36 results about "Ofdm transceiver" patented technology

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.

An OFDM transceiver has a transmitter, a receiver, and a loopback switch. The loopback switch configured is for selectively establishing a physical connection between an output terminal of the transmitter and an input terminal of the receiver. The transmitter is configured for outputting to the output terminal an OFDM signal generated based on a local oscillator signal. The receiver is configured for demodulating the OFDM signal, received via the physical connection, using the local oscillator signal and determining amplitude and phase imbalance parameters based on performing frequency-domain estimation of amplitude and phase imbalances. Hence, the receiver is configured for performing imbalance compensation on a received wireless OFDM signal based on the determined amplitude and phase imbalance parameters. Hence, amplitude and phase imbalances can be estimated accurately despite channel fading and frequency variations encountered between the transmitter of the wireless OFDM signal and the receiver.

An object relative status determination system (54) for a vehicle (52) includes an orthogonal frequency domain modulation (OFDM) transceiver (56) that generates an object range signal (83). The system (54) may also include a global navigation system (GNS) (58) that receives a satellite range signal (70). A controller (66) is coupled to the OFDM transceiver (56) and the GNS (58) and determines object information relative to the vehicle (52) in response to the object range signal (83) and the satellite range signal (70).

Disclosed is a pilot multiplexing method in an Orthogonal Frequency Division Multiplexing (OFDM) system. Transmit data is transmitted by an OFDM signal through an OFDM scheme, pilot data is directly spread, and a spread-spectrum signal, which has been obtained by spreading, is transmitted in the same frequency band as that of the OFDM signal at the same time in superposition therewith or time-division multiplexed therewith. The spread-spectrum signal is a CDMA signal that has been obtained by spreading the pilot data by a prescribed spreading code.

An object relative status determination system (54) for a vehicle (52) includes an orthogonal frequency domain modulation (OFDM) transceiver (56) that generates an object range signal (83). The system (54) may also include a global navigation system (GNS) (58) that receives a satellite range signal (70). A controller (66) is coupled to the OFDM transceiver (56) and the GNS (58) and determines object information relative to the vehicle (52) in response to the object range signal (83) and the satellite range signal (70).

In an OFDM transmitter apparatus for transmitting transmit signals, which are output from first and second OFDM transmit circuits, utilizing two mutually orthogonal polarized waves, a single carrier wave generator is provided in common for the OFDM transmit circuits, and a frequency converter in each OFDM transmit circuit multiplies a baseband signal by a common carrier wave, which is output from the carrier wave generator, to convert the baseband signal to a radio signal.

A method and apparatus for efficiently providing a large volume of channel feedback, e.g., for OFDM MISO and MIMO systems, is described herein. To that end, a mapping unit in an OFDM transceiver maps channel feedback values, e.g., received reference signal values or channel estimates derived therefrom, on a one-to-one basis to individual transmission subchannels. More particularly, the mapping unit maps a feedback value, e.g., the received reference value or a channel estimate derived therefrom, to a single transmission subchannel of an outgoing OFDM signal. For example, the mapping unit may map the feedback value to an input of a frequency transform unit, such as an inverse discrete Fourier transform unit, to map the feedback value to a single transmission subchannel comprising an OFDM transmission subcarrier. The OFDM transceiver transmits the outgoing OFDM signal to the remote transceiver to provide the feedback value to the remote transceiver.

Preamble generator for a multiband frequency division multplexing (OFDM) tranceiver of a wireless personal area network (WPAN) being switchable between a time frequency interleaving (TFI)-mode wherein data packets are transmitted by said transceiver in different frequency bands according to a predetermined frequency hopping pattern and a fixed frequency interleaving (FFI) mode wherein data packets are transmitted by the transceiver in at least one fixed frequency band, wherein said preamble generator scrambles in the fixed frequency interleaving (FFI) mode a predetermined preamble of the data packets by multiplying said preamble with a pseudo random data sequence to flatten a power spectrum of said preamble.

A DMT / OFDM transceiver wherein communication occurs between stations in the form of symbols distributed and transmitted in channels which are allocated when making a link between the stations, each channel supporting a number of bits depending on the spectral response of the link when established. Instead of providing separate modules for performing iFFT's and FFT's, the transceiver has only a single FFT, or iFFT which operates on real and imaginary parts of the data stream; the outputs of the FFT or iFFT being supplied to a post processing stage where simultaneous equations having real and imaginary terms for the transmit and receive data, are solved in order to separate the transmit and receive data.

A channel estimation method for an OFDM transceiver. The OFDM transceiver is configured to derive channel state information (CSI) for a communication channel by processing the preamble of a received OFDM packet. The received packet could be, for example, an unsolicited data packet or a solicited service packet such as an acknowledgement packet. The derived CSI information can then applied to the generation of weighted OFDM packets for transmission over the communication channel. As a result, an improved effective communication channel may be established between this OFDM transceiver and another OFDM transceiver. A channel estimation method of the present invention may be implemented in an access point (AP) or a client terminal (CLT) of a WLAN system. In either case, the improved communication channel can be used, for example, to extend the range corresponding to a selected transmission bit rate and / or to increase the transmission bit rate between the AP and a CLT. In addition or alternatively, the improved communication channel can be used to reduce emitted RF power and, therefore, to reduce electrical power consumption.

A configurable Orthogonal Frequency Division Multiplexing (OFDM) device comprises a first transform stage configured to generate a first stage output having a first length, a second transform stage configured to operate in conjunction with the first transform stage and to generate a second stage output having a second length, and a switching network configured to selectively connect the second transform stage with the first transform stage to select the first stage output or the second stage output. A method of configuring an Orthogonal Frequency Division Multiplexing (OFDM) device comprises determining an appropriate OFDM mode, based on the OFDM mode determined, selectively connecting a first transform stage of the device with a second transform stage of the device, wherein the first transform stage has a first stage output and the second transform stage has a second stage output, and selecting the first stage output or the second stage output.

The invention relates to communications protocols for very high-speed data transmission, in particular burst mode packet data communications for ultra wideband (UWB) communications systems. We describe a method of sending a burst of data packets from a first OFDM transceiver to a second OFDM transceiver, said transceivers having a set of OFDM synchronisation symbols for synchronising communications between the transceivers, the method comprising: sending said data packets from said first to said second transceiver, and between sending at least some of said data packets of said bursts receiving acknowledgement data from said second transceiver at said first transceiver; and wherein said acknowledgement data is encoded using said OFDM synchronisation symbols.

Disclosed is a pilot multiplexing method in an Orthogonal Frequency Division Multiplexing (OFDM) system. Transmit data is transmitted by an OFDM signal through an OFDM scheme, pilot data is directly spread, and a spread-spectrum signal, which has been obtained by spreading, is transmitted in the same frequency band as that of the OFDM signal at the same time in superposition therewith or time-division multiplexed therewith. The spread-spectrum signal is a CDMA signal that has been obtained by spreading the pilot data by a prescribed spreading code.

For use in an orthogonal frequency division multiplexing (OFDM) transceiver, a multimode local oscillator circuit and a method of operating the same. In one embodiment, the circuit includes: (1) a single sideband mixer having an output, first and second inputs and a local oscillator input and (2) a signal generator, coupled to the single sideband mixer, for alternatively providing to the first and second inputs: (2a) constant values to cause the single sideband mixer to generate a first receiver local oscillator signal for operating the OFDM transceiver as a zero intermediate frequency receiver and (2b) a first orthogonal baseband signal to cause the single sideband mixer to generate a second receiver local oscillator signal for operating the OFDM transceiver as a low intermediate frequency receiver.

The invention relates to the field of optical transmission systems. In particular, the invention relates to a system and a method for adjusting an optical OFDM transmission system in a power optimized manner. An optical OFDM transmitter (310) operating at an overall bit-rate is provided. It comprises an adjustable mapping unit (314) associated with one of N OFDM subcarriers, operable to map M bits of a digital input signal (360) into a constellation point, thereby yielding a subcarrier signal of the corresponding OFDM subcarrier. Furthermore, it comprises an adjustable transformation unit (315, 316), operable to transform the subcarrier signal to yield an electrical output signal. In addition, the OFDM transmitter comprises an electrical-to-optical converter (324, 325), operable to convert the electrical output signal into an optical output signal. Finally, the OFDM transmitter comprises a control unit (311, 312), operable to select the number of OFDM subcarriers N and the number of bits M, such that the electrical power consumption of the OFDM transmitter (310) is minimized for the overall bit-rate and operable to adjust the adjustable mapping unit (314) and the adjustable transformation unit (315, 316) according to the selected numbers M and N.

In an OFDM transmitter apparatus for transmitting transmit signals, which are output from first and second OFDM transmit circuits, utilizing two mutually orthogonal polarized waves, a single carrier wave generator is provided in common for the OFDM transmit circuits, and a frequency converter in each OFDM transmit circuit multiplies a baseband signal by a common carrier wave, which is output from the carrier wave generator, to convert the baseband signal to a radio signal.

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.

The invention relates to a lead code pre-emphasis system of an OFDM (Orthogonal Frequency Division Multiplexing) transceiver. The lead code pre-emphasis system comprises a physical environment testing module, an emphasis network, a kasami code generation module, a frequency domain conversion module, an emphasis processing module, a time domain conversion module, an OFDM transmitter and an OFDM receiver; the physical environment testing module is used for testing a communication channel and outputting an attenuation curve characteristic vector of the communication channel to the emphasis network; the emphasis network is used for carrying out inversion on the vector to obtain a weighted value and outputting the weighted value to the emphasis processing module; the kasami code generation module is used for generating a kasami code, switching the kasami code to the frequency domain and outputting the kasami code switched to the frequency domain to the emphasis processing module; and the emphasis processing module is used for carrying out weighting processing on the kasami code which is switched into the frequency domain according to the weighted value, switching the weighted kasami code into the time domain and outputting the kasami code switched to the time domain to the OFDM transmitter and directly outputting the standard kasami code to the OFDM receiver. The lead code pre-emphasis system disclosed by the invention has stronger practicability and capability of accurately extracting the line attenuation situation in allusion to an instruction response type serial bus physical transmission channel; Due to adoption of the OFDM receiver and the OFDM transmitter, only is an RAM (Random Access Memory) storage value of the lead code changed without extra working module.

An RF receiver includes a plurality of OFDM modules. The OFDM modules include receiver antennas for substantially simultaneously receiving a plurality of transmission signals transmitted via a single frequency band having a plurality of sub-channels. Further included is a channel estimation module connected to the plurality of OFDM modules, and a channel compensation module connected to the channel estimation module and the plurality of OFDM modules. For each sub-channel, the channel estimation module is capable of estimating channel frequency responses affecting the transmission signals, and the channel compensation module is capable of compensating the transmission signals according to the estimated channel frequency responses. The receiver allows an improved transfer rate per frequency band.

An orthogonal frequency division multiplexing OFDM transceiver system that is applicable to high speed mobile environment belongs to the technical field of digital communication and is characterized in that at the sending end, the data is segmented and goes through fast reverse fourier transform respectively, and OFDM sub-symbols after transformation are directly cascaded and are attached with a zero protective suffix, thus a relatively big sub-carrier interval is acquired and intercarrier interference caused by Doppler-spread is lessened, but the sensitivity of the system to inter sub-symbol interference. At the receiving end, an interference cancellation receiving device and method that uses sub-carrier given information is designed and the inter sub-symbol interference caused by multipath delay spread is eliminated. The invention causes little or no loss in spectral efficiency of OFDM system, and under the same channel condition, the system of the invention can improve the moving speed supported by traditional methods by about 1.6 times.

A method and system for providing broadband access to a data network via gas pipes is disclosed. Embodiments of the present invention utilize Orthogonal Frequency-Division Multiplexing (OFDM) or Frequency-Division Multiplexing (FDM) as a modulation technique in order to protect against the effects of dispersion in the gas pipes. An OFDM transceiver modulates a digital data stream into an OFDM signal, RF up-converts the OFDM signal, and transmits the RF up-converted OFDM modulated signal through a gas pipe.

A signal processing unit and a method for using the signal processing unit. The signal processing unit comprising at least two Digital Signal Processors (DSPs) and at least one memory for storing data. The DSP is adapted for signal processing and is capable of accessing the at least one memory. According to an embodiment, the signal processing unit is an Orthogonal Frequency-Division Multiplexing (OFDM) transceiver. The OFDM transceiver is adapted to receive and transmit signals.

The invention discloses a user-defined OFDM (Orthogonal Frequency Division Multiplexing) transceiver, which comprises a zero intermediate frequency transmitting and receiving channel and a digital signal processing module, wherein the zero intermediate frequency transmitting and receiving channel is used for carrying out up conversion on a base band I / Q (Input / Output) signal generated by the digital signal processing module and outputting after power amplification during emission, as well as receiving an OFDM signal and outputting the base band I / Q signal to the digital signal processing module after completing down conversion during reception; the digital signal processing module is used for carrying out carrier tracking, OFDM demodulation and data decoding according the base band I / Q signal collected by an A / D (Analog to Digital)converter and outputting data in a needed format to an upper computer during reception, as well as completing data coding and user-defined OFDM format generation according to data issued by the upper computer during emission. The user-defined OFDM transceiver has the advantages of high sensitivity, far transmission distance and strong timeliness and is suitable for wireless data transmission under the environment with high sensitivity with the transmission rate of 2 Mbps and complex terrain; the user-defined OFDM transceiver provides communication for equipment, such as an unmanned aerial vehicle, and provides a foundation for expanding the market of the unmanned aerial vehicle.

An Orthogonal Frequency Division Multiplexing (OFDM) communication system and method to schedule transfers of first and second user communications between the FDM communication system and a Wireless Communication Device (WCD) are provided. The OFDM communication system in one example includes an OFDM scheduling system to process Quality-of-Service Class Identifiers (QCIs) and determine if the first user communication having a first QCI can be scheduled subsequently and if the second user communication having a second QCI can be scheduled in place of the first user communication, and if the first user communication can be scheduled subsequently and the second user communication should be scheduled in place of the first user communication, then schedule the second user communication in place of the first user communication. An OFDM transceiver wirelessly transfers the second user communication in place of the first user communication between the OFDM communication system and the WCD based on scheduling.

An OFDM communication transceiver, which is configured to test its connection with an antenna circuit unit, has a receiver chain and an emitting chain. The receiver chain includes a time-to-frequency transform unit and the emitting chain includes a frequency-to-time transform unit. The transceiver further includes means for disconnecting the receiver chain to the antenna circuit unit, means for providing a stimulus as input to the emitting chain, means for reintroducing the signal at the output of the emitting chain as an input of the receiving chain, means for determining a circuit resonance frequency, Fr, and a quality factor, Q, of a transfer function computed from the output of the time-to-frequency transform unit, and means for deciding about the connection of said antenna circuit unit according to the resonance frequency and the quality factor.

The multipath effect of the seawater channel is one of the key issues affecting the communication performance of the inductively coupled chain used in the ocean, so the present invention proposes a communication method for the inductively coupled link used in the ocean to resist the multipath effect of seawater; according to the mathematical model of the inductively coupled chain seawater channel The calculated number of paths, the delay of each path and the parameters of amplitude attenuation realize the multipath channel hardware simulator; study OFDM technology and propose an FPGA algorithm scheme that can resist multipath effects, and realize the OFDM transceiver system; The path simulator and OFDM transceiver system constitute the test platform for the marine inductive coupling chain communication system. The transmission performance test of the platform is completed, the relationship between the CP length and the maximum delay of the channel is analyzed, and the optimal CP length and the signal-to-noise condition under this CP length are determined. Comparing the influence of the bit error rate of the transmitted data; the invention provides a laboratory test platform for studying the multipath delay effect of the inductive coupling chain, and provides a new method for improving the transmission performance of the channel.

Preamble generator for a multiband frequency division multplexing (OFDM) tranceiver of a wireless personal area network (WPAN) being switchable between a time frequency interleaving (TFI)-mode wherein data packets are transmitted by said transceiver in different frequency bands according to a predetermined frequency hopping pattern and a fixed frequency interleaving (FFI) mode wherein data packets are transmitted by the transceiver in at least one fixed frequency band, wherein said preamble generator scrambles in the fixed frequency interleaving (FFI) mode a predetermined preamble of the datapackets by multiplying said preamble with a pseudo random data sequence to flatten a power spectrum of said preamble.