Comments for The WindoWSIL http://windowsil.org Your window into the Wireless Systems Innovation Laboratory Thu, 11 Mar 2010 01:19:29 +0000 http://wordpress.org/?v=2.0.3 Comment on Finding a Good Research Topic by Aditya Kurve http://windowsil.org/2008/09/22/finding-a-good-research-topic/#comment-67074 Mon, 08 Mar 2010 03:13:02 +0000 http://windowsil.org/2008/09/22/finding-a-good-research-topic/#comment-67074 Thank you Dr Heath. It was very useful. Thank you Dr Heath. It was very useful.

]]> Comment on Finding a Good Research Topic by zhou baolong http://windowsil.org/2008/09/22/finding-a-good-research-topic/#comment-63612 Wed, 23 Dec 2009 13:40:56 +0000 http://windowsil.org/2008/09/22/finding-a-good-research-topic/#comment-63612 a very good proposal for searching research topic. it is really useful for graduate students . thank u for your sharing ! a very good proposal for searching research topic. it is really useful for graduate students . thank u for your sharing !

]]> Comment on EE Wins the Nobel Prize for Physics by Robert Heath http://windowsil.org/2009/10/07/ee-wins-the-nobel-prize-for-physics/#comment-60463 Wed, 14 Oct 2009 05:00:15 +0000 http://windowsil.org/2009/10/07/ee-wins-the-nobel-prize-for-physics/#comment-60463 This is really great news! It kind of offsets some of the other Nobel decisions this year. I'm glad to see an EE get this award. Compared with the sciences and mathematics, I think we as engineers have very few high visibility awards. Actually I can't think of any awards for engineers that someone, say outside of IEEE, would even know. This is also well deserved because the recipient, as you point out, founded the EE department in CUHK, which is by now quite well known. This is really great news! It kind of offsets some of the other Nobel decisions this year.

I’m glad to see an EE get this award. Compared with the sciences and mathematics, I think we as engineers have very few high visibility awards. Actually I can’t think of any awards for engineers that someone, say outside of IEEE, would even know.

This is also well deserved because the recipient, as you point out, founded the EE department in CUHK, which is by now quite well known.

]]> Comment on Finite-SNR Diversity-Multiplexing Tradeoff by Brian Pocock http://windowsil.org/2007/11/18/finite-snr-diversity-multiplexing-tradeoff/#comment-47001 Thu, 15 Jan 2009 22:34:03 +0000 http://windowsil.org/2007/11/18/finite-snr-diversity-multiplexing-tradeoff/#comment-47001 Many thanks for this intersting article, its been useful for a research paper i'm writing at University about MIMO Many thanks for this intersting article, its been useful for a research paper i’m writing at University about MIMO

]]> Comment on High SNR distribution of eigen-values of a Wishart Matrix by Haochuan Zhang http://windowsil.org/2008/11/12/high-snr-distribution-of-eigen-values-of-a-wishart-matrix/#comment-45121 Wed, 03 Dec 2008 14:52:45 +0000 http://windowsil.org/2008/11/12/high-snr-distribution-of-eigen-values-of-a-wishart-matrix/#comment-45121 Yes, the result is very nice. Indeed, after deriving the first order expansion on the marginal distribution of each Wishart eigenvalue,I find that the exponent of $x$ remains the same even in the presence of spatial correlation and line-of-sight effect. In other words, the diversity order of each MIMO sub-channel is independent of the two factors above. This is very interesting and somewhat amazing, at least to me. PS. Thank you, Rahul Vaze, for the nice paper. Also, WindoWSIL is a nice place. ^_^ Yes, the result is very nice. Indeed, after deriving the first order expansion on the marginal distribution of each Wishart eigenvalue,I find that the exponent of $x$ remains the same even in the presence of spatial correlation and line-of-sight effect. In other words, the diversity order of each MIMO sub-channel is independent of the two factors above. This is very interesting and somewhat amazing, at least to me.

PS. Thank you, Rahul Vaze, for the nice paper. Also, WindoWSIL is a nice place. ^_^

]]> Comment on High SNR distribution of eigen-values of a Wishart Matrix by Rahul Vaze http://windowsil.org/2008/11/12/high-snr-distribution-of-eigen-values-of-a-wishart-matrix/#comment-44083 Thu, 13 Nov 2008 19:36:55 +0000 http://windowsil.org/2008/11/12/high-snr-distribution-of-eigen-values-of-a-wishart-matrix/#comment-44083 It should be included in the chapter that deals with precoders, beamforming etc. It should be included in the chapter that deals with precoders, beamforming etc.

]]> Comment on High SNR distribution of eigen-values of a Wishart Matrix by Robert Heath http://windowsil.org/2008/11/12/high-snr-distribution-of-eigen-values-of-a-wishart-matrix/#comment-44082 Thu, 13 Nov 2008 19:34:24 +0000 http://windowsil.org/2008/11/12/high-snr-distribution-of-eigen-values-of-a-wishart-matrix/#comment-44082 Indeed a very nice result. We should include this somewhere in the MIMO book. I wonder where? Of course, it seems more useful for analyzing MIMO methods that depend on the smaller(est) values instead since it is only good for small x. Indeed a very nice result. We should include this somewhere in the MIMO book. I wonder where? Of course, it seems more useful for analyzing MIMO methods that depend on the smaller(est) values instead since it is only good for small x.

]]> Comment on Finding a Good Research Topic by Finding a Good Research Topic « Ringing In http://windowsil.org/2008/09/22/finding-a-good-research-topic/#comment-41709 Sat, 27 Sep 2008 18:33:27 +0000 http://windowsil.org/2008/09/22/finding-a-good-research-topic/#comment-41709 [...] a Good Research Topic September 27, 2008 Posted by flashbuzzer in Research. trackback I recently wrote this post on my research group’s blog. While it probably best applies tograduate students in wireless communications, some of the ideas expressed there should be useful for grad students in other disciplines. [...] […] a Good Research Topic September 27, 2008 Posted by flashbuzzer in Research. trackback I recently wrote this post on my research group’s blog. While it probably best applies tograduate students in wireless communications, some of the ideas expressed there should be useful for grad students in other disciplines. […]

]]> Comment on LTE abbreviations - Take Your Pick!! by James S. Kim http://windowsil.org/2008/07/18/lte-abbreviation-take-your-pick/#comment-39021 Fri, 15 Aug 2008 21:54:26 +0000 http://windowsil.org/2008/07/18/lte-abbreviation-take-your-pick/#comment-39021 My idea is 'the Largely technologically Evolved standard (LTEs)', which requires one more s, however. My idea is ‘the Largely technologically Evolved standard (LTEs)’, which requires one more s, however.

]]> Comment on LTE abbreviations - Take Your Pick!! by Robert Heath http://windowsil.org/2008/07/18/lte-abbreviation-take-your-pick/#comment-37771 Tue, 22 Jul 2008 20:57:24 +0000 http://windowsil.org/2008/07/18/lte-abbreviation-take-your-pick/#comment-37771 Long Term Engagement? Long Term Engagement?

]]> Comment on The Gold Prize by Rahul Vaze http://windowsil.org/2008/02/04/the-gold-prize/#comment-36332 Wed, 11 Jun 2008 03:50:41 +0000 http://windowsil.org/2008/02/04/the-gold-prize/#comment-36332 You got all the congrats but where is the treat :) You got all the congrats but where is the treat :)

]]> Comment on Slide template using LaTeX by falcon http://windowsil.org/2007/04/24/slide-template-using-latex/#comment-35629 Wed, 14 May 2008 08:30:55 +0000 http://windowsil.org/2007/04/24/slide-template-using-latex/#comment-35629 Perhaps you can put all of the steps into a "Makefile" and then "compile in one step" with the "make" tool in unix-derived systems. Perhaps you can put all of the steps into a “Makefile” and then “compile in one step” with the “make” tool in unix-derived systems.

]]> Comment on AMD Design Contest by Rahul Vaze http://windowsil.org/2008/03/24/amd-design-contest/#comment-34274 Wed, 02 Apr 2008 19:14:51 +0000 http://windowsil.org/2008/03/24/amd-design-contest/#comment-34274 Ali, you can choose any one. Ali, you can choose any one.

]]> Comment on AMD Design Contest by Ali Y. Panah http://windowsil.org/2008/03/24/amd-design-contest/#comment-34159 Mon, 31 Mar 2008 23:47:18 +0000 http://windowsil.org/2008/03/24/amd-design-contest/#comment-34159 which prime factor is p? which prime factor is p?

]]> Comment on 60 GHz Wireless Communications by Robert Heath http://windowsil.org/2008/03/13/60-ghz-wireless-communications/#comment-33405 Wed, 19 Mar 2008 00:26:57 +0000 http://windowsil.org/2008/03/13/60-ghz-wireless-communications/#comment-33405 Very nice introduction. I think there are still a tremendous number of challenges remaining in the 60GHz area. Very nice introduction. I think there are still a tremendous number of challenges remaining in the 60GHz area.

]]> Comment on Overview of MIMO Broadcast Channel Capacity Results by Rahul Vaze http://windowsil.org/2008/02/12/overwiew-of-mimo-broadcast-channel-capacity-result/#comment-33341 Tue, 18 Mar 2008 04:13:17 +0000 http://windowsil.org/2008/02/12/overwiew-of-mimo-broadcast-channel-capacity-result/#comment-33341 Thanks Caleb for pointing out the typos. Thanks Caleb for pointing out the typos.

]]> Comment on 60 GHz Wireless Communications by Ali Y. Panah http://windowsil.org/2008/03/13/60-ghz-wireless-communications/#comment-33260 Mon, 17 Mar 2008 02:05:54 +0000 http://windowsil.org/2008/03/13/60-ghz-wireless-communications/#comment-33260 aah I see. thanks aah I see.
thanks

]]> Comment on 60 GHz Wireless Communications by Bob Daniels http://windowsil.org/2008/03/13/60-ghz-wireless-communications/#comment-33255 Sun, 16 Mar 2008 23:57:33 +0000 http://windowsil.org/2008/03/13/60-ghz-wireless-communications/#comment-33255 That's a fair question. The consumer wireless market is driven by the spectrum that it has available. It just turns out that 60 GHz, although not by luck, has large quantities of free unlicensed spectrum available for virtually every "power player" in the wireless market (Japan, Korea, Europe, Australia, and North America). You have to realize that spectrum is mostly licensed for specific applications including radar, television broadcasts, and satellite communications. Other unlicensed millimeter-wave frequencies are available (for example 92-95 GHz in the United States). However, the international availability as well as the bandwidth magnitude available for 60 GHz carrier frequencies is quite unique when we consider all the "power players" together. So to answer your question, if the same amount of bandwidth was available at 30 GHz internationally (compared to 60 GHz), it would almost certainly be receiving more attention since it would observe less path loss and atmospheric absorption. That’s a fair question. The consumer wireless market is driven by the spectrum that it has available. It just turns out that 60 GHz, although not by luck, has large quantities of free unlicensed spectrum available for virtually every “power player” in the wireless market (Japan, Korea, Europe, Australia, and North America).

You have to realize that spectrum is mostly licensed for specific applications including radar, television broadcasts, and satellite communications. Other unlicensed millimeter-wave frequencies are available (for example 92-95 GHz in the United States). However, the international availability as well as the bandwidth magnitude available for 60 GHz carrier frequencies is quite unique when we consider all the “power players” together.

So to answer your question, if the same amount of bandwidth was available at 30 GHz internationally (compared to 60 GHz), it would almost certainly be receiving more attention since it would observe less path loss and atmospheric absorption.

]]> Comment on 60 GHz Wireless Communications by Ali Y. Panah http://windowsil.org/2008/03/13/60-ghz-wireless-communications/#comment-33216 Sun, 16 Mar 2008 01:08:38 +0000 http://windowsil.org/2008/03/13/60-ghz-wireless-communications/#comment-33216 This was excellent Bob. I have a not so smart question. why 60? why not something like 30GHz? This was excellent Bob.
I have a not so smart question. why 60? why not something like 30GHz?

]]> Comment on Overview of MIMO Broadcast Channel Capacity Results by Caleb Lo http://windowsil.org/2008/02/12/overwiew-of-mimo-broadcast-channel-capacity-result/#comment-33113 Fri, 14 Mar 2008 17:50:49 +0000 http://windowsil.org/2008/02/12/overwiew-of-mimo-broadcast-channel-capacity-result/#comment-33113 Rahul - thanks for this writeup. Sometimes I find it difficult to get a handle on information-theoretic results, but this writeup illustrates the key proof mechanisms at a relatively accessible level (MIMO-BC -> AMIMO-BC -> DAMIMO-BC -> enhanced DAMIMO-BC, which is where I guess Bergman's proof becomes quite useful). It would be interesting to compare the proof employed here with that in the paper by Mohseni and Cioffi. A few comments on the nuts and bolts of this writeup: 1) Throughout the writeup we see that the governing system equation has user $n$ receiving $y_n = H_nx_n+v_n$. It seems, though, that the transmitter would send $x$ to user $n$, not just $x_n$ (which is what user $n$ wants to decode). 2) There seems to be a mistake in the achieved rate for user 2 in the case where DPC encoding entails encoding user 2's signal first. The determinant in the denominator should have $S_1$, not $S_2$ (since user 1's signal would interfere with user 2's signal). 3) The definition of the enhanced DAMIMO-BC is somewhat confusing. It would seem more straightforward to have the constraint $cov(\hat{v}_i)\leq cov(v_i^{*})$ for $i = 1,2$. Currently, $cov(\hat{v}_1)$ is compared with $cov(v_2^{*})$, but how is this an improvement over the DAMIMO-BC? I wonder if the accompanying sum constraint on the covariances is the key to understanding this. Rahul - thanks for this writeup. Sometimes I find it difficult to get a handle on information-theoretic results, but this writeup illustrates the key proof mechanisms at a relatively accessible level (MIMO-BC -> AMIMO-BC -> DAMIMO-BC -> enhanced DAMIMO-BC, which is where I guess Bergman’s proof becomes quite useful).

It would be interesting to compare the proof employed here with that in the paper by Mohseni and Cioffi.

A few comments on the nuts and bolts of this writeup:
1) Throughout the writeup we see that the governing system equation has user $n$ receiving $y_n = H_nx_n+v_n$. It seems, though, that the transmitter would send $x$ to user $n$, not just $x_n$ (which is what user $n$ wants to decode).
2) There seems to be a mistake in the achieved rate for user 2 in the case where DPC encoding entails encoding user 2’s signal first. The determinant in the denominator should have $S_1$, not $S_2$ (since user 1’s signal would interfere with user 2’s signal).
3) The definition of the enhanced DAMIMO-BC is somewhat confusing. It would seem more straightforward to have the constraint $cov(\hat{v}_i)\leq cov(v_i^{*})$ for $i = 1,2$. Currently, $cov(\hat{v}_1)$ is compared with $cov(v_2^{*})$, but how is this an improvement over the DAMIMO-BC? I wonder if the accompanying sum constraint on the covariances is the key to understanding this.

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