Subject: [T2TRG] Follow-up: Inter-network Coexistence in the Internet of Things

From: L M Feeney <[email-masked]>
Date: Tue, 29 May 2018 11:32:26 +0200

Dear all,

This is the promised follow-up message summarizing how the new draft
incorporates some of the helpful feedback from the London meeting.

Goal is to clarify possible roles for T2TRG/IETF, with main changes in
sections 3 + 4.   Sections 4.1 and 4.4 are largely new and I recommend
them to those already familiar with the document.

I've marked responses to specific comments (thank you) and apologize for
any missing attributions.

Further comments and discussion most welcome.

***  more discussion of issues around performance evaluation (section 4.1)

--- Comment from Ted Hardie about understanding what features are
important for a testbed for evaluating inter-network interactions. Eliot
Lear had a related question what data needs to be harvested. Comment
from Eve Schooler about hackathon and realistic environments.

*** more clarity between concrete activity and speculative research
(sections 3, 4.2, 4.3)

The former includes performance evaluation and informing ongoing
protocol development.  Text clarifies roles of PHY/MAC and higher layer
protocols (noting that some IETF protocols are quite close to the MAC).
Higher layer protocols need to behave as well as possible in the
presence of interference, not exacerbate it, and (where possible)
mitigate it.

The latter is very speculative about possibility of new protocols for
explicit coordination between administratively unrelated networks.

--- Comments from Juan Carlos Zuniga and others; some discussion at the
side meeting about causes/mitigations (synchronization, keep-alive) is
better suited to another document.

*** new section on role of spectrum regulation (section 4.4)

Spectrum regulation doesn't mandate specific protocols. Any high layer
coordination protocol needs incentive and buy-in.

New regulations such as LBT may help. But by its nature it has to be
much more prescriptive than simple transmit power or channel utilization
limits.  This appears to lead to additional risk of incompatibilities.
There is some research literature, but it would be helpful to understand
this more.

My impression is that the LTE offloading is being extremely careful
about this; it's a major step and there would be repercussions if it
went badly wrong.  Whether this is equally true for smaller IoT
solutions isn't clear.

There is also additional discussion of LPWAN and especially spectrum
regulation. The diversity in sub-GHz spectrum is huge: Two and even
three orders of magnitude in bitrate, communication range.  The PHY
layers are intended to be super resilient, but there is a lot still to
understand here.

IETF has a strong interest in ensuring that regulation helps use the
channel efficiently, but isn't so prescriptive that it constrains
protocol unnecessarily or strangles innovation.

*** comment from Gabriel Montenegro about the role of spectrum
regulation and LBT (listen-before-talk) requirements, comment from Juan
Carlos Zuniga on need for buy in,  Alexander Pelov about LPWAN

Best regards,
Laura

----
Laura Marie Feeney
Division of Computer Systems
Uppsala University, Sweden

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