  Sink mobility is seen as a successful strategy to resolve the hotspot problem
in Wireless Sensor Network (WSN). Mobile sinks roam in the network and collect
data from special nodes such as Cluster Heads (CH) by means of short-range
communications which improves the energy efficiency. Numerous mobile sink based
routing protocols have been proposed, however, they incur high delays
especially in large scale networks where the mobile sink has to travel for a
long distance to collect data from CHs and consequently they failed to ensure a
tradeoff between energy efficiency and delay. To resolve this issue, we propose
in this paper an Effective Hybrid Routing Protocol termed as EHRP. The main aim
of this protocol is to combine between single-hop and multi-hop routing.
Indeed, when the mobile sink arrives at a cluster it collects its data while
the other distant CHs continue to send their data using our proposed improved
Ant Colony Optimization (ACO) algorithm to avoid the waiting-time. The existing
ACO algorithms use in the distance heuristic which is not practical in real
world and fail to consider relevant statistic information of energy (e.g.,
minimum energy, average energy) in path selection which leads to unbalanced
energy consumption in the network. To address these issues, the proposed
routing algorithm employs the Received Signal Strength Indicator (RSSI) and
statistic information of energy to consume energy efficiently and decrease the
probability of sending failure. The performance of the proposed routing
protocol is tested and compared with those of the relevant routing protocols.
The simulation results show that, in comparison with its counterparts, EHRP
succeeds to minimize energy consumption and delay as well as enhancing the
packet delivery ratio.
