?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.title=HACK%3A+Hierarchical+ACKs+for+Efficient+Wireless+Medium+Utilization&rft.creator=Salameh%2C+L&rft.creator=Zhushi%2C+A&rft.creator=Handley%2C+M&rft.creator=Jamieson%2C+K&rft.creator=Karp%2C+B&rft.description=WiFi%E2%80%99s+physical+layer+has+increased+in+speed+from%0D%0A802.11b%E2%80%99s+11+Mbps+to+the+Gbps+rates+of+emerging%0D%0A802.11ac.+Despite+these+gains%2C+WiFi%E2%80%99s+inefficient+MAC%0D%0Alayer+limits+achievable+end-to-end+throughput.+The+culprit%0D%0Ais+802.11%E2%80%99s+mandatory+idle+period+before+each+medium%0D%0Aacquisition%2C+which+has+come+to+dwarf+the+duration+of+a%0D%0Apacket%E2%80%99s+transmission.+This+overhead+is+especially+punishing%0D%0Afor+TCP+traffic%2C+whose+every+two+data+packets+elicit%0D%0Aa+short+TCP+ACK.+Even+frame+aggregation+and+block%0D%0Alink-layer+ACKs+(introduced+in+802.11n)+leave+signifi-%0D%0Acant+medium+acquisition+overhead+for+TCP+ACKs.+In%0D%0Athis+paper%2C+we+propose+TCP%2FHACK+(Hierarchical+ACKnowledgment)%2C%0D%0Aa+system+that+applies+cross-layer+optimization%0D%0Ato+TCP+traffic+on+WiFi+networks+by+carrying%0D%0ATCP+ACKs+within+WiFi%E2%80%99s+link-layer+acknowledgments.%0D%0ABy+eliminating+all+medium+acquisitions+for+TCP+ACKs%0D%0Ain+unidirectional+TCP+flows%2C+TCP%2FHACK+significantly%0D%0Aimproves+medium+utilization%2C+and+thus+significantly+increases%0D%0Aachievable+capacity+for+TCP+workloads.+Our+measurements%0D%0Aof+a+real-time%2C+line-speed+implementation+for%0D%0A802.11a+on+the+SoRa+software-defined+radio+platform+and%0D%0Asimulations+of+802.11n+networks+at+scale+demonstrate+that%0D%0ATCP%2FHACK+significantly+improves+TCP+throughput+on%0D%0AWiFi+networks.&rft.publisher=USENIX+Association&rft.contributor=Gibson%2C+G&rft.contributor=Zeldovich%2C+N&rft.date=2014&rft.type=Proceedings+paper&rft.language=eng&rft.source=+++++In%3A+Gibson%2C+G+and+Zeldovich%2C+N%2C+(eds.)+Proceedings+of+USENIX+ATC+%E2%80%9914%3A+2014+USENIX+Annual+Technical+Conference.++(pp.+pp.+359-370).++USENIX+Association+(2014)+++++&rft.format=text&rft.identifier=https%3A%2F%2Fdiscovery.ucl.ac.uk%2Fid%2Feprint%2F1452481%2F1%2FSalameh_HACK_Hierarchical_ACKs.pdf&rft.identifier=https%3A%2F%2Fdiscovery.ucl.ac.uk%2Fid%2Feprint%2F1452481%2F&rft.rights=open