Proxim Corporation

Hewlett-packard Company

Juan G Grau, Jr

Linh Tien Truong

Arthur B Coleman

Richard A Nyquist

Andrew H Naegeli

Jeff R Sutton

Brian S Messenger

Roaming capability is provided to mobile computers within a standard network such as a Novell network. In a computer network running under a network operating system that provides for fault-tolerant internet routing of network communications between nodes and requires that network ID of a node remain constant for the duration of session, the nodes include multiple mobile computing devices wirelessly connected to the network. The mobile computing devices are provided with the capability to roam during a session by changing access points to the network. This capability is provided by programming the mobile computing devices so as to appear to the network as routers able to change access points during a session. The routers connect one sub-net to one other sub-net, the one sub-net being connected to a mobile computing device and having a fixed network ID and the other sub-net, through fault-tolerant internet routing being connected to a selectable access point and therefore having a variable network ID. The resulting workstation/routers may be termed virtual routers in that they connect a purely logical sub-net having a fixed network ID but no physical instantiation to exactly one other sub-net.

Providing roaming capability for mobile computers in a standard network

A digital radio transceiver uses a differential 4-ary frequency shift keying (D4FSK) modulation scheme to achieve a radio that is low cost, miniaturizable, low in power consumption, and high in spectral efficiency. An adaptive digital 'slicer' looks at a digitized FM video signal produced in the receiver to determine if the data sent is a 00, 01, 10 or 11. The digitized FM video signal is first processed by a differential decoder, the output of which is input to a peak detector. The peak detector outputs a signal upon the occurrence of a three-step transition, i.e., a peak-to-peak voltage value. Two-step and three-step transitions are separately detected and used to perform digital clock recovery. A carrier detect circuit uses a digital bit filter to produce a carrier detect signal that is reliable and glitch-free. The digital radio transceiver uses frequency hopping spread spectrum transmission. A switchable loop bandwidth frequency synthesizer provides for glitch-free switching between a wide hopping bandwidth and a narrow bandwidth between hops.

Digital communications equipment using differential quaternary frequency

A spread spectrum radio communication system includes a generator for generating a pseudo-random chipping sequence, a frequency spreader for combining digital data with the pseudo-random chipping sequence to produce a spread spectrum signal, a modulator for modulating the spread spectrum signal for broadcasting over a predefined frequency band, a demodulator for demodulating broadcast spread spectrum signals, a de-spreader that employs single bit quantization and oversampling for digitally correlating the output of the demodulator means with a pseudo-random chipping sequence, and an extractor for extracting clock and data signals from the output of the de-spreader. The chipping sequence is normally selected from a set of codes including an eleven-bit Barker code, its inverse and reversals of the inverse and non-inverse code.

Radio communication system using spread spectrum techniques

A vector analyzer incorporates a set of five types of markers for the display, which facilitate the visual analysis of the magnitude, phase and time relationships of the I and Q components of the modulation states displayed. The five markers are: an I marker, a Q marker, a magnitude marker, a phase marker and a time marker. The I and Q markers indicate amplitude in the I and Q coordinates displayed on the X-Y displays. The magnitude marker indicates amplitude on the radial coordinate of the X-Y displays. The phase marker indicates relative phase on the angular coordinate of the X-Y displays. The time marker indicates the time coordinate on the displays, and controls the time instant displayed. The analyzer also incorporates a circuit for performing linear transforms on the I, Q, and time data which allows real time adjustment of the sampled signals and enables the signals to be displayed in a three dimensional projection mode. The linear transform can be used to correct the display for three common sources of error in vector modulated signals: amplitude imbalance, phase errors, and quadrature errors. After the display has been corrected, the correction factors are a measure of the errors in the input signal, or in the device demodulating the input signal.

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San Mateo, CA, United States of America

Juan G Grau, Jr