We are encountering a problem with a bottleneck regarding the data rates in MIMO AFW.
We are employing a configuration consisting of one single-antenna MS (1 x NI-USRP 2954R) and one four-antenna BS (2 x NI-USRP 2954R). The transmission is carried only on uplink, from MS to BS. The set-up acts as a bridge for UDP data, as the incoming traffic is input to the source port 50001 of the MS, and is taken to the output at the sink port 60001 of the BS.
The traffic under discussion is generated from another PC, where the packet length can be set and the interval between packets can be configured also. If we set a packet length of 400 bytes and we set the time interval between packets to 118 us, normally we should obtain a data rate of roughly 400 Bytes x 8 / 118 us = 27Mbps, which is actually obtained in the MIMO AFW. Also, for packets of 500 Bytes with a time interval between packets of 148 us, we should further get 500 Bytes x 8 / 148 us = 27Mbps, which is still obtained in the MIMO AFW. However, when the length of the packet is set to 300 Bytes and the time interval between packets is set to 88 us, we no longer obtain 300 Bytes x 8 / 88 us = 27Mbps, but a data rate of 21-22Mbps, which is equivalent with a time interval between packets of 114us, as no data loss is recorded.
In this context, we noticed that regardless of the packet size, for time intervals between packets set somewhere below 114us, the MIMO AFW will no longer respond. The framework will decrease the transfer rate keeping the time interval fixed at approximately 100-114 us, rather than change the transfer rate according to the initially set time interval between packets.
Our question is: are there any limitations in MIMO AFW regarding the minimum accepted time interval between UDP packets that can affect the maximum achievable transfer rate for a UDP packet of a certain length?
