" A constant need to increase the network capacity for meeting the growing demands of subscribers has led to the evolution of cellular communication networks form the first generation (1G) to fifth generation (5G).
There will be billions of connected devices in the near future. Such a large number of connections are expected to be heterogeneous in nature, demanding higher data rates, lesser delays, enhanced system capacity and superior throughput. The available spectrum resources are limited and need to be flexibly used by the mobile network operators to cope with the rising demands. An emerging facilitator of the upcoming high data rate demanding next generation networks is device to device communication. "
How d2D is different than wLAN and Bluetooth?
A picture is worth a thousand words and similarly a comparison is worth 2000 words :). I will show the table which compares D2D, WLAN and Bluetooth.
What are the Growth prospects of D2D?
Another Table below can give you the overall information about the rising trends in D2D as shown:
What about MANETs VS D2D Communication?
In order to compare Mobile Adhoc networks (MANETs) with D2D communications. Take a look at the table below.
How Many Types of D2D Communication Exist?
The following four types of D2D Communication exist. More specifically the classification and hierarchy is shown below.
For comprehensive details, you can read at the source of this information below.
Pimmy Gandotra, Rakesh Kumar Jha, Device-to-Device Communication in Cellular Networks: A Survey, Journal of Network and Computer Applications, Volume 71, 2016, Pages 99-117, ISSN 1084-8045,