  Mobile Crowdsourcing (MC) is an effective way of engaging large groups of
smart devices to perform tasks remotely while exploiting their built-in
features. It has drawn great attention in the areas of smart cities and urban
computing communities to provide decentralized, fast, and flexible ubiquitous
technological services. The vast majority of previous studies focused on
non-cooperative MC schemes in Internet of Things (IoT) systems. Advanced
collaboration strategies are expected to leverage the capability of MC services
and enable the execution of more complicated crowdsourcing tasks. In this
context, Collaborative Mobile Crowdsourcing (CMC) enables task requesters to
hire groups of IoT devices' users that must communicate with each other and
coordinate their operational activities in order to accomplish complex tasks.
In this paper, we present and discuss the novel CMC paradigm in IoT. Then, we
provide a detailed taxonomy to classify the different components forming CMC
systems. Afterwards, we investigate the challenges in designing CMC tasks and
discuss different team formation strategies involving the crowdsourcing
platform and selected team leaders. We also analyze and compare the
performances of certain proposed CMC recruitment algorithms. Finally, we shed
the light on open research directions to leverage CMC service design.
