GPRS DT Analyse and Case

8/4/2019 GPRS DT Analyse and Case

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GPRS DT ANALYSE AND CASE

KEY WORDS:

GPRS DT, SYSTEM INFORMATION, CELL RESELECTION

ABSTRACT:

This report summarizes all kinds of problems in GPRS DT and corresponding methods to

solving them. And it gives more detailed analyze and related cases.


2/21

CATALOG

SYSTEM INFORMATION 2Ter ........................................................................................3

RESOURCE NOT ENOUGH .............................................................................................5MEASUREMENT FREQUENCY LACK ..........................................................................7

CELL RESELECTION OPTIMIZING (A) .........................................................................8

CELL RESELECTION OPTIMIZING (B) .......................................................................10

UPLINK INTERFERENCE TO DATA TRANSFER ...................................................... 11

TEST EQUIPMENT CAUSE ............................................................................................13

FREQUENCY INTERFERENCE .....................................................................................15

NEW SITE IMPROVE COVERAGE ...............................................................................16

MODIFY ANTENNA TO COVER .................................................................................. 19

GPRS FEATURE DISABLE ............................................................................................ 21


3/21

SYSTEM INFORMATION 2Ter

QUESTION

The signal strength and quality in cell A (900M) is poorer and poorer. When MS

moves in opposite direction, the signal strength and quality in cell B (1800M) is

very good. But at this time, MS could not occupies cell B, even C1 and C2 value

of cell B do not exist in TEMS C1 and C2 Chart.

ANALYSING

We could find MS receives System Information 13 before getting system

information 2 ter. So MS requests channel and gets corresponding channel for

data transfer in cell A. MS could not select cell B with strong signal strength and

good quality because of the lost of 1800M neighboring cell ARFCN.

Related explanation in GSM specification below.

METHOD


4/21

Strengthening signal coverage of both 900M and 1800M synchronously, which

could ensure the strong signal strength, good quality and high speed of data

transfer when not receiving System Information 2ter.


5/21

RESOURCE NOT ENOUGH

QUESTION

The data speed transfers slowly when MS reselect to one cell.

ANALYSING

After reselect to this cell, MS only gets 2 PDCHs. When gets 3 PDCHs, two

users share these 3 PDCHs. Data transfers slowly. The layer 3 signaling figure is

shown below.


6/21

This cell exists serious congestion through STS and the number of PDCH

establish failure, PDCH preempt and TBF release are more somewhat. So the

resource of this cell is not enough.

METHOD

The resource need to be increase. The speed of data transfer improves after the

number of frequency carriers is increased. The comparison figures are shown

below.


7/21

MEASUREMENT FREQUENCY LACK

QUESTION

In one road, both signal strength and quality are very poor, and speed of data

transfer is low. The cell reselection queue should be A->B->Cstrongest signal

strength->D->E in the first DT test. But the queue is A->F->E in this DT test.

ANALYSING

After the fist test, the CRO of cell B is changed from 8 to 5, which result in no

reselection from cell A to cell B. But the signal strength of cell B is not the

strongest, and cell C is the best selection through the first DT log.

The MS does not reselect from cell A to C because of relation lack between cell

A and C. And measurement frequency is not added in idle mode list of cell A.

METHOD

Adding measurement frequency of cell C to cell A in idle mode. Even the relation

between the two cells could be ignored.

The signal strength and quality of this road is improved after adding

measurement frequency of cell A in idle mode. The comparison figures are

shown below.


8/21

CELL RESELECTION OPTIMIZING (A)

QUESTION

In one road, the cell reselection is so fast and frequent, which results in low data

transfer.

ANALYZING

The cell reselection queue is A->B->A->C. After reselection from cell B to A, the

signal strength in cell A is very poor and data transfer stopped nearly. The signal

strength in cell C is strong, but cell B is not reselect to C, because the ACCMIN

98 and CRO 8 in cell B give cell B a too big coverage in idle mode.

METHOD

Modify ACCMIN in cell B from 98 to 94 and CRO from 8 to 4. The possibility of

selection to cell B is decreased and corresponding C is increased. The signal

strength and quality of Cell A and C is good compared to B.

The cell reselection in the first DT test is A->B->A->C.

The queue in the second DT test is A->C.


9/21

The cell selection is from cell A to C directly and cell B is not be added. The

number of cell reselection is decreased from 4 to 2. The data transfer is improved

therefore. The effect of the second DT test is shown below.


10/21

CELL RESELECTION OPTIMIZING (B)

QUESTION

In this road, the cell reselection is from cell A to B directly. But the signal strength

is very poor in cell A when reselection happens.

ANALYZING

When cell A reselects to B, the signal strength is very poor. Considering cell C

should be transition cell between cell A and B.

METHOD

Modify CRO in cell A from 6 to 4 and CRO in cell C from 0 to 4, which result

in cell reselection queue A->C-> B.


11/21

UPLINK INTERFERENCE TO DATA TRANSFER

QUESTION

After cell reselection to cell A, data transfer is poor.

ANALYZING

The uplink interference of cell A impacts quality in air-interface. The uplink

interference in STS is shown below.CELL DATE PERIOD NOACCUF ITFUSIB1 ITFUSIB2 ITFUSIB3 ITFUSIB4 ITFUSIB5

A 060825 0000-0100 360 889 40 1175 9963 1928

A 060825 0100-0200 360 1536 1456 5886 5752 206

A 060825 0200-0300 360 2316 3405 6293 3144 48

A 060825 0300-0400 360 3432 4806 5039 1138 13

A 060825 0400-0500 360 3912 5227 5142 1050 11

A 060825 0500-0600 360 6646 4504 3126 919 12

A 060825 0600-0700 360 3525 1877 3338 5082 503

A 060825 0700-0800 360 663 224 2087 7916 1265

A 060825 0800-0900 360 99 106 1013 4178 334

A 060825 0900-1000 360 68 13 34 5338 1505

A 060825 1000-1100 360 59 29 12 1198 2583A 060825 1100-1200 360 214 85 731 4183 688

A 060825 1200-1300 360 89 12 24 2585 3309

A 060825 1300-1400 360 100 75 385 3257 1896

A 060825 1400-1500 360 372 41 94 1680 1179

A 060825 1500-1600 360 122 11 71 987 1884

A 060825 1600-1700 360 109 9 17 744 2341

A 060825 1700-1800 360 182 26 13 418 2482


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A 060825 2000-2100 360 58 6 195 3063 2273

A 060825 2100-2200 360 94 15 188 5158 1689

A 060825 2200-2300 360 208 429 2188 5913 690

A 060825 2300-0000 360 7260 602 1788 2423 77

METHOD

Modify CRO in cell A from 5 to 0 to avoid to reselect to this cell.


13/21

TEST EQUIPMENT CAUSE

QUESTION

The signal strength and quality are very good, but the data transfer is not perfect.

ANALYZING

The operating system in test PC that day is E/// ESOE which sends special

network information on time. When MS reselects to cell A, the PC sends a series

of query indication to network side, which impacts the normal FTP download.

The abnormal indication is shown below through Ethereal software.


14/21


15/21

FREQUENCY INTERFERENCE

QUESTION

After selecting cell A, the speed of data transfer is changed poor.

ANALYZING

C/I is so low in cell A. It is the most important reason to poor data transfer.

MOTHED

The C/I of frequency 23 and 65 is the lowest, modifying 23 65 -- > 12 60. The

data transfer speed is improved. The comparison figures are shown below.

BEFORE AFTER


16/21

NEW SITE IMPROVE COVERAGE

QUESTION

The signal strength of some cells covering one road is less than or equal to

-80dBm, and the corresponding quality is changed to poor.

ANALYING

In this road, the signal strength of every cell is very low. So the coverage is not

so good to this road. The DT chart is shown below.

At the same time, the serious bit error rate could be seen in the layer 3 sheet of

TEMS Investigation. Abundant data retransmissions take place and data transfer

is interrupt usually. Related error bit is shown below.


17/21

There are many high resident buildings around this road. Some signal from micro

cellular leaks to the road, but it should be avoided and can not cover the whole

road. The below figure shows the low signal strength road, serving cell and micro

cells around.


18/21

METHOD

Advise to add new site in order to cover this road well.


19/21

MODIFY ANTENNA TO COVER

QUESTION

One site consists of 1800M and 900M, no cover by 1800M to its west direction

road.

ANALYZING

In the first test, MS selects this cell, but does not receive System Information

2Ter. So MS measures 1800M frequency only, and signal strength and quality is

changed poor when it moves from this site to the west direction because the MS

could not measure 900M frequency. Eventually data transfer is stopped. The DT

figure is shown below.

METHOD

Modify antenna angle from 60 to 90.

In the test later, signal strength of 1800M is improved and MS selects 900M cells

more easily. The DT figure is shown below.


20/21


21/21

GPRS FEATURE DISABLE

QUESTION

In some tests e.g. airport road, the FTP download and GPRS attach could both

not be operated effectively.

ANALYZING

This kind of problem took place hardly. Radio parameter and BSC parameter are

correct through careful check. No abnormal problems are found.

METHOD

Finally restarting cell GPRS feature solves this problem using RLGSE and

RLGSI commands. FTP data transfer is performed normally. This method is

produced through test, so problem should take place in HW or SW feature usage

and maintenance.

GPRS DT Analyse and Case

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