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Busy Elimination Multiple Access

Busy Elimination Multiple Access. Dramatically reduces collisions in data broadcasting due to the hidden terminal problem Geared to support prioritization of data transmissions Geared for use in mobile ad-hoc networks Has little overall control overhead and provides impressive good-put.

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Busy Elimination Multiple Access

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  1. Busy Elimination Multiple Access • Dramatically reduces collisions in data broadcasting due to the hidden terminal problem • Geared to support prioritization of data transmissions • Geared for use in mobile ad-hoc networks • Has little overall control overhead and provides impressive good-put

  2. Reliable broadcast problem • Transmissions collide at the common neighbor • SOLUTION: Common neighbor should arbitrate between its neighbors

  3. C B A E D A B C data transmission busy signal (Double power transmission) busy signal Channel Reservation to overcome hidden terminal problem • Common neighbor warns other neighbors when it is receiving transmission from any neighbor • Busy Tone Multiple Access(BTMA) – Channel reservation with distinct frequency busy signal (FDMA) • Busy Elimination Multiple Access (BEMA)– Channel reservation with a busy timeslot (TDMA)

  4. BEMA protocol • Rounds consist of BUSY/CONTROL phase and DATA phase • Each potential sender transmits for random/priority-based period of time bounded by Δ - β • Contender listens for a busy signal or collision AFTER it completes its busy signal transmission • Transmitter of longest duration signal wins

  5. DATA DATA BEMA in action 2 1 3 4 i j k • i and k compete • i wins and transmits data for 2 rounds • j and k transmit busy signal for entire busy timeslot in the meantime • k competes again

  6. BEMA: Protocol Actions {idle, candidate, waiting, leader, locked} DATA PHASE ACTIONS – 3,4,5 CONTROL PHASE ACTIONS – 1,2,6

  7. Logical Proof Lemma 1: If no leader in the beginning of a round at most one leader in one-hop neighborhood of any node k Lemma 2: If j is a neighbor of k and j is a leader k must be ‘locked’ to j Lemma 3: If j is a neighbor of k and j is a leader in the beginning of a round  no other node can transmit in the DATA phase of the round Lemma 4: Starting from the initial state  at most one leader in one-hop neighborhood of any node k Hence hidden terminal problem does not arise

  8. Number of Collisions • Collisions in BEMA and BMMM` remain largely constant with increase in traffic load

  9. Good-put (True Data throughput) • BMMM` suffers heavily due to high control overhead • BSMA’s good-put decrease almost linearly as the number of collisions increase. • CSMA’s good-put is high and constant because the data loss due to collisions is made up with the increase in transmitters transmitting with NO overhead.

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