With the ubiquitous demand for wireless communications, researchers have studied heterogeneous networks (HetNets) for years. Often the HetNets include a macrocell base station (MBS), several sets of macrocell users (MUs), a large number of femtocell base stations (FBSs), and femtocell users (secondary users), where the femtocells help the macrocell system relay the uplink or downlink traffic between the MUs and the MBS. In this article, we propose a novel joint information and energy cooperation method, with the aim of enhancing the spectrum and energy efficiency (EE) for cognitive HetNets. Specifically, the MUs and the femtocells harvest wireless energy from the radio frequency signal transmitted by MBS. By using the harvested energy, femtocells obtain the transmission opportunity to forward the signals of their serving users. We theoretically derive the theoretical expressions of the outage probabilities of the primary link as well as the secondary link. Then, we focus on investigating how to maximize EE by jointly considering time allocation and power control. Furthermore, we formulate the EE maximization problem, which contains the fractional form objective function and the linear inequality constraints and hence is nonconvex. To resolve this, we integrate the Dinkelbach method with convex optimization to derive the tractable and optimal solution. The numerical results demonstrate the simulations well match our theoretical analysis. Moreover, the results validate the feasibility of the proposed method for high-quality transmission without incurring extra energy consumption.

中文翻译：

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启用CR的宏-毫微微异构网络的联合信息和能源合作框架

随着对无线通信的普遍需求，研究人员已经研究了异构网络（HetNets）多年。HetNet通常包括宏小区基站（MBS），几组宏小区用户（MU），大量的毫微微小区基站（FBS）和毫微微小区用户（辅助用户），其中，毫微微小区可以帮助宏小区系统中继上行链路MU和MBS之间的下行流量。在本文中，我们提出了一种新颖的联合信息和能量合作方法，旨在增强认知HetNet的频谱和能量效率（EE）。具体而言，MU和毫微微小区从MBS传输的射频信号中收集无线能量。通过利用所收集的能量，毫微微小区获得了传输其服务用户的信号的传输机会。从理论上讲，我们得出了主要链接和次要链接中断概率的理论表达式。然后，我们重点研究如何通过共同考虑时间分配和功率控制来最大化EE。此外，我们制定了EE最大化问题，该问题包含分数形式的目标函数和线性不等式约束，因此是非凸的。为了解决这个问题，我们将Dinkelbach方法与凸优化相结合，以得出易于处理的最优解。数值结果表明，仿真与我们的理论分析非常吻合。而且，结果证实了所提出的方法用于高质量传输的可行性，而不会引起额外的能量消耗。