Patent application number | Description | Published |
20080219144 | TIMING ADJUSTMENTS FOR CHANNEL ESTIMATION IN A MULTI CARRIER SYSTEM - Apparatus and methods are provided for making timing adjustments in a multi carrier communications system. In an aspect, a timing correction method is provided for a multi-carrier system. This includes adjusting the time basis of two or more pilot interlaces with respect to each other in order to account for timing differences between the interlaces when combining the interlaces, and then adjusting or matching the time bases of the combined interlaces with a symbol to be demodulated. The alignment and matching is performed in order to generate channel estimates for data demodulation. The channel estimates, thus generated, along with the timing alignment information are in turn used for determining timing corrections to be applied to demodulation of a particular symbol. Corresponding apparatus are also disclosed that implement the methodology. | 09-11-2008 |
20080219332 | APPARATUS AND METHODS ACCOUNTING FOR AUTOMATIC GAIN CONTROL IN A MULTI CARRIER SYSTEM - Apparatus and methods are provided for accounting for the effects of automatic gain control (AGC) in a multi carrier communications system when combining pilot tone interlaces by essentially reversing the effects of the AGC. In an aspect, a method for adjusting for the effects of automatic gain control when combining pilot interlaces in an interlace filter of a communication system is disclosed. The method includes determining a normalization gain of an applied automatic gain control normalized to a predefined time. Additionally, two or more combining coefficients for an interlace filter are determined based on a selected criterion. Each of the two or more combining coefficients is then modified based on the determined normalization gain to yield adjusted combining coefficients. Corresponding apparatus are also disclosed. | 09-11-2008 |
20090279517 | METHODS AND SYSTEMS FOR MULTI-MODE TERMINAL SCANNING - Certain embodiments of the present disclosure provide a method for scanning for paging messages in a second radio access technology (RAT) network, such as a CDMA network, while connected to a first RAT network, such as a WiMAX network. For certain embodiments, an enhanced scanning request message may facilitate establishing a scanning cycle in the first RAT that aligns with a paging cycle of the second RAT. | 11-12-2009 |
20090304100 | INTERFERENCE REDUCTION BETWEEN OFDM CARRIERS BY FREQUENCY OFFSET OPTIMIZATION - Systems and methodologies are described that facilitate signal separation across different carriers within a wireless communications environment. The systems and methods can identify a carrier spacing that can be based upon a tone spacing associated with two or more carriers. Such carrier spacing can be employed within a network in order to mitigate signal separation with multiple carriers. The subject innovation can further evaluate a carrier raster associated with a network in order to identify a carrier spacing to ensure orthogonality between tones from different carriers. | 12-10-2009 |
20090316815 | METHODS AND SYSTEMS FOR OVERHEAD REDUCTION IN A WIRELESS COMMUNICATION NETWORK - Methods and apparatus are provided for increasing throughput in a wireless communication system by reducing the amount of overhead transmitted to certain user terminals. Overhead due to control information may be reduced for these certain user terminals by selecting a low repetition factor. Overhead may be further reduced for these certain user terminals by selecting a modulation/coding scheme with a higher data rate for transmitting the control information. The selection may be based on channel conditions associated with the user terminals, such as signal-to-interference-plus-noise ratios (SINRs). | 12-24-2009 |
20090316840 | METHODS AND SYSTEMS FOR STC SIGNAL DECODING USING MIMO DECODER - Space time coding (STC) may be applied at the transmitter adding redundant information in both space and time dimensions. At the receiver, the received STC signal may be decoded using a spatial multiplexing MIMO decoding, for example, based on either Minimum Mean Square Error (MMSE) or maximum-likelihood (ML) algorithms. A selective STC decoder may incorporate both the conventional maximum ratio combining (MRC) decoding scheme and a MIMO decoding scheme. One of the STC decoding schemes may be selected, for example, based on estimated channel conditions in order to achieve a trade-off between error rate performance and computational complexity. Components used for a non-selected scheme may be powered down. | 12-24-2009 |
20100067597 | METHODS AND SYSTEMS FOR MAXIMUM-LIKELIHOOD DETECTION USING POST-SQUARING COMPENSATION - A “post-squaring” detection algorithm, and related devices, that may reduce the complexity of maximum likelihood detection (MLD) schemes while preserving their performance is provided. Rather than search for optimum metrics (such as minimum distance metrics) based on squared norm values, a search may be based on un-squared norm metrics, and the squaring may be postponed, for example, until subsequent log-likelihood ratio (LLR) computation. For certain embodiments, approximations of un-squared norm values may significantly reduce computation complexity. | 03-18-2010 |
20100091912 | METHODS AND SYSTEMS USING NORM APPROXIMATION FOR MAXIMUM LIKELIHOOD MIMO DECODING - Certain embodiments of the present disclosure provide techniques for approximate computation of l | 04-15-2010 |
20100095189 | METHODS AND SYSTEMS FOR MODIFIED MAXIMUM-LIKELIHOOD BASED TBCC DECODING - A method and apparatus for decoding of tailbiting convolutional codes (TBCC) are disclosed. The proposed modified maximum-likelihood TBCC decoding technique preserves error correction performance of optimal maximum-likelihood based TBCC decoding, while the computational complexity is substantially decreased since a reduced number of decoding states has been evaluated. Compare to other sub-optimal TBCC decoding algorithms, modified maximum-likelihood TBCC decoding achieves improved packet error rate performance with similar computational complexity. | 04-15-2010 |
20100158079 | ID-CELL INDEX SEARCH ALGORITHM AND CARRIER FREQUENCY OFFSET ESTIMATION - Techniques for initial wireless network synchronization by a mobile station are provided. For certain embodiments, the techniques may involve a joint search for the cell identification (ID-cell index) and the coarse carrier frequency offset (CFO) estimation. For certain embodiments, the techniques may be based on hard correlation and binary differential despreading that substantially simplifies computational complexity compare to known techniques that independently search for the ID-cell index and perform CFO estimation. | 06-24-2010 |
20100158170 | METHODS AND SYSTEMS USING FFT WINDOW TRACKING ALGORITHM - Techniques for the adjustment of a position of Fast Fourier Transform (FFT) window are provided. The adjustment may be based on the condition that the length of channel impulse response is larger than the length of cyclic prefix. The technique may determine a position of the FFT window that attempts to maximize carrier-to-noise (C/N) ratio value measured at the receiver. | 06-24-2010 |
20100177852 | METHODS AND SYSTEMS FOR TIME TRACKING IN OFDM SYSTEMS - Techniques proposed in the present disclosure may used to update an FFT window position and perform linear phase compensation for OFDM wireless systems with up to two antennas at the receiver. Techniques presented herein may help resolve a problem of determining an optimum FFT window position under the condition that the length of channel impulse response is larger than the length of cyclic prefix. | 07-15-2010 |
20100182899 | OFDM Time Basis Matching With Pre-FFT Cyclic Shift - In OFDM communication, a pre-FFT cyclic shift is used to achieve time basis matching among symbols, and/or between symbols and their corresponding channel estimates. | 07-22-2010 |
20110158342 | TIME TRACKING FOR A COMMUNICATION SYSTEM UTILIZING A CYCLIC PREFIX - Techniques for performing time tracking in a communication system utilizing a cyclic prefix are described. In an aspect, a receiver may perform time tracking and determine an FFT window position based on a metric related to inter-symbol interference (ISI) and inter-carrier interference (ICI). The receiver may determine an early energy for signal paths earlier than the current FFT window position, determine a late energy for signal paths later than the current FFT window position, determine the metric based on the early and late energies, compute an update amount for the FFT window position based on the metric, and update the FFT window position based on the update amount with a time tracking loop (TTL). In yet another aspect, the receiver may compute the FFT window position based on a channel impulse response (CIR) estimate directly, without using a TTL. | 06-30-2011 |
20110158367 | DUAL FREQUENCY TRACKING LOOP FOR OFDMA SYSTEMS - Methods and apparatus for correcting frequency errors between a carrier frequency of a signal received by a wireless device and a reference frequency local to the device. For certain aspects, such a method generally includes receiving a signal in a receiver having an LO producing a reference frequency, a radio frequency (RF) phase-locked loop (PLL), and a digital rotator, estimating a frequency difference between a carrier frequency of the received signal and the LO reference frequency, and applying the estimated frequency difference to the RF PLL and the digital rotator. | 06-30-2011 |
20110206151 | MULTI-TERM DEMAPPING FOR MULTI-CHANNEL WIRELESS COMMUNICATION - Providing for reduced complexity or improved accuracy in de-mapping received wireless data streams for multi-channel wireless communication is described herein. By way of example, a low-complexity likelihood algorithm can be employed to de-map data bits from the wireless data streams. In one particular example, the likelihood algorithm can approximate a received bit with a subset of received wireless symbols correlated the bit, reducing algorithm complexity. In other examples, a limited set of received wireless symbols can be employed for the subset, further reducing algorithm complexity. According to at least one other example, logarithmic terms of the algorithm can be approximated with non-logarithmic functions, such as a look-up table, series expansion, polynomial approximation, or the like. These approximations can enhance symbol de-mapping accuracy while maintaining or improving processing overhead for a wireless receiver. | 08-25-2011 |
20140003278 | ENERGY SAVING MODE WITH MAINTAINED NUMBER OF ADVERTISED TRANSMIT ANTENNAS | 01-02-2014 |