A Variational Inference Framework for Soft-In Soft-Out Detection in Multiple-Access Channels
A Variational Inference Framework for Soft-In Soft-Out Detection in Multiple-Access Channels
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DOI：
10.1109/tit.2009.2016054
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发表时间：
2008-08
影响因子：
2.5
通讯作者：
D. Lin;Teng Joon Lim
中科院分区：
文献类型：
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作者：
D. Lin;Teng Joon Lim
我们提出了一个统一的框架，推导和研究软在软出（SISO）检测在多址信道中使用变分推理的概念。所提出的框架可以用于多址干扰（MAI）、符号间干扰（ISI）和多输入多输出（MIMO）信道。不失一般性，我们将集中我们的注意力在涡轮多用户检测，以促进更具体的讨论。结果表明，与一些损失的最优性，变分推理避免了指数复杂的后验概率（APP）检测优化密切相关的，但更易于管理，目标函数称为变分自由能。除了系统的吸引力之外，这种观点还有其他几个优点。首先，它提供了统一的和严格的理由，提出了许多检测器从根本上不同的理由，并方便联合检测和解码（利用涡轮原理）时，错误控制码被纳入。第二，有效的联合参数估计和数据检测是可能的，通过变分期望最大化（EM）算法，使得在接收机不准确的信道知识的不利影响可以系统地处理。我们还能够扩展基于BPSK的SISO检测方案，以严格的方式使用变分参数的任意平方QAM星座。
We propose a unified framework for deriving and studying soft-in soft-out (SISO) detection in multiple-access channels using the concept of variational inference. The proposed framework may be used in multiple-access interference (MAI), intersymbol interference (ISI), and multiple-input multiple-output (MIMO) channels. Without loss of generality, we will focus our attention on turbo multiuser detection, to facilitate a more concrete discussion. It is shown that, with some loss of optimality, variational inference avoids the exponential complexity of a posteriori probability (APP) detection by optimizing a closely related, but much more manageable, objective function called variational free energy. In addition to its systematic appeal, there are several other advantages to this viewpoint. First of all, it provides unified and rigorous justifications for numerous detectors that were proposed on radically different grounds, and facilitates convenient joint detection and decoding (utilizing the turbo principle) when error-control codes are incorporated. Second, efficient joint parameter estimation and data detection is possible via the variational expectation maximization (EM) algorithm, such that the detrimental effect of inaccurate channel knowledge at the receiver may be dealt with systematically. We are also able to extend BPSK-based SISO detection schemes to arbitrary square QAM constellations in a rigorous manner using a variational argument.