8.2.4 Duplexing techniques and PHY Type parameter encodings

Both frequency division and time division duplexing are supported. The duplexing method shall be reflected in the PHY Type parameter (11.1.2.1) as shown in Table 85.

Table 85—PHY Type parameter encoding

8.2.4.1 FDD operation

In FDD operation, the uplink and downlink channels are on separate frequencies. The capability of the downlink to be transmitted in bursts facilitates the use of different modulation types and allows the system to simultaneously support full-duplex subscriber stations (which can transmit and receive simultaneously) and half-duplex subscriber stations (which do not). Note that the downlink carrier may be continuous, as demonstrated in Figure 107 (third frame). Figure 107 describes the basics of the FDD operation.

In the case of a half-duplex SS, transition gaps, as described in 8.2.4.2.1 and 8.2.4.2.2, apply.

Downlink

Uplink

frame

time

Figure 107—Example of FDD bandwidth allocation

8.2.4.2 TDD operation

In the case of TDD, the uplink and downlink transmissions share the same frequency but are separated in time, as shown in Figure 108. A TDD frame also has a fixed duration and contains one downlink and one uplink subframe. The TDD framing is adaptive in that the link capacity allocated to the downlink versus the uplink may vary.