Abstract: Secure communication protocols are disclosed in which two parties generate a shared secret which may be used as a secure session key for communication between the parties. The protocols are based on Diffie-Hellman type key exchange in which a Diffie-Hellman value is combined with a function of at least a password using the group operation such that the Diffie-Hellman value may be extracted by the other party using the inverse group operation and knowledge of the password. In one embodiment, each of the parties explicitly authenticates the other party, while in another embodiment, the parties utilize implicit authentication relying on the generation of an appropriate secret session key to provide the implicit authentication. Typically, the parties will be a client computer and a server computer.

Abstract: A method and apparatus for resolving floating point and integer ambiguities in a satellite position navigation system is disclosed. A rover station is periodically positioned at unknown locations and has a satellite receiver capable of receiving the navigation signals. By calculating relative position coordinates between a base station in a known location and the rover station, and by calculating other position parameters relative to the satellite position, a geometric constraint based on a measured elevation angle between the rover and base station can be incorporated into data computations and processing to help resolve carrier phase ambiguities. The elevation angle is measured by transmitting multiple laser beams to an optical sensor on the rover station. This technique results in greater precision in determining the location of the rover.

Abstract: Wireless devices within an ad-hoc wireless network adaptively set their transmission power levels based on locally available information. Initially, each such wireless device sets its transmission power level to a relatively low level, and gradually increases its power level up to a predetermined maximum transmission power level. As the transmission power increases, the wireless device is able to incrementally connect with additional wireless devices located at increasing distances from the wireless device. As the wireless device connects with these additional wireless devices, it checks a connectivity constraint. When the connectivity constraint is satisfied, the wireless device stops increasing its power and operates at its current power level. In one embodiment, the connectivity constraint is a geometric connectivity constraint based on the angular distribution of wireless device connections.

Abstract: Disclosed is a method and apparatus for multipath mitigation using an antenna array. An antenna array made up of a plurality of antennas is used to receive satellite signals from satellites. Various configurations of antenna arrays is disclosed, including a linear vertical antenna array and a horizontal antenna array in which the antenna elements are located in a horizontal plane. A switch sequentially connects each of the antenna outputs to a single processing path to generate a common additive signal. The common additive signal is provided to satellite channel processors, each of which processes the signals from an associated satellite. A phase shift correction signal associated with each of the antennas is generated and synchronously applied to a carrier phase reference signal. A blocking signal may be applied to the satellite channel processors in order to block the processing of signals from an unwanted satellite.

Abstract: A method and apparatus for detecting and correcting anomalous measurements in a satellite navigation receiver is disclosed. Anomalous measurements are detected using the redundancy of observed satellite signals, or by analyzing the relationship between phase measurements at two frequencies when using dual frequency receivers. Upon determination that an anomalous measurement exists, the particular channel on which the anomalous measurement has occurred is determined. In addition, the extent of the anomalous measurement is estimated to produce an estimated error value. This information may then be used by the satellite navigation receiver in order to increase the accuracy of a navigation task.

Abstract: Duplicate processing at network operators is avoided by applying once-only processing at operators which are adjacent to either the source or destination host of a data packet. An operator is adjacent to a host if there exists a path between the operator and the host containing no other operators. In one embodiment, an operator determines that it is adjacent to a host if it receives a special broadcast data packet from the host. To ensure that no other operators receive the special broadcast data packet, the adjacent operator drops the packet. In another embodiment, operators determine whether they are adjacent to identified hosts by transmitting special ping packets to the hosts. If an operator receives a ping response from the host, the operator determines that it is adjacent to the host. To ensure that only adjacent operators receive ping responses, intervening operators drop special ping packets received from other operators.

Abstract: A network server stores database tables for use in resolving labels into network addresses as requested by a remote browser client. Each user has an associated address-table which stores user defined labels associated with network addresses. Users may access other user's address-tables if such other users grant authority to do so. Each user defines the address-tables to be searched, along with a search order, to be used when the user requests that a label be resolved into a network address. During address resolution, the server will resolve a received label into the network address associated with the label as defined by the first accessed address-table which contains the label. The search order as defined by the user may be overridden for a particular address resolution request by an appropriate user command. In various embodiment, the network addresses may be WWW addresses and electronic mail addresses.

Abstract: A packet data filter which stores ordered rules and sequentially applies the rules to received data packets to determine the disposition of the data packet. The packet filter maintains a match count in memory which indicates the number of times each rule matched an incoming data packet. Periodically, at the initiation of a user, or based on operating parameters of the filter, the rules are automatically re-ordered based on the match count. As a result of the re-ordering, rules with higher match counts are moved earlier in the sequential evaluation order and rules with lower match counts are moved later in the sequential evaluation order. As such, rules which are more likely to match incoming data packets are evaluated earlier, thus avoiding the evaluation of later rules. In order to prevent a re-ordering which would change the overall security policy of the packet filter, pairs of rules are compared to determine if they conflict (i.e.

Abstract: Signal points from a PCM-derived constellation are selected for transmission via a modulation technique which employs different levels of redundancy coding—including the possibility of no redundancy coding—for respective different sub-constellations of the overall PCM-derived constellation. The coding that is employed for at least one of the sub-constellations is carried out independently from any coding that is employed for any of the other sub-constellations. The PCM-derived constellation and the overall modulation technique are designed so as to accommodate the possibility that the telecommunications system in which the modulation technique is implemented may include so-called bit robbing and so-called digital attenuation.

Abstract: A computer operating system in which transfer of control of executing threads between protection domains is implemented using specific portals dedicated to the particular transfer of control between two protection domains. The transfer of control may also include parameter manipulation. A server registers a portal specification with a portal manager, the portal specification defining the behavior of portals which transfer control to the server. Thereafter, when a client application desires service from the server, the client application requests instantiation of a portal which will transfer control of an execution thread from the client application protection domain to the server protection domain. Upon receipt of the request, the portal manager dynamically generates portal code and updates a portal table associated with the client application, thus instantiating the portal.

Abstract: A wireless terminal dynamically maintains location dependent operating parameters while operating in low power-consuming sleep mode. The wireless terminal wakes up periodically to determine its current location. If the current location is within a predetermined distance from a previously stored location, then the wireless terminal stores the previously stored location, along with its associated location dependent operating parameter, in a predetermined memory location within the wireless terminal. If the current location is not within a predetermined distance from a previously stored location, then the wireless terminal generates a new location dependent operating parameter for its current location and stores the current location and new location dependent operating parameter in the predetermined memory location. In various embodiments, the location dependent operating parameter may be, for example, a digital control channel or a mobile switching center identification.

Abstract: Two or more digital signals are encoded using two or more respective line codes. The line codes are chosen in conjunction with the data rates of the digital signals such that the encoded signals are substantially orthogonal to each other in the frequency domain. As such, the two or more encoded signals may be combined and transmitted via a single physical medium with little or no interference. A transmitter for encoding and transmitting the digital signals contains line coders for encoding the digital signals and a combiner for combining the encoded signals for transmission via a single physical medium.

Abstract: A contention-based network which allows real-time traffic to exist as multiple independent linked-list chains or under certain conditions to be assembled into multiple linked-list chains. A time separation is enforced between the various multiple chains, which are limited to a predetermined maximum number of stations that each can have in order to allow non-real-time stations to obtain timely access to the medium. Ones of the multiple chains may also be joined into a single chain. Blackburst contention is used to enable a chain to be reconstituted robustly from non-anticipated interruptions, such as the failure of one of its stations.

Abstract: Advantageous error rate performance, high bandwidth efficiency, low delay and reduced error floor are achieved at an acceptable level of decoding complexity via the use of serial concatenated turbo codes. These are codes for which at least some of the output bits, including at least one redundant bit, provided by a first, outer encoder are, after interleaving, further processed by a second, inner encoder. The interleaver uses as its interleaved elements the bits associated with a particular symbol interval. The resulting data and redundant bits then select a symbol from a predetermined constellation for transmission. In the receiver, the turbo code is decoded using a corresponding number of soft output decoders which operates iteratively in such a way that improved performance as compared to a single encoding can be achieved. The turbo codes can be of various dimensionalities and can be used as a component of a multilevel code to achieve a desired level of bandwidth efficiency.

Abstract: Advantageous error rate performance, high bandwidth efficiency, low delay and reduced error floor are achieved at an acceptable level of decoding complexity via the use of serial concatenated turbo codes. These are codes for which at least some of the output bits, including at least one redundant bit, provided by a first, outer encoder are, after interleaving, further processed by a second, inner encoder. The resulting data and redundant bits then select a symbol from a predetermined constellation for transmission. In the receiver, the turbo code is decoded using a corresponding number of soft output decoders which operates iteratively in such a way that improved performance as compared to a single encoding can be achieved. The turbo codes can be of various dimensionalities and can be used as a component of a multilevel code to achieve a desired level of bandwidth efficiency.

Abstract: A path-oriented approach is provided to determine surviving paths in a decoder. The paths that are retained as the surviving paths are some number, M, of the paths which have the smallest path metrics, even if two or more of those paths come into a given state. This approach provides significantly improved performance in at least those applications in which branch metrics are a function of the surviving path from which the branch emanates.

Abstract: In a method of administering a telephone local loop plant, a substantial portion--preferably at or above 80%--of the existing narrowband plant is caused to be "dedicated," so that constituent segments of an existing local loop therewithin are not allowed to be used to form other local loops when the existing loop is taken out of service. The remainder of the narrowband plant--the "non-dedicated" plant--is used to fill subscriber current orders for new service. Administration of the narrowband plant that has been dedicated is given over to an administrative system that is deployed to administer broadband facilities within the local loop plant. In preferred embodiment, the local loop plant is upgraded from narrowband to broadband in a way which gives priority to those geographical areas for which the costs of maintaining the narrowband plant are the greatest. The method, overall, provides a mechanism for reducing the costs associated with administering all of the narrowband plant using the legacy systems.

Abstract: A logical data architecture for fetch-intensive database applications includes a first and a second logical database. The second database includes materialized views over the first database. Updates are propagated from the first database to the second database using so-called view maintenance techniques. In preferred embodiments, the first database may be optimized for update transactions and the second database may be optimized for read transactions. At least one of the materialized views included in the second database is based on a pre-defined application read transaction. The update processing overhead associated with view maintenance is substantially performed at the first database.

Abstract: A method and apparatus for determining whether a wireless station is operating within a prescribed geographic location. During an initialization process, the wireless telephone measures propagation delays of pilot signals from nearby base stations and stores the propagation delays in a non-volatile memory of the wireless station. Thereafter, during a check process, the wireless station measures propagation delays of pilot signals from nearby base stations and compares them with the stored propagation delays stored in memory. If the difference between the two sets of propagation delays are within a predetermined tolerance, then a determination is made that the wireless station is operating within the prescribed geographic location. Multiple sets of propagation delays may be stored in memory such that a determination can be made as to whether the mobile station is operating within any one of a number of prescribed geographic locations.

Abstract: Signal points from a PCM-derived constellation are selected for transmission via a modulation technique which employs different levels of redundancy coding--including the possibility of no redundancy coding--for respective different sub-constellations of the overall PCM-derived constellation. The coding that is employed for at least one of the sub-constellations is carried out independently from any coding that is employed for any of the other sub-constellations. In preferred embodiments, the sub-constellations are non-overlapping portions of the overall PCM-derived constellation, the redundancy codes are trellis codes, and the trellis codes employed in conjunction with sub-constellations having increasingly smaller minimum distance between signal points provide respectively increasing amounts of decibel gain in that minimum distance in order to compensate for that increasingly smaller minimum distance.