Abstract: A hybrid communication network for a transportation safety system includes a fixed wired nodes and mobile wireless nodes. Because the wired nodes operate independently packets transmitted by the wired nodes to the wireless nodes need to be synchronized. A downlink travel time for downlink packets traveling from a controller to the wireless nodes is determined. Then, the controller schedules downlink data intervals (DDI) based on the downlink travel time; and transmits downlink packets to the wireless nodes during the DDI, such that a latency requirement of the transportation safety system is satisfied.

Abstract: This invention provides a method for jointly optimizing network coding, channel coding, and signal constellations in non-coherent wireless multiple-input multiple-output (MIMO) wireless relay networks for the case when transceivers cannot obtain any knowledge of channel state information (CSI) due to high-speed mobility of the transceivers. In the relay networks, two terminal transceivers simultaneously transmit data to an intermediate relaying transceiver, which in turn broadcasts mixed data using physical-layer network coding to both terminals. The embodiments of this invention exploit different blind space-time trellis-coded modulations (ST-TCM) for each user, whose codebook is jointly generated over a Grassmannian manifold. The method is provided by exponential mapping with affine-lattice convolution for joint optimization of channel coding, modulations, and network coding. The method is designed for fast fading channels with and without interleaving.

Abstract: An encoder in a transmitter uses space-time trellis coding. An input bitstream is multiplexed to produce in parallel a set of output bitstreams. A multiplier applies a code generating weight to each output bitstream, which are combined, mapped and transmitted by a single antenna.

Abstract: A method and an optical receiver compensates for an error in a phase of an optical signal in a receiver. The signal includes blocks of symbols in a sequence. Each block is decoded based on a partially phase compensated symbols, and an average phase error for the block is estimated. Forward phase compensation and backward phase compensation is performed on the block based on the average phase error, and the decoding, estimating, performing is iterated until a termination condition is satisfied to produce a phase compensated block.

Abstract: A method allocates bandwidth to channels in an orthogonal frequency division multiple access and time division multiple access (TDMA) network. The network includes a master device (master) communicating with a set of slave devices (slaves). The master defines a set ?m of logical indices ? of a set of N physical subcarriers for a set of M data streams to be allocated to a set of Nd logical data subcarriers according to ?m={?|?=iM+m, i=0,1,2, . . . , d?1}, where d=Nd/M. The set of N data subcarriers is mapped to the set of Nd logical subcarriers according to the logical indices, and the data subcarriers are allocated to the logical subcarriers.

Abstract: A method reduces time-varying polarization crosstalk due to XPolM by transmitting multi-dimensional orthogonal constellations. Three variants of crosstalk-free constellations are provided: Grassmann constellations, unitary constellations, and rotation codes. The method uses the Grassmann constellations and the unitary constellations to deal with fiber nonlinearity by applying as a polarization-time coding. The rotation codes exploit a fiber channel characteristic to improve performance and to reduce computational complexity. The underlying orthogonality behind those constellations enables the receiver to decode it as if there is no polarization crosstalk. Moreover, the required computational complexity at the receiver is significantly reduced because neither crosstalk cancellers nor channel estimators are needed.

Abstract: A method estimates a wireless channel at a receiver. The signal is transmitted using narrowband orthogonal frequency division demultiplexing (OFDM) and frequency subcarriers, and the signal includes a set of data tones and a set of pilot tones. The channel and pilot tone interference are estimated based on all the pilot tones extracted from the signal and a channel model. The set of data are equalized based on the channel estimate. Data interference is detected according to the pilot interference and the equalized data tones. Subcarrier interference-to-noise ratios are determined based on the data interference. Signal strengths of the data tones are determined based on the equalized data tones, log-likelihood ratios of bits represented by the data tones are determined based on the subcarrier interference-to-noise ratios and the signal strength of the data tones.

Abstract: In a network for a safety system in a transportation system, the transportation system includes a shaft and a car arranged in the shaft. A first wall node is at a first end of the shaft and a second wall node is at a second end of the shaft to communicate safety messages with the car. Each wall node includes at least one wireless transceiver connected to one or more antennas. Each car in the shaft includes at least two wireless transceiver connected to one or more antennas, wherein the first transceiver of the car uses a first frequency and the second transceiver of the car uses a second frequency to communicate each safety messages in duplicate. A wired backbone connects the set of wall nodes to a controller of the safety system of the transportation system.

Abstract: A method reduces time-varying polarization crosstalk due to XPolM by transmitting multi-dimensional orthogonal constellations. Three variants of crosstalk-free constellations are provided: Grassmann constellations, unitary constellations, and rotation codes. The method uses the Grassmann constellations and the unitary constellations to deal with fiber nonlinearity by applying as a polarization-time coding. The rotation codes exploit a fiber channel characteristic to improve performance and to reduce computational complexity. The underlying orthogonality behind those constellations enables the receiver to decode it as if there is no polarization crosstalk. Moreover, the required computational complexity at the receiver is significantly reduced because neither crosstalk cancellers nor channel estimators are needed.

Abstract: In an orthogonal frequency division multiplexing (OFDM) network, a set of pseudo random sequences (PRS) are stored at a transmitter and a receiver. Each OFDM symbol is mapped to subcarriers for a set of transmit antennas to produce a mapped symbol. The mapped symbol is encoded using a pseudo-random phase precoder (PRPP) and the PRS to produce a precoded symbol. An inverse fast Fourier transform (IFFT) is applied to the precoded symbol, and the encoded symbol is transmitted to the receiver using the set of transmit antennas.

Abstract: A set of data symbols is selected from a set of modulation constellation, and a sample-mean of the set of data symbols is determined. Each data symbol is first shifted by the sample-mean to obtain a shifted data symbol, and then the shifted symbol is multiplied by a first constant to obtain a scaled data symbol. A second constant is added to the scaled data symbol to obtain a mapped data symbol. The sample-mean is multiplied by a third constant to obtain a sample-mean mapped symbol. The set of mapped data symbols and the sample-mean mapped symbol are then transmitted as a resource block.

Abstract: A base station transmits a set of sounding requests to a set of mobile station (MS) in a cell, using a set of beams, wherein there is one beam for each sounding request. Qualities of sounding signals transmitted by the set of MSs in response to receiving the sounding request are measured, and the set of MSs are grouped into subsets according to the qualities, wherein there is one subset of MSs associated with each beam.

Abstract: Channel state information for closed-loop transmit precoding in MIMO networks is fed back from the MSs to the BSs. The feedback is quantized using codebooks shared by the MSs and BSs to reduce overhead. The codebooks can be full-rank or rank-one. The quantized feedback is applicable to any definitions of MIMO channel covariance matrix as well as MIMO channel matrix. Since these codebooks are designed for closed-loop MIMO precoded transmissions, no additional memory is needed to store the codebooks at the BS and the MS only for the quantized feedback purposes.

Abstract: Channel state information in a closed-loop, multiple-input, multiple-output wireless networks is fed back from each mobile station to a base station by first determining a transmit covariance matrix R, and applying a singular value decomposition (SVD) R=U?VH, where U, V are left and right singular vector matrices, ? is a diagonal matrix with singular values. The matrix V includes column vectors V. A beamforming vector vmax=[1 exp(j?)exp(j2?) . . . exp(j?)]/?{square root over (N)}] is approximated by the column vector V having a maximum magnitude, where ? is a real number. Then, only the angle ? is fed back using a phase modulation mapping of the components exp(j?) onto the associated subcarrier.

Abstract: In a vehicle ad-hoc network (VANET), a transceiver node is arranged in a vehicle. The node includes a protocol stack, which includes an application layer, a link layer; and a congestion control layer arranged between the application layer and the link layer. The congestion layer transfers short messages between the application layer and the link layer. The short messages are defined according to a standard for the VANET, and the congestion layer optimizes a network-wide rate allocation for the short messages.

Abstract: This invention provides a method for jointly optimizing network coding, channel coding, and signal constellations in non-coherent wireless multiple-input multiple-output (MIMO) wireless relay networks for the case when transceivers cannot obtain any knowledge of channel state information (CSI) due to high-speed mobility of the transceivers. In the relay networks, two terminal transceivers simultaneously transmit data to an intermediate relaying transceiver, which in turn broadcasts mixed data using physical-layer network coding to both terminals. The embodiments of this invention exploit different blind space-time trellis-coded modulations (ST-TCM) for each user, whose codebook is jointly generated over a Grassmannian manifold. The method is provided by exponential mapping with affine-lattice convolution for joint optimization of channel coding, modulations, and network coding. The method is designed for fast fading channels with and without interleaving.

Abstract: A method optimizes a performance of a multi-cell orthogonal frequency-division multiple access (OFDMA) network that includes a set of base stations (BSs) located in a cell, and each BS transmits data on downlink channels to a set of mobile stations (MSs) in the cell. Each BS acquires channel state information (CSI) and inter-cell interference information (ICI) for each downlink channel to each MS in the cell. Each BS selects a power level and a modulation coding scheme level (MCS) for transmitting the data to each MS on the downlink channels based on the CSI and ICI, such that a bit rate is maximized and the ICI is minimized. Then, time and frequency resource are allocated for transmitting the data on the downlink channels to the set of MSs, such that the allocated resources are minimized to optimize the performance of the network.

Abstract: A network includes a master node (master) and a set of slave nodes (slaves). The network uses orthogonal frequency-division multiplexing (OFDM) and time division multiple access (TDMA) symbols on sub-carriers. During a first downlink transmission from the master to the set of slaves using downlinks and all of the sub-carriers, a broadcast polling packet including data packets for each slave and sub-carrier assignments for the slaves is broadcast. Each slave transmits simultaneously to the master using uplinks and the assigned sub-carriers, a first response packet after receiving the broadcast polling packet. The master then broadcasts using the downlinks and all of the sub-carriers, a group acknowledgement packet, wherein the broadcast polling packet, the response packet, and the group acknowledgement packet include one superframe in one communication cycle, and wherein the broadcasting on the downlinks and the transmitting on the uplinks are disjoint in time.

Abstract: A method estimates a wireless channel at a receiver. The signal is transmitted using narrowband orthogonal frequency division demultiplexing (OFDM) and frequency subcarriers, and the signal includes a set of data tones and a set of pilot tones. The channel and pilot tone interference are estimated based on all the pilot tones extracted from the signal and a channel model. The set of data are equalized based on the channel estimate. Data interference is detected according to the pilot interference and the equalized data tones. Subcarrier interference-to-noise ratios are determined based on the data interference. Signal strengths of the data tones are determined based on the equalized data tones, log-likelihood ratios of bits represented by the data tones are determined based on the subcarrier interference-to-noise ratios and the signal strength of the data tones.

Abstract: A hybrid communication network for a transportation safety system includes a wired network including a set of fixed nodes. Each fixed node includes a wired interface for connecting the fixed node to the wired network and at least one wireless interface. The set of fixed nodes further includes a head node at a first end of the wired network connected to a controller, a terminal node at a second end of the wired network, and a set of relay nodes arranged between the head node and the terminal node. A wireless network includes a set of mobile nodes and a set of fixed nodes connected to the wired network. Each mobile node includes at least one of the wireless interfaces, and each mobile node is arranged in a moveable car.