Ask the Expert - Recent Threads

How to expand coverage?

TellyHwang — Fri, 26 Apr 2013 03:02:53 GMT

HI !

I like to know how to expand coverage in LTE system.

Easily, we can change amp power and reverse gain but there are some restrict in random access in cell edge I think.

Can I expand coverage if I change zero crrelation zone config ?

Cell reselection

sanjeev.aus — Tue, 14 May 2013 09:16:49 GMT

Hi Experts,

I have one doubt when UE is reselecting to 3G, to calculate trigger point based on Threshold Serving Low, which qrxlevmin is taken into account, from SIB-1, SIB-3

Trigger point is, measured RSRP < threshServingLow + qrxlevmin ( Now my question is this qrxlevmin is from which SIB-1 or 3....???)

IPv6, multiple APN and MVPN in LTE

olegol — Tue, 07 Aug 2012 11:36:47 GMT

Who can explain what I need to add / configure to / in Ericsson LTE core for support IPv6, multiple APN and MVPN? My core and eNBs loaded by 2011B version.

Throughput issue in PUSCH power control mode

kapilrancore — Tue, 21 May 2013 07:20:51 GMT

However, while doing these power control tests we realized that for RSRP < -90 dBm e.g. RSRP = -95 dBm or RSRP = -100 dBm, the UL throughput for Absolute Mode is noticeably lesser compared to the UL throughput in case of Accumulate Mode.

This is not expected. In conducted environment when a path loss is set by attenuator it remains the same and there is no large scale or small scale fading which the power control has to mitigate. So in the test conditions created in the lab the power control loop should settle down quickly and irrespective of the type of Power Control Mode Accumulate or Absolute the UL Throughput should be the same.

RRC Connection Reconfiguration Msg- apn_ambr_dl_ext = 158 (0x9e) (100 Mbps) and apn_ambr_dl = 254 (0xfe) (8640 kbps)

mohsin.vit — Fri, 17 May 2013 00:27:23 GMT

Hi,

Here is a small snippet of UE log I collected for LTE Attach Procedure using QXDM. This snippet is part of the RRC Connection Reconfiguration message that piggy backs NAS messages Attach Complete and Activate EPS Default Bearer Request.

After all my readings on the internet and various blogs I am still not able to figure out the difference between apn_ambr_dl_ext and apn_ambr_dl.

My basic question is which of the two is the actual APN-AMBR that the UE is allowed?

apn_ambr_incl = 1 (0x1)

apn_ambr_dl = 254 (0xfe) (8640 kbps)

apn_ambr_ul = 254 (0xfe) (8640 kbps)
oct5_incl = 1 (0x1)
apn_ambr_dl_ext = 158 (0x9e) (100 Mbps)
oct6_incl = 1 (0x1)
apn_ambr_ul_ext = 158 (0x9e) (100 Mbps)
oct7_incl = 0 (0x0)
oct8_incl = 0 (0x0)

Network Config is as follows :

DL Bandwidth = 10 MHz (50)

Number of TX Antennas = 2

UE is using only one APN.

speedtest.net showed ~27Mbps on the UE.

Any insight will be highly helpful.

RSSI Calculation

mehran.ali — Mon, 20 May 2013 14:11:25 GMT

hello experts

I would like to know whether synchronization is necessary for the calculation of RSSI or not.?

By synchronization I mean synchronizing the frame boundaries through PSS and SSS synchronization.

Thanks

The relationship about uplink/downlink subframe and the special subframe

threestoner — Mon, 20 May 2013 13:38:04 GMT

I'm confused that the relationship about uplink/downlink subframe and the special subframe . Does it influence the UE's switch ? I have experimented more than twenty times , but I still have no idea about the relationship . Can you help me( A student from China)?

I wish I can receive your reply soon !

Thanks a lot

Regarding GTP prim protocol cause "Another node is about to go down" in cause section

kunalkumar — Fri, 17 May 2013 14:31:41 GMT

Hi All,

in the gtp protocol implementation as per the ftp specification we have the following messages:

Charging related Cause values introduced for the present document:

In requests:

63 This node is about to go down

62 Another node is about to go down

61 The receive buffers are becoming full

60 The transmit buffers are becoming full

The use case for Another node is going down is that is :

If CGF(Which comprises of GTP node and communicates with GSN for cdrs) detects a link failure towards the Billing system then it generates a message with message "Another node is about to go down " it also suggests an alternative node for redirection if redirection request is enabled.

Now my question is :How does the CGF/GTP node detects the link failure towards Billing system as billing system is mostly different from CGF node...

Can any one suggest the standard way to do this.

PLZ help.............................asap.

59 System failure

in TAU, how mme knows if the UE was in SGSN(2/3G) or in MME?

watson100 — Sat, 18 May 2013 04:37:08 GMT

If the UE was in LTE coverage and served by MME and inter a mme coverage, The new MME uses the GUTI received from the UE to derive the old MME/S4 SGSN address

If the UE was in 2/3G coverage and served by Gn-SGSN and inter a mme coverage,The new MME sends SGSN Context Request (old RAI, P-TMSI, old P-TMSI Signature, New SGSN Address) to the old SGSN to get the MM and PDP contexts for the UE.
the MME derives the old SGSN from the old RAI and the old P-TMSI (or TLLI).

MY question is how the new mme distinguish this 2 situation.

i know in R10, the guti type can tell the new mme where this guti is Native GUTI or mapped GUTI.

but what is in R9? HOW will mme do if there is no guti type in NAS message.

THANKS

Reading PSS and SSS info

Rani — Fri, 17 May 2013 12:54:17 GMT

Hello,

I would like to know the PCI from SSS and PSS using the symbol table on VSA. Is it possible? as the symbol table shows binary decoded information after the mapping and descrambling.How to read it?

Thank you for your help

Connection between RU (radio unit) and base station capacity?

infi — Tue, 07 May 2013 15:01:13 GMT

hello!

I learn that the capacity of base station is dependent the bandwide, MIMO and another thing.

When I read LTE station base datasheet, I saw that could be 1-12 RU (radio unit).

Do have connection between RU (radio unit) and base station capacity?

thanks.

LTE Redirection

dancorry — Tue, 14 May 2013 04:43:33 GMT

For a UE to move from LTE to CS service, does the Redirection correspond to handover from LTE to UMTS, or UE goes into the UMTS domain in idle mode after redirection for CS fallback.

I am confused with Cell redirection and handover from EUTRAN command, can anyone give some info on this.

CSFB failure with cause miscellaneous unspecified

Yassine — Tue, 14 May 2013 18:51:01 GMT

Hi experts, it's my first post in this forum and hope that i'll get some useful stuff :). Let's begin, i detected on S1 interface a CSFB which terminates with a UE context release request sent from the eNode B toward the MME with cause miscellaneous unspecified. Anyone who knows the exact cause meaning? Why do we have such message?

RACH Required During Handover

Varun — Wed, 15 May 2013 06:26:41 GMT

Dear Experts,

This may sound very silly to many of you.

However, in LTE, I am failing to understand, as to why we need to send a RACH attempt during the Handover Attempt using one of the reserved Preambles for Contention Free Random Access. Because I have never encountered any description for GSM or WCDMA HHO's about RACH Attempts during Handover Access.

So if someone could explain, whether the same process is carried out in GSM/WCDMA or in LTE, why the Handover Access Signalling cannot be carried out in a dedicated way.

Thanks a Lot in advance for your precious time...!!!!

Regards...!!!

Mapping LTE MCS scheme to MCS indexes

Abdulaziz Ghaleb — Wed, 15 May 2013 07:53:51 GMT

Dear Experts,

In LTE, we have MCS-1 to MCS-13.

QPSK 1/8

QPSK 1/5

QPSK 1/4

QPSK 1/3

QPSK 1/2

QPSK 2/3

QPSK 4/5

16QAM 1/2

16QAM 2/3

16QAM 4/5

64QAM 2/3

64QAM 3/4

64QAM 4/5

We also have 29 MCS indexes range form 0 to 28. (I_mcs =0 to I_mcs -28)

I would like to know how to map MCS ( with the coding rate) to the MCS index (I_mcs).

Thank you in advance for your help.

Kind Regards,

Aziz

orthogonal codes usage

saikiran vangapandu — Fri, 10 May 2013 05:34:36 GMT

During RACH procedure, eNodeB interprets different RAPID with same RNTI.

This could be possible with uasge of differnt orthogonal codes by UE.

How UE will know which orthogonal code to be used during intial call setup?

LTE signal demodulation

boudalal — Fri, 10 May 2013 09:25:53 GMT

Hi,

I am using VSA last version for LTE signa demodulation. Knowing the PCI,I have already set the RS frequency shift and needed parameters (bandwith, RS location..), but still the demodulation is not correct. WellI have no synchronisation error but the constellation (OFDM meas are not correct)

I think it's because of a low SNR, I amnot sure. How can I improve SNR ? or there are any other parameters I should set.

I'va taken a screenshot of what I get.

Integrity Algorithm for Non-Emergency Calls?

Vijay Soundararajan — Mon, 13 May 2013 09:10:54 GMT

Can a non-emergency call have EIA0 (Null) Integrity for AS and NAS? Or NULL integrity is only for emergency calls as per specification? Or is it vendor specific?

Sequence of HARQ redundancy versions in downlink

biswanath.swain — Sun, 12 May 2013 17:47:23 GMT

36.321 mentions explicity the sequence of redundancy versions for uplink re-transmissions, but does not have any details for downlink re-transmissions.

Extract from standard for UL: The sequence of redundancy versions is 0, 2, 3, 1

Does 3GPP standard has specified the downlink re-transmission sequence of reduncancy versions? If yes, is it a fixed sequence like uplink or it is dynamically selected based on some criteria?

-- Biswanath

Default or Dedicated bearer

dancorry — Thu, 18 Apr 2013 21:12:32 GMT

can anyone tell me, Is there any parameter which indicates whether the bearer is a default or dedicated bearer.

expert system

chepetsa — Thu, 25 Apr 2013 15:08:51 GMT

may anyone give me an area of expertise that has a problem that needs to be solved by an expert system.

How to do power scaling for cell specific reference signal in Physical Layer

Abhishek kumar — Fri, 10 May 2013 12:38:12 GMT

I would like to know about following :

1. What is the RMS power for cell specific reference signal to be used in Physical Layer ?

2. How we can do the power scaling for Cell specific reference signal depending upon the power of eNB?

3. What are the parameters on which power of Cell specific reference signal depends and what are the relation between them ?

4. How cell specific reference signal is related to other downlink channels ?

Sync of uplink and downlink NAS transport pkt.

Pankaj Singh — Wed, 24 Apr 2013 09:19:24 GMT

Hello Guys,

Actually I got stuck with s1ap pcap. I was trying to understand the entire packet flow. But what I have seen is, after initialUEmessage sometimes it shows uplink/downlink NAS transport messages and sometimes not. what's happening actually ? why it doesn't show these message every time.

Packet flow which I have seen is :-

Src Dst Pkt

10.104.1.34 192.168.0.165 InitialUEmessage

192.168.0.165 10.104.1.34 SACK

10.104.1.34 192.168.0.165 InitialContextSetupResponse

What's that ? why it doesn't have NAS messages also.

Please Reply.

Thanks in advance

Very Poor RRC Accessibility

krishnan venkataraghavan — Mon, 29 Apr 2013 11:37:28 GMT

Hi Experts!,

RRC setup success rate is very poor in one of the networks. The cause of failure seems to be RAC(Radio Access Control) which is 100% on top worst cells.

I have checked the Admission Control Parameters everything seems fine. No restrictions on PUCCH front either. There are no active/history alarms on the cells. This issue is present till date. Your suggestions for troubleshooting this are most welcome!!

CQI reporting

kishore.nittala — Tue, 30 Apr 2013 05:01:13 GMT

Based on the measured RSRP and RSRQ on the S-Cell, the feedback on the signal strength is sent to the eNB by the UE based on the CQI reports.

How does the UE calculate this CQI?

how does the UE translate the measured signal strength to value between 1-15 as CQI.

is there a direct mapping? Any spec reference?

Best regards

Kishore