Due to the development of communication technology and the rise of user network demand, a reasonable resource allocation for wireless networks is the key to guaranteeing regular operation and improving system performance. Various frequency bands exist in the natural network environment, and heterogeneous cellular network (HCN) has become a hot topic for current research. Meanwhile, Reconfigurable Intelligent Surface (RIS) has become a key technology for developing next-generation wireless networks. By modifying the phase of the incident signal arriving at the RIS surface, RIS can improve the signal quality at the receiver and reduce co-channel interference. In this paper, we develop a RIS-assisted HCN model for a multi-base station (BS) multi-frequency network, which includes 4G, 5G, millimeter wave (mmwave), and terahertz networks, and considers the case of multiple network coverage users, which is more in line with the realistic network characteristics and the concept of 6G networks. We propose the optimization objective of maximizing the system sum rate, which is decomposed into two subproblems, i.e., the user resource allocation and the phase shift optimization problem of RIS components. Due to the NP-hard and coupling relationship, we use the block coordinate descent (BCD) method to alternately optimize the local solutions of the coalition game and the local discrete phase search algorithm to obtain the global solution. In contrast, most previous studies have used the coalition game algorithm to solve the resource allocation problem alone. Simulation results show that the algorithm performs better than the rest of the algorithms, effectively improves the system sum rate, and achieves performance close to the optimal solution of the traversal algorithm with low complexity.

翻译：随着通信技术的发展及用户网络需求的增长，无线网络的合理资源分配是保障系统正常运行及提升性能的关键。自然网络环境中存在多种频段，异构蜂窝网络（HCN）已成为当前研究热点。与此同时，可重构智能表面（RIS）已成为下一代无线网络发展的关键技术。通过调整到达RIS表面的入射信号相位，RIS能够改善接收端信号质量并降低同频干扰。本文针对包含4G、5G、毫米波（mmwave）及太赫兹网络的多基站（BS）多频网络场景，构建了RIS辅助的HCN模型，并考虑了多网络覆盖用户的情形，更符合现实网络特征及6G网络理念。我们提出以最大化系统总和速率为优化目标，并将其分解为用户资源分配与RIS组件相移优化两个子问题。鉴于问题的NP难及耦合特性，我们采用块坐标下降（BCD）方法交替优化联盟博弈的局部解，并利用局部离散相位搜索算法获取全局解。与以往大部分研究单独使用联盟博弈算法求解资源分配问题不同，仿真结果表明该算法性能优于其他算法，有效提升了系统总和速率，并以低复杂度实现了接近遍历算法最优解的性能。