Abstract
The channel estimation and data detection of orthogonal frequency-division multiplexing with index modulation in doubly selective channels is a challenging problem due to the large number of channel parameters and the severe inter-carrier interference. In this paper, an iterative channel estimation and data detection scheme is proposed with the aid of the recent compressed sensing algorithm of approximate message passing (AMP). The time-varying channel is first approximated by basis expansion model (BEM) to reduce the number of channel parameters to be estimated, and AMP is utilized to estimate the BEM coefficients based on the pilot signals and soft information of data from the decoder. The channel is then reconstructed from the estimated BEM coefficients, and AMP is also employed to recover the transmit data based on the estimated channel and soft information of data from the decoder. The soft information of AMP detector is further sent to the decoder, which feeds soft information to both AMP estimator and AMP detector. To address the undesired measurement matrix in both channel estimation and data detection, two variants of AMP, i.e., damped AMP and vector AMP (VAMP), are utilized as practical estimator and/or detector here. Moreover, in both damped AMP/VAMP estimator and detector, the efficient utilization of soft data information is presented. Finally, simulation results are given to verify the performance of the proposed receiver.
Highlights
Orthogonal frequency division multiplexing with index modulation (OFDM-IM) is a novel multi-carrier modulation technique [1]–[3]
SIMULATION RESULTS the bit error rate (BER) performance of the proposed damped approximate message passing (AMP)/vector AMP (VAMP) channel estimator and AMP/VAMP detector is given by computer simulations
When damped AMP detector is used, damped AMP estimator and damped VAMP estimator show similar performance. This can be partly interpreted by the fact that the activation patterns (APs) constraint of OFDM-IM is not taken into account fully in the first global iteration in the damped VAMP detector
Summary
Orthogonal frequency division multiplexing with index modulation (OFDM-IM) is a novel multi-carrier modulation technique [1]–[3]. In [31], an expectation maximization (EM)-based blind channel estimator with the framework of BEM for the OFDM system was proposed by utilizing the historical information of high speed railways. In [35], a turbo iterative receiver consisting of LMMSE BEM channel estimation, LMMSE data detection and maximum a posterior (MAP) decoding was proposed. Motivated by the good signal recovery performance and computationally efficient implementation of damped AMP and VAMP for general measurement matrix, in this paper, we propose to extend our early work in [38] to turbo receiver [35], [36] consisting of channel estimator, data detector, and channel decoder. Channel estimators are derived for BEM-based DSCs. It is found that the proposed AMP estimator can achieve nearly the same performance as LMMSE estimator with much lower computational complexity. For two vectors x and y with the same size, x/y denotes the component-wise division
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