A method and arrangement for generating data for transmitter or receiver simulations where the generated data includes Multiple Input Multiple Output radio environment (MIMO) characteristics. The arrangement includes a model data (11), which is off-line loadable to transmitter baseband unit (12). The model data is transmitted over a MIMO environment (14, 24), which scrambles the transmitted data. A receiver baseband unit (16) receives and saves the data. From the receiver baseband unit (16) the received data is loadable off-line to an external device where the data can be utilized in transmitter or receiver algorithm simulations.