52479642 Performance Analysis Per Transceiver Basis

Performance Analysis per Transceiver Basis

PERFORMANCE ANALYSIS PER TRANSCEIVER BASIS..................................................................1

ABSTRACT ...................................................................................................................................................2

INTRODUCTION..........................................................................................................................................2

BTS STATISTICS..........................................................................................................................................2

2.1 DESCRIPTION OF MEASUREMENTS..................................................................................................................32.1.1 Intermittent Fault Measurement......................................................................................................32.1.2 TRA Synchronization Fault Measurement......................................................................................32.1.3 Connection Statistics Measurement................................................................................................3

BTS COUNTERS AND OBJECT TYPE.......................................................................................................................32.2.1 Transceiver Group..........................................................................................................................4

PC TRASYNCCNT TRA SYNCHRONIZATION FAULTS. INCREMENTED WHEN A ....................................................4 TRA SYNCHRONIZATION FAULT IS REPORTED, BY THE BTS, .............................................................................4ON ONE OF THE TIMESLOTS WITHIN THE TG .........................................................................................................4

2.2.2 Timeslots..........................................................................................................................................4PC CONCNT Connection setup attempts. Incremented each time a ....................................................4

2.3 BTS STATISTIC AND FORMULA.....................................................................................................................52.4 CAPABILITIES..............................................................................................................................................5

2.4.1 Object Type: MOTG........................................................................................................................5 NUMBER OF COUNTERS = 2............................................................................................................................5

2.4.2 Object Type: MOTS.........................................................................................................................5

TOTAL LOAD CONTRIBUTION = NUMBER OF TSS * (NUMBER OF COUNTERS + TS STATE INDICATOR)..................................................................................................................................................5

3. MOTS STATISTICS COLLECTION......................................................................................................6

Even though the object type MOTS is not enabled, it is still possible to fetch the counter statistics for both CONCNT and CONERRCNT. This is done by using the command RXMFP in the OSS:...............6

3.1 COMMAND DESCRIPTION: RXMFP..............................................................................................................63.2 EXECUTING THE RXMFP COMMAND.............................................................................................................6WHERE XX IS THE TG NUMBER........................................................................................................................63.3 COUNTER SIZE............................................................................................................................................73.4 COLLECTING THE COUNTER STATISTICS............................................................................................................7

If ..............................................................................................................................................................7Then..........................................................................................................................................................7CONCNTt = 65535 - CONCNTbefore + CONCNTafter (2)..............................................................7

3.5 RECOLLECTION OF STATISTICS.......................................................................................................................8

4. DROPPED CALL RATE...........................................................................................................................8

4.1 DROPPED CALL RATE PER TIMESLOT................................................................................................................84.2 DROPPED CALL RATE PER TRX ....................................................................................................................9

5. TABULATING STATISTICS ..................................................................................................................9

5.1 COMMAND DESCRIPTION.............................................................................................................................105.1.1 Command description RXCDP......................................................................................................105.1.2 Command description RXHDP.....................................................................................................10

5.2 TABULATING COUNTER VALUES FOR NON FREQUENCY HOPPING CELLS................................................................115.3 TABULATING COUNTER VALUES FOR SYNTHESIZER HOPPING CELLS.....................................................................135.4 TABULATING COUNTER VALUES FOR BASEBAND HOPPING CELLS ........................................................................14

6. ANALYSIS OF TIMESLOT PERFORMANCE...................................................................................20

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6.1 FREQUENCY INTERFERENCE – NON HOPPING.................................................................................................206.2 FREQUENCY INTERFERENCE – SYNTHESIZER HOPPING.....................................................................................216.3 FREQUENCY INTERFERENCE – BASEBAND HOPPING........................................................................................216.4 HARDWARE FAULTY ..................................................................................................................................22

7. SUMMARY...............................................................................................................................................22

8. REFERENCE............................................................................................................................................23

Abstract

The process of radio network optimization involves investigation of cells having bad

performance. This is regardless of any poor KPI figures, for example, high drop call rate,

low handover success rate, poor call setup success rate and etc. The are many reasons that

contribute to the poor cell performance. This document describes one of many techniques

to identify if a particular transceiver unit or specific timeslots causes the problem and

highlight some of the method to troubleshoot the problem. The KPI being focussed in

discussion is the dropped call rate.

Introduction

There are many types of cell configuration. There are cells with one, two, or more

transceiver unit (TRU). This is due to the design and capacity requirement. The

performance of all transceiver unit and timeslots within a cell should be fairly similar.

This statement is true to a certain extend, where the frequency plan as well as both

hardware and software version and reliability needs to be taken into account. Hence,

should there be a large variation in terms of each transceiver’s performance, the problem

should be further analyzed.

BTS Statistics

The following describes the BTS level statistics that can be used to monitor the

performance of the cells.

15 October, 2001 2

2.1 Description of Measurements

2.1.1 Intermittent Fault Measurement

One intermittent fault counter exists per transceiver group (TG). The counter is

stepped when an intermittent fault is reported on one of the managed objects within the

TG.

2.1.2 TRA Synchronization Fault Measurement

One TRA synchronization fault counter exists per transceiver group (TG). The

counter is stepped when a TRA synchronization fault is reported, by the BTS, on one of

the Timeslots within the TG.

2.1.3 Connection Statistics Measurement

There are two counters per Timeslot Handler (TS), one stores connection setup

attempts on logical channels served by the TS and the other stores abnormally terminated

connections on logical channels served by the TS. The first counter is stepped each time a

Traffic Channel (TCH) or Stand Alone Dedicated Control Channel (SDCCH) is seized.

The second counter is stepped for TCH and SDCCH whenever a connection is dropped

due to any of the following reasons:

• Error indication

• Connection failure indication

• Abnormal disconnect request (due to Timing Advance larger than the value specified

for the cell or number of Measurement Results received less than specified for the

cell)

• Trace failure at Small Restart

• Forlopp release

BTS counters and object type

There are two types of counters, namely Peg Counter (PC) and Status Counter (ST).

PC is Peg Counter, where it shows the accumulated number of events or the accumulated

value of a counter. A peg counter can only be incremented. While ST shows the counter

15 October, 2001 3

value at a specific moment (i.e. snapshot). A status counter can be incremented or

decremented.

2.2.1 Transceiver Group

Object Type = MOTG (Managed Object Transceiver Group)

Measurements are done per transceiver group record.

In order to allow insertion of the INTERCNT and TRASYNCCNT counters, the TG must

be defined.

Type Counter Name Description

PC INTERCNT Intermittent faults. Incremented when an

intermittent fault is reported on one of the managed

objects within the TG

PC TRASYNCCNT TRA synchronization faults. Incremented when a

TRA synchronization fault is reported, by the BTS,

on one of the timeslots within the TG

2.2.2 Timeslots

Object Type = MOTS (Managed Object Time Slot Handler)

Measurements are done per Time Slot Handler (TS)

In order to allow insertion of the CONERRCNT and CONCNT counters, the TS must be

defined.

Type Counter Name Description

PC CONERRCNT Abnormally terminated connections. Incremented

for TCH and SDCCH when a connection is dropped

due to reasons specified in 2.1.3

PC CONCNT Connection setup attempts. Incremented each time a

TCH or SDCCH is seized

15 October, 2001 4

2.3 BTS Statistic and formula

One very useful statistic to be monitored is Drop Connections on Timeslot Basis

The formula is calculated per TS regardless of SDCCH or TCH connections.

TS_DR = Abnormally Terminated Connections of Total Number of

Connection Setup Attempts

= %100CONERRCNT

CONCNT ∗

2.4 Capabilities

The size of the counters is 16 bits. The number of counters to be handled by the STS

Database is limited. The capacity of STS is shared among the statistical measurement

functions in the BSC. Therefore when these BTS statistic counters are enabled, it will

occupied an amount of capacity and thereby, increasing the STS load.

2.4.1 Object Type: MOTG

Total load contribution = Number of TGs * (Number of counters + TG state

indicator)

Where Number of TGs is size alterable and max size is 512.

Number of counters = 2

TG state indicator = 1

2.4.2 Object Type: MOTS

Total load contribution = Number of TSs * (Number of counters + TS state indicator)

Where Number of TSs is size alterable and max size is 8160.

Number of counters = 2

TS state indicator = 1

The amount of statistics expected to be pegged for the MOTS counters can be done by

estimating at the amount of timeslots that exist in a BSC. Looking at the amount of

timeslots in a BSC, this will certainly increase the load for STS measurements. That is

why, this object type is normally not enabled in a network.

15 October, 2001 5

To be able to fetch the statistics from object type MOTS, while not increasing the STS

load, an alternative method can be used. This method is described in the next section.

3. MOTS statistics collection

Even though the object type MOTS is not enabled, it is still possible to fetch the counter

statistics for both CONCNT and CONERRCNT. This is done by using the command

RXMFP in the OSS:

3.1 Command Description: RXMFP

This command initiates the printing of fault information for one or more managed

object instances or all defined managed object instances of a specified managed object

type. The operator can specify, using the parameter FAULTY, that the information is

only printed for faulty managed object instances.

A managed object instance is considered to be faulty if it is blocked from its own

supervision in state NOOP, or is in state FAIL.

The operator can specify, using the parameter SUBORD, that information is also

printed on all managed object instances subordinate to one or more specified managed

object instances.

No more than 32 managed object instances can be specified in the command. The order

does not remain after system restart [2].

3.2 Executing the RXMFP command

Below describes how to execute the command to fetch statistics for both CONCNT and

CONERRCNT.

RXMFP:MO=RXOTS-XX-YY-0&&-7;

Where XX is the TG number

YY is the TRX number

0&&-7 specifies timeslot 0 to timeslot 7

15 October, 2001 6

3.3 Counter size

Since the size of the counter for both CONCNT and CONERRCNT is only 16 bits,

when the counters reached a maximum value of 65535 (which is calculated by 216-1), the

counter will reset to zero and start counting again.

3.4 Collecting the counter statistics

As highlighted earlier, the counter statistics are able to be collected using the

RXMFP command. But the duration between collection of statistic counters before and

after needs to be carefully defined. A period of two to three hours is recommended.

The counter CONCNT and CONERRCNT will give an accumulation value of connection

establishment and abnormal connection termination for a particular timeslot respectively

at a particular time. But looking at this is a peg counter, these counters are accumulated

each time the event occur.

Let say CONCNTbefore and CONERRCNTbefore are values collected initially and

CONCNTafter and CONERRCNTafter are values collected after a certain period of time, t.

Since the counter will reset to 0 when it reaches 65535, there is a possibility that the

counter values collected after time duration is less than what it was before. Therefore, to

determine what was the number of connection establishments during that specified period

of time, the equation below are used.

Let’s say number of connection establishment during time t is denoted as CONCNTt

If

CONCNTafter > CONCNTbefore ,

Then,

CONCNTt = CONCNTafter - CONCNTbefore (1)

If

CONCNTafter < CONCNTbefore ,

Then

CONCNTt = 65535 - CONCNTbefore + CONCNTafter (2)

Similarly, the number of abnormal connection terminations for that specified period of

time CONERRCNTt can be determined by replacing CONCNT with CONERRCNT in

15 October, 2001 7

equation (1) and (2). Note that the period, t should not be set too long to prevent the

counters to reset more than one time and that will make equation (1) and (2) to be invalid.

This is because the counter accumulation depends on the amount of traffic and subscriber

behavior for this cell.

3.5 Recollection of statistics

If the value of connection establishment and abnormal connection terminations as

calculated from Section 3.4 are very small, then, it is recommended to recollect the

statistics for a longer time duration or/and at different hours, i.e. during peak hour.

Having more data samples will be able to draw better conclusion when analyzing the

timeslots performance.

If any of the timeslot configurations was changed, say a timeslot was block/deblock

or a TRU was being replaced during the statistic collection time, the values collected will

not be valid. Then, it is essential to recollect the statistics again.

4. Dropped call rate

Useful hints can be obtained by looking at the number of abnormal connection

terminations on each timeslot. Since the allocation of timeslot to the mobile station is

being done according to the ICM band, timeslots with small number of connection

establishments may yields higher ICM band as compared to those timeslots with higher

number of connection establishments. Hence, poor performance may be suspected at

these high ICM band timeslots. However this may not be 100% true. For example,

timeslots that have hardware problem but good ICM band may have more connection

establishments. Nonetheless the drop connections may as well results a high number.

Consequently, by just looking at the timeslots with a high number of abnormal

connections termination may not yield bad performance. It is more valid to look at the

dropped call rate instead.

4.1 Dropped call rate per timeslot

The dropped call rate per timeslot, during time, t (TS_DRt) can be determined based on

the following equation:

15 October, 2001 8

%1 0 0C O N C N T

C O N E R R C N TD R_T S

t

tt ∗=

4.2 Dropped call rate per TRX

Similarly, the dropped call rate per TRX during time, t (TRX_DRt) can be calculated as

below.

%1 0 0t,t i m e_d u r i n g_T R X_p e r_e s t a b_C o n n e c t i o n

t,t i m e_d u r i n g_T R X_p e r_c o n n e c t i o n_D r o pD R_T R X t ∗=

∑= i it )C O N E R R C N T(t,t i m e_d u r i n g_T R X_p e r_c o n n e c t i o n_D r o p

∑= i it )C O N C N T(t,t i m e_d u r i n g_T R X_p e r_n te s t a b l i s m e_C o n n e c t i o n

where i ranged from 0 to 7, denoting the TCH timeslots in particular TRX.

For the BCCH TRX, timeslot 0 is used to carry BCCH and therefore, no call

establishment is allowed in this timeslot. Therefore, i ranged from 1 to 7 for BCCH TRX.

Timeslot 0 is not included in the calculation.

Correspondingly, when evaluating the TCH dropped call performance, the timeslots

carrying SDCCH should also be excluded in the calculation.

5. Tabulating Statistics

The printout from command RXMFP will be able to display the statistic CONCNT and

CONERRCNT for every timeslot. These timeslots are represented in this format as below.

Timeslot = RXOTS-XX-YY-Z

Where XX is the Transceiver Group (TG) number

YY is the TRX number

Z is the timeslot number (0-7)

15 October, 2001 9

These timeslots representation is just software based interpretation and does not map

directly to the hardware position. For example, RXOTS-20-0-1 represents slot number 1

at TRX0 and TG20 in the software point of view, but it is not necessary that these

timeslot points to slot number 1 at TRX0 in the physical TRU.

By default the timeslots representation in software should be inline with the hardware.

But the inconsistency may due to various reasons. For example, a block/deblock

command was carried out for some MO or one of the TRX is faulty and etc.

Hence, when tabulating the counter values, it is necessary to find out exactly which

timeslot in the software corresponds to which timeslot in the hardware TRU. A way to do

this by using command RXCDP and RXHDP.

5.1 Command description

Both the commands RXCDP and RXHDP will be describe in brief in the following

section. More information can be obtained at [2].

5.1.1 Command description RXCDP

The command is used to initiate printing of managed object (MO) configuration data for

one or more managed object instances. The answer printout, “RADIO X-CEIVER

ADMINISTRATION MANAGED OBJECT CONFIGURATION DATA”, indicates how

each MO specified in the MO parameter is configured. When the MO class TG is

specified, MO configuration data for all related RX, TS, TX and DP are printed. The

order does not remain after system restart [2].

5.1.2 Command description RXHDP

This command is used to initiate printing of MO hopping data for one or more MO

instances. The answer printout, “RADIO X-CEIVER ADMINISTRATION MANAGED

OBJECT HOPPING DATA”, indicates how each managed object specified in the MO

parameter is configured for frequency hopping. The order does not remain after system

restart [2].

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5.2 Tabulating counter values for non frequency hopping cells

15 October, 2001 11

When frequency hopping is disabled, the process to find the mapping of the timeslot in

hardware and software is fairly straightforward. The command to be used is RXCDP.

Every TRX will have its own dedicated absolute radio frequency channel number

(ARFCN) and this will be the information used to differentiate the TRXs. Example of the

RXCDP command printout is shown as follows.

Figure 5.2.1 Answer printout for command RXCDP

15 October, 2001 12

<RXCDP:MO=RXOTG-170;

RADIO X-CEIVER ADMINISTRATIONMANAGED OBJECT CONFIGURATION DATA

MO RESULT ARFCN MISMATCHRXORX-170-0 CONFIG HOP NONERXORX-170-1 CONFIG HOP NONERXORX-170-2 CONFIG HOP NONERXORX-170-3 CONFIG HOP NONE

MO RESULT ARFCN TXAD TN BPC CHCOMB OFFS XRA ICMRXOTS-170-0-0 CONFIG 811 9 7 3270 TCH 0 NO ONRXOTS-170-0-1 CONFIG 811 9 6 3252 TCH 0 NO ONRXOTS-170-0-2 CONFIG 811 9 5 3218 TCH 0 NO ONRXOTS-170-0-3 CONFIG 811 9 4 3201 TCH 0 NO ONRXOTS-170-0-4 CONFIG 811 9 3 3174 TCH 0 NO ONRXOTS-170-0-5 CONFIG 811 9 2 3161 TCH 0 NO ONRXOTS-170-0-6 CONFIG 811 9 1 3122 TCH 0 NO ONRXOTS-170-0-7 CONFIG 811 9 0 3107 TCH 0 NO ONRXOTS-170-1-0 CONFIG 798 10 7 3164 TCH 0 NO ONRXOTS-170-1-1 CONFIG 798 10 6 3110 TCH 0 NO ONRXOTS-170-1-2 CONFIG 798 10 5 3100 TCH 0 NO ONRXOTS-170-1-3 CONFIG 798 10 4 3093 TCH 0 NO ONRXOTS-170-1-4 CONFIG 798 10 3 3084 TCH 0 NO ONRXOTS-170-1-5 CONFIG 798 10 2 3082 TCH 0 NO ONRXOTS-170-1-6 CONFIG 798 10 1 3078 TCH 0 NO ONRXOTS-170-1-7 CONFIG 798 10 0 3077 TCH 0 NO ONRXOTS-170-2-0 CONFIG 774 2 1 3308 SDCCH8 0 NO ONRXOTS-170-2-1 CONFIG 762 11 7 3254 TCH 0 NO ONRXOTS-170-2-2 CONFIG 762 11 6 3238 TCH 0 NO ONRXOTS-170-2-3 CONFIG 762 11 5 3217 TCH 0 NO ONRXOTS-170-2-4 CONFIG 762 11 4 3187 TCH 0 NO ONRXOTS-170-2-5 CONFIG 762 11 3 3171 TCH 0 NO ONRXOTS-170-2-6 CONFIG 762 11 2 3149 TCH 0 NO ONRXOTS-170-2-7 CONFIG 762 11 0 3118 TCH 0 NO ONRXOTS-170-3-0 CONFIG 774 2 0 3300 BCCH 0 NO ONRXOTS-170-3-1 CONFIG 774 2 2 3281 SDCCH8 0 NO ONRXOTS-170-3-2 CONFIG 762 11 1 3243 TCH 0 NO ONRXOTS-170-3-3 CONFIG 774 2 7 3213 TCH 0 NO ONRXOTS-170-3-4 CONFIG 774 2 6 3176 TCH 0 NO ONRXOTS-170-3-5 CONFIG 774 2 5 3162 TCH 0 NO ONRXOTS-170-3-6 CONFIG 774 2 4 3137 TCH 0 NO ONRXOTS-170-3-7 CONFIG 774 2 3 3108 TCH 0 NO ON

MO RESULT ARFCN TXAD BSPWR C0F MISMATCHRXOTX-170-0 CONFIG 774 2 45 YES NONERXOTX-170-1 CONFIG HOP 9 45 NO NONERXOTX-170-2 CONFIG HOP 10 45 NO NONERXOTS-170-3 CONFIG HOP 11 45 NO NONE

According to the command printout in Figure 5.2.1, this cell is using TG170, with 4

TRX. Frequency hopping is disabled and the ARFCN used is 774 (BCCH), 762, 798 and

811.

RXOTS-170-0-0 is corresponding to TXAD9 and TN7. This proves that RXOTS-170-0-0

is the software does not correspond to hardware timeslot 0 of first TRU. But, it is actually

mapped to timeslot 7 in TRU9 physically.

While all RXOTS-170-2-X (where X is 1,2,3,..7) are mapped to TRU11, RXOTS-170-2-0

is mapped to TRU2. Similarly, all RXOTS-170-3-X (where X is 0,1,7 except 2) are

mapped to TRU2 while RXOTS-170-3-2 is mapped to TRU11.

Therefore when determining the dropped call per TRX for this cell, the table below

should be used.

TRU TXAD TN ARFCN MO CONCNTbefore CONERRCNTbefore CONCNTafter CONERRCNTafter

TRU0

2 0 774 RXOTS-170-3-02 1 774 RXOTS-170-2-02 2 774 RXOTS-170-3-12 3 774 RXOTS-170-3-72 4 774 RXOTS-170-3-62 5 774 RXOTS-170-3-52 6 774 RXOTS-170-3-42 7 774 RXOTS-170-3-3

TRU1


TRU2


T

RU3


Table 5.2.1 Mapping of timeslots position between software and hardware

5.3 Tabulating counter values for synthesizer hopping cells

Tabulating counter values for synthesizer hopping cells (not hopping through BCCH) is

the same as described in section 5.3. The only difference is that under the column

ARFCN in RXCDP printout, the printout will be “HOP” for hopping TRXs and the

15 October, 2001 13

ARFCN for non-hopping (BCCH) TRX. The technique to distinguish the mapping of the

timeslots is identical.

5.4 Tabulating counter values for baseband hopping cells

When baseband frequency hopping is used, the process to find the mapping of the

timeslot in hardware and software is quite complicated. A straightforward method is to

disable the hopping and then repeat the process as discussed in section 5.4.

An alternative method is to use the command RXCDP as well as RXHDP. The parameter

to differentiate different TRU will be TXAD and MAIO. Example of the RXCDP and

RXHDP command printout is shown as follows. This method has yet to be verified to be

reliable for all the baseband hopping cells.

15 October, 2001 14

15 October, 2001 15

15 October, 2001 16

Figure 5.4.1 Answer printout for command RXCDP

According to Figure 5.4.1, the cell is having 4 TRX, using baseband hopping. The

BCCH frequency is 805 while the hopping TCHs are 805, 769, 781 and 793. Since

the TXAD at the MO RXOTS is displayed as “HOP” except for BCCH timeslot, that

is TXAD 0, it is therefore difficult to distinguish which RXOTS maps to which TRU.

Hence, the printout of RXHDP is used. Figure 5.4.2 shows an example of the

printout.

15 October, 2001 17

<RXCDP:MO=RXOTG-79;

RADIO X-CEIVER ADMINISTRATIONMANAGED OBJECT CONFIGURATION DATA

MO RESULT ARFCN MISMATCHRXORX-79-0 CONFIG HOP NONERXORX-79-1 CONFIG HOP NONERXORX-79-2 CONFIG HOP NONERXORX-79-3 CONFIG HOP NONE

MO RESULT ARFCN TXAD TN BPC CHCOMB OFFS XRA ICMRXOTS-79-0-0 CONFIG HOP HOP 1 6895 TCH 3 NO ONRXOTS-79-0-1 CONFIG HOP HOP 7 6889 TCH 3 NO ONRXOTS-79-0-2 CONFIG HOP HOP 6 6887 TCH 3 NO ONRXOTS-79-0-3 CONFIG HOP HOP 5 6871 TCH 3 NO ONRXOTS-79-0-4 CONFIG HOP HOP 4 6869 TCH 3 NO ONRXOTS-79-0-5 CONFIG HOP HOP 3 6867 TCH 3 NO ONRXOTS-79-0-6 CONFIG HOP HOP 2 6850 TCH 3 NO ONRXOTS-79-0-7 CONFIG HOP HOP 0 6838 TCH 3 NO ONRXOTS-79-1-0 CONFIG HOP HOP 1 6890 TCH 3 NO ONRXOTS-79-1-1 CONFIG HOP HOP 7 6888 TCH 3 NO ONRXOTS-79-1-2 CONFIG HOP HOP 6 6886 TCH 3 NO ONRXOTS-79-1-3 CONFIG HOP HOP 5 6870 TCH 3 NO ONRXOTS-79-1-4 CONFIG HOP HOP 4 6868 TCH 3 NO ONRXOTS-79-1-5 CONFIG HOP HOP 3 6865 TCH 3 NO ONRXOTS-79-1-6 CONFIG HOP HOP 2 6849 TCH 3 NO ONRXOTS-79-1-7 CONFIG HOP HOP 0 6837 TCH 3 NO ONRXOTS-79-2-0 CONFIG HOP HOP 1 5331 SDCCH8 3 NO ONRXOTS-79-2-1 CONFIG HOP HOP 7 6864 TCH 3 NO ONRXOTS-79-2-2 CONFIG HOP HOP 6 6862 TCH 3 NO ONRXOTS-79-2-3 CONFIG HOP HOP 5 6860 TCH 3 NO ONRXOTS-79-2-4 CONFIG HOP HOP 4 6854 TCH 3 NO ONRXOTS-79-2-5 CONFIG HOP HOP 3 6852 TCH 3 NO ONRXOTS-79-2-6 CONFIG HOP HOP 2 6848 TCH 3 NO ONRXOTS-79-2-7 CONFIG HOP HOP 0 6836 TCH 3 NO ONRXOTS-79-3-0 CONFIG 805 0 0 5345 BCCH 3 NO ONRXOTS-79-3-1 CONFIG HOP HOP 1 5864 SDCCH8 3 NO ONRXOTS-79-3-2 CONFIG HOP HOP 7 6863 TCH 3 NO ONRXOTS-79-3-3 CONFIG HOP HOP 6 6861 TCH 3 NO ONRXOTS-79-3-4 CONFIG HOP HOP 5 6859 TCH 3 NO ONRXOTS-79-3-5 CONFIG HOP HOP 4 6853 TCH 3 NO ONRXOTS-79-3-6 CONFIG HOP HOP 3 6851 TCH 3 NO ONRXOTS-79-3-7 CONFIG HOP HOP 2 6839 TCH 3 NO ON

MO RESULT ARFCN TXAD BSPWR C0F MISMATCHRXOTX-79-0 CONFIG 805 0 45 YES NONERXOTX-79-1 CONFIG 769 1 45 NO NONERXOTX-79-2 CONFIG 781 2 45 NO NONERXOTX-79-3 CONFIG 793 3 45 NO NONE

END

15 October, 2001 18

Figure 5.4.2.3 RXHDP printout for TRX2




<RXHDP:MO=RXOTS-79-0-0&&-7;

RADIO X-CEIVER ADMINISTRATIONMANAGED OBJECT HOPPING DATA

MO RESULT HSN MAIO ARFCN TXADRXOTS-79-0-0 CONFIG 4 1 769 1 781 2 793 3 805 0RXOTS-79-0-1 CONFIG 4 0 769 1 781 2 793 3 805 0RXOTS-79-0-2 CONFIG 4 0 769 1 781 2 793 3 805 0RXOTS-79-0-3 CONFIG 4 0 769 1 781 2 793 3 805 0RXOTS-79-0-4 CONFIG 4 0 769 1 781 2 793 3 805 0RXOTS-79-0-5 CONFIG 4 0 769 1 781 2 793 3 805 0RXOTS-79-0-6 CONFIG 4 0 769 1 781 2 793 3 805 0RXOTS-79-0-7 CONFIG 4 0 769 1 781 2 793 3END









MO RESULT HSN MAIO ARFCN TXADRXOTS-79-3-0 CONFIG 4 0 805 0RXOTS-79-3-1 CONFIG 4 0 769 1 781 2 793 3 805 0RXOTS-79-3-2 CONFIG 4 3 769 1 781 2 793 3 805 0RXOTS-79-3-3 CONFIG 4 3 769 1 781 2 793 3 805 0RXOTS-79-3-4 CONFIG 4 3 769 1 781 2 793 3 805 0RXOTS-79-3-5 CONFIG 4 3 769 1 781 2 793 3 805 0RXOTS-79-3-6 CONFIG 4 3 769 1 781 2 793 3 805 0RXOTS-79-3-7 CONFIG 4 3 769 1 781 2 793 3 805 0END

Based on concept of baseband hopping [3], the number of hopping frequencies will

depends on the number of TRXs. Thus, in the example above, 4 TRXs will baseband hop

over 4 frequencies. Timeslot 1-7 of all 4 TRXs will hop over 4 frequencies. Timeslot 0 of

BCCH TRX will not hop and it is used to transmit BCCH frequency all the time.

Timeslot 0 of non-BCCH TRX will only hop on 3 frequencies. Analyzing the printout

shown in Figure 5.4.2.1 to Figure 5.4.2.4, the RXOTS that has only 3 ARFCN will be

mapped to timeslot 0 of non BCCH TRXs, whilst RXOTS-79-3-0 having only one

ARFCN is mapped to timeslot 0 of the BCCH TRX. This can also be verified in RXCDP

printout as shown in Figure 5.4.1. The MAIO is then used to distinguish between the

different TRXs.

Assuming the MAIO parameter is set to default, therefore the MAIO management

will assign even MAIO in ascending order first, followed by odd MAIO in ascending

order [4]. In this example, the MAIO will be assigned in this order, 0, 2, 1 and followed

by 3.

Hence, all RXOTS with 4 ARFCN in Figure 5.4.2.1 to Figure 5.4.2.4 will be

distributed to their respective TRU according to the MAIO value. The corresponding

timeslot number in the TRU will be given in RXCDP command printout as shown in

Figure 5.4.1.

Similarly, all RXOTS with 3 ARFCN in Figure 5.4.2.1 to Figure 5.4.2.3 will be

distributed to their respective TRU according to the MAIO value. However in this case,

the BCCH TRX will not be taken into account, since timeslot 0 of BCCH TRX will not

hop. The corresponding timeslot number in the TRU is timeslot 0 for all the RXOTS. This

can also be proven in RXCDP command printout shown in Figure 5.4.1.

Therefore when determining the dropped call per TRX for this cell, the table below

should be used.

15 October, 2001 19

TRU TXAD TN MAIO MO CONCNTbefore CONERRCNTbefore CONCNTafter CONERRCNTafter

TRU0

(805)

0 0 BCCH-805 RXOTS-79-3-00 1 0 RXOTS-79-3-10 2 0 RXOTS-79-0-60 3 0 RXOTS-79-0-50 4 0 RXOTS-79-0-40 5 0 RXOTS-79-0-30 6 0 RXOTS-79-0-20 7 0 RXOTS-79-0-1

TRU1

(769)


TRU2

(781)


T

RU3

(793)


Table 5.4.1 Mapping of timeslot position between software and hardware

6. Analysis of timeslot performance

The statistic, subscriber perceived dropped call rate (T_DR-S) gives the dropped call

rate of the particular cell. Sometimes, investigation needs to be carried out up to per TRX

basis, and more over, per timeslot basis. Having the statistics as described in Chapter 4,

the cell performance can be investigated in more detail. The flow chart for the

optimization procedure is attached in Appendix I and Appendix II. Few reasons and

guides are described in following section.

6.1 Frequency interference – Non Hopping

Considering frequency hopping is unused, every TRX will have to operate at a

particular frequency. For example, a cell with 4 TRX, non hopping and running on

frequency f0, f1, f2, and f3 respectively, where f0 is the BCCH. If this cell is experiencing

high dropped call rate, possibly due to poor uplink or downlink quality, it is then possible

to check for frequency interference. Few methods can be employed to identify frequency

15 October, 2001 20

interference, such as performing frequency scanning at the field, doing drive test,

checking the ICM band values, checking frequency reuse distance from map (e.g.

MCOM), using coverage prediction tool in planning tools (e.g. TEMS Cell Planner) and

etc. Another method is to check the dropped call rate per TRX. If any particular TRX is

contributing a dropped call rate significantly higher than the others, then the frequency of

this TRX may have interference. Check the frequency of this TRX and perform retune if

necessary.

6.2 Frequency interference – Synthesizer Hopping

When frequency hopping is employed, the isolation of frequency interference

problem is trickier. For example, consider a cell with 4 TRX and using synthesizer

frequency hopping. Frequency f0 is the BCCH and f1, f2, f3, f4, f5, f6 f7, f8 and f9 are the

hopping frequencies. If this cell is experiencing high dropped call rate, possibly due to

poor uplink or downlink quality, check for any frequency interference. The ICM band

values of every timeslot will give an indication of bad uplink interference. It will be

helpful to check the dropped call rate per TRX in the given cell. If the BCCH TRX has a

much higher dropped call rate as compared to the hopping TRXs, check the BCCH

frequency (f0). Conversely, if all hopping TRXs have a significant higher dropped call

rate as compared with the BCCH TRX, check the TCH hopping frequencies (f0, f1…f9). It

is quite difficult to know which particular frequency/frequencies are having interference.

Therefore, it is recommended to disable hopping and then perform the same procedure as

described in Section 6.1. Since the number of frequencies in the Mobile Allocation (MA)

list is higher than the number of TRX in case of synthesizer frequency hopping, the

frequency equipped into each TRX once hopping being disabled need to be carefully

monitored. The search of which frequency is being interfered can be done one by one.

Once the interfered frequency/frequencies is/are identified, perform a frequency retune.

Another alternative will be changing the HSN or MAIO for the cell.

6.3 Frequency Interference – Baseband Hopping

If the cell is using baseband hopping, check the dropped call per TRX. For example,

consider a cell with 4 TRX (TRX0, TRX1, TRX2 and TRX3 where TRX0 is BCCH

TRX) and using baseband frequency hopping on frequency f0, f1, f2, and f3, where f0 is the

15 October, 2001 21

BCCH. All timeslots will be hopping on the same set of frequencies, except for timeslot 0

of TRX1, TRX2 and TRX3 where they are only hopping on f1, f2, and f3. Therefore

should there be any frequency interference, it should affect the performance on all

timeslots, except interference on BCCH channel. If particularly timeslot 0 of TCH TRX

(i.e. TRX1, TRX2 and TRX3) are having a much lower dropped call as compared to the

others, then, check the frequency interference on BCCH frequency. If all the TRXs are

having comparable dropped call rate, check all frequencies (f0, f1, f2 and f3). This is done

by disabling frequency hopping and repeating procedure as described in Section 6.1.

Otherwise, this may not be a frequency interference problem.

6.4 Hardware faulty

As discussed in Section 6.3, for baseband hopping, all timeslot hops on the same set

of frequencies except timeslot 0. If one of the TRXs is having very high dropped call rate

as compared to the others, this may be a clue that hardware fault exist.

As for synthesized hopping cells, if one of the hopping TRXs is having very high

dropped call rate as compared to the rest, then it may be a hardware problem. If the high

dropped call rate is at the BCCH TRX and no frequency interference is detected, it is also

possible that there is hardware faulty.

It is then advisable to check the drop call reason on cell level statistics. If the drop

call is due to low signal strength uplink, check the receive path of this particular TRX.

Check receiver sensitivity, VSWR, feeder connection and etc. If the drop call reason is

due to low signal strength downlink, then, check the transmit path. Check CDU, RTX

card, feeder and etc. Further information can be obtained from [1]

7. Summary

The usefulness of counter in MOTS is being described to ease the process of cell

optimization. When only a particular TRU is encountering bad performance as compared

to the others within the same cell, the probably reasons may either be frequency

interference or hardware fault. However, there may be more techniques to troubleshoot

the TRX performance and more reasons that lead to poor timeslot performance not

discussed here.

15 October, 2001 22

8. Reference

[1] Network Performance Improvement description for the area Dropped Calls LVR/P

97:0437 Rev B

[2] Alex Database BSC R8 BSS UM8 with APZ 212 20/220 IOG20 [LZN 301 115

P1AB]

[3] User Description, Frequency Hopping

[4] User Description, MAIO Management

15 October, 2001 23

15 October, 2001 24

15 October, 2001 25

15 October, 2001 26

Appendix I – Per TRX Drop call analysis for cell using Synthesized Hopping

yes

yes

no

yes

yes

Find interferenceno

yes

Change MAIO

Solve?

no

On all non BCCH TRX?

noNo alarm

?Hardware fault

yes

no

noParameters setting

correct?

Correct parameter setting

Solve?

Change HSN

Solve?

no

yes

Frequency retune

Solve?

A

yes

yes

yes

no

Only on BCCH TRX?

yes

no

noNo alarm

?

Parameters setting

correct?


Solve?

Hardware fault

no

yes

Frequency retune

Solve?

Synthesizer Hopping cell with High dropped

call

15 October, 2001 27

15 October, 2001 28

yes

yes

yes

no

On only one non BCCH TRX?

no

yes

Change MAIO

Solve?

noNo alarm

?Hardware fault

A

yesOn all TRXs?

noNo alarm

?Hardware fault

no

yes

Interference on all TRXs?

no

yes

Solve?

Frequency retune

yes

no

noParameters setting

correct?


Solve?

Hardware faultCheck cell designCheck cell coverageCheck STSCheck configuration

15 October, 2001 29

yes

no

yes

no

On all TRX?

yes

noNo alarm

?

High drop on particular

TRX?

Disable frequency hopping

Hardware fault

yes

noSolve?

Frequency retune

no

yes

yes

High drop on all TRX?

Interference on all freqs in all

TRX?

yes

noSolve?

Frequency retuneHardware faultCheck cell designCheck coverageCheck stsCheck configuration

yes

Baseband hopping cell with High dropped call

no

On all but timeslot 0 on non BCCH TRX? Collect more sts and

analysis again

no

yes

Retune BCCH

Solve?

yesOn particular TRX?

Hardware fault

Appendix II – Per TRX Drop call analysis for cell using Baseband Hopping

15 October, 2001 30

Documents

52479642 Performance Analysis Per Transceiver Basis