- Multiple preambles added to have more confidence in the channel estimate being calculated. Further, the frame_acquisition block was changed to calculate the equalizer appropriately. The last preamble is used only to calculate the SNR.
- The first data OFDM symbol is discarded. On the transmitter the change is in ofdm_packet_utils.py, and on the destination the corresponding change is reflected in crc_check() in ofdm_frame_sink. Also need to alter the behavior of the forwarder (which is not done in this changelist).
- Provision is made for every receiver to send the timing-offset slope (in the ‘h’ values) back to the transmitter. The transmitter can then correct the outgoing symbols (including preamble) with the corresponding timing-offset slope - this should reduce the rotation being seen at the receiver.
- ofdm_insert_preamble is dropped. Instead, the corresponding changes are made in the ofdm_mapper_bcv block to allow for the preamble addition. Faster and neater this way.
- Cleanup performed in ofdm_frame_sink to remove the unused code.
- Potentially multiple equalizers are calculated (one for each preamble except the last one - which is only used for snr). However, in the frame_sink, only the equalizer by the latest preamble is actually used.
- gr_message.h - padding bytes changed, since the header also includes the timing offset now.