This work does the statistical quality-of-service (QoS) analysis of a block-fading device-to-device (D2D) link in a multi-tier cellular network that consists of a macro-BS (BSMCBS_{_{MC}}) and a micro-BS (BSmCBS_{_{mC}}) which both operate in full-duplex (FD) mode. For the D2D link under consideration, we first formulate the mode selection problem—whereby D2D pair could either communicate directly, or, through the BSmCBS_{_{mC}}, or, through the BSMCBS_{_{MC}}—as a ternary hypothesis testing problem. Next, to compute the effective capacity (EC) for the given D2D link, we assume that the channel state information (CSI) is not available at the transmit D2D node, and hence, it transmits at a fixed rate rr with a fixed power. This allows us to model the D2D link as a Markov system with six-states. We consider both overlay and underlay modes for the D2D link. Moreover, to improve the throughput of the D2D link, we assume that the D2D pair utilizes two special automatic repeat request (ARQ) schemes, i.e., Hybrid-ARQ (HARQ) and truncated HARQ. Furthermore, we consider two distinct queue models at the transmit D2D node, based upon how it responds to the decoding failure at the receive D2D node. Eventually, we provide closed-form expressions for the EC for both HARQ-enabled D2D link and truncated HARQ-enabled D2D link, under both queue models. Noting that the EC looks like a quasi-concave function of rr, we further maximize the EC by searching for an optimal rate via the gradient-descent method. Simulation results provide us the following insights: i) EC decreases with an increase in the QoS exponent, ii) EC of the D2D link improves when HARQ is employed, iii) EC increases with an increase in the quality of self-interference cancellation techniques used at BSmCBS_{_{mC}} and BSMCBS_{_{MC}} in FD mode.

中文翻译：

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多层蜂窝网络中启用 HARQ 的 D2D 通信的有效容量分析


这项工作对由宏 BS (BSMCBS_{_{MC}} 组成的多层蜂窝网络中的块衰落设备到设备 (D2D) 链路进行统计服务质量 (QoS) 分析。 ）和微基站（BSmCBS_{_{mC}}）均以全双工（FD）模式运行。对于所考虑的 D2D 链路，我们首先将模式选择问题表述为三元组，其中 D2D 对可以直接通信，或者通过 BSmCBS_{_{mC}} 通信，或者通过 BSMCBS_{_{MC}} 通信假设检验问题。接下来，为了计算给定 D2D 链路的有效容量 (EC)，我们假设信道状态信息 (CSI) 在发送 D2D 节点处不可用，因此，它以固定速率 rr 和固定功率进行发送。这使我们能够将 D2D 链路建模为具有六种状态的马尔可夫系统。我们考虑 D2D 链路的覆盖和底层模式。此外，为了提高D2D链路的吞吐量，我们假设D2D对使用两种特殊的自动重复请求（ARQ）方案，即混合ARQ（HARQ）和截断HARQ。此外，我们根据发送 D2D 节点如何响应接收 D2D 节点的解码失败，考虑了两种不同的队列模型。最终，我们在两种队列模型下为支持 HARQ 的 D2D 链路和截断的支持 HARQ 的 D2D 链路的 EC 提供闭合形式的表达式。注意到 EC 看起来像 rr 的拟凹函数，我们通过梯度下降方法搜索最佳速率来进一步最大化 EC。 仿真结果为我们提供了以下见解：i) EC 随着 QoS 指数的增加而降低，ii) 当采用 HARQ 时，D2D 链路的 EC 会提高，iii) EC 随着所使用的自干扰消除技术质量的提高而增加在 FD 模式下的 BSmCBS_{_{mC}} 和 BSMCBS_{_{MC}}。