lay, respectively, with M+12=1.x1 and X2 are normalized intended Relay ((g)) MBS 1 Obstacles BS transmission UE UE Relay transmission MBS N Figure 4.6 System model. 4.2 NOMA in a mmWave-Based loT Wireless System with SWIPT signal for UE 1 and UE 2. PBS is the transmission power of the BS. At the receiver side, UE 1 observes which is expressed as (4.30) where NB1 is the additive Gaussian white noise (AWGN) with variance o2, d is the distance from the BS to UE 1, a is the path loss exponent for line-of-sight (LOS). Without loss of generality, we assume > |hBRI2. Hence according to NOMA proto- col, M1 2 22 is set to ensure QoS at the weak receiver. With this setting, UE 1 first decodes signal X2 with its SINR formulated as (4.31) where transmission SNR from the BS to UE 1. The superscript "1" indicates the first phase. SIC is performed to remove X2 from the superimposed signal, then UE 1 can decode its own message with the following SINR (4.32) At the relay side, it first splits the observation into two parts. One part is for the recharge- able unit, which consists of a super capacitor or a short-term high efficiency battery. The other part is for information decoding, which can be expressed as (4.33) where B is the power split coefficient indicating the portion of power assigned to energy harvest unit. NBR has the same distribution with NB1. Signal yRR goes through the decoding unit for X2, the corresponding SINR is (4.34) where PBR is the transmission SNR from the BS the relay. The remaining power is harvested by the relay. In this chapter, we adopt the non-linear energy harvest model, which is more precise in modeling the power-in-power-out relation in current wireless charging technology. Specifically, the harvested energy can be expressed as a logistic (sigmoidal) function (4.35) where M, a, b are constants and represent different physical meanings in wireless charging. M denotes the maximum harvested power at the relay when the energy harvesting circuit 4 NOMA in Relay and loT for 5G Wireless Networks PO((W) F