3g Inteference Test and Solution Report

 

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Radio Equipment Trial

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Final

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3G Uplink inteference mitigation filter test Radio Planning

3G Uplink Interference and Solution Report

 

  Document Category

Radio Equipment Trial

Information Category

Development Status

Final

Document Owner

3G Uplink inteference mitigation filter test Radio Planning

CONTENTS 1  2 

2.1 

3  4 

4.1  4.2  4.3 

5 

5.1  5.2  5.3 

6 

OBJECTIVE ............................................................................................................ OBJECTIVE..................................................... ................................................................ ......... 3  EXECUTIVE SUMMARY ................................................ .............................................................................................. .............................................. 3  TYPES OF INTEFERE INTEFERENCE NCE ................... ............................ .................. .................. .................. ................... ................... ................. ................. ............. ....4 4  TOOLS ........................................................................................................... ................................................... .......................................................................... .................. 4  TEST DETAILS BY HUAWEI. ...................................................................................... .................................................. .................................... 4  TEST PROCEDURES ............... ................................ .................................... .................................... .................................. .................................... ................... 4  OBSERVATION..................................................................................................................5   RECOMMENDED RECOMME NDED SOLUTION ......... .................. .................. .................. .................. .................. ................... ................... .................. ................. .......... 6  TEST DETAILS BY ERICSSON ................................................ .................................................................................... .................................... 6  METHODOLOGY METHODOL OGY .................. ........................... ................... .................. ................. ................... ................... .................. .................. .................. .................. ........... .. 7  PROCEDURE.....................................................................................................................7   OBSERVATION & SOLUTION...........................................................................................8  RECOMMENDATION.................................................................................. RECOMMENDATION........................... ......................................................................... .................. 9 

 

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1

3G Uplink inteference mitigation filter test Radio Planning

OBJECTIVE

  Confirm the level of inteference on the UL spectrum of the allocated Band D (1950 MHz – 1960MHz) spectrum granted to Celtel Nigeria. The test was conducted by Celtel’s two major vendors for 3G, they are:   Messrs Huawei Technologies Ltd conducted test Port-Harcourt, South South region.   Messrs Ericsson conducted test in Lagos, Lagos Region.

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2

EXECUTIVE SUMMARY Spectrum Assignment in Nigeria

CDMA operator Down

CDMA operator Up 1880

1890

1960

10MHz

BS 1970

10MHz Celtel Up

1950

Celtel Down

1960

2140

10MHz

10MHz

Figure 1: Spectrum Assignment of Celtel and CDMA operator  NCC had assigned 1950~1960MHz to Celtel UMTS Rx band, while 1960~1970MHz has already been assigned to Starcomms CDMA Tx band. Interference possibility exists between CDMA Downlink and UMTS uplink because the two frequency  bands are very close to each other.

2150

 

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2.1

3G Uplink inteference mitigation filter test Radio Planning

TYPES OF INTEFERENCE

There are three types of interferences between CDMA1900 downlink and UMTS2100 uplink.   Spurious emission 

  Blocking   Intermodulation.

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3

TOOLS

•  R&S FSH3 spectrum Analyzer. •  TEMS Drive test kit. •  Vendors’ (Huawei and Ericsson) Network statistics monitoring tools.

4

TEST DETAILS BY HUAWEI.

Huawei conducted the Interference test in Port-Harcourt where twenty four 3G sites are operational. The test procedure is shown below

4.1

TEST PROCEDURES

Objective

The test purpose is to verify if it can solve the interferences between Starcomms CDMA downlink and the Celtel WCDMA uplink after installing filters on both Starcomms sites and Celtel sites.  Test network figure

Prerequisites

The tested WCDMA site works normally. Procedure

1. Collect all the sectors’ RTWP (Received total wideband  power) without any an y filter and select a sector which is suffering

Expected result 

 

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3G Uplink inteference mitigation filter test Radio Planning

serious interference (RTWP>-90dBm) to test. 2

Install Celtel WCDMA receive filter on selected sector and

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then collect RTWP again. 3 Uninstall Celtel WCDMA receive filter and install CDMA transmit filter on the selected sector, then collect RTWP. 、

4 Install both WCDMA receive filter and CDMA transmit filter on selected sector and then collect RTWP. 、

5 Connect YBT250 to the tested sectors antenna without any filter. 、

6 Set YBT250 span range from 1920~1970MHz and record the result (save the spectrum figure). 、

7 Set YBT250 span range from 1950~1960MHz and record the result (save the spectrum figure). 、

8 Connect WCDMA receive filter on YBT250 and then connect selected sector antenna to filter. 、

9

Repeat steps 5 and 7.

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10

Change to another antenna of same sectors.

11

Repeat steps 5 to 9.

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Remarks

In this test, CDMA filter be installed on WCDMA sector (in real network, it should be installed on Starcomms CDMA site), but the effect is the same because of the filter is still on the same link.

4.2

OBSERVATION

Test was carried out using the RTWP (Received Total Wideband Power) measurement function of the Huawei Node B for all 72 sectors. For a sector to be free free from Uplink interference the RTWP < -102dBm. -102dBm. 32 sectors out of the 72 sectors tested fail failed ed this test. Therefore, Huawei used the above procedure to treat the affected cells using the designed filter and the Uplink interference was observed to have been eliminated for the affected site. An indication that the major source so urce of interference is the blocking from Starcomms’ CDMA sites.

 

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3G Uplink inteference mitigation filter test Radio Planning

The effect of installing filters(RTWP_M) 0

Without filters

-20

With WCDMA Filter With CDMA Filter

       )     m       B       d        (       P       W       T       R

-40

With both filters

-60 -80 -100 -120 1

51

10 1

1 51

2 01

2 51

3 01

351

401

451

50 1

55 1

Samples

Figure 2 The effect e ffect of installing filters (RI007_1, RTWP_M)

4.3

6 01

 

RECOMMENDED SOLUTION

In order to solve interference, Celtel needs to install filters on the affected site. The filter tested during the trial has a 40dB attenuation range and the results are shown  below..  below

Case Without filter With WCDMA filter With CDMA filter With both filter

Average RTWP -80.9dBm -101.7dBm -82.9dBm -105.6dBm

Figure 3 the effect of installing filters (RI007_1, RTWP_M) With the expected growth of Celtel 3G network as well as the expansion of the Starcomms network whose sites are potential po tential interferers to Celtel’s WCDMA sites. Huawei has recommended that 50% of WCDMA sites will need a filter to eliminate the Uplink interference. However, the specific sites will be b e identified using the Huawei RTWP tool.

5

TEST DETAILS BY ERICSSON

Ericsson conducted the Interference test in Lagos. The test procedure is shown below

 

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3G Uplink inteference mitigation filter test Radio Planning

5.1 METHODOLOGY Some sites were identified.   Record traces of the uplink (1950 – 1960 MHz) at identified site using R&S FSH3 spectrum Analyzer and taking a snap-shot of the graph.   Collect statistics for a period of 3 hours in the day. 

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5.2

PROCEDURE

A spectrum analyzer was connected to an Omni antenna to scan measurement for the uplink on a frequency range of 1920MHz to 1967MHz for us to get all the active  bandwidth before and after the bandwidth of 1950 MHz - 1960 MHz given to Celtel  Nigeria. 

  Identify all sites to be tested as well as their addresses.   Power on the Spectrum analyzer.

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  Connect the Spectrum analyzer to the Car charging system

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  Set the date and time to current date and time

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  Set the start Frequency to 1920 MHz and Stop frequency to 1967 MHz.

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  Set the Noise floor to -102dBm.

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  Connect the Omni antenna to the RF input port of the Spectrum Analyzer.

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  Set the sweep time to 10ms

  Check to ensure that the equipment is working normally and setup is complete.

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  Drive around each operational site and save the RTWP for each site in the memory of the Spectrum analyzer.

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  After all sites RTWP has been saved; download the file for observation and analysis.

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5.3

3G Uplink inteference mitigation filter test Radio Planning

OBSERVATION OBSERVATION & SOLUTION

With the UL interference statistics, it can be seen that some cells experienced some interference, which might have been caused by spurious emissions or blocking interference from other parties as shown in the figure below.

Figure 4 Spectrum from 1950 to 1960 without filter

 

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3G Uplink inteference mitigation filter test Radio Planning

Figure 5 Spectrum from 1950 to 1960 with filter Statistics was also collected on the network monitoring tool shows indication of interference in some sites. The installation of the Test filters reduced the level of interference. Based on the above results and observations, conclusion was drawn that there is some form of interference on the Uplink for certain 3G sites. We recommend that Celtel plan for about 35% of the 3G sites to require filters. This is required as a safe-guard measure for those sites that may experience interference. The other recommendation is to avoid direct line of sight with the CDMA operational sites on future installations.

6

RECOMMENDATION.

Based on the finding during the interference test the following is recommended:

1. The blocking effect of Starcomms sites on the Celtel’s 3G sites to be reported to the regulatory body – Nigerian communication Commission Commiss ion (NCC) for record purpose and  perhaps a regulatory action may emanate by reallocating frequencies to CDMA operators to finally eliminate the blocking interference. 2. 339 sites are planned for the 3G y year ear 1 rollout in in 13 states of Nigeria as shown below:

 

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State

Planned sites 9 12

3G Uplink inteference mitigation filter test Radio Planning

Starcomm's Presence

ABIA ANAMBRA CROSSRIVERS DELTA EDO ENUGU FCT IMO KADUNA KANO LAGOS

YES YES Planned for 2008

9 31 24 8 24 12 19 34 127

Planned for 2008 Towards Q4, 2007 No Known Plan YES No Known Plan YES YES YES

RIVERS Grand Total

30 339

YES

Since Starcomms is not stopping rollout and we do not know where next (citiy) they will rollout new sites, coupled with the fact that NCC is not indicating withdrawing the 1960MHz – 1970 MHz from Starcomms. It is recommended we install the tested filters on all 3G sites. For future 3G deployment in all cities; 3G Equipment Vendors should be instructed to install the tested filter for all Node Bs. Bs . These filter need to be acquired as soon as possible before the 3G commercial launch to improve the quality of service to our potential 3G subscribers.