39 results about "SC-FDE" patented technology

Various embodiments of multi input multi output (MIMO) communication systems include a transmit Tomlinson-Harashima Precoding (THP) technique and a single carrier frequency domain equalization (SC-FDE) technique. Parallel THP-FDE and successive THP-FDE are proposed based on the minimum mean square error (MMSE) criterion. For the successive THP-FDE technique, where all transmit streams are subsequently precoded, both suboptimal and optimal MMSE ordering algorithm are set forth. Since the feedback processing is performed at the transmitter, no error propagation problem exists in the THP-FDE MIMO techniques, yielding significant performance improvements over conventional FDE MIMO techniques. Applying channel prediction and THP compensation techniques can also further enhance performance.

An apparatus receives data encoded in a format where information bits for transmission are mapped into symbols each carrying a plurality of bits, some of which are encoded through a pulse position modulation (PPM) format and the rest of which are encoded through an additional modulation format on at least one PPM pulse. The receiver detects the signal through a dual-polarization coherent receiver front-end, and recovers polarization components of the signal by decoding a first non-zero portion of a plurality of bits carried by a symbol based on slot position of at least one PPM pulse in the polarization components and a second non-zero portion of the plurality of bits carried by the symbol based on the additional modulation carried by at least one PPM pulse in the polarization components. Pilot-assisted single-carrier frequency-division equalization (PA-SC-FDE) may be used for reliable signal reception in the presence of severe PPM errors.

The invention relates to a frequency-division duplexing transmission method for a wideband wireless communication system, belonging to the technical field of digital information transmission. The method comprises the following steps of: carrying out downlink multiple access at the transmitting end of a base station by adopting a time-domain and frequency-domain united orthogonal frequency division multiple access technology to obtain a downlink signal; carrying out uplink multiple access at the transmitting end of user equipment by adopting a time-domain and frequency-domain united single carrier multiple access technology to obtain an uplink signal; and carrying out duplexing transmission on the downlink signal and the uplink signal by adopting a frequency-division duplexing frame structure. A TFU-OFDMA (Time domain and Frequency domain United Orthogonal Frequency Division Multiple Access) technology provided by the invention can be used for solving the multiple access problem of modulation by adopting TFU-OFDM (Time domain and Frequency domain United Orthogonal Frequency Division Multiplexing) and has the advantages of flexibly allocating wireless resources, effectively resisting deep fading and narrow-band interference and the like; and by using a TFU-SCMA (Time domain and Frequency domain United-Single Carrier Multiple Access) technology provided by the invention, the multiple access problem of modulation by adopting the improved SC-FDE (Single Carrier-Frequency Domain Equalization) can be solved, the advantages that the transmitting end has low complexity and peak-to-average power ratio by the SC-FDE technology can be retained and the synchronization and channel estimation can be better carried out by the receiving end.

The invention relates to a low-signal-noise-ratio SC-FDE (Single Carrier-Frequency Domain Equalization) system synchronization method and synchronization device. The synchronization method comprises the following steps that: a transmitting end transmits a data frame including a first training sequence A, a second training sequence B, a cyclic prefix (CP) and a data symbol; and a receiving end receives the data frame and executes the following steps: S1, detecting the data frame by using the first training sequence A with a parallel code phase search algorithm and acquiring a coarse frequency offset estimation value to correct a coarse frequency offset value in order to obtain a data symbol subjected to coarse frequency offset correction; S2, performing fine frequency offset estimation by using the second training sequence B to correct a fine frequency offset value in order to obtain a data symbol subjected to fine frequency offset correction; and S3, performing symbol timing estimation by using the second training sequence B. Through implementation of the low-signal-noise-ratio SC-FDE system synchronization method and synchronization device, the influence of noise can be resisted effectively; a large carrier frequency offset detection range can be realized; excessively large offsets are corrected; and high-accuracy synchronization of signals is finished.

The invention discloses a phase noise suppression method under the low-complexity channel estimation of an SC-FDE (single carrier-frequency domain equalization) system. The phase noise suppression method comprises the following steps of: forming a training sequence by virtue of special characters, obtaining the responses of a small amount of frequency points of CFR (crest factor reduction) and a CIR (channel impulse response) by virtue of a LS (least square) algorithm according to the received signal, obtaining the initial CFR influenced by a phase noise CPE (common phase error) via a discrete Fourier transform interpolation filter, and performing time-domain noise power estimation and frequency-domain noise power estimation according to the training sequence; after an established channel is obtained, extracting the effective order of the CIR in a time domain, and calculating the copy of the special character received signal; using special characters as cyclic prefixes of transmission data blocks, estimating the ratio of the CPE on one cyclic prefix to the CPE in the initial established channel by virtue of an MMSE (minimum mean square error) algorithm, and then obtaining the ratio of the CPE of the whole data block to the CPE in the initial established channel via linear interpolation; and finally multiplying the CPE ratio with the initial CIR influenced by the phase noise CPE to track the whole channel of the present data block, and suppressing phase noise interference via the frequency-domain MMSE equalization. The channel estimation algorithm disclosed by the invention is low in complexity, thus reducing the complexity of a phase noise suppression algorithm.

Disclosed is a transceiving apparatus and method in which a space frequency block coding (SFBC) technique is applied to the SC-FDE technique. The transceiving method encodes an input signal into frequency-domain blocks so as to output at least two signal blocks in parallel to each other, inserts a cyclic prefix (CP) into the output signal blocks, and outputs the signal blocks through the same sub-channel by means of corresponding antenna.

The invention discloses a channel estimation method based on a unique word in a single carrier frequency domain equalization system. The channel estimation method comprises the following steps: designing a frame structure, estimating noise variance and estimating channel frequency response. In the process of designing the frame structure, more than one data block forms a long frame, and a section of UW sequence formed by a plurality of UWs is inserted in each long frame. In the process of channel estimation, firstly an LS algorithm is used for determining a frequency response value of each sub-channel, the frequency response value goes back to a time domain through IDFT/FFT, the noise variance is estimated according to a channel pulse response value which exceeds a cyclic prefix length, then noise reduction treatment is conducted on the channel pulse response value, eventually the channel pulse response value is converted to a frequency domain through DFT/FFT, and channel frequency response values are estimated. According to the channel estimation method based on the unique word in the single carrier frequency domain equalization system, specific to characteristics of slow fading channels, a traditional SC-FDE frame structure is improved, a channel estimation algorithm based on DFT is improved on the basis, and meanwhile the frequency response and the noise variance of the channel are estimated, and therefore the performance of the algorithm is improved.

The invention discloses a signal to noise ratio estimation-based frequency offset regulation method, which comprises the following steps of: setting an initial value SNR_reg of a signal to noise ratio register, and the corresponding initial value F_reg of a frequency offset register, and setting a counter n to be equal to 0; setting n to be equal to n+1, and acquiring an estimated frequency offset value Fn of the nth frame of data frames of a single carrier frequency domain equalization (SC-FDE) system; acquiring an estimated signal to noise ratio value SNRn of the nth frame; judging whether the SNRn is greater than the SNR_reg or not, and if the SNRn is greater than the SNR_reg, modifying the F_reg of the frequency offset register to be equal to Fn, and determining the estimated frequency offset value of a current frame to be Fn; if the SNRn is not greater than the SNR_reg, keeping constant the F_reg and modifying the estimated frequency offset value Fn of the current frame to be equal to F_reg; and repeating the steps, regulating the estimated frequency offset values Fn of all the frames. In the method, when a signal to noise ratio is estimated, pilot frequency data used for channel estimation is converted into a frequency domain on the basis of not changing the structure of the data frame for the characteristics of the SC-FDE system, so the accurate estimated signal to noise ratio value can be obtained, and is utilized to adaptively regulate frequency offset to well solve the problem that the estimated frequency offset value has an error under a low signal to noise ratio.

The invention belongs to an oversampling receiving method of a single-carrier wave frequency domain equalization (SC-FDE) transmission technology, which comprises the following steps of: filtering a received transmitting signal; oversmapling as the integer multiples as that of the frequency of a transmitted symbol from 2 times to 6 times; removing a circulatory prefix; converting time frequency; equalizing an information channel; and converting the time frequency and demodulating the signal to reduce the signal into a bit signal. Aiming at the phenomenon that the bandwidth of the transmitting signal is enlarged after a transmitting terminal signal is shaped and filtered, the oversampling receiving method multiply improves the sampling frequency of a receiving end (device), removes the circulatory prefix of the sampled data signal, correspondingly conveners by means of FFT, and equalizes the information channel to reduce the initial signal with fidelity. Therefore, the method has the characteristics of obviously improving the performance of the SC-FDE system under the condition of the same spectrum efficiency, greatly reducing the error rate, and effectively improving the quality, the reliability and the transmission efficiency of the communication, etc.

The invention discloses an integer frequency doubling offset and channel parameter joint estimation algorithm with an ultra-low complexity in a single carrier frequency domain equalization (SC-FDE) system. The algorithm comprises the following steps: (1) generating a training sequence; (2) obtaining a frequency domain signal of a receiving end; (3) constructing a mutual fuzzy function Doppler zero section of a Chu sequence; (4) constructing a metric function: utilizing the zero section of the Chu sequence to conduct joint estimation for an integer frequency doubling offset and channel parameter, and constructing the metric function; (5) obtaining integer frequency doubling offset estimation from the metric function; (6) obtaining corresponding time domain channel swashing response estimation according to the integer frequency doubling offset estimation. Characters of a mutual fuzzy function of the Chu sequence are utilized by the algorithm, the algorithm just needs using the zero section to construct an estimation metric function, and the algorithm not only can conduct estimation for integer frequency doubling offset, but also simultaneously can conduct channel estimation. Compared with a traditional algorithm, the algorithm which does not need multi-group cross-correlation operation has the ultra-low complexity.

The invention belongs to the technical field of shortwave communication, and particularly relates to a channel estimation method for Single Carrier Frequency Domain Equalization (SC-FDE) under a shortwave communication channel. The channel estimation denosing method suitable for the single carrier frequency domain equalization under the shortwave communication channel based on the SC-FDE is provided. Due to the poor shortwave channel and the effect of Gaussian noise, the accurate channel estimation value is very difficult to obtain, the very accurate frequency domain equalization cannot be carried out, and very good system performance cannot be obtained. The frequency guide block data initial channel estimation value is obtained through a least squares (LS) algorithm or a linear minimum mean square error (LMMSE) algorithm, the noise on a main path is removed through a method of sliding a frequency guide block, the noise on a low-energy path is eliminated through a low-energy path zero setting method, and the accurate channel estimation value is obtained.

The invention relates to a wireless sensor network channel estimation method based on SC-FDE and virtual multiple antennas, wherein, firstly, a transmitting end determines length value of Chu sequences which are taken as training sequences; secondly, noise powers of a relay end and a receiving end are estimated and the maximum non-zero tap number of channel time domain responses among various nodes is determined, and then power distribution coefficients of various nodes are determined; thirdly, corresponding Chu sequences are selected by the transmitting end according to the determined length value and the power distribution coefficients, added with cyclic prefixes, and transmitted in a first time slot; fourthly, the relay end receives signals which are transmitted by the transmitting end and then removes the cyclic prefixes of the signals, and novel cyclic prefixes are added after the signals are multiplied by power normalization coefficients and the power distribution coefficients, and then the signals are transmitted in a second time slot; the receiving end respectively receives signals in the first time slot and the second time slot, and various received signals are transformed to frequency domains after removal of the cyclic prefixes; fifthly, estimation of the minimum variance unbiased channel is performed, thereby channel estimation with high precision and low complexity in collaborative communication of the virtual multiple antennas is realized.

A transmission method using a massive MIMO (Multiple-Input and Multiple-Output) scheme with an arrangement 108 of N_m×N_b antenna elements at the transmitter, arranged in N_m sets of N_b antenna elements or N_b sets of N_m antenna elements based on SC-FDE (Single-Carrier with Frequency Domain Equalization) schemes with large constellations that is compatible with low-cost, highly-efficient, nonlinear amplifiers 106, while allowing spatial multiplexing gains.

The transmission structure of this transmission method decomposes in 103 the modulated symbols from 102 associated to a given constellation as the sum of N_m polar components that are modulated as N_m BPSK (Binary Phase Shift Keying) signals. Each of these BPSK signals can be regarded as an OQPSK (Offset Quadrature Phase Shift Keying) signal in the serial format that is specially designed to have good tradeoffs between reduced envelope fluctuations and a compact spectrum.

The invention discloses to an SC-FDE system based on MAP equalization and a construction method of a pilot frequency structure in the SC-FDE system based on the MAP equalization, relates to the SC-FDE system and the construction method of the pilot frequency structure in the SC-FDE system, and is used for solving the problems of high peak-to-average ratio of signals emitted by an OFDM (Orthogonal Frequency Division Multiplexing) system and sensitivity on a frequency offset and a phase noise. A mapping signal input end of a mapping unit is connected with a signal output end of a signal generator, and a modulation signal output end of a modulator is connected with the signal input end of a signal channel; the signal output end of the signal channel is connected with the signal input end of a Fourier transform module; a transformation signal output end of the Fourier transform module is connected with a transformation signal input end of a signal channel estimating and balancing unit; the signal output end of the signal channel estimating and balancing unit is connected with the signal input end of the Fourier transform module; a demodulation output end of a demodulator is connected with a demodulation signal input end of a decoder; and a decoding signal output end of the decoder is connected with a decoding signal input end of a judging unit. According to the SC-FDE system based on the MAP equalization and the construction method of the pilot frequency structure in the SC-FDE system based on the MAP equalization, a multipath effect of a single carrier system is eliminated.

The invention provides an AMC (Adaptive Modulation and Coding) method based on an SC-FDE (Single Carrier-Frequency Domain Equalization) system, relates to an AMC modulation and encoding method, and belongs to the field of wireless radio. In order to solve the problems that the a channel cost is increased and the spectrum efficiency is low under the condition that the SC-FDE system is at a time-varying multi-path channel, caused by that a channel needs to be subjected to estimation and policy exchange at any time when current information is transmitted, the invention provides the adaptive modulation and coding method by combining an AMC technology and self characteristics of an SC-FDE system theory; policy lasting time is introduced to restrict the utilization time of the policy and the switching frequency of the policy, so that the optimal policy which is matched with the current channel state is searched in a policy switching table; only if the average lasting time of the selected optimal policy is exceeded, the method can carry out the next time of the selection and the switching of the optimal transmission policy, so that the channel estimation and policy switching processing efficiencies are reasonably reduced, the spectrum efficiency is effectively improved and the system throughput is maximized. The AMC method based on the SC-FDE system is applicable to the field of a wireless radio communication technology.

The invention relates to a design method of an HARQ (Hybrid Automatic Repeat-request) communication way applied to SC-FDE (Signal Carrier Frequency-Domain Equalization) baseband system baseband system. The design method is characterized by comprising the following steps of: on the premise of a forward correction communication way of the common SC-FDE baseband system, analyzing defects of the system; then combining a technical principle related to the HARQ, taking a super-frame as a unit and transmitting data information of each frame into a signal channel decoding part of a receiving end to be judged; if finding that errors cannot be corrected, executing an instruction for repeatedly transmitting the data at the next moment; and otherwise, avoiding transmitting the data again and continually carrying out the transmission of the next frame. According to the invention, the design scheme of the system combining the SC-FDE and the HARQ technologies takes suitable reduction of a system throughput as the cost to obtain a lower error rate of the system, so that the received data become more accurate.

The invention discloses a signal processing method based on single carrier-frequency domain equalization (SC-FDE). The signal processing method comprises the following steps: an optical transmitter generates unique word (UW) sequences and synchronous data blocks; the UW sequences form a data frame, and the synchronous data blocks and the data frame form a super-frame; and finally the super-frame is taken as a base-band signal to be sent to an optical receiver. Meanwhile, the invention further discloses a signal processing system based on SC-FDE. By adopting the signal processing method and the signal processing system based on SC-FDE, hardware equipment of the optical transmitter can be simplified, the cost of the optical transmitter can be reduced, the time synchronization accuracy can be improved, and the occupied processing resource can be reduced during the channel estimation process.

The invention relates to the technical field of wireless communication, and particularly relates to a communication method based on SC-FDE (single carrier frequency domain equalization) and physical layer network coding. The invention aims to further improve performance of a wireless communication system, improve network throughput of the system, reduce a bit error rate of the system and achieve remote communication of asynchronous signals. According to the communication method disclosed by the invention, by applying an SC-FDE technology in processes of a first time slot and a second time slot of a two-way relay communication system, signals sent by two source nodes are subjected to time synchronization, two source node signals which are asynchronous in time are used as signals which reaches by different paths, and as long as an asynchronous range is in a range of a cyclic prefix, recovery can be carried out by frequency domain equalization, so that the bit error rate of the system is reduced; and in the process of the second time slot, a physical layer network coding technology is applied to improve network throughput of the communication system.

The invention belongs to a receiving processing method in a single-carrier wireless communication system. The method comprises: carrying out down-conversion treatment, A/D conversion, cyclic prefix removal, FFT treatment, communication channel estimation, linear equalization, demodulation, decoding and subsequent demodulation on a received transmitting signal. The invention is characterized by directly carrying out demodulation after carrying out linear equalization at a receiving terminal; then carrying out decoding treatment which contains bit log likelihood ratio treatment, candidate symbol vector listing and maximum likelihood treatment; and finally demodulating and sending the decoded data. In the invention, the error rate is only 15-50% of that of the background technology and is equivalent to that of the SD (spherical decoding) technology with higher complexity, and the performance gain can be improved by about 5dB; and under the condition of the same spectrum effectiveness, the invention has the characteristics that the receiving processing complexity of the communication system is low, the performance of the SC-FDE system is obviously improved, the error rate is greatly reduced, the communication quality, the reliability and the transmission efficiency are effectively improved, etc.