Proposed analytical model based on a three-level renewal process for slotted CSMA in single or double CCA, in saturated or insaturated case to obtain MAC throughput and avg. frame service time.
- The difference between IEEE 802.15.4 MAC and the classical slotted CSMA is a node can transmit packet only after two CCA of idle channel in the former, whreas only one channel sensing in the latter.
- In WLAN IEEE 802.11, the backoff counter does not freeze when the channel is busy, instead keeps decreasing untill reach zero, and transmits immediately after reach zero. While IEEE 802.15.4 transmits only after sensong two consecutive idle slots.
- The authors proposed the 3-level renewal prosess wich consist of :
– Level-1 : cycle that contain no transmission and contain transmission.
– Level-2 : cycle which collision and successful transmission
– Level-3 : cycle for successful transmission.
- Derive mathematical model for one CCA, double CCA, avg. service time and throughput for saturated and non-saturated model.
- The outputs : number of nodes vs. throughput; number of nodes vs. service time; number of nodes vs. transmission successful probability ; number of nodes vs. channel busy probability; saturation throughput between one CCA and double CCA; arrival rate vs. service time for unsaturated case.
“A Renewal Theory Based Analytical Model for the Contention Access Period of IEEE 802.15.4 MAC”, by Xinhua Ling, Yu Cheng, Jon W. Mark, Xuemin (Sherman) Shen
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Sharpen your concentration.
April 26, 2010