Abstract
Interference alignment (IA) and rate splitting (RS) are two promising interference processing techniques to handle the interference problems in the multi-input multi-output (MIMO) multi-cell cooperation scenario. However, under the imperfect channel state information (CSIT) in the practical systems, the poor robustness of IA has become a bottleneck of its performance gain. On the other hand, RS can provide a robust solution, yet its outage performance is limited by its SIC decoding process. To make up these two schemes’ shortcomings and achieve the robust and reliable multi-cell cooperation, in this paper, we propose a novel transmission scheme, signal and interference alignment based rate splitting (SIA-RS), and provide comprehensively analyze the performance under CSIT quantization error. Closed-from expressions are derived for the average sum rate, outage probability and symbol error rate (SER) and their asymptotic versions in high signal-to-noise ratio (SNR) region. Due to signal alignment and common message, there exists certain correlation between the key variables. The nested finite weighted sum of independent and correlated Erlang random variables is used to approximate the exact expressions of performance. The relationship between “splitting” and “alignment” is revealed via the analytical derivation and numerical simulation. The simulation results show that the proposed SIA-RS achieves the best average sum rate compared with conventional IA and RS schemes, indicate that alignment would further reduce the outage probability, and suggest to the separate modulation schemes for common and private messages in terms of SER.
Highlights
To satisfy the ever increasing demand of explosive growth of traffic for high date and mobility, the network deployment tends to be more ultra-dense and complicated, resulting in more severe interference
In this paper, we proposed a novel transmission scheme named by signal and interference alignment based rate splitting (SIA-RS), and comprehensively analyzed the performance under channel state information (CSIT) quantization error via giving the closed-from expressions of average sum rate, outage probability and symbol error rate (SER) and their asymptotic versions under the high signal-to-noise ratio (SNR)
Differing from conventional transmission, due to signal alignment and common message, there existed the correlation between key variables
Summary
To satisfy the ever increasing demand of explosive growth of traffic for high date and mobility, the network deployment tends to be more ultra-dense and complicated, resulting in more severe interference. Reference [6] claims that RS can obtain the optimal generalized DoF (GDoF) in K -user interference channel under finite precision CSIT These studies confirm that RS is robust to imperfect CSIT from the perspective of information theory. Based on the closed-from formulas, the simulation results illustrate that the proposed SIA-RS has the best average sum rate compared with conventional IA and RS schemes, verify that alignment can further improve the outage probability, and enlighten us as to the separate modulation schemes for common and private messages. E{·} denotes the expectation operators. vec(·) and rvec(·) denote the vectorization operator and its inverse transform, respectively
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