voip on the iphone: imagine the possibilities jan linden, vp of engineering
Post on 20-Dec-2015
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VoIP on the iPhone: Imagine the PossibilitiesJan Linden, VP of Engineering
VoIP on the iPhoneOutline
• Market trends• Technology trends• Mobile VoIP challenges• Solutions and recommendations
Evolution of IP Voice andVideo Processing
Solutions Designed Specifically for VoIP
Advanced Mobile and Multimedia Capabilities
PSTN Solutions Adapted for VoIP
Mobile Market Trends
• Fixed Mobile Convergence– Mobile phone increasingly perceived as a computer
• Advanced operating systems such as Apple OSX are making this a reality
– Users expect to access the same applications available across multiple platforms
• Increased accessibility and affordability– Network operators are introducing new pricing models to
encourage uptake of data driven services and applications• IP networks enable more cost effective transport
– Handset prices declining• iPhone 3G half the price of 1st Generation
Mobile Technology Trends
• Migration from legacy cellular to next-gen networks– Allows for faster data connection
• Growth of Smartphone adoption– iPhone and other dual-mode phones provide greater flexibility in
connecting to available networks– All-in-one devices able to run multiple applications efficiently
• Consumers can place calls and receive data simultaneously
• Development of 3rd Party Applications– Operating systems, like the Apple OS X, more conducive to
advanced 3rd party applications – VoIP over mobile in high demand
The iPhone as a VoIP Platform• iPhone most VoIP friendly phone on market…
– Open APIs for easy development– Sufficient CPU resources– Support of wideband codecs– Intuitive UI makes for simple navigation between applications– Demand for 3rd party apps is higher than other phones
• …but strengths present unique challenges– Running too many applications can drain resources– Usage scenarios can negatively impact voice quality
With the right voice processing software, developing VoIP applications is a cinch!
Technology Challenges – Network Connections• IP Networks
– Latency– Jitter – Packet loss
• Wireless connections– Low signal strength– Interference from users in
same or neighboring frequencies
– Available bandwidth varies– WiFi access point
bottlenecks
Technology Challenges
• Device Limitations– Limited processing power– Battery life– Data intensive applications can
cause jitter
• Mobile Environments– Tend to have excessive
background noise– Hands Free operation
enhances acoustic echo
Impact of IP Networks
Delay
Packet Loss
Network Jitter
Impact of IP Networks – Latency
• Major effect is “stepping on each other’s talk”
• Usage scenario affects annoyance factor – higher delay can be tolerated for mobile devices
• Long delays make echo more annoying
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Sources of Latency
• Codec• Capture• Playout• Network delay• Jitter buffer• OS interaction• Transcoding
A/DPre-processing
Speech encoding
IP interface
D/APost-processing
Speech decoding
Jitter buffer
IP Network
A/DPre-Processing
Speech Encoding
IP Interface
D/APost-Processing
Speech Decoding
JitterButter
IP Network
Impact of Latency on Voice Quality
• ITU-T (G.114) recommends:– Less than 150 ms one-way delay for most applications (up to 400
ms acceptable in special cases)• Users have become accustomed to longer delays
– Still, low delay very important for high quality
Data from ITU-T G.114
1
2
3
4
0 250 500 750
One-way transmission time [ms]
Mea
n O
pin
ion
Sco
re
Impact of IP Networks – Packet Loss and Jitter
• Packet Loss– Occurs due to flushed buffers in network nodes– Same effect if packets are too late to be used– Smooth concealment necessary
• Network Jitter– Transmission time differs for each packet– Jitter buffer necessary to ensure continuous playout– Trade-off between delay and quality
Technology Challenges – Mobile Environments
• Background Noise– Environments inherently noisy– Usage scenarios can make
differentiating between speech and noise difficult
• Acoustic Echo– Speakerphone operation common for iPhones– Micropohone and speaker close– High delay in VoIP makes echo more prominent
Technology Challenges – Devices• Limited Resources
– Size limits processing power– Battery life also limited
• VoIP Friendliness– Many smartphones limit access to
soundcard– Device buffers add latency– Clock drift
• Too much of a Good Thing– Running too many applications can drain
resources– Multiple applications accessing network
can result in jitter
VoIP Design Considerations
QualityCost
Speech Quality
Time to Market
Flexibility
Ease of Use
Network ImpairmentsPower Consumption
Device Considerations
Cost
Signaling
Features
Infrastructure
Coping with Network Degredation
Power Consumption
Hardware Issues (Processor, OS, Acoustics, etc.)
Echo Cancellation
Additional Voice Processing Components
Environment – Background Noise, Room Acoustics,
etc.
Speech Codec
VoIP DesignChallenges
Network
Codec
Hardware
Echo Power
Voice Environment
Mobile VoIP Design Considerations
Speech Codec
Speech Codec
Packet-loss Robustness
Memory
Sampling Rate
Complexity
Delay
Bit-rate
Quality
Complexity
Bit-rate
• Many conflicting parameters affect choice of codec
• Determines upper limit of quality
• Support of several codecs necessary
– Interoperability
– Usage scenario
• IPR issues a significant concern
Input Signal Robutness
Audio Bandwidth Effect on Quality
• Better than PSTN quality is achievable in VoIP– Utilizing full 0 – 4 kHz band in narrowband– Wideband coding offers more natural and crispier voice
Frequency
4 kHz 6.4-7.0 kHz
GIPS Narrowband Speech
Std Wideband Speech(e.g. G.722.2)
CD -Audio
Std Narrowband Speech Implementation (PSTN)
200 - 3400 Hz
GIPS Wideband Speech
3,4 22.1 kHz8 kHz
Quality
iPhone Specific Challenges
• Applications cannot run in the background• Audio HAL APIs (regular APIs) not available on iPhone. (As on
Mac.) Very iPhone specific solution had to be designed• Must consider change of audio route (e.g. headset in/out) and
handle this• Wideband audio not available via built-in mic
Recommendations
• IP Networks– No need for dedicated bandwidth if solution includes high
performance:• Bandwidth management• Robust codec framework
– Low latency achieved by efficient jitter buffer
• Audio– High quality audio is crucial
• Users expect the same quality they experience on the PC
• Optimized Solutions– Efficiency for ARM processors on iPhones– Reduce CPU constraint and increase battery life
Recommendations
• Adaptive Jitter Buffer and PLC– Manage up to 30% packet loss– Adapt to network busts and excessive mobile jitter
• Codecs Designed for IP Networks– Work in tandem with jitter buffer to overcome packet loss– Can deliver Wideband experience– Robust and bit-rate adaptive codecs necessary
• Efficient use of the total available bandwidth• GIPS iLBC already in the iPhone, GIPS iSAC and other wideband
codecs provide even better user experience
• Aggressive Voice Quality Enhancement– Detect and cancel background noise– Suppress acoustic echo
Recommendations
• VoiceEngine Mobile for iPhone– Comprehensive package of voice processing components
– Handles delay, jitter, packet loss and mobile environments– Optimized for iPhone and Smartphones
– Efficient solution reduces CPU demands– Flexible and easy to integrate