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

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.

The invention relates to a layered space-time nonlinear precoding method in a multi-carrier code division multiple access (MC-CDMA) system. The method comprises the following steps of: firstly, establishing a precoding system; adopting geometric mean resolution on feedback channel information in the system to form a product of a unitary matrix and an upper triangular matrix to obtain a precoding matrix with the same equivalent noise gain; carrying out nonlinear modular algebra precoding (THP, Tomlinson-Harashima Precoding) among MC-CDMA subcarrier channels at the transmitting end; multiplying all subcarrier signals after carrying out THP and the unitary matrix obtained by channel geometric mean resolution and then transmitting from a corresponding antenna; and processing at the receiving end by adopting a Zero Forcing (ZF) criterion or a minimum mean-squared error (MMSE) criterion. The method effectively eliminates the layer mistaking transmission effect of a layered space-time code, improves the code mistaking performance of the system, reduces the complexity of a downlink receiver and can effectively resist the selective fading of channel frequency, thereby improving the transmission performance of the system.

A system for performing adaptative multi-carrier code division multiple access (AMC-CDMA) includes first circuitry and modulator circuitry. The first circuitry determines a channel performance metric for each of a plurality of channels. The first circuitry determines at least one parameter of bit loading for each of the channels based on the channel performance metric. The modulator circuitry modulates AMC-CDMA signals using the parameters for bit loading in each of the channels for transmission over a wired connection.

The invention relates to digital transmission. It particularly relates to a method of transmitting data using multi-carrier Code-division Multiple Access (CDMA) for accessing a transmission system. The method comprises a step of modulating the data to be transmitted using Orthogonal Frequency-division Multiplexing (OFDM) for producing OFDM modulated data symbols and a step of spreading the OFDM modulated data symbols with spreading codes including a set of predefined sequences, wherein the sequences are predefined so that they satisfy predetermined auto-correlation and / or cross-correlation criteria within a region around the zero-time offset of the correlation function, defined as an interference Free Window (IFW).

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 apparatus and method for a Multi-Carrier Code Division Multiple Access (“MC-CDMA”) transmission network is disclosed. In the MC-CDMA transmission network a plurality of spreading sequences are assigned to individual users from a plurality of predetermined spreading sequences. The spreading sequences are assigned to users in order to minimize the interference created by the assignment of spreading sequences.

The present invention provides a method and an apparatus for a wireless communication between at least one mobile station and a base station in a cellular system. The method comprises providing a desired spreading in time and frequency domains to transmit data using at least two carriers in a transmission on an uplink to the base station. Either the base station may provide an indication to the mobile station to enable the desired spreading, or alternatively, the mobile station may request it. A spread-spectrum cellular system may enable a mobile station to provide a two-dimensional spreading, which distributes spreading in time and frequency directions. A single two-dimensional spreading code or at least two one-dimensional spreading codes may provide a two-dimensional spreading. In this way, in an uplink transmission using a multi-carrier, code division multiple access (MC-CDMA) protocol, by varying the data portions being spread in time and frequency domains a joint spreading may result. The joint spreading may distribute spreading codes in the time and frequency directions to distribute the spreading in a transmission. When using the MC-CDMA protocol, a mobile station may select one or more spreading formats in an uplink transmission that may increase the success rate of the packet transmission. Moreover, use of a particular spreading format in a flexible manner may reduce the packet delay and suppress intra-cell interference.

The invention discloses a multi-passive reflection label access system based on code division multiple access and a control method. The multi-passive reflection label access system comprises a plurality of passive reflection labels, an excitation source and a receiver, wherein each passive reflection tag sends a backscattering signal of an excitation source to the receiver after sequentially carrying out frame sealing, coding and modulation on the sent data, and each code contains a unique PN sequence of the corresponding passive reflection tag; and the receiver can decode the received coded data sent by the passive reflection labels and distinguish the coded data sent by different passive reflection labels according to PN sequences obtained by decoding. The system realizes simultaneous transmission of a plurality of nodes by code division multiple access in a passive reflection communication system comprising a plurality of passive reflection tags.

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 performs steps of simultaneously transferring transmitting data to a plurality of parallel data streams, and space time block encoding each data, followed by spreading the encoded data streams with a pre-designed space-path spreading code, and transmitting data with the transmit antennas through multiple paths. Finally, at each receiver, despreading received data by the matched filters, and separating mutually interfering signals with a linear combiner and a BLAST detector to obtain the diversity gain.

Practical transmission power adaptation in multicarrier code division multiple access (MC-CDMA) communications is using either a frequency domain technique or a time domain technique or a combined frequency and time domain technique in response to channel variations. With frequency domain power adaptation, the transmission power is allocated over the N′ (1≦N′≦N) strongest subcarriers rather than over all possible N subcarriers, where the strongest subcarriers are understood to exhibit the highest channel gains. A substantially optimal N′ can be chosen so that the average bit error rate (BER) is minimized. In the time domain power adaptation technique, transmission power is adapted so that the desired signal strength at the receiver output is maintained at a fixed level. In the combined time and frequency domain adaptation technique, the transmission power is first allocated over the N′ (1≦N′≦N) strongest subcarriers rather than over all possible N subcarriers and then it is adapted so that the desired signal strength at the receiver output is maintained at a fixed level.

In one embodiment, a multi-carrier CDMA network grants radio link resources to a mobile station by maximizing soft handoff conditions, by preserving frequency continuity with the mobile station, or by load balancing across carrier frequencies in two or more cells, or by some combination thereof. The network identifies carrier frequencies having two or more CDMA channels for assignment to the mobile station. If one of those frequencies was used by the mobile station to request resources, it may be advantageous to select that frequency; otherwise or instead, the choice is narrowed to the carrier frequency or frequencies having the greatest number of available radio links. From that point, the choice may be further narrowed, for example, by selecting the carrier frequency having the most favorable CDMA channel loading across two or more cells. In another embodiment, such multi-carrier load balancing is the basis of carrier frequency selection.

This invention discloses a method and a device for testing emission power in the multi-carrier CDMA communication system including: a grouped frequency unit, a mixer, a narrow band IF band-pass filter, a detector and a digital control unit, in which, said grouped frequency unit provides local signals needed by frequency conversion of the detection signals to the mixer, which mixes the signals for testing power and the local signals to generate IF signals with the necessary frequency, said narrow band IF band-pass filter should meet the requirement of suppressing the adjacent carrier power to separate carrier signals used in power detection, said detector finishes the conversion from RF signal to analog voltage, said digital control unit finishes the digitalized process of analog voltage, control to the output frequency of the grouped frequency and process of detection result.

The invention provides a wireless network communication real-time monitoring system and monitoring method, which adopt a manner of general packet radio service (GPRS) or code division multiple access (CDMA) wireless network combination, so that the communication cost can be lowered effectively, in addition, long-distance remote video monitoring can be realized, video information is processed through a packaging mechanism, a channel coding mechanism and an error recovery mechanism, the correct rate and reliability of video transmission are effectively improved, and monitoring faults are not easy to occur; every video acquisition sub-terminal can adopt a relay transmission manner, information collected by remote video acquisition sub-terminals is transmitted to near video acquisition sub-terminals, and the collected information is sent out by the near video acquisition sub-terminals, so that the distance of remote monitoring is effectively extended; in addition, a global positioning system (GPS) and a global system for mobile communications (GSM) short message module are adopted, thereby ensuring that immediate location at the first moment is performed and monitors are warned once monitoring information becomes abnormal.

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.