Duplex transmission is the simultaneous transmission of two information signals that allows simultaneous (or near simultaneous) 2-way communication. The WiMax system can use frequency division duplex (FDD), time division duplex (TDD) or half frequency division duplex (H-FDD).

Frequency division duplex is the process of simultaneously allowing the transmission of information in both directions via separate bands ( frequency division). When using FDD, each device transmits on one frequency and listens on a different frequency.

Time division duplex is a process of allowing two way communications between two devices by time sharing. When using TDD, one device transmits (device 1), the other device listens (device 2) for a short period of time.

After the transmission is complete, the devices reverse their role so device 1 becomes a receiver and device 2 becomes a transmitter. The process continually repeats itself so data appears to flow in both directions simultaneously.

H-FDD is a process that allows for two way communications between two devices through the combination of frequency division and time sharing. When using H-FDD, one device (device 1) transmits on one frequency which the other device (device 2) listens for a short period of time on that frequency. After the transmission is complete, the devices reverse their roles and device 2 transmits on a different frequency and the other device listens for a short period of time on that frequency. The process continually repeats itself so data appears to flow in both directions simultaneously. The use of H-FDD systems allows...