Abstract
Multiple-inputs multiple-outputs (MIMO) technology, including massive MIMO, plays an important role in modern wireless communication systems. Massive MIMO systems with high-order modulation can promote spectrum efficiency. The algorithm complexity and detection performance are the main challenges for the massive MIMO system. Thus, the low complexity and high-performance MIMO detector is important for the practical massive MIMO application. The Expectation Propagation (EP) detector outperforms many conventional detectors in high-order massive MIMO scenarios. However, its complexity increases exponentially with the number of sending antennas and the modulation order. In this paper, we propose a novel information updating scheme for EP MIMO detection algorithm to achieve high performance with low complexity. The high-efficiency EP detector is based on the expectation propagation algorithm with the jointed scheme of successive updating, sorting updating and sphere search aided algorithm. Numerical results show the high-efficiency EP detector reduces over 85% complexity of the original EP detector for the scenario $N_{t}=N_{r}=20$ with 64-QAM modulation, and the gain on complexity becomes more evident with the increase of antenna scale and the modulation order. The high-efficiency EP detector can outperform the original EP detector in different high-order massive scenarios. Compared with MMSE algorithm, the proposed scheme can get huge performance gain with 1.5 times complexity for high-order massive MIMO systems.
Highlights
Multiple-inputs multiple-outputs (MIMO) technology is one of the key technologies in modern wireless communication systems
Where ρ is a parameter to balance the complexity and performance. Another worthy mentioned thing, when ρ in (29) is determined, the radius of search space depends on the value of variance εi2(l) of the first iteration, which is totally depended on the adopted scheme of MIMO detector
When the MIMO system suffers from heavy load, Expectation Propagation (EP) detectors show a great advantage over the MMSE detector and the proposed high-efficiency EP detector can further improve the symbols error rate (SER) performance of the original EP detector with below 12.5% (α1 = 0.25, α3 = 0.5) of its complexity
Summary
MIMO technology is one of the key technologies in modern wireless communication systems. To improve the mentioned drawbacks of the original EP detector, we propose a novel information updating algorithm to achieve high-efficiency EP detector for high-order massive MIMO systems. To reduce the huge calculation load in the updating process for high order modulations, the high-efficiency EP detector adopts the sphere search aided (SSA), which can decrease the number of mathematical operations without performance loss. It reduces the complexity of the original. The proposed high-efficiency EP detector can reduce the complexity of the original EP detector in a single iteration and speed up the convergence, which improves the practicability of the EP algorithm in MIMO symbols detection.
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