OFDMA Principles in LTE

There are several ways to transmit over the frequency band and to share the resource between several devices.
 
What is TDMA,CDMA & FDMA ?
 
1.TDMA
• The users are separated by the the time
• Used by the GSM
2.CDMA
• The users are separated by the codes. They receive data at the same time at the same frequency.
• Used in the CDMAOne, CDMA2000 and WCDMA 
3.FDMA
• The users are separated by the frequency
• The 3G LTE used an improved FDMA called OFDMA