CDMA(Code Division Multiple Access)
FDMA and TDMA seemed pretty intuitive, but studying CDMA seemed like a slightly more higher level then both.
Some key terms in CDMA is Data Representation and the Chip Sequence.
The The chip sequence is a short binary code, often just a few bits long, and is unique to each user in the network.
In data representation, each data bit is represented by a long sequence of chips, which are produced by multiplying the data bit with the user's unique chip sequence. These chip sequences are designed to have low cross-correlation with each other, which helps to reduce interference between users.
In the above image, each user(C1, C2, C3, C4) has a unique chip sequence which will be multiplied to a data bit.
In this particular procedure, the stations 1~4 has the bit -1, -1, 0, +1. The 0 bit states that the station will be silent.
The bits are then multiplied to the chip sequences repectively, and the result we be:
Additionaly, this is the creation of the Walsh Table
