Synchronous Impulse Networks by Chee

A synchronous impulse network (SIN) is defined to be a network of spatially distributed wireless nodes employing UWB impulse transceivers whose oscillators are "ticking" at the same time/phase. In this research, the ultra-wide bandwidth of UWB signals is exploited to provide high resolution timing synchronization. The network node in the proposed synchronization scheme measures the time-of-arrival (ToA) of UWB monocycles transmitted from other nodes in the network. The measured ToAs are impaired by additive channel noise, oscillator phase noise and may correspond to ToA of signal arrived via non-line-of-sight (NLoS) propagation. To perform time transfer between network nodes, the designated master node transmits frame-synchronization pulses to slave nodes to align slaves' oscillator frame repetition rate with that of master. This is followed by two-way ranging using the master as the transponder to mitigate signal propagation delay. This allows a node in the SIN to estimate, from the measured ToAs, the initial offset differences between itself and the master nodes. It is assumed that the UWB monocycles occupy all the available bandwidth and network nodes transmit UWB impulses only in pre-assigned time slots. Thus the proposed synchronization scheme uses only one physical channel for time transfer and logical channels are formed via time division multiplexing. The 'roving' master concept for time transfer, whereby each node takes a turn as the master node, is also proposed in this research. The main objective of roving the network's nodes is to overcome blockages to network signal propagation paths and to extend the coverage of the synchronous network. The roving masters form either the mutually synchronous (MU) or hierarchical master-slave (HM) time transfer network architectures and their performances are compared with a single-master time-transfer architecture (SM).