High RTWP level in Huawei UMTS network

[lpkojihu]

Dear colleagues,

We experiencing exceptionally high level for RTWP measurements for many cells in Huawei UMTS network. Such level (-85....-75dBm) can not be explained by regular interference caused by mobile phones. This is a new UMTS network with very low traffic.
Spectrum analyzer measurements did not show any external interference sources. Typically measured RTWP with spectrum analyzer is around -110dBm

Event measurements through UMTS cell antenna shows -110dBm level.

Only when RRU unit is in operation the measured RTWP jumps to -80dBm.

GSM and UMTS networks are fully separated and isolated, i.e. separate antennae used and they are space separated and only single carrier used in UMTS - this excludes any source of Intermodulation cause.

The only problem that I can raise is a problem with RRUs. There are ~30% of cells are suffering from constant high RTWP level and 70% of cell suffering from peak levels of RTWP.

Please, assist with possible solution. Or you may know if some issues with new generation of the Huawei UMTS equipment.

Best regards

[bindi]

If you have already checked with spectrum analyzer and ruled out external interference, then it clearly looks like hardware issues. May be it was a particular batch of faulty hardware (RRU/MHAs etc), or even commissioning file may be. Check settings, in the comm file or if there are any switches needed to be set in node B for this.

[mobilink999]

Are you using TMA ??? whats attenuation setting??

use lst rxatten in MML and share with us.

[aly280779]

Hi,
Have you already checked if there is any cross sector? Because if it is the case you must correct it first. Check also neighboor declaration.

[D33T0X]

Are the RTWP levels constantly high? If yes then you have hardware issue. If the high RTWP levels come and go - that can be external interference.

[mdiazd]

The possible cause is the frequency of GSM carry, This generated intermodulation in you Reception of UMTS. The receiver are superheterodine circuit, and down convertion used a mutilplier, the multiplier generates harmonics that fall in the uplink Umts Carry.

You need set The GSM carry in other frequency, so that the intermodulation is out band the uplink UMTS carry .

[romagdinio]

which RNC software are you using RAN 10? and which SPC?

[sonerss]

Hi

Have you ever change the RRU?? It looks like a Hw problem.. Maybe you can control vswr values each fiders

BR


Dear colleagues,

We experiencing exceptionally high level for RTWP measurements for many cells in Huawei UMTS network. Such level (-85....-75dBm) can not be explained by regular interference caused by mobile phones. This is a new UMTS network with very low traffic.
Spectrum analyzer measurements did not show any external interference sources. Typically measured RTWP with spectrum analyzer is around -110dBm

Event measurements through UMTS cell antenna shows -110dBm level.

Only when RRU unit is in operation the measured RTWP jumps to -80dBm.

GSM and UMTS networks are fully separated and isolated, i.e. separate antennae used and they are space separated and only single carrier used in UMTS - this excludes any source of Intermodulation cause.

The only problem that I can raise is a problem with RRUs. There are ~30% of cells are suffering from constant high RTWP level and 70% of cell suffering from peak levels of RTWP.

Please, assist with possible solution. Or you may know if some issues with new generation of the Huawei UMTS equipment.

Best regards

[patek1968]

RTWP is caused by faulty hardware or loosed cables that weren't properly terminated..if its HW you can check in m2000 for the RTWP value and therefore can address this to their PM..

[danikd]

We have a similar problem in our Huawei network....we could not not find any external interference. The high RTWP appears only when RRU connected to the antenna. RRU replacement did not solve the problem, even UL frequency change did not show improvement.
Any thoughts about RRU performance? Any trouble tickets open?
Huawei told us just install filters, but I do not understand how it can solve a problem, since nothing appears on UL channel in the air.


Dear colleagues,

We experiencing exceptionally high level for RTWP measurements for many cells in Huawei UMTS network. Such level (-85....-75dBm) can not be explained by regular interference caused by mobile phones. This is a new UMTS network with very low traffic.
Spectrum analyzer measurements did not show any external interference sources. Typically measured RTWP with spectrum analyzer is around -110dBm

Event measurements through UMTS cell antenna shows -110dBm level.

Only when RRU unit is in operation the measured RTWP jumps to -80dBm.

GSM and UMTS networks are fully separated and isolated, i.e. separate antennae used and they are space separated and only single carrier used in UMTS - this excludes any source of Intermodulation cause.

The only problem that I can raise is a problem with RRUs. There are ~30% of cells are suffering from constant high RTWP level and 70% of cell suffering from peak levels of RTWP.

Please, assist with possible solution. Or you may know if some issues with new generation of the Huawei UMTS equipment.

Best regards

[soodlhor]

If like this, we can try to shut down GSM cell for testing.


The possible cause is the frequency of GSM carry, This generated intermodulation in you Reception of UMTS. The receiver are superheterodine circuit, and down convertion used a mutilplier, the multiplier generates harmonics that fall in the uplink Umts Carry.

You need set The GSM carry in other frequency, so that the intermodulation is out band the uplink UMTS carry .

[danikd]

If like this, we can try to shut down GSM cell for testing.

But GSM and UMTS are fully separated different cables/antennas/heights.

How it can create any Intermodulation?

[danikd]

But GSM and UMTS are fully separated different cables/antennas/heights.

How it can create any Intermodulation?

BTW, we've shift UL UARFCN for 10 MHz....the problem is still there.

[fahmi]

Hi,
I am facing the same problem with our huawei network, specially in UMTS 900.
I am doubting that there is interference with GSM.
or it may be a huawei hardware problem since all of us work with the same equipment and face the same problem !!

[electron]

Since it is affected on several site and your network in new which it means you are in roll out phase i think it can be some problem in hardware. As all friends suggested some check for RRU as first step lets do it and another thing that i had experienced can be because of ASC misconfiguration lets check status of ASC for each site .

Thanks

[danikd]

Since it is affected on several site and your network in new which it means you are in roll out phase i think it can be some problem in hardware. As all friends suggested some check for RRU as first step lets do it and another thing that i had experienced can be because of ASC misconfiguration lets check status of ASC for each site .

Thanks

can you please, elaborate on this issue? what to check on ASC?

[electron]

can you please, elaborate on this issue? what to check on ASC?

Actually ASC is Antenna Support device in E/// RNC you can check in from RNC with "st ASC" command in moshell in Huawei maybe experienced members can help you

[fangruan2201]

Dear colleagues,

We experiencing exceptionally high level for RTWP measurements for many cells in Huawei UMTS network. Such level (-85....-75dBm) can not be explained by regular interference caused by mobile phones. This is a new UMTS network with very low traffic.
Spectrum analyzer measurements did not show any external interference sources. Typically measured RTWP with spectrum analyzer is around -110dBm

Event measurements through UMTS cell antenna shows -110dBm level.

Only when RRU unit is in operation the measured RTWP jumps to -80dBm.

GSM and UMTS networks are fully separated and isolated, i.e. separate antennae used and they are space separated and only single carrier used in UMTS - this excludes any source of Intermodulation cause.

The only problem that I can raise is a problem with RRUs. There are ~30% of cells are suffering from constant high RTWP level and 70% of cell suffering from peak levels of RTWP.

Please, assist with possible solution. Or you may know if some issues with new generation of the Huawei UMTS equipment.

Best regards

Hi,

It is very easy. I guess your network use Agison (HuaWei) antenna.:D

Try to decrease the CPICH power u will see RTWP DECREASE ALSO.

This is due to poor antenna's material. Remember to buy good antenna: Katherein, Andrew or even Tonguy.

Cheer!

[danikd]

Hi,

It is very easy. I guess your network use Agison (HuaWei) antenna.:D

Try to decrease the CPICH power u will see RTWP DECREASE ALSO.

This is due to poor antenna's material. Remember to buy good antenna: Katherein, Andrew or even Tonguy.

Cheer!

Good try, but all antennas are Kathrein, last year model, tested for PIM (Passive Inter Modulation) and found good.

Single carrier operation, so Intermodulation is not possible, GSM is operating with different antennae, with space separation.

[entorresa]

In one cell site with high RTWP connect the spectrum analyzer to the cell site antena. Check the noise level. Turn off your 3G base station and check again your noise level.

If your 3G site are turn off you noise level should be low if not you have an external interference.

If you have external interference use the spectrum analyzer to meter the noise in 360°, take note where you found the high noise value. Do the same in at least 3 cell sites with high RTWP.

With this information and using triangulation you can discover where is the source of interference.

[agenov]

Dear colleagues,

We experiencing exceptionally high level for RTWP measurements for many cells in Huawei UMTS network. Such level (-85....-75dBm) can not be explained by regular interference caused by mobile phones. This is a new UMTS network with very low traffic.
Spectrum analyzer measurements did not show any external interference sources. Typically measured RTWP with spectrum analyzer is around -110dBm

Event measurements through UMTS cell antenna shows -110dBm level.

Only when RRU unit is in operation the measured RTWP jumps to -80dBm.

GSM and UMTS networks are fully separated and isolated, i.e. separate antennae used and they are space separated and only single carrier used in UMTS - this excludes any source of Intermodulation cause.

The only problem that I can raise is a problem with RRUs. There are ~30% of cells are suffering from constant high RTWP level and 70% of cell suffering from peak levels of RTWP.

Please, assist with possible solution. Or you may know if some issues with new generation of the Huawei UMTS equipment.

Best regards

Hi,

Can you share how you cope with the case? I am curious to find out how you solved the issue and what was the problem?

Thanks.

Alex

[rf_eng]

try to find external interferers!
I suggest drive testes with spectrum analyzer in neighbourhood. The most affected sector will tell you the direction.
It can be remote repeater installed at private office, damaged television ampliifer, some wireless CATV systems.
Remember that RRU is very sensitive and you have to operate with spectrum analyzer very carefully to find external problems.
In my career I have met some repeater which were causing very high RTWP even 2/3km from site!
If feeder, jumper antenna connection is OK I think. there is no other option..

[nimopaul]

Generally External interferance will have varying levels over time. Try re-orienting the antenna. Issue persists? Then try swapping the sector by swapping the cable. If it is external interferance, issue will persist in antenna facing old direction.
If it's H/w issue, after cable swap, the issue will also get swaped. i.e it will report pseudo interferance from new direction also.

Also see if the RTWP is constant through out. If yes, it could be h/s issue.

R's
Nimo

[Philippe]

Could you tell if the problem occurred on a specific Huawei product? I mean e.g. RRU at 850MHz or 900MHz or 2100MHz? which hardware and software release?

[b0r3l_1]

Hi

We experience same issues in our UMTS 850 last year, what we did is to replace the jumper cables and have it secure fit.

[rejreyes]

Was monitored as well with Huawei UMTS 2100 project here in the Philippines. Installation issues can be a culprit and external interference too as well. But as was noticed by the engineers, it was due to internal interference; never explained thoroughly though...

[jimjim]

Hi

We experience same issues in our UMTS 850 last year, what we did is to replace the jumper cables and have it secure fit.


Hello there,

Would you kindly give more explanation on the type of jumper cables that caused this interference? Was the fault in installation or type? What was the new type of cable jumpers you used?

:)
Regards,

[Philippe]

Hi

We experience same issues in our UMTS 850 last year, what we did is to replace the jumper cables and have it secure fit.

Only jumper problem? no RRU hardware problem creating spurious emission and intermodulation product in the uplink band of 850MHz? Can jumper bad installation really increase by 10dB the RTWP? or the increase was less (a few dB)?

[Philippe]

An interesting return of experience in a specific case: Passive Intermodulation Product occuring in the case of co-location between 3 systems : UMTS and CDMA at 850 MHz and GSM at 900MHz in Telstra, Australia.
Source: RFS magazine "Stay Connected" in 2007

[dremka]

In case of RTWP occurence in the UMTS network checking the system against intermodulation should be done in the first step. The test is very simple - during monitoring RTWP in the observed cell set the maximum tx power in that cell. When RTWP rises as tx power rises intermodulation is suspected. It can be either internal or external but it's simple to differentiate it - external interference reacts to the tilt change... From my experience the most cases of internal intermodulation is due to improper connector fixing - corroded surface acts as a mixer. I've also found several cases of external intermodulation - 100% of them were GSM or/and DCS repeaters with too small attenuation set.
Searching external interference in UMTS network with a spectrum analyzer is tricky to some extent - it isn't rare the interference is broadband and it's difficult to see it unless the noise floor on the SA display is around -130 [dBm] or lower so preamplifier should be used along with pass band filter to avoid intermodulation in the spectrum analyzer alone and false readout in the result.

Update:
In case of RTWP affected cells neighbours list should be also checked. UE connected to other cells can cause elevated RTWP in case of missing neighbours between these (affected and serving UE) cells, especially with lower band (eg 900 MHz) UMTS systems.

[yhussain110]

What is RTWP?

If you work with UMTS,'ve probably heard someone talk about RTWP. Its definition can be found in a dictionary of acronyms, such as http://acronyms.thefreedictionary.com/RTWP: Received Total Wideband Power.

Represents a measure of UMTS technology: the total level of noise within the UMTS frequency band of any cell.

RTWP is related to uplink interference, and its monitoring helps control the call drops - mainly CS. It also has importance in the capacity management, as it provides information for the Congestion Control regarding Uplink Interference.

In UMTS, the uplink interference may vary due to several factors, such as the number of users in the cell, the Service, Connection Types and Conditions of Radio, etc..

As our goal is to always be as simple as possible, we will not delve in terms of formulas or concepts involved. We will then know the typical values, and know what must be done in case of problems.


Typical Values

Ok, we know that RTWP can help us in checking the uplink interference, then we need to know its typical values.

In a network is not loaded, normal, acceptable RTWP Average value is generally around -104.5 and -105.5 dBm.



Values around -95 dBm indicate that the cell has some uplink interferers.

If the value is around -85 dBm, the situation is ugly, with strong uplink interferers.

Usually we have High, Low and Medium measures of RTWP. However, the maximum and minimum values are recommended only as auxiliary or reference, since they may have been caused by a peak of access, or even been forced to have a momentary value due to some algorithm i.e..

Thus, the value that helps us, and has the most accurate information is the same Mean RTWP!

For cases in which cell has two carriers, the difference between them RTWP should not exceed 6 dB.





Based on these typical values, most vendors have an alarm: RTWP "Very High. "


What to do in case of problems?

We have seen that RTWP can cause performance degradation, mainly CS Call Drops. Note: Actually, it's not RTWP that causes performance degradation. What happens is that when its value is 'bad', it's actually indicating the presence of interference - the latter being responsible for degradation.

But what can we do when we find bad values?

If RTWP is not at acceptable levels, some actions should be taken.

The first thing to do is check if there is a configuration issue with the RNC or NodeB. This is the most common case, especially in cases of new activations.
Once verified the parameter settings, the next step is the physical examination, especially jumpers and cables, often partially reversed. It also should be checked if there is faulty transmitters, or any other problem that could generate intermodulation between the NodeB and the antenna.
If the parameter settings and hardware are ok, the chance is very high that we have external interference, such as a Interferer Repeater.

In cases where there may be external interference, we must begin to act after such a prioritization based on how much this is affecting the cell KPI's across the network, if it carry high traffic, major subscribers, etc..

Note: There are many forms of interference in the uplink, both internal and external. Only a few are listed above. The deepening of all possibilities is beyond the goal of being simple to teach the concepts, but this is a suggestion for whoever wants to deepen the study, identification and elimination of interference.


In practice

to find - and eliminate - problems of interference is one of the biggest challenges in our area. For being such a complex problem, we recommend that be collected enough data for each investigation. Insufficient data collected can lead to erroneous conclusions, further worsening the problem.

The uplink interference may appear only in specific periods. Thus, it is recommended that data be collected from at least one week (7 days) for every 24 hours. Usually this amount of data is sufficient. In the figure below, we see different days and times - colorful - a fictional example where the interference occurred.



Data should be collected for the suspicious cell, but also for its adjacent cells, allowing it to make a triangulation increasing the chances of locating the source of interference.

Another way to locate the source of interference is to do a test in field. An antenna guy must gradually change the azimuth of the antenna, while another professional do RTWP measurements. That is, through the information directing the antenna and the respective values of RTWP, you can draw conclusions very good.

It is obvious that changing the online system may not be a good practice, and tests can be made with a Yagi antenna and a Spectrum Analyzer.

Vendors offer several ways to measure RTWP, using the OSS, performance counters and logs.




Dear colleagues,

We experiencing exceptionally high level for RTWP measurements for many cells in Huawei UMTS network. Such level (-85....-75dBm) can not be explained by regular interference caused by mobile phones. This is a new UMTS network with very low traffic.
Spectrum analyzer measurements did not show any external interference sources. Typically measured RTWP with spectrum analyzer is around -110dBm

Event measurements through UMTS cell antenna shows -110dBm level.

Only when RRU unit is in operation the measured RTWP jumps to -80dBm.

GSM and UMTS networks are fully separated and isolated, i.e. separate antennae used and they are space separated and only single carrier used in UMTS - this excludes any source of Intermodulation cause.

The only problem that I can raise is a problem with RRUs. There are ~30% of cells are suffering from constant high RTWP level and 70% of cell suffering from peak levels of RTWP.

Please, assist with possible solution. Or you may know if some issues with new generation of the Huawei UMTS equipment.

Best regards

[Aljunaibi]

It's related to the hardware .. RRU
if you are using active system, then try to relevel (retune) the active system based on accurate PCPICH power and total power.

try to upgrade the framware
Thanks

[giegala]

Don't know if it is still relevant.

We are facing similar problem. Although average RTWP is within limits -> -105..-103, the maximum is much higher up to -80. The peaks are very evident in RTWP monitor - they get 1s peaks of high level (up to -80 and in one particular indoor cell up to -65).

Spectrum analyser on the indoor cell did show any issues - thermal noise level, even we were seeing -65dBm on RTWP monitor. Then it was considered, that Path budget is too good and UE cannot downregulate power because of limitation (by 3gpp it is -51dbm). Therefore 20db attenuation has been added, however no change in rtwp monitor - not even decrease in peaks by 20dB.

The we have limited particular types of traffic - and found the reason --> RRC setups, i.e. RACH procedure. Huawei parameters allow ramping up to max what 3Gpp permits - 20 x 2dB, backoff is the smallest of all vendors i've seen -> 20 (e// has 27 and nsn 25). Therefore we tuned RACH procedure - limited ramping, increased back off. That caused Rach failures altogether for some mobiles.

Note, that we have on many cells, that does not seem to be installation issue, and spectrum analyser does not show anything. Disabling RACH had made RTWP monitor chart clean. I not regard it as an issue, however this RTWP monitor value is transferred to SIB7 what causes just generation of interference. Moreover this likely is causing another issue - high R99 UL RLC retransmission rate and even some RRC setup complete failures.

We are waiting for RND reply, however i would suspect the issue is in RRU software (MRFU is doing just the same). Software version we are running is R13.

[jacc121]

Dear colleagues,

We experiencing exceptionally high level for RTWP measurements for many cells in Huawei UMTS network. Such level (-85....-75dBm) can not be explained by regular interference caused by mobile phones. This is a new UMTS network with very low traffic.
Spectrum analyzer measurements did not show any external interference sources. Typically measured RTWP with spectrum analyzer is around -110dBm

Event measurements through UMTS cell antenna shows -110dBm level.

Only when RRU unit is in operation the measured RTWP jumps to -80dBm.

GSM and UMTS networks are fully separated and isolated, i.e. separate antennae used and they are space separated and only single carrier used in UMTS - this excludes any source of Intermodulation cause.

The only problem that I can raise is a problem with RRUs. There are ~30% of cells are suffering from constant high RTWP level and 70% of cell suffering from peak levels of RTWP.

Please, assist with possible solution. Or you may know if some issues with new generation of the Huawei UMTS equipment.

Best regards

You can try to turn off HSUPA, it's the cause for the high spikes of RTWP. You can try it for a cell since it's cell level.

Btw, hi to all fellow optimisers out there :), like keanchan and choonyeah :)

[dremka]

[QUOTE=jacc121;175720]You can try to turn off HSUPA, it's the cause for the high spikes of RTWP. You can try it for a cell since it's cell level.

I can confirm - for us it helped.

[oswe]

I also have the same in my network. being more visible at indoor sites...
it is almost exactly the same as you describe in here... so I start now to believe it is SW problem... please if any of you guys did open a ticket and got any answer from RNC please share at least the main cause...
thanks !
ps:
I also suspect about the algorithms. for example LDR I cannot make it work... nothing is triggering it...
thanks in advance

[yurii]

Passive intermodulation is an unwanted mixing effect caused
by non-linearity of passive components in the RF path. Intermodulation diverts signal energy partially to other frequencies
(spurious), which may fall into receive bands and cause serious
degradation of system performance.
You should check connectors and cables with site master or PIM analyser.( 100 % you will found something ! )

[andik_stt]

In nodeB bts level change or MOD RXBRANCH
attenuation from 0 to 45
RTWP initial0 (0.1dB) from 0 to -55
Before change this parameter make sure first cabinet - subrack and slot number.

[giegala]

Hi,

the problem have been identified. Our setup is to have 3x of RRC release complete to be sent by UE. However RNC was setup to release RL even after reception of first RRC RELEASE CMP message. Therefore UE will have RL lost and would be ramping UL power causing uncontrolled UL interference.

After RNC was setup to delay RL, RTWP issue was solved.

[cococrunch]

How to check RNC parameter for RRC_CONN_REL_CMP? Thanks



Hi,

the problem have been identified. Our setup is to have 3x of RRC release complete to be sent by UE. However RNC was setup to release RL even after reception of first RRC RELEASE CMP message. Therefore UE will have RL lost and would be ramping UL power causing uncontrolled UL interference.

After RNC was setup to delay RL, RTWP issue was solved.

[FrankPintor]

How to check RNC parameter for RRC_CONN_REL_CMP? Thanks
I think he means the PROCESSSWITCH3_UM_RRCRELCMP_RLDEL_DELAY_SWITCH in URRCCTRLSWITCH?

I'm surprised it made such a big difference, from the information I saw, this problem only affected certain mobiles, I think the iPhone was singled out as one.

[giegala]

Hi,

that's exactly the parameter. It could have been iphones, but nowadays everybody is blaming them. But it is enough to have 1 phone like that and all the phones are tx power upregulated in the cell

[Fosterthiele]

As we all know,While the mobile phone brings great conveniences to people, it also raises new challenge on the security of confidential work. In recent years, the wiretap, cheating in examination, medical negligence and gas station explosion with mobile phone occurred and it has aroused great concern of the society. Maybe it's one of the reasons that promoted the appearance of cell phone jammer (http://www.jammerall.com/categories/Cell-Phone-Jammers/).You may be watching a nice movie or enjoying your nap when you get free for sometime. Still you have chances of getting disturbed with your most loved ones and close friend chatting near you on the cell phone. At such hours, if you really care for your free time then you need to buy a cell phone jammer.

[jackleemaster]

As we all know,While the mobile phone brings great conveniences to people, it also raises new challenge on the security of confidential work. In recent years, the wiretap, cheating in examination, medical negligence and gas station explosion with mobile phone occurred and it has aroused great concern of the society. Maybe it's one of the reasons that promoted the appearance of phone jammer (http://www.jammerfromchina.com/).You may be watching a nice movie or enjoying your nap when you get free for sometime. Still you have chances of getting disturbed with your most loved ones and close friend chatting near you on the cell phone. At such hours, if you really care for your free time then you need to buy a cell phone jammer.

[captain_jejemon]

Hi,

the problem have been identified. Our setup is to have 3x of RRC release complete to be sent by UE. However RNC was setup to release RL even after reception of first RRC RELEASE CMP message. Therefore UE will have RL lost and would be ramping UL power causing uncontrolled UL interference.

After RNC was setup to delay RL, RTWP issue was solved.

Hi PROCESSSWITCH3_UM_RRCRELCMP_RLDEL_DELAY_SWITCH already set to ON.

But still high RTWP are experienced

[brianm]

What is the impact on site performance or user experience of very low Average RTWP of say -110dbm

[giegala]

Such low value shows that RF signal is too much attenuated. It directly reduces cell radius.

It could also mean link disbalance, when UL attenuation is misconfigured. In that case, UE could be camping on cell in idle mode, however will fail to access (setup RRC) because of incorrect calculation of pathloss.

In the extreme case, (and i have seen such) no antenna/jumper is connected to the RF unit.

[leresempe]

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