Opportunistic communications are limited by chan-
nel variability due to various factors, such as user
mobility, traffic types, and spectrum availability, and
limited communication range, may result in unpre-
dictable delays during message forwarding. There-
fore, only delay-tolerant traffic is suitable for OMSNs.
Compared with traditional communication networks,
OMSNs pose severe challenges for data forwarding.
Socievole et al.show that Bluetooth contacts network
layer and Facebook friendships network layer are sim-
ilar by experiment on a campus environment. [3] Since
social networks rely on the interaction among nodes,
the social features of mobile devices carried by hu-
mans have significant impacts on the establishment
of communications among mobile nodes. Thus, how
to design effective opportunistic routing algorithms
based on the social features of mobile nodes has be-
come an active research problem.
In recent years, Social Network Analysis (SNA)
[4] and its applications have also attracted many re-
searchers to utilize it to design novel network architec-
tures and effective routing algorithms, such as DTNs
[5], Pocket Switched Networks (PSNs) [6], Oppor-
tunistic Networks (OppNets) [7], and Social Aware
Networking (SANs) [8]. SNA plays an important role
in providing the basis for using of social features in
physical networks and enhancing the performance of
routing algorithms in OMSNs by utilizing the social
features and node mobility patterns. A typical SNA
considers several metrics to characterize the impor-
tance of nodes and their social relationships, which are
called social features. Those social features are used
to design effective and efficient routing algorithms in
OMSNs.
In typical OMSNs, there are many social features
can be utilized, including centrality, similarity, tie
strength, popularity, closeness, cumulative contact
frequency, stability, influence, social pressure mea-
surement, and so on [2]. Among all these social fea-
tures, centrality, similarity and tie strength are the most
widely used. Thus, we can use them to design rout-
ing algorithms with high delivery ratio, low latency
and low overhead. The reason why we choose these
three social features is that they are the most repre-
sentative among all social features. Centrality can de-
scribe how important a single node is in the network.
High centrality of a node means that the node is at
the center of the network. Not like Centrality, Sim-
ilarity and Tie-Strength can describe how strong the
relationship is between two nodes. The difference of
these two social features is that Tie-Strength directly
describes the node relationship, while the Similarity
indirectly describes the node relationship. These three
social features cover almost everything about society
that needs to be considered when designing routing al-
gorithms. We analyze the performance of routing al-
gorithms based on these three social features respec-
tively, and identify the pros and cons of these rout-
ing algorithms. We also observe that many routing al-
gorithms have not taken the node selfishness caused
by the limitations on energy, storage and spectrum re-
sources into consideration. Since node selfishness se-
riously affects the performance of routing algorithms,
many incentive mechanisms are proposed to mitigate
the impact of selfishness on the performance of routing
algorithms. We classify the routing algorithms with
these incentive mechanisms and describe their charac-
teristics, pros, and cons respectively.
There are already some surveys on routing algo-
rithms in OMSNs. Xia et al.[2] presents a comprehen-
sive survey for Socially Aware Networking. However,
they did not classify and analyze routing algorithms
according to specific social features. Zhu et al.[9]
presents an excellent survey on data routing strategies
in MSNs, but they have not covered the effect of self-
ishness on routing performance and the solutions for
selfishness. Our paper intends to provide a compre-
hensive survey on opportunistic routing algorithms in
OMSNs. We first review various routing algorithms
based on the aforementioned three social features and
identify the common problems in such routing algo-
rithms. To handle the node selfishness, we classify the
routing algorithms based on incentive mechanism de-
sign and elaborate their characteristics, discuss design
challenges and future research directions of routing al-
gorithms for OMSNs. Compared with current surveys,
the classification method of this paper is different, and
the selected articles are relatively new.
For analysis the routing algorithms more system-
atic, we divide the design parameters into three lev-
els. (1) Delivery Ratio. No matter the routing al-
gorithm based on social features or the routing algo-
rithm with incentive mechanism, the most important
consideration in designing the algorithm must be the
delivery ratio, because the delivery of messages is the
most basic requirement of the routing algorithm and
China Communication · February 2021 87