# Telecommunications acronyms

When I first got to campus, I arrived a bit earlier than most of the staff and I didn’t have the key to my office. So I went to the Rutgers Math Library to hunker down and read a bit. It was winter break and so the place was empty. The furniture in there is pretty retro — it kind of reminded me of the Urbana Free Library as a kid. While browsing the stacks, I came across this:

A book I saw at the Rutgers Math Library

One of the most… annoying things about wireless communications is the proliferation of acronyms. The one most people haven’t heard of is UE for “User Equipment.” That is, the cellphone or mobile or tablet. The one that everyone has heard of is LTE, for “Long Term Evolution,” an acronym with nearly zero informational content ($H(\mathsf{LTE}) \approx 0$ for those in the information theory crowd). How “LTE” passed muster with the marketing folks is mysterious to me. Perhaps being more or less meaningless was a plus in their book.

In any case, go to any tutorial on actual wireless technologies (like the LTE tutorial I went to), and it quickly devolves into a soup of acronyms from which few travelers return unscathed. They may be great if you already know what they mean, but it’s a disaster for trying to teach people.

David McAllester, my department chair at TTI, has a started a new blog.

I thought it was pretty well known that people are fairly unique by ZIP code, but Forbes has an article about it now (h/t Raj). Of course, stores can also ping a smartphone’s WiFi to get more accurate location information about your activity within the store — when you check out they can tag your the MAC address of your device to all the other information about you. Creeptastic!

Bradley Efron’s perspective on the impact of Bayes’ Theorem from Science (h/t Kevin).

Some discussion on what makes a popular philosophy book. I wonder what, if anything, transfers over to a popular mathematical book?

Some thoughts from Larry Laudan on the mathematization of the presumption of innocence.

# The politics of your Butterworth filter order

Since I’ve diversified my research interests beyond communications, I kind of lost track of what has been happening in cognitive radio. Via Kevin Drum I learned of another proposed FCC auction of broadcast spectrum in the 600-700 MHz range. Apparently there’s a political debate over how wide the guard bands should be. On the one side, wide guard bands prevent more spectrum from being auctioned off, and on the other, they may allow for some municipalities to put in services operating in those bands (?)

I never thought I would see the day when the sharpness of your bandpass filter would become a political issue, but there you have it.

# Postdoc positions at UT Austin

The ECE department at The University of Texas at Austin seeks highly qualified candidates for postdoctoral fellowship positions, lasting up to two years, in the information sciences, broadly defined. Applicants should have, or be close to completing, a PhD in ECE, CS, Math, Statistics or related fields.

# Illinois Wireless Summer School

I just came back from the Illinois Wireless Summer School, hosted by the Illinois Center for Wireless Systems. Admittedly, I had a bit of an ulterior motive in going, since it meant a trip home to see my parents (long overdue!), but I found the workshop a pretty valuable crash course running the whole breadth of wireless technology. The week started out with lectures on propagation, wireless channel modeling, and antennas, and ran up to a description of WiMAX and LTE. Slides for some of the lectures are available online.

Some tidbits and notes:

• Venugopal Veeravalli gave a nice overview of channel modeling, which was a nice refresher since taking David Tse’s wireless course at the beginning of grad school. Xinzhou Wu talked about modulation issues and mentioned that for users near the edge of a cell, universal reuse may be bad and mentioned Flarion’s flexband idea, which I hadn’t heard about before.
• Jennifer Bernhard talked about antenna design, which I had only the sketchiest introduction to 10 years ago. She pointed out that actually getting independent measurements from two antennas by spacing them just the right distance apart is nearly impossible, so coupling effects should be worked into MIMO models (at least, this is what I got out of it). Also, the placement of the antenna on your laptop matters a lot — my Mac is lousy at finding the WiFi because its antenna is sub-optimally positioned.
• Nitin Vaidya discussed Dynamic Source Routing, which I had heard about but never really learned before.
• Dina Katabi and Sachin Katti talked about network coding and its implementation. The issues with asynchronous communication for channel estimation in the analog network coding was something I had missed in earlier encounters with their work.
• P. R. Kumar talked about his work with I-Hong Hou and Vivek Borkar on QoS guarantees in in a simple downlink model. I had seen this talk at Infocom, but the longer version had more details and was longer, so I think I understood it more this time.
• Wade Trappe and Yih-Chun Hu talked about a ton of security problems (so many that I got a bit lost, but luckily I have the slides). In particular, they talked about how many adversarial assumptions that are made are very unrealistic for wireless, since adversaries can eavesdrop and jam, spoof users, and so on. They mentioned the Dolev-Yao threat model, from FOCS 1981, that I should probably read more about. There were some slides on intrusion detection, which I think is an interesting problem that could also be looked at from the EE/physical layer side.
• R. Srikant and Attila Eryilmaz gave a nice (but dense) introduction to resource allocation and network utilization problems from the optimization standpoint. Srikant showed how some of the results Kumar talked about can also be interpreted from this approach. There was also a little bit of MCMC that showed up, which got me thinking about some other research problems…
• The industry speakers didn’t post their slides, but they had a different (and a bit less tutorial) perspective to give. Victor Bahl from MSR gave a talk on white space networking (also known as cognitive radio, but he seems to eschew that term). Dilip Krishnaswamy (Qualcomm) talked about WWAN architectures, which (from the architectural standpoint) are different from voice or other kinds of networks, and in particular where the internet cloud sits with respect to the other system elements was interesting to me. Amitava Ghosh (Motorola) broke down LTE and WiMAX for us in gory detail.