dsps and hmp in voice over ip application design

August 3-4, 2004 • San Jose, CA • www.voipdeveloper.com

DSPs and HMP in Voice over IP

Application Design

Mike Kane

Senior Product Manager

Brooktrout Technology


DSPs and HMP in VoIP App Design

• Changing Requirements

• DSPs & HMP Issues

• Use Case Examples

• VoIP Solution Requirements

• Conclusions


The Changing Media Processing Environment

• Four migrations to manage– Migration to IP networks– Adoption of Industry-standard APIs – Migration from Hardware to Host-based Media Processing– Adoption of nextgen architectures

DSP-BasedHardware

Host Media Processing

PSTN IP

Today


The Changing Media Processing Environment -The Perceived Promise

• IP networks – Less ”virtual” resources are required per call = less cost– Multimedia & greater bandwidth = new solutions

• Adoption of Industry-standard APIs – More tools = faster, cheaper development– Easier application level integration = incremental development

• Migration from Hardware to HMP– Software = easier installation/management– No DSP hardware = lower cost

• Adoption of NextGen architectures– Modular systems = install only what you need– Decentralized decisions = flexibility, adaptability, extensibility


• Echo Cancellation• Gain Control• DTMF handling• Speech Buffering• Transferring• Tromboning


• Telephony Interface• Call Quality• Media Processing• Call Processing• Call Management


Migration to IP:TDM Voice Processing Requirements

PSTN

Analog/Digital TDM

PBX

Voice Processing

System

• Prompt & Collect• Play & Record• Conferencing• Speech Management


DigitalSet

ResidentialPhone

All TDM app functions & controlhappen at the voice processing system

All TDM app functions & controlhappen at the voice processing system


Migration to IP:VoIP Requirements

PSTN

IP

IP PBX

IVR System

AccessGateway • Echo Cancellation

• Gain Control• DTMF handling• Speech Buffering• Transferring/Tromboning

• Echo Cancellation• Gain Control• DTMF handling• Speech Buffering• Transferring/Tromboning

• Telephony • Call Quality• Media Proc.• Call Processing• Call Mgmt

• Telephony • Call Quality• Media Proc.• Call Processing• Call Mgmt



IP app functions & control happen at different pointsin the IP architecture

IP app functions & control happen at different pointsin the IP architecture

IP Phone


Migration to IP:VoIP Requirements

Features to Ensure Voice Processing working with Access

Gateway or IP PBX• Echo cancellation to support latency between GW and HMP Host• Gain Control to support voice quality • Interoperability with Access Gateway

– DTMF transport support across VoIP network between GW and Host (RFC 2833)

– Signaling support for circuit switching inband information

– SIP Call Control

– Codec support

• Gateway Support for desired connection to Central Office or PBX– Echo Cancellation

– Analog FX0


AdoptionStandards-Based Development

• Emerging standards for Application APIs including SALT and VXML

• Enabling API integration to Application API

ApplicationApplication

Enabling APIEnabling API

Media ProcessingMedia Processing

Network InterfaceNetwork Interface

Application APIApplication API

• Speed development for speech, IVR, multimedia

• Common application across TDM and IP

• Platform portability

Enabling APIEnabling API

Media ProcessingMedia Processing

Network InterfaceNetwork Interface

Abstraction LayerAbstraction Layer








DSPs & HMP Issues #1: Programmability

• Where is programmability happening?– Rarely at DSP but…APIs don’t always

expose DSP functionality– Direct APIs expose DSP or HMP functionality

but…don’t integrate IP PBX or Gateway control

– Standards-based APIs have the potential to integrate and provide easier development but… don’t go deep enough for call control


Migration from DSP to HMP: DSP Value Comparison

• Predictable performance per board• Near linear scalability using multi-boards• Interoperability over H.100• IP Capable• Standards Driven• Design/Functional maturity• Regular performance improvements• Regular cost improvements


DSPs & HMP Issues #2: Scaling/Performance*

# of channels

20

10

Single SpanDSP Board

# of channels

SingleCPUHBM

DualCPUHBM

30

50

40

60 Dual SpanDSP Board

Processor intensive functions have dramatic impact on performance

• Conferencing (-30%)• Fax (-50%)• Transcoding (-80%)

Processor intensive functions have dramatic impact on performance

• Conferencing (-30%)• Fax (-50%)• Transcoding (-80%)

* # of channels is illustrative. Actual scaling numbers will vary by processor and by product.

* # of channels is illustrative. Actual scaling numbers will vary by processor and by product.

Prompt & Play (Announce-ments)

Play &Collect(Messag-ing)

Play &Record(IVR)

Confer-encing

Trans-coding

FAX


Migration from DSP to HMP: HMP Value Comparison

• Hardware Independence• Ride Moore’s Law Curve• Low Total Cost of Operations

– Software model– Remote support/upgrades

• Low Logistics– Low inventory– Low/No shipping

• Standards based – Development– Interoperability

• Rapid performance improvements• Leap in cost improvements


DSPs & HMP Issues #3: Total Cost of Operation (TCO)

• Distributed Business Case – Vroom Auto Parts– Vroom sells 4 & 8 port auto parts inventory and ordering systems to 100’s of dealers

across the US. Due to competition, Mr. Vroom needs to find ways to cut costs. Today he sells 4 and 8 port analog board systems.

– AssumptionsAnalog Board

SolutionHMP

Solution

Purchase $1800 $1400

Installation $1000 $500

TCO $2800 $1900

SAVINGS 32%

• Purchase includes approximate list price of voice product plus PC & OS.

• Board Solution assumes site visit/HMP remote install

• Upgrade is from 4 to 8 ports. Board requires site visit, HMP is 4 port license with phone support install. Upgrade $1800 $400

TCO $4600 $2300

SAVINGS 50%


Use Case A: Speech-Enabled Auto Attendant TDM/DSP vs IP/HMP

PSTN IP

ASRSystem

IP PBX

1. Incoming call to PBX2. PBX Call Mgr sees

call for speech3. PBX Call Mgr turns on

EC, sends call to HMP4. HMP Buffers Speech5. API takes buffer

performs app

1. Incoming call to PBX2. PBX Call Mgr sees

call for speech3. PBX Call Mgr turns on

EC, sends call to HMP4. HMP Buffers Speech5. API takes buffer

performs app

PSTN

ASRSystem

PBX

1. Incoming call for speech treatment

2. App turns on EC & VAD @ DSP3. DSP/Driver Buffers Speech4. API takes buffer performs app

1. Incoming call for speech treatment

2. App turns on EC & VAD @ DSP3. DSP/Driver Buffers Speech4. API takes buffer performs app

TDM/DSP Configuration

IP/HMP Configuration


Use Case B: Conferencing ServiceIP/DSP vs IP/HMP

ASRSystem

1. Incoming call come to GW

2. GW Call Mgr passes calls to Conf sys.

3. HMP mix calls across codecs

4. Host takes 30% - 80% capacity hit w/ confer. & codecs

5. Add more hosts to scale


2. GW Call Mgr passes calls to Conf sys.

3. HMP mix calls across codecs

4. Host takes 30% - 80% capacity hit w/ confer. & codecs

5. Add more hosts to scale

PSTN

ConferencingSystem

1. Incoming call come to GW2. GW Call Mgr passes calls to

Conf sys.3. DSP mix calls across

codecs4. DSPs are added as app

scales

1. Incoming call come to GW2. GW Call Mgr passes calls to

Conf sys.3. DSP mix calls across

codecs4. DSPs are added as app

scales

IP/DSP Configuration


IP

AccessGateway

PSTN

Conferencing System

IP

AccessGateway


Use Case B: Distributed IVRIP/DSP vs IP/HMP

IP/DSP Configuration


PSTN

IPIVR

System

AccessGateway

IP

IVRSystem

AccessGateway

PSTN

IP IVRSystem

AccessGateway

IPIVR

SystemAccessGateway


2. GW Call Mgr passes calls to IVR

3. App takes call



3. App takes call



3. DSP receives call over IP

4. DSPs passes call to app



3. DSP receives call over IP

4. DSPs passes call to app


Issues in VoIP Solution SelectionVision Reality Guidance

Programmability & Control

• IP has smaller, less expensive components

• simpler standards

• IP More complexity & integration

• immature standards

• look for layered API architecture

• look for bridge from TDM to IP

Scale • more options

• scale with CPUs

• scale with purpose-built DSPs

• single technologies can’t solve all problems, need DSPs & HMP

• common APIs for DSP & HMP

• HMP for IVR/ASR, HW acceleration for conferencing, codecs

Total cost • HMP & IP mean lower cost

• complexity can add cost

• look for bridge from TDM to IP


DSPs and HMP in VoIP App DesignConclusions

• Many dimensions to comparison

• Both DSPs and HMP have place

• Choice is as much about architecture as technology

• Look for a VoIP solution that is flexible, that allows both DSP and HMP options

dsps and hmp in voice over ip application design

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