双向网络：当适应无用时
Two-way Networks: when Adaptation is Useless
摘要：
在双向网络中，节点同时充当消息的源和目的地。这允许节点处的“适配”或节点之间的“交互”-节点的信道输入可以是其消息和先前接收的信号的函数。如何最好地适应是双向沟通的关键，这使得它具有挑战性。然而，存在点对点信道的示例，其中从容量的角度来看，适配不是有益的。我们问是否存在类似的多用户双向网络的例子。我们首先考虑确定性的双向信道模型：二进制模2加法信道及其推广，以及线性确定性信道。对于这些确定性模型，我们得到的双向多址/广播信道，双向Z信道和双向干扰信道（IC）的容量区域。在所有情况下，我们允许所有节点将通道输入适配到过去的输出（除了线性确定性双向IC的部分，其中我们仅允许4个节点中的2个完全适配）。然而，我们表明，这种适应是无用的，从容量区域的角度来看，容量是通过策略，在每次使用的通道输入不适应以前的输入。最后，我们考虑了高斯双向集成电路，并表明部分自适应是无用的干扰时，是非常强的。在强和弱干扰制度，我们表明，在两个方向上并行使用的非自适应韩和小林计划实现在一个恒定的间隙内的对称率的完全（某些制度）或部分（剩余制度）自适应模型。核心的技术贡献是推导出新的，可计算的外部边界，允许适应。内界遵循相应的单向信道模型的非自适应可扩展性方案。
英文摘要：
In two-way networks, nodes act as both sources and destinations of messages. This allows for "adaptation" at or "interaction" between the nodes - a node's channel inputs may be functions of its message(s) and previously received signals. How to best adapt is key to two-way communication, rendering it challenging. However, examples exist of point-to-point channels where adaptation is not beneficial from a capacity perspective. We ask whether analogous examples exist for multi-user two-way networks. We first consider deterministic two-way channel models: the binary modulo-2 addition channel and a generalization thereof, and the linear deterministic channel. For these deterministic models we obtain the capacity region for the two-way multiple access/broadcast channel, the two-way Z channel and the two-way interference channel (IC). In all cases we permit all nodes to adapt channel inputs to past outputs (except for portions of the linear deterministic two-way IC where we only permit 2 of the 4 nodes to fully adapt). However, we show that this adaptation is useless from a capacity region perspective and capacity is achieved by strategies where the channel inputs at each use do not adapt to previous inputs. Finally, we consider the Gaussian two-way IC, and show that partial adaptation is useless when the interference is very strong. In the strong and weak interference regimes, we show that the non-adaptive Han and Kobayashi scheme utilized in parallel in both directions achieves to within a constant gap for the symmetric rate of the fully (some regimes) or partially (remaining regimes) adaptive models. The central technical contribution is the derivation of new, computable outer bounds which allow for adaptation. Inner bounds follow from non-adaptive achievability schemes of the corresponding one-way channel models.
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