I found it relatively easy to understand TDMA and FDMA but I just can't figure out CDMA and W-CDMA. For CDMA I think it is something like TDMA without time slots. At transmission side you can use whole bandwidth to send any signal from 0 to time "t". The one thing that secures you that signals wont interfere with each other is by "applying" to each signal different code (modulating that signal into that code). Receiver side only needs to know which code you used for which signal in order to "demodulate" it. I don't think I got it right, so any intuitive explanation would be helpful!
The code is a frequency hopping, direct sequence or Spread Spectrum algorithm to make the signal look like random frequency Gaussian noise but at a faster symbol rate than the data which boosts the conversion from CNR to SNR and allows high traffic to share a wide bandwidth.
It can be synchronous or asynchronous to all the other traffic.