U NIVERSITY OF M ASSACHUSETTS, A MHERST Department of Computer Science Anticipatory Wireless Bitrate Control for Blocks Xiaozheng Tie, Anand Seetharam, Arun Venkataramani, Deepak Ganesan, Dennis Goeckel University of Massachusetts Amherst

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 2 Wireless bitrate control Goal: To optimize goodput by adapting effective sending rate to channel quality Data packet Channel feedback  6Mbps 1Mbps 2Mbps Bad channel Good channel Good channel

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 3 Blocks reduce overhead Blocks = Large batch of packets E.g., 64KB MAC block in n 1MB block in Hop transport [NSDI’09] Packet Ack  DIFS Backoff SIFS X X Packet transmission DIFS Backoff X X Block transmission SIFS Timeout Backoff DIFS Backoff

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 4 Responsiveness vs. overhead 6Mbps 1Mbps 2Mbps X X X Block transmission  Low responsiveness  Low overhead 6Mbps Packet bitrate control  High responsiveness  High overhead Can we have both high responsiveness and low overhead?

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 5 Outline Why anticipatory bitrate control BlockRate design and implementation Evaluation Conclusion

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science Overhead vs. responsiveness (1) Overhead matters more in static settings 6 (Packet-based) (Block-based) 1.6x [Mobisys’08]

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 7 Overhead vs. responsiveness (2) Both overhead and responsiveness matter in mobile settings 30mph Data 2x  6Mbps  6Mbps 12Mbps  12Mbps Charm+Block Oracle+Block 1.7x

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 8 Outline Why anticipatory bitrate control BlockRate design and implementation Evaluation Conclusion

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 9 Anticipatory bitrate control Anticipatory = Selecting multiple bitrates predictive of future channel conditions. Bitrate control for packets 6Mbps Anticipatory bitrate control for blocks 6Mbps 12Mbps Good channel 6Mbps 12Mbps

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 10 Predict SNR trend: Slow-changing Linear regression model Assumes SNR linearly varies with time in slow- changing scenarios Static Pedestrian (1m/s)

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 11 Predict SNR trend: Fast-changing Path loss model Assumes SNR logarithmically varies with distance in fast-changing scenarios 30mph SNR(d)= SNR(d 0 ) – 10αlog(d/d 0 )

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 12 BlockRate design summary 30dB 40dB 6Mbps  6Mbps 12Mbps 2. Lookup SNR-Bitrate table to select anticipatory bitrate 1. Predict future SNR based on mobility pattern SNRBitrate …… 40dB12Mbps …… Linear regression Path loss Slow mobility? Yes NoNo

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 13 SNR-Bitrate table Maintains bitrate that maximizes goodput at each SNR

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 14 Outline Why anticipatory bitrate control BlockRate design and implementation Evaluation Conclusion

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 15 Experimental setup Vehicular Pedestrian Static V-to-V: 20 buses V-to-AP: 2 cars Mesh:16 MacMini nodes 2 mobile laptops ns3 simulation Pedestrian

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 16 Performance in V2V testbed BlockRateCharm+BlockCharmSampleRate #V2V contacts x

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 17 Performance in V-to-AP testbed 30mph Data 1.6x

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 18 Performance in pedestrian mobility Pedestrian mobility trace-driven simulation in ns-3 (Uses PHY-hint) (Uses movement-hint)

U NIVERSITY OF M ASSACHUSETTS A MHERST Department of Computer Science 19 Conclusion State-of-the-art bitrate control schemes must pick one: low overhead or high responsiveness BlockRate achieves both benefits Anticipatory bitrate control using blocks reduces overhead while being responsive Thank you!