SIST EN 300 965 V8.0.1:2003

SIST EN 300 965 V8.0.1:2003 is the Slovenian standard identical to EN 300 965 Version 8.0.1 for the GSM full-rate speech Voice Activity Detector (VAD). It specifies the VAD used on full rate speech traffic channels in the Digital cellular telecommunications system (Phase 2+), so GSM speech codec implementers and test engineers can apply the same detection logic and parameter updates.

What does SIST EN 300 965 V8.0.1:2003 specify?

SIST EN 300 965 V8.0.1:2003 specifies the Voice Activity Detector for full rate speech traffic channels in GSM 06.32 version 8.0.1 Release 1999. The scope note says it is updated to version 8.0.0 CRs from SMG#31, so the edition reflects that change set.

The document is centered on the VAD algorithm and the variables, thresholds and equations that drive it. In practice, that means implementers need to follow the same signal checks and update rules if they want compatible behavior.

What are the key requirements of SIST EN 300 965 V8.0.1:2003?

The standard defines the VAD decision process through a set of formulas and update steps. The practical aim is to decide whether a speech frame contains active speech or background noise, using the same logic across GSM implementations.

Detection logic

• The document uses periodicity detection as part of the speech decision. This matters because voiced speech has repeating structure, so the detector does more than look at level alone.
• The formulas reference signal measures such as ACF[0] and a threshold comparison. Implementers need to calculate these values the same way, or the VAD decision can drift from the intended behavior.

Threshold and state adaptation

• The algorithm uses internal variables such as thvad, pvad, rvad and adaptcount. These govern threshold setting and adaptation, so they are central to the detector state.
• The update logic shows how thresholds are increased, decreased or limited by margins and counters. In practice, this controls how quickly the detector follows changing noise conditions.
• The document includes initialization and update expressions for the VAD state. That is important for coding and for any test that checks the first frames after start-up.

Numerical processing

• The body contains recursive calculations, intermediate variables and error-related expressions. These are not just theory - they define the exact processing chain an implementation must reproduce.
• The equations also show how derived parameters are formed from earlier values. For a reader, that means the detector is specified as a step-by-step calculation, not as a loose functional description.

What terms does SIST EN 300 965 V8.0.1:2003 define?

• Voice Activity Detector (VAD) - the function that decides whether a GSM full-rate speech frame contains active speech.
• full rate speech traffic channels - the GSM traffic channels to which the VAD applies.
• periodicity detection - the check for repeating signal structure that helps identify voiced speech.
• thvad - the VAD threshold variable used in the decision and adaptation logic.
• pvad - an internal VAD parameter used in threshold calculations.
• rvad - another internal VAD parameter used in the adaptation process.
• adaptcount - a counter that tracks adaptation activity and helps control threshold updates.

Who uses SIST EN 300 965 V8.0.1:2003?

SIST EN 300 965 V8.0.1:2003 is used by GSM speech codec designers, baseband engineers, and equipment vendors that implement full-rate speech processing. It is also relevant to test laboratories and conformance teams that verify VAD behavior against the specified GSM algorithm.

Quality managers and buyers use it when they need compatibility in GSM voice processing across handsets, base stations, chips, or test equipment. The standard helps them check that a product follows the same VAD method as other GSM implementations.

What changed in SIST EN 300 965 V8.0.1:2003 from the previous edition?

SIST EN 300 965 V8.0.1:2003 updates version 8.0.0 CRs from SMG#31.

What does the SIST EN 300 965 V8.0.1:2003 document contain?

The document contains a mathematical description of the VAD processing chain for GSM full-rate speech traffic channels. It includes formulas for threshold handling, periodicity-related checks, adaptation control and internal state updates.

It also contains stepwise algorithm logic written through variables, conditions and recursive expressions. For implementers, these parts are the basis for software coding, algorithm verification and conformance testing.

The body shows how the detector derives and updates values such as thresholds and counters during operation. That makes the document useful not only for design, but also for debugging and comparing measured behavior against the specified VAD rules.