Abstract: The present invention provides a subcarrier index coordinator for use with a multiple-input, multiple-output (MIMO) transmitter having N transmit antennas, N being at least two, wherein each employs a plurality of transmit symbols with used subcarriers. The subcarrier index coordinator includes a subcarrier index generator configured to generate a set of pilot subcarrier indices and a set of data subcarrier indices for transmission. Additionally, the subcarrier index coordinator also includes a subcarrier index formatter coupled to the subcarrier index generator and configured to arrange the sets of pilot subcarrier indices and data subcarrier indices within the used subcarriers during transmission based on the N transmit antennas and the plurality of transmit symbols.

Abstract: A system and method are provided for eliminating the relative phase behavior in the transmitter and receiver radios employed in a wireless MIMO communication system. The method employs a single synthesizer and allows multiple transceivers to function with the same RF reference frequency source and/or IF reference frequency source. Since each transceiver has the same RF and/or IF reference frequency, each transceiver experiences the same phase noise. Thus, the phase noise for the MIMO transmitter is now bounded by the single synthesizer. The same relative phase behavior occurs in the receive portion as well.

Abstract: A packet detection system for a packet-based wireless receiver and a method of detecting packets for use with such receiver. In one embodiment, the packet detection system includes: (1) first and second chain-level packet detection circuits and configured to produce corresponding chain-level status signals and (2) a receiver-level packet detection circuit coupled to both the first and second chain-level packet detection circuits and configured to generate receiver-level status signals from the chain-level status signals.

Abstract: The present invention provides a time-switched preamble supplement generator for use with a multiple-input, multiple-output (MIMO) transmitter employing N transmit antennas wherein N is at least two. In one embodiment, the time-switched preamble supplement generator includes an initial preamble supplement formatter configured to provide a first permutation of a set of preamble supplements to the N transmit antennas during an initial time interval. The first permutation includes a single first preamble supplement and at least one second preamble supplement. The time-switched preamble supplement generator also includes a subsequent preamble supplement formatter coupled to the initial preamble supplement formatter and configured to provide (N-1) mutually exclusive further permutations of the set to the N transmit antennas during (N-1) subsequent time intervals.

Abstract: The present invention provides a time-orthogonal preamble supplement generator for use with a multiple-input, multiple-output (MIMO) transmitter employing N transmit antennas, where N is at least two. In one embodiment, the time-orthogonal preamble supplement generator includes an initial preamble supplement encoder configured to provide a preamble supplement to each of the N transmit antennas during an initial time interval. The time-orthogonal preamble supplement generator also includes a subsequent preamble supplement encoder coupled to the initial preamble supplement encoder and configured to provide the preamble supplement or a negation thereof to the N transmit antennas during (N-1) subsequent time intervals.

Abstract: A system for synchronizing a wireless receiver is provided. The system includes a first antenna (101a) and a second antenna (101b) to receive wireless signals containing data packets. The system includes one or more analyzer components (156) operable to determine correlation metrics based on at least a portion of the first received signal and a portion of the second received signal. The system further includes a synchronization component (158) operable to use the correlation metrics to determine a preferred correlation metric for synchronization by the wireless receiver of the first and second received signals to decode the data packet. A method for synchronizing a receiver of two wireless signals is also provided.

Abstract: A wireless transceiver 10 is provided that includes a configurable analog component 14 and a controller portion 18. The configurable analog component 14 is operable to receive an input radio frequency signal and to transmit the output radio frequency signal. The controller portion 18 is operable to promote adjustment of a bandwidth of the configurable analog component 14 from at least a first bandwidth to a second bandwidth.

Abstract: The present invention provides a concurrent gain generator for use with a MIMO transmitter having an N of two or more transmit antennas. In one embodiment, the concurrent gain generator includes a first sequence formatter that provides one of the N transmit antennas with a gain training sequence during an initial time interval, and a second sequence formatter that further provides (N?1) remaining transmit antennas with (N?1) additional gain training sequences during the initial time interval to train receive gains. The present invention also provides a non-concurrent gain adjuster for use with a MIMO receiver employing an M of two or more receive antennas. In one embodiment, the non-concurrent gain adjuster includes a gain combiner that computes a common receive gain as a function of M independent receive gains, and a gain applier that applies the common receive gain to receivers associated with the M receive antennas.

Abstract: The present invention provides a signal field scaler for use with a multiple-input, multiple-output (MIMO) transmitter employing N transmit antennas, where N is at least two. In one embodiment, the signal field scaler includes a signal field generator configured to provide a signal field corresponding to a multiple concurrent transmission to each of the N transmit antennas during a time interval. Additionally, the signal field scaler also includes a signal field adapter coupled to the signal field generator and configured to apply a vector of scale factors to the signal field for each of the N transmit antennas during the time interval to allow proper decoding of the signal field by a legacy receiver and a MIMO receiver.

Abstract: The present invention provides a gain training generator for use with a multiple-input, multiple-output (MIMO) transmitter employing N transmit antennas where N is at least two. In one embodiment, the gain training generator includes a fundamental training encoder configured to provide a basic gain training sequence to one of the N transmit antennas during a time interval to produce a basic gain training waveform having a basic peak-to-average ratio (PAR). Additionally, the gain training generator also includes a supplemental training encoder coupled to the fundamental training encoder and configured to further provide (N?1) supplemental gain training sequences to (N?1) remaining transmit antennas, respectively, during the time interval to produce supplemental gain training waveforms wherein each has a supplemental PAR substantially equal to the basic PAR.

Abstract: A preamble frequency switching design technique for frequency switching the training symbols within the preamble associated with a MIMO communication system ensures that data throughput is optimized.

Abstract: The present invention is directed to a time-switched preamble generator and method of generating a time-switched preamble for use with a multiple-input, multiple-output (MIMO) transmitter employing first and second transmit antennas. In one embodiment, the time-switched preamble generator includes an initial preamble formatter configured to provide a first preamble to the first transmit antenna and a second preamble to the second transmit antenna during an initial time interval. The time-switched preamble generator also includes a subsequent preamble formatter coupled to the initial preamble formatter and configured to provide the second preamble to the first transmit antenna and the first preamble to the second transmit antenna during a subsequent time interval.

Abstract: A transmit channel (gt1, h, gr2) through which a first wireless communication transceiver is to transmit to a second wireless communication transceiver can be estimated using information indicative of a relationship between the transmit channel and a receive channel (gt2, h, gr1) through which the first wireless communication transceiver receives communications from the second wireless communication transceiver. The relationship information (35) is combined (37) with further information (31) to produce an estimate of the transmit channel.

Abstract: For use with an orthogonal frequency division multiplexing (OFDM) receiver, the present invention discloses a channel estimator that employs a training sequence received through a channel. In one embodiment, the channel estimator includes a response assesser and a reducer. The response assesser computes a channel impulse response of the channel in a time-domain based on the training sequence. The reducer, coupled to the response assesser, sets designated taps associated with the channel impulse response to substantially zero.

Abstract: The present invention discloses a transmitter and receiver for use with an orthogonal frequency division multiplexing (OFDM) communications system. In one embodiment, the OFDM communications system includes an OFDM transmitter that generates a training sequence that includes a fractional tone in a guard band thereof and transmits the training sequence via a channel. The OFDM communications system further includes an OFDM receiver that receives the training sequence and employs the fractional tone to obtain a channel response estimate.

Abstract: For use with a multiple-input, multiple-output (MIMO) transmitter, an orthogonal preamble encoder, a method of encoding orthogonal preambles and a communication system incorporating the encoder or the method. In one embodiment, the encoder includes: (1) a preamble supplement generator configured to provide a first long sequence preamble supplement to a first transmit antenna of the MIMO transmitter and (2) a preamble supplement coordinator coupled to the preamble supplement generator and configured to provide a second long sequence preamble supplement to a second transmit antenna of the MIMO transmitter, at least a portion of the second long sequence preamble supplement being a negation of the first long sequence preamble supplement.

Abstract: The quantizer parameter for video encoding of the H.263 or MPEG-4 type updates in response to buffer discrepancy adapts to the targeted number of bits per frame, and saturates the maximum change of the quantizer parameter.

Abstract: This invention relates to a compound of formula I: or a pharmaceutically acceptable salt thereof; in which preferably R3, R4 and R6 are each hydrogen; X is C═O or CH2; and R7 and R8 are each independently selected from the group consisting of hydrogen, (C1-C12)alkyl, (C3-C8)cycloalkyl and (C1-C12)alkyl (C6-C14)aryl; or R7 and R8 when taken together form a (C2-C7)alkylene group; or —NR7R8 together forms a (C2-C14)heterocyclic or substituted (C2-C14)heterocyclic. Such compounds modulate the activity of serine hydrolases and can be used in pharmaceutical compositions for the treatment of Alzheimer's disease.

Abstract: A personal computer that enters sleep mode to conserve electrical energy is responsive to a proximity detector and a proximity timer. As long as a user is near the computer, as determined by the proximity detector, the computer is controlled by an activity timer, and enters sleep mode upon being idle for a predetermined period of time. When the proximity detector determines that the user has left the computer unattended, the proximity detector starts the proximity timer. When the proximity timer expires, the computer enters sleep mode. Because the proximity timer operates only when the user has left the computer unattended, the proximity timer may be set to expire earlier than the activity timer. Consequently, the computer may enter sleep mode earlier than would otherwise be possible, and thereby consumes less energy.

Abstract: This invention relates to a compound of formula I: or a pharmaceutically acceptable salt thereof; in which preferably R3, R4 and R6 are each hydrogen; X is C═O or CH2; and R7 and R8 are each independently selected from the group consisting of hydrogen, (C1-C12)alkyl, (C3-C8)cycloalkyl and (C1-C12)alkyl(C6-C14)aryl; or R7 and R8 when taken together form a (C2-C7)alkylene group; or —NR7R8 together forms a (C2-C14)heterocyclic or substituted (C2-C14)heterocyclic. Such compounds modulate the activity of serine hydrolases and can be used in pharmaceutical compositions for the treatment of Alzheimer's disease.