You are currently browsing the monthly archive for March 2011.

Happened to see a wonderful animation on the formation of human embryo and how a baby develops from almost nothing to the cute avatar!. First, I saw as it through a Facebook feed, but it is also there in you tube. I don’t know who the original creator of this nice animation is . Wonderful!

It was in 2006, I guess, I had written a mail to Mathworks on this topic. I did get an acknowledgment from them saying that they will incorporate this into the future version. I don’t see it yet. I wonder why! Anyway, here is the Email I had sent to them. Unfortunately, I couldn’t trace their Email reply since it was sent to my earlier official ID, which has changed! Hopefully, I will ping Mathworks  again and get this up.

I believe the theoretical BER under fading scenarios, provided by the ‘berfading’ function in Communication toolbox is not quite accurate, for frequency flat fading, when Doppler shift to be considered. Currently, for example, the berfading gives out the BER for Rayleigh (or Rice) fading channel, without considering the impact of Doppler spread. In the presence of  Doppler, there may be an irreducible error floor for certain modulation schemes, especially differential modulation schemes. There are theoretical results (not closed form) to reflect such impacts. Closer approximations of the average bit error probability are derived in closed form for some of the differential schemes (say DBPSK, DQPSK etc).

Just to illustrate the point, I am enclosing here, a snapshot of the comparative BER results. For DBPSK, the exact BER, considering maximum Doppler frequency, for a uniform scattering model (Jakes spectrum) can be better approximated to Pb=(0.5./(1+EbN0) ) .*(1+ (EbN0.*(1-besselj(0,2*pi*Ts*fd)) )); The simulation results closely match this result, as against the berfading  result “berfading(SNR,’dpsk’,M,1)”

The BER curves are shown in the figure, attached with. Blue curve is what Matlab ‘berfading’ gives. The pink (Pb_doppler_theory) is the approximate and more correct bound, for Jakes spectrum (See [1], [2], [3]). The latter result is in close unison with the simulation as well.It would be nice if Mathworks can modify (may be in the next release) berfading such that, the  theoretical BER expected take care of such fading characteristics (in this case Doppler). I am  using 2006b version of matlab. In this only Jakes spectrum can be compared. For other  spectrum (I read in the Mathworks website that other spectrums can be configured in later
versions of Matlab/toolboxes), appropriate modifications to be done.

[1] P. Y. Kam, Tight bounds on the bit-error probabilities of 2DPSK and 4DPSK in nonselective Rician fading,IEEE Trans. Commun., pp. 860-862, July 1998.
[2] P. Y. Kam, Bit error probabilities of MDPSK over the nonselective Rayleigh fading channel with diversity reception,IEEE Trans. Commun., pp. 220-224, Feb. 1991.
[3] M. K. Simon and M.-S. Alouini, Digital Communication over Fading Channels A Unified Approach to Performance Analysis, Wiley 2000.

The cricket world cup 2011 was at best boring, until yesterday. The Chinnaswami stadium in Bangalore, when all lights were alight, Ireland looking down the barrel at 111/5 with 26 overs to go, in search of the English target of 328, in came Kevin O’Brien. What stuck then onwards was sheer magic. Scintillating innings of power and conviction, which in the end sink the English hope. I cant imagine how berserk the Irish pubs in Dublin would have been last evening, post the most thrilling upsets in the world cup cricket history.

Come to think of it that Ireland has beaten a reasonably in form England by 3 wickets with 5 balls to spare. That too chasing a mammoth target of 328 for a win! If only they had beaten a relatively easy Bangladesh in the earlier match, this pool would have been very interesting. Honestly, the Ireland-Bangladesh match was played on a hopeless pitch, but that is no excuse.

Until yesterday, not many people would have given a chance to Ireland, in spite of the upset victory over Pakistan in the 2007 edition. No one had feared Kevin O’brien this much. But from now on, the teams will be aware of this massive threat, especially on flat tracks where one can hit through the line at will. Ireland is due to play India next in the very same ground. Not to forget that, the last match prior to this at the same venue produced a classic tie at 238, between England and India. So, game on?

For some reason, I really love the beginning scenes of the movie Tangled. The screen visualization and the audio are simple amazing. These days, I really relish seeing this again and again, especially the starting scene and the songs. Thanks Disney for such a wonderful movie!

For a generation of kids like me, growing up in the 80s and 90s in India, Anant Pai, popularly known as Uncle Pai was one of the most influential figure. Not because of his personality or the aura in public life, but the sheer creativity in transpiring the richness in the Hindu mythological stories to us in the form of children stories. The Amar Chitra Katha stories from him, not only had improved our knowledge on the many epic stories and its variants, but also brought the curiosity in the fairy tale world to young minds. It is with immense sadness I passed the day hearing his sad demise, last week.

 leeyoongu on LT codes decoding using Wiedem… vinod kumar on Yesudas and Rafi singing same… Ramesh on The split lot corner stor… sreelesh. on Yesudas and Rafi singing same… The new Prime gap |… on Improved bounds on Prime numbe…