Abstract: A method and apparatus for Turbo encoding uses a set of rate-compatible Turbo Codes optimized at high code rates and derived from a universal constituent code. The Turbo Codes have rate-compatible puncturing patterns. The method comprises: encoding a signal at a first and second encoder using a best rate 1/2 constituent code universal with higher code rates, the first encoder and the second encoder each producing a respective plurality of parity bits for each information bit; puncturing the respective plurality of parity bits at each encoder with a higher rate best puncturing patterns; and puncturing the respective plurality of parity bits at each encoder with a lower rate best puncturing pattern. In a variation, the best rate 1/2 constituent code represents a concatenation of polynomials 1+D2+D3 (octal 13) and 1+D+D3 (octal 15), D a data bit. A Turbo Encoder is provided which has hardware to implement the method.

Abstract: A method and apparatus for performing fractional minimum shift key modulation for a very small aperture terminal. A signal with a fractional modulation which appears to be frequency shift key is generated in the indoor unit. The outdoor unit employs a novel multiplication method to translate this signal to a minimum shift key modulated signal for satellite transmission.

Abstract: A VSAT system for generating and transmitting a modulated data signal to a satellite. The VSAT system includes an indoor unit for generating a modulated data signal having an envelope of constant amplitude, and an outdoor unit including a transmitter module operative to receive the modulated data signal and to frequency multiply and amplify the modulated data signal so as to produce a modulated carrier signal having an envelope of constant amplitude. The transmitter module includes a multiplier operative to frequency multiply the modulated data signal to the frequency of the modulated carrier signal, and a power amplifier operated in the saturation mode, which amplifies the modulated carrier signal to the desired power level. The components constituting the transmitter module are formed on a single integrated circuit.

Abstract: A burst analyzer is useful in a digital communication system in which a signal burst has a plurality of reference segments distributed within the signal burst for transmission of a plurality of reference signals. The burst analyzer includes a filter that compares the received signal, for each reference segment thereof, with each reference signal offset by one of a plurality of time offsets to generate correlation data. The burst analyzer then determines, for each reference segment of the signal burst, a maximum correlation value from the correlation data for each time offset. Then the burst analyzer determines the time offset at which a sum of the maximum correlation values, over the plurality of reference segments, is a maximum. The burst analyzer jointly generates a frequency domain representation of the correlation data associated with the time offset at which the maximum correlation sum is a maximum, and then determines a frequency at which the frequency domain representation is a maximum.

Abstract: An apparatus for generating a modulated signal which includes a modulator operative for receiving a first signal and input data signals, and modulating the first signal in accordance with the input data signals so as to produce a modulated reference signal; a first frequency divider coupled to the modulator output, operative to reduce the frequency of the modulated reference signal by a predetermined factor; a signal generator operative to produce a second signal; a first mixer having a first input coupled to an output of the first frequency divider and a second input coupled to the output of the signal generator. The first mixer operates to frequency translate the modulated reference signal by an amount equal to the frequency of the second signal. In addition, the signal generator of the present invention contains a direct digital synthesizer coupled to a second phase lock loop which operates to up-convert the output signal of the DDS to the microwave region.

Abstract: An MSAT system is provided which optimizes satellite resources when implementing a single-hop TtT call. The system allocates satellite channels and signaling channels for a single-hop TtT call to the participating terminals at an early stage during the call set-up procedure such that only a single pair of satellite channels are assigned to each of the terminals for call establishment and for use during the call, as opposed to two pairs of satellite channels. A test message for signaling channel (e.g., TTCH) validation is transmitted from the network (e.g., from a gateway station controller) to each of the terminals.

Abstract: A multicast network system utilizes a high speed link, such as a satellite link, to multicast multimedia information from the Internet to a plurality of receivers, such as personal computers. Information from selected web sites is organized into “channels” and provided to a multicast network for multicast transmission to the receivers. Updated channel information is also periodically provided. The receivers store the received channel such that a user can access the web page content in the channel at hard disk speed. Preferably, a conditional access system ensures that only authorized receivers receive the channels. The present invention also preferably includes a lower speed two-way connection to the Internet (such as dial up modem) which is used to report usage information and/or subscription information back to the web sites.

Abstract: An approach for electronically performing beam steering is disclosed. For electronic scanning, an n-bit quantized phase shifting approach is employed at each array element of a phased array antenna. By applying an initial phase bias, either deterministically or randomly, in each of the array elements, the performance of a phased array with n-bit quantization (even with n=2) approaches the performance of a system with no quantization. This approach can be used with linearly polarized or circularly polarized waves. For circularly polarized waves, the 2n phase shifts required of n-bit quantization are achieved in a manner that provides a simple, low-loss construction, which allows production of a low-cost reflectarray or a flat-plate lens.

Abstract: A method for improving spectral sampling using Discrete Fourier Transforms in a processor to detect a continuous wave (CW) signal in a burst having large initial uncertainties comprises the steps of dividing the burst into smaller sub-bursts; performing a Discrete Fourier Transform on each sub-burst; and non-coherently combining each sub-burst. A further variation includes selecting an optimal number L of sub-bursts based upon system performance, and desired detection performance at a minimum operating signal to noise ratio.

Abstract: A system and method of soft decision decoding is disclosed. An average signal magnitude is generated from a plurality of message bits. A scale factor is generated in accordance with the average signal magnitude, and soft decision bits are generated by processing the message bits using the scale factor. The scale factor and soft decision bits are transmitted and received across a communication link. The soft decision bits are rescaled using the scale factor and then rounded to the nearest integer value. The rounded values are then decoded. The soft decision bits are generated using a quantization having at least two bits, and soft decision bits are preferably rescaled using at least five bits.

Abstract: A satellite communication system has a first deployment of a plurality of satellites deployed in a medium earth orbit and two later deployments of a plurality of satellites deployed in the medium earth orbit. The first deployment is spaced so that the second deployment may be easily deployed and interleaved into the first deployment. A ground terminal is used for communicating with the satellites in the first and second deployments.

Abstract: An electronic document delivery system and method in which a broadcast center periodically sends a “catalog” of available documents to a receiving computer, thereby allowing a user to browse through the available documents without having to access the broadcast center. The documents are transmitted as packets, and the packets are decrypted as soon as they are received, eliminating the need to store both an encrypted and an decrypted version of the documents at the receiving computer. The receiving computer periodically receives information allowing it to decrypt received documents and to encrypt billing information for the receiving computer. The invention is not limited to text-only documents and can receive all types of documents, such as software, images, text, and full-motion video.

Abstract: A novel mobile satellite communications technique for hand-held terminals includes a satellite system having a plurality of individual satellites all in communication with a ground telecommunications hub. A signal processed by the ground telecommunications hub is radiated through multiple paths to a plurality of the individual satellites in the satellite constellation simultaneously. The radiated signal is then re-radiated by the plurality of individual satellites to a mobile satellite terminal that receives the re-radiated signal from the plurality of individual satellites simultaneously such that the same frequency spectrum may be re-used by another mobile user.

Abstract: A system in which a personal computer sends messages into a TCP/IP network using a conventional dial-up link and downloads data from the TCP/IP network using a high-speed one-way satellite link. A preferred embodiment uses a conventional SLIP provider to connect to the TCP/IP network and uses a commercial software TCP/IP package that has a standard driver interface. A spoofing protocol compensates for the long propagation delays inherent to satellite communication.

Abstract: A method for uplink power control and time synchronization in a satellite communications system that is achieved using satellite-based measurements of the uplink signal power and signal arrival time. Uplink signals transmitted from an originating terminal are received by a communications satellite which measures the received signal power and arrival time. The satellite transmits a downlink signal to the originating terminal containing information of the measured uplink signal power and arrival time. The originating terminal receives the downlink signal and transmits subsequent uplink signals with an uplink signal power and transmission timing based on the information transmitted by the satellite.

Abstract: A satellite-based communications system operating at high data rates includes a plurality of communications satellites each having an uplink and a downlink antenna for receiving and transmitting a plurality of spot beams which may be fixed or scanned. The fixed beams may be directed to areas of high satellite use. The scanned beams may be rapidly scanned between areas of use insufficient to support a dedicated beam. The scanned beam allows potentially nearly ubiquitous coverage by using high frequency beams. To rapidly scan, beam forming networks have a plurality of phase coefficients that may be changed so that the angle of the beam may change. A controller coupled to the beam forming network may be used to change the phase coefficients in response to beam inputs such as the desired beam and configurations of the other beams on the satellite.

Abstract: A method of interleaving blocks of indexed data of varying length is disclosed. The method includes the steps of: providing a set of basic Interleavers comprising a family of one or more permutations of the indexed data and having a variable length; selecting one of the basic Interleavers based upon a desired Interleaver length L; and adapting the selected basic Interleaver to produce an Interleaver having the desired Interleaver length L.

Abstract: Methods for the design and fabrication of micro-electro-mechanical switches are disclosed. Two different switch designs with three different switch fabrication techniques are presented for a total of six switch structures. Each switch has a multiple-layer armature with a suspended biasing electrode and a conducting transmission line affixed to the structural layer of the armature. A conducting dimple is connected to the conducting line to provide a reliable region of contact for the switch. The switch is fabricated using silicon nitride as the armature structural layer and silicon dioxide as the sacrificial layer supporting the armature during fabrication. Hydrofluoric acid is used to remove the silicon dioxide layer with post-processing in a critical point dryer to increase yield.

Abstract: An apparatus and method, for use in a satellite-based communications network, for minimizing blocking of communication between the network and access terminals resulting from differences in the signal propagation delays for the access terminals due to their different locations within a coverage area serviced by a spot beam generated by a satellite in the network. The apparatus includes a spot beam segregator which segregates a coverage area of the spot beam into at least one coverage zone based on the maximum and minimum propagation delay experienced by access terminals within the coverage area of the spot beam. The apparatus further includes a carrier grouper which groups the carrier into a number of groups corresponding to the number of offset zones, and assigns each carrier group to a respective one of the coverage zones.