Abstract: An apparatus and method for providing bandwidth on demand service in a wireless communication system having at least one user station, including a frequency divider for dividing a selected bandwidth into a plurality of frequency subdivisions. Also included is a unit for assigning a first number of frequency subdivisions to the individual user stations having a first total bandwidth, commensurate with the volume of transmission traffic. There also is a unit for changing the first number to a second number having a second total bandwidth commensurate with the change of the volume of transmission traffic.

Abstract: In a multi-channel demodulator, a detection-transition sample estimation scheme classified samples as left (L) or right (R) of a reference position within a symbol interval (110), or before (B) or after (A) a transition between symbols (120). When a sample is classified as L or B, the classification of the next sample is forced to R or A, respectively. A memory is provided for storing the contents of various registers when switching to processing of a different channel, and for retrieving from the memory stored data corresponding to previous processing of the different channel. Data read from the memory is written to a register downstream of the register from which it was taken when written to the memory. The read cycle of the memory is extended to ensure that a clock is available to load the data from memory into the downstream register after switching to the new channel.

Abstract: A completely autonomous failure recovery scheme for digital beam forming that provides self-diagnosis and self-healing of faulty processing chains in a communications satellite payload. A baseline processor comprises a plurality of processing chains that are identical in hardware and differ only in software. A redundant chain is programmed identically to the first processing chain by downloading the appropriate software coefficients from a controller. The first chain is then selected by a SELECT logic component its output is compared by a COMPARE logic component to the output of the redundant chain. In the absence of malfunctions, the two outputs should be identical. If the two outputs are not identical, the chain is diagnosed as faulty and it is replaced by a "hot" standby redundant chain. Further, a control signal from the diagnosis module alters the position of at least one output switch to disconnect the faulty module.

Abstract: A method and apparatus for determining initial carrier and symbol phase estimates in a burst mode digital communication system are described. In-phase and quadrature sample of a BPSK preamble are sampled to obtain correlation values. Next, sum and differences of the correlation values are obtained. Then the initial carrier phase estimate (THETAHAT) and the initial symbol phase estimate (TAUHAT) are obtained through application of an algorithm. The apparatus that implements the method consists of adders, inverters, arc tangent look-up tables and divide by 2 logic units.

Abstract: A method is described for performing fast Fourier transforms (FFTs) of various sizes simultaneously in one pipeline processor. The processor consists of several stages of butterfly computational elements alternated with delay-switch-delay (DSD) modules that reorder the data between the butterfly stages. The sequence of the DSD operations in the pipeline is made arbitrary. This flexibility in choosing the DSD sequence enhances the fault tolerance operation of the pipeline in case of a partial failure in one or more of the DSD modules. If one of the DSDs is no longer capable of operating in its prescribed mode, it is assigned a different operating mode. All the required changes are performed by software control without the need to physically remove or interchange any components. By properly ordering the input data to the pipeline and the butterfly twiddle factors, and by bypassing some butterfly elements for the smaller size transforms, it is shown that any mixture of FFT sizes can be performed.

Abstract: An apparatus for obtaining carrier synchronization acquisition in a digital burst mode communication system is provided. An accurate estimate of the carrier phase of the unmodulated preamble, .theta., is obtained by determining which of 256 intervals X.sub.o.sup.2 +X.sub.e.sup.2 fall into, and by evaluating which of 256 intervals Y.sub.o.sup.2 +Y.sub.e.sup.2 fall into. A quantized value is assigned to the generated output code for both X and Y inputs. The square root and arc tangent are evaluated to determine the value .theta..