Abstract: A passive tag transponder circuit comprising a receive antenna, reflect antenna, and rectifier network. The receive antenna can be configured to receive an ambient RF signal having a frequency of fc, or, a backscattered RF signal having a frequency of 2fc. The reflect antenna can be configured to receive a rectified output signal from the rectifier network, the rectified output signal having a frequency of 2fc. The reflect antenna can be configured to send a backscattered signal at the frequency of 2fc. The rectifier network can be connected to receive an input corresponding to the ambient RF from the receive antenna and send the rectified output to the reflect antenna.

Abstract: A passive tag transponder circuit comprising a receive antenna, reflect antenna, and rectifier network. The receive antenna can be configured to receive an ambient RF signal having a frequency of fc, or, a backscattered RF signal having a frequency of 2fc. The reflect antenna can be configured to receive a rectified output signal from the rectifier network, the rectified output signal having a frequency of 2fc. The reflect antenna can be configured to send a backscattered signal at the frequency of 2fc. The rectifier network can be connected to receive an input corresponding to the ambient RF from the receive antenna and send the rectified output to the reflect antenna.

Abstract: The system and method of the present invention can allow the imbedding of simulation primitives within a conventional programming language in order to use the full capabilities of the conventional programming language and its compiler without modification in the programming of efficient, scalable simulators. The simulation primitives are designed to be preserved through the compilation process, thus allowing a rewriter to modify the compiler's byte code output without accessing the source code. Also, since the rewriter output is a set of class files and a kernel can be written in the conventional programming language, and the system and method of the present invention can execute within a conventional virtual machine associated with the conventional programming language.

Abstract: A fault-tolerant and secure on-line certification authority uses replication to achieve availability. A client request is forwarded to a delegate server. The delegate forwards the request to all certification servers. After receiving responses from a quorum of certification servers, the delegate sends a client response including a threshold signature protocol to sign the client response. The delegate then forwards the client response to the client.

Abstract: A system and method for optimizing usage of a communications transmission medium. The transmission medium may be sliced into time and frequency domains so as to create time-frequency slices for assignment to users having varying access rates and user-application requirements. Through scheduling of the various speed users within the frequency and time domains, the system and method can efficiently allocate and make use of the available spectrum, thereby accommodating higher rate users requiring greater bandwidths and time slot assignments while still preserving cost-efficient access for lower speed users. Depending on the signal modulation scheme, the time-frequency slices may be allocated on non-contiguous frequency bands. The system and method is also applicable to code-division multiple access (CDMA) techniques by slicing the available code space along time-code domains, frequency-code domains or, in three dimensions, along time-frequency-code domains.

Abstract: A system and method for optimizing usage of a communications transmission medium. The transmission medium may be sliced into time and frequency domains so as to create time-frequency slices for assignment to users having varying access rates and user-application requirements. Through scheduling of the various speed users within the frequency and time domains, the system and method can efficiently allocate and make use of the available spectrum, thereby accommodating higher rate users requiring greater bandwidths and time slot assignments while still preserving cost-efficient access for lower speed users. Depending on the signal modulation scheme, the time-frequency slices may be allocated on non-contiguous frequency bands. The system and method is also applicable to code-division multiple access (CDMA) techniques by slicing the available code space along time-code domains, frequency-code domains or, in three dimensions, along time-frequency-code domains.

Abstract: The inventive methods employ symmetric encryption with first and second keys to provide secure access to information accessible to be shared among a dynamically changing set of authorized users on a network having a server. A single copy of the information, encrypted with the first key of the server, is stored in a location accessible to all network users. The second key is a private key of an authorized user and is used by the server to encrypt the first key. The encrypted first key is then stored by the server at a storage location accessible by the authorized user. The user accesses the storage location, obtains the encrypted first key, and uses his private second key to decrypt and thereby recover the first key. The user then decrypts the stored information using the recovered first key.

Abstract: A process for efficiently distributing processing between a mobile computing device having limited resources and at least one remote computing device having substantially greater resources than the mobile computing device, comprises establishing wireless communication between the mobile computing device and the remote computing device in response to a user's invoking of an application at the mobile device. The mobile computing device executes, in parallel, a first version of an algorithm for performing a function associated with the user-invoked application to obtain a first result, and the remote computing device executes a second version of an algorithm for performing the same function associated with the user-invoked application to obtain a second result. The results that are available first (generally the locally generated results) are presented to the invoked application on the mobile device.

Abstract: A packetized cellular system in which a mobile quasi-periodically transmits a beacon signal containing an ID number to a first base station in the cell in which it is located for storage with the ID's of other active mobiles in the cell. A copy of a list of the active mobiles in that cell is transmitted to all adjacent cells where they are placed on non-active list. Control of a mobile is handed-off to a second base station upon the receipt of a transmitted ID number of the mobile at the second base station. The mobile is then listed as active in the database of the second base station and non-active in the first base station.

Abstract: A system is arranged to a) monitor the flow of data communicated within a session between a mobile end-user device and a host via a connection which includes a wireless link established over a wireless network b) detect a disabled condition of the wireless link c) in response thereof, simulates a functioning mode of the session, and d) when the wireless link is restored, resume the session between the mobile end-user device and the host at the stage where the disabled condition occurred, as if a disconnect never occurred.

Abstract: A packet synchronization technique, in a synchronous optical packet switch, which delays received packets to ensure that there is only one packet per local time slot. The packets are of a time duration .tau. which is equal to or less than one-half the duration of the local time slot of the optical switch. Each packet received at an optical switch is delayed an interval of n.tau. where n=0, 1 or 2.

Abstract: An optical packet switch which receives data packets and switches those data packets in the optical domain without using recirculation devices is provided. The switch staggers the data packets in time to avoid packet collisions within the switch. The switch includes two stages that are coupled by optical delay lines. The non-blocking stages include a scheduling stage and a switching stage. Incoming data packets are received at the scheduling stage and are output to appropriate optical delay lines. The scheduling stage and the delay lines ensure that the data packets do not collide when the packets are switched at the switching stage of the optical switch.

Abstract: The capacity of a multi-mode optical fiber system, such as a local area network, is increased by selectively propagating only higher-order modes through the multi-mode fiber. Because only a small number of higher-order modes are propagated, pulse spreading induced by modal dispersion is minimized, and the bandwidth of the multi-mode fiber is increased. Because of the reduced modal dispersion, higher-order modes are recovered from the multi-mode fiber in accordance with the invention without filtering the output of the fiber. This renders the system less vulnerable to mechanical perturbations that are known to reduce the bit error rate of systems requiring filtering. Thus, by propagating only higher-order modes in this manner, the "bandwidth-distance" product of the multi-mode fiber is significantly increased.

Abstract: The polarization-dependent distortion of an optical signal transmitted through an optical fiber is reduced by aligning the polarization of the optical signal to minimize the received signal distortion. A polarization controller (a device which can change the polarization of light in an optical fiber) may be located at either the input or output end of a long haul optical fiber system and is used to align the polarization of the signal to minimize the received signal distortion. Automatic operation of the polarization controller can be obtained by using a steepest-descent method based on a distortion measure of the received signal for the optical signal transmitted through the optical fiber to generate control signals which are used to control the polarization controller.

Abstract: Currently, with optical time division multiplexing, a switching node is operated at the peak transmission rate. For example, if the data transmission rate is 10 Gbps, the line cards in the switching circuit are also required to operate at this rate despite the fact that the switching node does not actually need to access the data at this rate. Thus, the electronics, which includes the line cards at the switching node, is expensive and less reliable than a low-speed design. In this invention the requirement of operating the switching node electronics at the high speed link bit rate is eliminated by encoding the packet header field at a lower rate than the information in the data field. As a result, the line cards need only operate at the lower header rate. This is possible because the switching node does not need to process the data portion of the packet, but only the header information.

Abstract: A new data communications architecture is disclosed in which high level communications services provided to a host processor are arranged into independent horizontal functions that are processed in parallel. Any conditional dependencies among the horizontal functions are resolved by a connector that interfaces the horizontal functions to an application layer of the host processor. Additionally, communication performance is enhanced by allowing adaptive specifications of a high-level protocol employed in the architecture for providing the high-level services. This adaptive specification may be initiated in response to changing user requirements or varying network parameters. Then, a high-level protocol specification is obtained by choosing appropriate values for parameters of the horizontal functions which are parametrically programmable.

Abstract: With this invention, collisions of optical packets in local area networks are avoided. Briefly, each branch of a local area network topology, such as a star, a ring or a bus is provided with an optical path having two substantially parallel optical fibers which can be selectively configured to form either a direct straight through path or a loop-back path. Prior to advancing a packet to the next occurring branch, a test is made to determine if it is occupied. If it is not occupied, the packet is advanced along one of the opitcal fibers of the optical path. If it is occupied, then the two optical fibers are rapidly configured to form a loop-back path and the packet travels around the loop-back path, again and again as required until the danger of a collison with a preceding packet no longer exists.