Abstract: An active laser guarding system 1 comprises at least one screen 3 provided with at least two spaced apart conductors 7, 9 each defining a respective electrically conductive path that is electrically separate from the other. The screen 3 comprises material, at least between the two conductors 7, 9, which is arranged to carbonize when struck by a laser beam to form a further conductive path 19 which extends between, and electrically connects, the two conductors 7, 9. The system 1 further comprises a detector 15 operative to detect the further conductive path 19 so formed, the detector 15 being operative to generate a laser deactivation signal response to detecting the further conductive path 19.

Abstract: A surface emitting laser element includes a light emission part having a mesa structure. The light emission part includes a lower reflector; a resonator structure including an active layer; and an upper reflector. The lower reflector, the resonator structure and the upper reflector are laminated on a substrate. A peripheral part of a top surface of the mesa structure is covered by a dielectric layer that has a tapered surface such that a thickness decreases in a direction toward an outermost part, a taper angle of the tapered surface with respect to a surface of the substrate is smaller than a slope angle of a side wall of the mesa structure with respect to the surface of the substrate, and an end part of the dielectric layer coincides with an end part of the upper reflector.

Abstract: A manufacturing method for manufacturing a surface-emitting laser device includes the steps of forming a laminated body in which a lower reflecting mirror, a resonator structure including an active layer, and an upper reflecting layer having a selective oxidized layer are laminated on a substrate; etching the laminated body to form a mesa structure having the selective oxidized layer exposed at side surfaces thereof; selectively oxidizing the selective oxidized layer from the side surfaces of the mesa structure to form a constriction structure in which a current passing region is surrounded by an oxide; forming a separating groove at a position away from the mesa structure; passivating an outermost front surface of at least a part of the laminated body exposed when the separating groove is formed; and coating a passivated part with a dielectric body.

Abstract: The invention provides a quantum well active region for an optoelectronic device. The quantum well active region includes barrier layers of high bandgap material. A quantum well of low bandgap material is between the barrier layers. Three-dimensional high bandgap barriers are in the quantum well. A preferred semiconductor laser of the invention includes a quantum well active region of the invention. Cladding layers are around the quantum well active region, as well as a waveguide structure.

Abstract: A surface emitting laser is provided which can control a beam shape and can provide higher efficiency and higher power. The surface emitting laser includes a gain region that is provided between a first semiconductor multilayer film reflection mirror and a second semiconductor multilayer film reflection mirror, which are arranged so as to oppose to each other, and that has a first active layer and a second active layer. The surface emitting laser has a current constriction layer for constricting an electric current which is injected into the first active layer and the second active layer. The first active layer and the second active layer have different active layer structures from each other.

Abstract: An optical device having a structured active region configured for one or more selected wavelengths of light emissions.

Abstract: The present invention provides a photonic crystal surface emitting laser with which an arbitrary beam shape can be obtained and which enables design with a high degree of freedom. The surface emitting laser including a photonic crystal having a resonance mode in an in-plane direction parallel to a substrate includes a reflecting mirror for reflecting light emitted from the photonic crystal in a normal direction of the substrate and a spacer layer interposed between the reflecting mirror and the photonic crystal, wherein a nonuniform in-plane distribution is provided to the characteristics of one of the reflecting mirror and the spacer layer, so that a Q-value, which is a resonator characteristic in the normal direction of the substrate in the surface emitting laser, has a nonuniform in-plane distribution.

Abstract: An oscillator housing includes a main body unit that is shaped into a frame and formed of a metallic material and a cover unit that is formed of a metallic material to cover openings of the main body unit, and has an outer wall that has an arc cross section perpendicular to the optical axis and extends in the optical axis direction and side walls that are connected to the both ends of the outer wall in the optical axis direction. When the cover unit is fixed to the main body unit with a fixing member, the outer wall having an arc shape is configured such that force is generated in the height direction towards the outside of the oscillator housing on the connecting portion of the cover unit with the main body unit.

Abstract: An array of discrete catalyst elements is contained in a heated module external to the main laser vessel with an auxiliary gas flow loop connecting them so as to provide independent control of catalyst temperature and gas flow rate to achieve high CO+1/2O2 to CO2 recombination under high pulse repetition frequency operation for a sealed laser. Catalyst elements in the form of cylinders with holes through their centers are mounted on multiple parallel rods or catalysts in the form of small spherical or cylindrical elements are contained in multiple packets arranged in the module so as to minimize flow impedance and maximize laser gas recycling throughput. The cylindrical catalyst module is constructed so as to allow for rapid heating to operating temperature while withstanding atmospheric differential pressures during laser processing.

Abstract: In one general embodiment, a thin film structure includes a substrate; a first corrosion barrier layer above the substrate; a reflective layer above the first corrosion barrier layer, wherein the reflective layer comprises at least one repeating set of sub-layers, wherein one of the sub-layers of each set of sub-layers being of a corrodible material; and a second corrosion barrier layer above the reflective layer. In another general embodiment, a system includes an optical element having a thin film structure as recited above; and an image capture or spectrometer device. In a further general embodiment, a laser according to one embodiment includes a light source and the thin film structure as recited above.

Abstract: A gain module, operative to output a laser light coupled into a laser system, is structured with at least one gain element radiating the laser light and a spectrally-selective element. The spectrally-selective element includes a slab of photosensitive material and two parallel feedback and isolating Bragg mirrors recorded in the slab. The feedback Bragg mirror is operative to provide a wavelength-dependent feedback so as to cause the laser chip to generate the laser light at the resonance wavelength of the feedback Bragg mirror. The isolating Bragg mirror is automatically adjusted to retroreflect a backreflected signal light, which is generated by the laser system at a signal wavelength different from the resonance wavelength, upon positioning the feedback mirror orthogonally to the laser light.

Abstract: The invention relates to a laser light source for generating narrow-band laser radiation with high coherence, comprising a laser diode (1), which forms an internal resonator (4), and an external resonator (7) coupled to the internal resonator (4). The object of the invention is to improve a laser source of the kind such that it generates narrow-band and coherent laser radiation with high output power and at the same time with high long-term stability. Furthermore, the laser light source is to be produced in a cost-effective manner. The object is achieved by the invention in that the laser diode (1) runs in an operating mode in which multimode laser radiation is generated, comprising a plurality of spectrally neighboring resonance modes (9) of the external resonator (7). The resonance modes are selected by adapting the spectral characteristics of the external (7) and internal (4) resonators.

Abstract: The present invention relates to a switchable dual wavelength solid state laser with a solid state gain medium (1) which is selected to emit optical radiation at a first wavelength with a first polarization and of at least a second wavelength with a second polarization different from said first polarization when optically or electrically pumped. A polarizing device (7) is arranged within the laser cavity, said polarizing device (7) being adjustable at least between said first and said second polarization. The two end mirrors (2, 3) of the laser cavity are designed to allow lasing of the solid state laser at the first wavelength when the polarizing device (7) is adjusted to the first polarization, and to allow lasing of the solid state laser at the second wavelength when the polarizing device (7) is adjusted to the second polarization. The proposed solid state laser allows an easy switching between two emission wavelengths.

Abstract: An arc discharge method includes the steps of heating and melting a non-conductive object by arc discharge using a plurality of carbon electrodes in a output range of 300 to 12,000 kVA; and setting a ratio of the distance between a contact position at which the carbon electrodes come in contact with each other and a front end to the diameter of the carbon electrode during the start of the arc discharge to be in the range of 0.001 and 0.9.

Abstract: A technique for wirelessly transmitting management data without cables in a data center is provided. Management data is obtained at a device in the data center. A wireless management data signal is generated from the management data. The wireless management data signal is configured to be transmitted at frequencies matching an ambient electromagnetic noise emitted by the data center, such that the wireless management data signal is masked in the ambient electromagnetic noise emitted by the data center. The wireless management data signal is wirelessly transmitted to another device.

Abstract: A frequency hopping pattern and a method for transmitting uplink signals using the same are disclosed. A frequency hopping pattern is defined by combination of subband hopping, which is performed over one or more subbands divided from a system band for transmission of the uplink signals, and mirroring where resource blocks within one subband are arranged reversely based on the center of the subband. Sequences as to whether to apply minoring and subband hopping amount are cell-specific random numbers, and are generated independently or in combination.

Abstract: A Point-to-Point communication system includes (i) a millimeter-wave channel having a substantially flat channel transfer function between a first frequency of millimeter-waves and a second frequency of millimeter-waves, the two frequencies are separated by at least 500 MHz, (ii) a transmission system configured to transmit an Orthogonal Frequency Division Multiplexing (OFDM) signal having a bandwidth of at least 100 MHz over the millimeter-wave channel as a millimeter-wave signal located between the first frequency and the second frequency, and (iii) a reception system comprising a radio receiver having a substantially non-flat reception transfer function over the bandwidth of the OFDM signal, configured to receive the millimeter-wave signal via the millimeter-wave channel and down-convert the millimeter-wave signal into a reconstruction of the OFDM signal having a bandwidth of at least 100 MHz, and an OFDM de-modulator configured to compensate for the substantially non-flat reception transfer function, by d

Abstract: The present invention provides a signal modulation method which includes the following steps: a input signal is channel encoded, and the channel encoded signal is processed by the following one or several ways: channel scrambling, interleaving, duplicating and puncturing; the signal being processed is divided into two components I and Q, wherein the two components I and Q compose a signal pair; the signal pair is divided into more than one path, and respective path of signal is quadrature phase shift keying spectrum spreading modulated using different spectrum spreading sequence and is orthogonally modulated in order that the peak-to-average power ratio of the respective paths of signal being orthogonally modulated are obtained; and a path of signal having the smallest peak-to-average power ratio is selected to be outputted as an output signal.

Abstract: In a communication system, a method and an accompanying apparatus determine a number of available fingers (110A-N) in a receiver (100). A controller (121) adjusts a threshold based on the determined number of the available fingers (110). The adjusted threshold may be one of, or any combination of, a pilot signal search threshold, a lock/unlock threshold, and a combine/un-combine threshold. The number of available fingers (110) may change after the threshold is adjusted.

Abstract: To receive a radio navigation signal modulated by a modulation waveform, the modulation waveform comprising a component BOC(n1,m) and a component BOC(n2,m), n2 being strictly less than n1, a correlation is performed between a prompt local waveform and the modulation waveform and a correlation is performed between a shifted (forward or backward) local waveform and said modulation waveform, over a time interval of duration T. The prompt local waveform is generated in the guise of a binary waveform comprising over said time interval at least one waveform segment BOC(n2,m) of a total duration of (1??A)T over said time interval, ?A being a parameter greater than or equal to 0 and strictly less than 1. The shifted local waveform is generated in the guise of a binary waveform comprising over said time interval at least one waveform segment BOC(n1,m) of a total duration of ?BT over said time interval, B being a parameter strictly greater than 0 and less than or equal to 1, and ?A being different from ?B.

Abstract: The present invention relates to a duobinary transceiver. Specifically, the duobinary transceiver circuit proposed by the invention provides a new circuit configure of a precoder in a typical transceiver and a decoder in a typical receiver, based on a conventional transceiver including a transmitter, a transmission medium, and a receiver.

Abstract: Multiple input multiple output (MIMO) receiver circuitry is described. In one circuit, input circuitry provides a matrix of unresolved symbols received from a plurality of receive antennas. Channel estimation circuitry constructs a plurality of channel matrices including at least two channel matrices corresponding first and second subcarriers, respectively. A preprocessing circuit receives input from the plurality of channel matrices and interleaves retrieved input into an input matrix. A first systolic array includes boundary cells and internal cells. The boundary cells and internal cells are configured to perform triangulation and back-substitution on the input matrix to produce an output matrix. A second systolic array performs right and left multiplication operations and cross-diagonal transpose on the output matrix to produce a weighted matrix.

Abstract: A channel estimation method and apparatus using a self-tracking algorithm is provided for improving channel estimation accuracy. The channel estimation apparatus of a mobile terminal includes a receiver for converting a received radio signal into a baseband signal, a match filter for converting the baseband signal into a digital signal including at least two samples, a channel estimator for buffering the samples, for analyzing multipath signals to predict a maximum power position and multipath energy, and for estimating a channel by selecting a multi-tap at the maximum power position through a slew control, an equalization controller for calculating an equalization tap gain using the multi-tap selected by the channel estimator, and an equalizer for compensating for distortion in the samples output by the channel estimator using the equalization tap gain calculated by the equalization controller.

Abstract: Generally, 100BaseT allows for the establishment of links on cables (such as Category 5 or CAT5 cables) up to 120 m or more in length. In a given industrial Ethernet system, many of the cables deployed will be less than 120 m in length, and, in fact, many of the cables are much shorter than 120 m. Yet, the transmission amplitude output from each unit is generally the same, regardless of cable length. Here, Power Back Off (PBO) circuitry is provided in a unit that operates in a PBO mode to passively estimate a cable length and adjust its corresponding transmission amplitudes to generally match the estimated cable length so as to reduce power consumption.

Abstract: A synchronization section specifies a position of a guard interval correlation's center of gravity based on a guard interval correlation value, and calculates a carrier-direction shift amount Fshift. An equalization section shifts the passband of a carrier interpolation filter of a carrier interpolation section by the carrier-direction shift amount Fshift calculated by the synchronization section. This shift processing causes the delay profile to be kept in the center of the passband of the carrier interpolation filter, for any FFT window position. This enables transmission path estimation without limiting a range of an FFT window position even if the passband of the carrier interpolation filter is narrower than a guard interval of an OFDM signal.

Abstract: Methods and circuits for automatic adjustment of equalization are presented that improve the quality of equalization for input signals with varying amplitudes. The methods and circuits may be used in Decision Feedback Equalization (DFE) circuits to maintain a constant equalization boost amplitude despite variations in input signal amplitude. The equalization circuitry measures the amplitude of the equalization input signal and computes tap coefficients to maintain a desired level of boost amplitude. Tap coefficients may be automatically adjusted by the equalization circuitry.

Abstract: A receiver is optimized by adapting the taps of a decision feedback equalizer component within the receiver. Data decisions and error decisions are generated. These data decision and error decisions are used to derive an error rate of data by measuring the number of margin hits that occur. A balance value is also calculated from the data decisions and the error decisions. The balance value is used to update a tap of the decision feedback equalizer. The updating of the tap continues until the number of margin hits has been minimized.

Abstract: Methods, medium, and machines which compress, enhance, encode, transmit, decode, decompress and display digital video images. Real time compression is achieved by sub-sampling each frame of a video signal, filtering the pixel values, and encoding. Real time transmission is achieved due to high levels of effective compression. Real time decompression is achieved by decoding and decompressing the encoded data to display high quality images. A receiver can alter various setting including, but not limited to, the format for the compression, image size, frame rate, brightness and contrast. In a Doppler improvement aspect of the invention, Doppler velocity scales are incorporated into grayscale compression methods using two bits. Variable formats may be selected and Doppler encoding can be turned on and off based on the image content.

Abstract: A video transmission system includes a transceiver module that receives a device parameter from a remote device and that transmits a video signal to the remote device, wherein the video signal is transmitted as at least one separate video layer stream chosen from, an independent video layer stream and at least one dependent video layer streams that require the independent video layer for decoding. A control module chooses the at least one separate video layer stream based on the device parameter.

Abstract: A self-adapting code rate distribution method of video image macro-block level is provided. The method carries out analysis processing in units of macro blocks, a bit distribution model which combines bits number of a macro block level with the macro block energy is used, so that the bit distribution of each macro block is combined with the macro block energy, in which the macro block energy is obtained through extracting and abstracting the macro block characters. The above model can primely combine the code rate control arithmetic with the nature character of the image, then the accuracy of the code rate control can be improved, the code quality can be controlled at the same time, and the quality change in space of the image can be smoothed, the image subjective quality can be improved.

Abstract: When entropy-encoding a converted quantized amount obtained by converting an image into a frequency region and quantizing it, if the output code bit quantity of the entropy encoding exceeds a predetermined amount, an image obtained by rebuilding the converted quantized value is outputted from an image encoding device. This guarantees an encoding delay caused by re-encoding to be a constant time without increasing the circuit size of the encoding device and provides an image encoding device of a subjectively high quality.

Abstract: Various embodiments for performing motion detection for video processing are described. In one or more embodiments, motion detection may be performed by computing a temporal difference measurement, a local spatial complexity measurement, and a content dependent motion detection value based on the temporal difference measurement and the local spatial complexity measurement. In some implementations, the content dependent motion detection value may comprise a division of the temporal difference measurement by the local spatial complexity measurement. In other implementations, an approximated content dependent motion detection value may be computed without division to reduce computational complexity. The content dependent motion detection value may be used to perform various adaptive post-processing operations such as for de-interlacing, noise reduction, frame rate conversion, and so forth. Other embodiments are described and claimed.

Abstract: A video signal coding system for network transmission includes a video output apparatus and a signal conversion apparatus. The video output apparatus includes a decoding unit decoding an video signal encoded by a coding method using a motion vector and a superimposing unit superimposing reference control information containing at least a motion vector on a blanking period of the video signal, and outputs the video signal with the reference control information superimposed. The signal conversion apparatus includes a separating unit separating the reference control information from the blanking period, an encoding unit encoding the video signal by the coding method using the motion vector, and a motion vector converting unit converting the motion vector in the reference control information into a motion vector corresponding to the coding method in the encoding unit, and the encoding is performed using the converted motion vector.

Abstract: In one embodiment, the method includes selecting a list 0 motion vector of the co-located block in a first reference picture as the motion vector if the co-located block has the list 0 motion vector and a list 1 motion vector. The first reference picture is a type of reference picture permitted to be located temporally before or after the current picture. The method further includes selecting the list 1 motion vector of the co-located block in the first reference picture if the co-located block only has the list 1 motion vector, scaling the selected motion vector based on temporal distance between the current picture and the first reference picture, and deriving at least one motion vector of the bi-predictive block based on the scaled motion vector.

Abstract: In one embodiment, the method includes selecting a list 0 motion vector of the co-located block in a first reference picture as the motion vector if the co-located block has the list 0 motion vector and a list 1 motion vector. The first reference picture is a type of reference picture permitted to be located temporally before or after the current picture. The method further includes selecting the list 1 motion vector of the co-located block in the first reference picture if the co-located block only has the list 1 motion vector, and deriving at least one motion vector of the bi-predictive block by applying a bit operation to the selected motion vector.

Abstract: A coding mode selection method for selecting a coding mode for motion vector estimation is disclosed. The method includes the following steps. First, a first coding mode is selected to perform motion vector estimation for a macroblock having M sub-blocks. M motion vectors corresponding to the M sub-blocks are separately calculated. It is determined whether correlations for the M motion vectors match to a predetermined condition. If not, the first coding mode is selected and the M motion vectors are utilized to perform a motion vector estimation; and if so, a second coding mode is selected and the N motion vectors corresponding to the second coding mode are utilized to perform the motion vector estimation, wherein the N motion vectors are generated by using the M motion vectors and 1?N<M.

Abstract: A circuit for computing sums of absolute difference (SAD) is provided. The circuit has an absolute difference circuit, a first adder, a first register and a first selective circuit. The absolute difference circuit receives a first data PMi,j and a second data PSi,j and output a absolute difference data ADi,j, wherein ADi,j=|PMi,j?PSi,j|. The first adder receives and adds the absolute difference data and a first accumulative data, and outputs a first sum. The register receives and locks the first sum according to a first preset timing sequence, and outputs a first sum of absolute difference data. The first selective circuit receives and selects the first sum of absolute difference data or 0, and outputs the selected data as the first accumulative data.

Abstract: A video processing system. In a specific embodiment, the system implements a system for processing macroblocks that includes a first module for processing a macroblock. A controller provides a first macroblock to the first module and provides a second macroblock to the first module, without waiting for the first module to complete processing of the first macroblock, when information is available to the first module to process the second macroblock. The first module may implement a pipelined processor that is adapted to process macroblocks simultaneously. Alternatively, the first module includes a first engine and a second engine, which may run in parallel as parallel engines. In a more specific embodiment, an entire image frame is treated as a single slice and processed by the system via a pipelined engines or parallel engines.

Abstract: Systems and methods that provide a video stream, the video stream comprising a sequence of plural compressed pictures corresponding to a video program, the plural compressed pictures having plural sets of compressed pictures, each of the plural sets adhering to one or more picture interdependencies, properties, or a combination of the picture interdependencies and properties, and provide auxiliary information in the video stream, the auxiliary information comprising plural data fields, the plural data fields comprising a first data field corresponding to one of multiple possible coding scheme, the coding scheme comprising a set of tiers that uniquely define the one coding scheme, the plural data fields further comprising a second data field different from the first data field, the second data field comprising an indication of whether the one or more picture interdependencies, properties, or a combination of both corresponding to the set of tiers is valid for use in decoding.

Abstract: In one embodiment, a method comprises providing a video stream, and providing information identifying compressed pictures in the video stream corresponding to respective picture interdependency tiers.

Abstract: A deblocking filter, an image encoder, and an image decoder perform edge-filtering of moving-image data which can be divided into blocks, on groups of a predetermined number of pixels arrayed across edges between the blocks, and include: a processing unit concurrently performing column-direction-edge filtering on more than one first group of pixels which are arrayed in rows across ones of the edges oriented in a column direction, the ones of the edges belonging to a macroblock to be currently processed; and an rearrangement unit rearranging pixels being included in the more than one first group of pixels and the macroblock and having been processed by the processing unit, into more than one second group of pixels in respective columns.

Abstract: In accordance with an embodiment of the present invention, a method comprising: representing coefficients of an adaptive image filter in binary words wherein the coefficients are restricted and the binary words have a maximum number of bits defined at least in part by a precision index; computing at least one of a convolution sum and multiple partial convolution sums of the adaptive image filter wherein the at least one of a convolution sum and multiple partial convolution sums having a constrained value range and having a binary representation with a fixed maximum number of bits; and generating the output of the adaptive image filter based at least in part on the at least one of a convolution sum and multiple partial convolution sums, is disclosed.

Abstract: A method for feeding back transmitter beamforming information from a receiving wireless communication device to a transmitting wireless communication device includes a receiving wireless communication device receiving a preamble sequence from the transmitting wireless device. The receiving wireless device estimates a channel response based upon the preamble sequence and then determines an estimated transmitter beamforming unitary matrix based upon the channel response and a receiver beamforming unitary matrix. The receiving wireless device then decomposes the estimated transmitter beamforming unitary matrix to produce the transmitter beamforming information and then wirelessly sends the transmitter beamforming information to the transmitting wireless device. The receiving wireless device may transform the estimated transmitter beamforming unitary matrix using a QR decomposition operation such as a Givens Rotation operation to produce the transformer beamforming information.

Abstract: A multipath component in a GPS signal received is detected when an asymmetry exists in the correlation function of the received signal and the expected GPS signal. The multi-path component is also detected, even without a line-of-sight component in the received GPS signal, when a peak of the correlation function jumps a significant distance (i.e., a sudden, significant change in a detected code phase).

Abstract: A method and modem are provided for obtaining an optimized efficiency of an Orthogonal Frequency Division Multiplex (OFDM) data transmission, such as for power line communication, for example. The length or duration of a guard interval or cyclic prefix in an OFDM symbol is newly selected at each start-up of a modem while initializing or preparing the OFDM data transmission. The length of the guard interval can be given by the number of samples in a time-discrete representation, and the value of such number of samples that is retained for the subsequent data transmission can be selected from a plurality of pre-determined possibilities based on an evaluation of a channel quality of a communication channel including a physical line to which the modem is connected. Hence, the selected value depends on actual transmission conditions, and the optimization potential offered by a more flexible handling of system parameters is exploited to meet changing conditions on the physical line.

Abstract: The present invention provides a wireless transmission method and system based on maximum multi-path delay estimation.

Abstract: This disclosure is directed to systems and methods that compensate for a phase change that results from a change in RF gain, a “phase glitch,” that would otherwise degrade the performance of a multiple sub-carrier communication system, such as OFDM. Pilot symbols are used to estimate the phase change, allowing the pilot and data symbols to be compensated by the estimated phase change. Preferably, the compensated pilots are used to per form a second iteration of phase change estimation that determines residual phase glitch. Thus, following the second estimation of phase change, data symbols can be compensated for the estimated residual phase change.

Abstract: An apparatus and a method for interference cancellation using a multi-user multiple input multiple output (MU-MIMO) scheme in a single carrier frequency division multiple access (SC-FDMA) system are disclosed. Received data of every terminal are classified into first received data and second received data. The first received data has lower reliability and the second received data has higher reliability than the first received data. The second received data is transmitted to an upper layer. Interference signals are formed with the second received data based on a channel estimation value. The interference signals are removed from the first received data, and the interference signal free first received data is transmitted to the upper layer.

Abstract: A mobile device in an OFDM system receives an OFDM signal comprising RS tones and data OFDM symbols. The received RS tones are extracted for channel estimation using a masking operation. Masking parameters are determined by matching channel time variance using corresponding time domain samples of the extracted RS tones. As approximated channel impulse responses of transmission channels, the time samples are masked to perform the channel estimation. The channel time variance comprising inter-carrier interference and delay spread are measured, respectively. A mean of differences in power between neighbor adjacent subcarriers of the extracted RS tones is used for the inter-carrier interference measurement. The delay spread measurement such as root-mean-squared (RMS) delay spread is calculated using the approximated channel impulse responses.

Abstract: In a peak-to-average power ratio (PAPR) reduction method for an orthogonal frequency division multiplexing (OFDM) system based on path finding, the method applied to the OFDM system uses an ant colony optimization (ACO) algorithm and a PTS to reduce a PAPR value, and an area of a computing circuit. In a simulated result, the method can reduce the PAPR effectively, and can be executed by a lower level of complexity of the computation. To solve a large matrix of the PTS, an ant colony optimization algorithm is used for calculating phase rotation vectors of a better quality effectively to achieve the effects of improving the performance, overcoming the high level of complexity of the computing circuit, and reducing the large area of the computing circuit.