69results about How to "Accurate channel estimation" patented technology

A method of transmitting and receiving preamble sequences in a transmitter in an OFDM communication system is provided. A transmitter segments a first sequence of a predetermined length into a predetermined number of second sequences, generates as many preamble sequences as the second sequences by applying different time offsets to the second sequences, selects a predetermined number of preamble sequences among the generated preamble sequences, maps the selected preamble sequences to the transmit antennas, and transmits the mapped preamble sequences through the transmit antennas.

A method of transmitting pilot signals for channel compensation in a mobile communication system based on DFT-spread-OFDM is disclosed. In the disclosed method, a first pilot signal and a second pilot signal are time-division multiplexed together with a data signal of a user into a time-division multiplexed signal which data signal is assigned a certain bandwidth; the time-division multiplexed signal is frequency-division multiplexed together with time-division multiplexed signals of other users when wirelessly transmitted; and the first pilot signal is assigned a bandwidth larger than the bandwidth of the data signal and the second pilot signal is assigned a bandwidth smaller than the bandwidth of the data signal.

An apparatus and method for channel estimation using preamble signals received from a serving Node B and neighboring Node Bs each having N (≧1) transmit antennas in a UE having M (≧1) receive antennas in a broadband wireless communication system. In the channel estimation apparatus, a Node B number decider calculates the maximum number N_S of channel-estimatable Node Bs using a preamble length, the number of antennas in each of the Node Bs, and the number of multiple paths. A multi-cell preamble matrix generator generates a multi-cell preamble matrix x_S by generating a Node B preamble matrix for each of the Node Bs and selecting N_S Node B preamble matrices according to reception power among the Node B preamble matrices. A channel estimator performs a channel estimation using x_S and signals received through the M antennas during a preamble receiving period.

The present invention relates to a method and arrangement to enhance the communication performance in wireless communication systems. The method of the invention provides a method of calibrating at least one first radio node in a wireless communication network. The communication network comprises at least a first radio node and a second radio node, which can be arranged to be in radio communication with each other. The calibration method is based on that at least one representation of radio channel characteristics, which has been exchanged from one radio node to the other. Whereby inaccuracies and differences in transmit receive chains are compensated and channel reciprocity can be used.

This invention discloses a guiding project based on time and frequency's synchronized training sequence. It uses the good period correlated characteristic and constant amplitude of CAZAC sequence to serve the CAZAC sequence as the known measuring sequence, and cramps out a part of sequence from CAZAC sequence to serve as guiding signal. Amplifies properly the guiding signal's power, and inserts the digital signal into the relevant place of the guiding signal and sets to zero. The measuring sequence can either be used to synchronize the time and frequency, also can be used to the channel estimation. The invention can make more precise channel estimation, higher data demodulation performance to make the system tracing the fading of the channel more precisely and duly.

In an OFDM transmitter included in a first service area, an orthogonal-code-pattern multiplication unit multiplies pilot channel signals belonging to any subcarrier group by an orthogonal code which is different from that for one or a plurality of OFDM transmitters adjacent to the OFDM transmitter included in the first service area, or a subcarrier assignment unit assigns pilot channel signals to pilot subcarriers which are common to a plurality of OFDM transmitters and based on a pilot arrangement notified in advance by a control station to all OFDM transmitters included in the first service area.

A CDMA receiver and a CDMA transceiver are provided which have high resistance to fading fluctuations, and carry out highly accurate channel estimation, considering the rate of channel fluctuations. When carrying out the channel estimation by calculating weighted sums of the (average values of) pilot symbols interposed into a data symbol sequence, the weighting control is performed considering the rate of the channel fluctuations. For example, the weighting control is carried out using, as its update values, inner products of the channel estimation values and the (average values of) pilot symbols. This makes it possible to achieve the highly accurate channel estimation.

The invention relates to a method of estimating the transmission channel of a received multi-carrier signal (y) in a mobile environment, which method comprises identifying pilots (P₁, P₂, . . . , P_k) present on carriers of the received multi-carrier signal (y), which pilots (P₁, P₂, . . . , P_k) comprise continual pilots (P₁, P₂, . . . , P_k), performing channel estimation on the received multi-carrier signal (y) using a time-domain interpolator (3, 3′) to give a first interpolator output (30), and performing channel estimation on the received multi-carrier signal (y) using a frequency-domain interpolator (4, 4′) to give a second interpolator output (40). A frequency offset in a continual pilot (P₁, P₂, . . . , P_k) is detected, and either the first interpolator output (30) or the second interpolator output (40) is selected on the basis of the detected frequency offset. The invention also relates to a system (1) for estimating the transmission channel of a received multi-carrier signal (y) in a mobile environment, which system comprises an identification unit (2) for identifying pilots (P₁, P₂, . . . , P_k) present on carriers of the received multi-carrier signal (y) which pilots (P₁, P₂, . . . , P_k) comprise continual pilots (P₁, P₂, . . . , P_k), a time-domain interpolator (3, 3′) for performing channel estimation on the received multi-carrier signal (y) to give a first interpolator output (30), a frequency-domain interpolator (4, 4′) for performing channel estimation on the received multi-carrier signal (y) to give a second interpolator output (40), an offset detection unit (5) for detecting a frequency offset in a continual pilot (P₁, P₂, . . . , P_k), and a selection unit (6) selecting either the first interpolator output (30) or the second interpolator output (40) on the basis of the detected frequency offset.

The invention relates to the communication technology field, disclosing a retransmission method, a retransmission apparatus and a communication system. The retransmission method comprise the following steps: receiving a retransmission indication after sending code words of two channel coding in first transmission, wherein the retransmission indication comprises the identification of the code wordof a channel coding which needs to be retransmitted; according to the preset phase positions of each symbol, determining precoding matrix of each symbol of code word of the channel coding which needsto be retransmitted, wherein the phase relationship of each symbol is fixed; and using the precoding matrix to encode each symbol of code word of the channel coding which needs to be retransmitted, and sending the coding through antenna. According to the invention, the success of retransmission for UE is guaranteed.

FBMC (Filter Bank Multicarrier) is a special carrier communication mode. Being different from OFDM (Orthogonal frequency division multiplexing), subcarriers of the FBMC are not orthogonal to one another, so that intersymbol interference and inter-carrier interference naturally exist. A traditional OFDM channel estimation method is built on the basis of no intersymbol interference and inter-carrier interference, thereof, to carry out accurate channel estimation, the interference of surrounding symbols to a pilot symbol must be eliminated, and surrounding interference factors are definite under a certain filter bank structure and a prototype filter design. An auxiliary pilot method is such a method that an auxiliary pilot is placed nearby the position of an actual pilot, the value of the auxiliary pilot is determined by virtue of the values of the surrounding symbols and the corresponding interference factors, and the interference of the surrounding symbols to the pilot position is eliminated by virtue of the auxiliary pilot, so as to carry out accurate channel estimation.

The invention discloses a channel estimation channel, which belongs to the technical field of digital information transmission. The method comprises the following steps: removing intersymbol interference and noise from linear convolution of data of the previous frame and channel impulse response to obtain novel linear convolution; calculating the pseudo random sequence of the current frame and the linear convolution for initial channel estimation; reconstructing the linear convolution of the current frame; respectively transforming the pseudo random sequence of the current frame and the reconstructed linear convolution; carrying out reverse transformation of the ratio after transformation to obtain novel channel estimation; and accumulating the iteration times, and using the novel channel estimation as the initial channel estimation for further iteration if the iteration times does not reach the preset maximal value, or else, setting the novel channel estimation as the final channel estimation. The channel estimation method can acquire more accurate channel estimation, eliminate intersymbol interference caused by multi-path channels and reduce the processing complexity for channel estimation and balance a of multi-carrier or single carrier transmission system based on pseudo random sequence filling.

A method of performing channel estimation of a physical downlink control channel (PDCCH) in a wireless communication system is disclosed. Specifically, the method performed by a user equipment (UE) includes receiving a synchronization signal block (SSB) from a base station, receiving system information (SI) from the base station based on the SSB, transmitting a physical random access channel (PRACH) preamble to the base station, receiving a response to the PRACH preamble from the base station, transmitting UE capability information related to the channel estimation to the base station, receiving information for a PDCCH monitoring duration from the base station, and performing the channel estimation based on the information for the PDCCH monitoring duration. The UE capability information includes information for a maximum number of control channel elements (CCEs) that are capable of the channel estimation per PDCCH monitoring duration.

When carrying out a channel compensation of a data symbol, a channel estimation value of the reference symbol of the frame itself and that of a reference symbol of the preceding frame are used. In this event, if an AGC gain at the time of a channel estimation value by a reference symbol of the frame itself is different from that of a frame of the reference symbol of the preceding frame, and if an AGC gain of the reference symbol of the frame itself is the same as that of a data symbol to be subjected to a transmission compensation, then the channel estimation value by the reference symbol of the preceding frame is corrected so as to cancel the difference of the AGC gains, followed by using it for a channel compensation of the data symbol.

Systems and methods which introduce a variable shift with respect to pilot symbols in providing a data subcarrier channel estimation are shown. Use of pilot symbol shifts may be useful, for example, when path delay is long and/or when non-consecutive, non-uniformly distributed pilot subcarriers are used. The foregoing shift may be introduced in the time or frequency domains according to embodiments of the invention. For example, a shift of a particular number of samples may be introduced with respect to the symbols of the pilot subcarriers in the measured pilot subcarrier channel response for use in data subcarrier channel estimation.

The method includes that: estimates the channel impact response of the mid training queue of the sub-frame normal slot; against the data section in the normal slot, according to the distance between the mentioned data section and the mentioned mid training queue, calculating via interpolation the channel impulse response of the mentioned data section. The invention avoids that treats directly the channel impulse response of the mid training queue is treated directly as the channel impulse response of the data section. This ensures a more accurate channel estimation of the data section and solves the technical problem that the channel estimation under hi-speed condition is difficult to realize via the existed technique. Therefore, the effective cover of the net against the hi-speed railway is realized.

The invention relates to a channel estimation method and a channel estimation system, applied to a large-scale MIMO system comprising base stations and a plurality of cells. The method comprises the following steps: different pilot signals are distributed to central users and edge users; the target base station estimates a channel between the target base station and the target cell according to received data; the target base station recovers the data sent by the central users of the target cell and caching the recovered data according to the estimated channel and signals received within a continuous time; the target base station eliminates the data sent by the central users of the target base station from the received data according to the cached data and the pilot signals of the central users; the target base station estimates the channels between the target base station and the edge users of the target cell, and channels between the target base station and peripheral interference cells, so that channel estimation is more accurate, and the pilot pollution problem is effectively solved.

A method for transmitting scattered pilot signals in a multi-carrier system is disclosed. The method includes: in each time slot, in time dimension, putting each 4 OFDM symbols into a group according to the order of the OFDM symbols; in each group of OFDM symbols, in frequency dimension, selecting, for each OFDM symbol, a plurality of valid sub-carriers to transmit scattered pilots, wherein for a same OFDM symbol, between each 2 valid sub-carriers selected, there are 7 valid sub-carriers; for different OFDM symbols in a same group, the valid sub-carriers selected are interleaving in frequency domain; and transmitting scattered pilot signals on the valid sub-carriers selected. The solution helps the multi-carrier system to handle multi-path channel with large delay spread, to obtain more accurate channel estimation and to achieve better receiving performance.

The invention relates to an anti-multipath iterative weighted LMMSE channel estimation method and device. The method comprises the following steps: S110, performing time domain filtering on channel time domain impulse response output through IFFT to obtain time domain channels hP and LS; S120, computing power delay distribution according to the time domain channels hP and LS; S130, performing phase rotation, segmentation and FFT cascading on the power delay distribution to form a frequency domain; S140, forming a frequency domain autocorrelation matrix and a cross-correlation matrix according to the frequency domain, and computing a channel estimation coefficient; and S150, computing the channel estimation according to the channel estimation coefficient. The anti-multipath iterative weighted LMMSE channel estimation method and device disclosed by the invention solve an interference problem on the mobile communication signal quality by a multipath problem in the city.