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1、3622IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 12, NO. 7, JULY 2013 Relaying Protocols for Wireless Energy Harvesting and Information Processing Ali A. Nasir, Student Member, IEEE, Xiangyun Zhou, Member, IEEE, Salman Durrani, Senior Member, IEEE, and Rodney A. Kennedy, Fellow, IEEE AbstractA
2、n emerging solution for prolonging the lifetime of energy constrained relay nodes in wireless networks is to avail the ambient radio-frequency (RF) signal and to simultaneously har- vest energy and process information. In this paper, an amplify- and-forward (AF) relaying network is considered, where
3、 an energy constrained relay node harvests energy from the received RF signal and uses that harvested energy to forward the source information to the destination. Based on the time switching and power splitting receiver architectures, two relaying protocols, namely, i) time switching-based relaying
4、(TSR) protocol and ii) power splitting-based relaying (PSR) protocol are proposed to enable energy harvesting and information processing at the relay. In order to determine the throughput, analytical expressions for the outage probability and the ergodic capacity are derived for delay-limited and de
5、lay-tolerant transmission modes, respec- tively. The numerical analysis provides practical insights into the effect of various system parameters, such as energy harvesting time, power splitting ratio, source transmission rate, source to relay distance, noise power, and energy harvesting effi ciency,
6、 on the performance of wireless energy harvesting and information processing using AF relay nodes. In particular, the TSR protocol outperforms the PSR protocol in terms of throughput at relatively low signal-to-noise-ratios and high transmission rates. Index TermsEnergy harvesting, wireless power tr
7、ansfer, amplify-and-forward, cooperative communications, throughput, outage probability, ergodic capacity. I. INTRODUCTION P ROLONGING the lifetime of a wireless network through energy harvesting has received signifi cant attention very recently 112. Though, replacing or recharging batteries can avo
8、id energy harvesting, it incurs a high cost and can be inconvenient or hazardous (e.g., in a toxic environments), or highly undesirable (e.g., for sensors embedded in building structures or inside the human body) 12. In such scenarios, a safe and convenient option may be to harvest the energy from t
9、he environment. Apart from the conventional energy harvest- ing methods, such as solar, wind, vibration, thermoelectric effects or other physical phenomena 13, 9, 1315, a new emerging solution is to avail ambient radio-frequency (RF) signals 4. The advantage of this solution lies in the fact that RF
10、 signals can carry energy and information at the same Manuscript received December 23, 2012; revised March 20, 2013; accepted May 9, 2013. The associate editor coordinating the review of this paper and approving it for publication was S. Mao. This research was supported under Australian Research Cou
11、ncils Discov- ery Projects funding scheme (project number DP110102548). The authors are with the Research School of Engineering, The Australian National University, Canberra, Australia (e-mail: ali.nasir, xiangyun.zhou, salman.durrani, rodney.kennedyanu.edu.au). Digital Object Identifi er 10.1109/TW
12、C.2013.062413.122042 time. Thus, energy constrained nodes can scavenge energy and process the information simultaneously 47, 10, 12. For wireless energy harvesting using RF signals, the recent state-of-the-art advances in point-to-point systems can be clas- sifi ed into two main approaches. The fi r
13、st approach considers an ideal receiver design that is able to simultaneously observe and extract power from the same received signal 4, 5, 10. However, as discussed in 6, this assumption does not hold in practice, as practical circuits for harvesting energy from RF signals are not yet able to decod
14、e the carried information directly. The second approach considers a practically realiz- able receiver design with separate information decoding and energy harvesting receiver for information and power transfer and is now widely adopted in the literature 6, 11, 12, 16, 17. For the fi rst class of rec
15、eivers, the idea of transmitting information and energy simultaneously was fi rst proposed in 4, where the authors used a capacity-energy function to study the fundamental performance tradeoff for simultaneous information and power transfer. The work in 4 was extended to frequency-selective channels
16、 with additive white Gaussian noise (AWGN) in 5. A two-way communication system for energy harvesting and information transmission was investi- gated in 10. For the second class of receivers, the perfor- mance limits of a three node multiple-input-multiple-output (MIMO) broadcasting system, with separate energy harvesting and information decoding receiver, was studied in 12. The work in 12 was extended in 16 by considering imper
