sensys-ch5-mac

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Schedule- vs. contention-based MACs • Schedule-based MAC • A schedule exists, regulating which participant may use which resource at which time (TDMA component) • Typical resource: frequency band in a given physical space (with a given code, CDMA) • Schedule can be fixed or computed on demand • Usually: mixed – difference fixed/on demand is one of time scales • Usually, collisions, overhearing, idle listening no issues • Needed: time synchronization! • Contention-based protocols • Risk of colliding packets is deliberately taken • Hope: coordination overhead can be saved, resulting in overall improved efficiency • Mechanisms to handle/reduce probability/impact of collisions required • Usually, randomization used somehow SS 05 Ad hoc & sensor networs - Ch 5: MAC protocols 8
Overview • Principal options and difficulties • Contention-based protocols • MACA • S-MAC, T-MAC • Preamble sampling, B-MAC • PAMAS • Schedule-based protocols • IEEE 802.15.4 SS 05 Ad hoc & sensor networs - Ch 5: MAC protocols 9
Page 1 and 2: Ad hoc and Sensor Networks Chapter
Page 3 and 4: Overview • Principal options and
Page 5 and 6: Requirements for energy-efficient M
Page 7: Centralized medium access • Idea:
Page 11 and 12: Main options to shut up senders •
Page 13 and 14: RTS/CTS • RTS/CTS ameliorate, but
Page 15 and 16: Sensor-MAC (S-MAC) • MACA’s idl
Page 17 and 18: Timeout-MAC (T-MAC) • In S-MAC, a
Page 19 and 20: B-MAC • Combines several of the a
Page 21 and 22: Power Aware Multiaccess with Signal
Page 23 and 24: Overview • Principal options and
Page 25 and 26: LEACH rounds SS 05 Ad hoc & sensor
Page 27 and 28: SMACS link setup • Case 1: Node X
Page 29 and 30: TRAMA - adaptive election • Given
Page 31 and 32: Comparison: TRAMA, S-MAC • Compar
Page 33 and 34: IEEE 802.15.4 • IEEE standard for
Page 35 and 36: Wakeup radio MAC protocols • Simp
Page 37: Summary • Many different ideas ex

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