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Wi-Fi Direct

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The Galaxy Nexus, an Android 4.1 phone with native Wi-Fi Direct[1]

Wi-Fi Direct, initially called Wi-Fi P2P, is a standard that enables Wi-Fi devices to easily connect with each other and quickly communicate without requiring a wireless access point.[2] Wi-Fi Direct enabled devices transfer data directly between each other with greatly reduced setup. And only one of the Wi-Fi devices needs to be compliant with Wi-Fi Direct to establish the peer-to-peer connection. 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 setup to require the proximity of a Near Field Communication, a Bluetooth signal, or a button press on one or all the devices. And, some have suggested Wi-Fi Direct will replace the need of Bluetooth for applications that don't rely on low energy.[3]

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.[citation needed]

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 (that is, in "ad-hoc mode"), but they go through the access point. Wi-Fi Direct devices are able to communicate with each other without requiring a wireless access point. The Wi-Fi Direct devices negotiate when they first connect to determine which device acts 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.[4] 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 (UPnP), Devices Profile for Web Services (DPWS), and Zero Configuration Networking (ZeroConf). 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 has become increasingly 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.[5] 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 has 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.[6][7]

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.

Another use for Wi-Fi Direct is to 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,[8] wireless display products such as Intel WiDi and Miracast as well as Wi-Fi Direct remote controls that are shipping circa November 2012.

Wifi Direct is becoming increasingly common in file sharing applications on Android devices, with most Android Version 4.1 (Ice Cream Sandwich) supported. Android version 4.2 (Jellybean) includes further refinements to Wifi Direct including persistent permissions enabling two-way transfer of data between multiple devices.

Technical description

Wi-Fi Direct essentially embeds a software access point ("Soft AP"), into any device that must support Direct.[6] 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.[6] Connection and setup is so simplified that some suggest it may replace Bluetooth in some situations.[9]

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.[6] 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 develops the standards suite underlying the Wi-Fi CERTIFIED certification program and owns the "Wi-Fi" trademark. The specification is available for purchase from the Wi-Fi Alliance.[10] A large and growing number of devices have been certified for Wi-Fi Direct. Over 1400 different devices have been certified for Wi-Fi Direct as of 31 October 2012.

Commercialization

Intel's My WiFi solution provides the Wi-Fi Direct technology on the Centrino 2 platform.[11] Wi-Fi Direct devices can connect to a notebook computer that plays the role of a Soft AP. The notebook computer can then provide Internet access to the Wi-Fi Direct-enabled devices without a Wi-Fi AP. Marvell,[12] Atheros, Broadcom, Intel, Ralink and Realtek announced their first products in October, 2010.[13] Redpine Signals' chipset was Wi-Fi Direct certified in November, 2010.[14] Google announced Wi-fi Direct support in Android 4.0 in October, 2011.[15] 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(released November 2011) was the first Android device to ship with Google's implementation of this feature and an API for developers to use for application development. Ozmo Devices offers Wi-Fi Direct chips and those chips are being used in Remote Controls,[16] Wi-Fi Direct Mouse designs [17] and many other products.

References

  1. ^ Android 4.0 Platform Highlights | Android Developers
  2. ^ Wi-Fi Direct™ | Wi-Fi Alliance
  3. ^ "Wi-Fi Direct could be death of Bluetooth".
  4. ^ "Wi-Fi Protected Setup", Wi-Fi Alliance Knowledge base
  5. ^ Glenn Fleishman, "Broadcom squeezes 11n, Bluetooth, FM into new, cheap chip", Ars Technica, 8 December 2008
  6. ^ a b c d Eric Griffith, "New 'Wi-Fi Direct' Spec Revamps Device Networks", PCMag.com, 14 October 2009
  7. ^ Olga Kharif, "Wi-Fi Is About to Get a Whole Lot Easier", BusinessWeek, 14 October 2009
  8. ^ http://www.shopping.hp.com/en_US/home-office/-/products/Accessories/Mice-and-Keyboards/LH571AA?HP-Wi-Fi-Direct-Black-Mobile-Mouse HP Wi-Fi Direct Mouse based on Ozmo chip
  9. ^ Chris Foresman, "Wi-Fi Direct protocol to ease peer-to-peer WiFi connections", Ars Technica, 14 October 2009
  10. ^ "Wi-Fi Alliance Published Specifications"
  11. ^ Welcome to the Freedom of Portable Wi-Fi, Intel My WiFi Pocket Book
  12. ^ Marvell supports WiFiDirect standard across entire line of 802.11 devices
  13. ^ Wi-Fi Direct Products Connect Without A Network
  14. ^ Redpine Signals’ Lite-Fi® – Ultra Low Power 802.11n – RS9110 Chipset Achieves Wi-Fi Direct™ Certification
  15. ^ Android 4 at developer.android.com
  16. ^ Ozmo Wi-Fi SOC selected for Roku remote control
  17. ^ Ozmo Wi-Fi Direct Mouse reference design certified
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