Abstract
In future multi-tier cellular networks, cognitive radio (CR) compatible with device-to-device (D2D) communication can be an aid to enhance system spectral efficiency (SE) and energy efficiency (EE). Users in proximity can establish a direct connection with D2D communication and bypass the base stations (BSs), thereby offloading the network infrastructure and providing EE improvement. We use stochastic geometry to model and analyze cognitive D2D communication underlying a multi-tier/multi-channel cellular network where the D2D transmitters are capable of harvesting RF energy from ambient interference resulting from simultaneous cellular downlink transmissions. For further improvement in EE, small cells (SCs) can be put into a power-saving mode by specifying a load-dependent transmission power coefficient (TPC) for SC BSs. In addition, to consider practical D2D communication scenarios, we propose a wireless video sharing framework where cache-enabled users can store and exchange popular video files through D2D communication. We investigate the potential effects of the TPC and the introduced D2D layer on the network EE and SE. We will also observe that the energy-harvesting CR-based D2D communication network design will not only ease the spectrum shortage problem but will also result in a greener network thanks to its reliance on ambient energies.
Highlights
Traditional designs in cellular networks have concentrated on spectral efficiency (SE) or on achieving some quality of service (QoS) criteria rather than enhancing energy efficiency (EE) [1,2]
With the evolution to Long-Term Evolution (LTE) and 5G, the cellular network has developed as a multi-tier network that comprises a conventional cellular network with multiple low-power base stations (BSs) (i.e., small cells (SCs))
It is important to note that for the underlay in-band D2D scenario, we mainly focus on the fourth case, i.e., when the cellular network, inside the D2D protection region, is absent on cd and the typical D2D transmitter correctly detects the absence of cellular transmissions and uses cd for D2D transmission
Summary
Traditional designs in cellular networks have concentrated on spectral efficiency (SE) or on achieving some quality of service (QoS) criteria rather than enhancing energy efficiency (EE) [1,2]. With the rise in the use of wireless data applications, EE has become one of the key design considerations for next-generation 5G/6G systems to accommodate the ever-increasing demand for traffic with the desired QoS, to mitigate operational costs, and to limit greenhouse gas (GHG) emissions from wireless cellular networks [2]. By integrating CR techniques, the D2D devices can borrow idle radio spectrums from primary networks without interrupting communications between the licensed users. In such a way, the capacity of D2D communications in cellular networks can be largely increased by improved spectrum efficiency (SE)
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