Basic WiMAX Network Optimization Things

Problem-1 High Noise + Interference (NI) in UL

We need to observer the apNiAvgCol1 to apNiAvgCol7 to measure the NI on Column basis.

The statistics provide average UL NI on a per column basis (each column is 3 consecutive UL symbols)

during the statistics collection interval. Providing those statistics for each column in the UL subframe

provides clues to abnormal system behavior. Those values should be quite similar to each other and the

variance over multiple statistics collection interval should be small. The values should also be within a

reasonable range for the anticipated interference. The range varies by the deployment environment and

there is no recommended value that works for all deployments.

Solution: What to Do

Scenario 1

If in the same statistics collection interval the lower ordered (earlier in time) columns have high NI and

the other columns do not, then recommendation is to check the duty cycle (DL/UL TDD ratio) of

neighbor carriers, both on this AP and neighbor APs. A mismatch in the duty cycle causes one carrier's

DL traffic to interfere with another's UL traffic.

Scenerio-2

If the overall average seems too high, then there is an external device causing the interference and this

interferer must be found. Could be someone infringing on the owned spectrum, could be a rogue mobile

trying to cause extra interference, or could be a faulty Mobile/CPE that is leaking power into unused

carriers.

Problem 2- Increased MSS Deregistration

Increased MSS deregistration can be due to following factors

Interference

RF Coverage

Configurations

Normal MSS deregistration (due to MSS power shutdowns)

The increased MSS Deregistration is marked by the following Attribute

Statistic = apDregLostMss, High apDregLostMss means high number of MSS Deregistration

CASE -1: Interference

First Problem.

CASE-2 : RF Coverage

The system needs to support analysis of poor RF coverage through the collection and reporting of RF

quality measures. These concern uplink and downlink qualities between the AP and MSS. Specific

measures would include CINR, RSSI, Coding Rates, and RF quality of neighbor sites. MSS data may be

used to assist with poor RF coverage identification

Statistics: apInitialRangingReq, apInitialRangingCorr, apPeriodicRangingReq,

apPeriodicRangingCorr, apInitNetEntAtt, apUsersActSlp

The MSS performs CDMA initial ranging to get access to the network during the network entry

procedure. The MSS power and timing might need adjustment/corrected by the serving BS. When the

BS receives CDMA initial ranging code, it checks if power and/or timing adjustments/corrections are

needed. If needed, the BS replies with RNG-RSP with status = Continue. The MSS makes the required

corrections and tries CDMA initial ranging again. If only minor or no adjustments/corrections are

needed, the BS replies with RNG-RSP with status = Success.

The percentage of Initial Ranging corrections is calculated as:

Equation 27

% Initial Ranging Corrections = (apInitialRangingCorr/apInitialRangingReq)*100%

The average Initial Ranging attempts per Network Entry is calculated as:

Equation 28

Average Initial Ranging Attempts = apInitialRangingReq/apInitNetEntAtt

The MSS performs CDMA periodic ranging in the active state on expiry of its internal T4

timer. However; the T4 timer is reset after an UL allocation, so regular UL allocations may

prevent periodic ranging. The procedure for power and/or timing adjustment is the same

procedure used in initial ranging except the periodic ranging CDMA codes are used

instead of the initial ranging CDMA codes.

The percentage of Periodic Ranging corrections is calculated as:

Equation 29

% Periodic Ranging Corrections = (apPeriodicRangingCorr/apPeriodicRangingReq)*100%

The average Periodic Ranging attempts per user is calculated as:

Equation 30

Average Periodic Ranging Attempts = apPeriodicRangingReq/apUsersActSlp

1- Excessive ARQ and/or HARQ failure percentages for all retransmissions.

Excessive retransmissions (ARQ or HARQ) are also indicative of poor RF coverage.

Increased trends in retransmissions may indicate that coverage needs to be adjusted.

Statistics: apArqBlockTransUl, apArqBlockFailUl, apArqBlockTransDl, apArqBlockFailDl,

apArqHybridTransDl, apArqHybridDlFail, apArqHybridTransUl,apArqHybridUlFail

ARQ Equations

ARQ Uplink Failure Rate = apArqBlockFailUl /apArqBlockTransUl

ARQ Downlink Failure Rate = apArqBlockFailDl / apArqBlockTransDl

HARQ Equations

HARQ Uplink Failure Rate = apArqHybridUlFail / apArqHybridTransUl

HARQ Downlink Failure Rate = apArqHybridDlFail / apArqHybridTransDl

HARQ Downlink Retransmission Rate = (ApTxDivHarqDlT4S2TxBASEDIV +ApTxDivHarqDlT4S2TxMIMOA

+ ApTxDivHarqDlT4S2TxMIMOB + ApTxDivHarqDlT4S2TxTxAAEBF + ApTxDivHarqDlT4S3TxBASEDIV

+ApTxDivHarqDlT4S3TxMIMOA +ApTxDivHarqDlT4S3TxMIMOB +ApTxDivHarqDlT4S3TxTxAAEBF +

ApTxDivHarqDlT4S4TxBASEDIV +ApTxDivHarqDlT4S4TxMIMOA + ApTxDivHarqDlT4S4TxMIMOB

+ApTxDivHarqDlT4S4TxTxAAEBF) / (ApTxDivHarqDlTRGT4TxBASEDIV +ApTxDivHarqDlTRGT4TxMIMOA +

ApTxDivHarqDlTRGT4TxMIMOB +ApTxDivHarqDlTRGT4TxTxAAEBF)

HARQ Uplink Retransmission Rate = (apTxDivHarqUlReTxMrc + apTxDivHarqUlReTxSdma) /

(apTxDivHarqUlTxMrc + apTxDivHarqUlFailedTxMrc + apTxDivHarqUlTxSdma +

apTxDivHarqUlFailedTxSdma)

CASE -3 Configurations

Parameter tuning for RF health may be required (DL MCS tables, UL CINR

targets, ARQ block size, timer values, etc)

Problem:3 Carrier Performance degradation due to How to identify UL RF coverage /quality

Low UL signal quality is indicated by low UL CINR and directly impacts carrier throughput and

performance. Reporting UL CINR metrics will help the operator identify coverage and throughput

impacting issues. The UL CINR is calculated as C (normalized per subcarrier at QPSK 1/2) + MS headroom

(normalized per subcarrier at QPSK 1/2) -NI.

The system shall report UL CINR in a histogram with 3dB granuality. The first bucket of the histogram is a

placeholder for all negative UL CINR, the last bucket is a placeholder of all UL CINR greater than 36 dB.

Number of power control corrections correlated with number of UL bandwidth allocations

can be used to infer RF coverage issues. A high percentage of power control corrections

compared to UL bandwidth allocations is an indication of coverage issues.

Statistics: apUlCinr01 to apUlCinr14, apPwrCntrlCorr, apUlAlloc, apNiAvgCol1 to apNiAvgCol7

CASES:

CASE1:

If UL CINR statistics (apUlCinr01 to apUlCinr14), over consecutive statistics collection intervals, shows

high occurrences of low UL CINR, this is an indication of coverage issue. Drive test the carrier to find the

source of low/bad coverage.

CASE 2:

• If there are low occurrences of high UL CINR over consecutive statistics collection interval and carrier

throughput is low this is an indication of coverage issues and the operator is encouraged to conduct

extensive RF environment analysis to get to the root of the issue.

CASE 3:

• Compare UL CINR with the results expected by the operator coverage tool, if the margin of difference

is high then RF investigation should be conducted to root cause the difference. The result of the

investigation could be correcting the operator coverage tool or identifying an RF issue and correcting it.

CASE 4:

• The UL CINR histogram can be used to predict theoretical UL carrier throughput. This theoretical

throughput can then be compared with the actual reported UL carrier throughput. If the actual

throughput is much lower than the predicted, configuration parameters like wmanIfBsNormalizedCN2.

CNIR Measures/KPIs

Uplink Ratio of CINR <= 36 dB

(apUlCinr01 + apUlCinr02 + apUlCinr03 + apUlCinr04 + apUlCinr05 + apUlCinr06 + apUlCinr07 +

apUlCinr08 + apUlCinr09 + apUlCinr10 + apUlCinr11 + apUlCinr12 + apUlCinr13) /


apUlCinr08 + apUlCinr09 + apUlCinr10 + apUlCinr11 + apUlCinr12 + apUlCinr13 + apUlCinr14)

Count of Uplink CINR Ratio > 5%

Description: The formula counts the instances of carrier-to-interference-and-noise ratio greater than

5%.


apUlCinr08 + apUlCinr09 + apUlCinr10 + apUlCinr11 + apUlCinr12 + apUlCinr13) / (apUlCinr01 +

apUlCinr02 + apUlCinr03 + apUlCinr04 + apUlCinr05 + apUlCinr06 + apUlCinr07 + apUlCinr08 +

apUlCinr09 + apUlCinr10 + apUlCinr11 + apUlCinr12 + apUlCinr13 + apUlCinr14)

Distribution of Uplink CINR

apUlCinr01, apUlCinr02, apUlCinr03, apUlCinr04, apUlCinr05, apUlCinr06, apUlCinr07, apUlCinr08,

apUlCinr09, apUlCinr10, apUlCinr11, apUlCinr12, apUlCinr13, apUlCinr14

Capacity Planning

Problem 4: Increased or excessive admission control failures

CASE 1 : The total number of MSSs concurrently in the active and sleep modes reached

Statistics: apUsersActSlp, apUserActSleepPeak

The statistics: apUsersActSlp, and apUserActSleepPeak should be analyzed to determine if the cause of

the admission control failures is due to user population

Corrective Action:

This problem scenario may be addressed by the following solutions:

• If the carrier is operating in a trunked modem configuration, move to a nontrunked modem

configuration, such that more users can be accommodated in a given carrier.

• If the carrier is already operating in a non-trunked modem configuration, add APs to support the

additional user demand.

If the number of modem resources are not exceeded, the number of transport

CIDs utilized within the carrier should be analyzed:

CASE 2: The maximum number of utilized Transport CIDs is reached

Corrective Action:

apFlowNotAdmMem, apTransportCids, apTransportCidsThresh, apTransportCidsPeak

apTransportCidsPeak should be analyzed to determine the if the cause of the admission control failures

is due to Transport CID utilization. This problem scenario may be addressed by the following solutions:

• Modify the AP configuration parameters that limits the maximum number of Transport CIDs allowed

per MSS to a smaller value

• If the carrier is operating in a trunked modem configuration, move to a nontrunked modem

configuration, such that more Transport CIDs can be accommodated in a given carrier.

• If the carrier is already operating in a non-trunked modem configuration, add APs to support the

additional Transport CID demand. If the number of modem resources is not exceeded, the reserved RF

utilization should be analyzed:

CASE 3: Available downlink or uplink RF bandwidth reserved by existing Service Flows is

causing denial of new or modifications to existing Service Flow requests

Statistics: apFlowNotAdmAi, apFlowNotChgdAi, apDlRsrvPuscSlotsCbrCir, apDlAvgMcsCbrCir,

apDlCbrCirBwThresh, apUlRsrvPuscSlotsCbrCir, apUlAvg-

McsCbrCir, apUlCbrCirBwThresh

The statistics apFlowNotAdmAi and apFlowNotChgdAi indicate the number of

times the carrier received a request to set up a new or modify an existing service

flow, but couldn’t due to reserved air interface bandwidth. If the apFlowNotAdmAi

or apFlowNotChgdAi statistic trends consistently contain significant values

(a value which is deemed too large given the Service Provider’s planning guidelines),

the statistics: apDlRsrvPuscSlotsCbrCir, apDlAvgMcsCbrCir, apDl-

CbrCirBwThresh, apUlRsrvPuscSlotsCbrCir, apUlAvgMcsCbrCir, and

apUlCbrCirBwThresh should be analyzed to determine if the cause of the

admission control failures is due to air interface bandwidth.

Downlink RF bandwidth projected by CBR and CIR flows

A lack of sufficient bandwidth for CBR and CIR flows in the Downlink direction

will be indicated by several pegs of the apDlCbrCirBwThresh statistic.

Average Downlink RF Bandwidth projected for CBR and CIR Flows is given by

the following equation:

Equation 1

Average Downlink RF bandwidth projected (Mbps) =

(apDlRsrvPuscSlotsCbrCir * apDlAvgMcsCbrCir) / (1M * Stats Collection

Period)

UplinkRF bandwidth projected by CBR and CIR flows

Likewise, a lack of sufficient bandwidth for CBR and CIR flows in the Uplink

direction will be indicated by several pegs of the apUlCbrCirBwThresh statistic.

Average Uplink RF Bandwidth projected for CBR and CIR Flows is given by

the following equation:

Equation 2

Average Uplink RF bandwidth projected (Mbps) = (apUlRsrvPuscSlotsCbrCir * apUlAvgMcsCbrCir) / (1M *

Stats Collection

Period)

.

Corrective Action:

Corrective actions related to large amounts of reserved bandwidth in either the

Downlink or Uplink directions may be addressed by the following solutions:

• If the carrier is operating in a trunked modem configuration, move to a nontrunked

modem configuration, such that additional air interface capacity may

be accommodated in a given carrier.

• Migrate from 1x3x1 to 1x3x3 frequency re-use pattern to reduce interference

and increase capacity. This would also include enabling the use of all PUSC

sub-channels within a carrier.

Note: Modification of PUSC sub-channels will cause interference pattern

differences, causing potential cell coverage impacts.

• Migrate from 3.5 MHz to 7 MHz channel bandwidths, or from 5 MHz to 10

MHz channel bandwidths

• Increase available slots by reducing the MAP repeat rate allowing the MAP

to consume less Downlink Bandwidth slots.

Note: reducing the MAP repeat rate will decrease MAP overhead and additional

Downlink RF capacity. However, it will also reduce cell coverage.

The slots consumed by the MAP are indicated by apMapSlotsUsed.

• If the Downlink bandwidth is exceeded by CBR and CIR and there is available

Uplink Bandwidth, then

a) increase the value of the Provisioning parameter PrcntAC_Bandwidth_DL,

or

b) change the Downlink/Uplink TDD Ratio.

• If the Uplink bandwidth is exceeded by CBR and CIR and there is available

Downlink Bandwidth, then

a) increase the value of the Provisioning parameter PrcntAC_Bandwidth_UL,

or

b) change the Downlink/Uplink TDD Ratio.

• Add APs to support additional RF capacity

Problem : Increased or excessive page time-outs

Increased Page time-outs could be caused by poor system coverage or excessive paging

Statistics: apPageCycles, apDropPageAp, apDelayedPages, apDlPagingSlotsUsed,

apTotalDlPuscSlotsAvail, capcInitPagesSent, capcPageRetrySent

An increase in capcPageRetrySent most likely indicates poor RF coverage or excessive

paging traffic. The percentage of page time-outs is given by the following equation:

Equation 5

Page time-out percentage =

(capcPageRetrySent/capcInitPagesSent)*100%.

This value should be less than 5% + (1 - Site coverage probability). Otherwise

poor RF cover may exist, and the items identified in Section 3.8 "GOAL - Diagnosis

of Poor RF Coverage" should be investigated.

A sharp, trended increase in capcPageRetrySent indicates that paging time-outs have

occurred for some reason:

Corrective Action:

• no pegs in apDropPageAp or apDelayedPages indicate that there is sufficient

paging capacity and the issue is most likely a RF coverage issue.

• pegs in apDropPageAp indicate that a corrective action could be (1) to

increase the configured AP “BTS paging interval” to a larger value (2) if

“BTS paging interval” is large, consider adding new paging group to

decrease the amount of paging per paging group.

• pegs in apDelayedPages indicate that a corrective action could be to consider

increasing the configured AP “BTS paging interval” to a larger value.

Paging Utilization:

The amount of paging traffic can be calculated and trended against population growth.

Paging utilization is a measure of the number of slots consumed for Broadcast Paging,

divided by the total number of available Downlink slots:

Equation 6

Paging Utilization (%) =

(apDlPagingSlotsUsed)/(apTotalDlPuscSlotsAvail) * 100%

Corrective Action:

If paging traffic becomes high, potential solutions include:

• Correct coverage issues by increasing the MAP repetition rate, move to a

more effective frequency re-use configuration to reduce interference, or add

APs to increase coverage.

• Decrease the number of paging retries per paging procedure

• Optimize paging groups, as discussed in Section 3.7 "GOAL - Paging Group

Optimization"

RF Utilization Trending for Capacity Planning

The Service Provider may want to be proactive, and therefore, trend RF utilization over

time. RF utilization over the air interface may be trended by computing the data traffic

(transmission and receipt of successful and unsuccessful payloads/slots) given the average

MCS levels and reserved bandwidth for the service flows.

Statistics: apMapSlotsUsed, apDlMacBroadcastSlotsUsed, apTxDivDlUnicastPusc-

Slots<DL TX Div Type>, apTotalDlPuscSlotsAvail, apTxDivUlPuscSlots<UL

TX Div Type>, apTotalUlPuscSlotsAvail, apDlPayloadKBCbr, apDlPayloadKBCir,

apDlPayloadKBBe, apUlPayloadKBCbr, apUlPayloadKBCir, apUlPayloadKBBe

Overall RF Utilization:

RF Downlink Utilization is a measure of all available and used Downlink slots for

broadcast and unicast messages divided by all Downlink slots.

Equation 7

RF Utilization Downlink (%) =

(apMapSlotsUsed + apDlMacBroadcastSlotsUsed + Total DL Unicast PUSC Slots Used

By All Tx Diversity Techniques) / (apTotalDlPuscSlotsAvail) * 100%

where:

Total DL Unicast PUSC Slots Used By All Tx Diversity Techniques =

apTxDivDlUnicastPuscSlots<DL TX Div Type> (MIMO-A) +

apTxDivDlUnicastPuscSlots<DL TX Div Type> (MIMO-B) +

apTxDivDlUnicastPuscSlots<DL TX Div Type> (TxAA-EBF) +

apTxDivDlUnicastPuscSlots<DL TX Div Type> (Base Diversity)

If RF Downlink Utilization is nearing the Service Provider’s maximum planning limits,

solutions include:

Corrective Action:

Adjust the MAP repeat rate (if possible) to reduce Downlink control channel utilization,

and free more Downlink bandwidth. This is especially helpful if the

Downlink Control Channel Utilization is excessive.

The Downlink control channel consists of the FCH and Downlink Broadcast MAC

Management messages. Its utilization is a measure of the available slots consumed for the

Downlink Control Channel components, divided by the total available Downlink slots.

Control Channel Utilization is given by the below equation:

Equation 8

Control Channel Utilization (%) = (apMapSlotsUsed + apDlMacBroadcastSlotsUsed)/

(apTotalDlPuscSlotsAvail) * 100

• Adjust the TDD ratio if there is available RF Uplink bandwidth (indicated by

RF Utilization Uplink (%))


• Migrate from 3.5 MHz to 7 MHz channel bandwidths, or from 5 MHz to 10

MHz channel bandwidths


RF Percent Uplink Utilization is a measure of all Uplink available and used slots divided

by all Uplink slots.

Equation 9

RF Utilization Uplink (%) =

(Total UL PUSC Slots Used By UL Tx Diversity Techniques)/(apTotalUlPusc-

SlotsAvail) * 100%

where:

Total UL PUSC Slots Used By All UL Tx Diversity Techniques = apTxDivUl-

PuscSlots<UL TX Div Type> (UL SDMA) + apTxDivUlPuscSlots<UL TX Div

Type> (MRC)

If RF Uplink Utilization is nearing the Service Provider’s maximum planning limits,

solutions include:

• Adjust the TDD ratio if there is available RF Downlink bandwidth (indicated by RF

Downlink Uplink (%))


• Migrate from 3.5 MHz to 7 MHz channel bandwidths, or from 5 MHz to 10 MHz

channel bandwidths


User throughput characterization

The user throughput per QoS service type can not be entirely characterized by the slots and

average MCS levels used by each service type, as such a metric includes MAC overhead

and retransmissions. The metric is, however, helpful to determine the air interface load

required to support the aggregate carrier population. In this regard, it would be beneficial

for the operator to compare the aggregate carrier air interface load to the actual payload

packets transferred. The payload Kilobytes per carrier does not include the MAC headers,

and therefore, would include such items as the Ethernet header (if Ethernet CS over the air

is supported), and the IP header.

The actual user payload bytes transferred per each QoS service type is pegged in total

Kilobytes and is reported as:

Downlink:

• CBR Kilobytes successfully transferred: apDlPayloadKBCbr

• CIR Kilobytes successfully transferred: apDlPayloadKBCir

Best Effort Kilobytes successfully transferred: apDlPayloadKBBe

Uplink:

• CBR Kilobytes successfully received: apUlPayloadKBCbr

• CIR Kilobytes successfully received: apUlPayloadKBCir

• Best Effort Kilobytes successfully received: apUlPayloadKBBe

HARQ Frame Erasure Rate Impact on Capacity

Various end to end services target differing Frame Erasure rates given the application type.

However, the Service Provider may wish to understand the resulting Frame Erasure rates

given the major QoS Service Types, and how they may impact RF capacity.

Statistics: apDlCbrBurstTxSucc, apDlCbrBurstTxAllFail, apDlCirBurstTxSucc,

apDlCirBurstTxAllFail, apDlBeBurstTxSucc, apDlBeBurstTxAllFail, apUl-

CbrBurstRxSucc, apUlCbrBurstRxOppAllFail, apUlCirBurstRxSucc, apUlCir-

BurstRxOppAllFail, apUlBeBurstRxSucc, apUlBeBurstRxOppallFail

The experienced frame erasure percentage per each QoS Service Type is defined below:

Downlink:

• Recommended maximum CBR Frame Erasure Rate: 10%

Equation 10

CBR Frame Erasure Rate (%) =

apDlCbrBurstTxAllFail/(apDlCbrBurstTxSucc + apDlCbrBurstTxAll-

Fail)*100%

• Recommended maximum CIR Frame Erasure Rate: 10%

Equation 11

CIR Frame Erasure Rate (%) =

apDlCirBurstTxAllFail/(apDlCirBurstTxSucc +apDlCirBurstTxAllFail)*100%

• Recommended maximum Best Effort Frame Erasure Rate: 10%

Equation 12

Best Effort Frame Erasure Rate (%) =

apDlBeBurstTxAllFail/(apDlBeBurstTxSucc +apDlBeBurstTxAllFail)*100%

Uplink:

• Recommended maximum CBR Frame Erasure Rate: 10%

Equation 13

CBR Frame Erasure Rate (%) =

apUlCbrBurstRxOppAllFail/

(apUlCbrBurstRxSucc + apUlCbrBurstRxOppAllFail)*100%

• Recommended maximum CIR Frame Erasure Rate: 10%

Equation 14

CIR Frame Erasure Rate (%) = (apUlCirBurstRxSucc + apUlCirBurstRxOppAllFail)*100%

• Recommended maximum Best Effort Frame Erasure Rate: 10%

Best Effort Frame Erasure Rate (%) =

Equation 15

apUlBeBurstRxOppallFail/

(apUlBeBurstRxSucc + apUlBeBurstRxOppallFail)*100%

Excessive Frame Erasure rates may indicate poor RF coverage. The impact to capacity is

a function of the Frame Erasure percentage, because transmissions will have to be retried

when they are not successful. Corrective actions when the FER of any of the above services exceed their

recommended values include:

Corrective Action:

• Implement the corrective actions for available RF capacity on the downlink

or uplink, as indicated in Section 3.1 "GOAL - RF Capacity Planning" “Available downlink or uplink RF

bandwidth reserved by existing Service Flows is causing denial of new or modifications to existing Service

Flow requests”.

• Deploy additional APs to mitigate coverage issues.

KPI Reprots

Quantify Network Entry/Re-Entry Success PercenatgeNetwork entry and network re-entry from idle mode success rates are one of the keyperformance indicators that the operator is interested in quantifying to validate if thesystem is performing according to specifications and agreement with Motorola. Also, theoperator needs to take the appropriate corrective actions to rectify any identified issuesimpacting those KPIsNetwork Entry Success PercentageNetwork entry goes through multiple phases, failure during any phase fails the networkentry and the MS is required to attempt network entry again to gain access to the WiMAXnetwork. The phases of network entry are:• Ranging (Receive of RNG-REQ with MAC address)• Capability Exchange• Authentication & Authorization• Registration• Preprovisioned Service Flows Setup: Establishing preprovisioned service flows. Forevery preprovisioned SF, admission control will check if there are enough resourcesin the system to admit the flow. If there are no resources, the preprovisioned SF setupwill fail. This type of failure is due to admission control failures (air interfaceresources, transport CID resources or backhaul resources), the carrier could beconfigured with low admission control thresholds for CIR & CBR or the carrier couldof reached its maximum capacity and can’t admit more users. For BE preprovisionedSF, the admission control function will check if there are transport CIDs availableand if there are no transport CIDs available, the SF establishment will fail. Since thefailure of NE due to admission control is related to system configuration and capacityplanning, the Network Entry Success rate will exclude attempts that failed due toadmission control.Statistics: apInitNetEntAtt, apInitNetEntSucc, apNeFailACThe statistic apNeFailAC represents number of NE attempts that failed due to admissioncontrol failure (not eneough air interface resources, or transport CIDS or backhaulresources).Equation 55

Network Entry Success Percenatge = 100% * apInitNetEntSucc / (apInitNetEntAtt- apNeFailAC)MSS initiated network re-entry from idle mode successPercentage

Equation 56MSS Initiated Network Re-Entry from Idle Mode Success Percentage =100% * apMssInitNetReEntSucc / apMssInitNetReEntAttIf the success rate is low:• Check authentication and authorization statistics (capcAuthAttemptPriAaa,capcAuthAttemptSecAaa, capcAccessAcceptPriAaa, capcAccessAcceptSecAaa,capcAccessRejectPriAaa, capcAccessRejectSecAaa, capcInitialAccessAcceptPriAaa,capcInitialAccessAcceptSecAaa) at CAPC for high authentication and authorizationfailure rate. If the rate is high, check the AAA configuration and make sure the usersare provisioned correctly. If the statistics (capcAccAuthMsgsFailedReTx,capcAaaEAPTimerExp and capcAaaTimerExp) are high this is an indication ofcommunication/link issues between CAPC and AAA, more investigation anddebugging is needed to root cause the problem and to correct it.• Check AP PMIP registration statistics (apPmipReg, apPmipRegFail) for high PMIPregistration failure rate.• If admission control failures are highly contributing to the over all NE failure (100%* apNeFailAC / (apInitNetEntAtt - apInitNetEntSucc)), then consider adjustingadmission control thresholds (if possible) or consider capacity expansion by addingnew carrier or site.• See 3.6 ‘GOAL - RF Optimization for Mobility’ for RF related corrective actions.

Quantify Idle Mode Entry Success PercentageIdle mode entry success rates are one of the key performance indicators (KPI) that theoperator is interested in quantifying to validate if the system is performing according tospecifications and agreement with Motorola. Also, the operator needs to take theappropriate corrective actions to rectify any identified issues impacting those KPIs.MSS initiated idle mode entry success percentageStatistics: apMssInitIdleAtt, apMssInitIdleSuccEquation 57MSS Initiated Idle Mode Entry Success Percentage = 100% * apMssInitIdle-Succ / apMssInitIdleAttFNE initiated idle mode entry success percentageStatistics: apBsInitIdleAtt, apBsInitIdleSuccEquation 58FNE Initiated Idle Mode Entry Success Percentage = 100% * apBsInitIdleSucc/ apBsInitIdleAttCorrective Action:If the success rate is low, refer to ‘GOAL - RF Optimization for Mobility’ for correctiveactions.Table 24. Statistics for Idle Mode Entry KPIs

Quantify Service Flow Establishment Success PercentageThe operator needs the ability to proactively view service flow performance characteristicsof the network. The visibility to the performance characteristics of how service flows areworking gives the operator the ability to determine if certain actions need to be pursued torectify issues. The visibility to performance metrics also gives them a baseline when

determining if certain actions rectified the problem.BS Initiated Service Flow Addition Success PercentageStatistics: apDsaReq, apDsaSuccEquation 59BS Initiated Service Flow Addition Success Percenatge = 100% * apDsaSucc /apDsaReqMS Initiated Service Flow Addition Success PercentageStatistics: apMsInitSfAddReq, apMsInitSfAddSucc, apMsInitFlowNotAdmtEquation 60MS Initiated Service Flow Addition Success Percentage = 100% * apMsInitSfAddSucc/ apMsInitSfAddReqEquation 61MS Initiated Service Flow Addition Failure Percentage (Not Including AdmissionControl Failures) = 100% * (apMsInitSfAddReq - apMsInitSfAddSucc -apMsInitFlowNotAdmt) / apMsInitSfAddReqService Flow Change Success PercenatgeStatistics: apDscReq, apDscSuccEquation 62Service Flow Change Success Rate = 100% * apDscSucc / apDscReqThe BS and the MS uses the SF change procedure (DSC) to change thecharacteristics of an established SF. The following are some of the DSC triggeringconditions:• Change PHS (Packet Header Suppression) rules• Change Packet Classification rules• Change SF rate.Service Flow Deletion Success PercentageStatistics: apDsdReq, apDsdSuccEquation 63Service Flow Deletion Success Percentage = 100% * apDsdSucc / apDsdReq

The paging rate is impacted by the paging cycle (wmanIfBsPagingCycle), paging interval(wmanIfBsPagingInterval) and the number of network re-entry that can be completedconcurrently. The operator will be interested to quantify the paging success rate in order totake the appropriate action if the rate is below the planned success rate.Paging Success PercentageStatistics: capcInitPagesSent, capcPageTimeoutsEquation 64Paging Success Percentage = 100% * (capcInitPagesSent - capcPageTimeouts)/capcInitPagesSentEquation 65Paging Arrival Rate (Pages/Sec) = capcInitPagesSent / (Statistics CollectionInterval)Corrective Action: If the paging success rate is below the planned rate, the followingactions can be taken to rectify that:• Analyze network re-entry metrics over consecutive statistics collection intervals,if the network re-entry success rate is low this could be the reason forhigh paging failure rates, refer to GOAL - Quantify Network Entry/Re-EntrySuccess Percenatge for more details and corrective actions.• If the paging arrival rate is high and the paging success rate is low, increasing

the paging interval (wmanIfBsPagingInterval) can increase the rate of pagingmessages over the air and decrease paging latency. Thorough analysis shouldbe done before adjusting this parameter because increasing it increases theDL control channel overhead.• Paging group optimization activity is recommended to improve paging successrate.

Quantify Service Interruption RateThe failure of a number of critical procedures will result in the subscriber’s WiMAXconnection to be dropped, forcing the subscriber to re-enter the network, and after someloss of service, re-initiate its data session. It is important to quantify the serviceinterruption rate to measure if the system is meeting the published rate. The serviceinterruption rate is a measure of number of service interruptions per subscriber per hour.Service interruptions occur for both active and idle subscribers and is tracked at both APand ASN-GW.Overall System Service Interruption RateStatistics: capcPageTimeouts, capcLuTimeout, capcLuFail, capcAKTimeout, capcIdleMssFullNE,capcAvgIdleMss, apDregLostActvMss, apDregMssInit,apDregCapcProcTimeout, apDregCapcProcFail, apDregOther, apUsersActSlp,apNbrBsHoAttmpts, apNbrBsHoSucc, apHoRngRspSucc, apCoordHoSucc,apUnexpHoSuccThe service interruption rate does not include interruptions due to AP or carrier outage.The operator can extrapolate the service interruption rate by analyzing the serviceinterruption metrics over long statistics intervals.Equation 66Service Interruptions for Idle subscribers =(capcPageTimeouts)ALL PGs + (capcLuTimeout + capcLuFail + capcAKTimeout+ capcIdleMssFullNE)ALL pCAPCs

Equation 67Service Interruptions for Active subscribers due to HO failure =(apNbrBsHoAttmpts - apNbrBsHoSucc)ALL NEIGHBOR CARRIERS

Equation 68Service Interruptions for Active subscribers =(apDregLostActvMss + apDregMssInit + apDregCapcProcTimeout + apDreg-CapcProcFail + apDregOther)ALL CARRIERS +(Service Interruptions for Active subscribers due to HO failure)Equation 69Overall Service Interruption Rate = ((Service Interruptions for Idle subscribers)+ (Service Interruptions for Active subscribers))/ (apUsersActSlpALL carrierS

+ capcAvgIdleMssALL pCAPCs) / (Statistics Interval in Hours)Equation 70Carrier Service Interruption Rate for Active Users = (Service Interruptions forActive subscribers) / (apUsersActSlp) / (Statistics Interval in Hours)Equation 71Service Interruption Rate for Idle Users = (Service Interruptions for Idle subscribers)/ (capcAvgIdleMssALL pCAPCs) / (Statistics Interval in Hours)

Equation 72Percentage of idle users service interruption due to Page Timeouts = 100% *(capcPageTimeouts)ALL PGs / (Service Interruptions for Idle subscribers) / (StatisticsInterval in Hours)

Equation 73Percentage of idle users service interruption due to Location Update Timeouts= 100% * (capcLuTimeout)ALL pCAPCs / (Service Interruptions for Idle subscribers)/ (Statistics Interval in Hours)Equation 74Percentage of active users service interruption triggered by MSS = 100% *(apDregMssInit)ALL CARRIERS / (Service Interruptions for Active subscribers) /(Statistics Interval in Hours)Equation 75Percentage of active users service interruption due to lost communication withMSS = 100% * (apDregLostActvMss)ALL CARRIERS / (Service Interruptions forActive subscribers) / (Statistics Interval in Hours)Equation 76Percentage of active users service interruption due to AP timing out forresponse from CAPC = 100% * (apDregCapcProcTimeout)ALL CARRIERS / (ServiceInterruptions for Active subscribers) / (Statistics Interval in Hours)Corrective Action: If the Overall Service Interruption Rate is higher than theplanned rate, the following actions can be taken to understand the cause(s) ofincreased service interruption:• If the Percentage of idle users service interruption due to Page Timeouts ishigh, refer to Section 5.5 "GOAL - Quantify Paging Success Percentage" forcorrective actions.• If the Percentage of idle users service interruption due to Location UpdateTimeouts is high, refer to Section 5.1 "GOAL - Quantify Network Entry/Re-Entry Success Percenatge" for corrective actions.• If the Percentage of active users service interruption due to lost communicationwith MSS is high, refer to Section 3.5.2 "Identify RF coverage, interferenceand configuration issues that increase MSS deregistration" forcorrective actions. The statistic apDregLostActvMss represents number oftimes AP lost communication with the MSS. AP detects lost communicationwith the MSS in the following cases: 1) Registered MSS performs full networkentry 2) AP times out waiting for response from the MSS 3) Maximumnumber of ARQ Resets reached• If the Percentage of active users service interruption due to AP timing out forresponse from CAPC is high, this could be due to AP-CAPC backhaul issues,refer to Section 4.2 "GOAL - Backhaul Availability" for corrective actions.

Quantify Access Failure RateAccess Failure Rate is a measure of the failure rate of service flow establishment after asuccessful network entry per total MSSs per Hour.Access Failure Rate% of Access Failure = (Total Number of Access Failures - Access Failures due toAdmission Control) / Access AttemptsAccess Failure Rate (Failure/MSS/Hour) = (Total Number of Access Failures - AccessFailures due to Admission Control) / (Total number of established sessions) / HourWhere:• Total Number of Access Attempt: Number of service flow establishmentattempt after a successful network entry.• Access Failure: Number of failed service flow establishment attempts after asuccessful network entry.• Access Failures due to Admission Control: Number of failed service flow

establishment attempts after a successful network entry due to admissioncontrol failure.• Total number of established sessions: (Number of Active Users at the start ofreporting period + Number of Successful Network Entry Attempts during thereporting period)Statistics: apMsInitSfAddReq, apMsInitSfAddSucc, apMsInitFlowNotAdmt, apInitNetEntSucc,apUsrsStartSciEquation 77Access Failure Rate (Failures/MSS/Hour) = (apMsInitSfAddReq - apMsInitSfAddSucc- apMsInitFlowNotAdmt) / (apUsrsStartSci + apInitNetEntSucc) /(Report Duration)Equation 78% Access Failure = 100% * (apMsInitSfAddReq - apMsInitSfAddSucc - apMsInitFlowNotAdmt)/ apMsInitSfAddReqEquation 79% Blocked Access = 100% * apMsInitFlowNotAdmt / apMsInitSfAddReq

Quantify Dropped Session RateDropped Session Rate is a measure of Data Session drops (drop/lost of MS WiMAXconnection) after successful establishment in terms of number of dropped sessions perMSS per Hour. The operator needs the ability to monitor the dropped session rate in orderto correct any issues causing higher than expected rate.The dropped session does not include the following:• A drop of a Service Flow does not count towards a dropped session. A drop of a datasession only counts once towards a dropped session, regardless of the number ofservice flows on the session.• Normal device power down and device initiated DREG are not included in thedropped session rate.The session drop rate (SDR) is defined as:Equation 80SDR = (Number of Dropped Sessions) / (Total Number of Established Sessions)/ (Report Duration)Where:Number of Dropped Sessions = apDregLostActvMss + apDregCapcProcTimeout+ apDregCapcProcFail + apDregOther + SUMOverAllNeighbors(apNbrBsHoAttmpts- apNbrBsHoSucc)Total Number of Established Sessions = apUsrsStartSci (At the Start of thereport interval) + apInitNetEntSuccEquation 81% of Dropped Sessions due to RF reasons = 100% * apDregLostActvMss /Number of Dropped SessionsEquation 82% of Dropped Sessions due to Failed HO = SUMOverAllNeighbors(apNbrBsHoAttmpts- apNbrBsHoSucc) / Number of Dropped SessionsIf the session drop rate is higher than the system expected value of (5%), the operator canuse the following corrective actions to understand the reason behind the high drop rate andrectify the problemCorrective Action: If the ‘% of Dropped Sessions due to RF reasons’ is high, this isan indication of RF quality issues. The BS is loosing RF communication withthe MS while the MS is in the active/sleep state. The operator needs to investigatesite coverage. Also, there could be some devices with low CINR that is

enough to successfully perform network entry and establish a WiMAX connection,and then the CINR drops to low value and looses connectivity with the system.The operator needs to monitor such devices and resolve the signal qualityissue (the devices can be determined using the DREG logs collected at the sectorwith high ‘% of Dropped Sessions due to RF reasons’)

Documents

Basic WiMAX Network Optimization Things