SQI optimization

**justdream** · 2011-11-24, 06:51 AM

Dears,

Could you please share here your expereince about SQI optimization?
I didn't participate in this issue before, so kindly advcie..

**Finetopix** · 2011-11-24 06:51 AM

**louvre** · 2011-11-24, 07:29 AM

This one is tricky and it has lot of variable involved some of them are very subjective and if not done properly can give very weird results. So what is SQI , it is speech quality Index. the word itself give reference to its trickyness... mainly 2 words speech and quality.. so how do quantify or analyze a speech what is baseline on which you will decide it is good or bad speech.. e.g. English and Chinese are two completely different langauge which has no inlinking to each other.. so you compare english with chinese baseline what will be happening, you will get result which is not authentic thats where it becomes subjective as its a matter of perception for a langauge and it is different for each and every user. So basically you have to do MOS test before you can go any further in this endavour... Then you have to figure out about the quality part once you have sorted MOS part in the SQI.. where you can use quality optimization technique to solve any detected problems.

I am attaching to freely available docs which i hope will guide you through the complex part of SQI and MOS relation.

**louvre** · 2011-11-29, 03:54 AM

Originally Posted by polo

password please?

its the default password

**peanut** · 2011-11-30, 08:58 AM

Traditionally, speech quality in GSM networks is measured by means of the RxQual parameter. RxQual, however, suffers from a number of drawbacks which make it an unreliable indicator of speech quality. SQI is a more sophisticated measure which is dedicated to reflecting the quality of the speech (as opposed to radio environment conditions). This means that when optimizing the speech quality in your network, SQI is a better criterion to use.

RxQual and Its Limitations
RxQual is obtained by transforming the bit error rate (BER) into a scale from 0 to 7 (cf. 3GPP TS 45.008, section 8.2). In other words, RxQual is a very basic measure: it simply reflects the average BER over a certain period of time (0.5 s). By contrast, a listener’s assessment of speech quality is a complex process which is influenced by many factors. Some of these, all of which RxQual fails to take into account, are the following:
• The distribution of bit errors over time. For a given BER, if the BER fluctuates very much, the perceived quality is lower than if the BER remains rather constant most of the time. Different channel conditions give rise to radically different BER distributions. However, since RxQual just measures the average BER, it cannot capture this. (In fact, the logarithmic scale of RxQual gives rise to the opposite effect: a high BER variance gives a better RxQual than a low variance does. This is completely misleading from a speech quality point of view.)
• Frame erasures. When entire speech frames are lost, this affects the perceived quality in a very negative way.
• Handovers. Handovers always cause some frames to be lost, which generally gives rise to audible disturbances. This does not show at all in RxQual, however, since during handovers BER measurements are suppressed.
• The choice of speech codec. The general quality level and the highest attainable quality vary widely between speech codecs. Moreover, each codec has its own strengths and weaknesses as regards types of input and channel conditions.
In short, RxQual fails to capture many phenomena that have a decisive influence on a listener’s judgment of speech quality. Using RxQual for optimization of speech quality in the network thus leads to suboptimal results.

Design of SQI
SQI has been designed to take into consideration all the phenomena discussed before. This ensures that it will produce an unbiased prediction of the speech quality, independently of channel conditions and other circumstances. Somewhat roughly, the computation of SQI involves
• the bit error rate (BER)
• the frame erasure rate (FER)
• data on handover events
• statistics on the distributions of each of these parameters.
Furthermore, for each speech codec, SQI is computed by a separate algorithm which is tuned to the characteristics of that codec.
Like RxQual, SQI is updated at 0.5 s intervals.

Source: Tems Investigation help manual

**rfoptman** · 2011-11-30, 05:27 PM

Attached is some documents describes SQI and how it can be optimized. Based on my experiences, applying AMR feature in the network will increase the SQI level siginficantly, as we experienced it in our network, applying AMR increased SQI in all the network.