You are not logged in.
I noticed that when I compared the long training symbols from the ofdm_tx_mimo_init.m file and the output from the OutputMuxes block, there appeared to be a slight discrepancy. The first two long training symbols looked correct, but the last two samples from half of the long training symbol don't match what is defined in the previously mentioned matlab file. I'm looking into whether this is a timing issue in the OutputMuxes block and the payload is being prematurely sent over prior to the preamble being completely transmitted. Is this a timing issue?
Offline
I stumbled across this bug recently- the output muxes switch to the payload 2 cycles early. This is the result of adding the preamble scaling multiplier (which has a 2 cycle latency) without adjusting the preamble/payload timing. You can fix it by changing a constant value in the OFDM Tx control block. In 'OFDM Tx MIMO/TxControl', there's a constant in the middle of the model with value 'length(preamble)-158'. This value is compared to the output of a counter which addresses the preamble lookup tables. When this counter hits the value 'length(preamble)-158', the Tx state machine starts processing payload. The 158 corresponds to the number of preamble samples which are transmitted while the Tx pipeline computes the first output sample. Change this constant value to 'length(preamble)-156' to delay the Tx pipeline by 2 cycles, which will cause the output muxes to switch after the last preamble sample.
Offline