259 results about "Ofdm transmission" patented technology

A wireless terminal and network terminal are provided for implementing a new uplink OFDM protocol. In the new protocol, the wireless terminal has a first transmit chain for generating and transmitting a low rate mode OFDM transmission in a first frequency band of the OFDM band; and a second transmit chain for generating and transmitting a burst-mode transmission in a second frequency band of the OFDM band, the first frequency band being distinct from the second frequency band. An access channel is provided which is overlaid over the low rate mode transmissions of other users.

A method and system for communication of information in OFDM format are disclosed. The method employs multi-symbol encapsulation (MSE), wherein multiple OFDM symbols are grouped together in cyclic frames having a single cyclic guard portion, for example a cyclic prefix, with multiple OFDM symbols sandwiched between each two consecutive cyclic guard portions. All OFDM symbols of one frame are equalized together at the receiver in a frequency domain using a single DFT/IDFT operation sequence. Embodiments of the MSE OFDM system are disclosed enabling high bandwidth efficiency, high tolerance to carrier frequency offset and low peak-to-average power ratio.

A computationally efficient pulse shaping method for OFDM that produces mutually orthogonal transmission pulses having fast spectral decay is provided. The pulse shaping method comprises an iterative method for designing OFDM transmission pulses that satisfy prescribed time-frequency localization conditions. The iterative method may be implemented in a computationally efficient way and can be used to adapt the transmission pulses to time-varying channel conditions in real-time, thereby maximizing the bit-error performance of an OFDM system while maintaining high data rates in wireless transmission.

A method for rate adaptation with extended MCS set for wideband eigen-beamforming transmission. A signaling method over multiple channels in a wireless telecommunication system including a transmitter and a receiver, performs the steps of obtaining an information bit stream, selecting the number of transmission streams, selecting different transmission rates for each MIMO OFDM transmission, and transmitting the information bit stream from the transmitter via said multiple channels over a plurality of transmitter antennas to the receiver according to the selected transmission rate per channel. Selecting transmission rates further includes the steps of selecting the transmission rates based on the diversity order of each stream. The method selects different transmission modes for each MIMO OFDM transmission and provides a simple, fast and efficient scheme to select the transmission rate for each eigen-mode transmission.

A method of reducing peak-to-average power ratio in an OFDM signal comprises the steps of modulating a set of subcarriers with a set of data symbol vectors to produce a first modulated signal, limiting the magnitude of the first modulated signal to produce a first limited modulated signal, demodulating the first limited modulated signal to recover distorted input symbol vectors, constraining the distorted input symbol vectors to values greater than or equal to a minimum threshold value to produce constrained data symbol vectors, constraining out-of-band spectral components to lie within a predetermined mask, and remodulating the constrained data symbol vectors. A transmitter that performs the method is also included.

In an OFDM transmission scheme, in order to compensate any frequency response variations time wise resulted from any distortion in a transmission path, out-of-synchronization with passage of time, frequency drift, and phase shift, and to improve a demodulation characteristic, a PS detector in a receiver receiving an OFDM signal detects a pilot symbol. A PS1 TPFR calculator calculates a frequency response of the transmission path for a first pilot symbol, while a PS2 TPFR calculators calculates a frequency response of the transmission path for a second pilot symbol for a second pilot symbol. Thereafter, a compensation vector calculator calculates compensation vectors from the frequency responses of the transmission path for both of the first and second pilot symbols by linear approximation. A frequency response compensatory compensates the frequency response variation of subcarriers in a data symbol based on the calculated compensation vectors.

A system and method for effectively providing an adaptive modulation scheme and known-cyclic prefix (CP) technology in an orthogonal frequency division multiplexing (OFDM) communication system. An OFDM transmission system variably generates a known CP while considering a channel state. Pilot subcarrier position information for generating the known CP is sent to a transmitter. Pilot subcarriers are selected on the basis of a channel state of an OFDM symbol through which data is transmitted and the known CP is generated, such that data transmission is provided efficiently.

An optical network includes a multidimensional coder and modulator for handling multiple-in-multiple-out MIMO spatial lightpath properties and content of any specific supercarrier, a spatial mode multiplexer responsive to orthogonal frequency division multiplexing OFDM transmissions and the multidimensional coder, a spatial-spectral routing node coupled over a fiber link to the spatial mode multiplexer for performing switching granularity by a spatial mode reconnection, a multidimensional decoder and demodulator; and a spatial mode demultiplexer coupled over a fiber link to the spatial-spectral routing node and responsive to the multidimensional decoder and demodulator.

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.

Disclosed is a method for generating and transmitting a reference signal in a clustered DFT-spread OFDM transmission scheme. A method for generating and transmitting a DM-RS in a clustered DFT-spread-OFDM scheme comprises: a step of generating DM-RS sequences corresponding to the number of clusters allocated for an uplink transmission; and a step of mapping the generated DM-RS sequences to the relevant DM-RS symbol positions for each cluster. Accordingly, the method for generating and transmitting a reference signal according to the present invention, in which DM-RS sequences are allocated and transmitted on a cluster basis, uses a complete DM-RS sequence for each cluster, and therefore inter-cell interference can be weakened, and problems which might occur when applied to a multi-user MIMO (MU-MIMO) scheme can be solved.

The time required for switch the channel can be remarkably curtailed. When broadcasting signals through a plurality of information channels with an OFDM system, the plurality of information channels are multiplexed in the sense of frequency and collectively subjected to IFFT modulation for connected transmission instead of subjecting the plurality of information channels independently to OFDM modulation for transmission. With this arrangement, the efficiency of exploitation of frequencies is improved. According to the invention, the OFDM frames are synchronized for each information channel for the purpose of connected transmission. Then, the OFDM receiver can switch the information channel for signal reception, maintaining the frame synchronizing signals.

A diversity transmitter for use in an OFDM transmission protocol which diversity transmitter comprises:

• • a diversity generator (2) for receiving and diversifying OFDM transmit symbols, and outputting diversified OFDM symbol matrices (DOSM), DOSM symbols within each DOSM being divided into at least two primary streams each comprising different DOSM symbols, a transmit processor for receiving said at least two primary streams of DOSM symbols, and for transforming said each DOSM symbol from the frequency domain into the time domain, and outputting time domain OFDM symbols (TDOSs),
  • a cyclic delay circuit (41 . . . 4P) for dividing at least one of said primary streams of TDOSs into at least two branches of identical TDOSs, each branch for supplying a respective spatial channel for transmission to a receiver,
  • the arrangement being such that, in use, said cyclic delay circuit (41 . . . 4P) applies a cyclic time shift to a TDOS symbol in at least one of said branches before transmission.

Methods for secure OFDM communications include changing the length of OFDM symbols in a pseudo-random fashion by appending a totally random signal to some of the OFDM symbols. An adaptive cyclic prefix is provided for covert and spectrally efficient communication. A developed PN based random data addition provides further security by removing the chance of combining synchronization information over several OFDM symbols.

A receiving apparatus in an OFDM transmission system includes a channel estimation unit (101) for measuring a delay profile of a delayed wave having a delay greater than a guard interval of data; a guard-interval-exceed delayed wave detector (103) for detecting, from the delay profile as an intersymbol interference (ISI) portion, a delay-time portion greater than the guard interval of the data; a ISI replica generator (104) for generating, as the ISI replica, a time-waveform portion of a known symbol conforming to the ISI portion, or a time-waveform portion of the preceding symbol; subtractor (102) for subtracting the ISI replica from a receive signal; and an FFT arithmetic unit (106) for demodulating data by applying FFT processing to the result of subtraction.

Systems and methods for power line transmission are disclosed in which transmitters and receivers are connected to one or more phases of the power line. At least one symbol stream to be transmitted on the power line network is generated. The at least one symbol stream is scaled using a weight vector to generate a plurality of scaled symbol streams. The weight vector comprises a plurality of weights, each corresponding to a phase of the power line network. Each of the scaled symbol streams are transmitted on a corresponding phase of the power line network. A zero crossing detector identifies phase information for a receiver. A concentrator adapts signals to be sent to the receiver based upon the phase associated with the receiver.

Methods and apparatus in a fifth-generation wireless communications, including an example method, in a wireless device, that includes receiving a downlink signal comprising an uplink access configuration index, using the uplink access configuration index to identify an uplink access configuration from among a predetermined plurality of uplink access configurations, and transmitting to the wirelesscommunications network according to the identified uplink access configuration. The example method further includes, in the same wireless device, receiving, in a first downlink subframe, a first Orthogonal Frequency-Division Multiplexing (OFDM) transmission formatted according to a first numerology and receiving, in a second downlink subframe, a second OFDM transmission formatted according to a second numerology, the second numerology differing from the first numerology, where the first numerology has a first subcarrier spacing and the second numerology has a second subcarrier spacing, the first subcarrier spacing differing from the second subcarrier spacing. Variants of this method, corresponding apparatuses, and corresponding network-side methods and apparatuses are also disclosed.

A system and method for crest factor reduction of OFDM transmission systems using selective sub-carrier degradation, is disclosed. A modulated communications signal comprising a series of symbols is converted into parallel format in groups of plural symbols in the frequency domain. Crest factor reduction reduces a primary peak of the groups of plural symbols by selective sub-carrier degradation, to generate peak reduction symbols. The groups of plural symbols are converted into time domain symbols, and combined with the peak reduction symbols to provide peak reduced symbols in time domain.

The invention discloses a visible light communication system and a visible light communication method thereof, which relate to the technical field of wireless optical communication. The system comprises a transmitter and a receiver. An input signal is converted into an optical signal by the transmitter, the optical signal is transmitted to the receiver by a wireless optical channel, and the receiver converts the optical signal into an electrical signal and outputs the electrical signal. The transmitter comprises a carrier interferometry orthogonal frequency division multiplexing (CI-OFDM) modulation circuit and a white light-emitting diode (LED) drive circuit which are connected, wherein the CI-OFDM modulation circuit is used for performing CI-OFDM modulation on data input by a user; and the white LED drive circuit is used for converting the electrical signal generated by the CI-OFDM modulation circuit into the optical signal. The receiver comprises a PD photoelectric detector and a CI-OFDM demodulation circuit which are connected, wherein the PD photoelectric detector is used for performing P/D conversion on the received optical signal to convert the optical signal into the electrical signal; and the CI-OFDM demodulation circuit is used for performing CI-OFDM demodulation on the received data. By the system and the method, the transmission quality of the visible light communication system can be effectively improved, and the peak-to-average power ratio of an OFDM transmitted signal can be reduced.

The device for processing OFDM transmission signal includes radio remote unit (RRU) and base band unit (BBU). BBU is in use for carrying out data mapping from media access layer to physical layer as well as scrambling baseband data, and coding, interlacing, demodulating channel, then sending them to RRU. RRU also includes post-processing module for baseband data. The post-processing module is in use for carrying out serial-parallel conversion for baseband data, interpolation, fast reverse Fourier transform, adding circulation prefix, parallel-serial conversion, and outputting. The invention raises resolution and sampling rate of signal spectrum, saves bandwidth of transmission link between BBU and RRU as well as improves quality of transmission signal.

A TFI-OFDM transmission system includes a data generator generating data having a speed corresponding to a transmission speed mode; a convolutional encoder convolutional-encoding the data, an interleaver bit-interleaving the encoded data, an OFDM modulator inputting a first data group into a positive frequency domain and a second data group into a negative frequency domain, executing an IFFT, and outputting OFDM symbols; a buffer temporarily storing the OFDM symbols in order to sequentially transmit the OFDM symbols in a time domain at least two times; and a frequency generator generating certain frequencies to transmit the OFDM symbols in a certain number of frequency bands corresponding to transmission channels.

Modulation section 201 performs modulation processing on transmission data. Mapping control section 202 controls mapping of the baseband signal onto the subcarriers so that the important information conventionally transmitted by one subcarrier is transmitted by two subcarriers and one of the two subcarriers should be the subcarrier with a carrier frequency signal of frequency 0 which was conventionally not used. IFFT section 203 performs IFFT processing on the modulated transmission data. Transmission section 204 performs transmission processing on the IFFT-processed transmission data and transmits the processed transmission data from antenna 205.

A method and apparatus for de-interleaving interleaved data in a deinterleaver memory in an Orthogonal Frequency Division Multiplexing (OFDM) based Integrated Services Digital Broadcasting Terrestrial (ISDB-T) receiver. In different embodiments, the apparatus comprises of a OFDM symbol counter along with a divider or a buffer pointer RAM with circular pointer logic, a first lookup table to obtain delay buffer size and interleaving lengths for a given OFDM transmission layer, and a second lookup table to obtain buffer base address and interleaving lengths for a given OFDM transmission layer.