Abstract: Methods and systems are presented which provide selection techniques for network equipment to communication stations with access point information that may be utilized to select network equipment for determining a location of the communication station. Techniques are disclosed involving location determination information in wireless networks. Such techniques may involve time of flight distance measurement protocols, signal strength measurement techniques and wireless communication networks. The networks may include IEEE 802.11 networks. In some embodiments, a device or communication station may receive a list of access point entries including data structures that have logical links corresponding to neighboring access points, the list being usable by the device to select an access point in a constant O(1) time. The data structure many include an address access point identifier, the geographic coordinates of the access point, a height above a floor value, unit types, and the error values.

Abstract: Methods and systems are presented which provide selection techniques for network equipment to communication stations with access point information that may be utilized to select network equipment for determining a location of the communication station. Techniques are disclosed involving location determination information in wireless networks. Such techniques may involve time of flight distance measurement protocols, signal strength measurement techniques and wireless communication networks. The networks may include IEEE 802.11 networks. In some embodiments, a device or communication station may receive a list of access point entries including data structures that have logical links corresponding to neighboring access points, the list being usable by the device to select an access point in a constant O(1) time. The data structure many include an address access point identifier, the geographic coordinates of the access point, a height above a floor value, unit types, and the error values.

Abstract: A novel and useful apparatus for and method of single antenna interference cancellation (SAIC) in a wireless communications system. A class of algorithms is disclosed for Downlink Advanced Receiver Performance (DARP) receivers based on a novel metric calculation used during equalization and optionally in other portions of the receiver as well, e.g., soft value generation. A DARP receiver for 8PSK EDGE modulation is presented wherein the interfering signals comprise GMSK modulated signals. The modified metric takes into account the rotation remaining in the noise component of the received signal after de-rotation of the 8PSK signal. Considering the interferer to be a GMSK signal, the I/Q elements of the noise are correlated and this fact is used to modify the decision rule for the received signal thus improving the performance of the equalizer. The model is further extended to take into account temporal error correlation.

Abstract: A novel and useful apparatus for and method of Gaussian Minimum Shift Keying (GMSK) single antenna interference cancellation (SAIC) for use in a digital receiver. The invention comprises an interference mitigation module that treats the problem of GMSK SAIC in a blind manner. The interference mitigation mechanism is operative to compensate for the co-channel interference added in the communications channel which is subject to multipath propagation and fading, receiver filter and any pre-channel estimation filtering. The interference mitigation module takes advantage of the spatial diversity making up multiple branches of the received signal. The branches comprise the in-phase and quadrature elements of the received signal, the sampling phases if over sampling is applied (i.e. T/m sampling) and/or multiple antennas. The invention utilizes the spatial diversity of these multiple representations of the received signal and combines (i.e.

Abstract: A novel and useful apparatus for and method of single antenna interference cancellation (SAIC) in a wireless communications system. A class of algorithms for Downlink Advanced Receiver Performance (DARP) receivers based on a novel metric calculation used during equalization and optionally in other portions of the receiver as well such as soft value generation. A DARP receiver for 8PSK EDGE modulation is presented wherein the interfering signals comprise GMSK modulated signals In accordance with the invention, the modified metric is adapted to take into account the rotation remaining in the noise component of the received signal after de-rotation of the 8PSK signal. Considering the interferer to be a GMSK signal, the I/Q elements of the noise are correlated and this fact is used to modify the decision rule for the received signal thus improving the performance of the equalizer. The model is further extended to take into account temporal error correlation.

Abstract: A novel and useful channel tracking mechanism operative to generate channel estimate updates on blocks of samples during reception of a message. The tracking mechanism is based on the weighted recursive least squares algorithm and implements the estimation process by recursively updating channel model parameters upon the arrival of new sample data. The mechanism is operative to update channel estimate information once per sample block. An interblock exponential weighting factor is also applied. The block length is chosen short enough to enable good tracking performance while being sufficiently long enough to minimize the overhead of generating preliminary decisions and of updating precalculated tables in the equalizer. The method of the invention can be performed in either hardware or software. A computer comprising a processor, memory, etc. is operative to execute software adapted to perform the channel tracking method of the present invention.

Abstract: A novel and useful apparatus for and method of I/Q gain mismatch compensation for use in a communications receiver. The invention is operative to calculate an estimate of the I/Q gain mismatch. Each input sample is subsequently multiplied by the inverse of the estimate to generate compensated samples. The training sequence portion of the uncompensated input samples is used to generate the I/Q gain mismatch estimate. In accordance with the present invention, the H matrix used in calculating the gain mismatch estimate is pre-calculated for several channel lengths and stored in memory. An estimate of the channel is generated which provides the channel length and the location in the input sample buffer of the first training sequence sample to be used in calculating the gain mismatch estimate. The channel length is used to determine the number of training sequence samples to be used and to select one of the previously calculated H matrices.

Abstract: An apparatus for and method of converting soft symbol decision information into soft bit decision information that overcomes the disadvantages of the prior art. The invention is adapted to receive M soft symbol values where each symbol represents m bits (M=2m). The output for each symbol comprises m soft values of bits representing the symbol. The invention is operative to convert the soft symbol values to soft bit values using the log likelihood ratios (LLRs) of a bit and a symbol expressed as conditional probabilities. The method of the invention is presented which can be performed in either hardware or software. A computer comprising a processor, memory, etc. is operative to execute software adapted to perform the soft symbol to bit conversion method of the present invention.

Abstract: A novel and useful apparatus for and method of determining the channel order and channel estimate in a communications system such as a wireless communication system including cellular and cordless. Such channels are typically characterized by rapidly changing impulse response and their taps can be modeled as zero-mean, complex, Gaussian random processes. A sufficiently long, initial channel estimate of length is performed so as to ensure that the actual channel taps will be contained in the estimated taps thus making certain that the equalizer will effectively eliminate intersymbol interference. Channel estimation is performed during each burst using the training sequence transmitted in the middle of the burst. The tap energies are averaged so as to track slow variations in the pattern of resultant channel taps. A noise floor is calculated using the lowest averaged taps and a threshold is computed based thereon and applied to the average taps.

Abstract: A novel and useful apparatus for and method of DC offset compensation for use in a communications receiver. The invention is operative to calculate an estimate of the DC offset which is subsequently subtracted from each input sample to generate compensated samples. The training sequence portion of the uncompensated input samples is used to generate an estimate of the DC offset. The vector used in calculating the offset estimate is pre-calculated for several channel lengths and stored in memory. An estimate of the channel is generated which provides the channel length and the location in the input sample buffer of the first training sequence sample to be used in calculating the offset estimate. The channel length is used to determine the number of training sequence samples to be used and to select one of the previously calculated vectors.

Abstract: An apparatus for and method of generating soft decision information from a sequence of hard symbol decisions output from a decoder in a concatenated communications receiver. Soft symbol decisions are computed given hard symbol decisions from the equalizer, channel estimation information (i.e. FIR filter taps used to estimate the channel), and the input samples received from the channel. The log likelihood ratio (LLR) for all symbol possibilities is calculated by computing the conditional probability of the input sample sequence given the hard symbol decision sequence. The noise variance is optionally used in computing the soft output values, thus improving the overall performance of the receiver. In one embodiment, symbol vectors are calculated beforehand and stored in a table. An error vector calculator functions to calculate an error vector that is applied to soft output calculation units. Each soft output calculation unit functions to generate a soft output value for a particular symbol candidate.

Abstract: An apparatus for and method of converting soft symbol decision information into soft bit decision information that overcomes the disadvantages of the prior art. The invention is adapted to receive M soft symbol values where each symbol represents m bits (M=2m). The output for each symbol comprises m soft values of bits representing the symbol. The invention is operative to convert the soft symbol values to soft bit values using the log likelihood ratios (LLRs) of a bit and a symbol expressed as conditional probabilities. The method of the invention is presented which can be performed in either hardware or software. A computer comprising a processor, memory, etc. is operative to execute software adapted to perform the soft symbol to bit conversion method of the present invention.