45 results about "Rayleigh channels" patented technology

The invention discloses a complete UAV (unmanned aerial vehicle) relay model which comprises two types of links, wherein one type of the links is a ground-air link from a ground station to a UAV, and a channel under the link is regarded as a Rician channel; and the other type of the links is an air-air link from a UAV to a UAV, and a channel under the link is regarded as a Rayleigh channel. Although the analysis is complicated, the relay model and a channel model can well conform to actual situations. Based on the channel model, the invention also provides a method for solving the interruption probability, and the method cannot be influenced by the channel model and is suitable for any channel model with a precondition that a channel matrix of the channel model must be known. By virtue of MATLAB (matrix laboratory) simulation, a curve of characteristic values of a channel matrix H can be obtained, then by virtue of curve fitting, a mathematical expression of the characteristic values can be obtained, and then a cumulative distribution function of the characteristic values is obtained, which is much simpler. By use of the method provided by the invention, the overall interruption probability of the two sections of the links is obtained, and the interruption probability under an actual situation is well reflected.

The invention discloses a distribution-type optical-fiber Raman temperature sensor adopting circulating pulse coding and decoding and Rayleigh demodulation, and the sensor comprises a pulse optical-fiber laser, an acoustic-optic demodulator, an integrated optical-fiber wavelength division multiplexer with four ports, two photoelectric receiving amplification modules, a coding-decoding demodulation digital signal processor, an optical-fiber temperature sampling ring, an intrinsic temperature measuring optical fiber, a digital temperature detector and a personal computer (PC). The sensor codes and decodes a signal on the basis of the circulating S matrix conversion, and the online location temperature measurement of the optical fiber is realized by utilizing an effect that the optical-fiber Raman optical strength is demodulated by the temperature and utilizing an optical time domain reflection principle. The circulating laser pulse coding and decoding is realized, and a Rayleigh channel is used as a temperature demodulation reference channel, so that the signal-to-noise ratio of the system is greatly improved, and the measuring precision and the measuring distance of the system are improved.

The invention discloses a time domain self-correlated flat fading channel modeling method. The method comprises the following steps: firstly simulating a flat fading channel through a computer, and verifying the flat fading channel; mainly comprising the following steps: firstly initializing a parameter which comprises a maximum Doppler frequency shift, system sampling frequency, system sampling point number N, and a flat filter correlated parameter; a method for producing the flat fading channel is as follows: inputting a flat filter through two paths of Gauss white noise random sequences, thereby respectively producing a colored Gauss white noise random sequence with the flat Doppler power spectrum, and respectively forming a real part and a virtual part of a flat fading channel; and finally, performing one-order and two-order statistical analysis on the flat fading channel, and then designing a channel hardware simulation system. By using the method disclosed by the invention, the Rayleigh channel flat Doppler power spectrum is convenient to realize by using a forming filter, namely, the flat filter, and the envelope obeys the Rayleigh distribution.

An orthogonal frequency division multiplex (OFDM) receiving system for changing a fast Fourier transform (FFT) window period using a guard interval, and a method for the same are provided. The method includes extracting scattered pilots, which are inserted into a symbol at intervals of predetermined samples, from a received OFDM signal, estimating a symbol timing offset using the extracted scattered pilots and setting a symbol timing synchronization point in the data transmission interval, and adding samples in a predetermined interval in the data transmission interval to samples in an interval obtained by subtracting a predetermined length from the useful symbol interval starting from the symbol timing synchronization point and performing FFT with respect to the result of addition. Accordingly, symbol timing synchronization and channel equalization can be accurately performed without having ISI even when a symbol start point is not correctly decided under a multi-channel (or a Rayleigh channel) or a pre-ghost channel environment.

The invention discloses a quadrature amplitude modulation signal identifying method based on mixed moment and fisher discrimination, mainly solving the problems of large calculation amount and low identification rate in the prior art. The method comprises the following processes: sampling a received signal; respectively calculating a secondary moment, a fourth-order moment and a sixth-order moment of a sampled sequence; normalizing and combining results of the moments to acquire new characteristic quantity; determining two threshold values which discriminate that modulation types are unequal, and comparing the characteristic quantity after the characteristic quantity of the received signal is projected with the threshold values; and determining the signal to be a 64 QAM signal if the projected characteristic quantity is more than the larger threshold value, and determining the signal to be a 128 QAM signal if the projected characteristic quantity is less than the larger threshold value and more than the smaller threshold value, and determining the signal to be a 32 QAM signal if the projected characteristic quantity is less than the smaller threshold value. The method has excellent identification performance under a Rayleigh channel and low signal to noise ratio, ensures that the identification rate can reach 98 percent under a condition of the signal to noise ratio 5dB, and can be used for automatic identification of the quadrature amplitude modulation signal without priori information.

The present invention provides a multiple-aerial system transmitting system and a modulation mode selecting method of the non-ideal communication channel. In the Rayleigh channel mode the receiver is provided with ideal communication channel information and adopts the maximum likelihood detector for respectively simulating in different modulation modes to obtain the system error code ratio curve. According to the request of the system error code ratio, the ideal signal-to-noise ratio threshold of the complexing system and the diversity system satisfying the request of the error code ratio is obtained. Afterwards in the actual communication system, the non-ideal signal-to-noise threshold is obtained with the mean square error between the signal-to-noise ratio threshold and the non-ideal communication channel information, and the non-ideal signal-to-noise ratio is compared with the signal-to-noise of current system. Then a transmitting mode and modulating mode which satisfy the request of the error code ratio and have maximum frequency spectrum efficiency are selected for feedbacking to the transmitting side. The transmitter adjusts the current transmitting mode and modulating mode according to the feedback information. The invention can correctly select the transmitting mode and modulating mode according to the system environment and the mean square error of the non-ideal communication channel information and evidently increase the frequency spectrum efficiency of the system.

The invention relates to a double-direction four-channel coupled distribution-type optical-fiber Raman temperature measuring system, which comprises a broadband light source, a double-direction four-channel optical-fiber coupler, a single-mode fiber, a first optical splitter, a second optical splitter, a first photoelectric detection circuit, a second photoelectric detection circuit, a third photoelectric detection circuit, a signal collection card and a computer; and the double-direction four-channel coupled distribution-type optical-fiber Raman temperature measuring system is mainly used for the monitoring the temperature of the places such as electric power cables, tunnels, oil pipes, flammable and explosive places and the like in real time, the sensitivity is high, the response speed is fast, the transmission distance is long, and the electromagnetic interference resistance is strong. A Stokes channel and an anti-Stokes channel are used for demodulating the temperature information, and a Rayleigh channel is used for demodulating the position information; and the temperature resolution is 0.8 DEG C, the space resolution is equal to or less than 1m, and strong practicability is realized.

The invention relates to a receiver of an OFDM system and a moving speed estimation method thereof, belonging to the field of wireless communication. The method comprises the following steps: 1) leading the receiver to convert a time domain OFDM signal r(n) to a frequency domain OFDM signal R(n); 2) leading the receiver to carry out channel estimation on the frequency domain OFDM signal R(n) and obtaining frequency domain channel response Hi of each OFDM symbol; 3) leading the receiver to calculate the change value delta H of the frequency domain channel response between the different OFDM symbols according to the obtained frequency domain channel response; and 4) leading the receiver to estimate the current moving speed of the receiver according to the change value delta H; and the system comprises a fast Fourier transform module, a channel estimation module, a frequency domain channel response change estimation module and a moving speed estimation module of the receiver. The moving speed estimation method of the receiver is simple, rapid and easy to implement and is not only applicable to Rayleigh channels, but also applicable to Rician channels; furthermore, the estimation precision is high.

The invention discloses a method for forwarding multi-system soft information in a Rayleigh channel. When high order modulation is adopted, under a low SNR (Signal Noise Ratio) region, an MPSK (Multiple Phase Shift Keying) signal estimation forwarding method in a fading channel is selected; and under a high SNR region, an MPSK signal mutual information forwarding method in the fading channel is selected. The method for forwarding the multi-system soft information in the Rayleigh channel has the beneficial effects that the system bit error rate performance is better; and under the condition that the SNR is the same as relay number, the data rate is gradually increased along with the increase of system number, and the reliability of each scheme is obviously reduced, but the bit error rate performance of a soft information forwarding scheme is still superior to an AF scheme and a DF scheme.

The invention discloses a LoRa signal transmission method based on MIMO, and the method comprises the steps: carrying out the modulation of a to-be-transmitted LoRa signal x, so as to obtain a modulated signal; carrying out the space-time group coding of the modulated signal; adding noise to the coded signal, and transmitting the signal with noise on a Rayleigh channel; enabling a receiving end todecode the received signal, and carrying out the demodulation of the decoded signal so as to obtain a received signal x'. Compared with the prior art, the method can effectively resist the Rayleigh fading in a novel transmission mode of LoRa+MIMO, and improves the transmission reliability of the LoRa signal in the Rayleigh channel. In other words, the multi-antenna technology is added to the LoRatechnology, and the method employs the mode of space-time group coding for signal transmission, and can increase the capacity of the channel, so as to improve the diversity order of the signal transmitting and receiving ends, obtaining the diversity gain so as to resist the Rayleigh fading, and improving the transmission reliability of the LoRa signal in the Rayleigh channel.

The invention discloses a quick channel simulation method and a quick channel simulation device of an amplify-forward relay system. The quick channel simulation can be performed for the amplify-forward relay system, a general simulated channel from a transmitting terminal to a receiving terminal can be rapidly generated after number of antennas and correlation coefficient of the transmitting terminal, a relay terminal and the receiving terminal and independent average of Rayleigh channels and variance are acquired. Correlation channels are established from a transmitter to the relay terminal and the terminal to a receiver, then correlation matrix of the general simulated channel is calculated according to the correlation coefficient of the transmitting terminal, the relay terminal and the receiving terminal; and finally a channel model is established according to the correlation matrix of a general channel. The quick channel simulation method for the simulations of the amplify-forward relay system has the advantages that correlation of a base station terminal, the relay terminal and the receiving terminal and transceiver link correlation are fully taken into the consideration of the established model, and an entire link can be simulated truly and accurately by the model; definition is strictly abided in cultivating the correlation coefficient to make the same accurate and reasonable; and the whole link can be simulated from the transmitter to the receiver to achieve effects of convenience and conciseness.

The invention belongs to the technical field of wireless network virtualization, and discloses a wireless network virtualization method based on equivalent capacity in a single-cell LTE-A system. The method comprises the following steps: introducing an LTE-A uplink system as a system model and a wireless channel as a Rayleigh channel; representing the Rayleigh channel through a finite state Markov model, dividing a channel state threshold to acquire a state transition probability matrix; computing a probability distribution of a service rate in a scheduling slot; computing equivalent capacity information when each service process selects each resource distribution mode in one scheduling slot; establishing a target function of a resource allocation model with the maximum system equivalent capacity; and solving out a channel allocation variable of the resource allocation model by use of a branch and a bound method. The problem that the data is inaccurate due to the time-variant characteristic and the attenuation characteristic of a wireless channel is solved. The customization service is provided for the services types in different varieties, the overall overhead for the deployment and the operation of a mobile cellular network is lowered.

The invention discloses a planar compact low-coupling four-polarization MIMO antenna based on an orthogonal mode, which comprises a first radiator and a second radiator based on the orthogonal mode, the first radiator adopts an annular structure, the second radiator adopts a microstrip patch structure, a radiation mode of an electric dipole (Ex) and a magnetic dipole (Hz) is obtained on the first radiator, and two orthogonal TM11 microstrip antenna modes (Hx, Hy) are obtained on the second radiator. According to the invention, the internal space of the first radiator is fully utilized, the second radiator is arranged in the first radiator, four polarization modes are obtained in a planar structure, and the antenna has the characteristics of compact structure, low coupling and the like; the TM11 mode working frequency of the second radiator is reduced through the fractal structure, and the second radiator and the first radiator work in the same frequency band. According to the invention, the vector characteristics of the electromagnetic field are effectively utilized, and the channel capacity greater than 3 * 3 and close to 4 * 4 independent identically distributed Rayleigh channels can be obtained in a multi-path rich propagation environment through a compact structure.

The invention discloses an orthogonal index modulation method based on diagonal space-frequency codes. The diagonal space-frequency codes are used as a sending signal matrix. According to the invention, firstly, two modulation symbols are associated through a Hadamard matrix and a rotation matrix to construct a diagonal code, in addition, index numbers in a space-frequency resource block (RB) are independently selected twice, and different space-frequency units are utilized to modulate and construct homodromous and orthogonal components of the diagonal code to obtain a DSFC-QIM sending signal matrix. According to the invention, DSFC-QIM code word design is carried out on each resource block, so that second-order transmit diversity can be obtained. Simulation results show that under independent and related Rayleigh channels, the method provided by the invention obtains better bit error rate performance than the existing QSFIM scheme.

The invention relates to a data transmission method of a multi-packet feedback opportunistic route, in particular to the data transmission method of the multi-packet feedback opportunistic route based on an ETX value under Rayleigh channels. System feedback response expenses are lowered. The data transmission method of the multi-packet feedback opportunistic route is applied to an opportunistic route strategy in which a plurality of nodes (dozens of nodes to hundreds of nodes) exist in an area, Rayleigh fading channels with random channel parameters are formed among the nodes, the ETX value is calculated among the nodes through feedback information to choose a data package front transmission path. According to the data transmission method of the multi-packet feedback opportunistic route based on the ETX value under the Rayleigh channels, a data frame, a feedback frame and a response frame in the opportunistic route are provided, the feedback information of a plurality of packets is placed into the feedback frame to be fed back, and thus the system feedback response expenses are effectively lowered. The data transmission method of the multi-packet feedback opportunistic route based on the ETX value under the Rayleigh channels is applied to data transmission of the multi-packet feedback opportunistic route based on the ETX value under the Rayleigh channels.

The invention discloses a PN code FFT parallel acquisition method in wireless communication techniques. The method includes the steps of generation of a short pseudo code set of a transmitting end, generation of a base band modulating signal, up-conversion processing and signal transmission, generation of a short pseudo code set of a receiving end, signal receiving and down-conversion processing, frequency domain matching and correlation solving, and majority decision. According to the method, a long pseudo code is converted into G short pseudo codes, all the short pseudo codes are connected in a cascading mode to generate the short pseudo code sets, the short pseudo code sets in the same cascading mode are adopted in a receiver at the same time so as to carry out frequency domain matching coherent processing, and then majority decision based on chip delay is carried out; in this way, the method has the advantages that the sensitivity to channel noise is low, accurate channel estimation is not needed during acquisition, acquisition accuracy is high, and the robustness of decision criteria is improved as well due to the adoption of majority decision. A required signal-to-noise ratio in a Rayleigh channel is -13dB or so when the acquisition probability of the method is 95%, and the gain of the signal-to-noise ratio is improved by 12dB or so when compared with the required signal-to-noise ratio of -1dB in background technologies.

The estimate method is to apply to the mobile communication system. Substitute the actual Rely fading factor with the average value of the Rely fading factor to derivate the relationship between the signal-to-noise ratio (S/N) of the channel and the statistic value of the received data. By applying this relationship, the estimated value of the S/N of the channel is obtained. The invention overcomes the disadvantage of the method, which can only be applied on the AWGN channel.