On rejection

Early on, a major issue with evolutionary theory was the lack of "early" animal fossils: complex animals, like trilobites, were well known in the Cambrian fossil record, but there was no evidence of their evolutionary precursors.

All this changed in 1946, when geologist Reginald Sprigg made a startling discovery. The New York Times has the story:

Reginald Sprigg, a geologist for the South Australia government, was checking out some old mines in the Ediacaran Hills of the Flinders Range several hundred miles north of Adelaide. Sprigg noticed some striking disc-shaped impressions up to four inches in diameter on the exposed surfaces of rocks nearby. Sprigg interpreted the patterns as the [pre-Cambrian] fossil remains of soft-bodied creatures like jellyfish or their relatives.

The kind of career-making discovery a young scientist could only dream of! But the story goes on (emphasis added):

When Sprigg first showed the imprints to leading authorities, they dismissed them as artifacts made by the weathering of the rocks. ... Later that year, when Sprigg found the frond-like forms he called Dickinsonia, he was certain that such geometrical impressions could have been made only by living creatures. But despite their potential importance, Sprigg’s discoveries were ignored at an international geology meeting and his paper describing the fossils was rejected by the leading journal [Nature]. Sprigg moved on to other, more rewarding pursuits in the oil, gas, and mining industries.

It took another decade for Sprigg's earth-shattering contribution to be widely recognized. Something to keep in mind both as an author and as a reviewer.

The other Blackwell channel

In memory of the late David Blackwell (see obits here and here), I'd like to talk about the Blackwell channel. Not this one, which is the one everyone thinks of, but the other one -- otherwise known as the trapdoor channel, the billiard-ball channel, or the chemical channel. (Find me another information theorist with two channels named after them.)

The channel works like this. Information is transmitted using coloured balls (red to represent 0 and black to represent 1, say). The "channel" is a bag containing a single (red or black) ball. At each channel use, the transmitter inserts a single ball into the bag, and the receiver then removes one of the two balls, selecting uniformly at random between the two. It should be obvious that this model can be generalized in various ways.

Blackwell proposed this model in his 1961 book as an example of a channel with memory: the channel output is clearly dependent on prior channel inputs. Remarkably for such a simple model, capacity is still unknown. As far as I know, the best result is the channel capacity with feedback, found by Permuter et al. to be the logarithm of the golden ratio. Since the transmitter is free to disregard the feedback, this must also be an upper bound on the capacity without feedback.

This channel also admits zero-error codes. For example, even if the initial channel state is unknown, a threefold repetition code (i.e., red, red, red or black, black, black) can be decoded without errors, since there can be at most one wrong-coloured ball at the output; thus, the zero-error capacity is (trivially) at least 1/3. Zero-error capacity is also an open problem for this channel.

Why the rage against Engage?

The Engage grant is a new NSERC initiative for kick-starting collaborations between industry and academia. The main features of these grants are: short duration (6 months max), limited value ($25,000 max), industry focus (an industrial partner, who will own all the IP, is mandatory), and quick decisions (6 week turnaround, which is only possible with no peer review). I found out on Friday that my Engage proposal would be funded; I'll write more about it as we publish, but the project is in the broad area of fractional resource sharing for femtocells, similar to the earlier work we've done on fractional cooperation (e.g., 1, 2, 3).

So imagine my surprise to learn that the CAUT has come out strongly opposed to Engage, passing the following resolution:

NSERC must remain a granting council that enables peer-reviewed fundamental research. Whereas linkages between industry and universities consistent with academic freedom are possible, the targeting of granting council funds to private industry’s needs erodes Canada’s capa­city to contribute to the general advancement of knowledge in the public interest.

Of course I'm biased because I'm a recipient of NSERC's largesse under this program. But CAUT's position is bizarre on a number of counts. First, it treats all scientific research as equally separate from industrial applications. In wireless communications, there is no tension between the "general advancement of knowledge" and "industry's needs" -- they are one and the same, because essentially all of the applications are industrial. Second, it assumes that only non-industrial research is in the public interest. Again, in wireless, it's the opposite -- the type of research that has a real impact, say by improving your mobile's performance (like this), is coming out of industrial labs, not out of academia. Third, CAUT has completely missed the point of this program: its limited scope, duration, and funding makes it only useful as a door-opener, to give a researcher an easy way to approach a company, and to give that company a low-risk way to say yes to a collaborative project. What's more, Engage grants can only be approved for companies and researchers that have never collaborated before, so this granting program can't be part of some great outsourcing of corporate R&D to universities.

My view on these projects is broadly held across engineering faculties. So CAUT is misunderstanding its membership by opposing the Engage grant, and promoting a "pure" vision of academia that is potentially harmful in some disciplines.

Molecular communication using Brownian motion with drift

I'm third author on this paper, and Sachin and Ravi rightly deserve most of the credit. However, we got a writeup in Technology Review, so I thought I would blog a bit about the paper.

In molecular communication, a transmitter sends a message to a receiver by releasing a pattern of molecules into a shared medium. One way to communicate using molecules is to use timing -- i.e., releasing a molecule at different times to express different messages. Using Brownian motion, the timing message is distorted by the random propagation time from transmitter to receiver.

My original work on molecular communication (1, 2) considered the case of drift-free Brownian motion. In this paper, we extend these results into Brownian motion with drift -- it's a much easier case to deal with, since the first arrival distribution without drift has a very heavy tail, as well as infinite mean. We also have some nice results about modulation: even when multiple molecules are available, pulse position modulation turns out to work quite well if the drift velocity is low.

The paper was submitted to IEEE Trans. Nanobioscience, and we're expecting the first reviews back any day now.