X-Haul Solutions for Different Functional Split Options Using THz and Sub-THz Bands

In a variety of scenarios, from temporal events to emergencies, mobile cell also known as cell on wheels (COW) or cell on light truck (COLT) is considered as a widespread solution for temporarily increasing the capacity of the cellular networks. Flying cells are small-sized, low-cost, fast deployment options of mobile cells. In the fifth generation (5G) of cellular systems, the functionalities of radio access network (RAN) components i.e., centralized unit (CU), distributed unit (DU), and radio unit (RU) vary in different functional splits and thus have different data rate requirements for the interfaces between the units. The initial target of the paper is to provide a basic overview of different functional splits introduced in 5G, and highlight the throughput requirements of the transport X-Haul links of those functional splits. Moreover, the target is to investigate the option of utilizing terahertz (THz) and sub-THz wireless radio link to meet a high data rate requirement. In this work, we considered two frequency bands i.e., 105 GHz and 220 GHz, and estimated the handling capacity of the X-Haul link for different supporting bandwidths and distances. The X-Haul link capacity requirements also depend upon the air interface configuration, therefore, in this work different bandwidths, the number of antennas, and MIMO layer configurations are considered. The analysis is applicable for the terrestrial as well as for the flying platforms. Interestingly, it is found that with a lower functional split i.e., split 8, the X-Haul data requirement is above 150 Gbps for a simple 5G system with only 100 MHz bandwidth and 32 antennas.