950 results about "Guard interval" patented technology

Systems and methods are provided for determining a link metric for a communication link along a path between a source node to a destination node is provided. A node can generate a link metric (LM) for the communication link between the particular node and next-hop node towards the destination node in the path based on a plurality of variables. The node can determine the LM for the communication link based on a plurality of variables including: bandwidth on the communication link, a number of spatial streams used to transmit over the communication link, and a guard interval used used to transmit over the communication link.

Multiple Transmit Multiple Receive Orthogonal Frequency Division Multiplexing (‘OFDM’) comprising generating bit streams and corresponding sets of N frequency domain carrier amplitudes ({tilde over (s)}(kN+j), 0≦j≦N−1) modulated as OFDM symbols subsequently to be transmitted from a transmitter, where k is the OFDM symbol number and j indicates the corresponding OFDM carrier number. Affix information is inserted at the transmitter into guard intervals between consecutive time domain OFDM symbols and are used at the receiver to estimate the Channel Impulse Response (H_lm) of the transmission channels, the estimated Channel Impulse Response (Ĥ_lm) being used to demodulate the bit streams in the signals received at the receiver. The affix information is known to the receiver, as well as to the transmitter, and is mathematically equivalent to a vector (c_D) that is common to the time domain OFDM symbols multiplied by at least first weighting factors (α_k) that are different for one time domain OFDM symbol (k) than for another and second weighting factors (w_i(k)) that enable one of the transmit antenna means (i) to be distinguished from another.

An apparatus and a method for reducing an error vector magnitude in an orthogonal frequency division multiplexing (OFDM) receiver. The method includes the steps of inputting a receiving symbol including a guard interval and an effective symbol interval following the guard interval, in which a front portion of the guard interval and a rear portion of the effective symbol interval have windowing intervals corresponding to windowing of a transmitter, and replacing a signal of the rear windowing interval with a signal of an interval between the front windowing interval and the effective symbol interval, thereby outputting a signal of the effective symbol interval, which substitutes for a signal of the rear windowing interval, to a fast Fourier transform (FFT) section.

Signals (typically in the form of OFDM signals) are transmitted between one or more transmitting antennas and one or more receiving antennas. The signals transmitted are subject to addition of a guard interval before scrambling in the time domain, while the signals received are subject to removal of the guard interval after scrambling in the time domain. Preferably time-scrambling of the OFDM signal being transmitted occurs after IFFT processing and guard interval insertion, while time de-scrambling of the signal being received occurs before both guard interval removal and FFT processing. Optionally, unscrambled pilot symbols (e.g. in the form of a training sequence), can be present at regular intervals inside the signal structure. At the receiver, equalization is carried out preferably in the frequency domain.

Aspects of the invention are directed to a cell-frequency-link descriptor configured to map network-specific parameters with time frequency slicing (TFS) information in a digital video broadcast system. The cell-frequency-link descriptor may include fields that provide a mapping between a cell identifier, a TFS group identifier, a bandwidth, a guard interval, a transmission mode, and a frequency. The fields may provide a mapping between cells, frequencies, TFS groups, related guard intervals, bandwidths, and transmission modes for multiple cells within the digital video broadcast system. The fields may include: a cell identifier field, a TFS-group identifier field, a bandwidth field, a guard interval field, a transmission mode field, a frequency field, a cell identifier extension field, and a transposer frequency field.

An OFDM demodulation (1) is provided which includes a guard correlation/peak time detection circuit (12) to generate a peak timing Np of a guard interval correlation value, and a timing synchronization circuit (13) to estimate a symbol-boundary time Nx from the peak timing Np. The timing synchronization circuit (13) calculates the symbol-boundary time Nx by filtering the peak time Np by a DLL (delay locked loop) filter (43). Further, the DLL filter (43) includes a limiter (52) to limit the range of phase-error component and an asymmetric gain circuit (53) to change the magnitude of the gain correspondingly to the polarity of the phase error to prevent the timing from being pulled out due to a fading or multipath.

Embodiments are directed to binary phase shift key modulating a first pilot symbol according to a reference sequence, and differentially binary phase shift key modulating a second pilot symbols. The original reference sequence and the delayed differentially modulated sequence are then combined before performing an Inverse Fast Fourier Transform and inserting a guard interval. Receiver operations are an inverse of the transmitter operations, which were just discussed. The receiver does not have to know the reference sequence. Embodiments are directed to specifying a plurality of seeds that are bit patterns each having r bits not all of which have a value of zero, extending the seeds into respective sequences by applying to each seed a recurrence formula; and using one of the sequences as a comb sequence and using the sequences other than the comb sequence as binary phase shift keying patterns.

A method for generating a preamble of a frame for a multiple input multiple output (MIMO) wireless communication begins by, for each transmit antenna of the MIMO wireless communication, generating a carrier detect field, wherein, from transmit antenna to transmit antenna, the carrier detect field is cyclically shifted. The method continues by, for a first grouping of the transmit antennas of the MIMO wireless communication: generating a first guard interval following the carrier detect field; and generating at least one channel sounding field, wherein, from transmit antenna to transmit antenna in the first grouping, the at least one channel sounding field is cyclically shifted, and wherein the at least one channel sounding field follows the first guard interval. The method continues by, when the MIMO wireless communication includes more than the first grouping of the transmit antennas, for another grouping of the transmit antennas: generating at least one other channel sounding field, wherein, from transmit antenna to transmit antenna in the another grouping, the at least one other channel sounding field is cyclically shifted, and wherein the at least one other channel sounding field follows the at least one channel sounding field; and generating the first guard interval prior to the at least one other channel sounding field.

A method and transceiver for wireless multicarrier communications. At the transmitter side, conventional OFDM symbols, after inverse fast Fourier Transform, are scrambled in time domain and then guard-interval (GI) inserted, up-converted at the carrier frequency for transmission. At the receiver side, after GI removal and frequency domain channel equalization, the received signal is transformed into time-domain by inverse fast Fourier Transform. The time-domain equalized signal is descrambled in time domain and then transformed back to the frequency domain before it is rate-matched, demodulated and decoded. This time-domain scrambling and descrambling method can be used in a wireless OFDM system such as WLAN, cellular OFDM, and MC-CDMA.

A method of estimating timing of at least one of the beginning and the end of a transmitted signal segment in the presence of time delay in a signal transmission channel. Each of a sequence of signal frames is provided with a pseudo-noise (PN) m-sequences, where the PN sequences satisfy selected orthogonality and closures relations. A convolution signal is formed between a received signal and the sequence of PN segments and is subtracted from the received signal to identify the beginning and/or end of a PN segment within the received signal. PN sequences are used for timing recovery, for carrier frequency recovery, for estimation of transmission channel characteristics, for synchronization of received signal frames, and as a replacement for guard intervals in an OFDM context.

Embodiments of cyclic diversity systems and methods are disclosed. One system embodiment, among others, comprises a logic configured to cyclically advance, or perform the periodic equivalent of the same, one or more sections of an orthogonal frequency division multiplexing (OFDM) packet relative to the OFDM packet to be transmitted on a first transmit antenna, the packet having the one or more cyclically advanced sections to be transmitted on a second transmit antenna, the duration of the cyclic advance having a duration less than a guard interval.

A transmitter transmits payload data using Orthogonal Frequency Division Multiplexed (OFDM) symbols. The first OFDM symbol is a first type having a number of sub-carriers which is less than or equal to the number of sub-carriers of the one or more second OFDM symbols of a second type and a guard interval for the first OFDM symbol is selected in dependence upon the longest possible guard interval of the second OFDM symbol. Accordingly an OFDM communications system can be formed in which data is transmitted using a frame structure in which a guard interval is adapted to allow a mix of different types of OFDM symbols.

The invention discloses a device discovering method used for device-to-device communication. The method comprises that a user equipment UE transmits a discovery channel used for discovering equipment, wherein the discovery channel comprises at least an information portion and a protection interval portion; that the information portion is used for identifying the UE; that the protection interval portion is used for separating the discovery channel from other channels in time domain; and that other channels are device-to-device communication channels or cellular communication channels transmitted from other UE. The invention also discloses a device discovering apparatus used for device-to-device communication. The technical scheme of the invention resolves a device discovery problem of D2D communication in a cellular communication system, considers the coverage of cellular cells when the discovery channel is designed, prevents D2D discovery from interfering with cellular communication. The CP length of the discovery channel is determined by the coverage of the D2D discovery such that equipment discovery efficiency under a condition that UEs are not synchronized is guaranteed.

A method and system for using frequency resources in a communication system are provided. In the method and system, a total frequency band is divided into at least two frequency subbands and there is a guard interval between frequency subbands. A first frequency subband includes a TDD UL frequency subband and a TDD DL frequency subband. A second frequency subband includes an FDD UL frequency subband. A BS sets a frequency band between the TDD UL frequency subband and an FDD UL frequency subband as an additional UL frequency subband, and receives a signal from an MS in the additional UL frequency subband.

The in-band adjacent-channel digital audio broadcasting system includes a scrambling unit for scrambling a signal to be broadcasted, thereby generating a scrambled signal; an outer coding unit for performing a first encoding of the scrambled signal, thereby generating an outer encoded signal; an outer interleaving unit for performing a first interleaving of the outer encoded signal a byte by byte basis, thereby generating an outer interleaved signal; an inner coding unit for performing a second encoding the outer interleaved signal, thereby generating an inner encoded signal; an inner interleaving unit for performing a second interleaving of the inner encoded signal, thereby generating an inner interleaved signal; a modulating unit for modulating the inner interleaved signal, thereby generating an orthogonal frequency division multiplexing (OFDM) symbols; a guard interval inserting unit for inserting a guard interval between the OFDM symbols in order to eliminate an inter-symbol interference, thereby generating an OFDM frame; and an RF processing unit for performing a conversion of the OFDM frame into an analog radio frequency signal so that the OFDM signal can be transmitted in a specific frequency channel of an FM frequency band, and for amplifying and outputting the analog radio frequency signal.

A coherent optical receiver for a data-frame format in which a data frame has two or more pilot-symbol blocks, each having a cyclic prefix or suffix, and one or more payload-symbol blocks, each of which is concatenated with at least one adjacent block without a guard interval between them. The receiver uses optical signals corresponding to the pilot-symbol blocks to perform data-frame synchronization, frequency-offset correction, and channel-estimation procedures, which are robust even in the presence of certain transmission impairments. The receiver applies block-overlap processing with a sliding window to recover the payload data in a manner that substantially cancels the adverse effects of inter-block interference caused by the absence of guard intervals in the payload portion of the data frame. In one embodiment, the receiver performs channel-estimation and block-overlap processing for polarization-division-multiplexed signals in a manner that enables a combined, intertwined application of channel-response-compensation and polarization-demultiplexing procedures.

A transmitting apparatus, a receiving apparatus and methods of controlling these apparatuses are provided. The transmitting apparatus includes: an input processor configured to process a plurality of input streams to generate a plurality of base band frames; a bit interleaved and coded modulation (BICM) processor configured to perform forward error correction (FEC) coding, constellation mapping, and interleaving on the plurality of baseband frames; a symbol generator configured to add signaling data to the plurality of baseband frames output from the BICM processor to generate an orthogonal frequency division multiplexing (OFDM) symbol; and a transmitter configured to select at least one of a plurality of pilot patterns based on a fast Fourier transform (FFT) size and a guard interval fraction, insert a pilot in the OFDM symbol according to the selected pilot pattern, and transmit a stream including the pilot-inserted OFDM symbol. Thus, a data transmission rate is increased and accurate channel estimation is performed, through inserting different pilots according to different FFT sizes and guard interval fractions.

A method of transmitting digital information over a dispersive optical channel includes encoding the digital information into a series of data blocks, wherein each block comprises a plurality of substantially orthogonal frequency domain subcarriers. Each data block is then divided into at least two frequency bands, each band comprising a plurality of contiguous subcarriers. A frequency/time transformation is then performed, in order to form a corresponding plurality of transformed bands, each transformed band comprising a sequence of time domain data samples. A time delay is applied to at least one of the transformed bands relative to at least one other of the transformed bands. The bands are then combined to produce an electrical signal waveform embodying the digital information. Finally, an optical source is modulated using the electrical signal waveform, to produce a corresponding optical signal for transmission over the dispersive optical channel. The invention enables a reduction in the duration of guard intervals that may need to be inserted into the transmitted data blocks, in order to avoid received signal degradation due to inter-symbol interference caused by dispersion in the optical channel. Transmission overheads may thereby be reduced, resulting in an improvement in transmission efficiency.

A timing error compensation system in an OFMD/CDMA communication system includes an analog-to-digital converter for converting an OFDM signal, comprised of a data symbol stream in which a pilot symbol is inserted at intervals of a prescribed number of data symbols, received from a transmitter, to a digital OFDM symbol stream by prescribed sampling synchronization, a guard interval remover for removing a guard interval inserted in the OFDM symbol by prescribed frame synchronization, and a fast Fourier transform (FFT) device for performing fast Fourier transform on the guard interval-removed OFDM symbol and outputting a data symbol stream. In the time error compensation system, a pilot symbol detector receives the data symbol stream and detects the pilot symbols inserted in the data symbol stream at prescribed intervals. A timing compensator determines a linear phase difference line for the detected pilot symbol, generates a timing error estimation signal according to the determined linear phase difference line, and provides the timing error estimation signal to the analog-to-digital converter and the guard interval remover so as to determine the sampling synchronization and the frame synchronization.

The module for switching between a long guard interval and a short guard interval comprises a signal processing unit, a measurement unit, a comparison unit and a switching unit. The module receives a first data symbol, and the data symbol has one of a long guard interval and a short guard interval. The signal processing unit is configured to generate a second data symbol in accordance with the first data symbol. The measurement unit is configured to measure a portion of the first and second data symbols in order to generate a first measurement value and a second measurement value. The comparison unit is configured to generate an output signal by comparing the first and second measurement values with a threshold value. The switching unit is configured to selectively switch guard intervals of subsequent data symbols in accordance with the output signal.

An arrangement and method in a communication system such as an Orthogonal Frequency Division Multiplexing (OFDM) radio receiver for reducing the impact of interference from an intermittent interfering signal transmitted by an interfering system which may be co-located with the OFDM system or may be remotely located. Each OFDM symbol in a received OFDM signal includes a guard interval (GI), a middle portion, and a last portion identical to the GI. The arrangement determines which portion of each OFDM symbol is contemporaneous with the interfering signal and time-shifts a fast Fourier transform (FFT) window in the OFDM receiver to minimize or eliminate FFT processing of samples of the OFDM symbol that are contemporaneous with the interfering signal, thereby minimizing the impact of the interfering signal.

The present invention provides a method of and an apparatus for changing the gain of a receive path amplifier during the middle of a packet transmission, and particularly changing the gain during a guard interval between a symbol with encoding bits disposed therein and a subsequent data symbol encoded in a manner corresponding to the encoding bits.

A method and an apparatus relating to an OFDM data communications system where the sub-carriers are modulated using differential quadrature phase-shift keying (DQPSK). The multi-carrier transmitted signal is directly generated by means of summation of pre-computed sample points. As part of the multi-carrier signal generation, a signal for the guard interval is established. In an acoustic application of this approach, direct radiation of the sub-carrier approach is facilitated. Symbol synchronization in the receiver is based on signal correlation with the missed sub-carrier. Separation of the sub-carriers in the receiver by means of correlation of the received signal and reference signals that are derived from a table of pre-computed values. Optimal non-coherent processing of the sub-carriers without any phase tracking procedures is achieved.