Abstract: An apparatus for and a method of simulating the functionality of the gatekeeper in a LAN telephony system. The gatekeeper simulator of the present invention enables tester personnel to manually control the behavior of the gatekeeper and its environment. The gatekeeper simulation platform utilizes a commonly available computing platform such as a personal computer (PC) adapted so as to have a LAN connection interface such as a commonly available Network Interface Card (NIC), IP communication stack and an H.323 protocol stack. A gatekeeper simulation software application runs over the IP communication stack and H.323 protocol stack which together constitute a LAN telephony platform. The gatekeeper simulator is adapted to simulate any desired request supported by the H.323 protocol suite. In addition, it is adapted to simulate all possible responses to a request as well. Further, it is adapted to simulate the responses selectively and individually for each specific user in the network.

Abstract: A digital subscriber line access multiplexer (DSLAM) adapted for use with an Ethernet over Very High Speed Digital Subscriber Line (VDSL) transport facility. The DSLAM connects to a plurality of CPE devices on one end and to a high speed Ethernet link on the other. The DSLAM is adapted to receive HDLC protocol formatted VDSL frames, extract Ethernet frames therefrom and generate standard Ethernet signals for transmission overran Ethernet connection. Standard Ethernet frames are received from a Fast Ethernet input signal and encapsulated in HDLC frames for transmission over the VDSL facility to a particular CPE. The voice signal from a conventional telephone set is combined with the VDSL data signal. The combined signal is split at the DLSAM into separate voice and data signals. The Ethernet frame data is extracted from the HDLC frames and input to the Ethernet switch. The voice signal is forwarded to a conventional PBX.

Abstract: A novel robust communications scheme whereby a repetition code at the transmitter and an associated cumulative decoder at the receiver are used to increase the reliability of transmission in a communications system. The robust communications scheme of the present invention is effective to increase the reliability of transmission by repetitively transmitting each data segment a number of times in accordance with a repetition code and subsequently collecting the received energy at the receiver over an accordingly longer period of time. Accumulating the received energy over a longer period of time at the receiver, yields a marked improvement in the signal to noise ratio (SNR) of the receiver.

Abstract: A novel and useful dynamic packet filter that can be incorporated in a hardware based firewall suitable for use in portable computing devices such as cellular telephones and wireless connected PDAs adapted to connect to the Internet. The invention performs dynamic packet filtering on packets received over an input packet stream. The dynamic filter checks dynamic protocol behavior using information extracted from the received packet. Sessions are created and stored in a session database to track the state of communications between the source and destination. Recognition of a session is accelerated by use of a hash table to quickly determine the corresponding session record in the session database. Session related data is read from the session database and the received packet is checked against a set of rules to determine whether to allow or deny the packet.

Abstract: A connection mechanism permitting a unidirectional processing device to function as a virtual bi-directional processing device. A pass through dummy connection is inserted in a unidirectional circuit card to permit the connection of standard keyed duplex-paired cables to other processing cards. The use of keyed cables to connect the various circuit cards in a system reduces the burden of a user to manually insure that all cables are properly connected between cards. The pass through dummy connection may be any suitable media such as optical fiber for optical signals or electrical cable, wire or printed circuit board traces for electrical signal.

Abstract: A novel and useful apparatus for and method of automatic gain control (AGC) using Kalman filtering and hysteresis. A nonlinear, time-variant loop filter such as a Kalman filter is employed in the feedback loop of an AGC circuit. The circuit is able to transition quickly and make fast adaptations to new levels of the input signal by use of a restart mechanism used to dynamically modify the gain of the loop filter thus enabling the AGC circuit to quickly adapt to changes in the signal level of the input. An AGC circuit incorporating a hysteresis circuit in the feedback loop is also disclosed.

Abstract: An apparatus for and a method of dynamically prioritizing packets over a packet based network. Packets are dynamically prioritized on the basis of their ‘time to live’ in the network as they travel from one network entity to another. Packets are assigned a priority in accordance with how ‘old’ or ‘young’ they are. Packets with a relatively long time left to live are assigned lower priority then those with relatively little time left to live. A time to live (TTL) field is added to the packet as it travels from one network entity to another. The contents of the time to live (TTL) field represents how ‘young’ or ‘old’ the packet is and conveys the time left before the packet is no longer of any use. Each network entity that receives the packet with a TTL field, subtracts from it the time the packet spends passing through that entity. The field decreases as it hops from network entity to entity until it reaches its destination or is discarded.

Abstract: An apparatus for and method of simultaneously searching an input character stream for the presence of multiple strings. The strings to be searched for are determined a priori, processed and stored in substring tables during a configuration phase. The strings to be searched for are divided into a plurality of two and three character substrings and stored in substring tables. A hash of each substring is calculated and stored in a hash table whose output is an index to a substring table. During searching, the content filter generates the hash of the input character stream and attempts to find a matching substring stored in the hash table. A string is declared found if all the substrings making up the string have been received in correct consecutive order.

Abstract: A forwarding table comprising a combination of a hash table and a content addressable memory (CAM). The forwarding table combines a one way hash table and a small CAM to perform the forwarding information retrieval function. The CAM is used when an address cannot be found in the hash table. When MAC addresses are being added to the forwarding table, they are first tried in the hash table. The address is applied to the hash function and a resulting index input to the hash table. If a hit occurs, it indicates that an entry at that index already exists and a location in the CAM is then allocated for that address. As long as the CAM does not become full, a 100% hit rate is guaranteed. During retrieval, the hash table or the CAM forms the forwarding information output to the next processing stage. If an entry is not found in the hash table, it will typically be found in the CAM. If no entry is found in either, the received frame is flooded to all the ports of the network device.

Abstract: An apparatus for and method of generating soft decision information from a sequence of hard symbol decisions output from a decoder in a concatenated communications receiver. Soft symbol decisions are computed given hard symbol decisions from the equalizer, channel estimation information (i.e. FIR filter taps used to estimate the channel), and the input samples received from the channel. The log likelihood ratio (LLR) for all symbol possibilities is calculated by computing the conditional probability of the input sample sequence given the hard symbol decision sequence. The noise variance is optionally used in computing the soft output values, thus improving the overall performance of the receiver. In one embodiment, symbol vectors are calculated beforehand and stored in a table. An error vector calculator functions to calculate an error vector that is applied to soft output calculation units. Each soft output calculation unit functions to generate a soft output value for a particular symbol candidate.

Abstract: A novel and useful acquisition and synchronization mechanism for spread spectrum communication systems whereby a synchronization sequence comprising a plurality of known symbols spaced apart by predefined time delay intervals is transmitted as the start of packet signal. At the receiver, the received signal is correlated against the synchronization sequence using the predefined gaps or time delay intervals inserted between the symbols. The received signal is linearly correlated to generate a correlation peak for each symbol received. The expected position of each correlation peak is calculated and compared to the positions of the correlation peaks received. If the number of matches exceeds a threshold, synchronization is declared.

Abstract: An apparatus for and a method of remote echo cancellation in a packet based telephony system. Echo cancellation algorithms normally performed on the local end of a connection, are performed instead by the remote end of the connection. Alternatively, the echo cancellation algorithms are performed for both the local and remote ends of a connection on a remote device. In the former case, the remote endpoint estimates the echo function of the local endpoint using audio and timing synchronization data corresponding to the actual audio played at the local endpoint. Using this information, the remote endpoint is able to accurately perform echo cancellation.

Abstract: A system for probing one or more SVCs that enables a network manager station to setup a probe event in advance before a SVC is created. Upon the creation of the SVC, the data is captured and sent to the network management station without any further intervention required. In a first stage, a SVC originator is configured with a probing IE containing parameters to be included in the SETUP request message when SVCs are established. A unique identifier is included as one of the parameters in the probing IE and is used by the probing switch to detect a SVC that is to be probed. A PVC is established to the switch containing one or more SVCs that are to be probed. A probing port is configured on the switch and a range of VPI/VCIs are assigned to the port. A multicast connection is configured in the switch and traffic from the SVC originator is directed toward both the destination and to the probing port. In this fashion, the SVC traffic can be analyzed using diagnostic tools located remotely anywhere on the network.

Abstract: A interleaver/de-interleaver mechanism for reducing the latency of transmitted interleaved codewords. The interleaver/de-interleaver mechanism utilizes a shortened first codeword which functions to offset the interleaving and transmission on subsequent codewords so as to achieve reduced latency depending on the degree of shortening applied. The interleaver/de-interleaver mechanism is particularly useful in power line carrier based systems to reduce the exposure to burst errors by providing interleaving with minimal latency penalty.

Abstract: A dynamic queuing system wherein a single memory is shared among a plurality of different queues. A single memory, termed a queue memory, is by ally shared by one or more queue. The queue memory is divided into a plurality of memory blocks that we initially empty. An empty list functions to track which memory blocks are empty and available for use in a queue. Each queue constructed utilizes one or more memory blocks. When a queue becomes full, an additional memory block is allocated to it. Conversely, as memory blocks of a queue are read, i.e. emptied, they are returned to the pool of empty memory blocks for use by other queued.

Abstract: An apparatus for and a method of interfacing a host to a modem. Data is transferred between the host and the modem via a serial interface. The modem provides the physical layer implementation functions (i.e., transmission and reception functions) in addition to providing low level MAC layer function processing. Functions provided include collision detection, back-off algorithm according to a programmed back-off time, conditional transmission, automatic retransmissions and ACK/NACK packet generation and processing. This serves to eliminate any stringent access timing constraints usually placed on the host processor resulting in reduced cost and complexity of the host.

Abstract: A system for collaborative document annotation whereby notes (i.e. annotations) associated with a document, such as an image or text document, are stored in a notes database on a central notes server. The documents and associated annotations are treated independently from each other whereby separate data structures are created for the documents and for the associated annotations. A web server application on the server side functions to capture requests from one or more note client applications for creating, storing, editing and retrieving annotations related to specific documents stored on the notes server. On the client side, the notes client functions to display the document that the user wishes to annotate and provides the tools necessary to permit the user to create, edit, delete, retrieve and store notes. A synchronization process transmits the annotations generated by the user from the notes client to the notes server.

Abstract: An apparatus for and method of encapsulating Ethernet frames over a Very high speed Digital Subscriber Line (VDSL) transport facility. The VDSL frames are transmitted over a point to point VDSL link where they are subsequently extracted and forwarded as standard Ethernet frames. The VDSL facility transport system comprises an Ethernet to VDSL Customer Premises Equipment (CPE) coupled to a DSL Access Multiplexor (DSLAM) over a VDSL transport facility. The Ethernet to VDSL CPE functions to receive a 10 BaseT Ethernet signal and encapsulate the Ethernet frame into a VDSL frame for transmission over the VDSL facility. The DSLAM is adapted to receive VDSL frames, extract Ethernet frames therefrom and generate and output a standard Ethernet signal. Ethernet frames are encapsulated within VDSL frames and transmitted on the wire pair without regard to the state of the Tx and Rx SOC signals output by the VDSL transceiver.

Abstract: A direct sequence spread spectrum receiver for use in a communication system that utilizes code shift keying (CSK) modulation. Code shift keying modulation transmits data in the form of circularly rotated spreading waveforms such as PN sequences. The data is conveyed in the amount of rotation applied to the spreading waveform before it is transmitted. While tracking, the receiver decodes the received symbols yielding the original transmitted data. The input frequency range of the receiver is divided into one or more frequency bands. For each frequency band, the received signal is filtered, digitized and split into I and Q data streams wherein the Q data stream is delayed by ¼ƒc. Both I and Q data streams are sampled and correlated with an adaptive template. The received data is clocked into a shift register and circularly rotated and a correlation sum is generated. The correlation output of both I and Q channels are summed over all the frequency bands and a maximum correlations is determined.

Abstract: A novel and useful windowing mechanism for reducing the out of band harmonics of an output transmit signal. The windowing mechanism functions to smooth the transition between two consecutive transmit waveforms. The mechanism of present invention is particularly useful in communication systems characterized by consecutively transmitted symbols whereby the concatenation of transmitted waveforms causes discontinuities between symbols. The windowing mechanism is operative to reduce the effect of these discontinuities to reduce out of band harmonics of the transmitted output signal. The windowing mechanism extends each transmit waveform both earlier and later in time thus creating extending waveform portions on either end of the transmit waveform. The extended portions are then multiplied by a suitable windowing function and the result is summed with the next transmit waveform.