WiFi Direct Introduction

In WiFi Direct, Devices will directly communicate without the need of AP. In a P2P group one device will have AP-Like functionality and that device is called GO (Group owner), and devices connected through to the GO is called GC (Group Clients). Any device that supports WiFi Direct will be capable of being a GO or GC. Devices will be come GO or GC based on the handshake happening at the time of Group Formation. We can discuss about the Group Formation procedures in the later posts. In a Group there will be one GO, and there will be many GCs connected to the GO.

P2P supported device can operate at concurrent mode as well. In concurrent mode P2P device can connect to the Infrastructure AP. So ,P2P device can operate at GO+STA or GC+STA mode. Here we will have two interfaces when P2P device is operating at concurrent mode. In P2P concurrent mode both the interfaces may be on the same channel. Still there is a use-case that both the interfaces will be operating on different channels or different bands.

In the Below Figure , Observe that P2P Device in a concurrent operation.

Device should support at least 802.11g rates to support WiFi Direct.

To support efficient wireless use P2P devices

  1. Should not use 11b Rates (1,2,5.5,11) for data and management frames except:
    1. Probe Request frames sent to both P2P and non-P2P devices.
  2. P2P Devices shall not respond to the Probe request Frames that indicate support for 11b rates only.

Note 1: P2P GO sends the Beacon using OFDM. Observe the below frame capture for Beacon frame from GO.

Note 2: P2P GO transmits the Probe Response using the OFDM rates, including frames sent in response to Probe Request received at 11b rates from non 11b only devices.

Note 3 : P2P devices shall not include 11b rates in the list of supported rates in probe request frame intended only for P2P Devices.

Note 4: 11b rates may be included in the list of supported rates in probe request frames intended for both P2P and Devices and non P2P devices.

Bottom line here is , P2P only devices will not support 11b rates (Legacy rates). P2P devices should support minimum 11g rates.

In the below sniffer capture observe that the supported rates from the P2P GO Beacon.

In the next post, we will learn about P2P Discovery procedure.