: 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.
A frame control header (FCH) is only associated with demodulating downlink data bursts, not with uplink data bursts.
A downlink PHYPhysical Layer protocol data unit (PDU(protocol data unit) The data unit exchanged between peer entities of the same protocol layer. On the downward direction, it is the data unit generated for the next lower layer. On the upward direction, it is the data unit received from the previous lower layer.) 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 BPSKBinary phase shift keying - A type of phase modulation using 2 distinct carrier phases to signal ones and zeros. 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 QPSKQuadrature phase shift keying 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-MAPdownlink map: A MAC(Medium Access Control: In most wired and wireless networks, a mthod is used to control how and when a device can transmit data over the communications link. This is the network's Medium Access Control scheme. The MAC protocol operates within the Data Link layer (Layer 2) of the ISO OSIOpen System Interconnect 7 layer Model. The IEEE 802.11 standard, for example, specifies the MAC protocol for sharing of the wireless medium, packet formats, addressing, eror detection and recovery following errors. message that defines burst start time for both time division multiplex and time division multiple access (TDMATime Division Multiple Access: A technology for digital transmission of radio signals between, for example, a mobile telephone and a radio base station. In TDMA, the frequency band is split into a number of channels which in turn are stacked into short time units so that several calls can share a single channel without interfering with one another. Networks using TDMA assign 6 timeslots for each frequency channel. TDMA is also the name of a digital technology based on the IS-136 standard. TDMA is the current designation for what was formerly known as D-AMPS.) by a subscriber station (SS) on the downlink.) message and/or uplink map (ULUp Link (reverse link: from cell phone to base station)-MAP) message, then uplink channel descriptor (UCDuplink channel descriptor: A medium access control message that describes the PHY characteristics of an uplink.) and downlink channel descriptor (DCDdownlink channel descriptor: A MAC message that describes the PHY characterstics of a downlink channel.) messages.
Data Subcarrier Modulation (802.16 OFDM)
Subframe Info (802.16 OFDM)
Format tab (IEEE 802.16 OFDM Demod Properties)
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