Synchronization Reference (802.11a/g/j/p OFDM)

Synchronization Reference controls the type of synchronization used to synchronize to the start of an OFDM Orthogonal Frequency Division Multiplexing: OFDM employs multiple overlapping radio frequency carriers, each operating at a carefully chosen frequency that is Orthogonal to the others, to produce a transmission scheme that supports higher bit rates due to parallel channel operation. OFDM is an alternative tranmission scheme to DSSS and FHSS. burst. The two available choices are Short Training Sequence (also called Short Sync or Short Training Symbols) and Channel Estimation Sequence (also called Long Sync or Long Training Symbols).

Short Training Sequence: Synchronizes the start of the OFDM burst to the OFDM Short Training Sequence.
Channel Estimation Sequence: Synchronizes the start of the OFDM burst to the OFDM Channel Estimation Sequence.

For IEEE Institute of Electrical and Electronics Engineers. A US-based membership organisation that includes engineers, scientists, and students in electronics and related fields. The IEEE developed the 802 series wired and wireless LAN standards. Visit the IEEE at http://www.ieee.org 802.11a/g, either sync type is valid, the default is set to Short Training Sequence. For HIPERLAN/2, the only valid sync type is Channel Estimation Sequence.

Synchronization Reference also specifies the segment of the preamble used by the VSA to compute the Sync Corr error data result.

IEEE 802.11a/g/j/p Training structure

The IEEE 802.11a/g/j/p preamble field (PLCP Physical layer convergence protocol preamble SYNC) is used for synchronization. It consists of 10 short symbols (t1 through t10) and 2 long symbols (T1, T2) as shown in the following figure.

HIPERLAN/2 Training Structure

HIPERLAN/2 typical preamble training structure. The Channel Estimation Sequence is used for synchronization.