Wednesday, October 29, 2014

HotNets 2014: Infrastructure Mobility: A What-if Analysis


Scribe notes by Athina Markopoulou.

Infrastructure Mobility: A What-if Analysis

Today’s wireless access networks cannot keep up with the demand. Today’s network infrastructure (APs, cell towers) is static while users may be mobile. The main idea proposed in this paper is to make the infrastructure itself mobile, in order to exploit diversity. There is a wide range of mobility options (tethering  - on the order of feet, ceiling railing - on order of meters, cell tower drones - order of km) and timescales to adapt. The authors put a disclaimer that they do not know the killer app yet and they consider this as a bottom-up enabling research. The author argued that their idea can be made practical through robots (“robotic WiFi”) and that it can provide compelling gains (in terms of SNR variation, throughput gains and other metrics, as evidenced by experimental results for micro-mini-macro mobility) without actually moving the APs much. He compared the approach to overprovisioning and argued that mobility is complementary to density. He also envisioned that the monitoring and control of mobility should be coordinated and optimized by the cloud.  He listed challenges including:  how to move the AP, how to coordinate this decision with other optimizations (e.g. channel selection, coding etc).

Q&A (during panel discussion, some of them addressed to all papers)

Q : If you make the AP mobile, things may break down (physically)easier. How do you tradeoff between higher throughput and higher chance of failure.
A: These risks, as well as psychological discomfort, are increasing with the use of robots  in our life.

Q: The question is not about psychology aside, it is about reliability.
A: We can optimize for different utility functions. So far, we optimized throughput, but we could include reliability in our objective function.

Q: What is your baseline for comparison? Could you get the same benefits by simply using MIMO?
A: We are currently using a single antenna. Mobility is complementary to MIMO.

Q: All 3 papers require help from participants. How reliable are these participants and how sensitive is the outcome to optimal choices?
A: The precise placement of AP is not critical, since there is a lot of diversity, and many positions of the AP are good enough.

Q: Rather than mobilizing the AP, we could move the antennas, etc.
A: Yes, but restricted mobility means less opportunity.

Q: You seem to need a lot of computation in real time. Where should this computation be done?
A: the computation bottleneck is the search space. It can be done at the local AP. In case of multiple APs, it can happen on the cloud.