Integrated Data and Energy Communication Network: A Comprehensive Survey
IEEE Communications Surveys and Tutorials
In order to satisfy the power thirsty of communication devices in the imminent 5G era, wireless charging techniques have attracted much attention both from the academic and industrial communities. Although the inductive coupling and magnetic resonance based charging techniques are indeed capable of supplying energy in a wireless manner, they tend to restrict the freedom of movement. By contrast, RF signals are capable of supplying energy over distances, which are gradually inclining closer to
... r ultimate goal -charging anytime and anywhere. Furthermore, transmitters capable of emitting RF signals have been widely deployed, such as TV towers, cellular base stations and Wi-Fi access points. This communication infrastructure may indeed be employed also for wireless energy transfer (WET). Therefore, no extra investment in dedicated WET infrastructure is required. However, allowing RF signal based WET may impair the wireless information transfer (WIT) operating in the same spectrum. Hence, it is crucial to coordinate and balance WET and WIT for simultaneous wireless information and power transfer (SWIPT), which evolves to Integrated Data and Energy communication Networks (IDENs). To this end, a ubiquitous IDEN architecture is introduced by summarising its natural heterogeneity and by synthesising a diverse range of integrated WET and WIT scenarios. Then the inherent relationship between WET and WIT is revealed from an information theoretical perspective, which is followed by the critical appraisal of the hardware enabling techniques extracting energy from RF signals. Furthermore, the transceiver design, resource allocation and user scheduling as well as networking aspects are elaborated on. In a nutshell, this treatise can be used as a handbook for researchers and engineers, who are interested in enriching their knowledge base of IDENs and in putting this vision into practice. Index Terms-RF signals, wireless energy transfer (WET), wireless information transfer (WIT), simultaneous wireless information and power transfer (SWIPT), wireless powered communication networks (WPCNs), integrated data and energy communication networks (IDENs). an increasing research interest from both the electronic and communication engineering communities. C. Near-field Wireless Energy Transfer At the time of writing, resonant inductive coupling  and magnetic resonance coupling  emerge as flexible wireless charging options for electronic devices in the nearfield. Resonant inductive coupling based wireless charging relies on the magnetic coupling that delivers electrical energy between two coils tuned to resonate at the same frequency. This technique has already been commercialised for small electronic appliances  , such as mobile phones, electric toothbrushes and smart watches etc. However, the coupling coils only support near-field wireless power transfer over a distance spanning from a few millimetres to a few centimetres  , while achieving a power transfer efficiency as high as 56.7%, when operating at a frequency of 508 kHz  . Furthermore, resonant inductive coupling requires strict alignment of the coupling coils. Even a small misalignment may result in dramatic reduction of the power transfer efficiency  . As a result, during the charging process, the electronic appliances cannot be freely moved. By contrast, magnetic resonance coupling  generates and transfers electrical energy between two resonators by exploiting evanescent-wave coupling. This technique has already been widely adopted for charging the electric vehicles due to its high power transfer efficiency  . For example, magnetic resonance coupling is capable of achieving a power transfer efficiency as high as 90% over a distance of 0.75 m  . Both its power transfer efficiency and its charging distance are much higher than that of the resonant inductive coupling. However, magnetic resonance coupling still belongs to the category of near-field wireless charging, since its power transfer efficiency dramatically reduces to 30%, when the distance is increased to 2.25 m  . Nonetheless, magnetic resonance coupling does not require strict alignment between the rechargeable device and the energy source. Hence, during the charging process, the electronic appliances may be moved within the charging area  . Furthermore, a multiple-input-multiple-output (MIMO) system, which has already been widely adopted for improving the performance of the wireless communication, can also be introduced into the field of magnetic resonance coupling in order to further enhance the power transfer efficiency   .