83 results about "Coherence bandwidth" patented technology

Systems and methods of scheduling sub-carriers in an OFDMA system in which a scheduler takes into account channel conditions experienced by the communication devices to optimize channel conditions. The scheduler can partition a set of sub-carriers spanning an operating bandwidth into a plurality of segments. The segments can include a plurality of global segments that each includes a distinct non-contiguous subset of the sub-carriers spanning substantially the entire operating bandwidth. One or more of the global segments can be further partitioned into a plurality of local segments that each has a bandwidth that is less than a channel coherence bandwidth. The scheduler determines channel characteristics experienced by each communication device via reporting or channel estimation, and allocates one or more segments to communication links for each device according to the channel characteristics.

A method is provided for maintaining synchronization between an AT and a base station during an idle period. During the idle period, a reduced number of uplink reference signals for uplink channel quality estimation are sent to the base station by the AT. The uplink reference signals are sent to assist coherent demodulation and uplink channel quality estimation for scheduling. During the uplink idle period, the numbers of uplink reference signals are designed to be reduced in selective coherent bandwidths. The selection of the coherent bandwidth alternates in time and covers the entire spectrum to allow the channel quality estimation through the entire spectrum.

A apparatus and method for estimating a channel condition of a forward link by a mobile station in a mobile communication system including the mobile station and a base station for performing an operation of transmitting/receiving data using a plurality of subcarriers having mutual orthogonality. The method comprises measuring carrier-to-interference ratio (C/I) values of the subcarriers using a signal received from the base station; determining from the received signal a subcarrier for transmitting feedback information in a given coherence bandwidth; generating feedback information to be transmitted over the determined subcarrier; and transmitting the generated feedback information to the base station as information for estimating a channel condition of the forward link.

A method for configurating a basic signal allocation unit and a method of transmitting signals using the configurated basic signal allocation unit are disclosed. In particular, a basic frequency domain signal allocation unit is configurated by considering at least one selected from the group consisting of a signaling overhead, a size of a coherent bandwidth and a number of divisors among specific numbers and an OFDM symbol number corresponding to a multiple of a subframe unit, each of the specific numbers multiplied to a predetermined subcarrier spacing to enable a result value of the multiplication to have a difference smaller than a prescribed threshold from a divisor of a system bandwidth. And, a time domain unit is configurated by 1-subframe unit. Accordingly, signaling overhead can be efficiently reduced.

The present invention provides methods, apparatus and systems for delivery of digital data to stationary receivers over a terrestrial wireless link at a low data rate using a new coded orthogonal frequency division multiplexing (COFDM) scheme. Digital data is encoded and modulated using coded orthogonal frequency division multiplexing (COFDM) to produce a data stream. The data stream is communicated to a stationary receiver via a terrestrial wireless link having a ratio of (i) 50% coherence bandwidth to (ii) allocated channel bandwidth of not greater than 50%. The COFDM scheme employed by the present invention overcomes the degradation of multipath fading induced by terrestrial channels, such as the Ultra High Frequency (UHF) broadcast channel.

A system for variable-sized resource block allocation in a communication system is disclosed. A processor module is configured to construct one or more resource blocks, having one or more sizes, and to define a candidate resource block set, including one or more of the constructed resource blocks, and a coherence bandwidth set, including one or more coherence bandwidths. A coherence bandwidth estimate is derived for a resource block subframe, and the one or more resource blocks in the resource block set are ranked, based on a comparison between the coherence bandwidth estimate and each of the one or more coherence bandwidths in the coherence bandwidth set. The highest ranked resource block is allocated for a data transmission to a user; and data is scheduled in accordance with a size of the allocated resource block. The allocated resource block size is indicated to one or more mobile stations in the communication system.

Methods, apparatus and computer program products are provided for establishing a time-frequency reference signal pattern configuration in a carrier extension or a carrier segment, such as for cell-specific reference signals (CRS) and/or demodulation reference signals (DM RS). One method includes receiving information regarding a time-frequency reference signal pattern configuration in a carrier extension or carrier segment. The time-frequency reference signal pattern configuration defines a subframe to include a reference signal based upon a time density parameter and defines a resource element to be utilized within the subframe based upon a frequency density parameter. This method also includes receiving reference signals pursuant to the time-frequency reference signal pattern configuration such that reference signals have a coherence time T_coh with at least one subframe including a reference signal in the CE or CS per T_coh and a coherence bandwidth B_coh with at least one resource element containing a reference signal per B_coh.

A level of interference affecting signal components of received communication signals is estimated and used to weight the signal components. The signal components in a each of a number of groups of signal components are weighted based on respective interference estimates to thereby adjust signal components for coloured interference, which may vary significantly between different groups of signal components. Each group of signal components may include a single component or components within a relatively narrow sub-band of the communication signals, such as a coherence bandwidth of an Orthogonal Frequency Division Multiplexing (OFDM) signal.

Frequency-dependent cancellation separates a plurality of interfering signals received by a plurality of receivers. Received wideband single-carrier signals or multicarrier signals are separated into a plurality of narrowband subcarriers. Sub-carrier frequencies and frequency-band characteristics may be selected with respect to channel characteristics (e.g., coherence bandwidth, interference, etc.). A cancellation circuit provides complex weights to the sub-carrier components. Weighted components associated with each sub-carrier frequency are combined to separate a plurality of interfering signals. Optionally, a plurality of the separated subcarriers may be combined to reconstruct at least one transmitted single-carrier signal from a plurality of frequency components. Combining may include decoding, such as to reconstruct a coded sequence of data symbols transmitted via direct-sequence coding, code division multiple access (CDMA), multicarrier CDMA, carrier interferometry (CI), CI coding, or coded orthogonal frequency division multiplexing.

The present invention provides dynamic switching technique for space-time coding/decoding mode based on channel status information for a MIMO-OFDM system, in which a method for dynamic switching of space-time coding mode comprises: determining step for determining a space-time coding mode based on feedback information by a transmitter; mapping step for mapping the determined coding mode to a corresponding coder so that a number of sets symbol streams corresponding to respective transmit antennas are generated after coding a modulated symbol sequence for desired coding; and feedback step for periodically feeding used coding mode information back to a receiver via a forward control channel. The present invention defines coherent bandwidth and coherent time as measurement of switching threshold and proposes the corresponding switching policy to retain advantages such as low complexity of space-time coding, stable performance under space associated channels, complete space diversity and etc. and extend the application environment of space-time or space-frequency block coding in a OFDM system so that a MIMO OFDM system can be applied in a number of complex propagation environments.

The invention discloses a diversity channel estimate method for OFDM systems based on comb-type pilot frequency, comprising the following steps: a. carrying out diversity on pilot frequencies and ensuring that the interval between adjacent pilot frequencies in each group is less than the coherence bandwidth of the channel; b. carrying out channel estimate on pilot frequencies in each group by traditional channel estimate methods and obtaining a plurality of channel estimate values of the group; c. combining the a plurality of channel estimate values of the group obtained in step b by the way of diversity combining and obtaining new combined channel estimate values. The method solves the problem of bigger error of the influence of noises on channel estimate in transform-domain channel estimate based on comb-type pilot frequency under the condition of prior information of unknown channels. According to the technical proposal of the invention, when the diversity number is L, the gain brought by the invention to MSE is 101g (1/L)dB, thereby greatly improving the property of BER.

An apparatus and method for determining a pilot pattern in a Broadband Wireless Access (BWA) communication system are provided. In the pilot pattern determining method, an Orthogonal Frequency Division Multiplexing (OFDM) demodulator generates frequency-domain data by fast-Fourier-transform (FFT)-processing a received signal. A pilot pattern decider calculates a coherence bandwidth and a coherence time using subcarrier values received from the OFDM demodulator, and selects one of a plurality of pilot patterns according to the ratio of the coherence bandwidth to the coherence time.

An apparatus and a method for adaptive channel estimation and a coherent bandwidth estimation apparatus are provided. The adaptive channel estimation apparatus includes a first channel estimator, a coherent bandwidth estimator and a second channel estimator. The first channel estimator uses a predetermined approach to calculate a first channel response of each tone of an orthogonal frequency-division multiplexing (OFDM) signal. The coherent bandwidth estimator is coupled to the first channel estimator for calculating a coherent bandwidth according to the first channel responses. The second channel estimator is coupled to the first channel estimator and the coherent bandwidth estimator. For each of the tones, the second channel estimator calculates a weighted average according to the coherent bandwidth and the first channel responses of several adjacent tones including the aforementioned tone. The second channel estimator outputs the weighted average as the second channel response of the aforementioned tone.

The invention relates to a repeater arrangement for amplifying a communication link between a base station and user equipment, wherein the communication link comprises an uplink and a downlink utilizing frequencies within a coherence bandwidth. The repeater arrangement comprises: a first antenna for communication with the base station; a second antenna for communication with the user equipment; an amplifying device operatively connected to the first antenna and to the second antenna for conveying and amplifying communication signals between the first antenna and the second antenna, the amplifying device comprising a first signal path for the uplink and a second signal path for the downlink, the first and second signal paths having equal electrical length, in order to affect said communication signal identically in both uplink and downlink, providing same phase and amplitude characteristics to said communication signal.

In accordance with the invention, a method includes determining either the number of tones per chunk required to compute per-chunk order responsive to a sub-band bandwidth, a coherence bandwidth and number of chunks, or the number of chunks responsive to a sub-band bandwidth and a coherence bandwidth; determining an order for each chunk; and determining, for each chunk, QR decompositions for all its tones according to the determined order.

Various systems and methods are provided for channel estimation. These systems and methods (a) determine a coherence bandwidth for the channel, (b) adapt the channel estimation based on the coherence bandwidth, and (c) perform channel estimation by transmitting a channel estimation symbol over a channel. In some embodiments, the channel estimation is adapted based on the coherence bandwidth. This may include selecting a number of channel estimation symbols to transmit in a packet. Additionally, the number of channel estimation symbols transmitted in a packet can be selected by increasing the number of channel estimation symbols when the coherence bandwidth of the channel is high or decreasing the number of channel estimation symbols when the coherence bandwidth of the channel is low.

The present invention relates to a method, apparatus, and computer program product, wherein frequency co-variances or correlations of a measured power delay profile or frequency correlation function are estimated at two different non-zero sub-carrier lags of an orthogonal frequency division multiplexing channel. A ratio of squared magnitudes of the two estimated frequency co-variances is calculated and a delay spread or coherence bandwidth of said channel is estimated based on the calculated ratio.

The invention discloses a method and device for reconstituting a channel state information self-adaptive interpolation. The method comprises the steps that a receiver determines the number N of adjacent subcarriers with the correlation coefficients larger than a set threshold value according to the correlation of subscarrier channel state information, the grouping number Ns of the interpolation at each time is calculated, and at last channel state information is fed back to a transmitter in a grouping mode; after the transmitter receives the feedback information, the feedback information is analyzed first, and then the channel state information interpolation on the feedback subcarriers is used for obtaining the channel state information on subcarriers which do not feed back data in an OFDM symbol. According to the device, the receiver comprises a channel estimation module, a module for calculating the number of coherent bandwidths and the number of coherent bandwidth subcarriers, a module for calculating mutual coefficients between channel state information matrixes, an interpolation grouping number calculation module and a channel state information feedback module; the transmitter comprises a channel state information analysis module and a channel state information self-adaptive interpolation reconstitution module. Compared with a traditional clustering method for reconstituting the channel state information, the method and device can effectively lower the performance loss caused by grouped feedback.