LDPC codes optimization for differential encoded LDPC coded systems with multiple symbol differential detection

2016 ◽  
Author(s):  
Yang Yu ◽  
Ziyan Jia ◽  
Weige Tao ◽  
Shiliang Dong
Keyword(s):  
Ldpc Codes ◽  
Differential Detection ◽  
Coded Systems

scholarly journals Mapper and Demapper for LDPC-Coded Systems

2012 ◽  
pp. 104-109
Author(s):  
U. Kiran ◽  
V. Ugendar
Keyword(s):  
Ldpc Codes ◽  
Low Complexity ◽  
Error Correcting Codes ◽  
Modulation Scheme ◽  
Finite Precision ◽  
Decoding Algorithms ◽  
Mapping Strategy ◽  
Coded Systems ◽  
Approximate Expressions ◽  
The Ideal

Low Density Parity Check (LDPC) codes are state-of-art error correcting codes, included in several standards for broadcast transmissions. Iterative softdecision decoding algorithms for LDPC codes reach excellent error correction capability; their performance, however, is strongly affected by finite-precision issues in the representation of inner variables. Great attention has been paid, in recent literature, to the topic of quantization for LDPC decoders, but mostly focusing on binary modulations and analyzing finite precision effects in a disaggregrated manner, i.e., considering separately each block of the receiver. Modern telecommunication standards, instead, often adopt high order modulation schemes, e.g. M-QAM, with the aim to achieve large spectral efficiency. This puts additional quantization problems, that have been poorly debated in previous literature. This paper discusses the choice of suitable quantization characteristics for both the decoder messages and the received samples in LDPC-coded systems using M-QAM schemes. The analysis involves also the demapper block, that provides initial likelihood values for the decoder, by relating its quantization strategy with that of the decoder. A signal label for a signal in a 2m-ary modulation scheme is simply the m-bit pattern assigned to the signal. A mapping strategy refers to the grouping of bits within a codeword, where each mbit group is used to select a 2m-ary signal in accordance with the signal labels. The most obvious mapping strategy is to use each group of m consecutive bits to select a signal. . We will call this the consecutive-bit (CB) mapping strategy. An alternative strategy is the bit-reliability (BR) mapping strategy which will be described below. A new demapper version, based on approximate expressions, is also presented, that introduces a slight deviation from the ideal case but yields a low complexity hardware implementation.

Differential Detection of Single-Chain and Two-Chain Urokinase-Type Plasminogen Activator by a New Immunoadsorbent-Amidolytic Assay (IAA)

1986 ◽  
Vol 56 (03) ◽  
pp. 407-410 ◽  
Author(s):  
Angelo Corti ◽  
Maria Luisa Nolli ◽  
Giovanni Cassani
Keyword(s):  
Plasminogen Activator ◽  
Carcinoma Cell ◽  
Differential Detection ◽  
Single Chain ◽  
Response Curves ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator ◽  
Before And After ◽  
Culture Supernatants ◽  
Human Epidermoid Carcinoma

SummaryA new immunoadsorbent-amidolytic assay (IAA) for the specific differential detection of two-chain urokinase-type plasminogen activator (tcu-PA) and its single-chain precursor (scu-PA) in cell culture supernatants has been developed. The assay combines the selectivity of immunoassays with the specificity of enzyme activity assays exploiting both the antigenic and enzymatic properties of the two proteins. tcu-PA and scu-PA are selectively immunoadsorbed on the wells of a microtiterplate coated with the monoclonal antibody 5B4 and tested for enzymatic activity before and after activation by plasmin treatment. Both proteins are determined with similar efficiency since overlapping dose-response curves were obtained in the range between 12.5-200 ng/ml. The assay has been used to determine tcu-PA and scu-PA in A431 human epidermoid carcinoma cell supernatants. The analytical recoveries for tcu-PA and scu-PA added to A431 cell supernatants were 95.2% and 96.9% respectively. The intra- and inter-assay variations (CV) were 5.5% and 9.0% for tcu-PA and 9.7% and 9.8% for scu-PA respectively.

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