62 results about "Sync word" patented technology

With audio data reduction on the basis of ISO/IEC standard 11172-3, a frame length varying by 8 bits is used at a sampling frequency of 44.1 kHz in order to arrive, on average, at a particular fixed data rate. The lengthening of a data frame is signalled by a padding bit in the header of the frames. The invention dispenses with evaluation of the padding bit. Instead, the mean frame length L is calculated, L is rounded down to the next integer, for the subsequent frame it is first established whether the expected sync word for this frame appears, and, if this is so, this frame is decoded without taking into account the padding bit, but if the expected sync word for this frame does not appear, the decoding of the frame is started one 8-bit later without taking into account the padding bit.

In RF transceivers, a method and system for using phase shift key (PSK) sync word for fine tuning frequency adjustment are provided. One aspect of the invention provides for adjusting a local oscillator frequency in a radio frequency (RF) receiver when a residual DC offset remains after a coarse frequency offset adjustment if performed. The fine adjustment may be necessary because of the synchronization required with a PSK-based modulated portion of a Bluetooth packet. A residual phase shift detected in a sync sequence portion of the Bluetooth packet may be utilized to determine a residual or fine frequency adjustment. This approach may allow an RF receiver to operate, in some instances, without the need for an equalizer. In this regard, the power consumed by the RF receiver may be minimized and/or the overall cost of the RF receiver may be reduced.

A method and system for communicating signal data in GNSS system using LDPC convolution codes. The method involves, at transmitting end, formatting signal data into a set of subframes. Each subframe of the signal data can be encoded in accordance with a parity check matrix defining Tanner graph representation of LDPC convolution codes. The encoded signal data can be interleaved and added with a Sync word field to transmit an interleaved block of encoded signal data through a communication channel. At receiving end, the interleaved block of encoded signal data can be de-interleaved after it is received from the communication channel. The Tanner Graph shows the connectivity in time invariant parity check matrix. A message passing technique is used to decode the LDPCCC encoded message. The encoded signal data can be decoded through the message passing technique to obtain the signal data primitively transmitted at the transmitting end. Such method and system are capable of achieving error free performance over the GNSS communication channel for effective navigation data communication, and also provide good BER performance over a wide range of Signal-to-Noise ratios.

The portion of TDMA frames otherwise containing the sync word is eliminated for one or more data frames at the end of a TDMA data burst to provided added bandwidth for data payload or for a reduced bandwidth. Once a communication channel has been established and is in steady state mode (after receipt of one or more frames), the sync word is eliminated from the remaining frame structure. Drift of a local clock with respect to an incoming data stream is monitored using an oversampled or multiplied master clock to provide suitable resolution to determine an approximate position of an active edge of the master clock with respect to a bit or symbol being clocked. Any drift from center results in an adjustment of the local master clock. In a preferred embodiment, the drift is measured in a last bit or symbol of a received TDMA burst, and the master clock is adjusted to re-center the local master clock with respect to that last bit. Accordingly, the receiver is "tuned' to the clock signal of the transmitting TDMA device such that the receiving TDMA device can predict where the next start of frame will occur. By doing so, the sync word is no longer necessary in the remaining frames of the TDMA burst to decode the start of next TDMA frame. The sync word may be included in more than one frames in the beginning of the TDMA burst, but is eliminated from one or more frames at the end of the TDMA burst.

Both a pre-word (PW) and a sync word (SW) are used to establish a synchronization or only the sync word (SW) is used to establish a synchronization in accordance with an operational status related to the synchronization in a mobile wireless communication apparatus. For example, during an initial synchronization with a control channel (110) being received, both the pre-word (PW) and the sync word (SW) are used to establish a synchronization when a calculation result in a synchronization calculating part exceeds a predetermined threshold value only once. During an initial synchronization with a direct communication channel (112) being received, both the pre-word (PW) and the sync word (SW) are used to establish a synchronization when the calculation result exceeds the predetermined threshold value once; or alternatively, only the sync word (SW) is used to establish a synchronization when the calculation result successively exceeds the predetermined threshold value twice. According to the present invention, the sync word is shortened so as to quickly establish a communication link, and the sync detection can be performed with high precision.

The invention relates to a method for synchronizing data frames. The method comprises the following steps: capturing sync words in the data frames, and outputting a capture indicator signal and a capture sync word serial number; according to the capture indicator signal, the capture sync word serial number and a current count value, executing multiplex synchronization lock, computing and latchingthe frame head position, and outputting a locked signal and an empty/full indicator signal, wherein the count value is obtained by executing a cycle count taking a frame length as a cycle to the received data frames, the empty/full indicator signal comprises an empty state and a full state respectively indicating unlatched and latched; according to the locked signal, outputting a locking indicatorsignal, outputting a frame head indicator signal according to the current count value, and outputting a write enable signal according to the empty/full signal, wherein the write enable signal is usedfor coordinating the multiplex synchronization lock. The invention achieves a fast, exact and stable data frame synchronizing method.

A frame synchronization apparatus and method based on differential correlation in a communication system are provided. A correlation analysis is performed by using sync word in a prior search window and a posterior search window for obtaining a plurality of prior-window correlation values and a plurality of posterior-window correlation values, respectively. N maximum correlation values in the correlation values are selected, wherein indexes of the maximum correlation values are I₁˜I_N, and N is an integer greater than 0. The posterior-window correlation values are compared with a first threshold. If one of the posterior-window correlation values is greater than the first threshold, the index of the one is defined as J. If the index J is equal to one of the index I₁˜I_N, a check step is performed by using the index J for confirming that a position of the index J is a header position.

In a transmitter, a motion detector detects a motion amount of a coded block. A buffer memorizes a detected motion amount. A buffer controller controls the buffer to read the motion amounts in the order opposed to the writing order. A switch selects one of outputs. In a receiver, a sync word detector discriminates first and second sync words. A primary frame memory memorizes an actually decoded image. A secondary frame memory memorizes a predicted image corresponding to the actually decoded image. Memory controllers read out the image information of coding blocks from the corresponding frame memories in an order opposed to the writing order. A switch selects either one of the information of the primary or secondary frame memories.

In a channel estimating circuit, a Sync Word is demodulated by using a channel estimation value not with a symbol or a slot including the Sync Word to be demodulated, but with its preceding and succeeding symbols or slots. Furthermore, in a channel estimation process, if a Synch Word to be demodulated is included in any of groups into which a plurality of symbols are divided, the Sync Word is demodulated by using a channel estimation value obtained with the channel estimation process using not this group but another group.