Capacity CCH Load & Paging
Short Description
Capacity CCH Load & Paging...
Description
WCDMA RAN Optimisation CCH Load & Paging Optimisation
Latest version can be found: https://sharenet-ims.inside.no https://sharenet-ims.inside.nokiasiemensnetw kiasiemensnetworks.com/Overview orks.com/Overview/D495060771 /D495060771
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Introduction
• This material Covers Uplink and Downlink common channel monitoring. Paging capacity together with 24 kbps paging channels is explained. • There is Recorded SVU session available covering part of the material • Paging Load Monitoring (By Francesco Norscia)
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Content
Common Channel Load Monitoring Uplink Channel Monitoring Downlink Channel Monitoring
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CCH Load Load - Int Introd roduct uction ion
Common Channel load monitoring includes: • RACH pre-amble
• RACH-c and RACH-u load • FACH-c and FACH-u load • PCH load • SCCPCH power load
From efficient traffic scheduling point of view the CCH load of each cell needs to be measured, for example FACH-c, FACH-c, FACH-u FACH-u and PCCH transport channels channels can be multiplexed into same SCCPCH which causes some prioritization of the RLC SDUs This prioritization might lead to deletion of other transport channel’s RLC SDUs therefore it is important to measure the loads of the individual transport channels 5
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Content
Common Channel Load Monitoring Uplink Channel Monitoring Downlink Channel Monitoring
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Uplink Channel Mapping Logical Channels
CCCH
Transport Channels
RACH
DCCH
Physical Channels
PRACH
E-DPDCH E-DPCCH EDCH
DTCH
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DCH
• A single RACH transport channel is used for both, control plane signaling and user plane data. • RACH is mapped to PRACH onto PRACH physical channel which makes use of contention based access procedure i.e. there is probability that collisions occur when multiple UE attempt to make use of the PRACH.
HS-DPCCH • PRACH is separated in the preamble part and a message part. Preambles are used to DPDCH gain access to PRACH message time slot DPCCH and to ensure that the message is transmitted with sufficient uplink power.
© Nokia 2014 - CCH Load & Paging – v1.2 - Kirsi Teravainen - D495060771
Measuring the RACH Channel
Random access channel load (RACH) can be measured at the RACH preamble and transport channel levels. • WBTS measures the number of acknowledged (ACK/NACK) PRACH preambles per 20 ms RACH frame, averages over RRI period and sends the measurement to RNC. NOTE: the averaged value is rounded to closest integer, thus low PRACH load is not measured accurately •
The maximum preamble capacity is 60 preambles per RACH frame of 20 ms (4 signatures * 15 slots)
RNC_978b indicates the preamble load. •
The RACH preamble load and transport channel load are inter-connected.
•
Every positively acked preamble will correspond one sent RACH message (RACH-c of RACH-u).
•
The BTS can acknowledge in one second 60 * 1/20ms = 3000 preambles/sec.
•
BTS can decode RACH_capacity (default = 2) / 10 ms = 200 RACH messages/sec
•
Total RACH message load % = 3000 / 200 * RACH preamble load % = 15 * RACH preamble load %
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Measuring the PRACH Preamble capacity
The number of acknowledged PRACH preambles per 20ms frame during averaged over the RRI period can be calculated based on the counters below • M1000C176
SUM_RACH_ACK_PREAMBLES
• M1000C177
DENOM_RACH_ACK_PREAMBLES
RNC_978a can be used to measure PRACH message load •
The maximum preamble capacity is 60 preambles per RACH frame of 20 ms RNC_ 978b_AverageP RACHMessag eLoad
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SUM_RACH_ ACK_PREAMB LES
DENOM_RACH _ACK_PREAM BLES
© Nokia 2014 - CCH Load & Paging – v1.2 - Kirsi Teravainen - D495060771
Measuring the PRACH Preamble capacity The RACH message decoding blocking can be estimated with Erlang B equation (although this is not 100% correct for slotted system like RACH and to system with retransmission). Calculation as function of RACH preample load RNC_978b. It indicated that the level of 1.5 preambles / 20 ms will result in 5% blocking on RACH message decoding. Blocking will cause the BTS to send a negative acknowledgement and UE to apply N300 and T300 for re-transmission. A load of 1 preamble per 20 ms (1/60 = about 2% preamble load = 30% total RACH message load) can be used as triggering point for RACH_capacity increase.
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30 %
RACH message decoding blocking probability 25 %
g 20 % n i k c o l b e g a 15 % s s e m H C A R
P(Capacity=2) P(Capacity=3) P(Capacity=4)
10 %
5%
0% 1 2 4 6 7 9 1 2 4 6 7 9 1 2 4 6 7 9 1 2 4 6 7 9 1 2 4 6 7 9 0 1 2 3 4 5 7 8 9 0 1 2 4 5 6 7 8 9 1 2 3 4 5 6 8 9 0 1 2 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 3 3 3 3
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Number of RACH preamles per frame (RNC_978b)
Measuring RACH channel
• Both data (RACH-u) and signaling data (RACH-c) throughput can be measured • The counters are incremented when the MAC-c sends to the RRM an internal message (every 2 seconds, including 4 samples) with the common channel information • RACH throughput M 1000C 60 AVE_RACH_ THROUGHPUT
RACH _ throughput
M 1000C 61 RACH_DENO M_ 3
• RACH-u throughput formula provides RACH transport channel User Plane data throughput RACH-u throuhgput
M 1000C 62 AVE_RACH_ DATA_THROU GHPUT
M 1000C 63 RACH_DENO M_ 4
• RACH-c throughput formula provides RACH transport channel Control Plane data throughput RACH-c throughput
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M 1000C 60 AVE_RACH_ THROUGHPUT M 1000C 62 AVE_RACH_ DATA_THROU GHPUT
M 1000C 61 RACH_DENO M_ 3
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M 1000C 63 RACH_DENO M_ 4
Measuring the RACH Channel
The Random Access Channel capacity depends on the RACHCapacity parameter • The RACHCapacity defines the HW capacity reserved for a RACH transport channel in the BTS
• RACH Capacity is indicated as the number of decoded RACH messages in a 10 ms radio frame • Defines also the number of used PRACH preamble signatures used • Range 1,2,3,4 (messages) and default = 2
For example if the RACHCapacity = 2 (def) then it means that the BTS can decode 2 RACH messages in every 10ms radio frame and therefore the decoding capacity is 2 RACH PDUs * 45B/10ms = 9kBps = 72kbps i.e. 2 RACH TBs * 360bit/10ms = 72kbps
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Measuring the RACH Channel
Iub capacity is according to the table below, depending on the RACHCapacity parameter (1,2,3,4)
• Note the capacity impact on iub as the capacity above is required as per each cell so there is a clear impact on how many e.g. voice users 1*E1 can support in case capacity for RACH is increased 13
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Example: RACH-c and RACH-u loading
• Examples of RACH load (TP / TP_max) in high traffic cells (RACH_capacity = 2) • In extreme load the RACH throughput drops even though ack preample load is high
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Measuring the RACH Channel
• The PRACH load is dependent upon the number of UE making use of the RACH transport channel. The RACH transport channel may be used for the t ransfer of either user plane or control plane information.
• The PRACH load can be reduced by: • Increasing the RACH_capacity parameter • Evaluate whether or not there are large quantities of signaling generated by cell, URA, location area or routing area updates. If so, consider adjusting the area boundaries • Evaluate whether or not there is excessive user plane data transfer within CELL_FACH. If so, consider reducing the RLC buffer thresholds that trigger the transition to CELL_DCH • Upgrading the Node B configuration in terms of an additional carrier
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Content
Common Channel Load Monitoring Uplink Channel Monitoring Downlink Channel Monitoring
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Downlink Channel Mapping Logical Channels
Transport Channels
Physical Channels
P-CPICH
BCCH
BCH
P-CCPCH
PCCH
PCH
S-CCPCH PICH AICH P/S-SCH
CCCH FACH CTCH DCCH
DTCH 17
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HS-DSCH
E-HICH HS-PDSCH* HS-SCCH
DCH
DPDCH DPCCH
S-CCPCH Configuration 1
• • • •
This configuration limits the PCH bit rate to 8 kbps The PCH is multiplexed with the FACH-u and FACH-c The PCH always has priority SF64 is required to transfer the FACH-u and FACH-c bit rates Logical channel
Transport channel
Physical channel 18
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DTCH
FACH-u
DCCH
CCCH
FACH-c
SCCPCH 1 SF 64
© Nokia 2014 - CCH Load & Paging – v1.2 - Kirsi Teravainen - D495060771
BCCH
PCCH
PCH
24kbps Paging Channel
• Earlier versions support a PCH bitrate of 8 Kbps • Transport block size of 80 bits & 10 ms TTI • PCH bitrate of 8 kbps limits the capacity of paging messages to a single paging record, i.e. single paging record can be broadcasted per 10 ms TTI • RU20 support PCH bitrate of 8 and 24 kbps, 24kbps PCH is based upon - Transport block size of 240 bits & 10 ms TTI - 24kbps paging channel require activation of second SCCPCH channel Paging Type 1 message
maxPage = 8 3GPP allows up to 8 paging records per paging message
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S-CCPCH Configuration 2
• PCH24kbpsEnabled is configured to enabled with this configuration
Logical channel
DTCH
DCCH
CCCH
BCCH
PCCH
• Increases the PCH bit rate to 24 kbps
• The PCH is allocated its
Transport channel FACH-u
FACH-c
PCH
own S-CCPCH
• SF128 is allocated to the PCH to support the increased bit rate
Physical channel
SCCPCH 1 SF 64
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SCCPCH 2 SF 128
24 paging Channel - Impact to Code and power capacity Cch,256,14
• Channelisation code for 24 kbps PCH uses a larger section
E-AGCH
of the code tree
Cch,128,6
• HSDPA cannot use 15 HS-PDSCH codes when HSUPA 2 ms
Cch,128,5
TTI is enabled with 24 kbps PCH
E-HICH & E-RGCH
• The transmit power of the S-CCPCH is defined using the parameters:
• • • •
PtxSCCPCH1 (PCH/FACH or only FACH)
HS-SCCH Cch,16, 0
Cch,128,4
PtxSCCPCH2 (Standalone PCH)
S-CCPCH 2
PtxSCCPCH3 (S-CCPCH for SAB)
PICH
Cch,64,1
PtxSCCPCH2SF128 (Standalone PCH SF128 / 24kbps)
AICH
• The PtxSCCPCH2SF128 parameter defines the transmit
P-CCPCH
power of the S-CCPCH used to transfer the 24 kbps PCH
Cch,256,3 CPICH
• All parameters define the transmit power of the data bits (rather than the transmit power of the TFCI and Pilot bits) 21
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S-CCPCH 1
Cch,256,2 Cch,256,1 Cch,256,0
Common Channel Load - SCCPCH
SCCPCH load is used by PS in downlink channel type selection algorithm •
Average SCCPCH load is given as percentage value (defined as ratio between the SCCPCH transmission power and the CPICH power)
•
incremented when the MAC-c sends to the RRM an internal message (every 20 seconds, including 0.5s sampling period) with the common channel information
•
SCCPCH load is one criteria for switching from common channel to dedicated channel
RNC_ 979a_SCCPCHAverageLoad
M 1000C 64 AVE_SCCPC H_INC_PCH_ LOAD
M 1000C 65 SCCPCH_LO AD_DENOM_ 0
%
•
If a single S-CCPCH is configured then this KPI is applicable to that channel
•
If two S-CCPCH are configured then this KPI is applicable to the S-CCPCH encapsulating the PCH transport c hannel
Both counters are incremented every CCH Load Measurement Period •
Num is incremented by the value received in the measurement
•
Denom is incremented by the number of measurements
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SCCPCH Monitoring – FACH-u and FACH-c •
The load of different transport channels (FACH-u, FACH-c and PCH) can be monitored separately
•
FACH-u and FACH-c load can be calculated using Formulas below
•
RNC_2029b FACH-u Load Ratio provides information about the FACH transport channel User Plane data load, by dividing the FACH channel throughput by the corresponding transport channel max bit rate to get the load ratio. RNC_ 2029b_FACH u
•
100*
Sum AVE_FACH_U DATA_TP_SC CPCH Sum FACH_U_DAT A_TPUT_DEN OM_ 1* 36000
RNC_2030b FACH-c Load Ratio provides information about the FACH transport channel Control Plane data load, by dividing the FACH channel control data throughput by the corresponding transport channel max bit rate to get the load ratio.
RNC_ 2030b
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AVE_FACH_U SER _ TOT _ TPUT (AVE_FACH_ UDATA_TP_S CCPCH) 100* FACH_USER_ TOT_TPUT_D ENOM_ FACH_U_DAT A_TPUT_DEN OM_ 1 1 33600
© Nokia 2014 - CCH Load & Paging – v1.2 - Kirsi Teravainen - D495060771
Example: FACH-c and FACH-u loading
• FACH and S-CCPCH load from two high traffic cells • RACH-c and FACH-c have higher priority, also the user plane allocation is limited when RACH or FACH load reaches load threshold (default 75%)
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Paging Types and PCH Load
When the network needs to contact a certain user a Paging procedure will take place. • The paging method used depends on the UE RRC state:
- IDLE: Paging Type 1 - over PCH - LA/RA level - CN originated - Cell/URA-PCH: Paging Type 1 - over PCH - Cell/URA level - CN/RNC origin. - Cell-DCH/Cell-FACH: Paging Type 2 / over SRB / Cell level Only Paging Type 1 affects the PCH Load
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Paging Channel capacity(I)
• NSN RAN, until RU10 (RN4.0) sw release, provides an 8 kbps PCH transport channel on the S-CCPCH. • The PCH TBS is 80 bits allowing to carry a single paging record per TTI (10ms) 100 paging records per second a single cell can thus page maximum 100 UEs per second
Max PCH Throughput 8 kbps 26
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max 100 Pages/s per cell
© Nokia 2014 - CCH Load & Paging – v1.2 - Kirsi Teravainen - D495060771
Paging Channel capacity(II)
• This capacity could get exhausted due to a combination of reasons (high traffic, LAC oversize,…). In case of too high Paging Load a considerable percentage of paging messages could get lost causing a bad user experience (‘non-reachability’ of UEs due to missing pages). • It should be taken into account that S-CCPCH can be shared with the FACH-c and FACH-u but PCH always has priority. This means that a high Paging load has an impact upon FACH capacity when single S-CCPCH is configured.
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MSS/VLR counters for Paging
MSS/VLR counters for Paging attempts (originated by MSC only), successes and failures per LAC in measurement table M353. •
Available in VLR measurement report, paging per LAC (353/161H)
Counter id
Counter name
Description
M353B3C1
PAGING ATTEMPTS PER LAC
Number of initiated Pagings from the VLR to the specific LA.
M353B3C2
SUCCESSFUL PAGINGS PER LAC
Number of successf ul Pagings in the VLR in the speci fic LA
M353B3C3
PAGING ATTEMPT WITH IMSI PER LAC, SUCCESSFUL
The number of paging attempt with IMSI for successful pagings (ATT#(SUCC)) counters show how many paging requests were sent to the A and Iu interfaces (from the MSC) per LAC when the paging was successful.
M353B3C4
PAGING ATTEMPT WITH TMSI PER LAC, SUCCESSFUL
The number of paging attempt with TMSI for successful pagings (ATT#(SUCC)) counters show how many paging requests were sent to the A and Iu interfaces (from the MSC) per LAC when the paging was successful
M353B3C5
PAGING ATTEMPT WITH IMSI PER LAC, FAILED
The number of paging attempt with IMSI for failed pagings (ATT#(FAIL)) counters show how many paging requests were sent to the A and Iu interfaces (from the MSC) per LAC when the paging failed.
M353B3C6
PAGING ATTEMPT WITH TMSI PER LAC, FAILED
The number of paging attempt with TMSI for failed pagings (ATT#(FAIL)) counters show how many paging requests were sent to the A and Iu interfaces (from the MSC) per LAC when the paging failed.
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RNC KPIs for Paging attempts
• The mentioned counters can be used to monitor the number of paging messages per cell: E_ 1 _ATT_CN_OR IG M 1006 C 25 _ PAGING_TYP Paging Att empts per Cell M 1006 C 25 PAGING_TYP E_ 1 _ATT_RNC_O RIG M 1006 C 27 _ PAGING_TYP E_ 2 _ATT
• In order to count only the amount of pages sent on PCH channel the following KPI can be used (Paging Type 2 excluded): PE_ 1 _ATT_CN_OR IG M 1006 C 25 _PAGING_TY Paging Type 1 Attempts per Cell M 1006 C 26 _PAGING_TY PE_ 1 _ATT_RNC_O RIG
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RNC KPI for Paging Load The AVE_PCH_THROUHGPUT counter, divided by the denominator, gives Average PCH throughput UPDATED: When the RNC/MAC-c sends an internal message with common channel information to the Radio Resource Management in the RNC Not suitable if 24 kbps paging CH
MAC-c sends this message at 2-second intervals Average PC H Throughput
M 1000C 70 AVE PCH THROUGHPU T
M 1000C 71 PCH THROU GHPUT DENO M 0
bps
Taking into account that the PCH physical limit is 8kbps the Average PCH Throughput can be normalized to this value providing PCH Load in percentage: RNC_ 2031a_PCH Load
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100
Average PC H Throughput bps 8000
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%
Not suitable if 24 kbps paging CH
Average PCH throughput daily distribution • The average PCH Throughput approaches 7kbps several times per day • This can be assumed as a clear symptom of PCH congestion during the traffic peak hour.
RNC ≡ LAC
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PCH physical limit
Average PCH Load daily distribution • Average PCH Load equal to 80..90% at RNC≡LAC level • In a such highly congested situation a high rate of missing pages is expected and a LAC splitting needs to be planned
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VLR Paging SR vs PCH Thp: congestion • The Paging success rate starts to decrease when PCH throughput exceeds 4-4.5kbps, that is a PCH Load of 50-55% approximately and is below 90% when PCH throughput exceeds 6kbps
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VLR Paging SR vs PCH Thp: no congestion • Interesting to compare the correlation shown by a nearly unloaded RNC
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Received Page/s by CN vs PCH Load • A quasi-linear relation exists up to 45% PCH load and starts to become non-linear at 50% meaning that CN needs to send more paging (i.e. repaging) because RAN is not able to properly serve them.
M1003C36 – Received paging messages from CN (s)
• Threshold of 50% PCH Load confirmed as Rule of Thumb to trigger PCH Load optimization
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Paging Load Optimization: LAC splitting • Enabling a 2nd S-CCPCH without 24 kbps paging channel will not increase the PCH capacity (8kbps), but only FACH capacity.
• LAC splitting is needed to reduce the Paging Load • LAC split methodology is based on the number of BH MTCs: the target is to balance BH MTC on hour level Answered Pagings (CS)
M1001C56 MTC_LOW_PR IOR_SIGN_A TTS
LAC splitted
Weekend normal traffic decrease
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M1001C60 MTC_CAUSE_ UNKNOWN_AT TS M1001C32 MTC_CONV_C ALL_ATTS
Paging Load Optimization: RAN1202 (RU20) 24 kbps Paging Channel • Provides support to PCH bit rate of 24 kbps next to 8 kbps
• 24 kbps PCH is based upon a TBS of 240 bits and TTI of 10 ms • Up to 8 paging records per TTI allowed (3GPP) max 8 * (RU10) PCH Capacity
• Requires # S-CCPCH > 1 (PCH is still allocated its own S-CCPCH) • SF is decreased from 256 to 128 compared to the 8 kbps configuration in order to support the increased bitrate
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TN148 - PCH throughput increase- 24 kbps PCH 24 kbps Paging Channel feature can increase the paging channel capacity three times higher from the 8 kbps • Transport block configuration used in the PCH channel have been modified so that larger block size is used if 24 kbps PCH is enabled • The result of this change is that PCH channel throughput measured by formula PCH _ throughput
( M 1000C 70 _ AVE _ PCH _ THROUGHPUT )
Not suitable if 24 kbps paging CH
( M 1000C 71 _ PCH _ THROUGHPUT _ DENOM _ 0)
Shows higher values in RU20 than in RU10 even if the amount of paging messages would remain the same. It’s because the counter is based on measuring physical transport blocks in the Iub interface and those blocks are sent with same size even if there isn't paging messages to fill in all the blocks.
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TN148 - PCH throughput increase – 24 kbps PCH The best way to measure paging channel utilization is based on PE_ 1 _ATT_CN_OR IG M 1006 C 25 _PAGING_TY Paging Type 1 Attempts per Cell PE_ 1 _ATT_RNC_O RIG M 1006 C 26 _PAGING_TY
These counters tell the amount of paging messages successfully scheduled in the Iub interface -8 kbps PCH can transfer about 100 paging messages per second, -24 kbps channel capacity is about 400...500 messages per second (depends on paging type). When the amount of paging messages exceeds 50% of t he nominal capacity, its good time to start thinking about actions to reduce paging channel load to avoid degradation in paging success rate. • 50 msg/s for 8 kbps PCH • 250 msg/s for 24 kbps PCH
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Example: Updating 8 kbps to 24 kbps PCH
Configuration changes • 08.11.2010 - 24 kbps PCH, 2nd SCCPCH • 09.11.2010 - Inactivity parameter changes (this is not releated to 24 kbps PCH changes)
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Object Parameter Name
Abbreviated Name
Actual value
new value
RNC
Low utilization time to trigger of the MAC-d flow
MACdflowutilTimetoTrigger
2 sec
0 sec *
RNC
Window size of the MAC-d flow throughput measurement
MACdflowthroughputAveWin
3 sec
2 sec
RNC
Low throughput time to trigger of the E-DCH MAC-d flow
EDCHMACdFlowThroughputTimetoTrigger
5 sec
1 sec
RNC
Window size of E-DCH MAC-d flow throughput measurement
EDCHMACdFlowThroughputAveWin
3 sec
2 sec
RNC
Uplink traffic volume measurement low threshold
TrafVolThresholdULLow
128 bytes
256 bytes
RNC
UL/DL activation timer
UL_DL_activation_timer
2 sec
1 sec
RNC
Inactivity timer for uplink 8kbps DCH
InactivityTimerUplinkDCH8
5 sec
2 sec
RNC
Inactivity timer for uplink 16kbps DCH
InactivityTimerUplinkDCH16
5 sec
2 sec
RNC
Inactivity timer for uplink 32kbps DCH
InactivityTimerUplinkDCH32
5 sec
2 sec
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PCH Utilisation, TN148 method • Number of sites per load level with 8 kbps and 24 kbps PCH, using TN148 method
=(PAGING_TYPE_1_ATT_CN_ORIG + PAGING_TYPE_1_ATT_RNC_ORIG)/3600/4 • 8 kpbs PCH -> 100 pages/s • 24 kbps PCH -> 400-500 pages/s =(PAGING_TYPE_1_ATT_CN_ORIG + PAGING_TYPE_1_ATT_RNC_ORIG)/3600
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PCH utilisation, Nov 5, 8 kbps PCH
Results using old method with 8 kbps PCH PCH utilisation Nov 5 1400
120 %
1200
100 %
1000
t
80 %
n u o c
800
r
%
u o h ll c W
40 % 400
20 %
200
0
0% 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73
Utilisation [%]
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D C
600
e
43
F
60 %
© Nokia 2014 - CCH Load & Paging – v1.2 - Kirsi Teravainen - D495060771
PCH Utilisation Nov 5, 8 kbps PCH - TN148 method • Results using TN148 method with 8 kbps PCH Similar kind of results with both method when 8 kbps PCH in use
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PCH loading and FACH throughput
One SCCPCH and 8 kbps PCH. •When SCCPCH is heavily loaded there is risk that FACH messages are delayed or even dropped. This may cause reconfiguration process failures and PS RABs drops.
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Example: Average Paging load RNC15 Paging capacity is increased from 100 paging/s to 450-500 paging/s 2nd SCCPCH and 24 kbps PCH activated
Paging Load (Paging per second) RNC15 500.0 450.0 400.0 350.0 300.0 250.0 200.0 150.0 100.0 50.0 0.0
PPS
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Max PPS Capacity
Preventive action Target
Paging utalization calculated as Pagings per second according to the formula below (M1006C25 PAGING_TYPE_1_ATT_CN_ORIG + M1006C26 PAGING_TYPE_1_ATT_RNC_ORIG)/3600 © Nokia 2014 - CCH Load & Paging – v1.2 - Kirsi Teravainen - D495060771
Example: Paging success rate from LAC350 (MSS counters)
2nd SCCPCH and 24 kbps PCH activated
Paging Succesrate per LAC 100
Improved paging success rate after feature activation
99 98 97 96 95
LAC 350
94 93 92 91 90 9 2 / 1 1 / 0 1 0 2
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0 3 / 1 1 / 0 1 0 2
1 0 / 2 1 / 0 1 0 2
2 0 / 2 1 / 0 1 0 2
3 0 / 2 1 / 0 1 0 2
4 0 / 2 1 / 0 1 0 2
5 0 / 2 1 / 0 1 0 2
6 0 / 2 1 / 0 1 0 2
7 0 / 2 1 / 0 1 0 2
8 0 / 2 1 / 0 1 0 2
9 0 / 2 1 / 0 1 0 2
0 1 / 2 1 / 0 1 0 2
1 1 / 2 1 / 0 1 0 2
© Nokia 2014 - CCH Load & Paging – v1.2 - Kirsi Teravainen - D495060771
2 1 / 2 1 / 0 1 0 2
3 1 / 2 1 / 0 1 0 2
4 1 / 2 1 / 0 1 0 2
5 1 / 2 1 / 0 1 0 2
6 1 / 2 1 / 0 1 0 2
7 1 / 2 1 / 0 1 0 2
8 1 / 2 1 / 0 1 0 2
9 1 / 2 1 / 0 1 0 2
Example: Paging msg per paging from VLR LAC350 2nd SCCPCH and 24 kbps PCH activated
Pag msg per pag from VLR (%) 180.00 160.00 140.00 120.00 100.00 80.00 60.00 40.00 20.00 0.00
Pag msg per pag from VLR MSC_514A
After feature activation less paging messages per paging is send. Hence paging load has decreased and paging capacity increased while paging success rate is improved 48
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Example: PS NRT active failures RNC15, 13 and 18 2nd SCCPCH and 24 kbps PCH activated in RNC15
2nd SCCPCH and 24 kbps PCH activated in RNC13 and 18
RAB active fail PS background RADIO 18000 16000 14000 12000 10000 8000 6000 4000 2000 0 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1 2 3 2 2 2 2 2 3 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 0 0 0 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
RNC-13
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RNC-15
© Nokia 2014 - CCH Load & Paging – v1.2 - Kirsi Teravainen - D495060771
RNC-18
Conclusion
• Higher Paging Channel TBS reduces PCH load from radio interface point of view. It also reduces internal processing load of RNC because less internal messages are needed to serve the same amount of users. • So less DMPG processing capacity is needed for PCH and it can be used for other purposes. Both PCH and RNC processing load are important areas of RNC performance.
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Paging drop counters – RU30 new RNC Counters to measure the amount of dropped paging records in L2. • Previously this information was available only in DMPG computer logs Counter id
Counter Name
Updated
M1006C251
PAGING DROP LOW PRIORITY
When the L2 entity of RCN drops low priority paging message due to congestion
M1006C252
PAGING DROP HIGH PRIORITY When the L2 entity of RNC drops high priority paging message due the congestion
L3 detects first-time and repeated paging’s for Idle and Connected mode UEs and attaches the information into paging messages sent to the L2. The first-time paging's are marked as having “high priority” and repeated paging’s as having “low priority”. L2 prioritises paging records marked as having “high priority” over the ones marked with “low priority” in its scheduling decisions
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Paging drop counters Paging for UE’s in IDLE state
When RNC receives paging message RANAP: Paging from the CN, counter: M1003C36 REC_PAG_MSG is incremented
BTS
UE
RNC
CN
UE In Idle mode RANAP: PAGING
1
PICH
M1006C251 PAGING_DROP_LOW_PRIORITY : The number of low priority paging r ecords dropped in L2 scheduling. Counter is updater when the L2 entity of RNC drops low priority paging message due to congestion. M1006C252 PAGING_DROP_HIGH_PRIORITY : The number of high priority paging records dropped in L2 scheduling. Counter is updated when the L2 entity of RNC drops high priority paging message due to congestion.
(FP/AAL2/PCCH/PCH/S-CCPCH) : PAGING TYPE 1 RRC connection establishment Paging response
CN (RANAP: PAGING Message received from CN = UE in idle mode) originated paging amount: When RNC sends Paging Type 1 through cells, counter M1006C25 PAGING_TYPE_1_ATT_CN_ORIG
If RNC cannot process the paging messages and forward those to the UE due to high ICSU load, counter M1003C47 DEL_PAG_MSG_ICSU_OVERLOAD is incremented
Counter is updated when the RNC L2 entity has successfully scheduled PAGING TYPE 1 message for sending to the BTS and the paging procedure is triggered by the CN.
If RNC cannot process the paging messages and forward those to the UE due to high RRMU load, counter M1003C48 DEL_PAG_MSG_RRMU_OVERLOAD is incremented
Paging messages dropped due to overload are not included.
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Paging drop counters - RU30 new
Upon receiving of the paging message from Core Network, L3 determines priority of the message •
The idea is that first time paging and paging messages related to system information update would be given high priority and repetition of an earlier received paging message would be set as low priority • Prioritisation will be done for both Idle and Connected mode UE related pagings • L3 passes the paging message to the cell-specific MAC-c entity
• The message includes information of the priority of the paging • Based on this, the message is placed to the corresponding paging queue to be scheduled at the appropriate time • MAC-c schedules the paging messages so that the high priority queue is prioritised over the low priority queue whenever possible • Paging messages that could not be scheduled on time are discarded 53
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Increase the Iub reservation for RACH, reduce the FACH timer, Reduce the unnecessary registrations and inter-rat cell reselection, reduce the RACH-u load (lower TrafVolThresholdULow)
Common Channel load Monitoring
Increase the RACH capacity (FACH throughput limited by RACH capacity), Reduce the unnecessary registrations and inter-rat cell reselection and reduce the FACH timer, reduce FACH-u load ( lower TrafVolThresholdDLow), Separate SCCPCH for FACHs and PCH
Calculate CCH Load i.e. FACH-c + FACH-u, PCH, RACH-c + RACH-u per Cell
Yes
RACH throughput >10kbps
Yes
Increase the RACH reservation for Iub / increase the RACHcapacity No
No FACH throughput >15kbps
Yes
No PCH throughput >5kbps
Yes
No Calculate the #pages per LAC, >65/s
Yes
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#RL setups/s limiting factor
© Nokia 2014 - CCH Load & Paging – v1.2 - Kirsi Teravainen - D495060771
Reduce the Common Channel Setup usage
Separate SCCPCHs for FACHs and PCH Activate cell_PCH/URA_PCH
No
Calculate the #pages per LAC, >65/s
Yes Activate 24kps paging channel, cell_PCH/URA_PCH and
Paging Parameter Recommendations – 3G Implicit Detach (VLR) = 8h
Parameter Name (Cell level)
CS_T3212 = 40dh (decihours) = 240min = 4hours TMSI page repetition in voice call = Used Paging Attempts (AT) = 0 or 1 Repaging Interval (INT) = 3.5 s or 4.5s
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N300
3
2
T300
2000ms
2000ms (10)
Parameter Name (RNC level)
Current
Recommended Value
WaitTimeRRCconversational
3
2
WaitTimeRRCstreaming
3
2
WaitTimeRRCinteractive
5
8
5
8
WaitTimeRRCsubscribed
3
3
WaitTimeRRCemergency
1
1
WaitTimeRRCinterRATreselection
3
3
IuCS DRX cycle length = 640 ms
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Recommended Value
WaitTimeRRCbackground
UTRAN DRX cycle length = 320 ms
IuPS2 DRX cycle length = 640 ms
Def/Current
WaitTimeRRCregistration
5
5
WaitTimeRRChighPrioritySignalling
1
2
WaitTimeRRClowPrioritySignalling
5
2
WaitTimeRRCunknown
1
2
WaitTimeRRCother
0
2
© Nokia 2014 - CCH Load & Paging – v1.2 - Kirsi Teravainen - D495060771
Paging Parameter Recommendations – 3G Voice call SMS Initial Page
1st Re-Page
2nd Re-Page
No Paging Response
3rd Re-Page
VLR sends to RNC & RNC sends to UE No Paging Response
Paging interval4. 5s
1st Re-Page
Initial Page
SMS
UE listens pages and establishes RRC
Two pages received from RNC
RRC Connection Request Paging Response Wait Time 2s Initial Page
Wait Time 2s
1st Re-Page
2nd Re-Page
3rd Re-Page Four pages received from RNC
Voice
UE listens pages and establishes RRC
RRC Connection Request Paging Response W ait Time 2s
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W ait Time 2s
© Nokia 2014 - CCH Load & Paging – v1.2 - Kirsi Teravainen - D495060771
W ait Tim e 2s
W ait Time 2s
Paging - Core Network Parameters
AT (MSS)
Use of TMSI (VLR)
Page Repetition (VLR)
Result
0
Yes
Yes
TMSI+IMSI
0
Yes
No
TMSI
1
Yes
Yes
TMSI+TMSI+IMSI+IMSI
2
Yes
Yes
TMSI+TMSI+TMSI+IMSI+IMSI+IMSI
2
Yes
No
TMSI+TMSI+TMSI
2
No
Yes
IMSI+IMSI+IMSI
2
No
No
IMSI+IMSI+IMSI
• Search procedure is performed only if MS location is not found
- Search is always an IMSI page which will be repeated SCOUNT times with SINTER intervals
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Exercises
• Does the PCH capacity increase if second S-CCPCH is activated without 24kbps paging channel ? • List main Paging optimisation methods ?
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