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|Towards Energy Harvesting and Interference Mitigation for D2D Communication in 5G
|Energy harvesting;D2D;Channel allocation;5G
|The exponential growth in the usage of various data-intensive applications such as ultra high definition video transmission, live streaming, augmented reality, virtual reality, real-time video calling, live conferences, and social network services, generate a huge amount of data traffic. This massive increment in data traffic degrades the spectral efficiency. To fulfil the high-end data rate requirements of the aforementioned applications, up-gradation in the existing cellular infrastructure is much needed to meet out the requirements of fifth-generation (5G) networks. Some of the salient features of the 5G networks are high spectral efficiency, massive connec- tivity, and ultra-reliable low latency. To enhance the spectral efficiency, the researchers from both academia and industry emphasize the usage of device-to-device (D2D) communication. D2D is supporting to the 5G networks in which nearby user equipment can communicate directly or cooperatively to each other with or without depending upon the base station (BS). It offloads the data traffic to counterbalance the load on the BS using either overlay or underlay paradigm. In overlay scenario, a dedicated spectrum resource is assigned to the D2D users and the rest is used by the cellular mobile users (CMUs). On the other hand, in the underlay sce- nario, D2D users reuse the spectrum resources assigned to the CMUs which increases network spectral efficiency. Despite these advantages, mutual interference between the D2D mobile users (DMUs) and CMUs has been a challenging issue in the underlaying networks. Apart from the interference, data management due to massive connectivity is another is- sue in the 5G networks. The existing underlay D2D cellular infrastructure hugely depends on the orthogonal multiple access (OMA) for spectral reuse. In OMA, one resource block (RB) can serve to one user only, it degrades the spectral efficiency. Also, the OMA supported D2D communication is expensive as connections are limited. To mitigate these issues, power do- main non-orthogonal multiple access (PD-NOMA) is used. In PD-NOMA, multiple users are served using different power levels opportunistically as per the channel conditions and quality- of-service (QoS) from a common orthogonal channel. The PD-NOMA based spectrum sharing has considered a better solution for D2D communication in 5G to improve spectrum efficiency, and network connectivity. Energy is another major issue in D2D communication due to the limited energy storage ca- pability of a battery. To prolong the lifetime of a battery, the wireless powered communication network (WPCN) is used. The WPCN is a harvest-then-transmit protocol and is a combination of the downlink wireless energy transfer (WET) and the uplink wireless information transfer ii Ishan Budhiraja, 901703009 (WIT). In WET, devices harvest energy from ambient radio frequency (RF) signals to empower their battery, and in WIT, the devices transmit information to the desired user using harvested energy. In this research work, the following schemes have been proposed to rectify the aforemen- tioned issues: • Firstly, a “Cross-Layer Interference Management Scheme for D2D Mobile Users Using NOMA" is proposed. In this scheme, the sum rate of the overall network is maximized with respect to the constraints of RB and power allocation. To achieve this goal, the D2D mobile groups (DMGs) are designed between the D2D transmitter (DDT) and DMUs to reduce the intra-user interference using successive interference cancellation (SIC) tech- nique. Secondly, the resource allocation scheme for both the CMUs and DMGs is de- signed to mitigate the cross-interference using many-to-many mapping scheme. Also, to fully exploit the potential benefits of DMGs and to enhance the spectral efficiency of the DMGs, the group rate selection criterion based RB reuse algorithm among DMGs is proposed. Lastly, for power optimization, the difference of two convex programming approach based on a successive convex approximation with low complexity is used to reduce the co-channel interference. • The second scheme is “Energy-Delay Tradeoff Scheme for NOMA-Based D2D Groups With Wireless Powered Communication Networks". In this, firstly, the DDTs and CMUs harvest energy from the RF signals of the BS. Then, the CMUs and DDTs transmit the information to the BS and DMUs from the harvested energy using the time division multiple access (TDMA) and PD-NOMA, respectively. Considering both stochastic traf- fic arrivals and time-varying channel conditions, the stochastic optimization problem is formulated, here, the aim is to maximize the energy efficiency and minimize the delay. The many-to-one matching based subchannel allocation, weighted sum method and Lya- punov optimization scheme are used to estimate the optimal outcome. Further, to obtain the closed-form expression of power and to optimize the time for WPCN, the Lagrangian function has been used. To simulate the above two schemes Matlab 2017b and convex optimization (CVX) tools are used, and the parameters used in the simulation are taken from 3GPP urban path loss model (Release- 15 and RAN1).
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