Using subsystem performance parameters to optimize end-to-end performance Scott Pennock Senior Hands-Free Standards Specialist QNX Software Systems

Outline Introduction Subsystems Subsystem performance parameters Optimizing end-to-end (e2e) performance Conclusions All content copyright QNX Software Systems

Circuit-switched network Introduction ITU-T G.799.2 defines a mechanism that can be used to improve the end-to-end (e2e) speech communications performance of telephone connections Each Signal Processing Equipment (SPE) on the telephone connection communicates its Signal Processing Functions (SPFs) capabilities to all other SPEs Based on coordination rules, each SPE will either “enable” or “disable” its own SPFs to optimize e2e performance MSC-O MSC-T Server SC-T Server MGW-O MGW-T BSC-O SPNE-T IP packet network Circuit-switched network Land User MS-O Media Path Signalling Path ITU-T G.799.2/Figure I.6  Mobile-to-land call through an IP packet network and a circuit-switched network All content copyright QNX Software Systems

Introduction (continued) This presentation will describe how e2e performance can be further optimized by: Expanding the list of what is considered SPE to include: Acoustic interfaces Signal transport equipment (e.g., speech codec, de-jitter buffer, etc.) Measurement devices (e.g., ITU-T P.561, etc.) Adding subsystem performance parameters to the information exchanged between SPEs All content copyright QNX Software Systems

Terminals are becoming dynamic subsystems -Traditionally terminal equipment considered static; no longer true, subsystems can dynamically change during a call -This figure shows two other candidate SPEs, “Acoustic interface” and “Local/Network transport”; note that SPFs will interact with this equipment—not just other SPFs All content copyright QNX Software Systems

Subsystem performance parameter considerations When is performance measured? Classification into performance levels apriori Real-time measurements of parameters How is performance measured? Signal-based analysis Parameter-based analysis All content copyright QNX Software Systems

Acoustic interface performance parameters All content copyright QNX Software Systems

Example of QoS levels in the Send direction for the Acoustic interface Measurement parameter 1 2 3 4 5 Speech-to Noise Ratio (SpNR) SpNR > 25 dB SpNR > 20 dB SpNR > 15 dB SpNR > 10 dB SpNR > 5 dB Send Frequency Response (SFR) SFR mask 1 SFR mask 2 SFR mask 3 SFR mask 4 SFR mask 5 Send ReVerberation (SRV) SRV > 15 dB SRV > 10 dB SRV > 5 dB SRV > 0 dB SRV > -5 dB Send Distortion + Noise (SDN) SDN < 1% SDN < 2% SDN < 3% SDN < 4% SDN < 5% Speech-to-Echo Ratio (SpER) SpER > 5 SpER > 0 SpER > -5 SpER > -10 SpER > -15 Echo Tail Delay (ETD) ETD < 5 ms ETD < 10 ms ETD < 15 ms ETD < 20 ms ETD < 25 ms Echo Tail coherence (ETco) ETco > 95% ETco > 90% ETco > 85% ETco > 80% ETco > 75% All content copyright QNX Software Systems

Speech enhancement performance parameters All content copyright QNX Software Systems

Local transport performance parameters All content copyright QNX Software Systems

Network transport performance parameters All content copyright QNX Software Systems

Optimizing e2e performance There are many ways subsystem performance parameters can be used to optimize performance: Determining if acoustic interface can support requested service (e.g., wideband, high SNR, low echo path distortion, stereo telephony, etc.) Determining if speech enhancement can handle acoustic interface (e.g., hands-free) Selection of best acoustic interface (could be due to hardware, usage, or environment) Setting speech enhancement parameters based on acoustic interface or speech codec Setting radio link parameters based on speech codec/SNR Selecting speech codec based on local transport error pattern Selecting speech codec based on upstream (or downstream) speech codec to minimize transcoding distortion Turning “off” poorly performing SPFs G.799.2 allows for defining “attributes” for a SPF, but need standardized measurement parameters to be effective All content copyright QNX Software Systems

Conclusions G.799.2 has limited ability to optimize e2e performance e2e performance can be further optimized by: Expanding the list of devices considered SPE to include: Acoustic interfaces Transport equipment Measurement devices Adding subsystem performance parameters, or QoS levels, to the information exchanged between SPE Terminal equipment is no longer “static”; it is dynamic with different subsystems interoperating There is still much work to be done to identify the validate subsystem performance parameters However, this should not prevent designing the information exchange between SPEs so that when performance parameters become available, there is a mechanism for utilizing them All content copyright QNX Software Systems

Thank you Scott Pennock Senior Hands-Free Standards Specialist spennock@qnx.com All content copyright QNX Software Systems