Sunday, April 24, 2011

Seminar in Ottawa: Information-theoretic problems in molecular and nanoscale communication

I'll be in Ottawa this Thursday and Friday: Thursday I'll be the external examiner at the Ph.D. defense of one of Yongyi's students, and Friday I'll be giving a seminar on some of my recent molecular communication work. Details follow.

Time: Friday, April 29, 11 AM

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.

Tuesday, April 19, 2011

A critic speaks

Personally, I have never been able to convince myself that the Metropolitan Opera broadcasts are cultural in any deep sense of the word. The broadcasting of ludicrous Nineteenth Century melodrama, accompanied by music which is emotionally powerful but frequently of staggering vulgarity, and projected by means of acting which often falls below the level of a high school literary society's play, is cultural only on a very special level. I am devoted to opera and never miss a performance if I can help it, but if I were going to broadcast something that was cultural, I would certainly not choose Lucia, La Traviata or Tosca.

Yours sincerely,
Robertson Davies

(I was a resident at Massey College during my Ph.D., where Davies was the founding master. [Source, via])

Monday, April 11, 2011

Paper at MoNaCom

I had a paper in the MoNaCom workshop, which was held on Sunday afternoon in Shanghai, in conjunction with Infocom 2011.  Satoshi presented the paper; unfortunately I had to miss what looked like a very interesting workshop.

In our earlier work on microchannel molecular communication, we noticed that naive placements of the transmitter and receiver were suboptimal.  However, when we tried to optimize these placements, we ran into a problem: our high-fidelity simulation of the molecular motors was computationally intensive, so it would have taken forever to run the huge number of simulations required in the optimization problem.  Addressing this problem, our paper gives a quick-to-simulate, though approximate, model for motor trajectories, and applies it as a design tool for optimizing information rates in microchannels.

N. Farsad, A. W. Eckford, S. Hiyama, and Y. Moritani, "A simple mathematical model for information rate of active transport molecular communication," in Proc. 1st IEEE International Workshop on Molecular and Nano-Scale Communications, Shanghai, China, 2011. [PDF]

Friday, April 8, 2011

Random matrices and the Kronecker product

The distribution of a zero-mean, jointly Gaussian column vector x is pretty basic stuff in probability: we get the covariance matrix R, given by

where the superscript T represents transposition. Then we find the probability density function (pdf)

where k is the number of elements in x.

But suppose you have not a random vector, but a jointly Gaussian, zero-mean k by k random matrix X. How do you express the pdf compactly? And can you compactly represent the pdf of matrix multiplications of X?

Friday, April 1, 2011

Is my salary any of your business? (Updated)

UPDATE: Doorey has an interesting take on the sunshine list.

For the first time, I made it onto Ontario's salary disclosure list.  I won't link to it, but a trivial amount of Googling would lead you to find out exactly what I earned last year.

On the one hand, my employer is a public institution, and I agree that the public deserves to know how their money is being spent.  And there are some individuals, like university presidents and senior executives of public corporations, whose compensation packages are large, and who negotiate their employment contracts individually; these packages should be on the public record.  But I'm a middle-ranked professor with no administrative authority, and my pay is set by collective bargaining. Do you need to know exactly how much I, personally, get paid?

The disclosure list would perform its function if it was published as it is today, but with names redacted:  the public would know, in general, how much professors and other civil servants get paid.  I don't see what extra public good is served by printing my name, which is a significant invasion of privacy.

And a memo to the local papers: "Many more public servants earning six figures" is not news, although it certainly provides inflammatory fodder for people who think public servants are all fat cats helping themselves at the public trough.  Salaries naturally go up as a result of cost-of-living increases, which track inflation, so it would be a huge surprise if the list did not grow.  A much better question, whether the size of the list is growing at the expected rate given inflation, is not answered by any of the media reports I read.