Abstract: A system for bidirectional communication of digital data between a central unit and a remote unit wherein the need for tracking loops in the central unit has been eliminated. The central unit transmitter generates a master carrier and a master clock signal which are used to transmit downstream data to the remote units. The remote units recover the master carrier and master clock and synchronize local oscillators in each remote unit to these master carrier and master clock signals to generate reference carrier and clock signals for use by the remote unit receiver. These reference carrier and clock signals are also used by the remote unit transmitters to transmit upstream data to the central unit. The central unit receiver detects the phase difference between the reference carrier and clock signals from the remote units periodically and adjusts the phase of the master carrier and master clock signals for use by the central unit receiver to receive the upstream data.

Abstract: A method and apparatus for implementing a subchannel for management and control or other supplemental data on a media shared with a high speed data link. Several FDMA approaches are disclosed including AM, FM, PM, phase, QAM, QPSK etc. modulation of a subcarrier having a frequency which is in the bandwidth provided by the shared media which is not used by the DC balanced high speed data stream. A preferred species which is compatible with existing high speed data transmitters and receivers comprises a subchannel transmitter which frequency shift keys a subchannel carrier of about 1 mHz with the subchannel data. The modulated subchannel carrier is summed by superposition with a DC balanced NRZ format gigabit data stream and coupled onto the media.

Abstract: A data processing system implements a security protocol based on processing data in packets. The data processing system comprises processing packets for storing filter code and processing data packets according to stored filter code, and a policy managing function for generating filter code and communicating generated filter code for packet processing. The packet processing function is arranged to examine, whether the stored filter code is applicable for processing a certain packet. If the stored filter code is not applicable for the processing of a packet, the packet is communicated to the policy managing function, which generates filter code applicable for the processing of the packet and communicates the generated filter code for packet processing.

Abstract: A learning half bridge and bridge for a Fibre Channel Arbitrated Loop and switching protocol. A half bridge can be coupled to a local loop segment and a remote loop segment. The half bridge includes transmit and receive ports implementing predetermined switching and conflict resolution rules and a memory storing a forwarding table. Typically the switching rules are implemented using state machines. The state machines implement a switching protocol that controls transitions between states which control switching connections, writing of data to memory and reading of data from memory and preemption of conflicting OPN primitives. Each half bridge includes a local return segment that can be switched by the state machines to bypass the remote loop segment if both the source node and destination node are on the local loop segment so as to make the local loop segment a complete Fibre Channel Arbitrated Loop.

Abstract: A bidirectional digital data communication system which generate phase coherent upstream clock and carrier signals from recovered downstream clock generated from a master clock in a central unit. The preferred species uses any downstream clock rate and generates a phase coherent upstream clock so long as the two clock rates can be related by the ratio M/N where M and N are integers. One embodiment uses an MCNS downstream and an SCDMA upstream and uses MNCN timestamp messages in the downstream to achieve an estimate of RU frame offset prior to establishing frame alignment using a ranging process. The use of timestamp messages to estimate the offset is aided by a low jitter method for inserting timestamp messages by avoiding straddling of MPEG packet headers with the sync message. Clock slip is detected by counting upstream clock cycles over a predetermined downstream clock interval and the RU transmitter is shut down if slip is detected to prevent ISI interference from misaligned codes.

Abstract: A series of police doppler single mode radars and a multimode police doppler radar, all with direction sensing capability are disclosed. A quadrature front end which mixes received RF with a local oscillator to generate two channels of doppler signals, one channel being shifted by an integer multiple of 90 degrees in phase relative to the other by shifting either the RF or the local oscillator signal being fed to one mixer but not the other. The two doppler signals are digitized and the samples are processed by a digital signal processor programmed to find one or more selected target speeds. Single modes disclosed are: stationary strongest target; stationary, fastest target; stationary, strongest and fastest targets; moving, strongest, opposite lane; moving, strongest, same lane; moving, fastest, opposite lane; moving, fastest and strongest, opposite lane; moving, fastest, same lane; moving fastest and strongest, same lane.

Abstract: An apparatus for accelerated Fiber Channel protocol handshaking and data exchange involves dividing a Fiber Channel arbitrated loop architecture up into a plurality of arbitrated subloops, each of which arbitrates locally using the same fundamentals as the Fiber Channel arbitration protocol but with some slight modifications which do not affect the compatibility of standard Fiber Channel nodes. Each subloop is coupled to a hub port which contains a state machine which implements distributed intelligence to do switching function and fill word generation to implement the accelerated protocol by using a plurality of switching, fill word generation and token passing rules. The state machine in each hub port is coupled to its local subloop and to its neighboring hub ports through a single TDMA bus which has timeslots dedicated to carrying broadcast loop and return loop traffic and control token traffic.

Abstract: A process for reducing the amount of overhead data in ATM cell headers prior to transmission both upstream and downstream on an HFC cable plant or other transmission media using SCDMA on at least the upstream path, without loss of either IP or Ethernet addressing information. A virtual link between each remote unit and a central unit is established using multiplexing to establish a virtual link to every remote unit. Downstream ATM cells are optimized by stripping off all but 2 bytes to leave a 50 byte cell. Incoming IP packets have their IP addressing information used to look up Ethernet domain address information for the RU and destination process to which this RU is coupled. An Ethernet header is appended to each IP packet as is RFC 1483 bytes to signal the start of the packet. The packet is parsed into 48 byte ATM cell payloads. VPI/VCI information for the virtual link of the remote unit to which the packet is bound is looked up using the Ethernet address information.