Detection, Synchronization, Channel Estimation and Capacity in UWB Sensor Networks using Compressed Sensing.

Abstract

Conventional receivers in ultrawideband (UWB) communication system usually require high sampling rate and thus consume much power. With compressed sensing (CS), the sampling rate can potentially be reduced. In this thesis, the performance of CS used in a UWB receiver is evaluated. Using a compressed sensing approach, the receiver consists of a number of analog correlators that process the received signal by projecting the received signal using random (or pseudo random) vectors. Considering the practical implementation in the receiver, the orthogonal Hadamard vectors in the correlators are adopted. After projection, the matching pursuit or basis pursuit is used to obtain the channel estimate. The recovered channel templates are then correlated with received signal to detect the transmitted information bits.

The bit error rate (BER) performance of systems with different number of pilots, projection vectors, and fingers in a rake receiver is also evaluated. Moreover, the performance of different receivers and the effect of the finite bit resolution on channel estimation is investigated. It is shown that the sampling rate can be reduced significantly with only a slight degradation in performance when a compressed projection matrix is used compared to when a conventional Nyquist sampling rate is applied.

A second aspect of UWB investigated is channel measurement and corresponding channel capacity. The measurement data of a channel between the UWB antennas under the bridge across Telegraph Road in Michigan is used to calculate the channel capacity. The channel capacity calculated in this specific environment provides the knowledge of the fundamental limit of rate of transmission in this particular scenario.

A third aspect of UWB communication considered involves the synchronization and detection of signal presence. An m-sequence is used to synchronize the signal. The corresponding BER performance is evaluated. It is observed that the BER performance of the proposed synchronization method is comparable to that of a system assumed to have perfect synchronization. Finally, the autocorrelation characteristic of the signal is exploited to detect the existence of the signal. The advantage of the method proposed is that the threshold to determine the existence of signals is independent of signal-to-noise ratio.