Picture Source: Cisco
The clouds are up in the sky whereas the fog is low, on the ground. This is how Fog Computing is referred to as opposed to the cloud. Fog sits at the edge (that is why edge computing) to reduce the latency and do an initial level of processing thereby reducing the amount of information that needs to be exchanged with the cloud.
The same paradigm is being used in case of 5G to refer to edge computing, which is required when we are referring to 1ms latency in certain cases.
whitepaper from Ovum & Eblink explains:
Mobile Edge Computing (MEC): Where new processing capabilities are introduced in the base station for new applications, with a new split of functions and a new interface between the baseband unit (BBU) and the remote radio unit (RRU).
Mobile Edge Computing (MEC) is an ETSI initiative, where processing and storage capabilities are placed at the base station in order to create new application and service opportunities. This new initiative is called “fog computing” where computing, storage, and network capabilities are deployed nearer to the end user.
MEC contrasts with the centralization principles discussed above for C-RAN and Cloud RAN. Nevertheless, MEC deployments may be built upon existing C-RAN or Cloud RAN infrastructure and take advantage of the backhaul/fronthaul links that have been converted from legacy to these new centralized architectures.
MEC is a long-term initiative and may be deployed during or after 5G if it gains support in the 5G standardization process. Although it is in contrast to existing centralization efforts, Ovum expects that MEC could follow after Cloud RAN is deployed in large scale in advanced markets. Some operators may also skip Cloud RAN and migrate from C-RAN to MEC directly, but MEC is also likely to require the structural enhancements that C-RAN and Cloud RAN will introduce into the mobile network.
The biggest challenge facing MEC in the current state of the market is its very high costs and questionable new service/revenue opportunities. Moreover, several operators are looking to invest in C-RAN and Cloud RAN in the near future, which may require significant investment to maintain a healthy network and traffic growth. In a way, MEC is counter to the centralization principle of Centralized/Cloud RAN and Ovum expects it will only come into play when localized applications are perceived as revenue opportunities.
And similarly this Interdigital presentation explains:
Extends cloud computing and services to the edge of the network and into devices. Similar to cloud, fog provides network, compute, storage (caching) and services to end users. The distinguishing feature of Fog reduces latency & improves QoS resulting in a superior user experience
Here is a small summary of the patents with IoT and Fog Computing that has been flied.