A straightforward comparison of the above recent research
regarding sensor-cloud is shown in Table 2. From exploring
these recent developments about sensor-cloud, it is observed
that the research regarding sensor-cloud is still at its infancy,
although sensor-cloud for green IoT is very promising.
More interesting research regarding this area are expected to
emerge.Regarding the future sensor-cloud, we envision that
the future sensor-cloud will evolve into social-sensorcloud
(SSC), in which social networks (SNs) [61], [62], WSN
and cloud connect and complement each other, as shown
in Fig. 4. In social-cloud, integrating SNs and CC, there are
already much research (e.g., [63]–[66]), in which the key
idea is to share the cloud resources and services utilizing the
relationships established between members of a SN. In SSC,
leveraging SNs, not only will the sensor-cloud resources and
services be shared, but also the SNs could be used to achieve
better energy efficiency for sensor-cloud in the following
ways.
• Sharing the sensor-cloud resources and services to other
users with SNs, will substantially reduce the resources
and services requested by the sensor-cloud users. As a
result, the energy consumption of sensor-cloud can be
decreased dramatically.
• The massive user behavior information in SNs, could
be collected and analyzed as well as further utilized to
enhance the energy usage in sensor-cloud (e.g., optimize
the data gathering and data transmission in WSN,
improve the data storage and data processing in cloud,
etc.). In return, users’ needs will also be better satisfied.
• Based on the amount of resource consumption and service
usages created by a variety of users in SNs, the
deployment of resources could be optimized and the
waste of resources could be reduced in sensor-cloud.
In other words, the attendance of SNs could greatly help
sensor-cloud fulfill green IoT.
powerful cloud computing technologies to provide excellent
data scalability, rapid visualization, and user programmable
analysis’’ [13], [14].Attracting increasing interest from both academic and
industrial communities, sensor-cloud [13], [14], [53] is actually
a new paradigm, motivated by complementing 1) the
ubiquitous data sensing and data gathering capabilities of
WSNs as well as 2) the powerful data storage and data
processing abilities of CC. Particularly, as presented in Fig. 3,
the basic application model of sensor-cloud is to use the
ubiquitous sensors (e.g., static sensors, mobile sensors, video
sensors, etc.) offered by the SNP (sensor network provider)
to collect various sensory data (e.g., temperature, humidity,
traffic, house surveillance, etc.) about the surrounding
environment. Then the sensory data is further transmitted to
the cloud provided by the CSP (cloud service provider) for
storage and further processing. After the cloud stores and
processes the sensory data with data centers, the processed
sensory data are delivered to the CSU (cloud service user) on
demand. In this whole process, SNPs act as the data sources
for CSPs. CSUs are the data requesters for CSPs.
With sensor-cloud integration, there are many favorable
advantages [13], [14], benefiting the users and the WSN as
well as the cloud. For instance, users can have access to their
required sensory data from cloud anytime and anywhere if
there is network connection, instead of being stick to their
desks. The utility of WSN can be increased, by enabling it to
serve multiple applications. The services cloud provides can
be greatly enriched, by being able to offer the services that
WSN provides (e.g., healthcare monitoring, environmental
monitoring, forest fire detection, landslide detection, etc.).
In particular, enhancing the performance (e.g., data processing
speed, response time, visualization) of WSN with
immense storage and processing capability of cloud, analytical
results have shown that sensor-cloud could outperform a
traditional WSN, by increasing the sensor’s lifetime by 3.25%
and decreasing the energy consumption by 36.68%. All these
are very desirable for smart world and green IoT.the following two critical security issues. Issue 1: Genuine
CSPs and genuine SNPs could be impersonated by vicious
attackers to perform communications with CSUs and CSPs,
respectively. As a result, any service cannot be obtained by
CSUs and CSPs from the fake CSPs and SNPs, while the trust
and reputation of the authentic CSPs and SNPs are strongly
decreased by these fake CSPs and SNPs. Issue 2: Lacking
trust and reputation calculation and management of CSPs
and SNPs, CSU may easily choose an untrustworthy CSP
and CSP probably easily selects an untrustworthy SNP. Then
the delivery of the service (from CSP to CSU, from SNP
to CSP) owns an unacceptable large latency, or cannot be
delivered successfully quite often, or could only be offered
for a very short time period unexpectedly. To solve these