A routing method for supporting ad-hoc mobile communications within a radio communications network. The network comprises a plurality of mobile hosts including a source mobile host and a destination mobile host, and a plurality of radio communications links connecting together with mobile hosts. The method comprises measuring the stability of the communications links between neighbouring mobile hosts using an associativity based characteristic and selecting a communications route through the network from the source mobile host to the destination mobile host based on the stability of the communications links. The associativity characteristic is measured by each mobile host periodically transmitting and receiving identifier beacons (ticks) and updating the status of its corresponding links. The greater the number of ticks associated with a given link, the greater its stability. Use of the associativity characteristic enables the routing method to deal efficiently with mobile host migrations throughout the network.

Routing method for Ad-Hoc mobile networks

In wireless local area networks utilizing frequency-hopping between different channels spaced over an allotted frequency band, two or more groups of transceivers in close proximity may be arranged to operate satisfactorily with the full bandwidth available to each by arranging that their hop sequences are kept separate. This may be achieved by arranging for the hop sequence of one group or of each group to skip at intervals from one point to another in the sequence, chosen at random.

Wireless local area networks

A disclosed method tunes a signal from a channelized spectrum having a predetermined channel spacing. A signal of interest having a predetermined maximum bandwidth is mixed with a local oscillator signal, which has a frequency that is an integer multiple of the channel spacing or one-half of a channel spacing displaced from an integer multiple of the channel spacing. The local oscillator signal is selected to frequency translate the signal of interest to within a near-baseband passband whose lower edge is spaced from DC by at least about the maximum bandwidth of the signal of interest. Problems associated with 1/f noise, DC offsets, and self-mixing products are avoided or substantially diminished. Other methods and systems are also disclosed.

Simplified high frequency tuner and tuning method

A wireless local area network (WLAN) provides optimal data throughput by operating at multiple data rates simultaneously. The WLAN includes a network master communicating with a plurality of remote client transceiver nodes. The network master maintains a table of active client transceiver nodes. The table includes a current data rate for each of the active client transceiver nodes. Periodic high-speed and low-speed beacon signals are transmitted from the network master to the active client transceiver nodes. Each of the active client transceiver nodes receives and processes the beacon signals to determine an optimal data rate. Then, each of the active client transceiver nodes transmits a return signal to the network master which designates the determined optimal data rate. Thereafter, the network master updates the table to reflect the optimal data rate for each of the active client transceiver nodes. Subsequent messages from the network master to the active client transceiver nodes are thereby transmitted at the current data rate for each respective one of the active client transceiver nodes.

Concurrent multiple data rate communications in a wireless local area network

Wireless local area networks (“wireless networks”) used to interrelate individual mobile nodes, and having the capability of automatically establishing and/or modifying functionality of a network in response to the characteristics and/or identity of the nodes connected to the network at a given time. The wireless networks may be mobile, and may be employed in applications using service vehicles, such as truck, skid and trailer mounted equipment used in the well servicing industry, delivery or maintenance trucks, railroad service vehicles, aircraft, or off-shore service vehicles.

Wireless network system

A method for use in a single cell of a wireless communication system of the type having a leader station that coordinates communication among a plurality of remote stations that are in the cell. The method applies to systems that use slow frequency-hopping radios and a Carrier Sense Multiple Access (CSMA) type protocol. In this context, the method allows a remote station to initially acquire the frequency-hopping pattern and time base of the leader station and to maintain frequency synchronization in the face of control information loss due to radio transmission effects (e.g., interference, noise or multipath fading). In the acquisition phase, the remote station actively generates probe messages that are sent to the leader station so as to rapidly achieve frequency synchronization with the leader station.

Robust frequency management and acquisition in a wireless local area network that uses frequency-hopping radios

An apparatus and a method for detecting a carrier signal of a phase shift keyed modulated signal. A first counter circuit generates a plurality of counts, with each count being a number of cycles of a reference frequency signal occurring between two consecutive rising edges of an intermediate frequency signal. A comparison circuit compares a first count of reference frequency cycles to a second count of reference frequency cycles when a difference between an initial count of reference frequency cycles and a first predetermined number is less than a second predetermined number. The first predetermined number represents a time period of one cycle of the nominal center frequency, and the first count and the second count respectively represent time periods of first and second cycles of a pair of consecutive cycles of the intermediate frequency signal. The comparison circuit generates a difference signal when a difference between the first count and the second count is less than a third predetermined number. A second counter circuit counts cycles of the intermediate frequency signal and generates a carrier detect signal when a count of the intermediate frequency signal cycles equals a fourth predetermined number.

Digital delta mode carrier sense for a wireless LAN

A phase shift modulator at the transmitter has a control input connected to a binary signal source. A high frequency carrier signal is applied to a carrier signal input of the modulator. The modulated carrier signal is transmitted to a receiver where it is mixed with a local oscillator frequency. At the receiver, a modulated signal is amplified by a limit amplifier to form the received signal into square wave pulses of a uniform height. The demodulator detects when the spacing between the edges of the square wave signal change in response to the phase shift modulation at the transmitter. When the spacing between the edges of the square wave IF signal is detected to be shorter than the normal spacing for a steady IF signal with no modulation, this signifies a first binary value. A longer than normal spacing between the edges of the square wave IF signal signifies a second binary value. Frequency drift compensation circuits are disclosed to overcome frequency variations in the carrier and the local oscillator.

Phase demodulation method and apparatus for a wireless LAN, by counting the IF period

A control system for the carriage drive of a line printer includes a microprocessor which controls a carriage drive stepper motor through programmable timers and interface adapter along with other non-print units of a printer mechanism. A control counter in the carriage drive responsive to feedback pulses from the stepper motor coacts with the timers to control various operation of the stepper motor during line feeding of a print medium and is used by the microprocessor for preventing loss of control of the carriage drive due to interrupts from other devices.

Printer system having microprocessor control

A printer system comprising a belt printer mechanism controlled by a stored program digital microprocessor to print lines of data on a print medium. Selective operation of a linear array of print hammers, paper feeding, data conversion and arranging in scan/subscan order are performed by the microprocessor. The fire data for operating hammers is precalculated and arranged in scan/subscan order during the print medium feeding interval with printing occurring immediately at the first print scan after print medium motion in which one or more desired characters become aligned with print hammers. An indirect addressing technique which eliminates sorting is used to arrange the print position fire data in scan/subscan order.

Arthur E. Fleek

Papers

Robust frequency management and acquisition in a wireless local area network that uses frequency-hopping radios

Digital delta mode carrier sense for a wireless LAN

Phase demodulation method and apparatus for a wireless LAN, by counting the IF period

Printer system having microprocessor control

Line printer system and method of operation with microprocessor control