Wi-Fi Direct, initially called Wi-Fi P2P, is a Wi-Fi standard that enables devices to
connect easily with each other without requiring a wireless access point and to communicate
at typical Wi-Fi speeds for everything from file transfer to Internet connectivity.
One advantage of Wi-Fi Direct is the ability to connect devices even if they are from different
manufacturers.
Only one of the Wi-Fi devices needs to be compliant with Wi-Fi Direct to establish a
peer-to-peer connection that transfers data directly between each other with greatly reduced
setup.
Wi-Fi Direct negotiates the link with a Wi-Fi Protected Setup system that assigns each device
a limited wireless access point.
The "pairing" of Wi-Fi Direct devices can be set up to require the proximity of a near
field communication, a Bluetooth signal, or a button press on one or all the devices.
Wi-Fi Direct may not only replace the need for routers, but may also replace the need
of Bluetooth for applications that do not rely on low energy.
Background Basic Wi-Fi
Conventional Wi-Fi networks are typically based on the presence of controller devices
known as wireless access points.
These devices normally combine three primary functions; physical support for wireless and
wired networking, bridging and routing between devices on the network, and service provisioning
to add and remove devices from the network.
A typical Wi-Fi home network includes laptops, tablets and phones, devices like modern printers,
music devices and televisions.
The majority of Wi-Fi networks are set up in "infrastructure mode", where the access
point acts as a central hub to which Wi-Fi capable devices are connected.
The devices do not communicate directly with each other, but they go through the access
point.
Wi-Fi Direct devices are able to communicate with each other without requiring a dedicated
wireless access point.
The Wi-Fi Direct devices negotiate when they first connect to determine which device shall
act as an access point.
Automated setup As the number and type of devices attaching
to Wi-Fi systems increased, the basic model of a simple router with smart computers became
increasingly strained.
At the same time, the increasing sophistication of the hot spots presented setup problems
for the users.
To address these problems, there have been numerous attempts to simplify certain aspects
of the setup task.
A common example is the Wi-Fi Protected Setup system included in most access points built
since 2007 when the standard was introduced.
Wi-Fi Protected Setup allows access points to be set up simply by entering a PIN or other
identification into a connection screen, or in some cases, simply by pressing a button.
The Protected Setup system uses this information to send data to a computer, handing it the
information needed to complete the network setup and connect to the Internet.
From the user's point of view, a single click replaces the multi-step, jargon-filled setup
experience formerly required.
While the Protected Setup model works as intended, it was intended only to simplify the connection
between the access point and the devices that would make use of its services, primarily
accessing the Internet.
It provides little help within a network - finding and setting up printer access from a computer
for instance.
To address those roles, a number of different protocols have developed, including Universal
Plug and Play, Devices Profile for Web Services, and Zero Configuration Networking.
These protocols allow devices to seek out other devices within the network, query their
capabilities, and provide some level of automatic setup.
New uses It became common for smart phones and portable
media players to include Wi-Fi as a standard feature, and over time it has become common
in feature phones as well.
The process of adding Wi-Fi to smaller devices has accelerated, and it is now possible to
find printers, cameras, scanners and many other common devices with Wi-Fi in addition
to other connections, like USB.
The widespread adoption of Wi-Fi in new classes of smaller devices made the need for ad hoc
networking much more important.
Even without a central Wi-Fi hub or router, it would be useful for a laptop computer to
be able to wirelessly connect to a local printer.
Although the ad hoc mode was created to address this sort of need, the lack of additional
information for discovery makes it difficult to use in practice.
Although systems like UPnP and Bonjour provide many of the needed capabilities and are included
in some devices, a single widely supported standard was lacking, and support within existing
devices was far from universal.
A guest using their smart phone would likely be able to find a hot spot and connect to
the Internet with ease, perhaps using Protected Setup to do so.
But the same device would find streaming music to a computer or printing a file might be
difficult, or simply not supported between differing brands of hardware.
Wi-Fi Direct can provide a wireless connection to peripherals.
Wireless mice, keyboards, remote controls, headsets, speakers, displays and many other
functions can be implemented with Wi-Fi Direct.
This has begun with Wi-Fi mouse products, wireless display products such as WiDi and
Miracast as well as Wi-Fi Direct remote controls that were shipping circa November 2012.
File sharing applications on Android and BlackBerry 10 devices could use Wi-Fi Direct, with most
Android Version 4.1 and BlackBerry 10.2 supported.
Android version 4.2 included further refinements to Wi-Fi Direct including persistent permissions
enabling two-way transfer of data between multiple devices.
Technical description Wi-Fi Direct essentially embeds a software
access point, into any device that must support Direct.
The soft AP provides a version of Wi-Fi Protected Setup with its push-button or PIN-based setup.
When a device enters the range of the Wi-Fi Direct host, it can connect to it, and then
gather setup information using a Protected Setup-style transfer.
Connection and setup is so simplified that some suggest it may replace Bluetooth in some
situations.
Soft APs can be as simple or as complex as the role requires.
A digital picture frame might provide only the most basic services needed to allow digital
cameras to connect and upload images.
A smart phone that allows data tethering might run a more complex soft AP that adds the ability
to bridge to the Internet.
The standard also includes WPA2 security and features to control access within corporate
networks.
Wi-Fi Direct-certified devices can connect one-to-one or one-to-many and not all connected
products need to be Wi-Fi Direct-certified.
One Wi-Fi Direct enabled device can connect to legacy Wi-Fi certified devices.
The Wi-Fi Direct certification program is developed and administered by the Wi-Fi Alliance,
the industry group that owns the "Wi-Fi" trademark.
The specification is available for purchase from the Wi-Fi Alliance.
Commercialization Laptops
Intel included Wi-Fi Direct on the Centrino 2 platform, in its My WiFi technology by 2008.
Wi-Fi Direct devices can connect to a notebook computer that plays the role of a software
Access Point.
The notebook computer can then provide Internet access to the Wi-Fi Direct-enabled devices
without a Wi-Fi AP.
Marvell Technology Group, Atheros, Broadcom, Intel, Ralink and Realtek announced their
first products in October 2010.
Redpine Signals' chipset was Wi-Fi Direct certified in November of the same year.
Mobile Devices Google announced Wi-Fi Direct support in Android
4.0 in October of the following year.
While some Android 2.3 devices like Samsung Galaxy S II have had this feature through
proprietary operating system extensions developed by OEMs, the Galaxy Nexus was the first Android
device to ship with Google's implementation of this feature and an application programming
interface for developers.
Ozmo Devices, which developed integrated circuits designed for Wi-Fi Direct, was acquired by
Atmel in 2012.
With the Blackberry 10.2.1 upgrade, Wi-Fi Direct is now available.
iOS 8 will be gaining support for Wi-Fi Direct for its AirDrop, Handoff, Instant Hotspot
and AirPlay features.
Game Consoles The Xbox One, released in 2013, supports Wi-Fi
Direct.
NVIDIA's SHIELD controller uses Wi-Fi Direct to connect to compatible devices.
NVIDIA claims a reduction in latency and increase in throughput over competing Bluetooth controllers.
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