Usuario:Amitie 10g/Vitrina/Wi-Fi Direct
Conventional Wi-Fi networks are typically based on the presence of controller devices known as wireless access points, "base stations" or "hot spots". 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 a wired connection to a broadband provider, the access point, computers connected by wired and wireless connections, and sometimes other devices on the network. 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, but they go through the access point. All Wi-Fi Direct devices are able to operate as either a device or an access point. The Wi-Fi Direct devices negotiate when they first connect to determine which device acts as an access point.
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, multi-device, 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 Apple's Bonjour. These protocols allow devices to seek out other devices within the network, query their capabilities, and provide some level of automatic setup.
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. 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 working ad hoc networking much more important. Even without a central Wi-Fi hub/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 essentially embeds a software access point, or "soft AP", into any device that wishes to 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 using the existing ad-hoc protocol, 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 AP's 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 develops the standards suite underlying the Wi-Fi CERTIFIED certification program and owns the "Wi-Fi" trademark. The final specification has not been released, and certain aspects of the system have not been mentioned to date. For instance, the system used for discovery and device classification, an analogue of UPnP or Bonjour, has not been mentioned in existing references.
The first Wi-Fi Direct certified printer was the Samsung SCX-3400 series. (Oct 2011)
Intel's My WiFi solution provides the Wi-Fi Direct technology on the Centrino 2 platform. 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. Atheros, Broadcom, Intel, Ralink and Realtek announced their first products in October, 2010. Redpine Signals' chipset is Wi-Fi Direct certified in November,2010. Google announced Wi-fi Direct support in Android 4.0 in October, 2011. While some Android 2.3 devices 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 API for developers to use for application development.
- "Wi-Fi Protected Setup", Wi-Fi Alliance Knowledge base
- Glenn Fleishman, "Broadcom squeezes 11n, Bluetooth, FM into new, cheap chip", ars technica, 8 December 2008
- Chris Foresman, "Wi-Fi Direct protocol to ease peer-to-peer WiFi connections", ars technica, 14 October 2009
- "Wi-Fi CERTIFIED Interoperability Certificate Certification ID: WFA8921", Wi-Fi Alliance, 1 November 2010
- Welcome to the Freedom of Portable Wi-Fi, Intel My WiFi Pocket Book
- Wi-Fi Direct Products Connect Without A Network
- Redpine Signals’ Lite-Fi® – Ultra Low Power 802.11n – RS9110 Chipset Achieves Wi-Fi Direct™ Certification
- Android 4 at developer.android.com