108results about How to "Improve BER performance" patented technology

The invention discloses a multi-user sub-carrier index modulation orthogonal frequency-division multiplexing (SIM-OFDM) transmission method. At a sending end, logic blocking of sub-carriers is carried out by adoption of an orthogonal amplitude modulation order M at first; then, information bits of all users are also grouped correspondingly; each group is divided into two parts again; one part selects one sub-carrier in each block to enable the sub-carrier to be silent; the other part modulates the residual activated sub-carriers in each sub-block; due to inverse fast Fourier transform, parallel-serial conversion and addition of a cyclic prefix, an SIM-OFDM symbol is formed and sent; at a receiving end, logic grouping, which is the same as that at the sending end, of a detection signal output by a GAMP detector is carried out by adoption of a multi-user iterative detection method based on a generalized approximate message transferring algorithm under non-ideal channel state information; a symbol having the minimum power in each group is judged, so that the positions of silent sub-carriers are identified; index bits are recovered; and residual symbols are demodulated, so that digital modulation bits are obtained. By means of the multi-user sub-carrier index modulation orthogonal frequency-division multiplexing (SIM-OFDM) transmission method disclosed by the invention, the energy efficiency and the BER performance are improved.

The invention discloses a joint detection decoding method for an MIMO system through combination of a polarization code. The method comprises the steps of 1), initializing a path list and a PED list of the path list; 2), establishing a reduction tree T; 3), carrying out path expansion layer by layer, and updating the path list and the PED list; and 5), carrying out hard input or soft input decoding after path expansion of all layers is finished. According to the method, through combination of the coding characteristic of the polarization code, ineffective path expansion and update can be avoided, the integrated calculation complexity is reduced, and moreover, the BER performance of the system is improved.

The invention provides a self-adapting modulating and encoding method and device based on channel second-order statistics in OFDM (orthogonal frequency division multiplex) system, and its characteristic: by character signal-to-noise ratio (SNR) variance, dynamically selecting suitable adapting time window; and using a two-grade moment criterion, i.e. according to SNR average value and variance, selecting suitable modulating and coding style (MCS) to accurately convert SNR to MCS, thus enhancing the applicability of self-adapting modulation and coding and reducing the possibility of system interruption, and therefore, bringing about better error bit rate property.

The invention provides a multiuser detection method based on a serial strategy for an SCMA (Sparse Code Multiple Access) uplink communication system, and belongs to the field of signal detection of wireless communication systems. The method is characterized in that nodes in a conventional SCMA factor graph are divided into J groups (J is a quantity of user nodes); each group comprises one user node and all resource nodes connected with the user node; and all nodes (one user node and all the resource nodes which are connected with the user node) of each group are updated in sequence in each iteration process. According to the multiuser detection method, already-updated node messages are utilized in each iteration process, so that a utilization ratio of the already-updated node messages can be effectively increased. The BER (Bit Error Rate) performance of the method is far superior to the BER performance of a method in the prior art under the condition of less iteration times. The calculation complexity of the method is much lower than the calculation complexity of the method in the prior art under the condition of hardly any loss of the BER performance.

The invention relates to an SC-IFDMA (single carrier-interleaved frequency division multiple access) communication method based on SIM (subscriber identity module) modulation and belongs to the technical field of anti-jamming. The thoughts of SIMOFDM (SIM orthogonal frequency division multiplexing) is used for reference to introduce SIM modulation to SC-IFDMA. Different time slot bearing data is selected at the transmitting end of an SC-IFDMA link according to SIM modulation index bits, and the SIM modulation signals are detected at the receiving end with a special detecting method. The SIM modulation introduces new power distribution strategies to increase BER (bit error rate) performance of a system. If further interweaving is performed after SIM modulation to reduce the probability that the adjacent time slots are subjected to the same deep fading, and the BER performance of the system can be further increased. In addition, introducing of time domain interweaving and the SIM modulation does not affect the low PAPR (peak to average power ratio) performance of the SC-IFDMA system.

The invention proposes a detecting method of synchronization between base station and user time in OFDM communication system and the realizing method of time synchronization. The transmitting end superimposes reset PN series to OFDM symbol before the analog-to-digital conversion in OFDM symbol generating process; at the reception end, the base station or user receives OFDM, detects the correlation of part of the OFDM signal sampled value and a preset PN series, it can confirm the starting time of received symbol and the time deviation of OFDM symbol starting time of base station or user. The user adjusts the starting time of him symbol and the time of signal transmitting, makes user synchronous to base station in time.

The invention belongs to the technical field of communication anti-jamming, relates to a generalized spatial modulation (SM) technology, a quadrature amplitude modulation (QAM) technology, and a relevant MIMO (Multiple Input Multiple Output) technology, and provides an adaptive modulation method based on a generalized spatial modulation system. An optimal modulation way combination is selected to transmit signals, so that a minimum Euclidean distance between constellation points can be increased, and the BER (Bit Error Rate) performance of the system is improved remarkably under the conditions of introducing a relatively small feedback quantity and increasing relatively low complexity.

The present invention relates to the technical field of wireless communications, and particularly to a method for reducing the PAPR in a subcarrier index modulation orthogonal frequency division multiplexing system. In the method of the present invention, amplitude limiting processing is performed on a modulated signal first, so that cancelled amplitude limiting noise is obtained, and amplitude limiting noise is obtained finally. Compared with the conventional constellation extension method, the method of the present invention can extend constellation points to a greater extent, thereby significantly improving the PAPR suppression performance and having good BER performance.

The invention discloses a data model dual-drive GFDM receiver and method. The method comprises the steps: respectively obtaining a channel estimation and a signal detection neural network; taking thereal-number result of a matrix comprising transmitted pilot frequency information and a received time domain pilot frequency vector as the input of a channel estimation neural network, and outputtingan estimation of the frequency domain channel state information; obtaining an equivalent channel matrix, taking the real-number result of the equivalent channel matrix and the received time domain signal vector as the input of a signal detection neural network, and outputting the result as the estimation of a GFDM symbol; establishing a demapping neural network, taking an estimation of the GFDM symbol outputted by the signal detection neural network as the input, and outputting the estimation as the estimation of the original bit information; determining the output of the demapping network andthe size of a set threshold, and outputting a detection result of the original bit information according to a determination result. The method has the advantages that the training parameters do not change with the data dimension, the training speed is fast, and the adaptability to different channel environments is strong.

The invention relates to a dynamic compensation method for reducing LED (Light Emitting Diode) nonlinear distortion of a visible light Flip-OFDM (Orthogonal Frequency Division Multiplexing) communication system. The method comprises the following steps: segmenting a modulated subcarrier data vector into a plurality of non-overlapped subsequences; multiplying by a corresponding weighting coefficient, extending to be a hermitian symmetric sequence and then performing IFFT (Inverse Fast Fourier Transform); selecting a weighting coefficient for keeping the negative signal amplitude of a combined signal to be minimum; decomposing the polarity of the combined signal into a Flip-OFDM positive signal and a flip negative signal and limiting the amplitude; carrying an end cut signal of the positive signal at a zero signal position corresponding to the flip negative signal as a compensation signal; restoring the positive signal by a receiving end through the compensation signal. By using the method, PAPR (Peak to Average Power Ratio) in the Flip-OFDM system can be effectively suppressed, and the LED nonlinear distortion is reduced, so that the usability and the reliability of the system are greatly improved.

The invention belongs to the technical field of communication anti-jamming, in particular relates to the spatial modulation (SM) technology, a transmit precoding technology, a phase rotation (PR) technology, phase shifting keying (PSK), an antenna selection technology and multiple input multiple output (MIMO) modulation technology. A receiving end selecting a receiving antenna set and a transmitting antenna set according to an algorithm proposed by the invention according to channel information obtained through channel estimation, and feeds back the transmitting antenna set to the transmitting end; the transmitting end performs the spatial modulation mapping on the transmit data according to the transmitting antenna set fed back by the receiving end. Through the adoption of the method disclosed by the invention, the minimum Euclidean distance between constellation points is increased, the BER (Bit Error Rate) performance of the system is obviously improved under the condition of introducing tiny feedback quantity and increasing small complexity.

The invention provides a multi-user precoding robust construction method under explicit delayed feedback, which is suitable for the multi-user parallel transmission based on the explicit feedback in a wireless multi-antenna transmission system. The method comprises the step that a base station researches all users serviced by the base station to obtain the mean motion speed of each user, computes the Doppler translation of each user according to the speed, computes the time-lapse related coefficient of each user according to a Clark scattering model, forms a delayed coefficient matrix, and substitutes the quantitative channel information fed back by a plurality of user sides and the obtained delayed coefficient matrix into a robust precoding construction formula provided by the method to obtain the precoding. The implementation process of the method in the practical application comprises the steps: 1) channel estimation; 2) delayed feedback; and 3) robustness precoding computation. The application efficiency can be higher if the precoding construction scheme provided by the method is adopted.

According to the multi-wavelength LED underwater visible light communication modulation method based on deep learning provided by the invention, a plurality of LEDs with different wavelengths are used, and based on a deep learning neural network, self-adaptive modulation and demodulation are carried out by using channel and noise power information estimated by a receiver; through training, the non-negative real signal requirement of VLC based on intensity modulation and direct detection can be met, the average optical power of the constellation diagram of the transmitter can be kept constant,the method can automatically adapt to different underwater channel characteristics, and better BER performance can be achieved in most underwater environments under the same spectral efficiency compared with an existing scheme.

The invention relates to a communication anti-interference technology, and particularly relates to an antenna selection technology based on spatial modulation. A method provided by the invention mainly comprises the steps: setting a candidate set P and a selected set S, wherein the set P initially includes serial numbers of all transmitting antennas, and the set S is initially empty; calculating the length of a vector of each column in a channel matrix H, putting a transmitting antenna corresponding to one column with the largest vector length into the selected set S, and removing the transmitting antenna from the candidate set P; calculating decision variables Q of each antenna in the candidate set P and all antennas in the selected set S, putting the antenna in the candidate set P, corresponding to the largest decision variable Q, into the selected set S, and removing the antenna from the candidate set P; and repeating the step until obtaining the selected set S meeting the requirement. The antenna selection technology has the beneficial effect that the BER performance can be greatly improved at lower complexity and feedback quantity. The antenna selection technology is especially suitable for antenna selection of spatial modulation.

The invention claims an adaptive generalized spatial modulation (AGSM) method using joint optimization, and belongs to the technical field of wireless communication. The provided method comprises the steps that symbol modulation constellations are combined with traditional GSM antenna assemblies to form space modulation constellations; a receiving end selects the optimal space modulation constellation under a channel condition according to channel condition information, and feeds the space modulation constellation back to a sending end; and the sending end adopts the space modulation constellation to implement bit mapping in next transmission. Furthermore, an AGSM simplified computation method is provided, the optimal space modulation constellation is selected via an local optimal selection way, and computation times for a Euclidean distance in AGSM can be effectively reduced. Compared with the traditional GSM system, the provided method can effectively enhance BER performance of the system, the feedback quantity is small, and the computation is simple.

The invention discloses a modulation method supporting brightness modulation of an indoor visible light communication system; aiming at the requirement that the visible light communication gives consideration to illumination in actual system, and reliable communication is realized under multiple brightness level conditions and the mixed MPPM modulation method is adopted; different modulation combining schemes are set according to different brightness modulation demands, a receiving terminal judges the ratio of the modulation combination according to the energy detection, and different illumination brightness levels are supported while the reliable transmission for information is ensured. Compared with technical scheme of adopting OOK modulation with redundancy compensation symbol in the standard IEEE802.15.7, and the technical scheme can have obvious performance gain under the indoor optical communication point-to-point communication scene.

The invention discloses a companding method for reducing OFDM (orthogonal frequency division multiplexing) system peak-to-average ratio. By researching the relation between reduced PARP (peak-to-average power ratio) in signals and bit error ratio (BER) in the OFDM system to compromise the same, the novel companding method is provided. The companding algorithm is a method capable of reducing the PAPR of the OFDM system effectively, and the maximum PAPR of output signals can be set so as to meet the requirements of different systems. Further, according to different signal noise ratio (SNR), standard for inverse companding transformer is provided, and a better BER performance receiver can be obtained. Indicated by a simulation result, the companding method can remarkably reduce the PAPR of the OFDM system and has better spectrum characteristics and bit error ratio performance as compared with conventional methods.

The invention belongs to the technical field of communication interference resistance, and particularly relates to a pre-coding method for use in spatial phase modulation. The pre-coding method disclosed by the invention is mainly characterized in that a pre-coding vector is obtained through a receiving end according to an estimated channel matrix H. The method comprises the following specific steps: determining the serial numbers m and n of transmitting antennae corresponding to two constellation points according to the minimum distance between any two points in the constellation diagram of an SM-PSK (Spatial Modulation-Phase Shifting Keying) system; if m is equal to n, directly using theta which is selected at last as an initial vector without adopting remaining algorithms in the step; and if m is unequal to n, setting an angle deviation value deltatheta as 2pi / N, and selecting an optimal vector as a pre-coding vector from a set of alternative pre-coding vectors. The method has the beneficial effects that the minimum Euclidean distance between adjacent constellation points can be expanded, and the BER (Bit Error Rate) performance of the system is improved remarkably under the condition that minimal feedback quantity is introduced into the system and the complexity is increased slightly. The invention is particularly suitable for the pre-coding method for use in the spatial phase modulation.

The invention belongs to the technical field of wireless communication, and relates to an index modulation orthogonal frequency division multiplexing (OFDM-IM) technology, a constellation diagram design technology and an adaptive technology, in particular to a constellation diagram design and adaptive modulation method for the index modulation OFDM system. The constellation diagram design method comprises the following steps: firstly, giving an alternative modulation combination, and designing a proper constellation diagram; and adaptively selecting a modulation way according to the designed constellation diagram, so that each subcarrier wave block selects an optical modulation way from the alternative modulation combination. Compared with a conventional ISIM-OFDM (Interleaved Subcarrier Index Modulation-Orthogonal Frequency Division Multiplexing) system, the constellation diagram design method has the advantages that an adaptive modulation technology is adopted at a transmitting end, so that the situation of relatively high bit error rate of a single modulation way under a poor channel condition is avoided. The constellation diagram is designed, so that the Euclidean distance between modulation symbols can be increased, and the transmission accuracy is increased.

The invention discloses a two-dimensional vacant code index modulation method based on machine learning. The two-dimensional vacant code index modulation method mainly comprises the following steps of1) carrying out serial-parallel conversion on the sending information bits u of a transmitting end; 2) establishing an optimal antenna subset based on an SVM, and constructing a label and antenna combination mapping table; 3) carrying out symbol modulation and index modulation on the sending information bit u after serial-parallel conversion, thereby determining a transmitting antenna, a modulation symbol and a spread spectrum PN code; 4) performing spread spectrum on the modulation symbol, and transmitting the spread spectrum to a receiving end; and 5) using the receiving end to receive thespread spectrum signal and perform the correlation characteristic detection on the spread spectrum signal; 6) performing estimation detection on the despread signal by using the CNN; and 7) demodulating and demapping the estimated demodulation symbol and antenna with the PN code index value so as to restore the source information bit. According to the method, the advantages of a spread spectrum technology in spatial modulation and code index modulation are combined, the multi-antenna channel link resources are utilized, and due to the fact that the spread spectrum technology is used, the method has certain anti-interference and anti-multipath capacity.

The invention discloses an interference cancellation detection method for an OFDM transmission system of a short cyclic prefix. The invention provides an effective interference cancellation detectionscheme for a scene of severe inter-subcarrier interference (ICI) and inter-symbol interference (ISI) caused by insufficient cyclic prefixes of OFDM signals in a multipath fading channel. The window radius of partial interference cancellation is calculated according to a channel delay power spectrum, and partial interference cancellation detection is sequentially carried out on designed subcarriergroups. According to the method, the detection time delay and the hardware implementation complexity can be well balanced, and the bit error rate leveling problem of the short cyclic prefix OFDM system is effectively improved while the conventional interference cancellation operand is reduced.

The invention belongs to the technical field of communication, and relates to a receiving and sending end antenna selection method based on a channel norm of a generalized spatial modulation system. The invention provides the receiving and sending end antenna selection method based on the channel norm of the generalized spatial modulation system. According to the technology, a proper receiving and sending antenna set is selected according to channel information, the average SNR of a receiving end can be maximized, and the BER performance of the system is greatly improved under the condition that less feedback quantity is imported and lower complexity is increased for the system.

The invention discloses a reference diversity design algorithm of a multistage code shift differential chaotic shift keying system, and relates to a modulation technology in a wireless communication technology. A transmitter uses the orthogonal characteristic of a walsh code sequence to superpose a reference signal with reference diversity and a plurality of information bearing signals on the sametime slot to obtain a transmission signal, and the transmission signal passes through a wireless channel and is influenced by multipath fading and additive white Gaussian noise; the reference signalsdamaged by the noise are averaged by the receiver to reduce the interference of the noise on the reference signals, the denoised smooth reference signals are correlated with the information bearing signals to obtain decision variables, and hard decision is performed on the decision variables to obtain information estimation bits; and a theoretical BER of the proposed system is derived through a decision variable, and an optimal reference diversity number of the MCS-DCSK-RD system is determined according to the theoretical BER. System noise can be reduced, and the system performance is improved.

The invention belongs to the technical field of communication, and relates to a joint detection method for signals of a massive MIMO uplink system. According to the scheme of the invention, the methodincludes the following steps that: firstly, an iterative matrix is constructed, and a low-complexity iterative scheme is proposed based on the constructed matrix; and then, a steepest descent methodand the proposed iterative method are mixed to accelerate the proposed iterative method; in addition, the computational complexity is reduced by skillfully utilizing the properties of inversion of partitioned matrices and a matrix-vector multiplication; and then, the detailed convergence proof and complexity analysis are performed; and finally, simulations prove that the BER performance of the proposed algorithm is better than that of most existing iterative algorithms and the near-optimal performance of an MMSE algorithm can be reached in a small number of iterations.

The invention belongs to the technical field of communication jamming resistance, and particularly relates to a power allocation method for a receiver space modulation system. According to the method,a power allocation algorithm is applied to the receiver space modulation system; compared with a traditional receiver space modulation system model, the scheme has the main advantage that a power allocation module is added at a transmitter by means a limited feedback link, the transmitting power is reasonably allocated by means of current channel information, and therefore the performance can beoptimal; and on the condition that the transmitting power is the same, the method can achieve great BER performance improvement compared with the traditional receiver space modulation system.

The invention belongs to the technical field of communication anti-interference, and relates to spatial modulation (Spatial Modulation, SM) technology, minimum mean square error (Minimum Mean Square Error, MMSE) technology, and related MIMO (Multiple Input Multiple Output) technology. The invention provides a new MMSE soft detection algorithm based on an SM-OFDM system. According to the technology, the coefficient of an MMSE detector is theoretically calculated, soft information and external information of an iterative detector are solved by prior information LLR, and to-be-detected data is iteratively updated, so that the BER perform ace of the system is significantly improved.

The invention, which belongs to the technical field of digital communication, provides a method for realizing channel equalization by using frequency-domain oversampling in an orthogonal frequency division multiplexing (OFDM) receiver. According to the method, oversampling is carried out on a received OFDM signal in a frequency domain; oversampling is carried out on estimated channel information in the frequency domain; equalization is carried out on a virtual subcarrier signal obtained by oversampling by using an oversampling channel; and the virtual subcarrier signal after equalization is converted into a time-domain signal and then is converted into a practical sub carrier data signal in a non-oversampling frequency domain. According to the method, an output signal can be demodulated and decoded and thus data transmitted by an OFDM system can be restored. An error rate performance of an OFDM system receiver can be improved by enhancing an oversampling rate.

The invention belongs to a field of communication anti-jamming technique and specifically provides an optimal power distribution method for an SM-OFDM (Spatial Modulation-Orthogonal Frequency Division Multiplex) system under imperfect channel estimation. According to the method, a receiving terminal obtains system BER (Bit Error Rate) upper bound according to an estimated channel so as to obtain an optimal power distribution scheme. The method specifically includes steps of obtaining an estimation channel of data sub carriers by adopting an eta-order generalized linear interpolation technology according to the estimation channels of eta pilot frequency sub channels which are the nearest to the data sub channels; calculating the average BER upper bound union set bound of the data sub carriers; and finally obtaining the optimal power distribution scheme between a pilot frequency symbol and a data symbol through minimizing the BER upper bound. In a condition of limited total power, the BER performance of the SM-OFDM system can be improved distinctively without computation complexity increase. The method provided by the invention is suitable for all the generalized linear interpolation technologies.

The invention relates to the wireless communication field, and discloses a multi-input and multi-output receiving signal detection method and a receiving device, so that the system can flexibly come to a compromise between the complexity of a detection algorithm and good BER performance. As for the sub-flow with better signal quality, a detection algorithm with lower complexity is adopted; and as for the sub-flow with poor signal quality, the detection algorithm with high BER performance is adopted, wherein, the preset threshold is one of the preset thresholds at two levels at least.

The invention provides a parallel multiuser detection method in an SCMA system. The method comprises: during parallel iterative decoding of an SCMA system, if locations of greatest elements in a codeword confidence vector of a certain user node in ith iteration and (i-1)th iteration in an SCMA factor graph are different, the user node is determined to be unstable, a user corresponding to the user node can not be judged in advance, and a next iteration process is executed; and otherwise, the user node is determined to be stable and threshold condition judgment is carried out on the user corresponding to the user node. According to the method provided by the invention, on the basis of the existing threshold-based MPA algorithm, judgment on the stability of the user node is added; and only the user that meets the threshold condition and passes the user node stability judgment can be processed by decoding in advance. Therefore, reliability of judging the codeword by the threshold-based MPA algorithm in advance is improved; and the message iteration becomes sufficient on the condition of low threshold, so that the good BER performance is obtained.