NSF Ultra Low Latency in Wireless Workshop - Technology Shivendra Panwar PhD work of Menglei Zhang and Nicolas Barati Marco Mezzavilla, Sundeep Rangan, Jing Zhu, Thanasis Korakis, Amir Hosseini, Ted Rappaport, Michele Zorzi

Low latency in the past Will history repeat itself… Priority queuing – why is it rarely turned on? IEEE 802.4, IEEE 802.11e, IEEE 802.11 PCF…. But, MPLS TE widely deployed

Is this time different? We have gone from a requirement of ~100 ms to ~1 ms From 20,000km to 200km over fiber For cellular this itself means that the core network (EPC in 4G) will have to be re-engineered

WiFi IEEE 802.11ac, ad, ax…. Promise of bandwidths up to 10Gb/s Is CSMA finally dead?

5G Cellular Air link: Massive MIMO, mmWave, Full Duplex NGMN White Paper promises 1 ms delay But…US carriers are proceeding cautiously Fixed wireless access will be the initial 5G application Do we need high bandwidth, low latency and mobility simultaneously?

Cross-layer Issues for mmWave Gigabit/s bandwidths, but very intermittent mmWave also needs directional transmission to work Buildings, body movement can lead to a drop in bandwidth First link technology with high bandwidth and intermittent drops in bandwidth. A challenge for networking researchers. Initial access to form a connection within 1 ms is a requirement (see paper by Nicolas Barati et al. [1])

TCP for single pedestrian UE scenario (Menglei Zhang et al. [2]) The blockage events were simulated by superimposing the real human blockage measurement traces measured with our sounding equipment over the channel models. Drop-tail Large congestion window High buffer occupancy and delay Human CoDel Low buffer occupancy and delay Rate degradation Dynamic RW Best performance

References [1] N Barati, SA Hosseini, M Mezzavilla, S Rangan, T Korakis, SS Panwar and M Zorzi, “Initial Access for Millimeter Wave Cellular Systems,” IEEE Transactions on Wireless Communications , accepted to be published. [2] M Zhang , M Mezzavilla, J Zhu, S Rangan, SS Panwar, “The Bufferbloat Problem over Intermittent Multi-Gbps mmWave Links”