928 results about "Frequency division multiplexed" patented technology

Signal construction, detection and estimation techniques for use in uplink timing synchronization and access control in an orthogonal frequency division multiplexed (OFDM) wireless system or other type of wireless communication system. In accordance with an illustrative embodiment of the invention, timing and access signals to be transmitted in designated timing and access intervals are constructed from orthogonal multitone signals. The multitone signals may be similar to multitone signals used in OFDM data transmission, except that a cyclic prefix associated with reception of the signals in a base station is extended to cover the timing errors of mobile stations not yet synchronized. The invention also provides design techniques which optimize the time resolvability and peak-to-average ratio of the multitone signals, an efficient fast Fourier transform (FFT) based technique for maximum likelihood timing estimation, and a robust linear filtering technique for averaging timing estimates from different synchronizations.

An interleaver and interleaving method each includes two stages, and is useful in coded orthogonal frequency division multiplexed (COFDM) wireless local area networks. A first stage performs a first block permutation and a second stage performs bit order permutation to effectuate a second group permutation. A corresponding de-interleaver does just the opposite at the receiver. A double-buffer version includes writing data into one memory block in a first order while reading data from the second block in a second order, with the first and second orders selected to effectuate the first block permutation.

A data processing apparatus maps input symbols to be communicated onto a predetermined number of carrier signals of an Orthogonal Frequency Division Multiplexed (OFDM) symbol. The data processor includes an interleaver memory which reads-in the predetermined number of data symbols for mapping onto the OFDM carrier signals. The interleaver memory reads-out the data symbols on to the OFDM carriers to effect the mapping, the read-out being in a different order than the read-in, the order being determined from a set of addresses, with the effect that the data symbols are interleaved on to the carrier signals. The set of addresses are generated from an address generator which comprises a linear feedback shift register and a permutation circuit. In order to provide a 4 k mode for an OFDM modulated system such as a Digital Video Broadcasting (DVB) standard such as DVB-Terrestrial (DVB-T) or DVB-Handheld (DVB-H) standards, a generator polynomial for the linear feedback shift register of Ri'[10]=Ri-1'[0]⊕Ri-1'[2] is provided with a permutation order which has been established by simulation analysis to optimise communication performance via typical radio channels.

The present invention centers upon uplink communication protocols for use primarily with orthogonal frequency division multiple access (OFDMA) communication systems. Aspects of the invention relate to narrow band frequency division multiplexed (NBFDM) modulation protocols primarily for uplink usage in asymmetric OFDMA communication systems. In particular, NBFDM uplinks that use quadrature multiplexed continuous phase modulation are detailed and noncoherent detection schemes are developed to process the uplink channel signals without the need to transmit uplink phase reference signals. Other aspects of the invention relate to burst mode uplink communications in OFDMA systems such as those involving opportunistic beamforming.

The present invention relates to allocating a radio resource in a wireless communication system utilizing orthogonal frequency division multiplexing (OFDM). Preferably, the present invention comprises receiving in a mobile station data associated with a radio resource allocation map from a base station, wherein the radio allocation map comprises control parameters for transmitting an uplink channel, wherein the uplink channel comprises at least on OFDM tile comprising a first set of subcarriers associated with representing at least part of an n-bit data payload, and a second set of subcarriers associated with representing at least part of a non-pilot m-bit data payload wherein each subcarrier carries a modulated data, and the first and the second set of subcarriers are exclusive to each other, and transmitting the uplink channel from the mobile station to the base station.

A power line communication device for communicating data signals over a power line is provided. One example embodiment comprises a conditioning circuit configured to be coupled to the power line and a modem communicatively coupled to the conditioning circuitry to transmit and receive data signals over the power line via the conditioning circuitry. The modem may be configured to transmit and receive orthogonal frequency division multiplexed data signals that comprise a plurality of sub-carriers, wherein the modem is adapted to vary the transmit power for each of a plurality of subsets of the plurality of sub-carriers from substantially zero power to a plurality of increments above zero power. The modem also may be adapted to transmit and receive data signals with the transmit power for each of a plurality of subsets of the plurality of sub-carriers being different and to transmit and receive using a different modulation scheme at different sub-carriers.

Methods and apparatus for use in reducing residual phase error (RPE) in orthogonal frequency division multiplexed (OFDM) communication signals are described. One method includes the steps of calculating a phase of each one of a plurality of channel-compensated data symbols to generate a plurality of data symbol phases; performing a hard-decision on each one of the plurality of channel-compensated data symbols to estimate a plurality of information symbols; calculating a phase of each one of the plurality of information symbols to generate a plurality of information symbol phases; calculating a phase difference between each data symbol phase and its associated information symbol phase to generate a plurality of phase differences; and determining a residual phase error based on the plurality of phase differences.

A method and apparatus of transmitting a reference signal in a wireless communication system is provided. Demodulation Reference Signals (DMRSs) for a plurality of respective antennas is generated. The DMRSs are mapped to a resource region, and transmitted through the respective corresponding antennas. The DMRSs are multiplexed using at least one of frequency division multiplexing (FDM), code division multiplexing (CDM), and time division multiplexing (TDM) methods and mapped in the resource region. Also, a position of an orthogonal frequency division multiplexing (OFDM) symbol to which the DMRSs are mapped in the resource region is an OFDM symbol to which a physical downlink control channel (PDCCH) and a legacy cell-specific reference signal (CRS) are not mapped.

A highly bandwidth-efficient communications method is disclosed that enables remote stations to synchronize in time and frequency to their serving base station. The invention enables a base station and its remote stations in a cell to synchronize in a noisy environment where signals interfere from other base stations and remote stations in other cells. The base station forms a forward synchronization burst that includes a plurality of tone frequencies arranged in a distinctive orthogonal frequency division multiplexed pattern unique to the base station. The unique pattern enables a remote station to distinguish the base station's bursts from other signals present in a crowded area. The distinctive orthogonal frequency division multiplexed pattern can be a Hadamard code pattern, for example. When the a base station has received a signal on a reverse link from a remote station, having significant interference, the base station selectively forms a request signal requesting the remote station to respond with a reverse synchronization burst that includes a plurality of tone frequencies arranged in the same distinctive orthogonal frequency division multiplexed pattern. The base station then transmits the forward synchronization burst and the request signal at a base station reference instant of time to the remote station. The reverse synchronization signals selectively occupy time slots in the transmission frame from the remote station to the base station, that would otherwise be occupied by channel control or traffic signals. Only when the base station requests the remote station to respond with a reverse synchronization burst, does this burst preempt the time slot from its other uses.

A radio system employing Orthogonal Frequency Division Multiplexed (OFDM) includes a Base Transceiver Station (BTS) along with a number of mobile terminals located within a coverage area of the BTS. In this system, a target mobile terminal is provided with a focused transmission beam to receive high data rate traffic information while the remainder of the mobile terminals are provide with pilot and signalling information. To achieve both objectives, a BTS is implemented with a transmission apparatus that generates a directional transmission beam for the data traffic information. In one design, this directional beam transmits the pilot and signalling information along with the data traffic information by rotating the beam within the coverage area. In another design, the BTS has a transmission apparatus that generates more than one transmission beam. In one case, the BTS transmits a directional transmission beam for the data traffic information required by the target mobile terminal and a second broad transmission beam for the pilot and signalling information required by the all of the mobile terminals. In another case, the BTS transmits two directional transmissions beams, one beam for data traffic information and one rotating beam for pilot and signalling information.

An architecture for providing high-speed access over frequency-division multiplexed (FDM) channels allows transmission of ethernet frames and/or other data across a cable transmission network or other form of FDM transport. The architecture involves downstream and upstream FDM multiplexing techniques to allow contemporaneous, parallel communications across a plurality of frequency channels. Moreover, an automatic frequency control resolves some issues of a free-running clock in an upstream tuner of the central concentrator by performing adjustments based on the average frequency error of a number of active upstream tones. In the preferred embodiments of the present invention, the automatic frequency control (AFC) utilizes a feedback loop for at least each active upstream tone. Also, the average of the active upstream tones is determined and is utilized in providing feedback to adjust the automatic frequency control (AFC).

The present invention discloses a transmitter and receiver for optical communications system, which provide compensation of the optical link nonlinearity. M-PSK modulating is used for data embedding in an optical signal in each WDM channel using orthogonal frequency division multiplexing (OFDM) technique. At the receiver side electrical output signals from a coherent optical receiver are processed digitally with the link nonlinearity compensation. It is followed by the signal conversion into frequency domain and information recovery from each subcarrier of the OFDM signal. At the transmitter side an OFDM encoder provides a correction of I and Q components of a M-PSK modulator driving signal to compensate the link nonlinearity prior to sending the optical signal to the receiver.

An Orthogonal Frequency Division Multiplexing communication system, wherein a frequency bandwidth is divided into one or more Resource Blocks Groups (RBGs) each having one or more Resource Blocks, provides for feedback of channel quality information and precoding metrics for a same at least one RBG of the one or more RBGs. More particularly, a user equipment measures one or more channel quality parameters associated with at least one RBG of the one or more RBGs, determines channel quality information and a precoding metric for an RBG of the at least one RBG, and reports the channel quality information and a precoding metric determined for the RBG to a radio access network. In one embodiment of the invention, the RBG whose channel quality information and precoding metric are reported may be selected from the at least one RBG based on the measured channel quality parameters.

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.

A method of transmitting data symbols via an Orthogonal Frequency Division Multiplexed (OFDM) symbols, includes forming data symbols into pairs, generating a first pair of modulation symbols for each of the pairs of data symbols, the first pair of modulation symbols forming first and second modulation symbols of an Alamouti cell, forming a first version of the OFDM symbols by modulating the sub-carriers allocated for carrying the data with the first and second modulation symbols of the Alamouti cells, and modulating the one or more pilot carriers of the first version of the OFDM symbol according to a predetermined pattern. The method also comprises generating a second pair of modulation symbols for each of the pairs of data symbols, the second pair of modulation symbols forming third and fourth modulation symbols of the Alamouti cell formed for the pair of data symbols in the first version of the OFDM symbol, forming a second version of the OFDM symbol by modulating the sub-carriers allocated for carrying the data with the third and fourth modulation symbols of the Alamouti cell, modulating the one or more pilot carriers of the second version of the OFDM symbols according to the predetermined pattern, and transmitting the first version of the OFDM symbol via a first antenna, and the second version of the OFDM symbol via a second antenna. For at least one of the pairs of data symbols, the sub-carriers, on which each of the first and second modulation symbols and the third and fourth modulation symbols forming the Alamouti cells, are separated within the first and second versions of the OFDM symbol by at least one other data bearing sub-carrier or one or more of the pilot carriers.

A transmitter and/or receiver according to the invention find application with the Digitial Video Broadcast-Terestrial 2 (DVB-T2) standard.

Method and process for receiving, demodulating, equalizing and processing of Modulation Demodulation Format Selectable (MFS) received signal, received from two or more than two antennas and from diversity receivers. Baseband processing filtering and adaptively equalizing demodulated signals and providing filtered equalized burst operated Time Division Multiplexed (TDM) cross-correlated in-phase and quadrature phase signal, spread spectrum Code Division Multiple Access (CDMA) signal and Orthogonal Frequency Division Multiplexed (OFDM) signals. Demodulation of peak limited cross-correlated OFDM signals. Demodulation and adaptive equalization of receive filtered signal, wherein the received filtered signal is mis-matched to transmit filtered signal. Process for receiving and demodulating MFS signals received from modulated linearly amplified and transmit filtered modulated non-linearly amplified (NLA) signal transmitters. Demodulation and processing of cross-correlated TDM, spread, spectrum and OFDM signals.

Methods and apparatus are disclosed for DC offset estimation and for DC offset compensation that collectively reduce or eliminate the distortion of subcarriers due to DC offset in an OFDM receiver. The DC offset estimation is obtained by subtracting a sum of time domain samples of an OFDM symbol for two consecutive OFDM symbols or subtracting a known transmitted OFDM symbol and a frequency domain representation of a received version of the known OFDM symbol (at least one of which is adjusted to compensate for channel distortion). The DC offset compensation is accomplished by removing the estimated DC offset from the received signal. The DC estimation process and the DC compensation process can be connected in disclosed feed-forward or feedback configurations.

The invention discloses a receiving method and device of an MIMO (multiple-input multiple-output) communication system compatible to multiple frame formats and belongs to the technical field of wireless communication. In a millimeter-wave wireless communication system, stations working in the same basic service set are likely to receive three different types of PPDUs (physical layer protocol data units), namely a single-carrier MIMO PPDU, an OFDM (orthogonal frequency division multiplexing) MIMO PPDU and an OFDM MU-MIMO (multi-user multiple-input multiple-output) PPDU. Preambles of the three frame formats are identical to signaling fields A in format and sent in a single-carrier mode. The receiving method includes that a receiver demodulates the signaling fields A with the single-carrier mode, a receiving process is configured on the basis of the signaling fields A and signaling fields B, and the various PPDUs are demodulated. Compared with the prior art, the receiving method and device have the advantage that reliability and compatibility of the system are improved effectively.

Various types of passive optical networks operate simultaneously in one passive optical network system comprising an optical line terminal, a passive remote node, and multiple optical network units. Downstream data is orthogonal frequency division multiplexed onto a single wavelength optical carrier transmitted on a primary downstream optical beam from the optical line terminal to a splitter in the passive remote node. The primary downstream optical beam is split into multiple secondary downstream optical beams; each is transmitted to a specific optical network unit. Upstream data is orthogonal frequency division multiplexed onto a single wavelength optical carrier transmitted on a secondary upstream optical beam from each optical network unit to a coupler in the passive remote node. The upstream wavelength for each optical network unit is different. The wavelength division multiplexed optical beam is transmitted from the passive remote node to a parallel signal detector in the optical line terminal.