Abstract
The design of an energy-efficient routing protocol is crucial for extending the life-time of limited energy-constrained wireless sensor networks (WSNs). To achieve this goal, the authors propose three proactive routing protocols; the first protocol is a circle zone stable election protocol (CZSEP). This protocol is a two-level heterogeneous energy protocol with a circle zone located at the centre of the network field and used to deploy the normal nodes and with advanced nodes that are randomly distributed around the circle zone. The performance of the proposed CZSEP was compared to that of the conventional ZSEP considering the same total initial energy. To further improve the performance of CZSEP, they propose the second protocol named as, CZSEP with helper nodes (CZSEP-HN) which is a three-level heterogeneous energy protocol. In CZSEP-HN, they add helper nodes in certain places in the network field to minimise the energy consumption in the considered network. Both CZSEP and CZSEP-HN can overcome the problem of large transmission distance between normal nodes and the base station (BS) and between cluster-heads and BS exists in conventional ZSEP. Finally, they propose the third protocol, which is a modified CZSEP-HN (MCZSEP-HN) to overcome the problem of energy consumption in CZSEP-HN. MCZSEP-HN is a four-level heterogeneous energy protocol with two circle zones one for normal nodes and the other for intermediate nodes. The obtained results showed that the MCZSEP-HN outperforms the other protocols in terms of life-time, throughput, stability and instability period and can reduce the energy consumption in WSNs.