• By (Deleted User)

    How is medium contention regulated in a point-to-multipoint configuration? Is it PCF or RTS/CTS or something else? I can not imagine that this configuration functions in DCF as the CPEs do not "hear" eachother. Anyway, information on a configuration like this is greatly appreciated.



  • Hi Benny:

    When you say that the point to multipoint CPE's (customer premise equipment?) do not hear each other, I assume you mean that most of the wireless bridges are not within receiver range of each others transmissions.

    Consider the main bridge to be an access point (AP) and all the other bridges to be client stations that associate with the AP. To each other the stations are hidden nodes. DCF with RTS/CTS is the classic solution for this problem.

    Wireless bridges are vendor proprietary AP's not anticipated by the IEEE 802.11 design. They extend the 802.11 design by allowing one "bridge" AP to associate to another normal or "bridge" AP much like a standard client station would, and then truncate the design by disallowing normal client stations from associating with the "bridge" AP.

    Have a great day. /criss

  • By (Deleted User)

    I mean with "do not hear each other", that one of the bridges is equipped with a sector antenna and the others (CPEs) with directional antennas. The bridges with directional AEs are not within range of each other.

    Your opinion is that this is normally resolved through the use of DCF with RTS/CTS.

    Do you know where I can verify this? Or do you have an example of tech specs of a bridge where this is mentioned?

  • Hi Benny:

    Yes, I thought you might mean directional antennaes as well.

    Yes, RTS/CTS is my opinion based on my understanding of the building blocks provided by 802.11. I read Cisco's 802.11 bridge documentation a few months ago, but I do not recall them getting down into the underlying physical realities of 802.11 such as how associations might be used between access points.

    Hopefully someone on the forum can put a protocol analyzer to the equipment and report first hand what is going down. I have the analyzer but not the bridges. Other clues could be had from the management screens of the bridges in how each refers to the other bridges.

    Thanks. /criss

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