Abstract: A receiver chain is provided for use in wireless data communication including a plurality of receive antennas and a vector Barker decoder or a CCK decoder. The vector Barker decoder operates on the plurality of received signals, preferably processed through a plurality of channel matched filters. The weightings of the plurality of channels can be done using a slicer variance, a PLL variance or another method.

Abstract: To detect the number of transmit antennas, a fast Fourier transform operation is performed on the received samples of the transmitted long training symbols of a preamble. Next, each of the Fourier transformed results is multiplied with the reference frequency-domain representation of the long training symbol so as to remove the effect of the symbols and to maintain the channel information. Next, inverse Fourier transform or least squares operations is performed on the multiplied values to compute channel impulse response. The number of shifted impulse response in the channel impulse response represents the detected number of transmit antennas. Packets containing preambles of the present invention may be received by extended devices as well as by legacy receivers that are not configured to receive and interpret these preambles. The training symbols may be cyclically-shifted and transmitted on different transmit antennas.

Abstract: In one embodiment, a wireless device for a wireless data communication system including the wireless device and a base station. The base station includes a plurality of first groups and a signal-processing unit. Each first group includes a receiver and at least one antenna connected to the receiver. The signal-processing unit includes memory and a processor adapted to process signals received by the first groups using a Maximum Likelihood Detection (MLD) method. The wireless device includes a plurality of second groups, each second group adapted to transmit a wireless signal to at least one first group via a corresponding communication channel. Each second group further includes a transmitter and at least one antenna connected to the transmitter.

Abstract: Systems and methodologies are described that provide low-complexity soft-output detection for MIMO communication systems. Looping can be performed over a set of constellation points per spatial stream to obtain distance metrics for each of a series of transmitted streams, for which values for the other transmitted streams can be estimated using a MIMO channel matrix and a sub-optimal MIMO algorithm. Examples of MIMO algorithms that can be utilized include Per-Stream List Detection (PSLD), Lattice-Reduced Detection (LRD), and a Guided-M Algorithm. Performance can be further improved by pre-processing the MIMO channel matrix and/or by utilizing techniques for Enhanced Metric Usage (EMU).

Abstract: In a packet detector, one or more tests are performed for packet detection according to packet detection parameters associated with the one or more tests, a rate of false detection is measured, and the packet detection parameters are adjusted accordingly to reduce the rate of false detection. The rate of false detection might be determined by analyzing post-detection and processing of a signal deemed to be a signal representing a packet for a failure of decoding indicative of a false detection. Such analysis might include testing for a failed SFD search, training symbol anomalies, poor conditioning of metrics used to determine frequency offset and OFDM timing, incorrect data fields, or the like.

Abstract: Medium access control device (301) for a mobile network station (3, 4, 5) or an access point (AP1) in a wireless local area network (1), having controlling means (302), processing means (303) and transmitting and receiving means (304); the controlling means (302) being arranged to control transmission and reception of radio frequency data signals containing data symbols; the transmitting and receiving means (304) being arranged for transmission and reception of electromagnetic data signals; the processing means (303) being arranged for detecting a first signal portion and a second signal portion in the received data signal, the second signal portion following the first signal portion and having a signal coding differing from a signal coding of the first signal portion.

Abstract: Channel estimation techniques are provided for a receiver of a wireless communication system using orthogonal frequency division multiplexing (OFDM), including legacy 802.11a and various extended rate systems. Training signals are received from one or more receive antennas. An estimated channel impulse response is computed from the received training signals by reference to a training sequence. The estimated channel impulse response is truncated in the time domain based on channel power and noise data. Channel response tracking techniques may also be implemented to correct for variations in channel response over the transmission time of a packet.

Abstract: Soft symbol decoder algorithms for multiple input, multiple output (MIMO) receivers reduce the search complexity by searching over fewer than all possible combinations of transmitted symbols to compute log metrics for each transmitted bit from each transmit antenna. In one algorithm, a sub-optimal set of transmitted symbols is computed and the transmitted symbols are restricted to neighboring constellation points of the sub-optimal set. In another algorithm, all constellation points are searched for every antenna except one. In yet another algorithm, constellation points are searched excluding more than one antenna. The non-searched antenna(s) can be handled by either a bit stuffing or a soft slicing technique.

Abstract: MIMO modulation is supported in a wireless network with at least one degenerate node. A transmitter separates data into multiple streams for modulation. To transmit the modulated data, the transmitter uses a separate antenna for each data stream or coherently combines the modulated data streams prior to transmission via fewer antenna than modulated data streams. In either case, the received signal includes a contribution from each data stream. A receiver is configured for processing multiple signals sent in parallel from multiple transmit antennas; thus, the operation of the receiver is unaffected by whether the multiple data streams of the transmitter were combined in the channel after transmission or in whole or part in the transmitter prior to transmission.

Abstract: Systems and methodologies are described for processing information at a device operating in a wireless communication system. Techniques for in-phase and quadrature (I/Q) calibration, interference cancellation, channel estimation, and signal-to-noise ratio (SNR) and rank metric calculation are provided herein. As provided herein, one or more of the described techniques can be used to adjust the performance of a wireless station in the presence of impairments to the wireless station and/or a communication link used by the wireless station.

Abstract: A receiver chain is provided for use in wireless data communication including a plurality of receive antennas and a vector Barker decoder or a CCK decoder. The vector Barker decoder operates on the plurality of received signals, preferably processed through a plurality of channel matched filters. The weightings of the plurality of channels can be done using a slicer variance, a PLL variance or another method.

Abstract: Soft symbol decoder algorithms for multiple input, multiple output (MIMO) receivers reduce the search complexity by searching over fewer than all possible combinations of transmitted symbols to compute log metrics for each transmitted bit from each transmit antenna. In one algorithm, a sub-optimal set of transmitted symbols is computed and the transmitted symbols are restricted to neighboring constellation points of the sub-optimal set. In another algorithm, all constellation points are searched for every antenna except one. In yet another algorithm, constellation points are searched excluding more than one antenna. The non-searched antenna(s) can be handled by either a bit stuffing or a soft slicing technique.

Abstract: In one embodiment, an MLD scheme for a wireless data communication system including steps (a)–(f). Step (a) includes calculating a first vector length for each of a plurality of complex vectors corresponding to a constellation having a plurality of combinations of possible data values. Step (b) includes selecting a subset of the combinations based on the first vector lengths calculated in step (a). Step (c) includes calculating, for a first transmitter, a second vector length for each complex vector corresponding to a combination in the subset. If there are one or more other transmitters, then, for each other transmitter, the method includes implementing steps (d) and (e). Step (d) includes reducing the subset based on the second vector lengths calculated in step (c). Step (e) includes calculating, for a current transmitter, a second vector length for each complex vector corresponding to a combination in the reduced subset.

Abstract: A receiver chain is provided for use in wireless data communication including a plurality of receive antennas and a vector Barker decoder or a CCK decoder. The vector Barker decoder operates on the plurality of received signals, preferably processed through a plurality of channel matched filters. The weightings of the plurality of channels can be done using a slicer variance, a PLL variance or another method.

Abstract: A wireless radiofrequency data communication system has a base-station with N first groups and a signal processing-unit with a memory and processor. Each first group has a receiver-unit provided with a receiver and at least one antenna which is connected to the receiver-unit, and the signal processing-unit is connected with each of the first groups for processing receive-signals generated by each of the first groups. The base station further has M second groups for transmitting radiofrequency signals to the first groups. Each second group has a transmitter-unit provided with a transmitter and at least one antenna which is connected to the transmitter-unit. The memory of the signal processing-unit is provided with information about the transfer-functions of radiofrequency signals from each of the antennas of the second groups to each of the antennas of the first groups, and the transmitters and receivers operate on essentially the same radio frequency or radiofrequency-band.

Abstract: An OFDM system uses a normal mode which has a symbol length T, a guard time TG and a set of N sub-carriers, which are orthogonal over the time T, and one or more fallback modes which have symbol lengths KT and guard times KTG where K is an integer greater than unity. The same set of N sub-carriers is used for the fallback modes as for the normal mode. Since the same set of sub-carriers is used, the overall bandwidth is substantially constant, so alias filtering does not need to be adaptive. The Fourier transform operations are the same as for the normal mode. Thus fallback modes are provided with little hardware cost. In the fallback modes the increased guard time provides better delay spread tolerance and the increased symbol length provides improved signal to noise performance, and thus increased range, at the cost of reduced data rate.

Abstract: The invention relates to a wireless radiofrequency data communication system comprising: a base-station comprising multiple first sets and a signal processing-unit, wherein each first set comprises a transmitter- and receiver-unit provided with a transmitter and a receiver and at least one antenna which is connected to the transmitter- and receiver-unit, wherein the signal processing-unit is connected with each of the first sets for processing signals received by the first sets and processing signals to be transmitted by the first sets, and multiple second sets, wherein each second set comprises a transmitter- and receiver-unit provided with a transmitter and a receiver and at least one antenna which is connected to the transmitter- and receiver-unit.

Abstract: Medium access control device (301) for a mobile network station (3, 4, 5) or an access point (AP1) in a wireless local area network (1), having controlling means (302), processing means (303) and transmitting and receiving means (304); the controlling means (302) being arranged to control transmission and reception of radio frequency data signals containing data symbols; the transmitting and receiving means (304) being arranged for transmission and reception of electromagnetic data signals; the processing means (303) being arranged for detecting a first signal portion and a second signal portion in the received data signal, the second signal portion following the first signal portion and having a signal coding differing from a signal coding of the first signal portion.

Abstract: A digital modulation system provides enhanced multipath performance by using modified orthogonal codes with reduced autocorrelation sidelobes while maintaining the cross-correlation properties of the modified codes. For example, the modified orthogonal codes can reduce the autocorrelation level so as not to exceed one-half the length of the modified orthogonal code. In certain embodiments, an M-ary orthogonal keying (MOK) system is used which modifies orthogonal Walsh codes using a complementary code to improve the auto-correlation properties of the Walsh codes, thereby enhancing the multipath performance of the MOK system while maintaining the orthogonality and low cross-correlation characteristics of the Walsh codes.

Abstract: The invention relates to a wireless radiofrequency data communication system comprising: