Internet-of-things (IoT) applications continue to drive advancements in serving as many heterogeneous low-latency downlinks and uplinks as possible within a constrained communication bandwidth. Full-duplexing (FD) transceivers have been introduced to implement simultaneous signal transmission and reception (STR) over the entire available frequency band. However, both inter-link interference and FD loop-interference are hardly suppressed to a necessary level for the effectiveness of FD-based STR even for microcells. This paper proposes an alternative STR technique per one time-slot for macrocells, where a fraction of a time-slot is used for downlinks and the remaining complementary fraction of the time-slot is used for uplinks. Thus, STR over the entire available bandwidth can be implemented in a way with no loop interference. Furthermore, another approach of using a fraction of the available bandwidth for downlinks and the remaining complementary fraction of the bandwidth for uplinks over the whole time-slot is also proposed. The problem of both downlink and uplink beamforming to maximize the energy efficiency of such heterogeneous networks subject to the quality-of-service in terms of downlink and uplink throughput is examined for all three possible STRs. Numerical results demonstrate the advantages of the time-fraction-wise STR and bandwidth-fraction-wise STR over the FD-based STR, where the time-fraction-wise STR is not only the best in serving the same numbers of downlinks and uplinks but also is capable of serving many more downlinks and uplinks with a higher energy efficiency.

中文翻译：

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上下行异构宏小区信号收发优化

物联网 (IoT) 应用程序继续推动在受限通信带宽内为尽可能多的异构低延迟下行链路和上行链路提供服务的进步。已引入全双工 (FD) 收发器以在整个可用频带上实现同步信号传输和接收 (STR)。然而，即使对于微小区，链路间干扰和 FD 环路干扰也很难抑制到基于 FD STR 的有效性所需的水平。本文提出了一种用于宏小区每个时隙的替代 STR 技术，其中时隙的一部分用于下行链路，时隙的剩余部分用于上行链路。因此，可以在没有环路干扰的情况下实现整个可用带宽上的 STR。此外，还提出了另一种方法，即在整个时隙上将一部分可用带宽用于下行链路，并将剩余的补充部分带宽用于上行链路。针对所有三种可能的 STR，研究了下行链路和上行链路波束成形的问题，以最大限度地提高此类异构网络的能量效率，这些网络受下行链路和上行链路吞吐量方面的服务质量影响。数值结果证明了时间分段 STR 和带宽分段 STR 优于基于 FD 的 STR，其中时间分段 STR 不仅在服务相同数量的下行链路和上行链路方面是最好的，而且还能够以更高的能量效率为更多的下行链路和上行链路提供服务。