Abdollahi Bafghi Ali H, Mirmohseni Mahtab, Nasiri-Kenari Masoumeh
Department of Electrical Engineering, Sharif University of Technology, Tehran P932+FM4, Iran.
Institute for Communication Systems (ICS), University of Surrey, Guildford GU2 7XH, UK.
Entropy (Basel). 2022 Aug 4;24(8):1078. doi: 10.3390/e24081078.
In this paper, we study the degrees of freedom (DoF) of a frequency-selective -user interference channel in the presence of an instantaneous relay (IR) with multiple receiving and transmitting antennas. We investigate two scenarios based on the IR antennas' cooperation ability. First, we assume that the IR receiving and transmitting antennas can coordinate with each other and that the transmitted signal of each transmitting antenna can depend on the received signals of all receiving antennas, and we derive lower and upper bounds for the sum DoF of this model. In an interference alignment scheme, we divide receivers into two groups called clean and dirty receivers. We design our scheme such that a part of the messages of clean receivers can be de-multiplexed at the IR. Thus, the IR can use these message streams for an interference cancellation at the clean receivers. Next, we consider an IR, the antennas of which do not have coordination with each other and where the transmitted signal of each transmitting antenna depends only on the received signal of its corresponding receiving antenna. We also derive lower and upper bounds for the sum DoF for this model of IR. We show that the achievable sum DoF decreases considerably compared with the coordinated case. In both of these models, our schemes achieve the maximum sum DoF if the number of transmitting and receiving antennas is more than a finite threshold.
在本文中，我们研究了存在具有多个收发天线的即时中继（IR）时频率选择性多用户干扰信道的自由度（DoF）。我们基于IR天线的协作能力研究了两种场景。首先，我们假设IR的收发天线可以相互协调，并且每个发射天线的发射信号可以依赖于所有接收天线的接收信号，然后我们推导了该模型和自由度的上下界。在一种干扰对齐方案中，我们将接收机分为两组，称为干净接收机和脏接收机。我们设计我们的方案，使得干净接收机的部分消息可以在IR处进行解复用。这样，IR就可以使用这些消息流在干净接收机处进行干扰消除。接下来，我们考虑一种IR，其天线之间没有相互协调，并且每个发射天线的发射信号仅依赖于其相应接收天线的接收信号。我们也推导了这种IR模型和自由度的上下界。我们表明，与协调情况相比，可实现的和自由度大幅降低。在这两种模型中，如果收发天线的数量超过一个有限阈值，我们的方案都能实现最大和自由度。
