When I do an Omnipeek capture of an iPerf TCP throughput test over WiFi, I only see TCP Acks from the iPerf server to the client. How come I don't see any TCP frames from the client to the server? I thought iPerf traffic moves from client to server.
It seems that your omnipeek client card cannot capture higher data rate traffic. The ACK frames are sent with basic data rates and the DATA frames are sent with higher data rates. The issue can come up if your client and AP are transmitting on 3 stream and 40 MHz and omnipeek can listen on 1 stream and 20 MHz. This can also happen if the omnipeek client card is at a distance as it may not see the date frames.
Please make sure the the Omnipeek client card supports 3 (or at-least 2 streams) and it also supports 40MHz channel bandwidth