Abstract: The turbo encoding process repeats the bits of the systematic data and appends the flushing tail bits prior to interleaving and encoding by the second constituent turbo encoder for providing an interleaved repetitive second encoded output for turbo decoding as a repetitive turbo code method to reduce the error floor of turbo coding. Preferably, the repetitive systematic string is also encoded by the first encoder and is transmitted providing repetitive transmitted first encoded sequence and a repetitive transmitted systematic sequence from the turbo encoder. The turbo decoder operates on three repetitive sequences and perform bit deletion among r repetitive systematic bits after conventional turbo decoding. The repetitive sequences may also be subjected to encoder puncturing and decoder bit insertion as an alternative enhancement.

Abstract: A satellite communications system includes an orbiting communications satellite for relaying communications to and from a plurality of ground stations, and a network management center for making connections via the satellite between the ground stations in response to connection requests received via the satellite from the ground stations, the network management center being configured to provide both open-end service and closed-end service. The network management center of one embodiment is configured to provides both types of service according to a predefined channel access protocol that enables the ground stations to request the type of service desired. The channel access protocol may be configured to adaptively allocate channels to open-end service and closed-end service according to changes in the traffic pattern and include a free-access tree algorithm that coordinates collision resolution among the ground stations.

Abstract: A circuit for generating a sequence of pseudo random numbers, {A.sub.k }. There is an exponentiator (30') in GF(2.sup.m) for the normal basis representation of elements in a finite field GF(2.sup.m) each represented by m binary digits and having two inputs and an output from which the sequence {A.sub.k } of pseudo random numbers is taken. One of the two inputs is connected to receive the outputs {E.sub.k } of maximal length shift register of n stages. There is a switch (32) having a pair of inputs and an output. The switch (32) output is connected to the other of the two inputs of the exponentiator (30'). One of the switch (32) inputs is connected for initially receiving a primitive element A.sub.0 in GF(2.sup.m). Finally, there is a delay circuit (34) having an input and an output.

Abstract: A technique for measuring the ion implant dosage involves method and apparatus for directing pulses of coherent radiation from a laser to the surface of a semiconductor that has been subjected to ion implant. The intensity of the third harmonic reflected from the semiconductor is determined and correlated to determine the ion dosage within the semiconductor.