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Shannon Chen
Shannon Chen

This document summarizes a research paper that proposes an exponential quantization (EQ) bandwidth allocation mechanism for voice over IP (VoIP) sessions. The mechanism is designed to be fair and improve overall user satisfaction. It models user satisfaction based on sending rate, divides rates into quantized levels, and adjusts rates up or down based on available bandwidth. Simulations show EQ supports more simultaneous calls and has higher accumulated user satisfaction than naive or Skype-based allocation schemes.

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Network and Systems Laboratory nslab.ee.ntu.edu.tw A Psychophysical Design towards Fair Bandwidth Allocation among VoIP Sessions Chien-nan Chen ꐽ Network and Systems Laboratory Graduate Institute of Networking and Multimedia National Taiwan University 2012/06/27 Advisors: Polly Huang and Hao-hua Chu Copyright ? 2012 1
Network and Systems Laboratory nslab.ee.ntu.edu.tw Copyright ? 2012 2
Network and Systems Laboratory nslab.ee.ntu.edu.tw Adaptation Psychophysics Sending QoS Rate Bandwidth Measurement Fairness QoE Rate Control Performance Assessment Copyright ? 2012 3
Network and Systems Laboratory nslab.ee.ntu.edu.tw Roadmap Mechanism Simulation ? QoS vs. QoE Design ? Sustainable ? Sending Rate vs. ? Rate control number of users ? Call-based Satisfaction ? Sending rate ? Accumulated simulation quantization satisfaction ? Comparison with Skype Modeling Analysis Copyright ? 2012 4
Network and Systems Laboratory nslab.ee.ntu.edu.tw Roadmap Mechanism Simulation ? QoS vs. QoE Design ? Sustainable ? Sending Rate vs. ? Rate control number of users ? Call-based Satisfaction ? Sending rate ? Accumulated simulation quantization satisfaction ? Comparison with Skype Modeling Analysis Copyright ? 2012 5
Network and Systems Laboratory nslab.ee.ntu.edu.tw Subjecting Codecs AMR-WB SILK ? Widely used in mobile ? The up-to-date codec devices used by Skype ? Nine coding rates ? Variable coding rates (6.6~23.8 kbps) (5.6~40.6 kbps) ? Two sampling rates ? Multiple sampling rates (8 and 16 kHz) (8, 12, 16, 24 kHz) ? ECC embedded, extra ? Wide spectrum of bits for redundancy qualities, extra bits for elaboration of details Copyright ? 2012 6
Network and Systems Laboratory nslab.ee.ntu.edu.tw Result Copyright ? 2012 7
Network and Systems Laboratory nslab.ee.ntu.edu.tw Model ? Both echoes the Weber-Fechners Law: logarithmic curves ? Different target use: stability (A) vs. flexibility (S) ? Mobile network vs. the Internet ? Error correction vs. Details elaboration ? Different spectrums of coding rates and resulting qualities (MOS) Copyright ? 2012 8
Network and Systems Laboratory nslab.ee.ntu.edu.tw Roadmap Mechanism Simulation ? QoS vs. QoE Design ? Sustainable ? Sending Rate vs. ? Rate control number of users ? Call-based Satisfaction ? Sending rate ? Accumulated simulation quantization satisfaction ? Comparison with Skype Modeling Analysis Copyright ? 2012 9
Network and Systems Laboratory nslab.ee.ntu.edu.tw Design The exact mathematic model Copyright ? 2012 10
Network and Systems Laboratory nslab.ee.ntu.edu.tw Design The exact mathematic model Take only the log property Copyright ? 2012 11
Network and Systems Laboratory nslab.ee.ntu.edu.tw Design The exact mathematic model Take only the log property Divide the sending rate into levels with exponential differences Copyright ? 2012 12
Network and Systems Laboratory nslab.ee.ntu.edu.tw Mechanism ? Sending rate is exponentially quantized into levels (which map to equally separated MOSs) ? A call is only allowed to transmit data at one of the level at any time ? Rate is raised to the highest level which the available bandwidth allows ? Rate is dropped to the next lower level when available bandwidth cannot sustain Copyright ? 2012 13
Network and Systems Laboratory nslab.ee.ntu.edu.tw Exponential Quantization (EQ) ? Simple and distributed ? Fairness: increases the number of calls served under the same network capacity ? Performance: increases the accumulated QoE of users served Copyright ? 2012 14
Network and Systems Laboratory nslab.ee.ntu.edu.tw Roadmap Mechanism Simulation ? QoS vs. QoE Design ? Sustainable ? Sending Rate vs. ? Rate control number of users ? Call-based Satisfaction ? Sending rate ? Accumulated simulation quantization satisfaction ? Comparison with Skype Modeling Analysis Copyright ? 2012 15
Network and Systems Laboratory nslab.ee.ntu.edu.tw 1. Fairness: Increase Users Case 1: Available bandwidth increasing (by B) ? Copyright ? 2012 16
Network and Systems Laboratory nslab.ee.ntu.edu.tw 1. Fairness: Increase Users Case 2: Available bandwidth decreasing ? Copyright ? 2012 17
Network and Systems Laboratory nslab.ee.ntu.edu.tw Fairer is Better ? VoIP, like any other interactive networking application, is a multi-party service ? Hoarding resource cannot improve your service quality High Rate Bad Tx Good Tx Quality Quality Good Rx Bad Rx Quality Quality Low Rate Copyright ? 2012 18
Network and Systems Laboratory nslab.ee.ntu.edu.tw 2. Performance: Increase QoE ? Rate change Normalized by the original rate Copyright ? 2012 19
Network and Systems Laboratory nslab.ee.ntu.edu.tw P-Fair and Accumulated QoE ? Copyright ? 2012 20
Network and Systems Laboratory nslab.ee.ntu.edu.tw Roadmap Mechanism Simulation ? QoS vs. QoE Design ? Sustainable ? Sending Rate vs. ? Rate control number of users ? Call-based Satisfaction ? Sending rate ? Accumulated simulation quantization satisfaction ? Comparison with Skype Modeling Analysis Copyright ? 2012 21
Network and Systems Laboratory nslab.ee.ntu.edu.tw Call-based Simulation ? We simulated 1,000~10,000 simultaneous calls in a backbone link with running background traffic ? The background traffic is adopted from [Fraleigh 03] which suggested a fractional Brownian motion with 124 Mbps average rate ? We simulated an OC-3 backbone link with 155 Mbps capacity Copyright ? 2012 22
Network and Systems Laboratory nslab.ee.ntu.edu.tw Comparison Three scenarios are simulated, where the calls adopt rate adaptation scheme of: 1. Exponential Quantization 2. Na?ve (baseline) Changes in available bandwitdth is evenly distributed to all calls, regardless of their qualities 3. Skype (reality check) By manipulating the bandwidth and recording the resulting rate of Skype, we manage to synthesize adaptation scheme of Skype Copyright ? 2012 23
Network and Systems Laboratory nslab.ee.ntu.edu.tw Number of Calls Served 3000 100% 90% 2500 80% Percentage of call supported Number of supported calls 70% 2000 60% 1500 50% 40% 1000 30% 20% 500 10% 0 0% Number of simultaneous calls Number of simultaneous calls Exponential Quantization Na?ve Skype Copyright ? 2012 24
Network and Systems Laboratory nslab.ee.ntu.edu.tw Accumulated QoE ? Problem: ITU never 8000 define MOS value for a 6000 forced dropped call 4000 Accumulate QoE 2000 ? According to our Na?ve Quant 0 model, MOS -2000 Skype approaches Cinf when -4000 bitrate is zero -6000 Number of simultaneous calls ? Our model outperforms Accumulated QoE when forced drop=-1 others when the dropped calls are given negative scores Copyright ? 2012 25
Network and Systems Laboratory nslab.ee.ntu.edu.tw MOS Distribution Exponential Quantization Naive Skype 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 1000 3000 5000 7000 9000 1000 3000 5000 7000 9000 1000 3000 5000 7000 9000 Number of simultaneous calls Number of simultaneous calls Number of simultaneous calls Copyright ? 2012 26
Network and Systems Laboratory nslab.ee.ntu.edu.tw Conclusion Aiming at devising a rate control mechanism for VoIP calls, we investigate: ? How users perceive voice quality at different sending rates with two popular speech codecs ? How one allocates the bandwidth such that we gain more users than losing more In result, we develop the simple and distributed EQ scheme that: ? Increase the user population (na?ve 334%; Skype 180%) ? Increase users satisfaction (na?ve +2.3; Skype +1.0) Copyright ? 2012 27

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  • 1. Network and Systems Laboratory nslab.ee.ntu.edu.tw A Psychophysical Design towards Fair Bandwidth Allocation among VoIP Sessions Chien-nan Chen ꐽ Network and Systems Laboratory Graduate Institute of Networking and Multimedia National Taiwan University 2012/06/27 Advisors: Polly Huang and Hao-hua Chu Copyright ? 2012 1
  • 2. Network and Systems Laboratory nslab.ee.ntu.edu.tw Copyright ? 2012 2
  • 3. Network and Systems Laboratory nslab.ee.ntu.edu.tw Adaptation Psychophysics Sending QoS Rate Bandwidth Measurement Fairness QoE Rate Control Performance Assessment Copyright ? 2012 3
  • 4. Network and Systems Laboratory nslab.ee.ntu.edu.tw Roadmap Mechanism Simulation ? QoS vs. QoE Design ? Sustainable ? Sending Rate vs. ? Rate control number of users ? Call-based Satisfaction ? Sending rate ? Accumulated simulation quantization satisfaction ? Comparison with Skype Modeling Analysis Copyright ? 2012 4
  • 5. Network and Systems Laboratory nslab.ee.ntu.edu.tw Roadmap Mechanism Simulation ? QoS vs. QoE Design ? Sustainable ? Sending Rate vs. ? Rate control number of users ? Call-based Satisfaction ? Sending rate ? Accumulated simulation quantization satisfaction ? Comparison with Skype Modeling Analysis Copyright ? 2012 5
  • 6. Network and Systems Laboratory nslab.ee.ntu.edu.tw Subjecting Codecs AMR-WB SILK ? Widely used in mobile ? The up-to-date codec devices used by Skype ? Nine coding rates ? Variable coding rates (6.6~23.8 kbps) (5.6~40.6 kbps) ? Two sampling rates ? Multiple sampling rates (8 and 16 kHz) (8, 12, 16, 24 kHz) ? ECC embedded, extra ? Wide spectrum of bits for redundancy qualities, extra bits for elaboration of details Copyright ? 2012 6
  • 7. Network and Systems Laboratory nslab.ee.ntu.edu.tw Result Copyright ? 2012 7
  • 8. Network and Systems Laboratory nslab.ee.ntu.edu.tw Model ? Both echoes the Weber-Fechners Law: logarithmic curves ? Different target use: stability (A) vs. flexibility (S) ? Mobile network vs. the Internet ? Error correction vs. Details elaboration ? Different spectrums of coding rates and resulting qualities (MOS) Copyright ? 2012 8
  • 9. Network and Systems Laboratory nslab.ee.ntu.edu.tw Roadmap Mechanism Simulation ? QoS vs. QoE Design ? Sustainable ? Sending Rate vs. ? Rate control number of users ? Call-based Satisfaction ? Sending rate ? Accumulated simulation quantization satisfaction ? Comparison with Skype Modeling Analysis Copyright ? 2012 9
  • 10. Network and Systems Laboratory nslab.ee.ntu.edu.tw Design The exact mathematic model Copyright ? 2012 10
  • 11. Network and Systems Laboratory nslab.ee.ntu.edu.tw Design The exact mathematic model Take only the log property Copyright ? 2012 11
  • 12. Network and Systems Laboratory nslab.ee.ntu.edu.tw Design The exact mathematic model Take only the log property Divide the sending rate into levels with exponential differences Copyright ? 2012 12
  • 13. Network and Systems Laboratory nslab.ee.ntu.edu.tw Mechanism ? Sending rate is exponentially quantized into levels (which map to equally separated MOSs) ? A call is only allowed to transmit data at one of the level at any time ? Rate is raised to the highest level which the available bandwidth allows ? Rate is dropped to the next lower level when available bandwidth cannot sustain Copyright ? 2012 13
  • 14. Network and Systems Laboratory nslab.ee.ntu.edu.tw Exponential Quantization (EQ) ? Simple and distributed ? Fairness: increases the number of calls served under the same network capacity ? Performance: increases the accumulated QoE of users served Copyright ? 2012 14
  • 15. Network and Systems Laboratory nslab.ee.ntu.edu.tw Roadmap Mechanism Simulation ? QoS vs. QoE Design ? Sustainable ? Sending Rate vs. ? Rate control number of users ? Call-based Satisfaction ? Sending rate ? Accumulated simulation quantization satisfaction ? Comparison with Skype Modeling Analysis Copyright ? 2012 15
  • 16. Network and Systems Laboratory nslab.ee.ntu.edu.tw 1. Fairness: Increase Users Case 1: Available bandwidth increasing (by B) ? Copyright ? 2012 16
  • 17. Network and Systems Laboratory nslab.ee.ntu.edu.tw 1. Fairness: Increase Users Case 2: Available bandwidth decreasing ? Copyright ? 2012 17
  • 18. Network and Systems Laboratory nslab.ee.ntu.edu.tw Fairer is Better ? VoIP, like any other interactive networking application, is a multi-party service ? Hoarding resource cannot improve your service quality High Rate Bad Tx Good Tx Quality Quality Good Rx Bad Rx Quality Quality Low Rate Copyright ? 2012 18
  • 19. Network and Systems Laboratory nslab.ee.ntu.edu.tw 2. Performance: Increase QoE ? Rate change Normalized by the original rate Copyright ? 2012 19
  • 20. Network and Systems Laboratory nslab.ee.ntu.edu.tw P-Fair and Accumulated QoE ? Copyright ? 2012 20
  • 21. Network and Systems Laboratory nslab.ee.ntu.edu.tw Roadmap Mechanism Simulation ? QoS vs. QoE Design ? Sustainable ? Sending Rate vs. ? Rate control number of users ? Call-based Satisfaction ? Sending rate ? Accumulated simulation quantization satisfaction ? Comparison with Skype Modeling Analysis Copyright ? 2012 21
  • 22. Network and Systems Laboratory nslab.ee.ntu.edu.tw Call-based Simulation ? We simulated 1,000~10,000 simultaneous calls in a backbone link with running background traffic ? The background traffic is adopted from [Fraleigh 03] which suggested a fractional Brownian motion with 124 Mbps average rate ? We simulated an OC-3 backbone link with 155 Mbps capacity Copyright ? 2012 22
  • 23. Network and Systems Laboratory nslab.ee.ntu.edu.tw Comparison Three scenarios are simulated, where the calls adopt rate adaptation scheme of: 1. Exponential Quantization 2. Na?ve (baseline) Changes in available bandwitdth is evenly distributed to all calls, regardless of their qualities 3. Skype (reality check) By manipulating the bandwidth and recording the resulting rate of Skype, we manage to synthesize adaptation scheme of Skype Copyright ? 2012 23
  • 24. Network and Systems Laboratory nslab.ee.ntu.edu.tw Number of Calls Served 3000 100% 90% 2500 80% Percentage of call supported Number of supported calls 70% 2000 60% 1500 50% 40% 1000 30% 20% 500 10% 0 0% Number of simultaneous calls Number of simultaneous calls Exponential Quantization Na?ve Skype Copyright ? 2012 24
  • 25. Network and Systems Laboratory nslab.ee.ntu.edu.tw Accumulated QoE ? Problem: ITU never 8000 define MOS value for a 6000 forced dropped call 4000 Accumulate QoE 2000 ? According to our Na?ve Quant 0 model, MOS -2000 Skype approaches Cinf when -4000 bitrate is zero -6000 Number of simultaneous calls ? Our model outperforms Accumulated QoE when forced drop=-1 others when the dropped calls are given negative scores Copyright ? 2012 25
  • 26. Network and Systems Laboratory nslab.ee.ntu.edu.tw MOS Distribution Exponential Quantization Naive Skype 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 1000 3000 5000 7000 9000 1000 3000 5000 7000 9000 1000 3000 5000 7000 9000 Number of simultaneous calls Number of simultaneous calls Number of simultaneous calls Copyright ? 2012 26
  • 27. Network and Systems Laboratory nslab.ee.ntu.edu.tw Conclusion Aiming at devising a rate control mechanism for VoIP calls, we investigate: ? How users perceive voice quality at different sending rates with two popular speech codecs ? How one allocates the bandwidth such that we gain more users than losing more In result, we develop the simple and distributed EQ scheme that: ? Increase the user population (na?ve 334%; Skype 180%) ? Increase users satisfaction (na?ve +2.3; Skype +1.0) Copyright ? 2012 27