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Full-Text Articles in Social and Behavioral Sciences
A Low Cost Soft Mapper For Turbo Equalization With High Order Modulation, Licai Fang, Qinghua Guo, Defeng (David) Huang, Sven Nordholm
A Low Cost Soft Mapper For Turbo Equalization With High Order Modulation, Licai Fang, Qinghua Guo, Defeng (David) Huang, Sven Nordholm
Faculty of Engineering and Information Sciences - Papers: Part A
In an MMSE based turbo equalization system, a soft mapper calculates the symbol mean and variance based on extrinsic Log-Likelihood-Ratios (LLRs) information coming from a Soft-Input Soft-Output (SISO) decoder. In this paper, we investigate the complexity of this module, and in particular, we employ a 3-segment linear approximation approach to calculate the mean and variance of data symbols from LLRs. For FPGA and VLSI implementation, we propose novel piecewise linear functions which map LLR to the mean and variance directly without the use of any two-variable-input multipliers. Simulation results for 16-QAM and 64-QAM show that the no multiplier approach has …
Lmmse Turbo Equalization Based On Factor Graphs, Qinghua Guo, Li Ping
Lmmse Turbo Equalization Based On Factor Graphs, Qinghua Guo, Li Ping
Faculty of Engineering and Information Sciences - Papers: Part A
In this paper, a vector-form factor graph representation is derived for intersymbol interference (ISI) channels. The resultant graphs have a tree-structure that avoids the short cycle problem in existing graph approaches. Based on a joint Gaussian approximation, we establish a connection between the LLR (log-likelihood ratio) estimator for a linear system driven by binary inputs and the LMMSE (linear minimum mean-square error) estimator for a linear system driven by Gaussian inputs. This connection facilitates the application of the recently proposed Gaussian message passing technique to the cycle-free graphs for ISI channels. We also show the equivalence between the proposed approach …
Evolution Analysis Of Low-Cost Iterative Equalization In Coded Linear Systems With Cyclic Prefixes, Xiaojun Yuan, Qinghua Guo, Xiaodong Wang, Li Ping
Evolution Analysis Of Low-Cost Iterative Equalization In Coded Linear Systems With Cyclic Prefixes, Xiaojun Yuan, Qinghua Guo, Xiaodong Wang, Li Ping
Faculty of Engineering and Information Sciences - Papers: Part A
This paper is concerned with the low-cost iterative equalization/detection principles for coded linear systems with cyclic prefixes. Turbo frequency-domain-equalization (FDE) is applied to systems that may contain the joint effect of multiple-access interference (MAI), cross-antenna interference (CAI) and inter-symbol interference (ISI). We develop an SNK-variance evolution technique for the performance evaluation of the proposed systems. Numerical results in various channel environments demonstrate excellent agreement between the predicted and simulated system performance. © 2008 IEEE.
Turbo Equalization Based On Factor Graphs, Qinghua Guo, Li Ping, Hans-Andrea Loeliger
Turbo Equalization Based On Factor Graphs, Qinghua Guo, Li Ping, Hans-Andrea Loeliger
Faculty of Engineering and Information Sciences - Papers: Part A
This paper presents a factor graph approach to turbo equalization. Unlike the existing linear MMSE turbo equalization methods, which operate with truncated windows (sliding or extending window), the proposed is a full-window approach with low complexity. This approach supports a high-speed parallel implementation technique, which makes it an attractive option in practice.