GO_NA15_E1_1 GSM Coverage Problem & Solution 19

7/28/2019 GO_NA15_E1_1 GSM Coverage Problem & Solution 19

http://slidepdf.com/reader/full/gona15e11-gsm-coverage-problem-solution-19 1/19

GSM Coverage problem & Solution

ZTE university



Objectives

To know different kinds of coverage problem, their causes and solutions.



Contents

Overview o f Coverage Prob lem

Main Causes of Coverage Problem & Solutions

Procedures of Handling Coverage Problem

Typical Cases



Contents

Overview of Coverage Problem

Main Causes o f Coverage Problem & Solut ions


Typical Cases



Main causes of weak coverage

Weak coverage

too small BTS power

too low antenna height

too small down-tilt

hardware problem

Obstruction of buildings



Main causes of over coverage

too high antenna height

inappropriate down-tilt

poor antenna performance



Causes of no-serving cell coverage

unreasonable planning

of antenna parameters

inappropriate type of antenna

too large or too small

carrier transmission power

shrunk coverage caused

by equipment problem

influence of changes

in radio environment

unreasonable settingof handover parameters

unreasonable setting of

cell reselection parameters

no-serving cell coverage



Contents



Procedures o f Hand l ing Coverage Problem

Typical Cases




Check setting of problem BTS’ radio parameters

Check if strong interference source exists

Check hardware

Check antenna system

Analyze the local geographical environment to

see if site location and type of site are appropriate



Contents




Typ ical Cases



Poor coverage at cold storage warehouse

【Problem description】

Subscribers complained about the poor coverage around a cold storagewarehouse of animal foodstuff; it was difficult to detect signal even whenthey were not far from the warehouse.

【Problem analysis】

According to subscriber’s complaint, we confirmed there was problem with

coverage around the warehouse. We found all radio parameters of the sitewere set correct at OMCR. Statistical report showed that idle data of interference band and UL/DL quality data distribution were normal.Hardware operated normally, as shown in OMCR warning report.

Hardware engineers went to the site and checked the system of the BTS,tested power amplifier's power and VSWR, they were all shown normal.Connection between equipment was correct. Antenna azimuth and down-tilt were all set reasonable.

Through DT on site, network engineers found that the signal strength of the antenna main lobe was weak, while that of the side lobes wasstronger, so they tentatively confirmed the problem was due to antennafault.



Poor coverage at cold storage warehouse

【Problem handling】 After the antenna was replaced with a new one, the coverage improved

greatly, so did the speech quality.



Poor coverage of a BTS

【Problem description】 Subscribers complained about weak signal strength around a Food

Bureau (near a BTS).

【Problem analysis】 According to subscriber’s complaint, we confirmed there was

problem with the BTS' coverage. We found all radio parameters of

the site were set correct at OMCR. Statistical report showed thatidle data of interference band and UL/DL quality distribution werenormal. Hardware operated normally, as shown in OMCR warningreport.

Hardware engineers went to the site and checked the system of theBTS, tested amplifier's power and VSWR, they were all shownnormal. Connection between equipment was correct. Antennaazimuth and down-tilt were all set reasonable.

Through DT on site, network optimization engineers found that theBTS’ coverage was in normal condition. While the Food Bureau,where subscribers complained about the signal, was 4km awayfrom the BTS, and only indoor signal was weak (covered by Cell2).



Coverage shrinking after BTS starts operation

【Problem description】 After Cell3 of a BTS started to operate, its coverage range was

found shrunk. On highway 3km away from the BTS, where the BTS

tower was visible, MS could not detect Cell3’s signal. MS could

receive signal when it’s around the BTS, and the signal level was

about -60dB. 【Problem analysis】

We checked in radio resource management centre and found

Cell3’s static power class was set 2, which meant its static power

was reduced by 4dB, so we reset it to be 0. The next day, MS on

highway 3km away from the BTS could receive Cell3’s signal, andits level was -60—70; and the signal level around the BTS was

strong, which was about -40dB.

we concluded that the cell’s coverage shrinking was caused by

wrong setting of static power control at OMCR.



High handover failure rate due to skip-zone

coverage 【Problem description】

Configuration of a mountain site was S11, and the local network wassingle band GSM900. From indicator statistics of the past week, we foundhandover success rate of Cell2 under the BTS kept very low, which wasaround 80%, while TCH allocation failure rate was completely normal.

【Problem analysis】 First, we could exclude the possibility of hardware problem and

interference, because there were no TCH assignment failures, whichexplained that MS could successfully occupy TCHs assigned to it by BSC;from DT analysis, we could see when signal level was above -90dbm, nocall drops happened to MS, and speech quality was good, which couldprove that no serious interference existed. Through further analysis, wefound the target cell for handover was a bit far from Cell2; and probablyadjacent cell relations were not set right during assignment planning,which resulted in isolated-island effect.

we could make area A and area B become adjacent cells to Cell2; whileCell2 coverage at A and B was already very weak, so Cell2 should not beadjacent cell to A and B .

After adjustment, handover success rate of Cell2 increased greatly, from80% to 96%.



High handover failure rate due to skip-zone

coverage

Cell2

Cell1



Questions for thinking

Which parameters can be adjusted to improvecoverage?

GO_NA15_E1_1 GSM Coverage Problem & Solution 19

Documents

Transcript of GO_NA15_E1_1 GSM Coverage Problem & Solution 19