In this paper, the sum-rate maximization problem is studied for wireless networks that use downlink rate splitting multiple access (RSMA). In the considered model, the base station (BS) divides the messages that can be transmitted to its users into a “private” part and a “common” part. Here, the common message is a message that multiple users want to receive and the private message is a message that is dedicated to only a specific user. The RSMA mechanism enables a BS to adjust the split of common and private messages so as to control the interference by decoding and treating interference as noise and, thus optimizing the data rate of users. To maximize the users’ sum-rate, the network can determine the rate allocation for the common message to meet the rate demand, and adjust the transmit power for the private message to reduce the interference. This problem is formulated as an optimization problem whose goal is to maximize the sum-rate of all users. To solve this nonconvex maximization problem with a single-antenna BS, the optimal power used for transmitting the private message to the users is first obtained in closed form for a given rate allocation and common message power. Based on the optimal private message transmit power, the optimal rate allocation is then derived under a fixed common message transmit power. Subsequently, an iterative algorithm is proposed to obtain a suboptimal solution of common message transmit power. To solve this nonconvex maximization problem with a multiple-antenna BS, a successive convex approximation method is utilized. Simulation results show that the RSMA can achieve up to 15.6% and 21.5% gains in terms of data rate compared to non-orthogonal multiple access (NOMA) and orthogonal frequency-division multiple access (OFDMA), respectively.

中文翻译：

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速率分割多址 (RSMA) 的速率分配和功率控制优化


在本文中，研究了使用下行​​链路速率分割多址（RSMA）的无线网络的总速率最大化问题。在所考虑的模型中，基站（BS）将可以发送给其用户的消息分为“专用”部分和“公共”部分。这里，公共消息是多个用户想要接收的消息，而私人消息是仅专用于特定用户的消息。 RSMA机制使得BS能够调整公共消息和私有消息的分割，从而通过解码并将干扰视为噪声来控制干扰，从而优化用户的数据速率。为了最大化用户的总速率，网络可以确定公共消息的速率分配以满足速率需求，并调整专用消息的发射功率以减少干扰。该问题被表述为一个优化问题，其目标是最大化所有用户的总速率。为了解决单天线BS的非凸最大化问题，首先针对给定的速率分配和公共消息功率以封闭形式获得用于向用户发送私人消息的最佳功率。基于最优私有消息发射功率，然后导出在固定公共消息发射功率下的最优速率分配。随后，提出了一种迭代算法来获得公共消息发射功率的次优解。为了解决多天线基站的非凸最大化问题，采用了逐次凸逼近方法。仿真结果表明，RSMA可以达到15.6%和21。与非正交多址 (NOMA) 和正交频分多址 (OFDMA) 相比，数据速率分别提高了 5%。