Low-complexity synchronization algorithms for orthogonally modulated IR-UWB systems

Abstract

Timing synchronization is a major issue for any communication system since it is essential to ensure its stable operation and reliable performance. In this paper, we compare two low-complexity synchronization algorithms for impulse radio ultra-wideband (IR-UWB) system, employing orthogonal pulse shape modulation (PSM). The two widely adopted modulation schemes for IR-UWB systems are binary pulse amplitude modulation and binary pulse position modulation. However, the possibility of generating orthogonal UWB pulses in recent years has motivated the use of orthogonal PSM which is particularly attractive as high-order modulation and also due to its possible robustness against ISI, and therefore is the focus of this paper. Relying on the unique signal format, the first algorithm applies simple overlap-add operation followed by energy detection to achieve synchronization. This approach is semi non-data-aided (NDA) because a part of the signal is specifically reserved to help enable synchronization. The other algorithm, on the other hand, exploits the discriminating nature of well-designed polarity codes and employs a series of code word matching and averaging operations to achieve synchronization. This approach is full NDA as there is no need to interrupt the data transmission. Based on the judicious change in the phase of transmitted signal applied for synchronization purposes, the second algorithm can also be used to extract synchronized aggregate templates. These templates are then used in demodulation, resulting in a low-complexity non-coherent alternative to complex Rake receivers. The two compared timing algorithms rely on simple overlap-add operations and thus remain operational under practical UWB settings. Simulation results are provided to demonstrate the efficient performance of proposed timing estimators.