Resource Allocation for Active Channels

在过去的十年中，中继辅助通信一直是密集研究的中心焦点。在单向或双向中继网络的上下文中已经提出了包括放大和转发、解码和转发、估计和转发在内的多种依赖策略，其目的是实现一对或多对源-目的地之间的通信或实现一对或多对收发机之间的信息交换。事实证明，中继信道属于更大类别的信道，即活动信道，其中信道行为可以在信道两端之间的某个位置进行调整，以获得最佳性能。这种通道可调整性在传统的通道模型中不存在(在此它们被称为被动通道)。事实上，在传统的无线信道模型中，端到端信道通常是给定的，并且对信道行为没有控制。为了补偿信道，必须在发射机上采用预编码和/或在接收机上均衡信道。*在活动信道中，除了发射机上的信号预编码和/或接收机上的信道均衡外，还可以调整信道本身。例如，在中继信道中，通过明智地设计中继操作并根据信道特性以及信号预编码操作和接收侧信道均衡来优化一定的性能度量，可以仔细地确定端到端信道冲激响应。申请人通过在著名期刊上发表的几篇论文，即IEEE信号处理会刊(两篇论文)和IEEE信号处理快报(一篇论文)，率先在活跃的渠道进行研究。在这些已发表的结果中，研究了具有相等子信道噪声功率的单向有源并行信道、具有不等子信道噪声功率的单向有源并行信道和具有相同噪声功率的双向有源并行信道的和速率最大化问题。在所有这些研究成果中，有一个共同的假设：不同子信道上的接收信噪比(SNR)与信道增益的平方成线性关系。基于该假设，然后在单向方案中的源的发射功率(或在双向方案中的不同子信道上的两个收发机的发射机功率)上最大化和速率。在这份提案中，申请人详细介绍了一项研究计划，该计划允许为活动信道进行最佳资源分配。这是通过引入更一般的(非线性)模型来描述子信道SNR和子信道增益来实现的。这样的任务要求这个项目专注于研究不同的绩效衡量标准。这项研究计划将研究并行通道，目的是将数据速率提高到超过当前网络数据速率的水平。**

In the past decade, relay-assisted communications have been the center focus of intensive research studies. Numerous relying strategies, including amplify-and-forward, decode-and-forward, estimate-and-forward, have been proposed in the context of one-way or two-way relay-networks with the aim to enable communications between one or more pairs of source-destination or to enable information exchange between one or more pairs of transceivers. It turns out that the relay channel belongs to a larger class of channels, namely active channels, where the channel behavior can be adjusted, for optimal performance, somewhere between the two ends of the channel. Such channel adjustability does not exist in traditional channel models (which they are herein referred to as passive channels). Indeed in traditional models of wireless channels, the end-to-end channel is often given and there is no control on the channel behavior. To compensate the channel, one has to either resort to precoding at the transmitter and/or equalize the channel at the receiver. ***In active channels, the channel itself can be adjusted in addition to signal precoding at the transmitter and/or channel equalization at the receiver. For example, in a relay channel, the end-to-end channel impulse response can be carefully determined through judiciously designing the relaying operation and optimizing a certain performance metric over the channel characteristics and over the signal precoding operation and receiver side channel equalization. The applicant has pioneered the research in active channels through several publications which appeared in prestigious periodicals, namely IEEE Transactions on Signal Processing (two papers) and IEEE Signal Processing Letters (one paper). In these published results, the problem of sum-rate maximization has been studied for i) one-way active parallel channels with equal sub-channel noise powers, ii) one-way active parallel channels with unequal subchannel noise powers, and iii) two-way active parallel channels with equal noise powers. In all these research outcomes, there is one common assumption: the received signal-to-noise ratios (SNRs) over different sub-channels are linearly related to the channel gains squared. Based on this assumption, then the sum-rate is maximized over the transmit powers of the source in one-way schemes (or the transmitter powers of the two transceivers over different sub-channels in two-way schemes). In this proposal, the applicant details a research program that allows optimal resource allocation for active channels. This is achieved by introducing more general (nonlinear) models to describe the sub-channel SNRs and sub-channel gains. Such a task requires this program to focus on studying different performance measures. This research program will study parallel channels with the aim to increase the data rate beyond current network data rates. **