117 results about "Composite channel" patented technology

A system and method are described for dynamically adapting the communication characteristics of a multiple antenna system (MAS) with multi-user (MU) transmissions (“MU-MAS”). For example, a method according to one embodiment of the invention comprises: transmitting a training signal from each antenna of a base station to each of a plurality of wireless client devices, each of the client devices analyzing each training signal to generate channel characterization data, and receiving the channel characterization data at the base station; computing a plurality of MU-MAS precoder weights based on the channel characterization data, the combined MU-MAS precoder weights comprising a MU-MAS channel matrix; determining instantaneous or statistical channel quality (“link quality metric”) for the wireless client devices using mutual information of MU-MAS links or singular values of the MU-MAS composite channel matrix; determining a subset of users and a MU-MAS transmission mode based on the link quality metric; precoding data using the MU-MAS precoder weights to generate precoded data signals for each antenna of the base station; and transmitting the precoded data signals through each antenna of the base station to each respective client device within the selected subset.

A method an apparatus is described for providing feedback for closed-loop transmitting with multiple transmit and receive antennas. The method includes a first step 900 of providing a codebook containing sets of weightings for each data stream of the multiple transmit antennas with each set identified by an index known to a transmitter and a receiver. The same codebook is utilized for any number of data streams up to the number of transmit antennas. A next step 902 includes measuring a composite channel between the transmitter and receiver. A next step 904 includes determining at least one performance metric for each set of weightings in the codebook. A next step 906 includes selecting preferred weightings for each data stream in response to the performance metrics. A next step 908 includes feeding back an index of the preferred weightings to the transmitter for use in subsequent transmissions.

Two additional structures for addition to the Digital Video Broadcasters (DVB) Service Information (SI) for implementation of the MPEG-2 Systems Standard (ISO/IEC 13818-1) are provided: the Logical Channel Table (LCT) and the Composite Channel Table (CCT). The LCT provides the mapping between a Logical Channel Number (LCN) representing a service and the transport stream(TSID)/program number (PN) on which the service can be found. LCT entries may designate either simple conventional channels or Composite Channels. The LCT contains a Composite Channel Indicator (CCI), which when set to "1', indicates that the selected channel is a composite channel. In this case, the LCT entry gives the home channel of the Composite Channel, which provides the CCT to the decoder so that the tuner can be retuned to the actual program designated in the CCT for current viewing. Each entry in the CCT associates a Composite Channel Number (CCN) with a LCN and represents the "present" definition for the composite channel. A simple LCN is used as a key to the LCT to determine the transport stream ID and program number (PN) for the service components in the usual way. As time progresses, the entry for a specific CCN will change; therefore, the CCN is used as a "pointer" to the LCN which is the currently active service for the composite channel. These tables work with conventional MPEG-2 service definitions to decode multi-service transport streams.

Closed loop multiple-antenna wireless communications system with antenna weights determined by maximizing a composite channel signal-to-interference-plus-noise ratio minimum. Multiplexed symbol streams over subsets of antennas enhance throughput.

The method and system for multi-user channel estimation in a multi-access network comprises: providing a communication signal (r_i) providing an estimated communication signal Formula (I) generated using a spreading code signal (C_i), an information sequence signal (B_i) and a predicted composite channel impulse response signal Formula (II); comparing the communication signal (r_i) to the estimated communication signal Formula (I) to provide an error signal (ε_i); and generating an estimated composite channel impulse response signal Formula (III) using the error signal (ε_i), the spreading code signal (C_i) and the information sequence signal (B_i); the predicted composite channel impulse response signal Formula (II) providing the multi-user channel estimation. The proposed method, which is based on a LMS like algorithm, is an efficient and low complexity method allowing estimating and tracking even fast times varying multi-path channels. Instantaneously, the composite channel impulse response is computed and estimates of all possible path energies are computed to be used as an indicator of the significant paths (delays).

A method and apparatus for curing composite materials that emit large volumes of volatiles during processing. The apparatus includes tooling having a rigid forming surface contoured to the shape of the formed composite part. A plurality of passages extend from the forming surface through the tooling. The passages are in fluid contact with an exhaust port. A composite workpiece is laid up and placed adjacent the forming surface. The apparatus includes a heater that heats the composite workpiece to temperatures at which volatiles are emitted. An evacuation system draws the volatiles away from the composite workpiece through the passages in the tooling and out of the exhaust port. One embodiment of tooling according to the invention is used to form a sine wave spar. The tooling includes upper and lower tool inserts upon which U-shaped composite channels are formed. The upper and lower tools are placed adjacent to each other to form the web of the spar. Cap strips are placed on either side of the joined U-shaped channels. Side rail tools are then placed adjacent the cap strips. A breather cloth is placed over the tools and the entire assembly is placed within a vacuum bag. The assembly is then placed within an autoclave and connected to the vacuum exhaust of the autoclave. During processing, volatiles are drawn away from the composite workpiece through the passages in the tooling using the vacuum exhaust.

The invention relates to a high-dielectric-constant gate dielectric composite channel field effect transistor device and belongs to the technical field of micro-electronics new materials and devices. The device comprises a substrate, a high-dielectric-constant gate dielectric, a graphical graphene conducting channel and a graphical molybdenum sulfide (MoS2) conducting channel which are sequentially stacked, and comprises a metal source electrode and a metal drain electrode which are arranged on the composite conducting channel. According to a preparing method, the mode of the atomic layer deposition technology (ALD) is directly utilized, and a high-dielectric-constant (high-k) material grows on the Si substrate. As the graphene/ molybdenum sulfide (MoS2) composite channels are adopted, the larger migration rate and the larger switch ratio can be obtained, and the electric property of the device is improved.

The invention relates to a non-orthogonal multiple access method based on large-scale MIMO. The method comprises the following steps of step 1, determining an optimal demodulation sequence; step 2, determining received power of a user; step 3, determining optimal emission power of the user; step 4, determining a data frame structure, wherein different users accessing the same base station follow the same uplink frame structure for synchronous transmission, and the time slot length used by the user does not exceed the coherence time of a wireless channel; step 5, adopting a pilot selection way,wherein a way of obtaining a pilot frequency by the user is that each user randomly selects the pilot frequency used by the user from a given pilot frequency set independently; and step 6, making a plurality of user terminals send signals to the base station at the optimal transmitting power based on the step 4 and the step 5, and after the base station receives the signals, only estimating a multi-user composite channel at an antenna end by means of the channel hardening capability of the large-scale MIMO, and utilizing a serial interference elimination technology to finally complete the recovery of all user signals.

A signal is received in the presence of noise and interference by demodulating the signal when a relationship between the signal and the noise and the interference meets a criterion, and by jointly demodulating the signal when the relationship between the signal and the noise and the interference does not meet the criterion. Moreover, the signal may be demodulated if a relationship between the noise and the interference meets a second criterion and may be jointly demodulated if the relationship between the noise and the interference does not meet the second criterion. More specifically, demodulation may be performed when the signal-to-noise-and-interference ratio exceeds a first threshold and joint demodulation may be performed when the signal-to-noise-and-interference ratio is less than the first threshold. Moreover, the signal may be jointly demodulated if the interference-to-noise ratio exceeds a second threshold, and the signal may be demodulated if the interference-to-noise ratio is less than the second threshold. Thus, if the desired signal power is high relative to noise and interference, joint demodulation may be skipped and demodulation may be performed. Moreover, if the desired signal power is not large compared to interference-and-noise, joint demodulation may be used only when the interference power is high relative to the noise power. Finally, an interfering signal's synchronization word may be found in the received signal, and the power of the interfering signal relative to the noise power may be determined from the located interfering signal synchronization word, to thereby determine the interference-to-noise ratio. Moreover, the interfering signal's synchronization word that is detected can provide improved estimation of the interfering signal's channel estimate, which can be estimated in terms of the interfering signal's medium response compared to the composite channel response.

An OFDM-based relay-assisted channel estimation method enables a composite channel (source-relay-destination) to be disintegrated into a source-to-relay channel and a relay-to-destination channel and separately estimated at the destination node in a relay-assisted way. A relay-amble signal is added to a sub-frame when the relay node is forwarding the amplified signals from the source node. Through the relay-amble signal, the second channel estimation from the relay node to the destination node is performed to obtain a second channel coefficient, and then uses an ML (Maximum Likelihood Estimator) algorithm to estimate a first channel coefficient from the source node to the relay node. After having estimated the coefficients of the two channels, the optimum diversity combining is performed at the destination node to improve accuracy of received data.

The invention discloses a composite channel MHEMT (Metamorphic High Electron Mobility Transistor) microwave oscillator and a preparation method thereof. The device is of a composite channel structure; mesa isolation of combined ion injection and wet corrosion is adopted; a source-drain metallic system of Ni/AuGe/Ni/Au forms ohmic contact; a T-shaped gate is manufactured by using a three-layer resist technology of two self-alignment processes of an electronic exposure beam and one development process; two different kinds of corrosion solution are used for corroding to form a gate groove; a vaporized Pt/Ti/Pt/Au metallic system forms schottky contact in the gate groove; buried Pt is formed through annealing treatment; a silicon nitride passivation layer is formed; thus the preparation of the device is finished. The oscillator and the method have the advantages of simple process, high reliability of the device and convenience in repetition. Superior direct current performance and alternating current performance are obtained by using the prepared device with gate length of 80 nanometers, the maximum output saturation current reaches 920 mA/mm, and the extrinsic transconductance reaches 1,100 mS/mm. The characteristic frequency of the device reaches 246GHz, and the maximum oscillation frequency is 301GHz.

The invention provides an OFDM receiver baseband processing method based on a low-precision ADC and an OFDM receiver baseband processing system based on the low-precision ADC, wherein a received signal is converted into an analog baseband signal through down conversion and then divided into two paths, one path is subjected to quantification with high sampling rate and low precision (1-2 bits), frame synchronous search is realized through an autocorrelation method by designing a proper reference sequence according to an obtained low-precision sample value sequence, and a high-efficiency iterative algorithm is designed for realizing accurate estimation for composite channel gain corresponding to each subcarrier, thus, constellational symbol data transmitted on each subcarrier can be recovered; and the other path is subjected to quantification with low sampling rate and high precision, and noise power estimation and automatic gain control are realized through long-time time averaging. A receiving method and a receiver processing system provided by the invention can guarantee realization of high-reliability OFDM data transmission under the condition of using the ADC with ultralow precision of 1-2 bits.

The invention relates to a method and system for simultaneous transmission of data from two or more wireless communication device during a transmission opportunity otherwise reserved for a single communication device. The invention proposes collaboration among the group of communication devices to reserve a transmission opportunity on a composite channel comprising of a plurality of sub-channels for the entire group and to efficiently manage allocation of the sub-channels for simultaneous data transmission from two or more devices. In the main aspect of the invention, the collaboration takes the form of grouping the sub-channels in the reserved composite channel so as to allow two or more stations to transmit data simultaneously over a contiguous frequency band. The collaboration among the group of communication devices may be in a managed or an ad hoc mode. The invention is particularly relevant to the IEEE 802.11 ac communication standard.

The invention discloses an MPPM-FSO system hard demodulation error symbol rate calculating method based on an EW composite channel model. The method comprises the steps that 1) based on EW distribution, a point-to-point free space optical communication composite channel model is established by taking into account the influence of a point error; 2) the values of the optimal decision threshold and adynamic decision threshold are determined according to the cumulative distribution model and probability distribution model of an EW turbulence and point error composite channel model; 3) the probability of wrong decision for each time slot subject to the interference of an EW turbulence and point error complex channel is calculated; and 4) the Gaussian Laguerre polynomials are used to acquire the closed expression of the error symbol rate. According to the invention, compared with a single atmospheric turbulence model, the composite channel model in the method takes into account the influence of the point error on the system performance; and the method has low complexity, is better than other hard demodulation algorithms in the aspect of the error symbol rate system performance, and ismore in line with the actual situation.

The invention discloses a production method of metallurgical composite channel steel. The main difference between the production method of the metallurgical composite channel steel and the traditional channel steel and the production method thereof is that a metallurgical composite pipe produced by utilizing a centrifugal casting process is used as a blank for producing the channel steel. The production method comprises the production steps of (1) producing a metallurgical composite pipe blank by using the centrifugal casting process; (2) symmetrically cutting the metallurgical composite pipe blank into two arc boards along an axial direction; (3) heating the arc boards to a plasticity temperature section of a composite steel tube base material, rolling and flattening by using a plate mill to form a composite flat steel board, and rolling the composite flat steel board according to a thickness requirement; (4) heating the rolled composite flat steel board, and producing a channel steel board meeting the requirements through hot-rolling; and (5) cutting a steel board strip in the middle of the channel steel board to prepare the metallurgical composite channel steel. A two-layered alloy in the channel steel produced by the invention has a metallurgical fusing layer; layering is different to realize; the service life is long; precious metal is saved for the channel steel made of single-alloy stainless steel material; and the economical benefits can be improved.

The invention relates to an orthogonal signal-division multiplexing (OSDM) underwater acoustic communication method based on time domain oversampling. Frequency domain diversity gain obtained throughOSDM intra-vector precoding is combined with frequency diversity gain obtained by time domain oversampling. Compared with a conventional symbol rate OSDM system, the system has the advantage that intra-vector frequency diversity gain is higher. Under the condition, each OSDM symbol vector is equivalently transmitted through a plurality of virtual channels. At a receiving end, equalization processing and multivariant receiving of each vector are realized through adoption of similar structures. According to a numerical simulation result, it is clear that compared with a conventional OSDM system,the time domain oversampling OSDM system provided by the invention has the advantage that the performance is clearly improved. Through composite channel matrix decomposition, an equalization algorithm employed by the invention has computing complexity approximate to linearity, and the time domain oversampling OSDM system provided has practical value.

The invention discloses a Double GG composite channel base multi-hop-FSO bit error rate calculation method considering influence of different beam effects. The method comprises the following steps: 1)based on Double GG turbulence distribution, considering the influence of a point error and path loss, establishing a transmission model suitable for a multi-hop-FSO system; and on the basis, deducinga system probability density function and a cumulative distribution function under the joint action of the Double GG turbulence, the path loss and the point error; 2) obtaining a closed system bit error rate expression by using the Gaussian Laguerre polynomial, and performing simulation verification through a Monte Carlo method; and 3) considering the influence of different beams, substituting ahop count, normalized jitter, a normalized beam width and a weather condition parameter into a end-to-end closed average bit error rate expression of the multi-hop-FSO system to obtain the influence of the parameter on the performance of the multi-hop FSO system.

A satellite communications system provides an information channel between remotely located transmitters and receivers. A virtual satellite system provides the same service, but divides the signal either in power or in data content into subchannels such that any particular signal is conducted to the intended receiver via a plurality of traditional satellite channels. The receiving terminal accepts the plurality of signals simultaneously from a possible plurality of satellites, combining the subchannels comprising the virtual channel into the original signal content as if conducted via a single channel. The receiving antenna system receives satellite subchannel signals from a plurality of directions using multiple antennas or a single antenna with multi-direction capability. Prior to signal combining, the receiver necessarily time-synchronizes the plurality of subchannels by introducing time delay in some channels before combining the subsignals into the original composite. A timing signal present in the virtual satellite system assists the receiver in determining the amount of delay to apply to each incoming signal. The timing signal is either a separate carrier or an additional modulation on the existing information-bearing carrier.

The invention relates to a method for producing propylene by catalytic cracking of C4 olefin. The method mainly solves the problem that the existing catalyst has poor stability and low propylene selectivity. The method comprises forming ZSM-5 molecular sieve raw powder with a shape index of 3-100 from raffinate C4, carrying out alkali treatment to obtain a molecular sieve catalyst having a composite channel structure, and carrying out a reaction process under conditions of a reaction temperature of 400 to 600 DEG C, reaction pressure of 0 to 0.3MPa and a weight airspeed of 1 to 50h<-1>. The method well solves the problem and can be used for industrial production of propylene by catalytic cracking of C4 olefin.