A Speech Processing Solution in a 3G Media Server Miikka Rautapää Nokia Networks Supervisor: Professor Raimo Kantola

Abbreviations AECAcoustic Echo Cancellation ALCAdaptive Level Control AMRAdaptive Multi-Rate (speech codec) AMR-WBWideband AMR (speech codec) BSSBase Station System DSPDigital Signal Processor ECEcho Cancellation EFREnhanced Full Rate (speech codec) FRFull Rate (speech codec) MIPSMillion Instructions Per Second NSNoise Suppression RANRadio Access Network TFOTandem Free Operation TrFOTranscoder Free Operation

Agenda Problem Description Speech processing applications 3G Network MGW architecture Speech processing media server Testing Results Conclusions & Future Work

Problem Description The problem MGW provides services for different interfaces Every service has own speech processing applications The objective Find a solution to share speech processing applications for all MGW terminations regardless of their interfaces Used methodology Case: own solution for the media gateway project

Speech Processing Applications Speech coding Tandem coding avoidance (e.g. TFO, TrFO) Speech enhancements (e.g. EC, AEC, NS, ALC) Speech synthesis Speech recognition Conferencing, Announcements, Interactive voice response Etc… Need lots of processing power

3G Network (1/2) Next-generation network Media gateway (MGW) routes traffic between packet network and circuit-switched network. Media server processes, manages, and delivers the media resources. Open, scalable architecture

3G Network (2/2) 3GPP release 4 network MGW MSC Server IP/ATM backbone Simplified architecture of the 3GPP release 4 network

MGW Architecture Interfaces ATM, RAN PSTN, BSS IP DSP Unit Control processor DSP chips  DSP software  MGW applications provide different user plane framing protocols for different interfaces, and different supplementary services (e.g. announcements) for other MGW applications.  MGW server processes provide basic functions for MGW applications.  DSP Platform provides connection management, timer services and basic operating system functions.

Speech Processing Media Server Integrated part of the MGW DSP Serves MGW applications with different speech processing applications FR, EFR, AMR ALC V-model design Client/server Signalling interface * Own contribution

Testing Unit, integration and system testing True media gateway hardware Bit-exact tests Performance measurements Codecs Overhead (control code)

Results 510 test cases (passed) FREFRAMRDTXOverhead MIPS ControlCodecsALCMulti channel Performance measurements (encoder&decoder)

Conclusions Speech processing applications Several applications Need lots of processing power Media server Optimised as enhanced services platform Integrated to the MGW DSP Layered software (applications – servers – platform) Results 510 test cases Performance depends on application algorithms

Future Work Other applications (e.g. AMR-WB, AEC) Easy to integrate Interface Signalling Function calls