In conventional backscatter communication (BackCom) systems, time division multiple access (TDMA) and frequency division multiple access (FDMA) are generally adopted for multiuser backscattering due to their simplicity in implementation. However, as the number of backscatter devices (BDs) proliferates, there will be a high overhead under the traditional centralized control techniques, and the inter-user coordination is unaffordable for the passive BDs, which are of scarce concern in existing works and remain unsolved. To this end, in this paper, we propose a slotted ALOHA-based random access for BackCom systems, in which each BD is randomly chosen and is allowed to coexist with one active device for hybrid multiple access. To excavate and evaluate the performance, a resource allocation problem for max-min transmission rate is formulated, where transmit antenna selection, receive beamforming design, reflection coefficient adjustment, power control, and access probability determination are jointly considered. To deal with this intractable problem, we first transform the objective function with the max-min form into an equivalent linear one, and then decompose the resulting problem into three sub-problems. Next, a block coordinate descent (BCD)-based greedy algorithm with a penalty function, successive convex approximation, and linear programming are designed to obtain sub-optimal solutions for tractable analysis. Simulation results demonstrate that the proposed algorithm outperforms benchmark algorithms in terms of transmission rate and fairness.
翻译:在常规的后向散射通信系统(BackCom)中,由于执行过程的简单性,对多用户反向反向访问(FDMA)通常采用时分多重访问(TDMA)和频率分多重访问(FDMA),但是,随着后向散射装置(BDs)数量激增,传统集中控制技术下将会出现高间接费用,用户间协调对于被动的双向散射通信系统来说是负担不起的,而被动的双向散射系统在现有工作中是很少引起关注的,但仍未解决。为此,我们在本文件中,我们提议为后向系统系统提供一个基于时间档的ALOHA随机访问(ALOHA),其中每个双向选择BD,并允许与一个运行混合多重访问的主动设备共存。要挖掘和评估业绩,将最大量传输设备传输率的资源分配问题,在传输天线选择、反应系数调整、权力控制和访问概率概率确定。为了解决这一棘手问题,我们首先将目标函数转换成一个对应的线性直线性版本,然后将Slimeximexalimex imex commabal prill comlial compal 函数转换成一个问题。