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The Effect of Exerting Adequate Persistence in Collision Avoidance Protocols

The Effect of Exerting Adequate Persistence in Collision Avoidance Protocols. J.J. Garcia-Luna-Aceves and Makis Tzamaloukas {jj, jamal}@cse.ucsc.edu Computer and Communications Research Group (CCRG) http://www.cse.ucsc.edu/research/ccrg.

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The Effect of Exerting Adequate Persistence in Collision Avoidance Protocols

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  1. The Effect of Exerting Adequate Persistence in Collision Avoidance Protocols J.J. Garcia-Luna-Aceves and Makis Tzamaloukas {jj, jamal}@cse.ucsc.eduComputer and Communications Research Group (CCRG)http://www.cse.ucsc.edu/research/ccrg Computer Engineering DepartmentJack Baskin School of EngineeringUniversity of CaliforniaSanta Cruz, CA 95064

  2. Presentation Outline • Non-persistent collision avoidance protocols • Motivation • Limited persistence issues • Limited persistence protocols: • FAMA-LCS, RIMA-SPL, RIMA-DPL • Throughput analysis • Conclusions JJ. Garcia-Luna-Aceves and A. E. Tzamaloukas

  3. Non-persistent MAC Protocols • SRMA (Kleinrock and Tobagi, August ‘76) • MACA (Karn, April ‘90) • MACAW (Bharghavan, Demers, Shenker and Zhang, August ‘94) • FAMA (Garcia-Luna-Aceves and Fullmer, September ‘97) • IEEE 802.11 (July ‘97) • RIMA (Garcia-Luna-Aceves and Tzamaloukas, August ‘99) JJ. Garcia-Luna-Aceves and A. E. Tzamaloukas

  4. Motivation • Improve performance achieved with non-persistent protocols at light-moderate loads: • reduced number of times a single node with a packet to send after sensing the channel busy must back off • smaller idle periods • Modify traditional persistent strategies: • node persists to transmit a packet only for a limited amount of time • reduced amount of contention when the channel becomes idle JJ. Garcia-Luna-Aceves and A. E. Tzamaloukas

  5. ongoing transmission collision 1-Persistent Carrier Sensing • Definition: Any node that has a local DATA packet to send will persist to sense the channel until no carrier is detected. At that time, with probability 1 the node will transmit the packet • Claim: Persisting over an entire DATA packet limits throughput JJ. Garcia-Luna-Aceves and A. E. Tzamaloukas

  6. Limited Persistence Carrier Sensing • DEFINITION: persistent carrier sensing up to h seconds after detecting carrier to limit contention • FAMA-LCS (Floor Acquisition Multiple Access with Limited-persistence Carrier Sensing) • RIMA-SPL (Receiver Initiated Multiple Access with Single Poll and Limited-persistence carrier sensing) • RIMA-DPL (Receiver Initiated Multiple Access with Dual Poll and Limited-persistence carrier sensing) JJ. Garcia-Luna-Aceves and A. E. Tzamaloukas

  7. FAMA-LCS JJ. Garcia-Luna-Aceves and A. E. Tzamaloukas

  8. RIMA-SPL JJ. Garcia-Luna-Aceves and A. E. Tzamaloukas

  9. RIMA-DPL JJ. Garcia-Luna-Aceves and A. E. Tzamaloukas

  10. Idle Busy Busy Busy Idle Busy TP2 TP1 TP0 TP0 TP1 TP1 h h Throughput Analysis Model • All the assumptions made for the analysis of non persistent protocols are valid here as well • Divide time into transmission periods (TP) • The type of a TP that follows another TP depends on the number of those persistent users waiting for the current TP to end JJ. Garcia-Luna-Aceves and A. E. Tzamaloukas

  11. P 01 0 P 1 P 00 11 P 10 P P 21 P 20 12 2 P 22 Throughput Analysis Model • Since we assume Poisson arrivals, what occurs in a given TP depends only on what happens in the previous TP • Define the state of the system at the beginning of a TP to be the type of that TP (i.e. state 0 is TP0) • These states correspond to a three-state Markov chain embedded at the beginning of the TP JJ. Garcia-Luna-Aceves and A. E. Tzamaloukas

  12. Throughput Analysis Model • fully-connected network of N nodes • single, unslotted channel, error-free • the size for an RTR, RTS and CTS is  seconds; the size for a data packet is  seconds • the turn-around time is considered to be part of the duration of control and data packet • the propagation delay of the channel is  seconds • a polled node receiving an RTR always has a data packet to send • the probability that the packet is addressed to the polling node is 1/N JJ. Garcia-Luna-Aceves and A. E. Tzamaloukas

  13. FAMA RIMA-SP Throughput results • Throughput vs. offered load for 1Mbps channel and 500 bytes DATA packets; network of 10 nodes JJ. Garcia-Luna-Aceves and A. E. Tzamaloukas

  14. Throughput results • Throughput vs. offered load for 1Mbps channel and 500 bytes DATA packets for RIMA-DP; network of 10 nodes JJ. Garcia-Luna-Aceves and A. E. Tzamaloukas

  15. Conclusions • We present a first approach of limited persistence in collision-avoidance protocols • Variations of well-known non-persistent sender and receiver-initiated protocols were proposed to demonstrate the effects of applying limited persistence • Our performance analysis results showed considerable benefits when adopting a limited carrier sensing approach • Since all the protocols considered provide correct floor acquisition our results can be extrapolated to networks with hidden terminals JJ. Garcia-Luna-Aceves and A. E. Tzamaloukas

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