[January 27, 2020] Will be off to Dublin, Ireland in June 2020 for ICC 2020 as our paper on using aggregation as an indication of available bandwidth via purely passive estimations was accepted to the CQRM symposium. If I recall, it was roughly 20 years ago that I went to my first “big” conference attending ICC when it was in Helsinki, Finland. One out of two papers in on this go round to ICC 2020. Wicked cool paper by my former Ph. D student Dr. Lixing Song with an assist from my current Ph. D student Al-Amin Mohammed to get it over the finish line. Bit more on the paper after the break.
While I probably a bit biased, this by far is one of the cooler papers from Lixing’s dissertation. In short, we took the underlying fundamentals from our work on Fast Mobile Network Characterization for WiFi, namely that the frame aggregation that happens over higher-speed WiFi (aka 802.11e) means that frames get aggregated when congestion happens at the access point, and explore whether or not we can take the active approach that our prior work employed and do a complete passive approach to determine Available Bandwidth (AB). The short answer is that yes, we can, or we would not have a paper.
The coolest part of the work which unfortunately did not fit in this paper is that you can actually get a pretty good estimation of available bandwidth during the time period of a typical WiFi scan duration on a channel by observing the block ACKs (unencrypted) during that very, very brief 20 ms window. So basically, you can not only see if WiFi exists during the scan but also get a reasonable indication of the likely load on that particular channel. There are a host of caveats that come with that (some can be cleaned up with machine learning, it requires decoding of the block ACK packets, others require more thinking with beamforming) but hats off to Lixing as that finding is pretty magical IMHO. We have some fairly cool explorations on this from downtown Chicago as well as our good old University Relations tent. Hopefully with the feedback from the presentation at ICC, we can put in a fantastic submission to IEEE Transactions on Mobile Computing or a similar venue.
Title: A Passive Client Side Control Packet-based WiFi Traffic Characterization Mechanism
Authors: L. Song, A. Mohammed, A. Striegel
WiFi has emerged as a pivotal technology for delivering Quality of Experience (QoE) to mobile devices. Un- fortunately, exploding numbers of competing devices, potential encroachment by cellular technology, and dramatic increases in content richness deliver a more variable QoE than desired. Moreover, such variance tends to occur both across time and space making it an extremely difficult problem to debug. Existing active approaches tend to be expensive or impractical while existing passive approaches tend to be too narrow. In our paper, we propose a novel passive client-side approach that delivers efficient and accurate characterization by taking advantage of the properties of Frame Aggregation (FA) and Block Acknowledgements (BA). We show in the paper that we can accurately derive important characterization metrics such as airtime and throughput with only a minimal amount of observed BAs. We show through extensive experiments the validity of our approach and conduct validation studies in the dense environment of a campus tailgate.