International Journal of Distributed Sensor Networks
T : Characteristics of routing protocols proposed for UASNs in related work.
Routing protocols
Time
synchronization
Multipath
establishment
Collision
avoidance
Routing void
detection
Routing update
Energy
eciency
QELAR []
No No MAC No
Partial update
Ye s
DBR []
No Yes MAC No
Periodical update
Ye s
AMCTD []
No Yes CSMA/CA No
Periodical update
Ye s
DBMR []
No Ye s M AC Ye s
Periodical update
Ye s
MRP []
No Ye s M AC Ye s
Partial update
Ye s
H-DAB []
No Yes MAC No
Periodical update
Ye s
GEDAR []
No Yes CSMA Yes
Full update
Ye s
PBDTP []
No Yes CSMA No
Full update
Ye s
PASR []
No No CSMA Yes
Partial update
Ye s
TSBNC []
Ye s No T D M A Yes
Periodical update
Ye s
E-PULRP []
No Yes CDMA No
Full update
Ye s
PER []
No Yes MAC No
Full update
Ye s
L-ABF []
No Yes MAC No
Full update
Ye s
LB-AGR []
No No MAC Yes
Partial update
Ye s
EEDBR []
No Ye s M AC Ye s
Full update
Ye s
protocol is designed by choosing appropriate historical infor-
mation and forwarding criteria based on the guidance from
ACPG.
2.2. Hybrid-Based Routing Protocol. In the design of routing
protocol, energy optimization is also a major concern. In [],
Hu and Fei used an adaptive, energy-ecient, and lifetime-
aware routing protocol based on reinforcement learning
routing protocol (QELAR). In QELAR, the residual energy of
each node, as well as the energy distribution among a group
of nodes, is factored in throughout the routing process to
calculate the reward function. e reward function aids in
selecting the adequate forwarders for packets. Each node in
the network is responsible for learning the environment, aim-
ing to take the optimal action and improving the performance
of the whole network gradually.
In [], Wu et al. proposed a time-slot-based routing
algorithm (TSR). A probability balanced mechanism named
TSBR is applied to TSR to eliminate redundancy and reduce
bit error ratio. e theory of network coding is also intro-
duced to TSBR to meet the requirements of further reducing
node energy consumption and extending the network life-
time.
In [], Gopi et al. proposed an energy optimized path
unaware layered routing protocol (E-PULRP). E-PULRP
consists of two phases: layering phase and communication
phase. In the layering phase, a set of concentric shells (layers)
areformedaroundthecentralsinknode.elayering
structure ensures that the packet is forwarded towards the
sink node. In the communication phase, one relay node is
identied from each layer to forward the packet.
In [], Huang et al. proposed a power-ecient routing
(PER) protocol. Based on the fuzzy logic inference system,
a forwarding node selector is employed to determine the
appropriate sensors to forward the packets to the destination.
Also, a forwarding tree trimming mechanism is adopted to
prevent excess spread of forwarded packets.
In [], Ali et al. proposed a layer-by-layer angle based
ooding (L-ABF) routing protocol. L-ABF addresses the
problemofnodesscatterinUASNs.InL-ABF,withoutusing
any explicit conguration and location information, each
node can calculate its ooding angle and then forward data
packets to the next upper layer toward surface sinks. e
number of nodes which ood the data packets is controlled
by the angle for ooding cone to prevent ooding over the
wholenetwork.eoodingconeisadjustedinlayer-by-
layer manner by using the angle based technique among the
upper layer nodes.
In [], Du et al. proposed a level based adaptive
geographic routing (LB-AGR) protocol. Based on available
energy, density, location, and level-dierence between neigh-
bor nodes, LB-AGR denes an integrated forwarding factor
for each candidate node. e integrated forwarding factor is
used to determine the best next-hop among multiple qualied
candidates.
In [], Wahid and Kim proposed an energy-ecient
depth-based routing (EEDBR) protocol. EEDBR utilizes the
depth and the residual energy of sensor nodes as a routing
metric. A sender-based approach is employed for routing
where the sender decides a set of next forwarding nodes
in order to reduce redundant transmissions from multiple
forwarders.
We conclude the characteristics of routing protocols men-
tioned above in Table .
3. Typical Routing Protocols for UASNs
Since routing protocols might dier depending on the appli-
cation and network architecture, it is unfair and misleading
to compare them without considering their assumptions and