85 results about "Chirp spread spectrum" patented technology

An orthogonal wavelet division multiplexing (OWDM) communication system including a synthesis section and a channel interface. The synthesis section includes a filter pair bank with multiple inputs and an output that provides an OWDM signal. Each input receives a corresponding symbol of a supersymbol, where the symbols are from a selected modulation scheme. The synthesis section generates the OWDM signal as a combination of weighted OWDM pulses, where each weighted OWDM pulse represents of a symbol of the supersymbol. An OWDM Spread Spectrum (OWSS) communication system that uses broad-time and broadband pulses generated from a family of OWDM pulses together with a set of orthogonal PN code vectors. The OWSS pulses are mutually orthogonal and allow multi-user operation. Each user is assigned an OWSS pulse corresponding to a particular PN code. OWSS enables high rate operation for wireless channels with the use of an equalizer with FE and DFE sections.

This invention modulates data onto a radio channel in such a way that the deleterious effects of the channel are reduced. This is accomplished in three steps: first, the information signal is modulated using a phase-differential modulation scheme. Second, the modulated signal is spread in both time and frequency by passing it through a dispersive filter, transmitting it through the channel, and removing the spreading using a dispersive filter in the receiver with the opposite characteristics of the filter in the transmitter. The third step, after demodulation, is to pass the signal through a low-pass filter to gather up the signal energy which has been dispersed by the channel. All three of these steps can be implemented with simple functional blocks, making this system very inexpensive to implement. Also included are two methods for enhancing the data throughput of the basic system, making it more bandwidth efficient.

The invention relates to a non coherent demodulation method, which belongs to the signal processing field, is used in Chirp spread spectrum technology demodulation, can reduce phase shift error, multipath time delay error and Doppler shift effect, and achieves better performance over multipath fading channels and IEEE802.15.4a S-V standard channels. The fundamental principle of the invention is: utilizing a Chirp signal as an impulse function in a proper fractional Fourier domain, i.e. fractional Fourier transformation achieves an excellent focusing ability to the Chirp signal sent by the CCS system. For the advantage of Chirp signal processing in fractional Fourier transformation, the fractional Fourier transformation can be used in CSS spread spectrum technology to demodulate Chirp signals with different modulation frequencies. The demodulation to CCS system is realized by implementing fractional Fourier transformation to the received base band data, and judging the code element by detecting the peak value of the focusing order. The method reduces the demand to frequency synchronization, needs no phase synchronization, and achieves better performance over multipath frequency selectively fading channels.

A wireless communication method in a network comprising one or several beacons and a plurality of end-points, comprising: sending by a beacon a timing message modulated according to a chirp spread spectrum format, receiving said timing message in one or several end-nodes a receiver, detecting said timing message aligning a local frequency reference and/or time reference of the end-node to the time reference of the transmitter by means of said timing message.

A technique for receiving multiple spread spectrum bursts is disclosed. Each spread spectrum burst is encoded with a common spreading code and may include an individual message and unique signal parameters. The technique includes the detection of the spread spectrum encoded bursts and estimation of the reception signal parameters. A single one of a plurality of burst receivers is assigned to each detected burst to extract the individual message of the detected burst.

The invention discloses an ultra-wideband communication method based on Dechirp and slippage correlation, comprising the following steps of: at a transmitting terminal of an ultra-wideband communication system, inserting a pilot sequence in sent data firstly; then, performing base-band modulation and linear frequency modulation and spread spectrum; outputting an ultra-wideband transmission signalat the linear frequency modulation and spread spectrum of an available radio frequency band; at a receiving terminal of the ultra-wideband communication system, firstly by using a slippage correlation method, completing synchronization of a received signal through adjusting the time delay of an ultra-wideband reference signal of the linear frequency modulation and spread spectrum; then, mixing the ultra-wideband reference signal of the linear frequency modulation and spread spectrum with the received signal, namely, performing Dechirp process; and finally, after filtering in low pass, demodulating the base band of the received signal. According to the ultra-wideband communication method, the sampling rate and the signal processing scale of the receiving terminal can be reduced; the synchronization precision requirements are not high; the complexity is very low; and the method is especially applicable for ultra-wideband expand distance low-speed communication with high spread spectrum gain.

The invention provides an asynchronous ad-hoc network positioning system and an asynchronous ad-hoc network positioning method based on bidirectional precise distance measurement, and belongs to the field of wireless communication positioning. The positioning system provided by the invention is composed of a data processing center and a plurality of node terminals, wherein the node terminals have the completely same structure and functions, and each node terminal is composed of a distance measurement module, a routing module, a power supply module and a logic control module. The system integrates a chirp spread spectrum (CSS) distance measurement technology with a ZigBee ad-hoc network technology, and achieves autonomous access and positioning of the new node based on a minimal hop principle. The system is low in cost, small in power consumption, short in positioning time and wide in applicability, and particularly can solve the problem of high precision positioning of groups under hostile geographical environment.

The present invention uses discrete multicarrier spread spectrum, direct sequential spread spectrum and inverse dicrete Fourier transformation to form a two-dimensional spread spectrum module, and the two-dimensional spread spectrum module, frequency hopping and time hopping spread spectrum are used to form the emission part of the united extending spectrum communication method. The inverse discrete multicarrier, direct sequential despreading spectrum and discrete Fourier transformation are used to form a two-dimensional despreading spectrum module and two-dimensional despreading spectrum module, time dehopping and frequency dehopping unit are used to form the receiving part of the united extending spectrum communication method.

The invention discloses a CSS (chirp spread spectrum) distance measurement-based wireless sensor network distributed node positioning method. The method comprises the following steps: using a distance vector exchange protocol to enable information interaction to be carried out between anchor nodes and unknown nodes in a wireless sensor network so as to enable the nodes to be located to obtain identities (IDs) and position coordinates of the anchor nodes within the 1-jump range; simultaneously establishing a corresponding anchor node information table; inquiring the anchor node information table of the nodes to be located; when the number of the anchor nodes within the 1-jump range is more than or equal to 3, acquiring the positions of the nodes to be located by a CSS distance measurement-based trilateral localization algorithm; upgrading the nodes acquiring the self positions to be the anchor nodes, and broadcasting the information of the self IDs and position coordinates of the updated anchor nodes to the surrounding neighbors in a broadcasting way; recording the information of the IDs and the position coordinates of the updated anchor nodes into the self anchor node information tables by the neighbor nodes to be located to realize the self node location.

The invention relates to multiservice mixed transmission method and system based on a multi-adjusting frequency chirp spread spectrum (CSS). The multiservice mixed transmission method based on a multi-adjusting frequency CSS comprises the steps of baseband modulation, CSS, fractional Fourier transform, transform domain filter, inverse frequency sweeping and demodulation. The multiservice mixed transmission method and system based on a multi-adjusting frequency CSS carry out multiservice mixed transmission by adopting multi-adjusting frequency CSS and can realize recognition and separation of a multiservice mode at a physical layer and simplify an upper scheduling algorithm; and the difference of different services is embodied at the physical layer, particularly, the transmission quality of different services can be flexibly adjusted by controlling parameters. The complex problem of multiservice mixture is simplified into the interference suppression problem between transform domain transmission multiplexing/multiaddress of a single service and the service, and different service signs are allowed to be asynchronously innitiated without demanding a strict time sequence relation.

A radio receiver for processing digital chirp spread-spectrum modulated signals that comprise a plurality of frequency chirps that are cyclically time-shifted replicas of a base chirp profile, said time-shifts being an encoded representation of a transmitted message. Includes a soft demapping unit that is adapted for working on fully populated as well as on partial modulation sets, and implements a timing error correction loop that acts back both in the time domain and in the frequency domain.

The invention discloses a wireless-network-based mobile node combined positioning method. The wireless-network-based mobile node combined positioning method comprises the following steps: performing CSS (chirp spread spectrum) ranging, thereby obtaining a ranging sample; calculating a sample mean (which is specified in the original PDF); step 2, by utilizing the sample mean obtained in step 1, performing non-line-of-sight judgment, thereby obtaining a visible state of a mobile node at time t; step 3, establishing a motion model of the mobile node and calculating a position of the mobile node at time t+1; step 4, performing combined positioning on the mobile node. According to the wireless-network-based mobile node combined positioning method, by designing a non-line-of-sight detection algorithm based on the Markov mode, non-line-of-sight state detection is achieved to eliminate influence of non-line-of-sight error on positioning; meanwhile, a KF-based combined positioning method is provided to achieve the combination of CSS positioning and inertial sensor positioning; therefore, a high-precision and low-complexity combined positioning method is achieved.

The invention relates to a method for achieving deep spread spectrum and coherent fast frequency hopping based on DAGC diversity combining, and belongs to the technical field of interference resistance in spread spectrum digital communication. According to the method, through a coherent digital AGC diversity combining algorithm, for an anti-interference communication system with the deep spread spectrum and the coherent fast frequency hopping combined, the influence on other diversity by interference diversity signals in the coherent combining process is lowered, the signal-to-noise ratio of demodulation signals is improved, and the anti-interference capacity of the system is enhanced.

The invention discloses a TDOA-based CSS (chirp spread spectrum) precise positioning method. According to the method, a base station model with different mobile station-co-base station virtual receivers is adopted; all the virtual receivers, namely, base station antennas, adopt the same clock, and therefore, requirements for clock synchronization can be eliminated from the source; when distance measurement is performed on a node to be positioned, namely, a mobile terminal, obtained distance measuring values between the node to be positioned and reference nodes are processed through adopting a voting and average combined filtering algorithm, and errors caused by environment are removed, and dynamic correction is performed on left distance measuring values through using a dynamic error correction algorithm, and therefore, distance measuring errors can be decreased to the greatest extent; the corrected distance measuring values are averaged, so that an average value can be obtained; the obtained average value is processed through using a TDOA three-dimensional localization algorithm, so that the position coordinates of the node to be positioned can be obtained, and therefore, final precise positioning can be realized.

The spread spectrum receiver employs circuits based on direct conversion techniques. These circuits enable realization of spread spectrum receivers of greatly reduced complexity and of much higher chip rates that can be implemented with the standard approach of a fully digital receiver. With these circuits, the digital processing is performed at the data symbol rate and not at a multiple of the chip rate that is customary in state-of-the art spread spectrum and CDMA receiver design.

The invention relates to a chirp spread spectrum modulation and demodulation method based on QPSK (Quadrature Phase Shift Keying). The method comprises the following steps: S1, generating a chirp signal with a fixed length according to parameter configuration; S2, combining the chirp signal into a frame header signal according to a certain format; S3, converting an original sending signal to be sent into a QPSK signal, and then multiplying the QPSK signal by an upchirp signal to generate a modulation signal; S4, combining the frame header signal with the modulation signal to generate completedata information, and transmitting the data information through the radio frequency transmitting module; S5, converting the data information into a baseband signal; S6, converting the baseband into adispreading signal; S7, converting a despread signal into demodulation data; S8, de-interleaving, de-whitening and decoding the demodulated data, and recovering the demodulated data into an original sending signal. The demodulation algorithm is simple and easy to implement, and signal synchronization is easy to process.

The invention provides a Chirp spread spectrum communication receiver time synchronization system and method. A signal-to-noise ratio enhancement module of the system is used for modulus operation conducting, gain acquiring, delaying and combining, wherein phase differences among symbols are eliminated by means of the modular operation, and useful signals are enhanced by means of gain acquiring; acombined spread spectrum modulation module conducts spread spectrum modulation with a combined Chirp signal; and after a signal obtained after combined spread spectrum modulation, matched filtering receiving and signal-to-noise ratio enhancement is acquired, peak searching of a narrow-band pulse obtained after matched filtering is narrowed within a symbol period by means of a noise threshold setin a judgment module, and a peak searching module captures the moment when a peak is obtained in the symbol period to achieve time synchronization. According to the system and method, by adding the judgment module in a synchronization module, error synchronization moment judgment brought when actual synchronization and ideal synchronization have a difference of integer multiples of the symbol period is solved, and the timing precision is improved; and meanwhile, the complexity of an algorithm is reduced due to narrowing of the synchronization moment searching range.

The invention discloses a seamless indoor and outdoor positioning system and positioning method based on combination a chirp spread spectrum (CSS) with a GPS. The positioning system is composed of an outdoor GPS satellite module, an indoor CSS positioning module, an indoor and outdoor positioning fusion switching module and a positioning result display module. The outdoor satellite positioning module utilizes a GPS satellite for navigation. The indoor CSS positioning module carries out an indoor distance measurement process by using a symmetrical double-sided two-way ranging (SDS-TWR) method, carries out optimization processing on positioning ranging data by using Kalman filtering, and then obtains an indoor position of the indoor positioning module by using a geometric trilateral positioning algorithm. The indoor and outdoor positioning fusion switching module carries out fusion, switching and integration on indoor and outdoor positioning methods based on indoor and outdoor positioning communication signal strength, thereby realizing smooth indoor and outdoor positioning result transition; and the positioning result display module displays a positioning result based on an outdoor two-dimensional electronic map and an indoor planar graph. Compared with the existing positioning system, the provided positioning system enables seamless connection of precise indoor and outdoor positioning to be realized based on combination a CSS technology with a GPS satellite navigation technology.

The invention provides a mobile underwater acoustic communication Doppler coefficient estimation method based on chirp signals. Suitable chirp signals are selected as modulation signals. Modulation is carried out through adoption of a CSSBOK (Chirp Spread Spectrum Binary orthogonal keyed) modulation mode. The variable quantity of an actual chirp signal length is obtained by employing the variable quantity of the sampling point quantity of the chirp signals before and after the Doppler effect is generated. Therefore, a Doppler coefficient is estimated. According to the mobile underwater acoustic communication Doppler coefficient estimation method based on the chirp signals provided by the invention, the method is simple and easy to carry out; the calculation quantity is low; the estimation precision is high; the Doppler coefficient of each code element can be estimated precisely; and the signals can be demodulated accurately.