Anticipatory wireless bitrate control for blocks

Abstract

We present BlockRate, a wireless bitrate adaptation algorithm designed for blocks, or large contiguous units of transmitted data, as opposed to small packets. Our work is motivated by the observation that recent research results suggest significant overhead amortization benefits of blocks. Yet state-of-the-art bitrate algorithms are optimized for adaptation on a per-packet basis, so they can either have the amortization benefits of blocks or high responsiveness to underlying channel conditions of packets, but not both. To bridge this disparity, BlockRate employs multiple bitrates within a block that are predictive of future channel conditions. In each feedback round, BlockRate uses a history-based scheme to predict the SNR for packets within the next block. In slow-changing scenarios as under pedestrian mobility, BlockRate uses a simple linear regression model to predict the SNR trend over the next block. In fast-changing scenarios as under vehicular mobility, BlockRate uses a path loss model to capture more significant SNR variations within a block. We have implemented a prototype of BlockRate in a commodity 802.11 driver and evaluated it via deployment on an indoor mesh testbed as well as an outdoor vehicular testbed. Our evaluation shows that BlockRate achieves up to 1.4× and 2.8× improvement in goodput under indoor and outdoor mobility respectively.