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From: Rajib Chowdhury on 22 Feb 2010 23:13
I am MSc student of wireless communication systems . I am working on thesis related with MIMO-OFDM system based on IEEE 802.16-2004. I am struggling to upgrade availale simulink model for MISO to MIMO . can any one help me to come with exact solution. Yeah i have done all jobs but so so confused about construct frequeney selective channel.
For IEEE 802.16-2004 with out stbc model available in matlab, I use bandwidth of 3.5 Mhz.
But i am not sure why delay vector is [0 prm80216d.chanTs]. chanTs is channel symbol period that according to my calculation could be .1406
channel delay spread need to be greater than symbol period.
In available model in Matlab, symbol period according to my calculation is p.Ts/p.numDataSym = 72/192 =.375 .
it Seems to me symbol period is not greater than chanel delay spread so how they implement frequency selective channel.
What could be the maximum doppler for IEEE 802-16-2004 .
If i calculate using equation f=vf/c for a train moving at speed 315 km/h
for frequency band 6 GHz, f= (315 km/h X 6Ghz)/3X100000000, i get doppler could be 3194.44 Hz. If i put this value as maximum doppler shift it give me very high ber. I have asked myself 1000 times am i right or doppler should be 10 hz.
For IEEE 802-16-2004 with STBC i have similar problem about those variables. I have tried upgrade miso model to mimo model .
In that mimo model i have created channel without fading that is created using
AWGN block in simulink. I have created channel with flat fading using Rayleigh and AWGN channel putting those two in sequence. Assigning doppler 10 Hz. Here i have again same problem whether doppler should be 3194.44 hz.delay vector 0 gain vector is 0 . Since its a 2X2MIMO system I have created four channel using 4 parallel cannel each sub channel having 1 Rayleigh channel and 1 AWGN. For each rayleigh channel i have assigned above mention value. Is it ok?
To create frequnency selective channel , i work in similiar way to flat fading channel .
but I have created gain vector [0 -3] and delay vector [0 (2.1*prm80216ds.chanTs)]
2.1*prm80216ds.chanTs=2.1* .1875 to make sure delay spread greater than OFDM symbol period. where OFDM sysmbol period is .375
Some time i think , whetehre " prm80216ds.chanTs" is single variable or two variables.
If you know the answers, can you please please help me. I need help and will be grateful . I need to submitt my thesis within one week. So if you just say this value means that or this should be done in this way , that will help me lot.
Thanks
Rajib



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