1. 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

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

3. 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

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

5. 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?

6. 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])

7. 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

8. 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”