8 results about "Preamble" patented technology

In an oversampled orthogonal frequency-division multiplexing (OFDM) orthogonal network, the preamble used for time synchronization does not have an ideal autocorrelation function due to guard bands, which degrade the accuracy of symbol timing. Therefore, a zero-correlation-zone (ZCZ) based preamble is used for time synchronization. Across correlation function (CCF) used for time synchronization is forced to 0 within a certain region around a main lobe. The length of the ZCZ is guaranteed to be larger than a cyclic prefix length of OFDM data symbols synchronization accuracy.

The present invention discloses a host receiver synchronizer for passive optical networks, and in particular a burst clock data recovery circuit in a host receiver in a bursty asynchronous communication system having a non-data preamble of less than 250 ns, for recovering a clock signal from a subscriber data burst. The circuit comprises: an adjustable oscillator for generating an output clock signal in response to a signal at an input thereof; a first comparator for comparing a frequency and phase of the output clock signal to that of a reference signal and feeding back a first feedback signal to the oscillator input; and a second comparator for comparing the frequency and phase of the output clock signal to that of the data burst and feeding back a second feedback signal to the oscillator input once the output clock signal is locked in frequency with the reference signal. The output clock signal is locked in frequency and phase to the data burst before receipt of the last bit of the preamble. The present invention is advantageous in that the receiver circuit improves synchronized jitter performance over the prior art solutions so that additional timing margin is provided, thereby allowing longer fiber lengths to be supported.

A system and method of retaining synchronization in a shared medium communications network. Synchronization is maintained between colliding transmitters and receivers by providing a Collision Based Inter Frame Space (CBIFS) which is a time period at least as long as the longest frame and that starts from a point in time common to all nodes such as after the backoff period (beginning of the PHY header). After a collision is detected in either a transmitting or receiving node, the node waits the remaining time in the CBIFS period. For transmitters the node waits the remaining time period from the end of the frame transmission until the CBIFS period terminates. For receivers, the node waits from the end of the preamble until the CBIFS period terminates.

A transmitter including a signal generator to generate an analytic signal in frequency domain, having frequency components that when converted to time domain result in a time domain signal with a preamble that includes a first half of containing non zero information and a second half containing only zero data. A shaper configured to generate a cyclic prefix including only zero data based on the second half of the preamble included in the time domain signal, and to attach the cyclic prefix including only zero data to the time domain signal to output a pilot signal that is to be transmitted via an antenna.

The invention relates to a blind estimation method for the signal to noise ratio of an OFDM system, and belongs to the technical field of wireless communication. Data subcarrier mean power and virtual carrier mean power are obtained on the basis of preambles of signal frames of the OFDM system, and further the signal to noise ratio is determined. Thus, the communication efficiency is higher compared with a pilot-aided estimation method for the signal to noise ratio in the prior art; the estimation precision is higher compared with a signal to noise ratio estimation method in which virtual carriers are used, and the blind estimation method of the invention is low in complexity, easy to realize and low in realization cost.

In the present disclosure, a transmitting device transmits a first message comprising i) a first random access preamble with a first random access preamble identifier (RAPID) and ii) a first uplink payload; receives a random access response (RAR) medium access control (MAC) protocol data unit (PDU) including i) a first field set to represent presence of one or more RAPIDs and ii) the one or more RAPIDs; determines whether both of the first RAP and the first payload is successfully transmitted, based on whether the one or more RAPIDs include the first RAPID; and monitors a second message related to the first message based on determining that both of the first RAP and the first payload is successfully transmitted.