131 results about "Shadow fading" patented technology

The present invention is directed to wireless communication, and more particularly, to providing improved signal quality using antenna beam selection and/or switching techniques. Embodiments of the present invention may measure the carrier-to-interference (C/I) level for each channel and for each antenna. Embodiments of the present invention assign forward-link signals to antennas such that only one forward-link signal is transmitted from a respective antenna. Moreover, embodiments prioritize assignment to antennas by the forward-link power, i.e., the forward-link signal associated with the highest power is transmitted from the antenna associated with the best channel quality metric for reverse-link of the respective channel. Additionally, embodiments may employ the assignment scheme with antennas that possess spatial, polarization, and/or directional diversity to minimize the effects of shadow fading.

The invention discloses an indoor passive target positioning method based on received signal strength, and belongs to the technical field of target detection and tracking in a wireless network. Considering the situation that a link is blocked by a target, the method is mainly applied to detection of links with a shadow fading phenomenon before positioning. The method comprises the steps of node arrangement, measurement of change values of the received signal strength of all the links when a monitored area is free of targets and a target enters the monitored area, time domain detection for excluding some mutant links without the shadow fading phenomenon, space domain detection for excluding the links with the shadow fading phenomenon far away from the actual position of the target, and estimation of the position of the target according to the links with the shadow fading phenomenon. The indoor passive target positioning method based on received signal strength is easy and flexible to implement; moreover, in combination with a time domain and space domain detection method, the influence of the links without the shadow fading phenomenon is effectively eliminated, the attenuation effect brought by the target is highlighted more accurately, so that indoor target positioning is more accurate, and better dynamic tracking is realized.

The invention discloses a satellite signal simulator and a satellite signal simulation method. The satellite signal simulator comprises a channel parameter generation unit used for calculating channel feature parameters according to satellite channel model parameters, communication frequency points, orbit parameters, terminal parameters and environment parameters; a radio frequency input unit used for converting intermediate-frequency signals of a satellite down to baseband signals; a channel simulation unit used for, according to the channel feature parameters, respectively performing Doppler frequency shift, multipath shadow fading, additive white noise and amplification filtering processing on the baseband signals; and a radio frequency output unit used for converting the signals output by the channel simulation unit into radio frequency signals for output. According to the invention, the simulated channel model types are enabled to be more diversified, the operation is convenient and visual, and the work accuracy and the data reliability of the satellite signal simulator are improved.

The invention relates to a multi-path shadow compound fading channel simulation device and a work method thereof. First, a universal compound fading mathematical model is provided based on the comprehensive consideration of the compound influence of path losses, shadow fading and multi-path fading. Then, the multi-path fading, the shadow fading and channel noise in the model are decomposed into a Gaussian random process expression form and generated by an SoS (Second-Order Section) fixed-point model in a unified simulation way. The simulation method conforms to FPGA-based (Field Programmable Gate Array) fixed-point operation characteristics and is easy to realize. The simultaneous simulation of an uplink and a downlink is supported by a simulation system. Two input interfaces are available for selection, and radio frequency simulation signals or intermediate frequency simulation signals are input through the input interfaces. Parameters about communication scenes and the like are input by a user through a PC (Personal Computer), the feature parameters of the compound fading channel under the scenes are calculated by a DSP (Digital Signal Processor) in real time, and the feature parameters are utilized by the FPGA to carry out hardware simulation. Output simulation signals passing a wireless channel also comprise intermediate frequency signals and radio simulation signals. The multi-path shadow compound fading channel simulation device and the work method thereof are used in land-land mobile communication scenes, and can also be used in air-land (land-air) and air-air communication fading channel scenes.

The invention discloses an orthogonal space-time pre-coding transmission method which is based on a distributed antenna system. According to the characteristics of a distributed multiple-input multiple-output channel, two restricted designed quantization sub-code books are stored at the two ends of transmitter and receiver. A moving end predicts a channel state message when a base station transmits signals according to an obtained channel estimated value. Based on the channel predicted values and according to the pairing error probability rule of the minimized orthogonal space-time pre-coding, the moving end chooses an optimal quantization codeword for fast fading and shadow fading respectively, and then feeds back the serial number of the two code words to the base station. After receiving the feedback message, the base station restores a corresponding quantization code word which creates a pre-coding direction matrix with the existing path loss message, and at the same time, the base station calculates a corresponding power distribution factor according to a mixed power distribution method, thus further improving the reliability of the transmission. The invention provides a simple and effective pre-coding transmission method for the distributed antenna system.

The invention relates to a 3D MIMO channel modeling method. The method includes the following steps that: (1) simulated scenes and network layout are determined, large-scale parameters are calculated according to the scenes and calculated correlations; (2) small-scale parameters are generated sequentially based on the large-scale parameters, a probability density function and the scenes; (3) a channel coefficient is calculated; (4) the small-scale parameters are updated according to a calculation result, and a drift model is built; and (5) time evolution is carried out according to the drift model, and then, modeling is carried out. According to the 3D MIMO channel modeling method of the invention, short-term time evolution of the channel coefficient is realized through updating time delay, a departure angle, an arrival angle, polarization, shadow fading and a K factor; smooth transition between adjacent channel segments is supported; a visual-range scene and a non-visual-range scene are simulated jointly by a common framework structure, and therefore, the complexity of a model can be reduced, and multi-unit scenes can be configured freely; and an algorithm of position graph generation is expanded, and diagonal angle movement directions are considered, and smoother output is created.

This invention provides a dual-path static baseband channel simulating device and method, which are applicable to a variety of communication scenarios. A channel model of each channel is selected by a user, and channel parameters are set and calculated; the channel parameters are subjected to fixed-point processing by a DSP (Digital Signal Processor), and the fixed-point parameters are transmitted into an FPGA (Field Programmable Gate Array) through an EMIF; multipath fading, shadow fading and Gaussian noise are superposed on the dual-path digital baseband signals collected by an AD in the FPGA, wherein the type of the multipath fading includes constant fading, pure Doppler fading, Rayleigh fading, Rician fading and the like; the shadow fading follows lognormal distribution; at last, an analog signal is output by a DA, and signal conditioning is performed on the analog signal, wherein the signal conditioning mainly comprises eliminating mirror components of the signal and controlling signal attenuation. The channel simulating device and method provided by the invention have the advantages of being various in fading types, simple in operation and the like.

The invention relates to an adaptive modulation (AM) method design and performance evaluation for a wireless distributed multi-antenna system (DAS). Under the constraint condition of a target bit error rate (BER), the system frequency spectrum efficiency is maximized to respectively design two AM schemes of a discrete rate and a continuous rate. By aiming at the discrete rate AM, an adaptive switching threshold based on precise BER is provided. Compared with the traditional AM based on an approximate threshold, the AM method disclosed by the invention can obtain high frequency spectrum efficiency. A channel model comprising path loss, shadow fading and Rayleigh fading is designed by considering the practical situation of DAS. On the basis, the computation expression of a continuous rate AM frequency spectrum efficiency, a discrete rate AM frequency spectrum efficiency and the average BER is given so as to provide an effective method for system performance evaluation. An Matlab (matrix laboratory) simulation platform shows that the designed AM method can satisfy the target BER requirement, and the continuous rate AM method is better than a discrete rate AM method. In addition, due to the providing of an improved threshold, the discrete rate AM can be used for realizing the high frequency spectrum efficiency if being compared with the traditional AM method. In addition, the provided frequency spectrum efficiency has good consistency with the average BER calculation and simulation, and the system performance can be effectively evaluated.

The present invention discloses an ultra-wideband node network-based device-free localization method, belonging to the field of wireless localization technologies in a wireless network. According to the method, an ultra-wideband signal is sent by using a node so as to realize device-free localization (DFL), a channel pulse response in a line of sight (LOS) is detected, and localization is performed by using change of an LOS path signal power. In addition, the ultra-wideband node has a precise distance measurement capability, and can achieve precise node self-localization. Node self-localization is achieved by using distance measurement provided by the ultra-wideband node according to a cooperation localization method, shadow fading caused by shielding by a target is obvious, and an imaging effect is further improved, so that the method is more applicable to an environment with low LOS power, can improve localization precision in a more complex environment, and greatly reduces manpower and time cost for node deployment.

The invention discloses a closed-loop power control correction method based on an LET-A system. The method comprises a step of calculating a distance between a user and a base station and estimating path loss, shadow fading and dependent gain of an antenna; a step of determining a correlated path loss compensation factor [alpha] according to the path loss; a step of counting the reception power RSRP of reference signals of all user equipment (UE) in a district according to a common reference signal sent by the base station and the path loss; a step of dividing the district into three areas, wherein when the UE is positioned in a superior area, the emission power is continuously increased on the basis of an original emission power; when the UE is positioned in a middle area, proper compensation is performed for the path loss as the path loss is increasing, i.e., the emission power is gradually increased with the increase in the path loss; and the UE is positioned in a fringe area, the emission power is reduced on the basis of a closed-loop power; and a step of re-sending a TPC command according to a correction factor, and selecting the emission power according to the area where the UE is. The closed-loop power control correction method provided by the invention considers three factors of district average throughout, a fringe user throughout and interference of adjacent districts.

The invention discloses an indoor radio tomography imaging enhancement method capable of deleting an interfering link based on motion prediction, and belongs to the technical fields of target detecting and tracking in a radio network. The method comprises the following steps of finding out an intersection set formed by shadow fading links by virtue of clusters; taking the center of the set as estimation of a target position at an initial moment, and utilizing a target motion model and the positioning result of the last moment to obtain estimation of the target position at the current moment through Kalman filtering, so as to delete the interfering link which is relatively far away from the target position; finally carrying out RTI (radio tomography imaging) through the shadow fading links, and obtaining the current moment position by using Kalman updating on the basis of the RTI. The effects of non-shade fading links are eliminated based on the motion prediction; false targets can be effectively removed; the fading effect caused by presence of the target is relatively accurately highlighted, thus target positioning is relatively accurate in a multipath environment; the imaging quality is improved; relatively excellent dynamic tracking is achieved.

The invention discloses a method and a mobile communication network for adjusting the transmission power of a mobile station. The method comprises the following steps that: each base station respectively measures uplink performance indexes of the base station and transmits the measure values of the uplink performance indexes of the base station to adjacent base stations through a backbone network; each base station respectively adjusts partial power control factors of the base station according to the received uplink performance indexes of the adjacent base stations and transmits the adjusted partial power control factors to each mobile station under the control of the base station through broadcast messages; and each mobile station respectively adjusts the transmission power of the mobile station according to the partial power control factors. The method adjusts the transmission power of the mobile station through partial power control technology, can reduce the disturbance of an uplink, further improve the performance of cell edge users, and greatly improve the throughput of a system sector particularly in a honeycomb wireless communication system of low-frequency multiplex factors. The optimized proposal performs compensation on the path loss and the shadow fading.

The invention relates to a dynamic spectrum distribution method based on covering frequency in a heterogeneous wireless network. The method is characterized by comprising total frequency spectrum benefit maximization and interference control, wherein the interference control is based on a coverage probability threshold, and the interference control model is p[n,m](A)>=beta n (1); and based on the interference control model, modeling of a covering frequency based dynamic spectrum distribution algorithm (CP-DSA) is defined in the description in the interference control model based on coverage probability, user signal interference noise ratio and base station coverage performance requirement are considered at the same time, starting from the purpose of ensuring the base station coverage probability requirement, to achieve the purpose of ensuring user service quality requirement in a cell; and by adopting the dynamic spectrum allocation algorithm CP-DSA based on covering frequency, the total frequency spectrum benefit can be improved, interference between base stations is effectively controlled, and under the condition of an actual shadow fading channel, the user SIR (signal interference noise ratio) requirement is met.

The invention discloses a shadow fading assistance carry-free equipment positioning method, and belongs to the technical field of wireless positioning in a wireless network. Wire nodes surrounding a monitoring region build a fingerprint database in an offline stage through the RSS (received signal strength) change of a measuring object in each training position; in the online stage, the shadow fading link detection is firstly performed; then, the positioning algorithm is selected according to different conditions of the shadow fading region intersection set. When an objective does not detect the shadow link in the position, a conventional fingerprint recognition method is still used; when the shadow fading link exists, the mode matching is only performed in a shadow fading region; when the shadow fading links are many, for example, the objective is positioned in the center of the monitoring region, the center of the intersection region is taken to be used as the objective position estimation. The method has the advantages that the shadow fading and the fingerprint recognition are combined; the shadow fading link is effectively utilized for assisting the fingerprint recognition, so that the target positioning is more precise.

The invention discloses a large-scale fading factor calculation system for a wireless channel. The system comprises a model establishment module, an initialization module, a spherical reflection coefficient calculation module, a path loss calculation module, a shadow fading calculation module and a result output module, wherein the model establishment module is used for establishing a two-path spherical reflection model; the initialization module is used for initializing antenna characteristics and earth surface characteristics; the spherical reflection coefficient calculation module is used for calculating a spherical reflection coefficient caused by a spherical curvature during the far-field flight of an unmanned aerial vehicle; the path loss calculation module is used for calculating electromagnetic wave loss, caused by the increment of roughness of the surface of the earth, of electromagnetic waves of reflection paths; the shadow fading calculation module is used for calculating shadow fading, caused by the blockage of a building, of the electromagnetic waves in an actual propagation environment; the result output module is used for determining an overall large-scale fading factor. The invention also provides a large-scale fading factor calculation method for the wireless channel. According to the large-scale fading factor calculation system and the large-scale fading factor calculation method for the wireless channel, the requirements of communication modeling and system evaluation are met.

Efficient spectrum sensing is implemented taking into account the fading caused by multipath fading and shadow fading in a mobile environment. A cooperative spectrum sensing method performed by a plurality of in-vehicle wireless communication devices, includes: a decorrelation time acquisition step for acquiring a first decorrelation time, which is a time interval in which channel fluctuations resulting from multipath fading are decorrelated, and a second decorrelation time, which is a time interval in which channel fluctuations resulting from shadow fading are decorrelated; a sensing step for repeatedly performing sensing at a time interval equal to or longer than the first decorrelation time; a notification step for wireless transmitting a plurality of most recent sensing results at a time interval equal to or longer than the second decorrelation time; and a determination step for determining a state of a channel on the basis of the plurality of sensing results transmitted from the plurality of in-vehicle wireless communication devices.

The invention provides a wireless body area network communication system interruption probability analyzing method based on a k-mu shadow fading channel. The method includes the steps of firstly establishing a system model, sequentially calculating the conditional probability density function, the unconditional probability density function and the generalized nonholonomic moment generating function of the signal-interference ratio of a receiver end, and finally calculating the interruption probability of the wireless body area network communication system under the co-channel interference condition. The method effectively solves the technical problem of lack of means for accurately analyzing the interruption probability properties of a wireless body area network communication system, and takes the influence of co-channel interference and additive white Gaussian noise on the system performance into consideration. An enclosed interruption probability expression is obtained by analyzing the statistical characteristics of the signal-interference noise ratio (SINR) of the receiving end, thereby providing theoretical foundation and basis for evaluating the influence of channel fading characteristics and co-channel interference on the wireless body area network communication system.

The invention discloses a node collaboration based Sybil attack detection method in a power controllable WSN (Wireless Sensor Network) and belongs to the network security technical field. The node collaboration based Sybil attack detection method comprises facing the real network environment which comprises the path loss and shadow fading and is a large scale propagation model to analyze a secondary difference value of an RSSI (Received Signal Strength Indicator) and providing a Sybil node identification algorithm according to the characteristic that the secondary difference value of the RSSI is not affected by changes of the node transmission power, wherein the Sybil node identification algorithm distinguishes whether two nodes are two Sybil identities which are forged through a malicious node or not through the mutual collaboration of public monitoring nodes of the two ordinary nodes. According to the node collaboration based Sybil attack detection method, the characteristics of the secondary difference value of the RSSI and the monitoring node cooperation scheme are combined and accordingly the detection efficiency of Sybil attacks in the power controllable WSN is improved and the network life cycle can be extended.

The invention provides a channel associated shadow fading construction method based on a stationary random process, relating to the field of wireless communication. A time varying channel associated shadow fading model construction method base on a stationary random process comprises a step 101 of segmenting a time-varying channel into a plurality of stationary intervals according to an actual transmission environment, a step 102 of determining the mean value and root-mean-square of the shadow fading in each stationary interval, and a step 103 of simulating the shadow fading with correlation in the stationary interval according to the stationary random process time varying channel associated shadow fading model.

The invention discloses a method for simulating propagation characteristics of a fading channel in a coupled multi-antenna indoor space. The method comprises the following steps: (1) generating an lthcluster transmitting angle and an lth cluster receiving angle which are randomly distributed; (2) generating a transmitting deviation angle and a receiving deviation angle conforming to the k sub-path in the l cluster of the transmitting end and the receiving end which are in Laplace distribution; Generating an emission angle of an lth cluster and a kth sub-path of the transmittingend; (3) generating an arrival angle of the k subpath in the l cluster of the receiving end; (4) generating the amplitude of each sub-path conforming to Rayleigh distribution; Generatinga phase of each sub-path obeying [0, 2] uniform distribution; (5) generating logarithmic normal shadow fading numerical random variables; (6) generating a guide vector of each antenna by combining the antenna layout; And (7) generating a channel transmission matrix of the whole tight coupling MIMO system. According to the method, the influence of large-scale shadow fading and the array element electromagnetic coupling effect in an indoor propagation environment is fully considered, and the channel characteristics of the indoor MIMO multi-antenna transmission system are accurately simulated and evaluated.

The invention relates to an electromagnetic spectrum map construction method and device, computer equipment and a storage medium. The method comprises the following steps: acquiring monitoring data and a to-be-estimated point position, and acquiring path attenuation component estimation by using a trend surface fitting algorithm; subtracting the monitoring data from the path attenuation component estimation value of the corresponding position, performing position clustering on the obtained residual monitoring data, and estimating a clustering result in an optimal neighborhood by adopting a Kriging method to obtain shadow fading component estimation; and obtaining an estimation result according to the path attenuation component and the shadow fading component. Electromagnetic spectrum map construction is decomposed into estimation of path attenuation and shadow fading components, so that the electromagnetic spectrum map construction precision is effectively improved; through monitoring data clustering and optimal neighborhood selection, the calculated amount is reduced under the condition of ensuring the construction precision, and the electromagnetic spectrum map construction speed is effectively improved; and the method does not need prior information such as a radiation source and a propagation model, and has good adaptability.

The invention relates to an optimal bit error rate estimation method which comprehensively considers multiple energy consumption influencing factors, according to different indoor environment, combined the influence of indoor distance, walls, number of floors, indoor obstacles on the obstruction and reflection of wireless sensor networks, the influence of shadow fading caused by the obstruction and reflection of wireless sensor networks is analyzed, and the energy loss model of the path distance of wireless sensor networks in the face of indoor obstacles is analyzed and derived with consideration of the impact of multiple impact factors in the reality of indoor communication on the transmission quality of wireless sensor networks. Meanwhile, with guaranteed transmission quality, combined with the influence factors of energy consumption caused by frame retransmission due to BER, the energy loss model of frame retransmission in wireless sensor network considering indoor obstruction shadow fading is analyzed and deduced, and the optimal BER is found to optimize the energy consumption model of the whole network, and then the path optimization of signal transmission is realized.

The invention provides a modeling simulation method and system for a satellite time-varying channel. A rain attenuation module and a Loo module are combined to serve as transfer states of markov to simulate a time-varying satellite channel simulation system considering weather state changes. A sunny module and a cloudy module adopt Loo models, and realize the simulation of sunny days and cloudy days by adjusting the receiving power obeying Rayleigh distribution of the Doppler frequency spectrum and the Lognormal distribution obeying the Doppler frequency spectrum according to the specific conditions of the sunny module and the cloudy module. During rain attenuation modeling, statistical parameters of a random process are fitted through long-term rain attenuation data obtained through calculation of an ITU-R model and substituted into the logarithm Gaussian distribution model, so that a time-varying sequence of rain attenuation values is obtained. Because the ITU-R model can calculate the rain attenuation value of the working frequency band below 55Ghz, the system is wide in simulatable frequency range. According to the method, factors such as multipath time delay, Doppler frequencyoffset and shadow fading in the transmission process are considered, and the transmission characteristics of the satellite mobile communication channel in different weather states are accurately described.

The invention discloses a method and a device of power control, and relates to the technical field of wireless communication. The method and the device of power control are used for improving power control performance. The standard deviation value of strength of received signals is confirmed according to the signal strength value of the received signals, the standard deviation value is the statistical average value of the difference value of the strength of the received signals and the average value of the strength of the received value, compensation is carried out on signal sending power according to the standard deviation value, therefore compensation is carried out on shadow fading in open loop power control, the defect that closed loop power control cannot track shadow fading of an information channel in time when propagation time delay is large is overcome, and accordingly power control performance is improved.