utils: add script to create long preamble

utils/create_long.R

@@ -0,0 +1,26 @@
+
+fft.shift <- function(sym) {
+
+	sym <- matrix(sym, ncol=64)
+
+	# the explicit dimensions are required
+	# if sym contains only one row
+	m1 <- matrix(sym[,33:64], ncol=32)
+	m2 <- matrix(sym[, 1:32], ncol=32)
+
+	return(cbind(m1, m2))
+}
+
+### symbols as defined in the standard
+sym <- c(1, 1, -1, -1, 1, 1, -1, 1, -1, 1, 1, 1, 1, 1, 1, -1, -1, 1, 1, -1, 1, -1, 1, 1, 1, 1, 0, 1, -1, -1, 1, 1, -1, 1, -1, 1, -1, -1, -1, -1, -1, 1, 1, -1, -1, 1, -1, 1, -1, 1, 1, 1, 1)
+freq <- c(rep(0, 6), sym, rep(0, 5))
+
+pre <- fft(fft.shift(freq), inverse=T) / sqrt(52)
+
+
+for(i in seq(1, 64, 4)) {
+	cat("\t\tgr_complex(", sprintf("% .4f", Re(pre[  i])), ", ", sprintf("% .4f",  Im(pre[  i])), "), ", sep="")
+	cat(    "gr_complex(", sprintf("% .4f", Re(pre[i+1])), ", ", sprintf("% .4f",  Im(pre[i+1])), "), ", sep="")
+	cat(    "gr_complex(", sprintf("% .4f", Re(pre[i+2])), ", ", sprintf("% .4f",  Im(pre[i+2])), "), ", sep="")
+	cat(    "gr_complex(", sprintf("% .4f", Re(pre[i+3])), ", ", sprintf("% .4f",  Im(pre[i+3])), "),\n", sep="")
+}