Testbed-based Evaluation of Mobile Communication Systems

The ever increasing demand for mobility calls for new mobile communication systems that deal more efficiently with the very limited bandwidth available. While such systems do exist and work well in computer simulations, little is known about their performance under real world conditions. Little is also known about how to best determine and compare the throughput performance of such wireless communication schemes in specific, realistic outdoor scenarios. The range of effective answers spans from performing numerical simulations to building prototypes. In recent years we have determined that a cost, time, and manpower efficient —as well as effective— method is that of carrying out quasi-realtime testbed measurements. In this approach, all possible transmit data is generated off-line in Matlab, but only the required data is then transmitted over a wireless channel which is altered by moving the receive antennas. The for closed-loop transmissions required feedback is instantly carried out in approximately 40 milliseconds in Matlab. The received data itself is not evaluated in real-time but off-line using a cluster of PCs. Results for the scenario measured are automatically obtained using the same script that has already controlled the complete measurement procedure and documentation. The potential of this efficient approach is demonstrated exemplarily on MIMO single carrier, MIMO HSDPA, and MIMO WiMAX measurements in indoor, urban outdoor, and Alpine outdoor scenarios. We present the results obtained in terms of physical layer throughput over transmit power as well as over transmit antenna element spacing.