1476 PIERS Proceedings, Kuala Lumpur, MALAYSIA, March 27–30, 2012 Measurement and Parameter Description of Time-varying Ultra-wideband Infostation Channel U. A. K. Chude-Okonkwo, R. Ngah, Yasser K. Zahedi, S. M. Zaid, and T. A. Rahman Wireless Communication Center, Universiti Teknologi Malaysia, Malaysia Abstract— In this article, we present the measurement and description of channel parameters for the time-varying Infostation UWB channel. We also consider how such parameters can be used to improve system performance in terms of optimally combating inter-symbol interference (ISI) and inter-channel interference (ICI) in the case of multiband OFDM. 1. INTRODUCTION The concept of infostation [1–3] presents a new way to look at the problem of providing high data rate wireless access. It is an isolated pocket area with small coverage (hundreds of meters) of high bandwidth connectivity that collects information requests from mobile users and delivers data while users are going through the coverage area. Infostations can be located in heavily populated areas such as airports, shops, pubs, hotels, and along highways. One of the technologies that have the potential to deliver the envisaged high-data rate infostation services is the UWB signaling [3]. The UWB has the basic attributes of extremely low transmission power, operating at unlicensed frequency, high data rate, multipath immunity and low cost. Existing channel characterization and measurement for the UWB channel have been limited to the case where the channel is assumed to be stationary over the transmission duration. However, for many infostation scenarios, time variation is expected due to the mobility of one of the communication terminals/scatterers. Hence, the existing channel models cannot be used to describe this new target scenario where terminal mobility is expected. Time-varying channels are often modeled as stationary random processes using the concept of the wide-sense stationary uncorrelated scattering (WSSUS) assumption [4]. Unfortunately, in time-varying UWB channel, the WSSUS assumption is invalid. The nature of the time-varying channel is such that the spatial structures of the multipath components, i.e., their number, time- of-arrivals (TOA), angle-of-arrivals (AOA) and magnitudes, change with time and location, leading to nonstationary statistics. Hence, non-WSSUS characterization [5, 6] of the channel is required. For the UWB channel, the fine time resolution implies narrow delay bins which enable paths to move fast from one tap to another [7]. Hence, the time evolution of the UWB channel cannot be decomposed into the time evolution of the individual taps, but of the individual paths. In this article, we present the measurement and the descriptions of channel parameters for the time-varying Infostation UWB channel. We also consider how such parameters can be used to improve system performance in terms of combating ICI in the case of multiband OFDM and mismatch in channel estimation. The rest of this paper is organized as follows. In Section 2, the basic system model is specified. The Infostation UWB channel measurement setup is presented in Section 3. Section 4 is devoted to describing the post processing of the measurement data and the description of the how the channel parameters can be used to improve system performance in terms of optimally combating ISI and ICI in the case of multiband OFDM. 2. SYSTEM MODEL Channels can be characterized by their response function in time and/or frequency domain say P (t, f ). The variation among the statistics of the measured channel responses taken over a given appreciable interval is assumed to be insignificant (stationary) in the WSSUS case. Unfortunately, in time-varying UWB channel this is not the case as the channel is non-WSSUS. In essence, non- WSSUS scattering function can be viewed as a set of evolutionary functions that are more or less the instantaneous responses P (t, f ) i , i =1, 2, 3,...,I of the channel to an input. Although the coherence parameters of these instantaneous channel realizations vary from one to another, for practical rationality we consider channel coherency only with respect to the reference channels response regard as being WSSUS say P (t, f ) 1 . The coherency of P (t, f ) 1 is ensured by restricting