Changes between Version 20 and Version 21 of WARPLab/Examples/OFDM

Timestamp:

Nov 2, 2015, 4:15:55 PM (8 years ago)

Author:

chunter

Comment:

--

WARPLab/Examples/OFDM

@@ -115 +115 @@
 ||  [[Image(Cn_PEn_Sy_phaseError.png,width=400)]][[BR]]1. Phase Error Estimates and SFO Recovery Matrix  ||  [[Image(Cn_PEn_Sy_constellations.png,width=400)]] [[BR]]2. Rx Constellation  ||  [[Image(Cn_PEn_Sy_evm.png,width=400)]] [[BR]]3. Error Vector Magnitude (EVM)[[BR]] and effective SNR  ||
 
+When both CFO recovery and Phase Error Recovery are disabled, there is nothing to counteract the differing center frequencies of the transmitter and receiver. The result is a received constellation that "spins" around the complex plane. The speed of this spin is CFO. The "beat patterns" of high and low EVM are caused by receive constellation to periodically align to the transmitted constellation as it rotates around the complex plane.
+
 === CFO Recovery: Enabled, Phase Error Recovery: Enabled, SFO Recovery: Disabled ===
 
 ||  [[Image(Cy_PEy_Sn_phaseError.png,width=400)]][[BR]]1. Phase Error Estimates and SFO Recovery Matrix  ||  [[Image(Cy_PEy_Sn_constellations.png,width=400)]] [[BR]]2. Rx Constellation  ||  [[Image(Cy_PEy_Sn_evm.png,width=400)]] [[BR]]3. Error Vector Magnitude (EVM)[[BR]] and effective SNR  ||
 
+Finally, we have re-enabled both time-domain CFO recovery and phase error recovery. We have disabled SFO recovery. As the sample clocks drift over the duration of the reception, EVM begins to increase on the outer subcarriers.
+
 == Limitations ==
 This example is intended as a starting point for researchers wishing to use WARPLab to prototype a wireless communications link. This examples does not implement some some blocks common in deployed OFDM systems, such as scrambling, interleaving and error correcting coding. For an example of a real-time OFDM implementation that implements all of these subsystems, please see the PHY in the [wiki:802.11 802.11 Reference Design].