Abstract: A method generates signals in a transmitter of a multiple-input, multiple-output wireless communications system. The transmitter includes Nt transmit antennas. A transmit covariance matrix Rt determined using statistical state information of a channel. The transmit covariance Rt matrix is decomposed using transmit eigenvalues ?t to obtain a transmit eigenspace Ut according to Rt=Ut?tU†t, where † is a Hermitian transpose. A pilot eigenspace Up is set equal to the transmit eigenspace Ut. A Nt×Tp block of pilot symbols Xp is generated from the pilot eigenspace Up and pilot eigenvalue ?p according to Xp=Up?p1/2. A data eigenspace Ud is set equal to the transmit eigenspace Ut. In addition, a Nt×Nt data covariance matrix Qd is generated according to Ud?dU†d, where ?d are data eigenvalues. A Nt×Td block of data symbols is generated, such that an average covariance of each of the columns in the block of data symbols Xd equals the data covariance matrix Qd.

Abstract: A method synchronizes transmissions through a channel in a wireless communications network including a device and a multiple coordinators within transmission range of the device. A superframe is defined to include a beacon period, a contention access period, and a contention free period. The beacon period includes multiple slots. In each coordinator, a particular beacon slot is selected to be non-conflicting with beacon slots selected by other coordinators. Beacons are then transmitted to the device by the coordinators at time periods associated with the selected slots.

Abstract: A method provides access to a channel in a network including stations and an access point connected by a common wireless channel. A station makes a request to the access point to access to the channel to transmit a data stream. The access point assigns a sequence index value to the data stream. The sequence index value is broadcast by the access point. Then, the station transmits the data stream, during a contention free period, at a time corresponding to the sequence index value.

Abstract: A method allocates data rates to layers to be transmitted in a multiple input, multiple output communications system. An input data stream is demultiplexed into multiple layers. For each layer, determine statistics representing a capacity of the layer based on past observations of transmitting the layer through a channel. For each layer, determine an optimum data rate based on the statistics. For each layer, determine if the optimum data rate is less than a minimum data rate of a set of available bit rates, and, if true, selecting, for a particular layer, the minimum data rate from the set of available data rates, and otherwise, if false, selecting, for the particular layer, a closest data rate from the set of available data rates that is less than the optimum data rate.

Abstract: A method is presented for processing signals of a multiple-input, multiple-output communications system in the RF domain. The system includes multiple transmit antennas and multiple receive antennas connected by a wireless channel. A matrix M is generated based on long-term characteristics of the wireless channel. The matrix M is multiplied times input RF signals to obtain output RF signals. The matrix can be generated in a transmitter, a receiver, or both.

Abstract: A personal identification device for use with a mobile telephone in a wireless communications network includes an connector mated to a connector of the mobile telephone normally used for a hands-free kit or a data port. In a typical application, a user of the mobile telephone calls a server. The server sends a first telephone signal to the personal identification device. The device responds with a second telephone signal, designed to simulate voice or data activity, depending on the type of connector that is used. The simulated voice activity is structured in such a way as to cause the radio signal transmitted by the mobile telephone to go on and off in response to the simulated voice activity. A nearby receiver can detect the on/off pattern. The on/off pattern is designed to convey a unique identification code.

Abstract: A method transmits packets over a single channel in a wireless communication network that includes multiple nodes. Access to the channel is gained in a transmitting node. Then, a block of packets is transmitted to a receiving node via the channel. The transmitting node receives only a single acknowledgement packet from the receiving node in response to transmitting the block of packets.

Abstract: A method suppresses interference in a time-frequency hopped, ultra wide bandwidth system. Signals corresponding to a transmitted symbol are received. The received signals are frequency demodulated, and a coefficient vector w that minimizes a cost function C ? ( w n ) = 1 ? k ? ? ? n - k ? ? ? k ? ? ? n - k ? ? ? ? ? w n H ? x k - c k ? 2 , is estimated, where ? is a weighting factor between 0, x is a vector representing the received signals, H is a frequency response of a channel used to transmit the symbol, and c is a known training symbol. A coefficient vector, ?n={circumflex over (R)}n?1{circumflex over (d)}n, is determined, where a correlation matrix for the received signals is R ^ n = 1 ? k ? ? ? n - k ? ? ? k ? ? ? n - k ? ? ? ? x k ? x k H , and an estimate of a crosscorrelation is d ^ n = 1 ? k ? ? ? n - k ? ? ? k ? ? ? n - k ? ? ? ? x k ? c k * .

Abstract: A method codes multiple data streams in multiple-input, multiple-output communications systems. In a transmitter, an input bitstream is encoded as codewords b in multiple layers. Each layer is modulated. A quasi-block diagonal, low-density parity-check code is applied to each layer, the quasi-block diagonal, parity-check code being a matrix H, the matrix H including one row of blocks for each subcode, and one row of blocks for each layer such that Hb=0 for any valid codeword. The layers are then forwarded to transmit antennas as a transmitted signal x.

Abstract: A method for communicating a bit stream using turbo coding encodes each input bit in the bitstream using a single 1/3 rate turbo encoder to produce a set of three bits. One of the three bits in each set is repeated to produce a set of four bits for each input bit. A time interval between the four bits is increased before transmitting the set of four bits on a communications channel. In a receiver, the time interval between the set of four bits received via the communications channel is decreased using a de-interleaver. The received set of four bits are diversity combine into a received set of three bits, and then a single 1/3 rate turbo decoder is used to recover an output bit for each input bit.

Abstract: A system and method schedule series of packets for transmission between terminals in a single wireless channel of a packet-switched local area network. The local area network can operate in an ad hoc mode or in infrastructure mode. A transmission rate is assigned to each of the terminals. The terminals can be mobile. Different terminals can be assigned different transmission rates, depending on a quality of the channel. That is, terminals transmitting via an error-free channel are assigned a higher transmission rate than terminals transmitting via an error-prone channel. Then, the series of packets are scheduled for transmission between the terminals such that each terminal receives a substantially equal amount of transmission time over an extended period of time.

Abstract: A method eliminates spectral lines and shapes the power spectral density of an ultra bandwidth signal. First, a train of pulses is generated. The pulses are then modulated in time according to symbols. A polarity of the pulses is inverted randomly before transmitting the pulses as an ultra wide bandwidth signal.

Abstract: An ad-hoc wireless communication network includes multiple nodes. Each node maintains a routing table. The routing table is constructed by broadcasting route request packets from a source node. The request packet includes an address of a destination node. Intermediate nodes in the network receiving the request packet, determine power and delay cost associated with the intermediate node participating in the route. If the cost is less than a threshold value, then the intermediate node participates in the routing of packets for other nodes. The intermediate node then sends a reply packet back to the source node. The reply packet includes the intermediate node addresses, as well as the power and delay costs. The source can thus construct the routing table. The source node can select a particular node for transferring application data packets based on either the power cost, the delay cost or both costs.

Abstract: A method for distributed admission control in communication channels of a network including a plurality of nodes measures, at each node, a traffic condition of a communication channel during successive time intervals having a predetermined length. At the particular node, the measured traffic condition for a last time interval is compared to a threshold. The state of the node is changed depending on the comparing.

Abstract: A method increases transmit diversity gain in a wireless communication system. In the wireless network, a transmitter has multiple antennas and a receiver has one antenna. A phase of each of received signal is measured. One signal is selected as a reference signal. For each other signal, a phase, with respect to the phase of the reference signal, is measured independently to determine feedback information indicating a required rotation of each other signal so that a phase of each other rotated signal is within an identical quadrant as the phase of the reference signal. The feedback information for each other signal is sent to the transmitter. In the transmitter, each other signal is phase rotated according to the corresponding feedback information before the signal is transmitting to the receiver.

Abstract: A wireless communication system includes a transmitter and a receiver. The transmitter includes multiple groups of transmit antennas. Input symbols are generated and then orthogonal space-time block is encoded to produce a data stream for each group of transmit antennas. Each data stream is adaptively linear space encoded to produce an encoded signal for each transmit antenna of each group according to feedback information for the group. The receiver includes a single receive antenna, a module for measuring a phase of a channel impulse response for each transmit antenna. The feedback information is determined independently for each group of transmit antennas from the channel impulse responses. The feedback information for each group of transmit antennas is sent to the transmitter.

Abstract: A method for antenna subset selection by joint processing in RF and baseband in a multi-antenna systems. Lt input data streams are generated in a transmitter for either diversity transmission or multiplexing transmission. These streams are modulated to RF signals. These signals are switched to the t branches associated with the t transmit antennas, and a phase-shift transformation is applied to the RF signals by a t×t matrix multiplication operator ?1, whose output are t?Lt RF signals. These signals are transmitted over a channel by t antennas. The transmitted signals are received by r antennas in a receiver. A phase-shift transformation is applied to the r RF signals by a r×r matrix multiplication operator ?2. Lr branches of these phase shifted streams are demodulated and further processed in baseband to recover the input data streams.

Abstract: A method and system transmits a stream of data symbols in a multiple-input/multiple-output wireless communications system that includes M pairs of transmitting antennas. The stream of data symbols are demultiplexed into M sub-streams and adaptively modulated and coded to a maximum data rate while achieving a predetermine performance on an associated channel used to transmit the sub-stream. Space-time transmit diversity encoding is applied to each coded sub-stream to generate two output streams, one output stream for each antenna.

Abstract: A method transmits an input stream of data symbols in a multiple-input, multiple-output wireless communications system. The input stream is demultiplexed into M substreams. Each of the M substreams is adaptively modulated and coded to a coded substream according to channel conditions. A first of the M coded substreams is space-time transmit diversity encoding into two space-time transmit diversity encoded substreams. There is one space-time transmit diversity encoded substream for each one of two transmit antennas. Each other coded substream is transmitted directly by a corresponding one of remaining M−1 transmit antenna.

Abstract: A method and system transmits an input stream of data symbols in a multiple-input/multiple-output wireless communications system that includes M subgroups of transmitting antennas. A stream of data symbols is provided to a combined switch and demultiplexer. The combined switch and demultiplexer selects a subset L of the M subgroups of antennas as active, where L<M. The demultiplexer then splits the data stream into L substreams, which are fed to the L subgroups of antennas. Before transmission, each of the L substreams is adaptively modulated and coded to a maximum data rate while achieving a predetermined performance on an associated channel used to transmit the substream. Space-time transmit diversity encoding is applied to each coded substream to generate multiple output streams, one output stream for each antenna of each of the L subgroups. The selection by the switch is based on channel conditions fed back by a receiver of the output streams.