Ultrawideband Channel Modeling on the Basis of Information-Theoretic Criteria

We present results of two indoor ultrawideband channel measurement campaigns in the 2-5 GHz frequency band. In measurement campaign I (MC I), the channel is static and we sample it spatially, while in MCII the transmitting and receiving antennas are fixed and channel variation is induced by people moving in the environment. Transmitter and receiver are separated by up to 27 m in MC I and up to 20 m in MC II. To determine suitable small-scale fading distributions for the tap amplitudes of the discrete-time baseband-equivalent channel impulse response, we use Akaike's information criterion (AIC). Despite the large bandwidth, AIC supports the Rayleigh (MCI) or the Rice distribution (MC II). For data from MC II, we estimate the covariance matrix of the random channel impulse response and demonstrate that the number of corresponding significant eigenvalues, and hence the diversity order of the channel, scales approximately linearly with bandwidth. Contrary to the uncorrected scattering assumption, we find that the channel taps are weakly correlated. The ergodic capacity predicted by the Ricean channel model with parameters estimated from MC II shows good agreement with the ergodic capacity obtained by direct evaluation of the measurement results, while the corresponding outage capacities show a worse fit for low outage probabilities because of shadowing.