Time-scale domain characterization of non-WSSUS wideband channels

Abstract

To account for nonstationarity, channel characterization and system design methods that employ the non-widesense stationary uncorrelated scattering (non-WSSUS) assumption are desirable. Furthermore, the inadequacy of the Doppler shift operator to properly account for the frequency shift in wideband channel implies that the timefrequency characterization methods that employ the Doppler shift operator are not appropriate for most wideband channels. In this article, the statistical time-scale domain characterization of the non-WSSUS wideband channel is presented. This approach employs the time scaling operator in order to account for frequency spreading, and also emphasizes on the nonstationarity of the wideband channel. The non-WSSUS statistical assumption termed localsense stationary uncorrelated scattering (LSSUS) is presented and employed in characterizing the nonstationary property of the time-varying wideband channel. The LSSUS channel model is then parameterized to provide useful coherence and stationarity/nonstationarity parameters for optimal system design. Some application relevance of the developed model in terms of channel capacity and diversity techniques are discussed. Measurement and simulation results show that the assumption of ergodic capacity and the performance of various diversity techniques depend on the degree of channel stationarity/nonstationarity. It is shown that the quantification of this degree of stationarity through the channel parameters can provide a way of tracking channel variation and allowing for adaptive application of diversity techniques and the channel capacity.

Generic stochastic modeling of vehicle-to-vehicle wireless channels

“…In other words, the LSF is invariant with frequency provided that the time intervals have been selected such that the WSS assumption in the time-domain holds [26]. Another contribution of modeling WSS in time-domain through the LSF can be seen in [30].…”

Channel measurement and time dispersion analysis for outdoor mobile ultrawideband environment

“…In an alternative approach, and inspired by Matz [21], the concept of local-sense stationary uncorrelated scattering (LSSUS) was introduced by Chude-Okonkwo et al [22]. The LSSUS concept was used to define the stationarity bandwidth and time using the definition of minimal RMS delay spread deviation ∆τ RM S and minimal scale spread deviation ∆s max for wideband channels (and consequently minimal Doppler spread deviation for narrowband, if required), respectively.…”

“…The values ∆τ RM S and ∆s max were alternatively defined as deviations in delay ( τ ) and scale ( s) (in relation to Doppler spread) of a given LSSUS channel realization from the reference WSSUS values. The expression for the LSSUS scattering function, which is an evolutionary spectrum, is given by Chude-Okonkwo et al [22]:…”

“…A number of perspectives have been used in the literature to assess the stationarity dimension of the time-varying channel. Some are based on the variation in first-order statistics [20], while others are based on second-order statistics of the channel [20][21][22]. In [20] the stationarity region, termed the local region of stationarity (LRS), was defined based on the change of the PDP P H (t, τ ) with respect to locations.…”

“…Hence, to quantify the deviation of LSSUS from WSSUS, the minimal delay profile deviation (MDPD) Ξ 2 τ and the minimal scale profile deviation (MSPD) Ξ 2 S are defined and expressed as [22]:…”