[info] IBSS (adhoc-mode) does multihop?

Archived from groups: (More info?)

Hey people,

I wanted to know whether, as specified, the IBSS (adhoc) mode of the 802.11b
specification does multi-hop. In the standard case if we have 4 stations
(called A,B,C,D) and they are all in range of each other then they should
all be able to talk to each other (assuming they all are setup with the
correct BSS id etc). Thats fine.

However, what if they are set up in a 'chain', meaning A-B-C-D like so, and
they are laid far enough apart that they can only talk to their neighbours.
Then obviously A can't directly talk to C or D. But as implemented, does
IBSS route the packets (frames?) from A to C via B? Or does it fail and
result in 4 overlapping IBSS's? But that sounds wrong to me.... not the
least because e.g. B will be in both the A-B IBSS and the B-C IBSS, both of
which will have the same BSS id.

Disclaimer: I ask because I am planning to implement this multi-hop
functionality as an undergraduate Senior Project using a fast-graphing
algorithm me and my mates came up with... sortof a showcase. But I don't
want to redo something that the spec already does. If you could cite your
answer in a spec or website where I can get further info, I'd be extremely
obliged.

I apologize if the question is poorly worded. I have just been digging
through the huge 802.11-1999 spec on ieee.org and am completely spaced out.

best, and thanks in advance,
/t.

(public posted replies fine but private replies to
tjaffri-please-no-spam-AT-cs.stanford.ee-dee-you)
4 answers Last reply
More about info ibss adhoc mode multihop
  1. Archived from groups: (More info?)

    I forgot my password for the IEEE Xplore website, but did you try over
    there?
    Probably in the Basic search you can type some thing like "802.11 ad-hoc
    architecture" or "802.11 ad-hoc multi hop" to find relevant publications.

    HTH

    "Taqi Jaffri" <tjaffri@stanford.edu> wrote in message
    news:c4glco$3pp$1@news.Stanford.EDU...
    > Hey people,
    >
    > I wanted to know whether, as specified, the IBSS (adhoc) mode of the
    802.11b
    > specification does multi-hop. In the standard case if we have 4 stations
    > (called A,B,C,D) and they are all in range of each other then they should
    > all be able to talk to each other (assuming they all are setup with the
    > correct BSS id etc). Thats fine.
    >
    > However, what if they are set up in a 'chain', meaning A-B-C-D like so,
    and
    > they are laid far enough apart that they can only talk to their
    neighbours.
    > Then obviously A can't directly talk to C or D. But as implemented, does
    > IBSS route the packets (frames?) from A to C via B? Or does it fail and
    > result in 4 overlapping IBSS's? But that sounds wrong to me.... not the
    > least because e.g. B will be in both the A-B IBSS and the B-C IBSS, both
    of
    > which will have the same BSS id.
    >
    > Disclaimer: I ask because I am planning to implement this multi-hop
    > functionality as an undergraduate Senior Project using a fast-graphing
    > algorithm me and my mates came up with... sortof a showcase. But I don't
    > want to redo something that the spec already does. If you could cite your
    > answer in a spec or website where I can get further info, I'd be extremely
    > obliged.
    >
    > I apologize if the question is poorly worded. I have just been digging
    > through the huge 802.11-1999 spec on ieee.org and am completely spaced
    out.
    >
    > best, and thanks in advance,
    > /t.
    >
    > (public posted replies fine but private replies to
    > tjaffri-please-no-spam-AT-cs.stanford.ee-dee-you)
    >
    >
  2. Archived from groups: (More info?)

    An IBSS is an ad-hoc point-to-point network. There is no controlling station
    taking the role of AP. There is no routing, no forwarding or packet
    bridging, of any kind. All stations must be able to directly receive the
    signals of all other stations. An ad-hoc network can be set up in which this
    requirement is violated, which means not only that some stations won't be
    able to talk to one another, but also that the so-called hidden node problem
    occurs - some stations cannot detect frames sent between other stations, and
    attempt to transmit at the same time, jamming the network and eventually
    causing the overall bitrate to degrade.

    It's always possible that I missed something in the standard, but that's my
    understanding. Can you name the clauses in the spec that describe what
    you're calling multihop functionlity?

    "Taqi Jaffri" <tjaffri@stanford.edu> wrote in message
    news:c4glco$3pp$1@news.Stanford.EDU...
    > Hey people,
    >
    > I wanted to know whether, as specified, the IBSS (adhoc) mode of the
    802.11b
    > specification does multi-hop. In the standard case if we have 4 stations
    > (called A,B,C,D) and they are all in range of each other then they should
    > all be able to talk to each other (assuming they all are setup with the
    > correct BSS id etc). Thats fine.
    >
    > However, what if they are set up in a 'chain', meaning A-B-C-D like so,
    and
    > they are laid far enough apart that they can only talk to their
    neighbours.
    > Then obviously A can't directly talk to C or D. But as implemented, does
    > IBSS route the packets (frames?) from A to C via B? Or does it fail and
    > result in 4 overlapping IBSS's? But that sounds wrong to me.... not the
    > least because e.g. B will be in both the A-B IBSS and the B-C IBSS, both
    of
    > which will have the same BSS id.
    >
    > Disclaimer: I ask because I am planning to implement this multi-hop
    > functionality as an undergraduate Senior Project using a fast-graphing
    > algorithm me and my mates came up with... sortof a showcase. But I don't
    > want to redo something that the spec already does. If you could cite your
    > answer in a spec or website where I can get further info, I'd be extremely
    > obliged.
    >
    > I apologize if the question is poorly worded. I have just been digging
    > through the huge 802.11-1999 spec on ieee.org and am completely spaced
    out.
    >
    > best, and thanks in advance,
    > /t.
    >
    > (public posted replies fine but private replies to
    > tjaffri-please-no-spam-AT-cs.stanford.ee-dee-you)
    >
    >
  3. Archived from groups: (More info?)

    Gary,

    > It's always possible that I missed something in the standard, but that's
    my
    > understanding. Can you name the clauses in the spec that describe what
    > you're calling multihop functionlity?
    >

    You are probably right; and I didn't see anything that said this in the
    spec. However, I do believe that the term 'adhoc network' is overloaded and
    other than the 802.11 mode it might also mean a self-configuring multi-hop
    'mesh-type' network. Thats why I wanted to make sure what the 802.11 mode
    exactly does since I would look pretty silly implementing something on top
    of IBSS that the standard already did.

    Kalyan, thanks for the idea. I will try to get into IEEE XPlore today.

    Thanks to both of you. Other comments always welcome.

    /t.
  4. Archived from groups: (More info?)

    Well, actually the term ad-hoc is Latin for "concerning the thing". It's a
    generic term originally used to refer to any attempt to address a single
    specific issue. For example, an ad-hoc committee is usally set up in
    response to a a single problem, exists only to solve it, then dissolves. It
    usually connotes an informal, relatively unstrucutured approach.

    In networking, the usage has these properties. It doesn't precisely refer to
    a "self-configuring" network that can be joined by any station without
    reconfiguring the rest of the network, because this is true both of an IBSS,
    and a BSS supported by an AP. Joining an infrastructure network has no more
    effect on the rest of the stations than joining an ad-hoc net. The main
    difference is that an IBSS exists only to support the fundamental
    requirements of sharing a channel - sensing other transmitters, avoiding
    collisions, and sharing timing information to synchronize logical clocks. It
    doesn't support a backend distribution system, roaming, solving the hidden
    node problem, or any of the other value-adds that come with an
    infrastructure nework. It exists to solve a single, specific problem in a
    relatively unstructured way - hence, it is an ad-hoc network.


    "Taqi Jaffri" <tjaffri@stanford.edu> wrote in message
    news:c4hnsi$3ua$1@news.Stanford.EDU...
    > Gary,
    >
    > > It's always possible that I missed something in the standard, but that's
    > my
    > > understanding. Can you name the clauses in the spec that describe what
    > > you're calling multihop functionlity?
    > >
    >
    > You are probably right; and I didn't see anything that said this in the
    > spec. However, I do believe that the term 'adhoc network' is overloaded
    and
    > other than the 802.11 mode it might also mean a self-configuring multi-hop
    > 'mesh-type' network. Thats why I wanted to make sure what the 802.11 mode
    > exactly does since I would look pretty silly implementing something on top
    > of IBSS that the standard already did.
    >
    > Kalyan, thanks for the idea. I will try to get into IEEE XPlore today.
    >
    > Thanks to both of you. Other comments always welcome.
    >
    > /t.
    >
    >
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