Abstract: A system and method for carrier recovery includes a plurality of carrier recovery modules, each processing the same input symbols, and each having a gain input and an error output. A loop gain control receives errors from the carrier recovery modules and provides gains to the carrier recovery modules. Based upon the errors during a current period, the loop gain control determines which module produced lowest errors, and selects the gain associated with that module as a best gain which is applied to a module which outputs symbols for decoding during a next period.

Abstract: A satellite communications system comprises a transmitter, a satellite transponder and a receiver. The transmitter transmits an uplink multi-level modulated signal (hierarchical modulation, layered modulation, etc.) to the satellite transponder, which broadcasts the multi-level modulated signal downlink to one, or more, receivers. The multi-level modulated signal comprises an upper layer and a lower layer. The lower layer conveys LDPC yes blocks, or LDPC frames, each LDPC block comprising S bits of data including a header portion and a data-bearing portion. The upper layer conveys shorter blocks, each shorter block comprising R bits of data, where R<S, the shorter block also comprising a header portion and a data-bearing portion. The transmitter synchronizes the start of transmission of each LDPC block to the start of transmission of a shorter block.

Abstract: A satellite receiver includes a down converter for providing a received signal and a demodulator having at least two demodulation modes for demodulating the received signal, wherein one demodulation mode is hierarchical demodulation and another demodulation mode is layered demodulation.

Abstract: A satellite receiver receives a hierarchical modulation based received signal, which has at least an upper layer (UL) and a lower layer (LL), and simultaneously recovers therefrom data conveyed in the UL signal and data conveyed in the LL signal.

Abstract: A satellite communications system comprises a transmitting ground station, including a transmitter and a receiver, a satellite transponder and a receiving ground station. The transmitter transmits an uplink signal to the satellite transponder, which broadcasts the received uplink signal as a downlink signal to the receiving ground station. The transmitting ground station monitors the downlink signal through the receiver and calculates log-likelihood ratios (LLRs) as a function of the monitored downlink signal. These LLRs are illustratively stored in a look-up table, which are then transmitted to the receiving ground station for use in recovering data from a received data signal.

Abstract: A Universal Mobile Telephone System (UMTS) receiver performs frame synchronization in accordance with a soft decision technique. Illustratively, the UMTS receiver first forms a matrix of correlation peak values (350) from at least one received frame, each row of the matrix representing a possible SSCH code and each column of the matrix representing a slot position of an SCH frame. The UMTS receiver then forms a metric (355) for each cyclic shift of each one of 64 possible scrambling code groups from the matrix of correlation peak values and identifies the metric with the highest value (360). Having identified the highest metric value (360), the UMTS receiver uses the scrambling code group (365) and offset associated thereto (370) to complete frame synchronization.