Abstract: A method is disclosed for signal detection in a wireless communication system that includes multiple-antenna arrays for transmission and reception. The method involves multiplying a vector of signals collected from respective receiving antennas by a nulling vector, such that the resulting vector product provides an estimated value corresponding to a specific one of the transmitted signals. A respective such multiplication is performed to detect each of the transmitted signals. In contrast to related methods of the prior art, each nulling vector is obtained from a channel matrix of estimated channel coefficients without performing any matrix inversion operations, and only a single pseudoinverse related to the channel matrix is computed. As a result, numerical stability is improved and the computational complexity of the method is reduced by an order of magnitude relative to methods of the prior art.

Abstract: A new scheduling discipline is disclosed for the forward link of a wireless network such as a CDMA network. The new discipline, which we denominate Modified LWDF (M-LWDF), resembles the known LWDF discipline in that only one queue is served at a time, and the queue to be served is that having the largest weighted delay.

Abstract: An interferometric system includes first, second and third optical fibers with first and second couplers. The first coupler is configured to receive radiation through the first fiber, provide a first radiation portion through the second fiber and provide a second radiation portion through the third fiber to the second coupler. The system also includes fourth and fifth optical fibers each configured to receive radiation from the second coupler and transmit radiation for receipt by the other.

Abstract: We disclose a method of dynamic channel assignment for wireless transmission systems that employ time or frequency multiplexing, or both time and frequency multiplexing. The invention is specifically addressed to the problem of avoiding interference in the channels of such systems. In a broad aspect, the invention involves partitioning base stations of a network into non-interfering sets. Channels are allocated to the non-interfering sets according to need. Stages of channel reallocation take place periodically. The reallocation takes place through coordinated activity by the base stations. That is, the channel reallocation is carried out in response to information that is exchanged between base stations, or it is centrally directed by the network in response to information passed to the network by the base stations.

Abstract: We describe a method for CDMA transmission of sets of data symbols to users that are organized into one or more user groups. Each user group is paired with a group of spreading codes, referred to as a “code group.” Each set of data symbols that are destined for respective users of a given user group is transmitted in the form of two or more distinct signal sequences. Each such signal sequence is transmitted from a respective one of two or more transmitting antennas. Each signal sequence is a linear combination of spreading code sequences belonging to the corresponding code group. Within each of these linear combinations, each spreading code sequence that appears has a scalar coefficient. Each of these scalar coefficients is a linear combination of pertinent data symbols (i.e., data symbols destined for users in the given user group) or of complex conjugates of pertinent data symbols.

Abstract: Our method of making high bandwidth silica-based multimode optical fiber comprises provision of a non-circular preform, and drawing fiber of chiral structure from the preform. The non-circular preform can be made by maintaining the inside of the tubular preform under reduced pressure during at least part of the collapse, resulting in a non-circular core and cladding. It can also be made by removal (e.g., by grinding or plasma etching) of appropriate portions of the preform, resulting in a circular core and non-circular cladding. In the latter case, fiber is drawn at a relatively high temperature such that, due to surface tension, the cladding assumes substantially circular shape and the core assumes a non-circular shape. The chiral structure is imposed on the fiber in any appropriate way, e.g., by twisting during fiber drawing the fiber alternately in clockwise and couterclockwise sense relative to the preform.

Abstract: We disclose a method for routing a set of demands in a ring network that comprises nodes interconnected by directed links, in which each demand may be routed clockwise or counterclockwise. According to our method, a linear program is solved to obtain a set of routing variables that minimize an objective function. Each routing variable corresponds to a respective one of the demands, and has a value, exemplarily, on the closed interval from 0 to 1. A value of 1 signifies, e.g., clockwise routing, and a value of 0 signifies counterclockwise routing. The objective function describes the value of a load, defined on each link and maximized over all links of the network, so that a solution of the linear program provides a minimum value of the maximized load. The method further comprises rounding the routing variables so that the value of each routing variable falls at 1 or 0. This rounding is carried out such that the maximized load does not exceed the previously-obtained minimum value of the maximized load.

Abstract: There is disclosed a method for processing a time-varying signal to produce a high-resolution spectrogram that represents power as a function of both frequency and time. Data blocks of a time series, which represents of a sampled signal, are subjected to processing which results in a sequence of frequency-dependent functions referred to as eigencoefficients. Each eigencoefficient represents signal information projected onto a local frequency domain using a respective one of K Slepian sequences or Slepian functions. The spectrogram is derived from time- and frequency-dependent expansions formed from the eigencoefficients.

Abstract: An optical attenuator having a structure in which a membrane covers a cavity formed on a substrate is disclosed. The membrane covering the cavity formed in the substrate is movable relative to the bottom surface of the cavity constituting a deformable mirror. Movement of the membrane relative to the bottom surface of the cavity attenuates optical signals impinging on the surface thereof. The movement of the membrane relative to the bottom surface of the cavity attenuates impinging optical signals by controlling the angle at which such impinging optical signals are reflected from the membrane surface.

Abstract: In a system for sending wireless communication signals on at least one downlink wavelength and receiving wireless communication signals on at least one uplink wavelength, there is a ratio r equal to the larger divided by the smaller of these wavelengths. The system comprises a receiver operative to receive signals imposed on a carrier having the uplink wavelength, a transmitter operative to transmit signals imposed on a carrier having the downlink wavelength, and an array of independent antenna elements. The array comprises a first and a second sub-array. One sub-array is electrically coupled to the transmitter, such that transmitted signals can be radiated from it, and the other sub-array is electrically coupled to the receiver, such that signals to be received can be extracted from it. The sub-arrays are geometrically similar to each other with a relative scale factor equal to the wavelength ratio r. The sub-arrays have at least one common antenna element.

Abstract: We describe a method for solving the joint problem of optimal routing and optimal bandwidth allocation in a network that supports plural subnetworks and plural communication services. Our method involves, for each source-destination pair communicating via a given subnetwork and a given class of service, determining a traffic rate to be offered to each of a set of permissible routes between that source and that destination, in the given subnetwork and service class. Our method further involves allocating a respective bandwidth to each link of each subnetwork. Significantly, the determinations of traffic rate to be offered, and the allocations of bandwidth to respective links of subnetworks, are performed in a mutually responsive manner.

Abstract: Disclosed is a modulation method for wireless signal transmission. Each message that is transmitted is made up of a sequence of signals, each selected from a constellation of L such signals, L a positive integer. Each transmitted signal is distributed spatially across a transmitting antenna array, and is also distributed in time. Thus, each signal may be represented as a T×M matrix, in which each of the M columns represents a distinct antenna of the array, and each of the T rows represents a distinct time interval. Each entry in this matrix represents a complex baseband voltage amplitude. Each of these signal matrices is proportional to a matrix having orthonormal columns.

Abstract: In an optical communication system, the signal power level injected into each of one or more optical fiber spans is reduced so as to suppress undesired non-linear effects. This reduction in injected signal level is made possible by remotely pumped amplification in the spans that are affected.

Abstract: Problems of fading in a multi-path environment are ameliorated, and the presence of reflective surfaces is turned from a disadvantage to an advantage, by employing a third polarization direction that effectively creates a third communication channel. This third communication channel can be used to send more information, or to send information with enhanced spatial diversity to thereby improve the overall communication performance. A transmitted signal with three polarization directions is created with a transmitter having, illustratively, three dipole antennas that are spatially orthogonal to each other. A received signal having energy content in three polarization directions is detected by a receiver having, illustratively, three dipole antennas that are spatially orthogonal to each other.

Abstract: We describe an improved method for decreasing the probability of an unacceptably high peak-to-average power ratio in a signal to be transmitted by a Frequency Division Multiplexing (FDM) system, such as a discrete multitone (DMT) system. The method involves generating at least two alternative signal sequences, computing Fourier transforms of the respective alternative signal sequences, and selecting for transmission one of these sequences, based on the Fourier transform computations. More specifically, the selection of one sequence may be based, e.g., on the determination that the Fourier transform of that sequence has an acceptable peak power. Alternatively, a comparison may be made among the Fourier transforms of the respective signal sequences, and selection made of that sequence whose Fourier transform exhibits the lowest peak power.

Abstract: The present invention relates generally to the field of optical communication and particularly to optical communication techniques which compensated for dispersion such as that in optical fibers. Compensation of optical dispersion is achieved with a polarization beam splitter with first, second and third ports, a dispersion compensating fiber, a first return means that changes the mode of polarization of a returned signal and a second return means. One end of the dispersion compensation means is connected to the third port of the polarization beam splitter, the other end is connected to the first return means. The second return means is connected with the second port of the polarization beam splitter, while the first port of the polarization beam splitter forms input and output. As the signal passes through the dispersion compensating fiber four times, the length of the dispersion compensating fiber can be greatly reduced.

Abstract: Apparatus and method are provided for detecting vehicles which are moving through a predetermined zone. The apparatus includes a plurality of acousto-electric transducers trained on the zone. A bandpass filter is provided for processing electrical signals from the plurality of acousto-electric transducers. A correlator having at least two inputs and an output is provided for correlating filtered versions of the electrical signals originating from at least two of the plurality of acousto-electric transducers. An integrator is provided for integrating the output of the correlator means over time. Finally, a comparator is provided for indicating detection of a vehicle when the integrated output exceeds a predetermined threshold.

Abstract: A 16B/18B low disparity code is described. The 16-bit input word is split into two bytes, i.e., into two 8-bit words, and each byte is mapped to a 9-bit word. The image of each input byte under the mapping depends at least in part on its disparity, and also in some cases on the disparity of the other word. Certain of the images under the mapping are then inverted. The decision whether to invert an image depends, at least in part, on the running digital sum (RDS) of the output. The RDS is the sum of all 1's in the data stream from its beginning (or from a designated starting point). Significantly, all possible input words are grouped, by disparity, into four categories. The rule for mapping of input words is different for each of the four categories.

Abstract: A system is disclosed for displaying information pertaining to the usage of Web pages. The system comprises first and second Web sites. The first Web site comprises plural Web-component files, each having a name in a Web-site directory. The second Web site comprises plural statistics files, each containing usage information about a corresponding Web-component file or sub-directory of Web-component files. The system further comprises a computing device that has a display screen, is operable by a user, and is in communication with the first and second Web sites. The computing device is operated under the control of Web-browser software effective for displaying, on the screen, Web components of the respective Web sites.

Abstract: A method of admitting and routing switched virtual circuit requests in a network first finds a set of routing paths on which a requested VC may be routed by using a two step process. The method uses a cost function based on a parameter related to the number of hops in a subset of VC connections previously made in the network to determine potential routing paths on which the VC can be routed at a cost below a specified threshold. The method next checks to determine which potential routing paths comprise links and nodes with sufficient resources to accommodate the request. Paths satisfying both steps are output as a set of routing paths and then a second criterion is used to select a path from the set on which to route the request. In a distributed routing system, the inventive method uses a local network state to determine the cost function and the set of routing paths.