From FCH - Data Subcarrier Modulation Format (802.16 OFDM)

Default: See 802.16 OFDM Standard Setups/Presets Table.

The VSA uses information within the frame control header (FCH) to determine the Data Subcarrier Modulation Format. If the FCH symbol is not present, the data subcarrier modulation format is automatically detected instead. The FCH information is used only for the first data burst, for subsequent bursts the data subcarrier modulation format is automatically detected.

For more information, see Data Subcarrier Modulation.

About FCH "Frame Control Header"

A frame control header (FCH) is only associated with demodulating downlink data bursts, not with uplink data bursts.

A downlink PHY protocol data unit (PDU) starts with a long preamble, which is used for PHY synchronization. The preamble is followed by a frame control header (FCH) burst. The FCH has the BPSK modulation format. The FCH is followed by one or more downlink data bursts, each transmitted with different burst profile. Data bursts with more robust modulation types are transmitted before bursts with less robust modulation (e.g. a QPSK burst is transmitted before a 64QAM burst).

The following example of the Subframe Info data trace shows the FCH (BPSK), followed by data bursts of QPSK, 16QAM and 64QAM.

The FCH may be followed by broadcast messages such as a downlink map (DL-MAP) message and/or uplink map (UL-MAP) message, then uplink channel descriptor (UCD) and downlink channel descriptor (DCD) messages.

See Also

Data Subcarrier Modulation (802.16 OFDM)

Subframe Info (802.16 OFDM)

Format tab (IEEE 802.16 OFDM Demod Properties)


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