- This topic has 180 replies, 1 voice, and was last updated 14 years, 5 months ago by kishor.
25th January 2006 at 14:32 #33012VijayGuest
Can e n one tell me Why 1 Hz frequency tranmit one bit only without error ???
waiting 4 yr reply plz reply ASAP.31st January 2006 at 09:51 #33013ahmadyGuest
is there a web page or standard with the earlang of pabx7th February 2006 at 10:39 #33014jsveigaGuest
I see you still have doubts about RxQual Sub vs Full and RxQual vs SQI.
Sub vs Full values (this applies not only to RxQual, but to RxLev and FER):
GSM can use discontinuous transmission (DTX) – when there is no sound to transmit, the phone and/or the BTS may not transmit all frames on the timeslot. This means that when you have DTX the RF signal is not present on the whole timeslot. So, when DTX is active and was used (it may be enabled, but not used in specific instants if you “speak too much ;-)) the RxLev and RxQual measured across the whole timeslot period will be meaningless. For this situation, there are measurements of RxLev and RxQual which are taken only on the obligatory frames (not on the actual tranmitted frames, which would complicate matters). These are the “Sub” values.
So “Sub” values are always valid, but may not be as precise as Full values, whereas Full values are more precise, but may be wrong when you have DTX. The network and the phone “know” when to consider the Sub or the Full values for handover decisions because there’s a “DTX was used” flag transmitted.
SQI vs RxQual:
RxQual is part of the GSM standard (05.08), and it is used basically for handover/power control. It is directly related to Bit Error Rate (there is a table on the standard). For each BER range, am RxQual value from 0 to 7 is used.
SQI, as Erik has pointed out, is more true to the actual user experience in terms of voice quality. RxQual alone is not a direct estimative of voice quality because:
– it does not take into account FER and CRC (you may have bad bits spread on different frames, which are corrected by the redundancy protection with no impact on the voice, or all on the same frame, which will cause the frame to be discarded, impacting the voice quality)
– it does not take into account the vocoder in use (even with RxQual and BER = 0, a half rate vocoder won’t give you the voice quality of an enhanced full rate vocoder, and for AMR it will depend on the percentage of bit rate used for each instant)
– it does not take into account the handovers (if you have lots of handovers, voice quality will drop even if RxQual is good – Ok, generally with good RxQual, there will be no handovers, but…)
SQI takes all these factors into account and also their statistical distribution (isolated FER occurences may have little or no impact on voice, for example), and has a very high correlation with actual human scoring of voice quality (better than 90%).
Summarizing, RxQual is more an RF quality paramenter, and SQI is a voice quality parameter.
from question 12 to 25. It has good information about SQI.
Joao S Veiga7th February 2006 at 11:02 #33015jsveigaGuest
sorry, your question was RxQual vs RxQual %, not Full vs Sub…
The RxQual defined on the GSM standard 05.08 is not in %. It is a value from 0 to 7, corresponding to BER ranges.
I suppose the RxQual %, since it is not a standard-defined parameter, may or not have different definitions on different measurement systems, but for Ericsson TEMS Investigation, it means the bit error rate corresponding to the RxQual (number) reported. For this system, the % values range from 0 to 26%, and the (number) values from 0 to 7, and their relationship is as defined on GS 05.08.
Joao S Veiga7th February 2006 at 12:06 #33016BokoGuest
Did you have experience with very low SQI, when using half rate codec with DTX in DL
Boko15th February 2006 at 11:28 #33017VojtehGuest
I have a question regarding the quality of a received signal in GSM. Do you have any idea what is prefered min level signal for a quality GSM data transfer? Is any recommandation to RxQal (1 – 7)? We have problems on the installed GSM devices. Thanks,
Vojteh5th March 2006 at 11:47 #33018meriemGuest
i am looking for a way to calculate the number of circuits given the blocking probability with erlang b formula,could anyone help me please!!!
my mail is:firstname.lastname@example.org March 2006 at 11:54 #33019Saptarshi GhatakGuest
What is earlang? How to measure Telephone call?10th March 2006 at 13:23 #33020Bijaya Kumar MishraGuest
What do you mean by “MS Power vs Timing advance” analysis ?
What message it conveys?
Thanks for your answer.10th March 2006 at 20:46 #33021ErikGuest
BKM, you mention “MS Power vs Timing advance analysis”. I think you must refer to some correlation between the power emitted by the mobile (when Power Control is activated) and the distance between the mobile and the antenna (which is measured by Timing Advance, each unit of TA being more or less 500 meters).
In overall, you should find more or less the same as the formula used for calculating link balance… MSP – PL(d) + AG(a) = R
MSP = minimum MS Power required
PL = Path Loss (in absolute value)
AG = Antenna Gain
R = minimum Reception level accepted by your BTS
a = angle of emission of the shortest signal beam reaching the mobile
I’m not sure what you mean by asking the messages conveyed. TA is just a measure of distance. It is useful for synchronisation (which I think, but not 100% sure, should be only on the side of the MS)10th March 2006 at 23:55 #33022CarolynGuest
I would like to know details about location update in cell and what is LAC?12th March 2006 at 03:12 #33023Balamurali EkambaramGuest
How to Calculate the Link load of a Signalling link? Also how many voice circuits does one Signalling link support?16th March 2006 at 18:07 #33024ErikGuest
Carolyn, if you just “google” what you are looking for, you can find it. For example: http://www.geocities.com/gsmmobilereport/mobilemanagement.htm
In short, LAC (Location Area Code) is an identifier for a geographic area. Location updates are performed to let the network know where the mobile stations are in case of a MTC. If someone tries to call you, the network will send a “paging request” on the whole LAC where your mobile has last been registered, to try to contact you. Your mobile will then contact the network using a RACH to make the connection complete between the person calling you, the network, and yourself.
I hope this helps…26th May 2006 at 06:23 #33025BharatGuest
What we do in RF survey & Microwave survey, plz Differensiate20th June 2006 at 09:47 #33026TineGuest
I understand FER is a voice element more than RF element. Can high FER rate cause high call drops when RxQual andRxLev are good