Ultragreen Relay Transmission With Wireless Power Transfer for Advanced IoT: Session-Specific Analysis and Optimization

Abstract

Reliable and energy-efficient wireless transmission is of critical importance to the success of future advanced Internet of Things (IoT). Due to the sporadic nature of IoT transmissions, the energy consumption of the individual IoT transmission session varies dramatically with the instantaneous operating environment as well as the quality of service (QoS) requirements. In this paper, we analyze and design the energyefficient relay transmission systems from an individual data transmission session perspective. Specifically, we consider a dualhop transmission system with a decode-and-forward relay that is solely powered by wireless power transfer from source node. For both time switching and power splitting modes of simultaneous power and information transmission, we analyze and minimize the total energy consumption of the system when transmitting a fixed amount of data, under a piecewise linear energy harvesting (EH) model. Closed-form expressions for optimal transmission parameters are obtained with and without the consideration of latency constraint. Through selected numerical results, we illustrate various design tradeoffs between energy consumption and latency constraint. We show that with optimal transmission parameters, relay transmission with energy transfer can achieve considerable energy saving compared to direct transmission when the direct link quality is poor and the latency constraint is not stringent. We also show that with optimized parameters, power splitting mode leads to lower energy consumption and smaller transmission duration than time switching mode, at the cost of higher implementation complexity.

Cooperative Resource Allocation for Hybrid NOMA-OMA-Based Wireless Powered MC-IoT Systems with Hybrid Relays

“…In [22], by considering that relays have finite data buffer and finite energy storage, a relay selection algorithm based on data and energy buffer status was proposed. In [23], both time switching-based relaying and power splitting-based relaying were considered, and the total system energy consumption was minimized under the latency constraint. In [24], based on the time switching-based relaying, by taking the channel aging effect into consideration, a joint relay selection, transmit beamforming, and power allocation algorithm was developed to maximize the system throughput.…”

“…Compared to the works on wireless powered IoT relay systems with NOMA [31][32][33][34][35][36][37] which only considered a relay serving a group of IoTDs, this work considers a more complex scenario with multiple hybrid relays and multiple groups of IoTDs, which requires allocation of resources and coordination among the hybrid relays and groups of IoTDs. Note, that the works [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] also did not consider the scenario of multiple hybrid relays serving different groups of IoTDs. It is noted that in previous works [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], only multiple access of the IoTDs is ...…”

“…Note, that the works [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] also did not consider the scenario of multiple hybrid relays serving different groups of IoTDs. It is noted that in previous works [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], only multiple access of the IoTDs is considered, while not only multiple access to the IoTDs but also multiple access to the hybrid relays are considered in this paper, which leads to more complex design problems than those in previous works. Note, that due to the high complexity of the successive interference cancellation (SIC) adopted by NOMA, the number of users in a NOMA group is normally restricted [30].…”