| 51 | | * Packet Detection: |
| 52 | | * Antenna Selection: |
| 53 | | * LTS Correlation: |
| 54 | | * Synchronization: |
| 55 | | * CFO Correction: |
| 56 | | * FFT: |
| 57 | | * Phase Error Estimation: |
| 58 | | * Channel Estimation: |
| | 51 | * '''Packet Detection''': implements two packet detection schemes: simple energy detection based on RSSI and auto-correlation of the I/Q samples searching for the preamble STS, based on the well-known [ieeexplore.ieee.org/iel3/26/14182/00650240.pdf Schmidl-Cox algorithm]. When selection diversity is enabled parallel packet detectors are enabled so that either antenna can trigger a detection. |
| | 52 | |
| | 53 | * '''Antenna Selection''': automatic selection of which I/Q stream feeds the rest of the PHY pipeline, using AGC gain selections as an indicator of received SNR. |
| | 54 | |
| | 55 | * '''LTS Correlation''': cross correlator searching for the 64-sample LTS in the preamble. The two LTS correlation peaks establish timing for the rest of the reception, marking the boundary of each OFDM symbol fed into the FFT. |
| | 56 | |
| | 57 | * '''Synchronization''': a dual-port circular sample buffer records all incoming samples. Once the LTS correlator establishes sample-level timing the buffer begins reading samples into the FFT using the correlation timing to set the boundary of each OFDM symbol. |
| | 58 | |
| | 59 | * '''CFO Correction''': the carrier frequency offset (CFO) is estimated before the FFT by comparing the phases of identical samples in the two LTS. The CFO is estimated by averaging the 64 phase comparisons, then removed by multiplying the I/Q samples by the output of a DDS. |
| | 60 | |
| | 61 | * '''FFT''': translates the time domain received samples into the frequency domain. Each FFT consumes 64 time domain samples and produces 64 frequency domain samples. The boundary of each FFT is established by the synchronization blocks above. The cyclic prefix of each OFDM symbol is removed by advancing the boundary of each FFT 16 samples per transform. |
| | 62 | |
| | 63 | * '''Channel Estimation''': |
| | 64 | |
| | 65 | * '''Phase Error Estimation''': |
