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Solutions to Solve Poor Coverage Problem in GSM-R Project

Publication Date:  2016-07-01 Views:  552 Downloads:  0
Issue Description

Poor coverage problem

  The reasons of poor coverage between Iren and Olif

Ø  The distance between Iren and Olifantsfontein stations is about 10.3km.

Ø  Large altitude gradient from Iren to Olif.

Ø  Too many tall and dense trees along the railway lines.

Ø   Sloping geographical terrain resulting in a low-lying pathway in this area.

However, several antennas and parameters optimization modifications have been done to improve the poor coverage in the above area but poor coverage still exists. Therefore, deep adjustments like changing antennas and applying PBT (power boost technology) have been planned; and even adding a new build station is considered to solve the poor coverage problem.

Solution

Static coverage testing for new station

Generally, a new station should be built in between of Iren and Olif stations. However, there are many other problems that should be taken into consideration. For example, power supply, bunker fencing, and so on.  

To obtain an optimal coverage in this area, static coverage testing was carried-out between Pine and Olif as shown below.

We selected 6 points at random to test the Rx level. The results show  that Test 2 and Test 4 are mainly poor coverage area.

Test point

Longitude

Latitude

Altitude (m)

Average

Rx level (dBm)

Distance to Poinedene (m)

Distance to Olif (m)

Test 1

Pine

E28.22847°

S25.92954°

1465

BCCH 955-109.67

50

5700

BCCH 972-89.93

Test 2

E28.23288°

S25.92980°

1492

BCCH 955-100.53

1750

3950

BCCH 972-92.69

Test 3

E28.23368°

S25.94119°

1509

BCCH 955-84.14

3000

2700

BCCH 972-97.59

Test 4

E28.23373°

S25.94707°

1515

BCCH 955-100.06

3650

2050

BCCH 972-107.11

Test 5

E28.23178°

S25.95782°

1530

BCCH 955-86.83

4900

800

BCCH 972-102.73

Test 6

(Olif)

E28.23446°

S25.96419°

1538

BCCH 955: -65.35

5700

100

BCCH 972 -110.07

Note:

v  BCCH 955 is the frequency configured on Olifantsfontein BTS

v  BCCH 972 is the frequency configured on IREN BTS

 

l  Test 2, the distance to Iren (BCCH: 972) is about 6.3km while to Olifantsfontein (BCCH: 955) is 4km. However, the Rx level of BCCH: 955 with the shortest distance to Olifantsfontein Station is lower than that of BCCH 972 (IREN Station).

l  Test 4, the Rx level is much lower than test 3 and its location is closer to Olifantsfontein station.

l  From the altitude picture, it shows that Test 2 and Test 4 are both locate in low-lying areas where altitude height changes rapidly. These special areas are having a low Rx level, therefore making it difficult to receive RF signal from Olifantsfontein station.

l  From coverage test result picture below, it shows that the poor coverage areas are near to Olifantsfontein stationso we could pay more attention to it.

 

l  Solution 1: Carry out deep adjustments to Olifantsfontein station

Ø  Increase the antenna gains from 18.2dbi to 21dbi by changing a new antenna.

Ø  Applying PBT (power boost technology). Firstly, we will dismantle the splitter of station; then, complete the configuration parameters work of PBT in BSC.

After finishing solution 1, it is estimated that the Rx level will increase by about 8dBm. Poor coverage situation will be improved a lot; however, if it still fails to meet the EIREN coverage acceptance criteria, solution 2 will be carried out.   

l  Solution 2: Adding a new site between Iren station and Olifantsfontein station.

Ø  Plan 1: new site build at Pine station is about 5.8km away from Olifantsfontein station. Provision of power supply and civil work will be convenient. However, due to low altitude gradient in this area, antenna height of 15m to 20m cannot provide good coverage. In this case, RF signal propagation will lower than plan 2.

Ø  Plan 2: Is about 1.80km away from Pine station and 3.95km to Olifantsfontein station. This location is proposed for good coverage between IREN and OLIFANTSFONTEIN stations due to EIREN requirements of coverage probability of 95% on a coverage level of -95dBm within 100m on the railway lines. It will be advisable to consider Plan 2 that involved the following: delivery time and cost, provision of power supply, provision of bunker and so on.

 

  New station site plan

Google Earth Profile of the proposed site from Pine station

 

Comment: The distance from the Pine station to plan 2 site location is about 1.80km as shown from Google Earth map.

 

The coverage prediction of new site:

Ø  Plan 1 @ Pine station

Comment: The coverage prediction at Pine station @ longitude: E28.22847 & Latitude: S-25.91362 is not good due to the terrain gradient from IREN to Olifantsfontein station. Therefore, a new site built at Pine station will not be recommended.

 

Ø  Plan 2 @ new location (1.80km away from Pine station)

Comment: The new location is about 1.80km away from the Pine station @ longitude: E28.23356 & Latitude: S-25.93115. The coverage prediction at this location is good from IREN to Olifantsfontein station.

 

The surrounding environment of new station.

Ø  Plan 1 site (Pine station)

Pine station is located in a large open area and it has a power supply house.

 

Ø  Plan 2 site (Pine station)

Remarks:

v  No relay building @ plan 2 location

v  No power supply house

v  Bunker will be required

v  Fencing will be required

 

END