Talk in Kobe: Information-theoretic problems in molecular and nanoscale communication

I'm in Osaka right now on a research trip, getting caught up on my many Japanese research contacts. One of the items on my agenda is a talk in Kobe on Monday afternoon, at the Kobe Advanced ICT Research Center, part of NICT. Details:

Title: Information-theoretic problems in molecular and nanoscale communication

Abstract: Recent advances in MEMS/NEMS and systems biology have made it possible to manufacture customized nanoscale devices, such as swarms of nanorobots. However, manufacturing is not enough: a significant remaining challenge is to solve the communication problem among these devices, which would allow them to coordinate their actions. Furthermore, the nanoscale communication environment is rather different from the systems that are usually studied by information and communication theorists. In this talk, I will introduce the nanoscale communication problem from an information-theoretic perspective, focusing on molecular communication, which mimics the way in which microorganisms communicate. Mathematical models and achievable-rate results will be presented, and important open problems will be discussed.

[Link for further details]

The ICC Deadline Fiasco

ICC is one of ComSoc's "flagship" conferences, and I try to submit something every year. It is more or less an annual tradition that the submission deadline is extended at least once. And although extensions are widely expected, they are never certain -- the conference organizers use the magic words (see here):

The Conference TPC has set realistic deadline dates and these may be rigorously adhered to.

This year, the original deadline was on Tuesday, September 6. Late in the evening of September 6, the first extension was officially announced by email, to September 19. And this morning, after working late into the night to get our paper finished, I noticed (not by email -- there has been no official announcement as yet -- but by logging in to EDAS) that the deadline has again been extended to September 28.

To be fair, the extensions have been useful.  We were having trouble getting good results out of our simulations, and without the first extension, we wouldn't have had a paper. But it is really annoying that the extensions were announced with only a few hours to go before the deadline. In the most recent case, I spent the weekend working late, and cleared my Monday schedule to make extra time to hit the deadline. For people like me with families and busy jobs, that causes a lot of tension.

I've never served any high-up role on a large TPC, so I don't know how extension decisions are made. But I don't think it's too much to ask that the extensions be announced with 48 hours' notice. It's not nice to let people ruin their weekends for no reason.

UPDATED: Paper at PIMRC: Hardware implementation of fractional cooperation

Update Sept. 15, 2011: PDF of the paper is here. Citation:

A. Calce, N. Farsad, and A. W. Eckford, “An experimental study of fractional cooperation in wireless mesh networks,” in Proc. 22nd Annual IEEE Symposium on Personal Indoor Mobile Radio Communications (PIMRC), Toronto, ON, pp. 990-994, 2011.

Original post follows.

I've got a paper at this week's IEEE PIMRC in Toronto:

A. Calce, N. Farsad, and A. W. Eckford
An experimental study of fractional cooperation in wireless mesh networks
Session: LPAN-8 (Multihop Cooperative Communication)
Date: Tuesday, September 13, 10:30-12:00
Room: Pier 9

Over the past five years I (and a bunch of other researchers, like Ravi and Nariman) have done a pile of work on fractional cooperation. Under this scheme, cooperation partners can just show up, relay as much of your transmission as they feel like (selecting symbols from your frame randomly), and leave -- with very little protocol and essentially no coordination. As chaotic as this sounds, we have always been able to show good results in simulation.

But with this paper, we put fractional cooperation in hardware for the first time: using some spare iMotes we had in the lab, my student Anthony managed to put together a small mesh network, showing that the system works as well in practice as it always has in MATLAB.

I'll post PDFs soon. Anthony will be giving the talk.

Designing microchannel molecular communication systems: Paper in Nano Communication Networks

I've got a new paper in Nano Communication Networks. (Of the five journal papers I've co-written on molecular communication, this is the last to be submitted and the first to be published ... quick review process FTW. But on the other hand, it's published by Elsevier.)

N. Farsad, A. W. Eckford, S. Hiyama, and Y. Moritani, “Quick system design of vesicle-based active transport molecular communication by using a simple transport model,” Nano Communication Networks, doi:10.1016/j.nancom.2011.07.003, 2011. [PDF]

In this paper, we're continuing our work on microchannel molecular communication (see also here), where molecular motors are used to transport the message-bearing molecules (MBMs).

Generating Lévy random variables from Gaussian (Updated)

Update August 17, 2011: Corrected a typo in the distribution.

Sometimes when I learn a neat mathematical trick, I write a blog post so I don't forget it.  This is one of those times.

If a random variable x has the Lévy distribution with parameters c and μ, then the pdf of x is given by

This distribution has applications in economics, finance, and physics. A famous statistical application is the first passage time of a Brownian motion: if w(t) is given by the Wiener process (with initial condition w(0) = 0), and x is the first time that w(x) = d, then x is Lévy distributed with c = d^2 and μ = 0.

Here's the trick, which is hard to find in the literature: let z represent a Gaussian-distributed random variable with mean 0 and variance v. Then 1/z^2 is distributed Lévy with c = 1/(2v^2) and μ = 0. In other words, if you have a good Gaussian random number generator, you can use it to quickly generate Lévy-distributed random variables!

This property is very briefly mentioned in the following paper (I had to do a bit more digging to verify it and get the right parameter values):

J. M. Chambers, C. L. Mallows, and B. W. Stuck, "A method for simulating stable random variables," J. Am. Stat. Soc., vol. 71, no. 354, pp. 340-344, Jun. 1976.

Talking about wireless: Elizabeth May's advice

Green Party leader and Member of Parliament Elizabeth May recently caused a stir by expressing concern over the safety of electromagnetic radiation. And here she is again this past weekend, taking an interview with her BlackBerry set to speakerphone, to avoid radiation exposure.

I'm not going to go into her concerns about safety (with which I largely disagree; if you're interested in the debate, an excellent summary is here). At the very least, May makes the valid point that there is no scientific consensus on wireless safety.  Fair enough!

But in her longer critique of wireless safety (found here on her blog), and by way of her subsequent actions, May gave some advice to those who are concerned about their exposure to EM radiation. Paraphrasing, she said this:

1. When using your phone, use speakerphone or text rather than holding it up to your ear.
2. You can use a smartphone, but don't keep it in your pocket.
3. At home, use a wireline network, not WiFi.
4. Don't get a Smart Meter.

What I will talk about is this: for people who are concerned about radio exposure (which doesn't include me), did Elizabeth May give good advice? It seems to me that #1 is good advice, #2 and #3 are questionable, and #4 is wrong to the point of embarrassing.

First Shannon Award Livetweet

Announced moments ago at the ISIT 2011 banquet in St. Petersburg, Russia: Congratulations to Abbas El Gamal on his well-deserved Shannon Award.

Livetweeted from the event by Johann Briffa: