Synchronizing a pulse position modulation (PPM) signal. A method includes performing a first synchronization operation by receiving a first series of symbols. The symbols in the first series are transmitted with a pulse in a known slot, such that the symbols comprise pulses that are substantially equally spaced in time from adjacent symbols. The first synchronization operation includes identifying when each pulse is received for each of the symbols and using information identifying when each pulse is received for each of the symbols in the first series of symbols to identify symbol and slot boundaries for the pulse position modulation signal. The method further includes performing a second synchronization operation by receiving a second series of symbols transmitted in a known pattern, and identifying the known pattern in the received second series of symbols to identify a frame boundary.

The present disclosure relates to the field of synchronising a radio frequency (RF) communication system based on the repeated transmission of data at the transmitter and the use of a method for the time synchronous averaging of this data at the receiver. The proposed communication technique uses the fact that the data signal is periodically repeated, without requiring the use of synchronisation data external to the data to be communicated. It enables phase and frequency synchronisation to be maintained when the received signals are very noisy, and even when they have a signal-to-noise ratio of less than 1 or even a negative signal-to-noise ratio (in dB). A significant improvement in the processing gain of the method for time synchronous averaging is advantageously achieved.

A communication device includes an interleaving unit that determines an interleaving length of transmit data to be transmitted through free-space optical communication, and interleaves the transmit data based on the determined interleaving length, and a shaping unit that shapes the interleaved transmit data so as to make the interleaving length detectable on a receiving side of the free-space optical communication.

The embodiment of the present disclosure provides a time code synchronization method, which includes following steps of: determining a target master node and one or more target slave nodes of a network system among the plurality of nodes; periodically sending a data packet to the one or more target slave nodes by the target master node, wherein the data packet includes a first time code and serial number information of the target master node; compensating the first time code according to the serial number information to obtain a second time code, and synchronizing the second time code by the one or more target slave nodes.

A communication device includes an interleaving unit that determines an interleaving length of transmit data to be transmitted through free-space optical communication, and interleaves the transmit data based on the determined interleaving length, and a shaping unit that shapes the interleaved transmit data so as to make the interleaving length detectable on a receiving side of the free-space optical communication.

A method and system for multipulse-pulse position modulation optical transmission that includes selecting a multipulse-pulse position modulation having a symbol alphabet having an upper-bound symbol alphabet size, and determining, based on at least one transmission characteristic associated with a transmitter, a subset of symbols of the selected symbol alphabet capable of being transmitted by the transmitter, the subset of symbols having a set of binary codewords. The method and system may include identifying two-symbol concatenation of binary codewords in the set of binary codewords, calculating a cross correlation of binary codeword in the set of binary code words through every two-symbol concatenation, determining a set of one or more acceptable codeword combinations by eliminating a portion of two-symbol concatenation of codewords corresponding to overlapping peaks in the respective calculated cross correlations, and transmitting, by the transmitter via an optical communication channel, information encoded based on the determined acceptable codeword combinations.

A receiving device includes: a receiver that receives a signal including PPM symbols; a clock generator that generates a clock for sampling; an A/D converter that digital-converts the received signal; a reference position detector that detects a leading position of the PPM symbols based on data from the A/D converter; and a clock error detector that detects a clock error. The clock error detector includes: a pulse position detector that detects a pulse position in the PPM symbols based on data from the reference position detector and A/D converter; a position error calculator that calculates a deviation of the pulse position based on data from the reference position detector, A/D converter, and pulse position detector; and a clock error calculator that calculates the clock error based on data from the position error calculator. The receiving device varies a frequency of the clock based on data from the clock error calculator.

A clock data recovery circuit detects illegal decisions for received data, accumulates a phase gradient for the data, determines a number of the illegal decisions in a configured window for receiving the data, and if the number of the illegal decisions exceeds a pre-defined number in the window, applies a sum of the accumulated phase gradient and a phase increment having a sign of the accumulated phase gradient to a clock circuit for the data receiver.

A coded light receiver comprising a sensor for receiving coded light, a filter, and a timing and data recovery module. The coded light comprises a signal whereby data and timing are modulated into the light according to a self-clocking coding scheme. The filter is arranged to match a template waveform of the coding scheme against the received signal, thereby generating a pattern of filtered waveforms each corresponding to a respective portion of the data, and the timing and data recovery module recovers the timing from the signal based on characteristic points of the filtered waveforms. The timing and data recovery module is configured to do this by separating the filtered waveforms into different sub-patterns in dependence on the data, and to recover the timing by processing each of the sub-patterns individually based on the characteristic points of each sub-pattern.

Ultra-Wideband (UWB) wireless technology transmits digital data as modulated coded impulses over a very wide frequency spectrum with very low power over a short distance. Accordingly, the inventors have established UWB devices which accommodate and adapt to inaccuracies, errors, or issues within the implemented electronics, hardware, firmware, and software. Beneficially, UWB receivers may accommodate offsets in absolute frequency between their frequency source and the transmitter, accommodate drift arising from phase locked loop and/or from relative clock frequency offsets of the remote transmitter and local receiver. UWB devices may also employ modulation coding schemes offering increased efficiency with respect to power, data bits per pulse transmitted, and enabled operation at higher output power whilst complying with regulatory emission requirements. Further, UWB devices may support a ranging function with range/accuracy not limited to the low frequency master clock employed within these devices enabling operation with ultra-low power consumption.