A Hybrid LDM, TDM/FDM and Hierarchical Modulation Signal Structure for In-band Distribution Link Transmission in SFN

This paper investigates the multiplexing technology to improve the wireless in-band distribution link (IDL) spectrum efficiency and reduce demultiplexing complexity. A Hybrid-Mux technology is proposed for high spectrum efficiency (compared to TDM/FDM), and low complexity and latency (compared to LDM). A 2-layer structured HM based on 2-layer LDM, and a 3-layer structured HM based on 3-layer LDM are introduced. The key signal structure of Hybrid-Mux and several typical cases of applications are presented, where the system complexity and capacity requirement can be satisfied. The throughput optimization is formulated and resolved, under the constraint of IDL capacity and size of constellation. Simulation results show that by using HM, Hybrid-Mux can achieve higher capacity than TDM and LDM only approach, while the demodulation and demultiplexing complexity of Hybrid-Mux is not much higher than the structure where IDL is TDM-ed with existing LDM signal, and is lower than the structure where IDL is TDM-ed with enhanced layer (EL) signal. The difference of LDM vs. HM in the design and implementation are discussed.