Differentiate between ad-hoc mode and Wi-Fi Direct mode in 802.11 architecture

Let us understand what a Wi-Fi Direct mode is.

Wi-Fi Direct Mode

The Wi-Fi Direct is built upon the same Wi-Fi technology used by most modern consumer electronic devices to communicate with wireless routers. It allows two devices to communicate with each other, provided that at least one of them is compliant with the standard to establish a peer-to-peer connection. Wi-Fi Direct is supported by more devices than most people realize.

This mode is shown below −

Here,

1 is the Printer
2 is the Computer with a wireless interface
3 is the Mobile or Another wireless device.

Ad-Hoc mode

Collections of computers are associated so that they can directly send frames to each other. There is no Access Point in Ad hoc, because Internet access is the killer application for wireless. Ad hoc networks are not very popular.

This mode is shown below −

Differences

The major differences between Wi-Fi direct and Ad hoc mode are as follows −

Parameters	Wi-Fi Direct mode	Ad-hoc mode
What is it?	In Wi-Fi direct mode, the communication occurs between the wireless nodes and access points, but not directly between wireless nodes	In ad-hoc mode, no access point is required because every node communicates directly with other nodes.
What about External Communication?	Access points acts as, a bridge to another wireless/wired network	If nodes are within the same range they can communicate.
Are Physical needs required? Complexity of modes	Physical infrastructure is needed in Wi-Fi direct mode Designing is simple because most of the network functionality lies within AP and the client is just a simple machine.	No physical infrastructure is needed in ad hoc mode. As no central coordination exists, we can use decentralized MAC protocols such as CSMA/CA, with all nodes having the same functionality. This shoots up the complexity and cost.
When it cannot be used? Applications Channel Access Topology of modes	It can’t be used in critical situations like disaster relief where no infrastructure is left. IEEE 802.11 & HIPERLAN2 are based on Wi-Fi direct mode. Most infrastructure-based WLAN uses TDMA-based protocols Based on topology the Wi-Fi, one main advantage is the ability of infrastructure WLANs to provide wired network applications and services	It is not always fully connected as two mobile nodes may temporarily be out of range. Bluetooth is a typical ad-hoc network. Most Ad-hoc based WLAN uses contention MAC protocols (e.g. CSMA) Ad-hoc WLANs are easier to set-up and they require no infrastructure