Agere Systems Inc.

Ncr Corporation

Lucent Technologies Inc.

Avago Technologies General IP (singapore) Pte. Ltd.

Jan Boer

Kai Roland Kriedte

Bas Driesen

Wilhelmus J Diepstraten

Hans Van Driest

Robert John Kopmeiners

Wilhelmus Diepstraten

Ra'anan Gil

Joachim S Hammerschmidt

Syed Aon Mujtaba

Adriaan Kamerman

Hendrik Van Bokhorst

Tim Schenk

Allert Van Zelst

Rienk Mud

Henk Van Bokhorst

Wilhelmus Josephus Diepstraten

A method and apparatus are provided for transmitting one or more symbols in a multiple antenna wireless communication system. Subcarriers from one or more symbols are interleaved across a plurality of antennas. The symbols may be, for example, long or short training symbols based on a single-antenna long or short training symbol, respectively, and wherein each subsequent subcarrier from the single-antenna training symbol is positioned in a training symbol for a logically adjacent antenna. One or more additional subcarriers may be inserted in at least one of the plurality of symbols to allow nulled subcarriers to be estimated using an interpolation-based channel estimation technique. The remaining portions of a header, as well as the data sequences of a packet, may also be diagonally loaded.

Method and apparatus for communicating symbols in a multiple input multiple output communication system using interleaved subcarriers across a plurality of antennas

A method for controlling a transmission rate of at least one transceiver, the transceiver including a transmitter and a receiver, includes: determining a signal quality characteristic corresponding to a signal received at the receiver by measuring a difference between one or more reference constellation points and one or more received constellation points, and modifying a transmission rate of the transmitter over a wireless communication channel as a function of the signal quality characteristic. The step of modifying the transmission rate over the wireless communication channel includes: determining lower and upper threshold levels representing reference minimum and maximum signal quality characteristics, respectively, corresponding to the transmission rate; maintaining the transmission rate when the measured signal quality characteristic is between the lower and upper threshold levels; and increasing the transmission rate when the signal quality characteristic is less than one or more lower threshold levels associated with one or more corresponding higher transmission rates.

Data transmission rate adaptation in a wireless communication system

In a wireless system including a wireless communication channel, a method for estimating a signal quality of a received signal includes the steps of receiving a signal from the wireless communication channel, the received signal including at least one field that is modulated and encoded in a substantially fixed manner, and generating at least one reference field based, at least in part, on the at least one field and on a channel estimation signal. The channel estimation signal is representative of at least one characteristic of the wireless communication channel. The method further includes the step of generating a signal quality estimate as a function of the at least one field in the received signal and the generated at least one reference field.

Signal quality estimation in a wireless communication system

A method and apparatus are disclosed for detecting a collision in a carrier sense multiple access wireless communication system. Each transmitting station includes a collision detector that evaluates one or more predefined criteria to determine when a collision has occurred. The collision detector evaluates the measured energy level and optionally payload and/or preamble detection information to determine if a collision has occurred. A collision occurred when an expected ACK message is not received, in the presence of an increased energy level and possibly preamble or payload detection information. The collision detector of the present invention can be activated, for example, at a time corresponding to the start of the 802.11 Short Inter Frame Space interval.

Method and apparatus for detecting a collision in a carrier sense multiple access wireless system

A method and apparatus are disclosed for transmitting symbols in a multiple antenna wireless communication system, such that the symbols can be interpreted by a lower order receiver (i.e., a receiver having a fewer number of antennas than the transmitter). For example, subcarriers from one or more symbols can be transmitted such that each of the subcarriers are active on only one of the antennas at a given time. In one implementation, the subcarriers are diagonally loaded across logically adjacent antennas. The symbols can include one or more long training symbols and optionally a SIGNAL field that indicates a duration that a receiver should defer until a subsequent transmission. In this manner, a transmitter in accordance with the present invention may be backwards compatible with a lower order receiver and a lower order receiver can interpret the transmitted symbols or defer for an appropriate duration.

Methods and apparatus for backwards compatible communication in a multiple input multiple output communication system with lower order receivers

A station for a communications network. In one embodiment, the station includes a decoder, a check processor, and a transmitter. The decoder is adapted to decode a received encoded data unit. The check processor is adapted to determine whether the encoded data unit has been correctly received. The transmitter is adapted to initiate, prior to the check processor completing the determination whether the encoded data unit has been correctly received, the transmission of an acknowledgment message comprising a frame having a plurality of different fields of data. The transmitter is adapted to modify the transmission of the acknowledgment message if the check processor determines that the data unit has not been correctly received.

Acknowledgement message modification in communication networks

A method for processing a received encoded data unit comprises: decoding the received encoded data unit; determining whether the encoded data unit has been correctly received; prior to completing the determination of whether the encoded data unit has been correctly received, initiating the transmission of an acknowledgment message; and modifying the transmission of the acknowledgment message if it is determined that the data unit has not been correctly received. In another embodiment, a station for a communications network comprises: a decoder adapted to decode a received encoded data unit; a check processor adapted to determine whether the encoded data unit has been correctly received; and a transmitter adapted to initiate the transmission of an acknowledgment message prior to the check processor completing the determination whether the encoded data unit has been correctly received. The transmitter is adapted to modify the transmission of the acknowledgment message if the check processor determines that the data unit has not been correctly received.

In a wireless system comprising at least one transceiver configurable for communication over a wireless communication channel, the transceiver comprising a transmitter and a receiver, a method for controlling a data transmission rate of the at least one transceiver comprises the steps of: (i) determining a signal quality characteristic corresponding to a signal received at the receiver by measuring a difference between one or more reference constellation points and one or more received constellation points, the signal quality characteristic representing an estimation of signal degradation; and (ii) modifying a data transmission rate of the transmitter based, at least in part, on the signal quality characteristic.

A system for operating a communication system comprising one or more transmitters and receivers. The transmitted signals are provided with a preamble for training the receiver and/or the transmitter being in communication. The quality of the received signal is measured and compared with a threshold. If the quality is higher or lower than said threshold, a short preamble processing or a long preamble processing, respectively, is used. More than one threshold and associated pairs of preambles having different length may be used.

Method for operating a communication system and a communication system with training means

A receiver, and a method for operating the receiver, for a station in a wireless local area network using a common wireless communication channel and employing a CSMA/CA (carrier sense multiple access with collision avoidance) protocol includes various modes. In normal mode, the receiver follows typical states in order to detect a message and demodulate data from the message properly. Meanwhile, a process implements a message-in-message (MIM) mode when an energy increase above a specified level is detected. While in the MIM mode, if a carrier is detected, the energy increase is caused by a new message; otherwise, the energy increase is caused by an interfering station. If the carrier is detected, the receiver begins retraining so that it can start receiving the new message as soon as the first message ends. If no carrier is detected, the receiver waits a specified time to detect a carrier or for the end of the first message, after which the receiver returns to the beginning of the normal mode. While in the normal mode, if a message is detected that is not addressed to the station, the receiver enters a hunt mode. While in the hunt mode, the receiver waits for the current message to finish. At the same time, a process implements retraining when both an energy increase above a specified level and a carrier are detected. If no carrier is detected within a specified time, or if the energy level decreases below the specified level, the receiver returns to the beginning of the normal mode.

Wireless lan with enhanced capture provision

A wireless LAN includes first stations adapted to operate at a 1 or a 2 Mbps data rate and second stations adapted to operate at a 1,2,5 or 8 Mbps data rate. The 1 and 2 Mbps rates use DBPSK and DQPSK modulation, respectively. The 5 and 8 Mbps rates use PPM/DQPSK modulation. All four data rates use direct sequence spread spectrum (DSSS) coding. All transmitted messages start with a preamble and header at the 1 Mbps rate. The header includes fields identifying the data rate for the data portion of the message, and a length field. For a 2 Mbps transmission the length field identifies the number of bytes in the data field. For a 5 or 8 Mbps the length field identifies the number of bytes in the data field which, if transmitted at 2 Mbps, would take the same transmission time of the data field, and is thus a fraction 2/5 or 2/8 of the actual number of the bytes. With this arrangements, all the stations are interoperable in a co-existent manner in the LAN.

Multirate wireless data communication system

A local area network station for receiving data symbols encoded in a spread spectrum code and transmitted over a wireless channel includes in-phase and quadrature correlators (42, 44) the output signals of which are used to address a look-up table (50) for conversion to amplitude and phase sample signals. Corresponding amplitude sample signals are integrated and stored in a plurality of registers (96) and for each symbol, the register (96) storing the maximum value is ascertained to identify the associated sample number, which is stored in a sample number register (160). This sample number is utilized to determine the time of a symbol clock signal (RXCLK) used for clocking the received data.

Clock recovery for a wireless local area network station

A multipoint data modem communication system includes a control modem (12) and a plurality of tributary modems (14, 16, 18). During an initial training mode, receiver parameters and equalizer coefficients are determined and stored in a storage device (156) in the control modem receiver at addresses associated with the tributary modems. During subsequent relatively short training signals, the stored parameters are accessed. The remote modems transmit identification address tones in parallel with the subsequent training signals, at frequencies separated by 200 Hz intervals from the training signal spectrum frequencies. A plurality of Discrete Fourier Transform (DFT) filter circuits (190) are utilized to determine the transmitted addresses by measuring the correlation of the received signal with locally-generated frequencies.

Multipoint data modem communication system

Digital Data receiving apparatus includes means for adjusting the timing of the sampling instants. A phase controlled oscillator (PCO 19) provides timing signals for sampling the received signal and is controlled, at the commencement of a received signal, by a timing initialization circuit (17) responsive to repetitive phase alterations in a training sequence. The timing initialization circuit (17) includes a plurality of Discrete Fourier Transform (DFT) circuits (23) responsive to frequencies dependent on the power spectral densities of the received signal, which received signal may be modulated at a normal rate or a fall-back rate. The DFT circuits (23) measure the correlation of locally-generated frequencies with the incoming samples for a predetermined number of such samples to produce a plurality of complex signals. A selector circuit (24) selects a pair of the complex signals dependent on the modulation rate. The provided pair of complex signals are multiplied in a complex conjugate multiplier (25) to produce a complex output signal which is fed to a phase segment detector (26) to provide a complex rotated signal. The complex rotated signal is converted in a phase-to-time-shift converter circuit (27) to a signal (m) for controlling the PCO 19.

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Jan Boer