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802.11p Open Issues.

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Presentation on theme: "802.11p Open Issues."— Presentation transcript:

1 802.11p Open Issues

2 Multiple WBSS 802.11p does not explain STA behavior in the presence of multiple WBSSs.  Can a STA join more than one WBSS at a time?  Can a STA both provide a WBSS and join another one at the same time?  If STAs are expected to be rapidly mobile, and passing along data frames (which I gather is the intent), it's not at all obvious how that is supposed to work.

3 Starbucks Problem One scenario is that a car with a WAVE mode radio pulls into the drive-through of a Starbucks.  It is within range of a normal Wi-Fi (a/b/g) beacon. It is clearly technically feasible for the car to scan for such beacons.  Would it be within the standard for the car to temporarily join the Starbucks infrastructure BSS, e.g. to download some music? If yes, would it be considered the WAVE mode STA that joined the infrastructure BSS, or would it require a non-WAVE mode STA (i.e. either a second STA or the original STA switching into non-WAVE mode)? If it is a non-WAVE mode STA, i.e. the MIB attribute is false, how does the MIB attribute get turned off, and then turned back on again when the car drives away from Starbucks and resumes its WAVE mode operations?

4 Transmit Power Control
This sub clause (11.8) describes TPC procedures that may satisfy needs in many regulatory domains and other frequency bands and may be useful for other purposes (e.g., reduction of interference, range control, reduction of power consumption). TPC is addressed in the document both for BSS and IBSS but NOT for WBSS TPC becomes an interesting problem in the truly mobile ad hoc network. With implications for channel congestion and cross channel interference TPC procedures for BSS and IBSS are clearly stated. Do we require similar procedures for WBSS?

5 Lack of A&A Several Comments
Since there are no authentication and no association in a WBSS, it is unlikely that the WBSS provider keeps track of connectivity with WBSS users. For example, when a WBSS user moves out of a WBSS provider's coverage, the WBSS provider cannot know whether the WBSS user exists in its WBSS or not due to the absence of the de-association process. In such environments, if the WBSS provider has a frame destined for the WBSS user in its buffer, it continues to transmit the frame until the number of retransmissions reaches a predefined threshold. Moreover, in a multi-rate WBSS the WBSS provider, in the absence of ACK frames, may use a lower bit-rate since it deems that the distance between the WBSS provider and user is getting farther or the radio condition becomes poorer, which results in the severe waste of the wireless channel.

6 Accessing a DS How does a STA in WAVE mode access a DS in the absence of Authentication and Association?


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