“…Likewise, single-hop is also used in several protocols for inter-cluster communication. However, some clustering protocols add multi-hop routing between CHs and BS, including LEACH-DT [41], ECPF [44], EBUC [62], TPSO-CR [40], ETPSO-CR [16], LPOBC [66], TTCH-WSN [67], MMDCP [68], MOFCA [51], TTDFP [52], EAUCA [54], HDDS [55], UCMR-FL [56]. Since the transmission energy is proportional to the transmission distance, the use of multi-hop routing between the CHs and the BS can improve the energy efficiency of the WSN.…”