| 5G is a paradigm shift from the traditional LTE that includes very high carrier with massive bandwidths,extreme base station and devices densities,and unprecedented numbers of antennas.Unlike the previous 2G,3G and 4G,5G is also highly integrative: tying any new 5G air interface and spectrum together with LTE and WIFI to provide universal high-rate coverage and seamless user experience.To support this,the core network have to reach unprecedented levels of flexibility and intelligence,spectrum reconstruction and highly utility is required,and the energy efficiency should be largely improved.FD technique and energy harvesting technique can respectively improve the spectrum efficiency and the energy efficiency for the whole system.Full-duplex communication is a promise of nearly doubled channel capacity compared to conventional half-duplex communication,thus offering the potential to complement and sustain the evolution of the 5G technologies towards denser heterogeneous networks with flexible relaying modes.On the other hand,compared with replacement of the batteries for wireless devices to prolong the lifetime of wireless networks,energy harvesting can significantly improve the energy efficiency and achieve the self-sustainable through harvests energy form the natural source even ambient RF signal.For exploiting the high spectrum efficiency of FD system and the diversity gains of multi-relay systems,this paper firstly considers a two-hop full-duplex multi-relay system.Each relay adopts decode-and-forward protocols for exploiting the high spectrum efficiency of FD system while reduce their vulnerability to self-interference.The single best relay is selected from those relays that have successfully decode the source message,which then forward the source message to the destination.Meanwhile,a new signal is broadcast by the source,all the relays,include the selected best one,attempt to decode this new message.In view of the effect both inter-relay interference and self-interference,a Markov-based analytical model is utilized for analyzing the outage probability of full-duplex multi-relay network.A close-to-full diversity order is analytically proved to be attainable for full-duplex multi-relay network by the simulation results.Besides,for realizing network energy self-sustaining,this paper studies the application of energy harvesting and wireless power transfer in multi-relay cooperative communication system.In the proposed wireless powered multi-relay network model,multiple intermediate relay terminals,which are off-grid and randomly spread within a certain cooperating area,attempt to decode and forward the source information to the destination by using energy scavenged from the source radio-frequency signals.A power splitting architecture is adopted at each relay,where the received signal observation from the source is adaptively divided into two portion for information decoding and energy collection.Then a single best relay(or relays),according the proposed relay selection scenarios,is selected to forward the decoded signal to the destination.In view of the spatial randomness and energy causality at the intermediate relays,stochastic geometry is applied to characterize the end-to-end outage probability of the cooperative multi-relay system,based on which,the asymptotic outage performance in the high signal-to-noise ratio regime is analyzed.Simulation results demonstrate that with only nominally more knowledge,e.g.,locations and charge status of relays,available for relay selection,the communication quality of the system can be substantially improved compared with an arbitrary random relay selection.This paper applies full-duplex technique and energy harvesting technique into traditional communication system and analyzes many metrics such outage probability and diversity gain,which propose important theoretical basis and effective design scheme for improving the spectrum efficiency,energy efficiency and communication quality of traditional communication networks. |
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