Cisco Technology, Inc.

Canadian Auto Preservation Inc.

Red Swan, Inc.

Michael E Lewis

David McClead Theobold

Lu Qian

James A Amos

Mark K Swannie

Mark Swannie

A technique for determining when to change a data rate by determining the cause of packet loss. The technique distinguishes between collision mediated packet loss and poor signal mediated packet loss. Rate shifting to a lower rate is performed after determining poor signals are causing packet loss. After switching to a lower rate, the packet loss rate can be compared to the pre-switch packet loss rate. If the packet loss rate has not improved by shifting to a lower data rate, then the data rate can be shifted to a higher rate. The technique can use a combination of channel response, signal strength, packet loss rate and throughput to determine when to switch data rates. A communication unit can maintain separate histories for each unit it is communicating with and employ a different data rate for each unit.

Data rate shifting methods and techniques

A method and implementation are disclosed for reducing signal distortion. A symbol detector is provided for establishing at least one decision boundary and assigning symbols extracted from a received signal to constellations of symbols separated by the at least one decision boundary. A quality measure implementation is provided for determining an error rate of the output of the symbol detector with respect to the at least one decision boundary. A boundary generator is provided for receiving the error rate and generating parameters that are fed back to the symbol detector to vary the decision boundary positions and shapes, so as to reduce the error rate of the symbol detector.

Method and implementation for adaptive symbol decision mapping

A network management architecture is disclosed having a network backbone and one or more macro service areas. Each macro service area includes one or more basic service areas, which each include an access point and a plurality of associated clients. A management system is employed for connecting the access points to the network backbone. The management system regulates access of the clients to the network so as to control a desired network parameter, which can relate to throughput, quality of service, or any other desired network parameter.

Network management architecture

The present invention generally provides a method for prevention of corrosion in a metal object by inducing a surface current over the entire surface of the metal object. The surface current can be induced by direct or indirect application of electrical waveforms having AC components generated from a circuit. The metal body and the negative terminal of a source of DC voltage (battery) are grounded. The positive terminal of the source of DC voltage is connected to the electronic circuit that imparts electrical waveforms of low voltage DC to the conductive terminal connected to the metal body. Alternate methods of inducing surface currents include direct capacitor discharge through the metal body, or movement of an electromagnetic field over the metal body, or by generating an RF signal attached to a transmitting antenna such that the transmitted signal is received by the metal body.

Method for inhibiting corrosion of metal

The difficulties and drawbacks of the previous-type systems are overcome by the present antenna system, alone and in combination with a wireless access point. The present antenna system includes a plurality of antenna elements for providing a respective plurality of communications signals over a wireless channel. An isolating structure is provided, selectively positioned with respect to the antenna elements, for selective varying signal isolation between the respective antenna elements. In this way, the present system is selectable between a high-throughput/short-range configuration and a low-throughput/long-range configuration.

Configurable antenna for a wireless access point

A method and implementation of wireless communication are disclosed in which wireless signals are exchanged between at least one remote client and a directional antenna array associated with a wireless network, wherein the directional antenna array includes a plurality of antenna elements. A statistical matrix analysis is performed for each of the at least one client and the antenna array, in order to locate angles associated with directions of each client with respect to the antenna array. Values are determined for weighting factors for RF signals of each of the respective plurality of antenna elements, so as to create predetermined phase differences between the signals of the plurality of antenna elements. The predetermined phase differences are used to direct at least one null toward at least one source of interference, so as to avoid signal interference.

Array beamforming with wide nulls

A directional antenna system is disclosed in which a plurality of RF nodes are provided for cooperatively forming a directional antenna array for transmitting and receiving wireless signals between a wireless client at a predetermined position in space. One or more network interface assemblies are provided for exchanging signals between the plurality of RF nodes and a network. Preferably, the plurality of RF nodes are distributed in space with respect to each other and the network interface assembly. The network interface includes a beamformer for applying a plurality of antenna weighting factors to the respective RF nodes, for introducing phase differences in the respective transmitted and received wireless signals that produce a directional steering vector for the wireless signals. In one embodiment of the invention, a processing arrangement is provided for deriving an array manifold, which includes a respective plurality of antenna weighting factors corresponding respectively to distances between each of the plurality of RF nodes, for producing the directional steering vector for the wireless signals. In another embodiment of the invention, a subspace beamforming arrangement is provided for building a covariance matrix from sampled values of a wireless client signal at each RF node, and deriving dominant eigenvectors corresponding to each RF node. The dominant eigenvectors are used as the respective antenna weighting factors for producing the directional steering vectors for the wireless signals.

Wireless LAN with distributed access points for space management

A split access point is disclosed in which an access point controller is provided for management functions of a plurality of wireless clients on a network and one or more media access controls are provided for moving data packets between the network and the wireless clients. One or more radios are provided for communicating with at least one wireless client. In the present invention, one or more of the access point controller, the media access control(s) and the radio(s) are physically separated so as to provide a split wireless access point.

Split access point

A method is disclosed for synchronizing a OFDM signal. The method includes receiving an OFDM signal including a plurality of long and short synchronization symbols, each comprising a plurality of points. The method includes correlating a predetermined number of points in a long symbol of the received OFDM signal against corresponding points in a reference symbol. A correlation peak is obtained between the received long symbol and the reference symbol, wherein the peak occurs at the time when the receiver has clock synchronization.

OFDM receiver clock synchronization system

An apparatus for prevention of corrosion in metal objects uses a capacitively coupled fastener or pad attached to a metal body being protected from corrosion. The metal body and the negative terminal of a source of DC voltage (battery) are grounded. The positive terminal of the source of DC voltage is connected to electronic circuitry that imparts pulses of low voltage DC through the capacitor to the fastener. These pulses of electrical current inhibit the oxidation of the metal object by providing a source of electrons to the oxidizing chemicals in contact with the metal. The electronic circuitry includes a reverse voltage protector to prevent the application of reverse source voltage. The circuitry also includes a power conditioner to supply a constant DC voltage to a microprocessor. The microprocessor generates pulses of DC signals that are amplified by a pulse amplifier and imparted to the conductive facing of the pad. For larger objects, a first and second cable are attached to a metal object. A phase compensated signal is applied to each cable to provide a phase synchronous signal at the metal object. The invention also includes a battery voltage monitor and a power indicator to indicate battery level. When the battery voltage drops below a reference level, the microprocessor senses this low voltage condition and shuts off operation of the pulse amplifier, thereby conserving battery power.

Process and apparatus for preventing oxidation of metal

An apparatus for prevention of corrosion in metal objects uses a capacitively coupled fastener or pad attached to a metal body being protected from corrosion. The metal body and the negative terminal of a source of DC voltage (battery) are grounded. The positive terminal of the source of DC voltage is connected to electronic circuitry that imparts pulses of low voltage DC through the capacitor to the fastener. These pulses of electrical current inhibit the oxidation of the metal object by providing a source of electrons to the oxidizing chemicals in contact with the metal. The electronic circuitry includes a reverse voltage protector to prevent the application of reverse source voltage. The circuitry also includes a power conditioner to supply a constant DC voltage to a microprocessor. The microprocessor generates pulses of DC signals that are amplified by a pulse amplifier and imparted to the conductive facing of the pad. The invention also includes a battery voltage monitor and a power indicator. When the battery voltage drops below a reference level, the microprocessor senses this low voltage condition and shuts off operation of the pulse amplifier, thereby conserving battery power.

Growing community of inventors

Hartville, OH, United States of America

Michael E Lewis