Abstract: Electronic devices may have multiple wireless integrated circuits such as first and second baseband processor integrated circuits. The first baseband processors may be used exclusively for handling packet switched traffic, whereas the second baseband processor may be used exclusively for handling circuit switched traffic. Radio-frequency front end circuitry may be used to couple multiple antennas to the baseband processors and associated radio-frequency transceivers. The first baseband processor may be coupled to a first universal integrated circuit card (UICC) storing a first subscriber profile, whereas the second baseband processor may be coupled to a second UICC storing a second subscriber profile. The first baseband processor may be used to support any desired circuit switched radio access technology, whereas the second baseband processor may be used to support any desired packet switched radio access technology.

Abstract: Electronic devices may be provided that contain wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry with first and second ports that are coupled by switching circuitry to first and second antennas. A first receiver in the transceiver circuitry may be associated with the first port and a second receiver in the transceiver circuitry may be associated with the second port. An electronic device may be operated in a single receiver mode in which only one of the receivers is active to conserve power or a dual receiver mode in which signals from both antennas may be received in parallel to compare antenna performance. Based on antenna performance metrics, the electronic device may adjust the switching circuitry to ensure that an optimal antenna is being used.

Abstract: In one embodiment, the present invention generates a single rotation angle that may be used to maximize diversity of a quasi-orthogonal space-time block code that encodes groups of four data symbols. Two rotation angles corresponding the first two data symbols in a group are set to zero, and two rotation angles corresponding to the second two data symbols in a group are set to a single initial value. A codeword distance matrix is determined for each possible combination of codewords and erroneously decoded codewords that may be generated using the initial rotation angle, and the minimum of the determinants of these matrices is selected. This process is repeated to generate a plurality of minimum determinants, and, for each iteration, a different single rotation angle corresponding to the second two data symbols is used. Then, a single rotation angle is selected that corresponds to the maximum of the minimum determinants.

Abstract: Methods and apparatus are provided for communicating data in a multiple antenna communication system having N transmit antennas. According to one aspect of the invention, a header format includes a legacy preamble having at least one legacy long training field and an extended portion having at least N additional long training fields on each of the N transmit antennas, wherein one or more of the at least N additional long training fields are comprised of only one Orthogonal Frequency Division Multiplexing (OFDM) symbol. The extended portion optionally comprises one or more repeated OFDM symbols for frequency offset estimation. In one implementation, the extended portion comprises a first high throughput long training field comprised of two repeated OFDM symbols and N?1 high throughput long training fields comprised of only one OFDM symbol. In another variation, the extended portion comprises N high throughput long training fields comprised of only one OFDM symbol.

Abstract: An exemplary fast Fourier transform (FFT) numerology for an orthogonal frequency division multiple access (OFDMA) downlink transmission system is described. The exemplary FFT numerology reduces the FFT sampling rate for a given transmission bandwidth, thereby increasing the battery life of a UE. The FFT numerology increases robustness against Doppler spread, phase noise, and frequency offset, enabling operation in channels with high delay spread, such as occurs in mountainous regions. The described numerology might provide the following without altering standard sub-frame duration: increased intercarrier spacing; reduced FFT sampling frequency across the transmission bandwidths; reduced FFT size across all transmission bandwidths; increased number of OFDM symbols per sub-frame; and/or increased cyclic prefix length choices.

Abstract: Methods and apparatus are provided for communicating data in a multiple antenna communication system having N transmit antennas. According to one aspect of the invention, a header format includes a legacy preamble having at least one legacy long training field and an extended portion having at least N additional long training fields on each of the N transmit antennas, wherein one or more of the at least N additional long training fields are comprised of only one Orthogonal Frequency Division Multiplexing (OFDM) symbol. The extended portion optionally comprises one or more repeated OFDM symbols for frequency offset estimation. In one implementation, the extended portion comprises a first high throughput long training field comprised of two repeated OFDM symbols and N?1 high throughput long training fields comprised of only one OFDM symbol. In another variation, the extended portion comprises N high throughput long training fields comprised of only one OFDM symbol.

Abstract: Methods and apparatus are provided for communicating data in a multiple antenna communication system having N transmit antennas. According to one aspect of the invention, a header format includes a legacy preamble having at least one legacy long training field and an extended portion having at least N additional long training fields on each of the N transmit antennas, wherein one or more of the at least N additional long training fields are comprised of only one Orthogonal Frequency Division Multiplexing (OFDM) symbol. The extended portion optionally comprises one or more repeated OFDM symbols for frequency offset estimation. In one implementation, the extended portion comprises a first high throughput long training field comprised of two repeated OFDM symbols and N?1 high throughput long training fields comprised of only one OFDM symbol. In another variation, the extended portion comprises N high throughput long training fields comprised of only one OFDM symbol.

Abstract: An exemplary fast Fourier transform (FFT) numerology for an orthogonal frequency division multiple access (OFDMA) downlink transmission system is described. The exemplary FFT numerology reduces the FFT sampling rate for a given transmission bandwidth, thereby increasing the battery life of a UE. The FFT numerology increases robustness against Doppler spread, phase noise, and frequency offset, enabling operation in channels with high delay spread, such as occurs in mountainous regions. The described numerology might provide the following without altering standard sub-frame duration: increased intercarrier spacing; reduced FFT sampling frequency across the transmission bandwidths; reduced FFT size across all transmission bandwidths; increased number of OFDM symbols per sub-frame; and/or increased cyclic prefix length choices.

Abstract: An exemplary fast Fourier transform (FFT) numerology for an orthogonal frequency division multiple access (OFDMA) downlink transmission system is described. The exemplary FFT numerology reduces the FFT sampling rate for a given transmission bandwidth, thereby increasing the battery life of a UE. The FFT numerology increases robustness against Doppler spread, phase noise, and frequency offset, enabling operation in channels with high delay spread, such as occurs in mountainous regions. The described numerology might provide the following without altering standard sub-frame duration: increased intercarrier spacing; reduced FFT sampling frequency across the transmission bandwidths; reduced FFT size across all transmission bandwidths; increased number of OFDM symbols per sub-frame; and/or increased cyclic prefix length choices.

Abstract: Methods and apparatus are provided for reducing power fluctuations during preamble training in a multiple antenna communication system using cyclic delays. A preamble having a legacy portion and a high throughput portion is transmitted (or received) on each of N antennas, wherein at least a portion of the preamble on a first of the N antennas is delayed relative to at least the portion of the preamble on a second of the N antennas, wherein the delay is non-orthogonal amount to introduce variation across the preambles transmitted on the N transmit antennas. The legacy portion may be, for example, an 802.11 a/g preamble.

Abstract: In one embodiment, a timing-offset estimator calculates a correlation value for each sample of an OFDM signal having a cyclic prefix for each OFDM symbol. The correlation value is provided to a tapped delay line that applies a separate weight to each of 2V correlation values, where V is the length of the cyclic prefix and the weights are based on a triangular weighting scheme that increases linearly from the first value, peaks at the Vth value, and decreases linearly to the 2Vth value. A stream of combined, squared correlation values is generated by combining and squaring the 2V weighted correlation values for each sample of the OFDM signal. For each cyclic prefix of the OFDM signal, a timing-offset estimate is determined based on a detected peak value in the stream of combined, squared correlation values. A timing-offset estimator with triangular weighting scheme may be implemented using recursive processing.

Abstract: In one embodiment, the present invention generates a single rotation angle that may be used to maximize diversity of a quasi-orthogonal space-time block code that encodes groups of four data symbols. Two rotation angles corresponding the first two data symbols in a group are set to zero, and two rotation angles corresponding to the second two data symbols in a group are set to a single initial value. A codeword distance matrix is determined for each possible combination of codewords and erroneously decoded codewords that may be generated using the initial rotation angle, and the minimum of the determinants of these matrices is selected. This process is repeated to generate a plurality of minimum determinants, and, for each iteration, a different single rotation angle corresponding to the second two data symbols is used. Then, a single rotation angle is selected that corresponds to the maximum of the minimum determinants.

Abstract: Methods and apparatus are provided for improved long preamble formats in a multiple antenna communication system having N antennas. According to one aspect of the invention, a preamble having a legacy portion and a high throughput portion is transmitted (or received) on each of the N transmit antennas, wherein the legacy portion comprises a legacy long training field and the high throughput portion comprises at least N high throughput long training fields, wherein the N high throughput long training fields are transmitted in N time slots using an N×N orthogonal matrix. The orthogonal matrix can be, for example, one or more of a Walsh matrix and a Fourier matrix. The N time slots can optionally comprise a single symbol.

Abstract: Methods and apparatus are provided for improved short preamble formats in a multiple antenna communication system having N antennas. A short preamble format having a legacy portion and a high throughput portion is transmitted (or received) on each of the N transmit antennas, wherein the legacy portion comprises a legacy long training field and the high throughput portion comprises N?1 high throughput long training fields. The legacy long training field and the N?1 high throughput long training fields can be transmitted in N time slots using an N×N orthogonal matrix, such as a Walsh matrix or a Fourier matrix. The N time slots can optionally comprise a single symbol. Backwards compatibility is optionally maintained by including a legacy short training field and a legacy signal field in the legacy portion of the short preamble.

Abstract: Methods and apparatus are provided for per-antenna training in a multiple antenna communication system having a plurality of transmit antenna branches. A long training sequence is transmitted on each of the transmit antenna branches such that only one of the transmit antenna branches is active at a given time. The active transmit antenna branch transmits the long training sequence with an increased power level relative to a transmission of a payload by the active transmit antenna branch. The increased power level for the active transmit antenna branch compensates for the inactive transmit antenna branches being silent during the given time. Thus, the active transmit antenna branch provides approximately the same antenna power while transmitting the long training sequence as a total power of the plurality of transmit antenna branches during a transmission of the payload. The increased power level can be provided, for example, by a digital-to-analog converter associated with the active transmit antenna branch.

Abstract: Methods and apparatus are provided for communicating data in a multiple antenna communication system having N transmit antennas. According to one aspect of the invention, a disclosed header format includes a legacy preamble having at least one legacy long training field and an extended portion having at least N additional long training fields on each of the N transmit antennas, wherein one or more of said at least N additional long training fields are comprised of only one OFDM symbol. The extended portion optionally comprises one or more repeated OFDM symbols for frequency offset estimation. In one implementation, the extended portion comprises a first high throughput long training field comprised of two repeated OFDM symbols and N?1 high throughput long training fields comprised of only one OFDM symbol. In another variation, the extended portion comprises N high throughput long training fields comprised of only one OFDM symbol.

Abstract: In one embodiment, a timing-offset estimator calculates a correlation value for each sample of an OFDM signal having a cyclic prefix for each OFDM symbol. The correlation value is provided to a tapped delay line that applies a separate weight to each of 2V correlation values, where V is the length of the cyclic prefix and the weights are based on a triangular weighting scheme that increases linearly from the first value, peaks at the Vth value, and decreases linearly to the 2Vth value. A stream of combined, squared correlation values is generated by combining and squaring the 2V weighted correlation values for each sample of the OFDM signal. For each cyclic prefix of the OFDM signal, a timing-offset estimate is determined based on a detected peak value in the stream of combined, squared correlation values. A timing-offset estimator with triangular weighting scheme may be implemented using recursive processing.

Abstract: A maximum a posteriori (MAP) processor employs a block processing technique for the MAP algorithm to provide a parallel architecture that allows for multiple word memory read/write processing and voltage scaling of a given circuit implementation. The block processing technique forms a merged trellis with states having modified branch inputs to provide the parallel structure. When block processing occurs, the trellis may be modified to show transitions from the oldest state at time k?N to the present state at time k. For the merged trellis, the number of states remains the same, but each state receives 2N input transitions instead of the two input transitions. Branch metrics associated with the transitions in the merged trellis are cumulative, and are employed for the update process of forward and backward probabilities by the MAP algorithm.

Abstract: An exemplary fast Fourier transform (FFT) numerology for an orthogonal frequency division multiple access (OFDMA) downlink transmission system is described. The exemplary FFT numerology reduces the FFT sampling rate for a given transmission bandwidth, thereby increasing the battery life of a UE. The FFT numerology increases robustness against Doppler spread, phase noise, and frequency offset, enabling operation in channels with high delay spread, such as occurs in mountainous regions. The described numerology might provide the following without altering standard sub-frame duration: increased intercarrier spacing; reduced FFT sampling frequency across the transmission bandwidths; reduced FFT size across all transmission bandwidths; increased number of OFDM symbols per sub-frame; and/or increased cyclic prefix length choices.

Abstract: Methods and apparatus are provided for per-antenna training in a multiple antenna communication system having a plurality of transmit antenna branches. A long training sequence is transmitted on each of the transmit antenna branches such that only one of the transmit antenna branches is active at a given time. The active transmit antenna branch transmits the long training sequence with an increased power level relative to a transmission of a payload by the active transmit antenna branch. The increased power level for the active transmit antenna branch compensates for the inactive transmit antenna branches being silent during the given time. Thus, the active transmit antenna branch provides approximately the same antenna power while transmitting the long training sequence as a total power of the plurality of transmit antenna branches during a transmission of the payload. The increased power level can be provided, for example, by a digital-to-analog converter associated with the active transmit antenna branch.