © Nokia Siemens Networks
Paramters and features BTS Parameter : SL, PRI,PMRG,LMRG,QMRG, HO parameter : MIU,MIH,HPP;;QDR & QUR;;LDR & LUR;;LAR & LER;C/I estimation method BCF parameter : DAC drift
MSC : LAC Mismatch
AMR : IHRH & IHRF,SAL;;;n(x),p(x) change for QDRF & QURF
Soc Classification level 171 © Nokia Siemens Networks
Presentation / Author / Date
RX QUALITY 100* (sum of RxQual samples 0-5)/sum of all RxQual samples 0-7)
Soc Classification level 172 © Nokia Siemens Networks
Presentation / Author / Date
Rx Quality
DL/UL CUMULATIVE QUALITY < 5 (dlq_2/ ulq_2) Network Doctor report 196 model
Soc Classification level 173 © Nokia Siemens Networks
173 08-11
© 2006 Nokia
1. Network Optimization Principles / 2006-
Rx Quality x Rx Level
DL/UL QUALITY/LEVEL DISTRIBUTION Network Doctor report 204 model
Soc Classification level 174 © Nokia Siemens Networks
174 08-11
© 2006 Nokia
1. Network Optimization Principles / 2006-
Rx Quality x Rx Level
Good Quality
HW Problem: Bad Quality for all Rx Levels
Coverage Problem: Bad quality and Low Rx Level
High Rv Level Interference Problem: Bad quality and High Rx Level NWD report 204 model
Soc Classification level 175 © Nokia Siemens Networks
175 08-11
© 2006 Nokia
1. Network Optimization Principles / 2006-
Rx Quality x Rx Level •
Coverage Problem
• Bad Quality is due to weak signal. Check TA statistics. Add sites.
•
Interference Problem
• Internal interference. Check if interference profile follows increases in traffic profile. Check frequency plan and TA statistics. Modify frequency to verify if problem is solved. • External interference. Check if interference is independent of traffic profile. • Due to synchronisation problem. Synchronisation source set in BTS clock. Change to BSC.
•
HW Problem
• Bad quality in all RxLevel classes of ONE TRX. Check alarms to verify whether there is a badly functioning TRX. Fix hardware problem. Check antenna line. • Swap frequency. If problem persists on the same TRX, fix HW problem. • Bad quality in all RxLevel classes of TWO TRX. Verify combiner or common parts connected to both TRX.
Soc Classification level 176 © Nokia Siemens Networks
176 08-11
© 2006 Nokia
1. Network Optimization Principles / 2006-
Timing Advance High share close: Most calls are established near the BTS BTS may have indoor coverage
Low share close: BTS might be so high that area bellow it does not receive any signal They might be another dominant site
High share far: May be causing Interference and drop call rate as traffic is captured in certain regions far from the BTS.
Soc Classification level 177 © Nokia Siemens Networks
Don’t forget: 1. Traffic distribution depends on clutter types and planned coverage! 2. Repeters can change expected distribution. 177 08-11
© 2006 Nokia
1. Network Optimization Principles / 2006-
Decreasing share: Traffic is distributed mostly in regions with higher signal level NWD report 232 model
Timing Advance • High share of traffic far from the BTS
• Internal Interference Problem: High drop call rate in a certain area. Rx Quality statistics indicates an internal interference problem. With planning tool evaluate sites with the same frequency - interfering candidates. TA statistics will show traffic distance of interfering cells. Downtilt is needed.
• No neighbours in area: High drop call rate. As this cell is covering na unexpected region, there will be no close neighbours declared and HO will not happen. Downtilt is needed. Soc Classification level 178 © Nokia Siemens Networks
178 08-11
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1. Network Optimization Principles / 2006-
Soc Classification level 179 © Nokia Siemens Networks
Presentation / Author / Date
ERLANG DROP PER MIN This KPI indicate the average time between the dropped calls. Its is a division of traffic expressed in minute –Erlangs divided by the total drops and is inversely proportional to DCR.
Soc Classification level 180 © Nokia Siemens Networks
Presentation / Author / Date
Congestion & blocking SDCCH congestion time (130,216) c2033 = sdcch_cong_time Bearer channel /NSVC (240) Circuit group blocking (602,604) M058, M026: Max. 1% in BH
Blocked SDCCH seiz att (216) c1001 = sdcch_busy_att Blocking (204,204, 130,216) , csf_1a RACH load rach_3, rach_4 (188, 216)
TCH congestion time (138, 216), c2027 = tch_cong_time Blocked TCH call att (216) blck_9c Blocking (204,200,138,216) , csf_3m,csf_3i,csf_3l 0026 SIGNALLING LINK LOAD OVER THRESHOLD (>0.2erl) 500627 AIV PAGING REFUSED BIG LOAD (BSCU overload )
RACH/NOISE COLLISION RACH
BTS TRX
MS
BSC
TC
Aif
Aif
MSC
Abis link Processor unit load (184,212) avg.70% critical avg.60% max. is recommended by R&D (avg. 50% for MB)
Paging Paging buffer occupancy pagings deleted (186)
SGSN
Signalling link (SS7) traffic (524) Add link if traffic > 200mErl
Access grant
Processor unit load (605,614) avg.70% critical (avg. 50% for MB)
No direct counter but affects csf_2j (200, 204, 250)
3164 PCU PROCESSOR OVERLOAD
HLR
AG blocking (229,204, 200, 216) (blck_13)
AG blocking, GPRS (229) (blck_21)
Alarm 2720 ‘Telecom Link overload’ (030) Alarm '7746' ‘Ch congestion in BTS above defined threshold' Soc Classification level 181 © Nokia Siemens Networks
NOTE: In MSC terminology instead of term ‘blocking’ there is term ‘call congestion'
Processor unit load (606,615) avg.70% critical (avg. 50% for MB)
NOTE:The lines indicate logical source of the info, the actual genereation of the info can be in the above standing object
ALARM ANALYSIS Alarm Number
Description
7745
CHANNEL FAILURE RATE ALARM
2992
BtTS and Tc unsynchronization clear calls on a interface
2993
BTS andTC unsynchronization clear calls on abis interface
7508
RADIO TIMESLOT FAILURE IN TRX
7600
BCF FAULTY
7601
BCF OPERATION DEGRADED
7603
BTS FAULTY
7604
BTS Operation Degraded
7606
TRX FAULTY
7617
SEVERAL CALLS DROPPED DUE TO PROBLEM WITH TRANSCODER
7704
PCM FAILURE
7705
LAPD FAILURE
7715
CONTINUOUS RESTARTS OF BCF-TRX
7725
TRAFFIC CHANNEL ACTIVATION FAILURE
7738
BTS WITH NO TRANSACTIONS
7743
MEAN HOLDING TIME BELOW DEFINED THRESHOLD
2955
TRANSCODER CHANNEL FAILURE
7746
CH CONGESTION IN CELL ABOVE DEFINED THRESHOLD
7767
BCCH MISSING
7939
FORWARD POWER TOO LOW AT TX ANTENNA
8112
FREQUENCY ERROR
Soc Classification level 182 © Nokia Siemens Networks
Presentation / Author / Date
7755—Channel failure rate above defined Threshold
Soc Classification level 183 © Nokia Siemens Networks
Presentation / Author / Date
7745
Soc Classification level 184 © Nokia Siemens Networks
Presentation / Author / Date
7745
Soc Classification level 185 © Nokia Siemens Networks
Presentation / Author / Date
7745
Soc Classification level 186 © Nokia Siemens Networks
Presentation / Author / Date
7601-BCF OPERATION DEGRADED BCF Operation Degraded
BD018
BCF-0030
EQUIPM
:This alarm 7601 is generated at the BTS.
2007-07-24 04:20:45.42
** ALARM (14652) 7601 BCF OPERATION DEGRADED Difference between PCM and base station frequency reference. 02 01 07 96 00 00 1) Fault reason: Cabinet I2C bus is jammed. Solution: 1)Switch the site power Off and On. 2)Check the fan unit, the power supply unit and the TRXs. If necessary, replace the faulty units(s). 3)If the fault reappears, replace the cabinet. The units inside the cabinet can be reused in the new cabinet 2) Fault reason: Incompatible unit presence has been detected in the BTS. Solution: •Replace the high power or EDGE TRX(s) with normal type TRX(s) and reset the BCF •Or, replace the normal type FAN and power supply with high power or EDGE units. Now EDGE and high power TRXs are supported. Soc Classification level 187 © Nokia Siemens Networks
Presentation / Author / Date
7601 3) Fault reason: Difference between the PCM and BTS frequency reference.
Solution: •Check the synchronisation settings of the transmission interface.( DAC Value)DAC value Range from 1800 t0 2200. •If the settings are OK, check the transmission chain. •If the alarm stays active or reappears after the recovery actions above, reset the BCF. •If the alarm reappears after the BCF reset, replace the BTS. Note: If this Supplementary alarm appears there is Drift in clock value(DAC). That leads to HO failures 4) Fault reason: Oven oscillator control is close to its margins. The oven might be outdated. Solution: •Check the synchronisation settings of the transmission interface. •If the settings are OK, check the transmission chain. •If the alarm stays active or reappears after the recovery actions above, reset the BCF. •If the alarm reappears after the BCF reset, replace the BTS Note: If this Supplementary alarm appears there is Drift in clock value (DAC). That leads to HO failures 5) Fault reason: Flash operation failed in BOI or TRX. Solution: Replace the BOI (Base station operation Interface unit) If it is TRX change the TRX Descrpition of Supplementary information: 1-6 XX XX XX XX XX XX 1 2 3 4 5 6 1 Rack (cabinet) number 2 shelf number 3 slot 4 Type of unit 5 unit number 6 subunit number Soc Classification level 188 © Nokia Siemens Networks
Presentation / Author / Date
Soc Classification level 189 © Nokia Siemens Networks
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