Introduction to Wi-Fi Direct

1. Introduction to Wi-Fi Direct

Wei-Tsung Su (3% 48 %)

[email protected]

11/22/2012 Ubiquitous Computing and Ambient Networking Laboratory

2. References

° Wi-Fi Alliance — Wi-Fi Direct
— http://www.wi-fi.org/discover-and-learn/wi-fi-direct
+ Wi-Fi Direct Industry Whitepaper
— http://www.wi-fi.org/knowledge-center/white-papers/wi-fi-
certified-wi-fi-direct%E2%84%A2-personal-portable-wi-
fi%C2%AE-technology-2010
+ Wi-Fi Direct Consumer Whitepaper
— http://www.wi-fi.org/knowledge-center/white-papers/wi-fi-
certified-wi-fi-direct%E2%84%A2-personal-portable-wi-
fIXC2%AE-connect-devices
+ HUGHES Systique Wi-Fi Direct Whitepaper
— http://hsc.com/Portals/0/Uploads/Articles/WFD_Technology

Whitepaper_v_1.7635035318321315728.pdf

11/22/2012 Ubiquitous Computing and Ambient Networking Laboratory

3. Purpose

+ Create direct connections between Wi-Fi client
devices without a traditional Wi-Fi infrastructure
network.

+ For example,

— Users can print documents directly to a Wi-Fi printer
with their laptops.

— Users can cast videos directly to a Wi-Fi TV with their
smart phones.

11/22/2012 Ubiquitous Computing and Ambient Networking Laboratory

4. How Wi-Fi Direct Works?

Grou
Group B

08

GO nek
ey SS o A
u =" Connection
_— >

Le
oN

ion
One-to-one configuration One-to-many configuration
As long as one device in a connection is
Wi-Fi Direct-certified, you can connect all

devices without a Wi-Fi home network or
hotspot.

GO is short for Group Owner

11/22/2012 Ubiquitous Computing and Ambient Networking Laboratory

5. Key Mechanisms

Device Discovery
Service Discovery
Group Formation
Invitation
Client Discovery
Power Management
P2P-PS and P2P-WMM-PS

Notice of Absence

Opportunistic Power Save

11/22/2012 Ubiquitous Computing and Ambient Networking Laboratory

6. Device Discovery

+ Identify other Wi-Fi Direct devices and establish
a connection
— If the target is not in a Group, a new Group is formed
* GO is negotiated.

— If the target is already part of a Group, the searching
device may attempt to join the existing Group.

+ Wi-Fi Protected Setup (WPS) is used to obtain
credentials and authenticate the searching
device.

11/22/2012 Ubiquitous Computing and Ambient Networking Laboratory

7. Service Discovery (Optional)

+ Advertise the higher layer applications to other
Wi-Fi Direct devices (even before a connection is
formed).

— For example, Wi-Fi printer can advertise its printing
services to other Wi-Fi Devices

+ Implementation is vender-specific.

11/22/2012 Ubiquitous Computing and Ambient Networking Laboratory

8. Group Formation

.

.

Once a Wi-Fi Direct connection is established between two Wi-Fi Direct
devices, a Group is formed.

However, a Group may be created by a single Wi-Fi Direct device
— Required when connecting a legacy device

— Desirable when creating a Group to offer a specific service (e.g. Internet
connection sharing.)

Once a Group is formed, other devices can join this Group as join a AP.

A Group can be
— temporary Group (single instance)
— Persistent Group (multiple, recurring use)

11/22/2012 Ubiquitous Computing and Ambient Networking Laboratory

9. Invitation (Optional)

« After a Group is formed,
a Wi-Fi Direct device may
invite another Wi-Fi
Direct device to join the MIT
Group.
The decision of whether
or not to accept an
invitation is left to the
invited Wi-Fi Direct
device.

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10. Client Discovery

+ Enabling a Wi-Fi Direct device to discover which
Wi-Fi Direct devices are in an existing Group.

* Locate and connect to a specific device or device

type.
— For example, a camera can query to see if any Wi-Fi
devices are printers in a Group.

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11. Power Management

« P2P-PS and P2P-WMM-PS
— based on Wi-Fi Power Save (PS) and WMM-PS
Notice of Absence
— Signal a planned absence
Opportunistic Power Save
— Save power by entering doze state
— Group owner is available on a periodic basis.

If legacy devices are present, these power
management functions cannot be employed.

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12. Important Capabilities

Persistent Group

Concurrent Connection

Multiple Groups

Cross-connection

Managed Device

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Page : 13

13. Persistent Group (Optional)

« Persistent Group may be restarted without
provisioning, eliminating the need to repeat
tasks such as entering a WPS PIN.

¢ Persistent Group are invoked using Invitation
mechanism. That is, all Wi-Fi Direct devices must
support Invitation in a Persistent Group.

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14. Concurrent Connection (Optional)

+ Concurrent connection
— Concurrent devices can be in a group while maintaining a
WLAN infrastructure connection at the same time.
+ Multiple group
— Join multiple Groups
+ Cross-connection
— Provide infrastructure access to other devices in the Group
— Concurrent operation requires support for multiple and
distinct MAC entities.
+ One for operation as a WLAN-STA
+ One for operation as a Wi-Fi Direct device

+ Implementation is vender-specific

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15. Managed Environments (Optional) À

+ A Wi-Fi AP may implement capabilities that allow
it to manage Wi-Fi Direct devices for efficiency
and security issues. For example,

— enforce Wi-Fi Direct devices do not use 802.11b for
data and management frames.

— de-authentication any Wi-Fi Direct device from the
infrastructure network for our-of-policy behavior.

« For example, all client devices that Cross-connection is not
allowed if they attempt to access infrastructure network
resources.

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16. Wi-Fi Direct Certification Program

+ Wi-Fi CERTIFIED Wi-Fi Direct devices must
implement Wi-Fi Peer-to-Peer technology (P2P).
Wi-Fi CERTIFIED Wi-Fi Direct devices must pass the
following certification tests
— Baseline Wi-Fi certification tests

+ At least 802.11g as well as WPA2-Personal

— Wi-Fi Multimedia (WMM) and Wi-Fi Protected Setup
(WPS) certification tests

+ WMM and WPS are optional Wi-Fi Alliance certification, but
both are mandatory for Wi-Fi Direct certification

— All mandatory certification tests

— Optional features certification tests. (tested if
implemented.)

11/22/2012 Ubiquitous Computing and Ambient Networking Laboratory