Link Rate Estimation and Adaptation for VoWLAN with Mobility Student: Yann-Huei Li Advisor: Dr. Ying-Dar Lin 2019/5/18 Speed Lab

Outline Background Problem statement Related works Solution VoWLAN – Voice over WLAN Sustainable Rate Metrics – MOS and Medium Consumption Problem statement Related works Solution Estimating Sustainable Rate: RTQ Adapting Retransmission Rate: RTQ Performance Evaluation Conclusions Future Works Reference 2019/5/18 Speed Lab

Background – VoWLAN: VoIP over WLAN Concerns of VoWLAN Transmission quality? MOS Service capacity? Medium consumption Rate selection (for quality maintenance): Sustainable rate determination Initial & retransmission rate selection 2019/5/18 Speed Lab

Background – Metrics: MOS and Medium Consumption MOS (Mean Opinion Score): Quality of received media after transmission. Range 1 to 5, 5 = best quality. Range for VoIP: 3.5~4.2 Medium Consumption (MC): (function) Lower MC --> more capacity Tradeoff between link rate & MC 2019/5/18 Speed Lab

Background - Sustainable Rate Sustainable rate (Rs): the transmission rate with satisfied quality and highest utilization of the channel. Let Rt represent current rate, If Rt > Rs: error rate↑, retransmissions↑, MC↑, MOS↓. If Rt < Rs: MOS is fine, but MC↑. Value of Rs varies due to mobility 2019/5/18 Speed Lab

Problem statement Environment: Goal: VoWLAN with mobility Selecting the rate closest to sustainable rate, i.e. satisfying certain MOS with minimum MC, as fast as possible. Current rate unsuitable, select better rate. Rate adaptation based on Traffic Quality (RTQ). 2019/5/18 Speed Lab

Initial rate selection Related Works Passive Active # of Succ. TX # of Failure TX RTT Congestion Medium condition Initial rate selection Sample rate Increase rate ARF, Onoe (with credit), PLC Vega like ARC Decrease rate ARF, Onoe (with credit) Maintain rate PLC Notation: ARF: Auto Rate Fallback PLC: Packet Loss Classification ARC: Audio Rate Control 2019/5/18 Speed Lab

Step 1 – Sustainable rate discovery (RAVTQ) By simulations, Given factors: distance (SNR), Link rate R Calculated factors: MOS value, MC (in % of the medium capacity) MC MOS factor Link rate (at fixed voice codec) 1Mbps 2Mbps 1Mbps Link rate (at fixed voice codec) 2Mbps Distance Distance 2019/5/18 Speed Lab

Step 1 – Sustainable rate discovery (RAVTQ) (cont.) Need to find R, such that At certain SNR, MOS = 3.5~4.2 and minimum MC Link Rate (in Mbps) SNR 2019/5/18 Speed Lab

Simulation - Input Traffic NS-2’s traffic input requirement: Packet send time Packet size Popular VoIP codec: G.711: 8kHz sampling, 32kbps stream G.723.1: 8kHz sampling, 5.6/6.3kbps stream G.729: 8kHz sampling, 8kbps stream CBR, Exponential on/off 2019/5/18 Speed Lab

Rates’ MOS vs Distance 2019/5/18 Speed Lab

Rates’ MOS vs SNR 2019/5/18 Speed Lab

Rates’ MC vs Distance 2019/5/18 Speed Lab

Rates’ MC vs SNR 2019/5/18 Speed Lab

Sustainable Rate VS Distance 2019/5/18 Speed Lab

Sustainable Rate VS SNR - Rs(SNR) 2019/5/18 Speed Lab

Step 2 – Initial & Retransmission rate selection (RTQ) Initial rate = Rt = Rs(SNR) Retransmission rate: Rate adjustment based on current MOS. 2019/5/18 Speed Lab

Performance Evaluation - Fixed distance 2019/5/18 Speed Lab

Performance Evaluation - with Mobility 2019/5/18 Speed Lab

RBAR thresholds 2019/5/18 Speed Lab

Rate Variance with Mobility 2019/5/18 Speed Lab

MOS Variance with Mobility 2019/5/18 Speed Lab

Conclusions Fixed distance: Mobility condition: RAVTQ MOS ≒ ARF MOS RAVTQ MC < ARF MC (mostly) Mobility condition: RAVTQ MC < ARF MC 2019/5/18 Speed Lab

Future Works - MOS of Different Codec 2019/5/18 Speed Lab

Future Works – MC of Different Codec 2019/5/18 Speed Lab

Future Works - Comparison of Average Rate under multiple MS nodes 2019/5/18 Speed Lab

Reference T. Branskich, N. Smavatkul, and S. Emeott, “Optimization of a Link Adaptation Algorithm for Voice over Wireless LAN Application,” IEEE Communications, 2005. C. W. Huang, A. Chindapol, J. A. Ritcey, and J. N. Hwang, “Link Layer Packet Loss Classification for Link Adaptation in WLAN,”. S. Pal, S. R. Kundu, K.Basu, and S. K. Das, “IEEE 802.11 Rate Control Algorithms: Experimentation and Performance Evaluation in Infrastructure Mode,”. A. Trad, Q. Ni, and H. Afifi, “Adaptive VoIP Transmission over Heterogeneous Wired/Wireless Networks,” 2004. 2019/5/18 Speed Lab

Reference (cont.) M. Lacage, M. H. Manshaei, and T. Turletti, “IEEE 802.11 Rate Adaptation: A Practical Approach,” Oct 2004. J. Matta, C. Pepin, K. Lashkari, and R. Jain, “A Source and Channel Rate Adaptation Algorithm for AMR in VoIP Using the Emodel,” June 2003 M. Bandinelli, F. Chiti, R. Fantacci, D. Tarchi, G. Vannuccini, “A Link Adaptation strategy for QoS support in IEEE 802.11e-based WLANs,” IEEE Communications, 2005 Z. Qiao, L. Sun, N. Heilemann, and E. Ifeachor, “A new method for VoIP Quality of Service Control use combined adaptive sender rate and priority marking,” IEEE Communications, 2004 2019/5/18 Speed Lab