75 results about "Multi-carrier code-division multiple access" patented technology

An approach for utilizing a pilot scheme in a spread spectrum communication system (e.g., Multi Carrier Code Division Multiple Access (MC-CDMA)) is provided. A communications link includes a sub-bands and a single pilot channel that is designated for the sub-bands for channel estimation. Pilot symbols transmitted over the single pilot channel are used to determine a first channel estimate associated with a first one of the sub-bands, and a second channel estimate corresponding to a second one of the sub-bands is derived from the first channel estimate.

Disclosed is an adaptive downlink packet transmission method for a multicarrier Code Division Multiple Access (MC-CDMA) system. The method can allocate radio resources efficiently according to the variations of channel conditions for each user terminal, allocate transmission power appropriately according to the interference from the same cell, and minimize interference to adjacent cells. The adaptive downlink packet transmission method includes the steps of: a) estimating a signal-to-interference-and-noise ratio (SINR) in a user terminal after channel equalization and despreading by measuring a downlink pilot channel; b) measuring an average interference factor and an average noise power; and c) allocating radio resources adaptively in the central station by determining transmission slots in a transmission frame, the number of spreading codes to be used in each transmission slot, symbol energy for each spreading code, and a transmission method, until transmission slots and packets to be allocated are not available.

A multi-code multicarrier CDMA system and method for communicating data by transforming a stream of data into a plurality of code sequences selected from a code book by associating symbols of the data stream with the code sequences of the code book, wherein the codebook includes M code sequences and each of the code sequences has a length of N data symbols, copying each of the code sequences onto one or more of a plurality of subcarriers, transmitting the plurality of subcarriers, receiving the plurality of transmitted subcarriers, demodulating the received subcarriers to result in the code sequences, transforming the code sequences back into the stream of data based upon the associations between the code sequences of the code book and the symbols of the data stream, changing at least one of the number M and lengths N of the code sequences in the code book.

The invention discloses a channel distribution method of multi-carrier code division multiple access system, comprising: in each section, selecting one or several frequency points as the main carrier frequency from the distributed frequency points while the left frequency points as auxiliary carrier frequency; according to the priority level, transmitting the downward guide time slot, the broadcast information and the calling information on the main carrier frequency with highest priority and arranging other public control channel on other main carrier frequency; indicating the main carrier frequency of system, so the base station can find the frequency of transmitting broadcast and calling information, and adding the information of frequency points on the all distributed information of all channels; the main and auxiliary carrier frequencies use the same disturbing code and the basic training sequence; operating the multi-time slot arrangement on same carrier frequency; setting the upward-downward switching points of main and auxiliary carrier frequencies as same. The invention can arrange a plurality of main carrier frequencies to provide the public access control channel service and reduce the interface probability and the access time in the accessing time of user terminal.

The invention claims to protect a space time block coding (STBC) MC-CDMA (Multicarrier Code Division Multiple Access) signal blind identification method based on the cyclostationarity, and belongs to the technical field of signal processing. The method comprises the following steps: establishing a selection standard of signal correlation functions according to the baseband physical model, signal construction and matrix representation of an STBC MC-CDMA system, and estimating corresponding fourth-order cumulants of the correlation functions; combining a fourth-order cyclic cumulant with the parameter of a channel to establish a cyclic statistic; and extracting a detection threshold according to the detection of cycle frequency, and making a judgment by comparing the detection threshold with the cyclic statistic to realize identification. As indicated by computer simulation, STBCMC-CDMA signals can be effectively identified with low complexity by adopting an algorithm adopted in the invention, and working under the condition of low input signal to noise ratio is feasible. Meanwhile, compared with a conventional identification algorithm, the algorithm adopted in the invention has the advantage that the influence of random noise is reduced by using the advantage of the fourth-order cyclic cumulant, so that the system performance is improved.

A apparatus and method for improved performance in radio telecommunications systems, and in particular multi-carrier code division multiple access (MC-CDMA) networks that employ pulse-shaping filters on the transmit side of a radio link. In order to more accurately transmit a radio signal bearing a symbol sequence, the modulated and spread information stream is upsampled using a technique that involves inserting zeros in the frequency domain. A corresponding downsampling procedure on the receive side permits reconstruction of the transmitted symbols. A new channel estimation algorithm may also be used, and the improved channel estimation advantageously employed to obtain more faithful symbol detection.

An improved transmission method for high-rate digital communication on unshielded twisted copper pairs for Very-High Speed Digital Subscriber Loop (VDSL) modems. The new modulation scheme is a Multi Code Multi Carrier Code Division Multiple Access, hereafter named MC² CDMA. The system takes advantage from both the CDMA modulation and the Multi-Carrier transmission and, in addition, the channel throughput is increased adopting a multi-code approach. The novel scheme encompasses transmitter, channel and receiver. loading.

The present invention discloses a MIMO system and method, which is suitable for MC-CDMA communication system with multiple paths to obtain the spectrum efficiency and gain simultaneously. The transceiver includes steps of simultaneously transferring a transmitting data to a plurality of parallel data streams, and space time block encoding each data. Then, spreading the encoded data streams with a pre-designed space-path spreading code, and transmitting data with the transmit antennas through a multiple paths. Finally, at each receiver, despreading received data by the matched filters, and separating mutually interfering signal with a linear combiner and a BLAST detector to obtain the diversity gain.

A system for performing adaptative multi-carrier code division multiple access (AMC-CDMA) is provided. The system determines a channel performance metric for each of a plurality of carriers and then determines at least one AMC-CDMA parameter for each of the carriers based on the channel performance metric. Modulator circuitry then modulates the signal on each carrier using the specified AMC-CDMA parameters for transmission over a wired connection.

The invention relates to radio engineering, more specifically to a method and a device for receiving multipath signals in a radio communications system with a code division multiple access (CDMA) and can be used for the receiving equipment of a base station. Said invention makes it possible to compensate a reciprocal signal interference of all user beams of information and pilot channels in a shaped complex cross-correlation response of all user beams of the information and pilot channels. The number of information channels and the data transmission rate in the information channels can vary from user to user. A serial compensation of the reciprocal signals interference of all user beams of the information and pilot channels during measurement of user signal parameters and complex waveform envelopes of all user beams is carried out in several iterations.

The invention discloses a method for estimating a channel of a multi-carrier code division multiple access system, which comprises the steps: A. a pilot symbol and a spread-spectrum symbol are mapped by a sender to a sub-carrier which bears a orthogonal frequency division multiplexing (OFDM) symbol; the pilot symbol and the spread-spectrum symbol are carried out time division multiplexing and transmission processing and sent to a receiver; B. a current first frequency response of the channel is determined by the receiver according to the preserved and received pilot symbol; C. the received spread-spectrum symbol is carried out a channel pre-equalization processing by the receiver according to the current first frequency response of the channel; D. the spread-spectrum symbol is carried out a spread-spectrum code despeading processing by the receiver; the service OFDM symbol is carried out a channel equalization processing. The invention solves the problem of that low accuracy of the channel estimation algorithm caused by a phase rotation of the information borne by the sub-carrier of the multi-carrier code division multiple access system which is generated by complex multipath components. The invention also discloses a channel estimation system for the multi-carrier code division multiple access system at the same time.

The invention discloses a setting method of a CDMA (code division multiple access) wireless communication network in high-speed rail environment. The CDMA wireless communication network comprises a base station set. Each base station comprises more than two signal sources equal in communication coverage radius. Antenna included angle of the base station signal sources meets the conditions that the included angle of the signal sources in the same base station is smaller than phi(S):phi(s)=theta-2*tan<-1>tau*v/s, the theta refers to 5dB lobe angle of the base station signal source antennas, the s refers to a definite distance of the base station signal source antennas from a rail in an actual scene, the tau refers to regulated CDMA system switching time, and the v refers to maximum train speed. Different stations can be set by the method according to different transmission environments before planning and construction, certain relation among azimuth, station spacing and the distance from the rail is guaranteed, construction efficiency can be improved effectively, late optimization work is reduced effectively, and network quality is improved effectively.

The invention relates to a time-frequency coding diversity MT-CDMA (multiple tone-code division multiple access) system transmitting and receiving method and belongs to a broadband multicarrier wireless communication transmitting and receiving method. A two-dimensional dispreading and multi-path separation module utilizes a time-frequency two-dimensional spread spectrum code group matrix, the two-dimensional dispreading and multi-path separation of users is realized, multiple paths of mutually irrelevant fading signals are obtained, each path of signals is merged by a phase correction and merging technology, and final output results are obtained through judgment; the spread spectrum code length can be any integral multiple of the subcarrier number, each user carries out two-dimensional coding according to a time-frequency coding grid chart, the duration time of a basic frame is enabled to be constant, and the data rate of a single user of a system is not reduced; and multiple multicarrier symbols are used as the basic frame during the system processing, and the basic frame is respectively used as a basic unit of processing time at transmitter and receiver ends. The transmitting and receiving method has the advantages that the method maintains the compatibility of the existing MT-CDMA system on the basis of a time-frequency coding diversity MT-CDMA wireless communication system of a RAKE receiver, and the system modification can be conveniently completed.

A channel estimation method in a wireless communication system based on multicarrier-code division multiple access (MC-CDMA) using frequency interleaving. A transmitter generates transmission symbols using a pilot signal (P) and an inverted pilot signal (−P) according to subcarriers on which spread symbols generated from a spectrum spreading operation are sent, performs an interleaving operation for the transmission symbols in a frequency domain, and transmits a result of the interleaving operation. A receiver extracts the pilot signal (P) and inverted pilot signal (−P) included in the transmission symbols and performs channel estimation.

A passive optical network (PON) for providing a large amount of data at high speed to subscribers is provided. In particular, a PON employing a multi-carrier CDMA in which a CDMA method is applied for an upstream signal is provided. The PON employing a multi-carrier CDMA includes: optical network terminals (ONTs) for transmitting CDMA-based data using multiple carriers to an optical line terminal (OLT) and for receiving Ethernet-based data transmitted from the OLT; the OLT for transforming CDMA-based data received from the ONT into Ethernet-based data, for transmitting the Ethernet-based data to a higher network, and for transmitting Ethernet-based date to the ONTs; and an optical coupler for coupling CDMA-based optical signals transmitted from the ONTs, for transmitting the coupled optical signal to the OLT, and for distributing an Ethernet-based optical signal transmitted from the OLT to the ONTs.