August 3-4, 2004 San Jose, CA Successfully Offering VoIP- Enabled Applications Services Jan Linden...

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

Successfully Offering VoIP-Enabled Applications Services

Jan LindenVice President of Engineering


Message

• Everything necessary for offering high quality VoIP in the applications market exist today

• However, many factors have to be considered to avoid pitfalls


VoIP in the Applications Space• Additions of real-time voice communication in

applications are booming– Peer to peer softphones (phone replacement or

complement)– Conferencing– Web collaboration– Education (one to many presentations)– Push-to-talk

• Many different types of devices– PCs– PDAs and smartphones with wireless access – Dedicated hardware


Design Considerations

• Speech quality• Ease of use• Time-to-market• Flexibility• Network

impairments

• Cost• Signaling• Infrastructure• Features• Device

considerations


Quality Aspects• Attention to details

– A chains is only as strong as its weakest link• Choice of codec• Sampling rate (narrowband 8 kHz vs. wideband

16 kHz)• Implementation issues• Auxiliary components (e.g. AGC, VAD, AEC)• Low latency

– One of the most important aspects and also very hard to achieve


Handling of Network Degradation

• Typical problem cases:– Internet applications– Wireless

• Packet loss concealment– Smooth concealment necessary

• Jitter– Jitter buffer necessary to ensure continuous

playout– Trade-off between delay and quality


Ease of use• Easy installation and upgrades• Audio tuning wizard or similar• Hands free operation (requires AEC)• Intuitive calling and use of other

functionality• Presence and address book• Support


Signaling and Transport• Call setup signaling

– Proprietary or standard (SIP, H.323, etc)– Reliability– Firewall and NAT traversal– Presence support

• Transport protocol– Proprietary or standard (UDP, RTP)– Reliability– Firewall and NAT traversal– Real-time performance


Auxiliary Functionality

• PSTN access• Voice mail• Call forward, hold, etc.• Video support• Instant Messaging• …


Infrastructure

• Server based or peer-to-peer– Call setup– Conferencing– Presence, address book, voice mail, etc.– Compatibility


Device Issues• Operating system

– Is it a real-time OS?– Support for multitasking– Delay and jitter

• Audio hardware and software– Delay– Quality– Sampling frequency support– Hands free support

• Clock drift– Hard to detect and compensate for

• Complexity – especially on PDAs


Design Options• Build your own

– Performance not known - risk– Long development time and time-to-market– Lack of expertise?– High cost– Flexibility

• Purchase full solution– Known quality– Short time-to-market– Low flexibility– Proven technology


Design Options cont.

• Purchase building blocks– Building blocks:

• Voice processing• Call setup and transport protocols• Application

– Best of class– Short time-to-market– Flexible– Proven technology


Performance Comparison

• Three VoIP clients with the very similar feature lists compared

• Significant delay differences – One way delay from 80 ms to 250 ms– Some clients have huge latency variations

• Basic speech quality– Differences in spectral characteristics (tinny

and muffled)– Clicks and pops


Performance Comparison cont.

• Handling of degraded networks– Acceptable packet loss varies from 3 % to 15 %– Long delays

• Hands-free performance– Many clients have full echo or are cutting out

the signal in an unacceptable way• Sensitivity to device difference varies• Rapidly varying gain control in some cases• Complexity fairly similar



• Audio demonstration– Same settings for all three clients– Codec used: G.711– Three test cases:

1. Perfect network2. 3 % packet loss3. 10 % packet loss


Performance Comparison cont.Client 1 Client 2 Client 3

Wideband support Yes No No

Echo cancellation Yes, full duplex and very good quality for standard setup

Yes, very poor performance. Significant clipping and often high echo even for a good setup

Yes, very poor performance. Significant clipping high echo 50 % of the time even for a good setup

Gain control Yes Yes, adapts annoyingly fast Yes, starts out with very low volume and adapts annoyingly fast

Basic quality Very good quality, full audio spectrum from ~70 Hz – 4000/8000 Hz

Poor, very inconsistent; sometimes very good sometimes a lot of clicks and pops. Spectrum limited at 3500 Hz.

Good quality, no audible artifacts but very limited spectral characteristics (300 Hz – 3100 Hz) plus some high frequency noise results in “thin” voice.

Packet loss and jitter performance

Very robust. 10 % packet loss gives good quality using any codec.

Very sensitive to packet loss and jitter both in terms of quality and delay. Quality poor already for 3 percent of packet loss.

Very sensitive to packet loss and jitter both in terms of quality and delay. Quality poor already for 3 percent of packet loss.

Delay Very low delay. 80 – 90 ms mouth to ear delay for perfect network. Adds almost no extra delay in jitter buffer when channel is poor.

Very high delay. Under perfect conditions one way delay on average 150 ms higher than Client 1 and even more for degraded networks. In worst case more than 500 ms longer delay than Client 1.

Very high delay. Under perfect conditions one way delay on average 100 ms higher than Client 1 and even more for degraded networks. In worst case more than 250 ms longer delay than Client 1.



• One of the clients consistently outperformed the other two

• The two worst ones showed similar behavior in most cases

– One of the clients had occasional pops and clicks under perfect network conditions

• This test showed how huge performance differences can be expected depending on the design team’s level of audio expertise


Summary

• High quality VoIP can be offered in the applications market today

• Lowest cost, shortest time-to-market, and best quality usually possible by purchasing proven VoIP solutions

• Beware of performance differences between solutions with seemingly identical feature lists

August 3-4, 2004 San Jose, CA Successfully Offering VoIP- Enabled Applications Services Jan Linden...

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