From b80ac9d9319c02e4ab576c2efcb534c58f7d53d8 Mon Sep 17 00:00:00 2001
From: eneller <erikneller@gmx.de>
Date: Mon, 23 Mar 2026 19:26:22 +0100
Subject: [PATCH] begin cdma decode

---
 cdma.Rmd | 39 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)

diff --git a/cdma.Rmd b/cdma.Rmd
index aba56d6..18affc7 100644
--- a/cdma.Rmd
+++ b/cdma.Rmd
@@ -62,7 +62,7 @@ perms <- combn(x = orthogonals,m = 2, simplify = FALSE)
 
 
 ```{r encode}
-output = c()
+output <- c()
 for (j in 1:ncol(lines_bin)){
   col <- lines_bin[,j]
   output_symbol <- 0
@@ -73,8 +73,43 @@ for (j in 1:ncol(lines_bin)){
     single_symbol <- (-1)^(1+symbol) * code # the resulting encoded vector
     output_symbol <- output_symbol + single_symbol # the sum of all encoded vectors
   }
-  output <-append(output, output_symbol)
+  output <-append(output, list(output_symbol))
 }
 ```
 
+## Decode
+Decoding CDMA is achieved by calculating the dot product of the received encoded symbol with each channel's characteristic code.
+```{r decode}
+decoded <- c()
+for (symbol in output){
+  decoded_col <- c()
+  for(i in 1:nrow(orthogonals)){
+    code <- orthogonals[i,]
+    decoded_symbol <- if(code%*% symbol > 0) 1 else 0
+    decoded_col <- append(decoded_col,decoded_symbol)
+  }
+  decoded<- append(decoded, list(decoded_col))
+}
+decoded_m <- do.call(cbind,decoded)
+```
 
+Then we apply our text encoding on each line separately.
+```{r text-decode}
+chunk <- function(x, chunk_size) {
+  split(x, cut(seq_along(x), breaks = seq(0, length(x), by = chunk_size), include.lowest = TRUE))
+}
+for (i in 1:nrow(decoded_m)){
+  line <- decoded_m[i,]
+  symbols <- chunk(line, 7)
+  for (symbol in symbols){
+    binary_str <- paste(symbol, collapse = "")
+    # Convert the binary string to a decimal value
+    decimal <- strtoi(binary_str, base = 2)
+    print(decimal)
+    # Convert the decimal value to an ASCII character
+    char <- intToUtf8(decimal)
+    print(char)
+  }
+}
+
+```
\ No newline at end of file