Preamble only (802.16 OFDMA)
: Cleared (See OFDMA Standard Presets Table.)
(applies to only)
The equalizer is trained using the Channel Estimation Sequence in the preamble of the OFDMA burst. After initialization, the equalizer coefficients are held constant while demodulating the rest of the burst.
When demodulating the 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 802.16 OFDMA signal, the VSA uses an equalizer to correct for linear impairments in the signal path, such as, multi-path. Switching between the different equalizer training methods can help isolate problems contributing to increased EVM Error vector magnitude (EVM): A quality metric in digital communication systems. See the EVM metric in the Error Summary Table topic in each demodulator for more information on how EVM is calculated for that modulation format./RCE Relative Constellation Error is the RMS level of the Error Vector Magnitude, averaged over all subcarriers and all detected OFDM symbols..
is only valid for the Subframe Type since a preamble is only available at the beginning of the Downlink subframe.
The advantages of using the equalization include the following:
- This method models what a typical OFDMA receiver would do when receiving transmissions from a base station. Thus the EVM/RCE measured using this method will more accurately reflect the signal quality seen by a typical OFDMA receiver.
- This method complies with the description in the "RMS constellation error measurement for BS Base Station - The equipment on the network side of a wireless communications link. The base station contains the tower, antennas and radio equipment needed to allow wireless communications devices to connect with the network. (downlink)" section "8.4.12.3.1" of the IEEE 802.16e-2005, standard.
The disadvantages of using the method of equalization include the following:
- The measured EVM/RCE value may be higher for signals whose impairments change during the burst than it would be if the equalizer were trained over the entire burst.
See Also
