Rate-splitting multiple access (RSMA) is an emerging multiple access technique for multi-antenna networks that splits messages into common and private parts for flexible interference mitigation. Motivated by its robustness and scalability, it is promising to employ RSMA in integrated satellite-terrestrial networks (ISTN), where a satellite serves satellite users (SUs) broadly with a multibeam multicast transmission while terrestrial base station (BS) serves cellular users (CUs) with a unicast transmission, operating in the same frequency band. To avoid the data exchange between satellite/cellular networks via backhaul, we assume a coordinated ISTN relying on imperfect channel state information. We put forth a coordinated RSMA framework tailored to the coordinated ISTN by applying inter-network rate-splitting (RS) with a super-common message on top of intra-network RS with common/private messages. With the unified RS design for inter- and intra-networks, we jointly optimize the precoding and power allocation of the private/common/super-common messages to achieve max-min fairness among all SUs and CUs through successive convex approximation. By doing so, the power of the super-common message can be adjusted according to interference levels of the satellite towards CUs, thereby potentially mitigating inter-network interference. Simulation results demonstrate the superiority and robustness of our approach to cope with various interference and propagation conditions.

翻译：速率分裂多址接入（RSMA）是一种新兴的多天线网络多址技术，通过将消息分裂为公共部分和私有部分以实现灵活的干扰抑制。鉴于其鲁棒性和可扩展性，在星地一体化网络（ISTN）中采用RSMA具有广阔前景——其中卫星通过多波束组播传输广泛服务卫星用户（SUs），而地面基站（BS）通过单播传输服务蜂窝用户（CUs），且两者工作在相同频段。为避免通过回传链路进行星地网络间的数据交换，我们假设基于非完美信道状态信息的协调型ISTN。通过在内网RS（含公共/私有消息）基础上引入带超公共消息的网间速率分裂（RS），我们提出了一种适配协调型ISTN的协调RSMA框架。基于内外网的统一RS设计，我们通过逐次凸近似联合优化私有/公共/超公共消息的预编码与功率分配，以实现所有SUs和CUs间的最大最小公平性。这样一来，超公共消息的功率可根据卫星对CUs的干扰水平动态调节，从而有效抑制网间干扰。仿真结果证明了该方法应对多种干扰与传播条件的优越性和鲁棒性。