52 results about "Interleaved frequency division multiple access" patented technology

A multi-rate interleaved frequency division multiple access (IFDMA) modulation scheme permits users to transmit at different data rates or to vary their data rates while providing frequency diversity and preserving low peak-to-average power ratios and orthogonality between users at different data rates. The modulation scheme allows user-specific data block and repetition sizes, as well as user-specific modulation codes. Code assignment rules are provided for maintaining orthogonality between users having different data rates. Block and phase ramp modulation codes can be used. Asynchronous transmissions by users are supported by ensuring that the length of the cyclic extension is sufficiently long to tolerate worst case relative signal arrival delays between users and the channel pulse response duration over the communication medium. The modulation scheme can be employed in wireless communication systems, such as cellular or paging systems.

The present invention employs a pilot scheme for frequency division multiple access (FDM) communication systems, such as single carrier FDM communication systems. A given transmit time interval will include numerous traffic symbols and two or more short pilot symbols, which are spaced apart from one another by at least one traffic symbol and will have a Fourier transform length that is less than the Fourier transform length of any given traffic symbol. Multiple transmitters will generate pilot information and modulate the pilot information onto sub-carriers of the short pilot symbols in an orthogonal manner. Each transmitter may use different sub-carriers within the time and frequency domain, which is encompassed by the short pilot symbols within the transmit time interval. Alternatively, each transmitter may uniquely encode the pilot information using a unique code division multiplexed code and modulate the encoded pilot information onto common sub-carriers of the short pilot symbols.

The invention discloses a time division multiple access / frequency division multiple access (TDMA / FDMA)-based wireless sensor network (WSN) medium access control (mac) layer scheduling method. By the scheduling method, channels are distributed by using a time division multiplex (TDM) system in clusters and a frequency division multiplex (FDM) system among the clusters aiming at a clustering-based data collection type WSN network. The TDM system and the FDM system favorably overcome the defect of a large number of access conflicts of a contention type mac scheduling method under the condition of high network load. Meanwhile, by the novel mac scheduling method, carrier sense multiple access (csma) time slots are introduced at a communication stage in the clusters, so that the defect of low expansibility of the TDMA scheduling methods is overcome. A node revives in an active period to forward data and enters a dormancy state in an inactive period, so that the energy consumption is lowered. According to the conditions of the network load, by the scheduling method, the duty ratio of the active period in the communication cycle can be automatically adjusted, the dynamic requirements of the network on throughput can be met, and the time delay of the data is reduced to a certain extent.

A data transmission method using a space time block code (STBC) scheme is provided. The method includes generating a modulation symbol by performing coding and constellation mapping on an information bit, generating a frequency-domain symbol by performing discrete Fourier transform (DFT) on the modulation symbol, generating a single carrier-frequency division multiple access (SC-FDMA) symbol by performing inverse fast Fourier transform (IFFT) after mapping the frequency-domain symbol to a subcarrier, and transmitting the SC-FDMA symbol on a slot basis.

The invention relates to a time division duplex transmission method for a broadband wireless communication system, belonging to the technical field of digital information transmission. The method comprises the following steps: using a time / frequency-domain unified orthogonal frequency division multiple access (TFU-OFDMA) technology to carry out downlink multiple access so as to obtain downlink signals at a transmitting end of a base station; using a time / frequency-domain unified single carrier multiple access (TFU-SCMA) technology to carry out uplink multiple access so as to obtain uplink signals at a transmitting end of user equipment; and using a time division duplex frame structure to carry out duplex transmission on the downlink signals and the uplink signals. The TFU-OFDMA technology provided by the invention solves the multiple access problems in the TFU-OFDM (Time / Frequency-domain Unified Orthogonal Frequency Division Multiplexing) modulation process, can flexibly allocate wireless resources and can effectively overcome deep fade, narrow-band interference and the like. The TFU-SCMA technology provided by the invention solves the multiple access problems in the improved SC-FDE (Single Carrier Frequency Domain Equalization) modulation process, reserves the advantages of low complexity of the transmitting end in the SC-FDE technology, low peak-to-average power ratio and the like, and enables the receiving end to be subject to synchronization and channel estimation better.

A method and system for adaptive control of sub-carriers is useful for increasing frequency diversity gain to improve bit error rate performance in an Interleaved Frequency Division Multiple Access (IFDMA) system. The method includes selecting a combination of a Repetition Factor (RF) and a repetition block size (Q), from possible combinations of a RF and a Q, based on a number of users (Nu) (step 1405). A Spreading Factor (SF), Forward Error Correction (FEC) coding rate (R), or modulation order (M) based on the Nu is then determined (step 1410). Control signals are then provided based on the RF and Q, and based on the SF, R, or M (step 1415).

The invention is applied to the technical field of communications and provides a Mesh net based OFDMA (orthogonal frequency division multiple access) system. The Mesh net based OFDMA system comprises a Mesh net and multiple data blocks divided according to time domain and frequency domain and orthogonal but non-overlapping, the Mesh net includes multiple nodes, and each node is connected with other one or multiple nodes. The data blocks are provided with retention gaps in front of the time domain. The nodes include one control node, and synchronizing signals corresponding to the nodes are accessed in the control node, so that signals of the nodes are synchronous to the signals of control node, and the control node controls and coordinates sending and scheduling of the data blocks of the nodes through a communication protocol. The control node is further used for controlling and managing data blocks commonly needed in the Mesh net and the arrangement pattern of the data blocks in the same time domain and frequency domain. The OFDMA system is applied to Mesh Internet networks with indoors or outdoors distribution or indoor and outdoor mixed distribution of the communication nodes through combination of the Mesh net and the OFDMA technology, and frequency spectrum utilization and resource distribution and flexibility of wireless networks are improved.

The invention discloses a passive optical network uplink transmission system based on interleaved frequency division multiple access, belonging to the optical communication field. The system comprises an ONU (Optical Network Unit) end and an OLT (Optical Line Terminal) end connected with each other by an optical fiber network. The system is characterized in that the ONU end comprises an IFDMA (Interleaved Frequency Division Multiple Access) baseband signal generating module used for generating a baseband IFDMA signal by using a signal of the user, wherein the signal output by the IFDMA baseband signal generating module is transmitted to an electro-optic modulation module via an up-converter module and a filtering module in sequence; the OLT end comprises an IFDMA baseband signal demodulation module used for demodulating the user signal from the baseband IFDMA signal; and an OLT end photoelectric conversion module is used for processing the output signal by a down-converter module and a filtering module in sequence and them transmitting the processed signal to the IFDMA baseband signal demodulation module. Compared with the prior art, the passive optical network uplink transmission system based on the interleaved frequency division multiple access, disclosed by the invention, can keep the signal PAPR (Peak-to-Average Power Ratio) to be very small so that the requirements on linear operations of a demodulator and a power amplifier are reduced; moreover, the complicatedness of a transmitter is low so that the cost of ONU end photoelectric appliances is effectively reduced.

A communication system in which an access point and one or more devices communicating through the access point adaptively apply Orthogonal Frequency Division Multiple Access (OFDMA). The access point may assign orthogonal subcarriers to devices as in conventional OFDMA, but the access point senses activity on the subcarriers and selects subcarriers without activity for assignment. In an alternative approach, a device that is configured for OFDMA communication may receive a channel assignment from a device that does not support OFDMA. The OFDMA-capable device may use only a portion of the subcarriers in the assigned channel, which may be communicated to the non-OFDMA device. During the non-OFDMA device may then ignore unused subcarriers in error detection and correction to avoid incorrectly classifying communications as erroneous. Information about OFDMA capabilities, subcarrier assignments and subcarriers in use may be communicated as information elements in network control communications, such as beacons and probe messages.

The present invention discloses a block-interleaved frequency division multiple access-based passive optical network transmission method. The method includes the following steps that: channel response is measured through a DSP (digital signal processing) method; at a transmitting end, user information is modulated, pre-channel compensation is performed on a downlink at the symbol blocks of an OLT (optical line terminal), in an uplink, rear channel compensation is performed on the OLT by inserting a training sequence, a modulated symbol block of which the length is P is repeated by K times, a symbol block of which the length is P*K is subjected to the effects of M paths of different shift factors, so that M paths of signals are generated and are multiplied by corresponding phase shift factors, and phase shift output is added, so that a B-IFDM (block interleaved frequency division multiple access) symbol block can be obtained, a cyclic prefix is added, shaping and filtering are carried out, and obtained signals are transmitted; and at a receiving end, after operation such as filtering, down conversion, de-mapping and decoding is performed, transmitted original bit information is restored. With the method of the invention adopted, requirements of the transmitter of an ONU end (optical network unit), for modulators and amplifiers, are lowered, the cost of a user side can be saved, the implementation of B-IFDMA is simple, and the complexity of the algorithms and devices of the transmitting end is decreased.

The invention discloses an adjustable bandwidth offset modulation multi-carrier frequency division multiple access transmission method which comprises the steps of generating a sending signal on a sending end and a processing a receiving signal on a receiving end, wherein the whole frequency band is divided into a plurality of sub bands to be allocated to different uses for realizing frequency division multiple access, each sub band (user) adopts offset modulation, bandwidth of each sub band (user) can be independently determined, frequency spectrum overlapping is allowed among the sub bands (users), the receiving end adopts a low-complexity frequency domain balance-based iteration decoding receiver, and can realize sending diversity under the condition of dual sending antennae. According to the method provided by the invention, the peak-to-average ratio of the sending signal is greatly lowered under the condition of keeping the frequency spectrum efficiency, the dynamic and flexible frequency spectrum resource allocation is realized; and meanwhile, by adopting a multi-user united frequency domain balance-based iteration receiving signal processing method, the transmission reliability is ensured at lower complexity.

Communications are supported between wireless communication devices using OFDMA signaling and duplicate processing. An OFDMA frame, which includes first data intended for a first recipient device and second data intended for a second recipient device, is transmitted via a first sub-channel, and a duplicate of the OFDMA frame is transmitted via a second sub-channel. In some instances, additional duplicates of the OFDMA frame are transmitted via additional sub-channels. The OFDMA frame may be generated based on a first frequency and then down-clocked to a second frequency that corresponds to a bandwidth of one of the sub-channels. A wireless communication device configured to perform such operations may be compliant with one or more IEEE 802.11 communication standards, protocols, and / or recommended practices and may also be backward compatible with prior versions of IEEE 802.11. Different numbers of sub-channels and sub-channels of different bandwidths may be used to different times.

A signal generation apparatus and signal receiving apparatus according to an Interleaved Frequency Division Multiple Access scheme is provided. The signal generation apparatus generates a plurality of complex symbols by digital-modulating a plurality of data symbols, and rotates the generated plurality of complex symbols in a plurality of each different phase angles. The signal generation apparatus generates a plurality of transmission symbols by repeating a plurality of rotated complex symbols at predetermined times, and rotating the repeatedly generated plurality of transmission chips in phase angles of an orthogonal phase sequence for the respective users. When the signal receiving apparatus receives the plurality of transmission symbols generated as described above, the maximum diversity gain may be obtained.

The invention provides a resource allocation method of a multi-user multi-input single-output-orthogonal frequency division multiple access system. The method comprises the following steps of: firstly, allocating total power to all subcarriers; then, serially allocating the resource of each subcarrier, until all the subcarriers are allocated. While allocating the resource of the subcarriers, firstly, a proportion weighting coefficient of users is updated, then, a user subset sharing the current subcarriers and the power allocation among the users in the user subset are obtained through a proportion rate greedy algorithm. In the method provided by the invention, system throughput and user fairness are balanced by setting an appropriate proportion weighting coefficient, and since priority of each user is fully considered while power is allocated for the users, better throughput performance can be obtained while user fairness is ensured.

The invention discloses a frequency offset and phase offset estimation method in a single carrier interleaved frequency division multiple access (SC-IFDMA) system and mainly solves the problem that inthe prior art, the estimation precision is low under an environment with relatively poor channels. The method comprises the application steps of generating transmitting data; arriving at a receivingend by the transmitting data through the channels; extracting data of each single carrier interleaved frequency division multiple access symbol of the receiving end; carrying out frequency offset estimation through utilization of repeated data and through adoption of an iteration method; carrying out frequency offset correction on received data through estimated frequency offset; demapping frequency offset corrected signals through subcarriers to obtain transform domain data; ordering the transform domain data according to an ordering rule and extracting phases of the first K pieces of data; calculating difference values of the phases of the K pieces of data and initial phases of symbols of quadrants in which the data is located; and averaging the obtained K difference values to obtain a final phase offset estimation value. According to the method, the estimation precision is high, the frequency offset and phase offset can be effectively estimated, and the method can be used for correcting rotation of a signal constellation diagram in the single carrier interleaved frequency division multiple access system.

The invention discloses an orthogonal frequency division multiple access (OFDMA) system signal processing method and a device to lower signal distortion of an OFDMA system. The OPDMA system signal processing method includes: a base station device sends reference signals to a terminal device and receives the present downlink subchannel quality parameters determined and responded by reference signals sent by the terminal device according to the base station device; targeting to each subcarrier, adjusting error vector magnitude (EVM) repair parameters used by a pre-set EVM repair algorithm corresponding to the subcarrier according to feedback channel quality parameters of each subchannel from the terminal device; based on the adjusted EVM repair parameters of the subcarrier, using the pre-set EVM repair algorithm to conduct the EVM repair to a frequency domain OFDMA signal on the subcarrier. The frequency domain OFDMA signal on the subcarrier is obtained from a signal distorted frequency domain OFDMA signal changing from time domain to frequency domain.

The invention discloses method and device for the origination of a ranging process in a TDD-OFDMA (time division duplex-orthogonal frequency division multiple access) system, mainly for solving the problem of large influence on the ranging performance of the prior art by a channel frequency selectivity and a near-far effect. The ranging steps comprise: (1) a channel estimation for a downlink frame, (2) a pre-equalization, (3) a code word mapping, (4) an amplitude-limiting processing, (5) an IFFT (inverse fast Fourier transform), and (6) an initial power control. The ranging device comprises a downlink frame channel estimation module, a pre-equalization module, a code word mapping module, an amplitude-limiting module, an IFFT module and an initial power control module. The method and device for the origination of a ranging process in a TDD-OFDMA system disclosed by the invention have the advantage of being capable of eliminating the near-far effect and keeping the orthogonality of a ranging code in a non-fast-transforming frequency selectivity channel; and the method and device are suitable for the origination of a ranging process in a time division multiplexing WiMax (worldwide interoperability for microwave access) or LTE (long term evolution) system.

Techniques for transmitting configurable pilots in a wireless communication system are described. The placement of pilots is determined based on an assignment of resources for transmission. Different placements of pilots are used for different assignments of resources. The assignment may be for one or more frames and / or one or more H-ARQ interlaces. The placement of pilot(s) in each frame or H-ARQ interlace may be determined based on the placement of pilot(s) in prior frame(s) or H-ARQ interlace(s). Pilots are sent at time and frequency locations determined by the placement of the pilots. Each pilot may be sent on one or more subcarriers in one or more symbol periods. The pilots may be TDM pilots and / or some other type of pilot. The pilots may be sent using IFDMA, LFDMA, EFDMA, OFDMA, or some other multiplexing scheme.

The invention discloses a multi-user signal-to-noise ratio blind estimation method in a single-carrier interleaved frequency-division multiple access (IFDMA) system. The method disclosed by the invention comprises the following steps: (1) converting an input signal into a frequency domain signal; (2) converting the frequency domain data into time domain data; (3) sending a modulated signal; (4) receiving a signal containing noise; (5) separating multi-user signal to obtain each user time domain signal; (6) computing average power of the noise; (7) computing the average power of a single-carrier IFDMA symbol; (8) computing the signal-to-noise ratio of the single-carrier IFDMA symbol; and (9) computing the signal-to-noise ration of each sub-frame. The transmission efficiency of the single-carrier IFDMA system is improved through signal-to-noise blind estimation; the signal-to-noise ratio of each sub-frame is directly computed through a large number of user time domain signals; the accuracy of the signal-to-noise estimation, especially the accuracy of the low signal-to-noise ratio estimation, can be improved.

An orthogonal frequency division multiple access-passive optical network including a plurality of optical network units each configured to generate orthogonal frequency division multiplexed signals, which are allocated thereto, based on a central frequency for frequency division multiplexing that is allocated in advance, and to use the generated signals in upstream transmission.

The invention provides an instruction image wireless transmission system and method of a frequency division multiple access and time division multiple access mixed system. Instruction data is transmitted through adoption of a time division multiple access system at an uplink, and image data is transmitted through adoption of a frequency division multiple access system at a downlink. An uplink signal processing module processes the instruction data to form a way of uplink transmitting signals. The uplink transmitting signals are sent to a downlink signal processing module through a transmittingchannel of an uplink radio frequency module and a receiving channel of a downlink radio frequency module in turn. The downlink signal processing module processes a plurality of ways of image data toform a plurality of ways of downlink transmitting signals. The downlink transmitting signals are sent to the uplink signal processing module through the transmitting channel of the downlink radio frequency module and the receiving channel of the uplink radio frequency module in turn. According to the system and the method, an asymmetric system is employed, namely, the time division multiple accesssystem is employed at the uplink, and the frequency division multiple access system is employed at the downlink, so parallel transmission of a plurality of ways of instruction data and image data isrealized.

The application relates to scheduling for orthogonal frequency division multiple access (OFDMA) transmissions in a wireless local area network (WLAN). An access point (AP) contends for a medium during a contention period in order to obtain exclusive control of the medium for a certain time period that may include one or more transmission opportunities. The AP and client stations (STAs) communicate during the time period using orthogonal frequency division multiple access (OFDMA) techniques with scheduled use (i.e., allocation) of sub-channels of the medium. The AP controls this scheduling for down-link and up-link communications by sending control signaling to inform the STAs of the resource allocation schedule which specifies STAs involved in the OFDMA communications along with the sub-channel identification bandwidth allocated to each STA. The control signaling may be a combination of physical layer (PHY) and medium access control layer (MAC) communicated information.

The invention discloses a pre-compensation method and device for the descending frequency offset of an orthogonal frequency division multiple access (OFDMA) communication system. The method comprises the following steps: a base station obtains a frequency offset value and an ascending channel estimation value corresponding to a subcarrier occupied by a user terminal; the base station obtains the value of a frequency offset pre-compensation parameter corresponding to the subcarrier according to the frequency offset value, the ascending channel estimation value and the transceiving signal module of the OFDMA communication system relevant to the frequency offset; and the base station uses the obtained value of the frequency offset pre-compensation parameter to carry out frequency offset pre-compensation to a descending signal on the subcarrier occupied by the user terminal. According to the method and the device, the descending signal of user terminals which occupy different subcarriers can be subjected to frequency offset pre-compensation by a respective proper frequency offset pre-compensation parameter, and therefore the method and the device can be used for different occasions with bigger user equipment (UE) frequency offsets.