Massive MIMO Systems with Low-Resolution Analogue to Digital Conversion

The massive multiple-input multiple-output (MIMO) system is a key technology for future wireless systems. A practical obstacle for massive MIMO is the high cost of high-resolution analogue-to-digital (AD) and digital-to-analogue (DA) conversions. In a full digital implementation, each antenna requires an individual radio frequency (RF) chain with DA/AD converters. The related cost is a serious burden when the number of antennas is large.In this project, we will study the use of low-cost, low-resolution (LR) AD converter (ADC) for the up-link systems. We will develop advanced post-conversion signal processing algorithms and devise corresponding forward error control (FEC) coding techniques. Our proposed tasks combine the recent advances in iterative statistical signal processing and iterative decoding. The so-called turbo principle is a conventional technique to avoid correlation buildup during iterative processing. This technique can deliver nearly optimal performance in binary decoding, but it is not optimal when more complicated operations, such as channel estimation, interference cancellation and quantization compensation, are involved. In this project, we will study a novel decorrelation technique that allows more effective information exchange and, in the same time, avoids the correlation problem. We will study methods to match multiple local processors. Based on preliminary numerical results, we conjecture that this matching technique can offer near-optimal performance. We will rigorously verify this conjecture in the proposed project. We will also design algorithms that can provide good performance without resorting to costly matrix inversions.In our preliminary work, we observed that the new techniques outperform the conventional turbo technique as well as the state-of-the-art AMP (approximate message passing) technique in a broad range of massive MIMO channel conditions. These observations are very encouraging since the turbo and AMP techniques are among the most powerful tools for communication and signal processing systems available. The outcomes of this project will provide new insights and solutions to massive MIMO systems.