1. Frequency division multiple access (FDMA) technology
It refers to the time during communications using different frequency channels for data transmission because the channel use different frequencies, so it will not interfere with each other. Early communication is achieved by this technique, relatively easy to implement, but low channel multiplexing.
2. Time Division Multiple Access (TDMA) technology
This technique may be implemented channel multiplexing, it is necessary to channel the carrier fragmentation processing at different times, into a gap 8 to 8 users, because the time is not occupied by the same, so it will not interfere with each other. This technique is frequency division multiple access technology than in the case where the same channel can accommodate more users.
3. Code Division Multiple Access (CDMA) technology
This technique can also be realized channel multiplexing, Qualcomm RESEARCH art. Identify from the 128-bit binary digital orthogonal code sequence, are not the same for all code sequences, the code sequences used to distinguish the base station. CDMA technology can accommodate more users than TDMA.
For chestnuts
There are 4 code division multiple access communication base station, the chip sequences are:
A：（-1-1-1+1+1-1+1+1）
B：（-1-1+1-1+1+1+1-1）
C：（-1+1-1+1+1+1-1-1）
D：（-1+1-1-1-1-1+1-1）
Now receives a chip sequence S: (- 1 + 1-3 + 1-1-3 + 1 + 1). Asked the data base station, his data is 0 or 1?
Now need chip sequence S, respectively A, B, C, D sequence is the inner product and / chip length. Result transmitting -1 0; 0 untransmitted data; transmission 1 1
(A * S) / 8 = (+ 1-1 + 3 + 1-1 + 3 + 1 + 1) / 8 = 8/8 = 1; A therefore transmits data 1
(B * S) / 8 = (+ 1-1-3-1-1-3 + 1-1) / 8 = -8/8 = -1; therefore transmits data B 0
(C * S) / 8 = (+ 1 + 1 + 3 + 1-1-3-1-1) / 8 = 0/8 = 0; therefore the untransmitted data C
(D * S) / 8 = (+ 1 + 1 + 3-1 + 1 + 3 + 1-1) / 8 = 8/8 = 1; D transmits data 1 so
