Abstract
We develop a joint source-channel coding (JSCC) scheme based on an unequal power allocation strategy, in which different levels of power are allocated according to a priori probability distribution of the information bits. Two protograph low-density parity-check codes are used as the source code and the channel code, respectively, in the proposed JSCC scheme. With fixed row weight and row element alphabet, optimization on the source code is conducted via random search to obtain a best-found base matrix with the lowest decoding threshold among all the searched base matrices. Simulation results show that the new JSCC scheme outperforms the traditional equal power allocation-based JSCC by exploiting the source statistics at the decoder. Moreover, theoretical threshold analysis is in agreement with the practical simulation results.
Highlights
Joint source-channel coding (JSCC) has been intensively investigated in [1]–[5], which achieved significant gains compared with its conventional counterpart, i.e., separate sourcechannel coding (SSCC)
We introduce the methodology of unequal power allocation (UPA) into the protograph low-density parity-check (LDPC) codes assisted joint source-channel coding (JSCC) (P-JSCC) system [4], [5] for the transmission of nonuniform binary memoryless sources, where the source and channel codes are both unpunctured protograph LDPC codes
An attempt for optimizing the source code is introduced via random search while fixing the channel code, which provides a best-found base matrix with the lowest decoding threshold among all the searched base matrices according to the joint protograph extrinsic information transfer (JPEXIT) analysis
Summary
Joint source-channel coding (JSCC) has been intensively investigated in [1]–[5], which achieved significant gains compared with its conventional counterpart, i.e., separate sourcechannel coding (SSCC). The advantages of JSCC over SSCC lie in: (1) The residual redundancy left by the source encoder can be further exploited by the channel encoder/decoder, and even by the modulator/demodulator. Unequal power allocation (UPA) is realized by means of modulation. Significant performance improvement is achieved compared with the P-JSCC system with equal power allocation (EPA). Asymptotic performance is analyzed via joint protograph extrinsic information transfer (JPEXIT), developed in [5], to verify the superiority of the P-JSCC system with UPA over its EPA based counterpart. An attempt for optimizing the source code is introduced via random search while fixing the channel code, which provides a best-found base matrix with the lowest decoding threshold among all the searched base matrices according to the JPEXIT analysis
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