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Ming Gu |
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Ming’s research |
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Resume |
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Publications |
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· Analog Error-correcting Decoder |
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Carefully designed Low Density Parity Check (LDPC) codes are shown to operate close to channel capacity and present an efficient way of establishing robust data connections in a noisy environment. Due to their low decoding and encoding complexity, LDPC codes have been proposed and found to be attractive for a wide range of applications ranging from digital video broadcasting (DVB) to wireless sensor networks (WSNs). However, each of these applications imposes a different set of constraints on LDPC encoding and decoding algorithms and hence demands different performance specifications. For instance, a DVB application might require a lower bit-error-rate (BER) than a WSN application, whereas a WSN application might impose a much stricter energy efficiency constraint on the LDPC decoding than its DVB counterpart. Therefore an LDPC decoding algorithm whose BER performance can be traded-off with respect to its energy efficiency is highly desirable. |
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We propose a sparse LDPC decoding algorithm that delivers near-identical BER performance as the “sum-product” decoder (delivering the optimal BER performance) while significantly reducing the entropy of LDPC messages. At the core of the proposed decoding algorithm is “margin propagation” which is a piecewise linear (PWL) approximation of the log-sum-exp function used in “sum-product” decoding. An attractive property, other than sparsity, of “margin-propagation” based LDPC decoding is that the algorithm can be parameterized which enables one to elegantly trade-off BER performance with respect to message sparsity and hence the energy efficiency of the decoder. |
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Moreover, we accomplish an analog current mode implementation of an MP-based (32,8) LDPC decoder. The implementation uses only addition, subtraction and threshold operations and hence is independent of transistor biasing. Measured results from prototypes fabricated in a 0.5um CMOS process verify the functionality of a (32,8) LDPC decoder and demonstrate the trade-off capability which is realized by adapting a system hyper-parameter. When configured as a min-sum LDPC decoder, the proposed implementation demonstrates superior BER performance compared to the state-of-the-art analog min-sum decoder at SNR greater than 3.5 dB. We show that an optimal configuration of the same MP-based decoder can also deliver up to 3 dB improvement in BER compared to the benchmark min-sum LDPC decoder. |
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High-speed communication systems High density storage systems (CD readers, hard-disk)
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