Design Of Transmission Strategy For Buffer-aided Relay System Based On Differential Chaotic Shift Keying

Cooperative communication technology has been extensively studied in recent years because of its reliability of data transmission.The proposal of the buffer-aided relay system breaks the limitation of the bottleneck link in traditional cooperative communication.Adaptive link selection for buffer-aided relaying can achieve significant performance gain compared with the conventional relaying with fixed transmission criterion.However,most of the existing link-selection strategies are designed based on perfect channel state information(CSI),and channel estimation is very complicated and difficult to implement.Moreover,in some complex circumstances,it is unrealistic to replace or charge the battery.In order to solve the above issues,the differential chaos shift keying(DCSK)technology and simultaneous wireless information and power transfer(SWIPT)technology are combined to use in the buffer-aided relay system and optimize transmission strategies of the system.In this paper,we first investigate a buffer-aided differential chaos-shift-keying based simultaneous wireless information and power transfer(DCSK-SWIPT)relay system,where a decode-and-forward(DF)protocol is considered and the relay is equipped with a data buffer and an energy buffer.In particular,we propose two link-selection protocols for the proposed system based on harvested energy,data-buffer status and energy-shortage status,where the CSI is replaced by the harvested energy to avoid the channel estimation and the practical problem of the decoding cost at the relay is considered.Furthermore,the bit-error-rate(BER)and average-delay closed-form expressions of the proposed protocols are derived over multipath Rayleigh fading channels,which are validated via simulations.Finally,results demonstrate that both the proposed protocols not only provide better BER performance than the conventional DCSK system and DCSK-SWIPT relay system but also achieve better BER performance and lower average delay in comparison with the conventional signal-to-noise-ratio-based buffer-aided DCSK-SWIPT relay systems.In order to match the actual scenarios,this paper models the energy buffer based on the first work,and proposes an energy and data buffer-aided DCSK relay system.Simultaneously,based on the harvested energy,the state of energy buffer and data buffer,two link-selected policies are proposed.Similarly,the proposed strategies do not require channel estimation,and link-selection can be performed just by judging the harvested energy.Simulation results demonstrate that the proposed strategies can achieve better BER performance compared with the strategies proposed in the first work.