3g Inteference Test and Solution Report

Document Category Radio Equipment Trial Information Category 3G Uplink inteference

mitigation filter test

Development Status Final Document Owner Radio Planning

3G Uplink

Interference and

Solution Report




CONTENTS

1 OBJECTIVE..................................................................................................................... 3

2 EXECUTIVE SUMMARY.............................................................................................. 3 2.1 TYPES OF INTEFERENCE ...............................................................................................4

3 TOOLS ............................................................................................................................. 4

4 TEST DETAILS BY HUAWEI. ...................................................................................... 4 4.1 TEST PROCEDURES ........................................................................................................4 4.2 OBSERVATION..................................................................................................................5 4.3 RECOMMENDED SOLUTION ...........................................................................................6

5 TEST DETAILS BY ERICSSON .................................................................................... 6 5.1 METHODOLOGY ...............................................................................................................7 5.2 PROCEDURE.....................................................................................................................7 5.3 OBSERVATION & SOLUTION...........................................................................................8

6 RECOMMENDATION.................................................................................................... 9




1 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.

2 EXECUTIVE SUMMARY

Spectrum Assignment in Nigeria

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.

1960

1970 1880 1890

BS

1950 10MHz

Celtel Up Celtel Down

10MHz

1960

10MHz

2150 10MHz 2140

CDMA

operator Down

CDMA

operator Up




2.1 TYPES OF INTEFERENCE

There are three types of interferences between CDMA1900 downlink and

UMTS2100 uplink.

� Spurious emission

� Blocking

� Intermodulation.

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 Expected result

1. Collect all the sectors’ RTWP (Received total wideband

power) without any filter and select a sector which is suffering




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

2、Install Celtel WCDMA receive filter on selected sector and

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.

10、Change to another antenna of same sectors.

11、Repeat steps 5 to 9.

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 from Uplink

interference the RTWP < -102dBm. 32 sectors out of the 72 sectors tested failed 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 of interference is the blocking from Starcomms’

CDMA sites.




The effect of installing filters(RTWP_M)

-120

-100

-80

-60

-40

-20

0

1 51 101 151 201 251 301 351 401 451 501 551 601

Samples

RTWP(dBm)

Without filters

With WCDMA Filter

With CDMA Filter

With both filters

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

4.3 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.

Case Average RTWP

Without filter -80.9dBm

With WCDMA filter -101.7dBm

With CDMA filter -82.9dBm

With both filter -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 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 identified using the Huawei

RTWP tool.

5 TEST DETAILS BY ERICSSON

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




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.

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.

� Connect the Spectrum analyzer to the Car charging system

� Set the date and time to current date and time

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

� Set the Noise floor to -102dBm.

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

� Set the sweep time to 10ms

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

� Drive around each operational site and save the RTWP for each site in the

memory of the Spectrum analyzer.

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

analysis.




5.3 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




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 (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 year 1 rollout in 13 states of Nigeria as shown below:




State Planned sites Starcomm's Presence

ABIA 9 YES

ANAMBRA 12 YES

CROSS-

RIVERS 9

Planned for 2008

DELTA 31 Planned for 2008

EDO 24 Towards Q4, 2007

ENUGU 8 No Known Plan

FCT 24 YES

IMO 12 No Known Plan

KADUNA 19 YES

KANO 34 YES

LAGOS 127 YES

RIVERS 30 YES

Grand Total 339

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. 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.

Documents

3g Inteference Test and Solution Report