added some OCTAVE scripts for OFDM generation in ARCH/EXMIMO/USERSPACE/OCTAVE

git-svn-id: http://svn.eurecom.fr/openair4G/trunk@4092 818b1a75-f10b-46b9-bf7c-635c3b92a50f

targets/ARCH/EXMIMO/USERSPACE/OCTAVE/OFDM_TX_FRAME.m

+function sig = OFDM_TX_FRAME(num_carriers,num_zeros,prefix_length,num_symbols_frame,preamble_length)
+
+% sig - output signal
+% sig_length - output signal length
+% num_carriers - number of sub-carriers
+% num_zeros - number of zero carriers minus 1 (DC)
+% prefix_length - length of cyclic prefix
+% num_symbols_frame - number of symbols per OFDM frame
+% preamble_length - length of 4-QAM preamble
+
+num_useful_carriers = num_carriers - num_zeros -1;
+
+sig = [];
+for k=1:preamble_length
+     QAM4_preamble = QAM_MOD(4,floor(256*abs(rand(1,num_useful_carriers/4))));
+     sig = [sig OFDM_TX(num_carriers,num_zeros,prefix_length,QAM4_preamble)];
+end
+
+for k=1:(num_symbols_frame - preamble_length)
+     QAM_data = QAM_MOD(256,floor(256*abs(rand(1,num_useful_carriers))));
+     sig = [sig OFDM_TX(num_carriers,num_zeros,prefix_length,QAM_data)];
+end