| 91 | | * [https://en.wikipedia.org/wiki/Carrier_frequency_offset Carrier Frequency Offset (CFO)] - The center frequency of the transmitter will not perfectly match the center frequency of the receiver. Unless corrected, this will de-orthogonalize the OFDM subcarriers and cause inter-carrier interference (ICI). CFO is typically corrected in the time domain via multiplication with a digital carrier whose frequency negates the CFO estimate. This example uses [#cite1 [1]] |
| 92 | | * Phase Error - Even after CFO is corrected in the time domain, there is typically a residual phase error component that must be corrected in the frequency domain and tracked over time. OFDM systems employ multiple pilot subcarriers to enable this recovery system. |
| 93 | | * Sampling Frequency Offset (SFO) - The temporal duration of a sample is slightly different at the receiver and transmitter due to different sampling clocks. Over the course of a reception, the relative sample periods will drift apart from one another. This manifests as larger phase error for the outer subcarriers |
| | 91 | * [https://en.wikipedia.org/wiki/Carrier_frequency_offset Carrier Frequency Offset (CFO)] - The center frequency of the transmitter will not perfectly match the center frequency of the receiver. Unless corrected, this will de-orthogonalize the OFDM subcarriers and cause inter-carrier interference (ICI). CFO is typically corrected in the time domain via multiplication with a digital carrier whose frequency negates the CFO estimate. This example uses a technique that compares two sequential preamble training symbols to estimate the CFO [#cite1 [1]]. |
| | 92 | * Phase Error - Even after CFO is corrected in the time domain, there is typically a residual phase error component that must be corrected in the frequency domain and tracked over time. OFDM systems employ multiple pilot subcarriers to enable this recovery system. All data subcarriers in each OFDM symbol are phase-rotated to match any residual rotation observed in the known pilots. |
| | 93 | * Sampling Frequency Offset (SFO) - The temporal duration of a sample is slightly different at the receiver and transmitter due to different sampling clocks. Over the course of a reception, the relative sample periods will drift apart from one another. This manifests as larger phase error for the outer subcarriers [#cite2 [2]]. Each data subcarrier in each OFDM symbol is phase-rotated differently according to its subcarrier index. |
