Joint Transmission Design for Multi-hop Collaborative UE Aggregation with NOMA

With the development of Internet of Things (IoT) technology, the number of IoT devices connecting to the network has grown exponentially, posing significant challenges to existing networks. Future network architectures will need to accommodate a larger scale and higher requirements of device access. For uplink systems with a large number of IoT devices, limited spectrum resources restrict access to IoT devices. In this paper, we build on the foundation of UE Aggregation, introducing non-orthogonal multiple access (NOMA) technology and pairing the cooperative points(CNs) and IoT devices into a joint transmission pair (JTP) to enhance the access rate for users at the cell edge. With the assistance of CNs, this approach aids users in combating interference, thereby improving the overall spectral efficiency of the system. Therefore, we model the problem as maximizing the system’s spectral efficiency. For this purpose, we introduce an algorithm for user pairing, and we employ a greedy strategy based on the maximum weighted independent set (MWIS) of a graph to allocate subchannels to different user groups. Finally, the simulation results demonstrate that the JTP-based UE aggregation and joint transmission design can effectively enhance the sum rate for edge users accessing the network via the CN, indicating improved system spectral efficiency under limited subchannel resources. Under a fixed number of subchannels, the JTP-based UE aggregation strategy achieves nearly a $70 \%$ increase in data rate compared to OMA, and brings up to a $36 \%$ improvement over traditional NOMA schemes.