Measurements, modeling and simulations of the UWB propagation channel based on direct‐sequence channel sounding

Abstract

The paper presents the statistical model for the ultra-wideband (UWB) indoor channel having a bandwidth of 2.4 GHz and a central frequency of 4.78 GHz. The model is based on propagation experiments performed in different rooms on a floor of an office-laboratory building. Within each room the receiver antenna is automatically moved over a square grid of 25 Â 25 locations spaced 2 cm apart. A correlative channel sounding technique is employed; actually the carrier is modulated by a train of short duration (0.4 ns) pulses shaped by a PN-sequence. After coherently demodulating the detected signals and removing the PN-sequence modulation, we post-process the extracted channel impulse responses by best-fit procedures to set up a statistical tapped delay line model (STDL) of the UWB indoor channel. We characterize the path loss for line-of-sight (LOS) and non-line-of-sight (NLOS) conditions by distance-power laws and the shadowing by lognormal distributions. A clustered structure is observed in the average power-delay profiles; rays arrive at the receiver in groups, exponentially decaying with different decay constants. The small-scale effects are modeled by the Gamma distribution since it verifies with a 95%-confidence interval both the Chi-Square test and the Kolmogorov-Smirnov test applied to the experimental data. The shape parameters of such Gamma distributions are truncated Gaussian variables spreading in the range from 1 to 3. An implementation of the derived STDL model is finally proposed and a comparison between the simulated and the measured statistics is performed proving the validity of our approach.

Rake performance for DS and TH based UWB system in a multipath channel

“…However, due to the optimal energy collection performed by the Rake receiver, better performances (i.e. smaller values of gP and gN ) are achieved when the pulse duration equals the delay difference between subsequent MPCs (1 ns according to the adopted propagation model [4]). …”

“…. , M. P L0 and P Lm in (5) are the path loss attenuations relative to the reference and the interfering users, generated according to the path loss model presented in [4]. As for coefficients gP and gN appearing in (5), they are equal to the inverse of the processing gains introduced by the Rake with respect to interference and noise, respectively.…”

“…where {hi} and {τi}, i = 0, 1, ..., H − 1 (being H the number of arrived paths), are the channel taps coefficients and the corresponding path delays, respectively, generated according to the NLOS channel model in [4]. To point out the path loss contribution, the coefficients hi in (9) can be written as: hi = √ P L0hi, where P L0 is the attenuation due to path loss relative to the reference user andhi is a complex random variable accounting for fast fading.…”

“…In this paper 2 , we adopt a semi-analytical approach to evaluate the capacity of UWB systems based on DS-Pulse Amplitude Modulation (DS-PAM) and Time-Hopped Pulse Position Modulation (TH-PPM). In order to provide realistic results, we consider the UWB indoor channel model proposed in [4] and derived by a pseudo noise (PN)-sequence measurement campaign over the band 3.6 − 6 GHz, for non line-of-sight (NLOS) communications in office environment with dense multipath. A Rake receiver scheme is adopted to exploit multipath diversity.…”

Path loss and time dispersion analysis for outdoor roadway UWB propagation channel

“…We conducted the measurement on Saturday, June 1, 2013, from 9.00 am to 10.30 am. The choice of time was to help reduce the influence of mobile scatterers and maintain a stationary channel throughout the measurement in described in [17].…”