One issue with bench testing is that the Rx level can be too high which causes distortion on the receiver.
There are several ways to reduce the receive level
1) Reduce the Tx power on both ends, to the minimum level available on the product.
2) Increase the link loss between the units.
- If you are using connectorised units with cable connectors use attenuators in the cables.
- If you are using integrated antennas increase the link loss between the units. You could us RF absorbing material, or simply lay the units on the floor 5 meters apart, with the antennas facing the ground