ASCI (Advanced Speech Call Items)

Advanced Speech Call Items (ASCI) is a set of features used in mobile communication systems to enhance voice quality and reduce interference in speech transmission. ASCI was first introduced in the 3rd Generation Partnership Project (3GPP) Release 4 specification, and has since been incorporated into subsequent releases of 3GPP.

ASCI consists of a suite of voice processing algorithms and techniques that are designed to improve the quality of voice communication in wireless networks. These algorithms are implemented in both the mobile device and the network infrastructure, allowing them to work together to provide better voice quality and a more reliable connection.

There are several key features that are part of ASCI, including voice activity detection (VAD), comfort noise generation (CNG), noise reduction (NR), and echo cancellation (EC). Each of these features is designed to address a specific aspect of voice communication in wireless networks.

Voice Activity Detection (VAD): One of the primary challenges in wireless voice communication is dealing with the fact that people don't talk all the time. There are often pauses in conversation, and during these pauses, the network doesn't need to transmit any data. Voice activity detection (VAD) is a feature of ASCI that helps to identify when someone is speaking and when they're not.

When the VAD algorithm detects silence, it sends a signal to the network to stop transmitting data. This helps to conserve bandwidth and reduce interference in the network. When the algorithm detects that someone is speaking, it sends a signal to the network to start transmitting data again.

Comfort Noise Generation (CNG): Another challenge in wireless voice communication is the fact that there is often background noise that can interfere with the conversation. Comfort noise generation (CNG) is a feature of ASCI that helps to address this issue.

When the network detects that someone is not speaking, it generates a low-level background noise that is designed to mimic the ambient noise in the environment. This helps to fill in the gaps in the conversation and reduce the impact of background noise.

Noise Reduction (NR): In addition to generating comfort noise, ASCI also includes a noise reduction (NR) algorithm that helps to filter out unwanted noise from the conversation. This algorithm uses a variety of techniques to identify and remove background noise, including spectral subtraction, Wiener filtering, and adaptive filtering.

Echo Cancellation (EC): Finally, ASCI includes an echo cancellation (EC) algorithm that helps to address the issue of echo in voice communication. When someone speaks into a mobile device, their voice is transmitted over the network and then played back through the speaker on the other end of the conversation. This can create a feedback loop that results in echo.

The EC algorithm uses a technique called adaptive filtering to identify and remove the echo from the conversation. This helps to improve the quality of the conversation and reduce the impact of feedback.

In addition to these core features, ASCI also includes several other algorithms and techniques that are designed to improve the quality of voice communication in wireless networks. These include:

• Wideband audio: This feature increases the frequency range of the audio signal, allowing for more natural and accurate voice reproduction.
• Variable rate codec: This feature adjusts the rate at which audio data is transmitted based on the available bandwidth in the network, helping to ensure that voice quality is consistent even in low-bandwidth situations.
• Packet loss concealment: This feature helps to address the issue of data packets being lost or dropped during transmission. When this happens, the algorithm can use techniques like interpolation and extrapolation to fill in the gaps in the audio signal.

Overall, ASCI is a powerful set of features that can significantly improve the quality of voice communication in wireless networks. By using advanced algorithms and techniques to address issues like background noise, echo, and packet loss, ASCI can help to ensure that voice communication is clear and reliable even in challenging environments.

ASCI is particularly important in mobile communication systems where bandwidth is often limited and signal quality can be inconsistent. By optimizing the way that voice data is transmitted and processed, ASCI helps to maximize the efficiency of the network and ensure that users have a high-quality voice experience.