Research On Compressed Detection Based UWB Communication Systems

Ultra-wideband (UWB) represents a new paradigm in wireless communication. The unprecedented radio bandwidth provides many advantages, such as immunity from flat fading. At the same time, UWB faces challenges:according to Shannon/Nyquist sampling theorem, UWB receivers need extremely high sampling rate of analog to digital conversion (ADC). The high rate of ADC is expensive, which limits the development of UWB technology application.Compressed sensing (CS) theory provides an efficient way to acquire and reconstruct sparse signals from a limited number of linear projection measurements leading to sub-Nyquist sampling rates. The advantages of compressed sensing theory include simpler hardware design, faster acquisition time, etc. This thesis proposes two ways to apply compressed sensing theory into the UWB system, which researches the performance in the aspects of bit error rate (BER) or systematic complexity. The main contributions of this thesis can be summarized as follows:1. Existing CS-based UWB receivers need real-time channel estimation to improve the BER performance, but real-time channel estimation imposes high complexity on UWB receivers. In chapter3, a new measurement matrix is exploited in the design of impulse UWB receiver. The new measurement matrix is constructed based on the statistical property of UWB multi-path signals. As a result, the impulse UWB receiver doesn’t need real-time channel estimation any longer. Using the new measurement matrix, the UWB receiver gains satisfactory BER performance with low complexity. Simulation results show that, the proposed receiver outperforms UWB receivers using channel time-delay measurement matrix in BER performance when the sampling rate is less than7.5%of the Nyquist sampling rate. What’s more, the lower the sampling rate is, the more advantages the proposed receiver has in terms of BER.UWB systems usually have one transmitter and one or more receivers. A natural question arises:can we move part of the hardware complexity of the receiver to the transmitter side to reduce the cost of UWB systems? Based this idea, we propose a new UWB system. In the new UWB system, measurement matrix module is moved from the receiver to the transmitter. At the same time, the channel itself is exploited as part of the measurement matrix. Only one receiving antenna module, one low-rate ADC module and one detection module are used at the receiver. In comparison with the receiver proposed in chapter3, the complexity of the new UWB receiver is reduced further. Simulation results show that, the new UWB system can be used to achieve satisfactory BER performance and lower the complexity of the receiver.