Abstract: A turbo decoder that calculates alpha, beta and gamma (branch metric) values does not normalize the branch metric but instead applies the normalization factor to the newly calculated extrinsic values before writing them to interleaving memory, resulting in use of less memory than in prior turbo decoders. A compensating factor is applied when the extrinsics are read from interleaving memory. The absence of normalization in the gamma calculation not only conserves memory but also enhances decoder sensitivity.

Abstract: Methods and apparatus are provided for block and rate independent decoding of LDPC codes. The disclosed LDPC decoders support multiple code block lengths and code rates, as well as a variable parity check matrix. The disclosed LDPC decoders decode LDPC codes that are based on a parity check matrix having a plurality of sub-matrices, wherein each row and column of the plurality of sub-matrices has a single entry. Each of the sub-matrices has at least one associated Phi-node, wherein each Phi-node comprises a memory device having a plurality of memory elements, wherein one or more of the memory elements may be selectively disabled. The Phi-nodes may be selectively disabled, for example, at run-time. The Phi-node optionally further comprises a multiplexer in order to provide a variable parity check matrix.

Abstract: Apparatus and method to determine selection of a scrambled data channel before receipt of an entire data block. An initial portion of a block of data received in one of a plurality of scrambled data channels is decoded, then re-encoded. A value is computed related to the number of mis-matched data symbols based on a comparison of decoded/re-encoded data and the corresponding received data. A best one of the plurality of data channels is selected based on the computed value being beyond a given threshold value.

Abstract: A method for performing a tree search is provided. A set of candidates is identified and then interim and final characteristics associated with each of the candidates are produced by a plurality of parallel tasks. These interim and final characteristics are examined, and each candidate that has at least one of the interim and final characteristic exceeding at least one preselected setpoint is removed from the set of candidates. Candidates with only interim results that do not exceed the preselected setpoint are selected for continued processing. Candidates with a final characteristic falling below the preselected setpoint are assembled into a heap. The process repeats until all of the partial candidates have had their final characteristic determined or no partial candidates remain.