WIDE-BAND MEASUREMENT AND ANALYSIS TECHNIQUES FOR THE MOBILE RADIO CHANNEL

The appearance of high bit rate digital radio systems would appear to demand the existence of wide-band channel models, planning tools, and simulation capabilities. The inclusion of these wide-band effects in planning tools would, in many cases, appear to be the most obvious way of improving upon the accuracy of existing propagation modeling techniques, especially in areas subject to multipath interference, for example, in urban areas surrounded by mountains. Detailed channel information is particularly important in the development of these more refined propagation models. This means that the mobile radio planner needs access to the local scattering function rather than just the average signal strength; moreover, it is increasingly desirable that experimentalists have the capability to locate scatterers (measure the direction of arrival azimuthal as well as elevation) to aid in multipath model development. In this paper, we present an overview of various approaches to wide-band channel data acquisition (channel sounding) and data analysis for the locally QWSSUS channel. In particular, we outline how high-speed digital signal processing techniques can be employed to construct a nearly ideal real-time wide-band channel sounder. The digital sounder which we describe employs a TMS32050A to implement a matched filter type receiver. The probe signal is a carrier BPSK modulated with a binary maximal length sequence; the received signal is processed in real time, yielding a complex time variant channel impulse response. A dynamic range in excess of 40 dB is achieved. We also briefly discuss techniques to use this data for stored channel simulation. Finally, by way of pointing-out that much more information can be extracted from channel sounding data than is generally appreciated, we briefly discuss the use of probability theory (Bayesian techniques) in model selection.