49 results about "Walsh sequences" patented technology

The present invention provides a method and system for reducing the peak to average power ratio (PAP) of a signal with low computational complexity. According to one embodiment, the present invention is applied to reduce the PAP of an OFDM signal. According to an alternative embodiment, the present invention, is applied to reduce the PAP of a CDMA signal. Rather than seeking the optimum solution, which involves significant computational complexity, the present invention provides for a number of sub-optimal techniques for reducing the PAP of an OFDM signal but with much lower computational complexity. In particular, according to one embodiment utilizing the PTS approach, an iterative technique is used to assign phase factors to each of a set of partial transmit sequences from a set of possible phase factors. Experimental results using the iterative technique showed only a slight degradation (1 dB) from the optimal approach using the same number of subblocks and subcarriers. In an alternative embodiment, which avoids feedback required by the iterative approach, a sequence of phase factors are generated randomly and assigned to each of a set of partial transmit sequences. This procedure is repeated for a pre-determined number of trials and the random sequence generating the lowest PAP is selected. In a third embodiment, a set of phase factors is generated using a structured sequence such as a Walsh sequence.

It is possible to improve the CQI reception performance even when a delay is caused in a propagation path, a transmission timing error is caused, or a residual interference is generated between cyclic shift amounts of different ZC sequences. For the second symbol and the sixth symbol of the ACK / NACK signal which are multiplexed by RS of CQI, (+, +) or (−, −) is applied to a partial sequence of the Walsh sequence. For RS of CQI transmitted from a mobile station, + is added as an RS phase of the second symbol and − is added as an RS phase of the sixth symbol. A base station (100) receives multiplexed signals of ACK / NACK signals and CQI signals transmitted from a plurality of mobile stations. An RS synthesis unit (119) performs synthesis by aligning the RS phase of CQI.

A terminal apparatus is disclosed wherein even in a case of applying SU-MIMO and MU-MIMO at the same time, the inter-sequence interference in a plurality of pilot signals used by the same terminal can be suppressed to a low value, while the inter-sequence interference in pilot signal between terminals can be reduced. In this terminal apparatus (200): a pilot information deciding unit (204) decides, based on allocation control information, Walsh sequences of the respective ones of first and second stream groups at least one of which includes a plurality of streams; and a pilot signal generating unit (205) forms a transport signal by using the decided Walsh sequences to spread the streams included in the first and second stream groups. During this, Walsh sequences orthogonal to each other are established in the first and second stream groups, and users are allocated on a stream group-by-stream group basis.

The present invention provides a method and system for reducing the peak to average power ratio (PAP) of a signal with low computational complexity. According to one embodiment, the present invention is applied to reduce the PAP of an OFDM signal. According to an alternative embodiment, the present invention is applied to reduce the PAP of a CDMA signal. Rather than seeking the optimum solution, which involves significant computational complexity, the present invention provides for a number of sub-optimal techniques for reducing the PAP of an OFDM signal but with much lower computational complexity. In particular, according to one embodiment utilizing the PTS approach, an iterative technique is used to assign phase factors to each of a set of partial transmit sequences from a set of possible phase factors. Experimental results using the iterative technique showed only a slight degradation (1 dB) from the optimal approach using the same number of subblocks and subcarriers. In an alternative embodiment, which avoids feedback required by the iterative approach, a sequence of phase factors are generated randomly and assigned to each of a set of partial transmit sequences. This procedure is repeated for a predetermined number of trials and the random sequence generating the lowest PAP is selected. In a third embodiment, a set of phase factors is generated using a structured sequence such as a Walsh sequence.

The invention discloses a multivariate orthogonal chaos shift keying modulation / demodulation method. According to the method, Hilbert orthogonal transformation and orthogonal Walsh sequence weighting are carried out chaos signals to construct a plurality of mutually- orthogonal chaos carrier signals; and the modulation / demodulation is carried out by utilizing a multivariate orthogonal modulation method. According to the multivariate orthogonal chaos shift keying modulation / demodulation method, the delay units in the existing binary / N-nary DCSK receivers are eliminated, the delay units in transmitters are decreased, the realizing complexity is reduced, the bit transmission speed of the system is greatly improved and the bit error rate performance of the system is enhanced to a relatively great extent.

A method for deep paging in a communication system employing orthogonal channelizing codes, such as Walsh sequences, of predetermined length m, that does not require a high powered paging channel. The method includes the steps of generating a paging channel message which is combined with a Walsh sequence having a length greater than or equal to 2m, and transmitting the paging channel message at a data rate of less than 4800 bits per second (bps). By transmitting the paging channel message at a low data rate and integrating collected energy over a period longer by a factor on the order of 1000, the message is able to penetrate buildings and other structures or high attenuation environments, thereby allowing one to successfully page a user terminal that is inside such a structure or area. Preferably, the paging channel message is formed using an auxiliary Walsh sequence on the order of 65536 chips in length, and the data rate is less than 10 bps.

Provided is a radio communication device which can surely prevent inter-code interference while maintaining the use efficiency of an upstream line control channel and suppress separation characteristic of a response signal. The device includes: a control unit (209) which controls a cyclic shift amount of a ZC sequence used for a primary diffusion in a diffusion unit (214) and a Walsh sequence used for secondary diffusion in a diffusion unit (217) according to a PUCCH number inputted from a judgment unit (208); the diffusion unit (214) which performs primary diffusion of the response signal by the ZC sequence set by the control unit (209); and the diffusion unit (217) which performs secondary diffusion of the response signal by the Walsh sequence set by the control unit (209). The diffusion unit (214) performs primary diffusion of the response signal by using the ZC sequence having such a cyclic shift amount that the guard interval at the both ends of the detection window section is maximum in the ZC sequences having different cyclic shift amounts.

The invention relates to an MC-CDMA-based underwater acoustic communication system and a PAPR suppression method, and the method comprises the steps: enabling a transmitting end to code input data after mapping, carrying out the serial-parallel conversion of the input data into q sub-data streams bi, and copying the bit of each sub-data stream bi into Np parts; generating a chaotic sequence according to the number U of subcarriers, and circularly multiplying the chaotic sequence by the basic spread spectrum sequence to generate a chaotic composite spread spectrum sequence C; multiplying each sub-data stream bi by the chaotic composite spread spectrum sequence C, and converting the multiplied sub-data streams bi into time domain signals through IFFT; and calculating the peak-to-average power ratio PAPR of the system according to the frequency band signal after up-conversion sampling. According to the PAPR suppression method disclosed by the invention, by changing the generation mode ofthe spreading code, the chaotic sequence is cyclically multiplied by basic spreading sequences such as an M sequence, a Walsh sequence or a completely complementary CCS sequence to generate a chaoticcomposite spreading sequence, so that the peak-to-average power ratio suppression characteristic of the system is improved. Compared with an amplitude limiting method, the method does not cause in-band distortion and out-of-band leakage. Compared with a probability method, the method is simple in operation mode and low in operation complexity.

Before carrying out equalization processing for data stream, the receiving end of the transmission system carries out recognition for transmission mode. The method includes steps: (1) when received data stream reaches system information bit in data frame, the input data starting multiplication to random sequence data in n bits one by one; mode for creating random sequence data in n bits is identical to mode for creating random sequence in system information generation procedure to carry out randomization process for Walsh sequence blocks; (2) after n pieces of symbol are transmitted, Walsh transform is carried out for multiplied result of n bits corresponding to these symbols; (3) fetching one maximal absolute value from n pieces of outputs after Walsh transform; based on definition of mode word in system information in time of transmission, finding out corresponding system information; then, finding out transmission mode of data frame matched to the system information.

The present invention is a novel and improved method and apparatus for transmitting data in a multiple carrier CDMA communication system. In the first implementation of the present invention, the data is encoded and the resulting encoded symbols are divided up and transmitted on different frequencies. The encoded symbols are provided to a symbol repetition means which keeps the symbol rate of data to be transmitted fixed. In a second embodiment, no symbol repetition is provided and variable length Walsh sequences are used to handle data rate variations.

In an apparatus and method for generating a SC-FDMA signal having a sequence of symbols, a signal is generated by spreading blocks of symbols using a spreading code, then applying an inverse discrete Fourier transform (IDFT) to the symbols, followed by rotating the phase of each symbol, and applying a guard interval in the form of a cyclic prefix (CP), such that the spreading code is selected from sequences having a DFT matrix and Hadamard-Walsh sequence, and whereby the difference between the amounts for rotating the phase of adjacent symbols is constant. The spreading may be changed so as to change the data rate for each transmitter.

The invention provides a method and system for constructing a no-hit-zone bipolar frequency hopping code. The method for constructing the no-hit-zone bipolar frequency hopping code includes the steps that first, a no-hit-zone frequency hopping sequence NHZ is constructed; second, a Walsh sequence is constructed; third, the no-hit-zone frequency hopping sequence NHZ and the Walsh sequence are combined to form the no-hit-zone bipolar frequency hopping code. The method and system for constructing the no-hit-zone bipolar frequency hopping code have the advantages that according to the constructed no-hit-zone bipolar frequency hopping code, all codons are totally orthogonal as long as the delay between users is within a zero correlation zone, so that multi-site interference and beat noise of a two-dimensional coherent OCDMA system will be completely eliminated, and the near-far effect of the two-dimensional coherent OCDMA system can also be eliminated. Therefore, by means of the no-hit-zone bipolar frequency hopping code constructed through the method and system, a high-capacity two-dimensional coherent OCDMA system can be achieved, and the no-hit-zone bipolar frequency hopping code can be applied to an optical access network, an optical local area network, an optical code label switching network, an optical fiber sensor network and the like.

The invention provides a constructing method and system for the two-dimensional bipolar code of a zero-correlation region in time / frequency domain. The constructing method comprises the steps that A a time domain zero-correlation region spread-spectrum sequence LA with the zero-correlation region is constructed; B a single coincidence sequence in frequency domain is constructed; C a Walsh sequence is constructed; D the time domain zero-correlation region spread-spectrum sequence of the zero-correlation region is combined with the single coincidence sequence in frequency domain are combined to form a time / frequency domain zero-correlation region two-dimensional optical orthogonal code; and E the time / frequency domain zero-correlation region two-dimensional optical orthogonal code is combined with the Walsh sequence to form the two-dimensional bipolar code of the zero-correlation region in time / frequency domain. The method and the system have the advantages that multi-site interference and beat noise of a two-dimensional coherent OCDMA system are completely eliminated; the near-far effect of the two-dimensional coherent OCDMA system can be eliminated; the large-capacity two-dimensional coherent OCDMA system can be realized; and the method and the system can be applied to an optical access network, an optical local area network, an optical code tag switching network, a fiber optic sensor network and the like.

A wireless communication apparatus capable of minimizing the degradation in separation characteristic of a code multiplexed response signal. In this apparatus, a control part (209) controls both a ZC sequence to be used in a primary spreading in a spreading part (214) and a Walsh sequence to be used in a secondary spreading in a spreading part (217) so as to allow a very small circular shift interval of the ZC sequence to absorb the interference components remaining in the response signal; the spreading part (214) uses the ZC sequence set by the control part (209) to primary spread the response signal; and the spreading part (217) uses the Walsh sequence set by the control part (209) to secondary spread the response signal to which CP has been added.

A receiver receives elements of a signal sequence. A state generator generates a sequence of addresses to translate between a pseudonoise sequence and a Walsh sequence. A storage medium, coupled to the receiver and the state generator, stores each element of the signal sequence at a given address according to the sequence of addresses.

The invention relates to a method for creating frequency domain zero correlation area code and the device and multi-carrier CDMA system. In the embodiment, Kronecker product operation is performed by initiation sequence and Walsh sequence generated according to the system parameter to acquire frequency domain zero correlation area code; the system adopts the frequency domain zero correlation area code for data transmission and user identification, which can effectively avoid interference between users due to selective fading of channel frequency, and support more users compared to system of existing frequency domain zero correlation area code and its selection scheme and support multi-speed service , and does not need code reallocation when active user number changes.

The invention provides a communication method for unmanned aerial vehicle visual formation coordination, which comprises the steps that aircraft GPS timing systems synchronously excite visual sensors to carry out image acquisition; a local WALSH sequence generator of each aircraft generates a spread spectrum sequence under excitation of the GPS timing systems, and spread spectrum processing is carried out on data frames formed by the aircraft position, the attitude and visual images; each wing aircraft modulates spread data to a predetermined frequency band and then transmits the data to a lead aircraft, wherein the transmitting time is synchronously triggered by the GPS timing systems; a multipath spread spectrum sequence tracking loop in the lead aircraft carries out de-spreading on the data frames so as to acquire the aircraft position, the attitude and the visual images transmitted by each aircraft; and then the lead aircraft can carry out three-dimensional reconstruction according to a usual method. The method provided by the invention can complete transmission and acquisition of visual images acquired by a plurality of unmanned aerial vehicles conveniently and effectively.

A method of interrogation / response in an IFF type Mode 5 communications system comprises at least the following steps: modulating the header of an interrogation message by using an orthogonal or substantially orthogonal function; detecting the modulation function used for the header and determining the algorithm for the decoding of the information contained in the message. The modulation function is a 16-bit Walsh sequence.

A method and apparatus for providing orthogonal spot beams (14a, 14b), sectors (16a, 16b), and picocells (18), by using orthogonal auxiliary pilots and different Walsh traffic channels in adjacent areas. According to the IS-95 standard, the pilot signal is covered with the 64-chip Walsh sequence zero. Designating the 64-chip all zeros Walsh sequence as P and the 64-chip all one sequence as M, additional pilot signals are provided in the present invention by concatenating the P and the M sequences. Thus, for two pilot signals, pilot Walsh sequences of PP and PM can be used. For four pilot signals, pilot Walsh sequences of PPPP, PMPM, PPMM, and PMMP can be used. In general, the required number of pilot Walsh sequences can be generated by substituting each bit in an K-bit Walsh sequence with the 64-chip all zeros P or all ones M sequence, depending on the value of that bit.

Systems and methodologies are described that facilitate increasing system capacity in a code-limited WCDMA (e.g., TDD, FDD, ) wireless communication environment. According to one aspect, a larger code space can be defined by introducing multiple code clusters within a sector, wherein each cluster has a unique scrambling code. Codes within a cluster can have orthogonal Walsh sequences that can be assigned to user devices to facilitate communicating over a wireless network and can overlap with codes in another cluster. The unique scrambling code assigned to each cluster can ensure that duplicate Walsh sequences in another cluster in the same sector appear as a pseudo-noise codes.

Provided is a method for constructing a cognitive radio simulation system on the basis of a complementary bridge function sequence. The method comprises step 1 inputting a spectrum spreading sequence into a constructed simulation system with a walsh sequence with sequence values of '+1' and '-1' and a bridge function sequence with sequence values of '+1', '0' and '-1' serving as the spectrum spreading sequence; step 2 respectively inputting an m sequence and a bridge function sequence which serve as a spectrum spreading sequence into the constructed simulation system; step 3 considering capacity for suppressing multi-access interference of a multi-user system when the bridge function sequence with a zero correlation of a cross-correlation function is utilized to serve as the spectrum spreading sequence under the multi-user system, wherein the step 1 and the step 2 consider the capacity for suppressing multi-path interference of a single-user system. The method constructs the cognitive radio simulation system on the basis of the complementary bridge function sequence and utilizes the Underlay accessing technology. By utilizing the bridge function sequence to serve as the spectrum spreading sequence, a ternary sequence with a zero correlation zone is verified to have better multi-path interference resistance capacity than a binary sequence.

The invention provides an asymmetric watermark algorithm based on Logistic chaotic mapping and a Walsh sequence. The algorithm comprises the following steps: a characteristic matrix is obtained according to the largest singular value of each coefficient block of a carrier image; a Walsh sequence which is not related to the characteristic matrix is selected to be a public key watermark, a chaotic sequence is obtained according to the Logistic mapping kinetic equation, and the chaotic sequence is converted into a sequence of which the value is + / -1 and a sequence which is not related to the characteristic matrix is cut out from the sequence as a private key watermark; an embed watermark is obtained according to the weighted sum of the public key watermark and the private key watermark, and a watermark image is generated according to the information of the embed watermark; and the watermark image is detected. The technical scheme of the invention has the advantage of high safety, the copyright can be well protected, and advantages of good performance and good robustness can be realized.

A wireless communication apparatus capable of minimizing the degradation of the separation characteristic of response signals to be code-multiplexed. In the apparatus, a control part (209) controls both a ZC sequence to be used for the primary spread in a spreading part (214) and a Walsh sequence to be used for the secondary spread in a spreading part (217) according to the associations between sequences and CCEs established in accordance with the probability of using response signal physical-resources corresponding to CCE numbers. The spreading part (214) performs the primary spread of the response signal by use of the ZC sequence established by the control part (209). The spreading part (217) performs the secondary spread of the response signal, to which CP has been added, by use of the Walsh sequence established by the control part (209).

The invention discloses a fractional order multi-carrier multi-code-shift multi-system differential chaos shift keying modulation and demodulation method and a modem, and relates to the technical field of communication signal processing. The modulation and demodulation method comprises the steps: carrying out the serial-parallel conversion of a to-be-transmitted multi-system information packet into P-path parallel multi-system information, carrying out the bit / symbol conversion to obtain P-path multi-system parallel constellation symbols, and meanwhile, generating a fractional order chaotic signal by a fractional order chaotic generator; generating a Walsh code by a Hadamard matrix, selecting a signal obtained by multiplying a first Walsh sequence by a fractional order chaos signal as a reference signal, multiplying other 2P different Walsh sequences by the fractional order chaos signal, inputting the multiplied signals into a multi-system DCSK modulator, respectively acquiring P paths of multi-system DCSK modulation signals through modulation, adding the reference signal and the P paths of multi-system DCSK modulation signals, after completing multi-carrier modulation, sending the information to a channel for transmission, and carrying out related demodulation at a receiving end to recover original information. According to the method, the bit error rate is lower, the higher data rate is realized, and the confidentiality is higher.

The invention provides an all-zero block detection method suitable for HEVC and relates to the technical field of video processing; a walsh transform WT coefficient matrix of a prediction residual sub-block, which is arranged according to a walsh sequence, is calculated; a walsh sequence WT coefficient matrix of the same order as the TB is calculated according to the walsh sequence WT coefficientmatrix of the prediction residual sub-block; and an all-zero block is detected according to the walsh sequence WT transform coefficient or a prediction residual error. Compared with an algorithm basedon SAD and SATD, a maximum transform coefficient is directly used for detecting the all-zero block; error detection caused by the residual energy distribution difference is avoided; therefore, the detection efficiency is greatly improved. According to the method, the full-zero block in the UQ can be detected, and the all-zero block in the RDOQ can also be detected; high detection efficiency is achieved for all the four-size all-zero blocks; the loss of the rate-distortion performance of an encoder is small, which can be basically ignored; overall time consumption of conversion / quantization operation is obviously reduced, and the encoding speed is increased.

The invention provides an asymmetric watermark algorithm based on Logistic chaotic mapping and a Walsh sequence. The algorithm comprises the following steps: a characteristic matrix is obtained according to the largest singular value of each coefficient block of a carrier image; a Walsh sequence which is not related to the characteristic matrix is selected to be a public key watermark, a chaotic sequence is obtained according to the Logistic mapping kinetic equation, and the chaotic sequence is converted into a sequence of which the value is + / -1 and a sequence which is not related to the characteristic matrix is cut out from the sequence as a private key watermark; an embed watermark is obtained according to the weighted sum of the public key watermark and the private key watermark, and a watermark image is generated according to the information of the embed watermark; and the watermark image is detected. The technical scheme of the invention has the advantage of high safety, the copyright can be well protected, and advantages of good performance and good robustness can be realized.