Device to device (D2D) communication is one of the most promising techniques for fifth-generation and beyond wireless communication systems. This paper considers coded caching in a wireless D2D network, in which a central server initially places the data in the user cache memories, and all user demands are served through inter-user coded multicast transmissions. D2D placement delivery array (DPDA) was proposed as a tool for designing coded caching schemes with reduced subpacketization levels in a D2D network. In this paper, we first constructed three classes of DPDAs using a cross resolvable design, a group divisible design, and a newly developed block design. The resulting D2D schemes achieve low subpacketization levels while meeting the known lower bound on the transmission load of a DPDA. These classes of constructed DPDAs either simplify or generalize all existing DPDA constructions that achieve the known lower bound and have low subpacketization levels. Furthermore, a new lower bound on the transmission load of a DPDA is proposed. Two new classes of DPDAs are then constructed using a cross resolvable design and a newly developed block design, respectively. These constructions yield low-subpacketization D2D schemes and achieve the proposed lower bound on the transmission load. Compared to existing schemes with the same system parameters as those obtained from the proposed DPDAs, the proposed schemes have an advantage in either transmission load or subpacketization level or both.

翻译：设备到设备（D2D）通信是第五代及未来无线通信系统中最具前景的技术之一。本文研究无线D2D网络中的编码缓存问题，其中中央服务器先将数据预存于用户缓存中，所有用户需求通过用户间的编码多播传输来满足。D2D放置交付阵列（DPDA）被提出作为设计D2D网络中低子分组化水平编码缓存方案的工具。本文首先利用交叉可分解设计、可分组设计及新构建的区组设计构造了三类DPDA。所得D2D方案在满足已知DPDA传输负载下界的同时实现了较低的子分组化水平。这些构造的DPDA类简化或推广了所有能达到已知下界且具有低子分组化水平的现有DPDA构造。此外，本文提出了DPDA传输负载的一个新下界，随后分别利用交叉可分解设计和新构建的区组设计构造了两类新的DPDA。这些构造产生了低子分组化D2D方案，并达到了所提传输负载下界。与采用和所提DPDA相同系统参数的现有方案相比，所提方案在传输负载或子分组化水平或两者兼备方面均具有优势。