Abstract: A method selects a route in a wireless cooperative relay network of nodes, the nodes including a source, a set of relays, and a destination. A codeword is encoded as a data stream. The data stream is transmitted from a source to a destination via a set of relays. Mutual information is accumulated at a particular node to decode the data stream and recover the codeword. Then, a route from the source to the destination is selected based on channel state information between the nodes while transmitting and accumulating.

Abstract: A system incorporates time-hopped impulse-radio (TH-IR), transmitted-reference impulse-radio (TR-IR) and noncoherent transceivers in the same wireless network. A transmitter modulates a sequence of bits in a wireless communications network by selecting one coding sequence from a set of orthogonal or quasi-orthogonal coding sequences based on a current subsequence of bits of the input sequence, generating a reference waveform and a data waveform of a waveform pair for each sequence.

Abstract: A method encodes a sequence of blocks of input bits to be transmitted over a wireless channel. Each block of input bits is converted to a codeword, and each codeword is mapped to multiple sub-blocks of complex numbers. Each sub-block is multiplied by a disambiguating spreading transform to obtain a sub-block of transformed symbols, which can be modulated and transmitted to a receiver, where each received block is demodulated to a block of complex numbers, which are partitioned into sub-blocks. The sub-block of complex numbers are converted to a set of likelihood ratios that correspond to decoded codewords. The input bits can be decoded unambiguously even if only one of the blocks of symbols corresponding to the block of input bits is received correctly.

Abstract: A method minimizes a rate for feeding back channel state information from a receiver to a transmitter in a multi-input, multi-output communications systems. A temporal autocorrelation function of the channel between the transmitter and the receiver is determined. A spatial covariance information is estimated of the channel. Then, the minimum rate for feeding back channel state information from the receiver to the transmitter is based on actual channel state information and the estimated spatial covariance information and the temporal autocorrelation function.

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 selects an optimal route in a cooperative relay network including a set of nodes. For each node in a set of nodes of a cooperative relay network, dynamically varying channel state information is determined. A transmission policy based on the dynamically-varying channel state information is selected, in which the transmission policy includes selected nodes forming an optimal route, a transmission mode for each selected node, and a transmission power for each selected node.

Abstract: In a time-hopped impulse radio system, each symbol is transmitted over a channel having different multipath components as a set of Nf frames. Each frame includes one pulse. All frames of a received signal corresponding to the symbol are sampled to generate Nf×L samples, where L is the number of samples for each frame. Then, the Nf×L samples are combined according to a minimum mean square error criterion to obtain a decision variable corresponding to the symbol.

Abstract: A method and system selects a subset of antennas from a set of antennas to transmit user data in a wireless communication system. The user data is transmitted during a first transmission time intervals (TTI) using a first subset of antennas. Pilot tones are transmitted during a second TTI using a second subset of antennas. Corresponding channel qualities are estimated for the first subset of antennas and the second subset of antennas from the user data and the pilot tones. Then, based on the estimating, a best subset of antenna is selected from the first subset of antennas and the second subset of antennas to transmit the user data during a subsequent TTI.

Abstract: A method for transmitting packets from a source node to a destination node via relay nodes of a wireless network. Packets are transmitted from the source node, along a route of relays nodes, to the destination node in a wireless network. Energy of the packets is accumulated only in the destination node by storing multiple versions of the packet. The packets are decoded in the destination node using the accumulated energy.

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 method signals a quality of range estimates in a UWB network. For each range estimate, a confidence level of a range estimate is signaled, a confidence interval for the range estimate is signaled, and a confidence interval scaling factor for the confidence interval is signaled.

Abstract: A method and apparatus for transmitting a packet in a wireless communications network is presented. A packet is constructed to include synchronization header, a physical layer header, and a payload. A preamble and a start of frame delimiter are inserted in the synchronization header. Multiple fixed length ternary sequences are inserted in the start of frame delimiter in an arbitrary order, and then the packet is transmitted.

Abstract: A method and apparatus for transmitting a packet in a wireless communications network is presented. A packet is constructed to include synchronization header, a physical layer header, and a payload. A preamble and a start of frame delimiter is inserted in the synchronization header. Multiple pairs of cores and of suffixes are inserted in the start of frame delimiter, and then the packet is transmitted.

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

Abstract: A method analyzes a set of signal acquired from a physical system. A set of parameters characterizing the set of signals is measured. The parameters can include the mean and the variance of the power of the signal, and a Rician factor. A first point and a second point of a moment generating function for a combination of the set of signals are evaluated according to the set of parameters to obtain a first sample and a second sample, respectively. First and second equations are defined. The equations respectively have an approximation of a moment generation function of a lognormal random variable representing the combination of the set of signals, at the first point and the second point, on the left side, and the first and second sample on the right side. The two equations are solved to obtain a mean and a variance of the lognormal random variable representing a distribution of the combination of the set of the signals.

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 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.