Abstract
In Spatial Modulation (SM), the information bits are split into two streams: one is mapped to a conventional complex signal modulation, and the other is used to select the active transmit antenna. Transmission SM schemes can be implemented with a single RF chain, allowing for a low-complexity transmitterwith relatively large spectral efficient. In this paper, we are concerned with coded SM schemes. In the literature, the usual approach considers a single encoder that jointly encodes both bit streams. In this work, we propose a coded SM system in which each of the information streams is encoded by a possibly different low-density parity-check (LDPC) code. The two LDPC codes are designed after selecting the code rates according to the mutual information associated with the two corresponding subchannels, for a fixed, reference signal-to-noise ratio (SNR). A two-layer, iterative message-passing decoder is developed, where the two component decoders exchange soft information. Through Monte Carlo simulations, we show that the bit error rate of the proposed scheme is low when the SNR is greater or equal to the reference SNR, demonstrating the strength of the proposed two-layer approach.
Highlights
W IRELESS communication systems using multiple transmit and receive antennas, i.e., multiple-input, multiple-output (MIMO) systems, have received wide attention in the last decades [2], [3], [4], as they are capable of achieving considerable gains in terms of diversity [3], [4] and/or capacity [5] over the systems with single transmit and receive antenna (SISO) [1].Recently, spatial modulation (SM) [6] has emerged as an attractive MIMO technique, where the indexes of the transmit antennas are exploited as an additional dimension
It is important to point out that this coding technique is applied in the formation of the codewords ca and cs, and presents as characteristics: flexibility in the choice of low-density parity-check (LDPC) rates, the low complexity involved in the processes since the matrix H is sparse, and the matrix H2 has no cycles of length 4 and has a few cycles of length 6
We explore in the present work the use of the extrinsic information generated at the output of the sum-product decoding algorithm (SPA) decoder for the LDPC code used in the signal modulation to provide a priori probabilities for the input of the detector of the LDPC code used for spatial modulation, and vice-versa
Summary
W IRELESS communication systems using multiple transmit and receive antennas, i.e., multiple-input, multiple-output (MIMO) systems, have received wide attention in the last decades [2], [3], [4], as they are capable of achieving considerable gains in terms of diversity [3], [4] and/or capacity [5] over the systems with single transmit and receive antenna (SISO) [1]. In [13], a non-binary LDPC-SM system in both one- and two-layer configurations have been shown to achieve good performance, at the expenses of a high decoding complexity due to non-binary field operations Another two-layer scheme was proposed in [14], wherein each information sequence is encoded by a block Markov superposition transmission (BMST) scheme, with iterations between the component decoders. Design and implementation of a two-layer binary LDPC coding scheme for SM, where the two information bit streams (associated with spatial and conventional modulations) are separately encoded. The evaluation of the mutual information of the two transmitted bit streams and the received signal as a way to select the component code rates. In [14], a SM-MIMO system is proposed with BMST encoding where two transmit antennas are enabled and higher order modulation are utilized in the two-layer total approach
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