1) The 802.15.4 beacon-enabled PAN uses slotted CSMA/CA algorithm and there ie a strong probability that collision and retransmission occur. There is no way to detect hidden node problem unlike IEEE 802.11. That’s why IEEE 802.15.4 beacon-enabled mode makes many collisions. If collision occurs, CSMA/CA executes retransmission operation. But in WSN, transmit operation spends high energy consumption.
2) The proposed algorithm derives the parameters to minimize collision and the number of retransmission through traffic monitoring
3) aUnitBackoffPeriod = 20 symbol times = 320 microsecon in 2.4 GHz
4) Comparing with IEEE 802.11 MAC, IEEE 802.15.4 doesn’t use RTS/CTS, so it’s more difficult to detect other nodes’ network traffics and collision probability will be increased according to the number of nodes.
Proposed Algorithm :
1) changing the MIB parameter parameters suitable for adapting the network traffic information.
2) Each node has the node traffic indication value (NTIV) which indicate local traffic rate. The NTIV can be adjusted by some events like ACK received, CCA fail or CSMA success
3) each node calculates its own NTIV and send it to the coordinator.
4) Each node transfers NTIV information within FrameControlField of ACK or Data Frame.
5) The PAN coordinator received packet which has NTIV, the figure out the cluster traffic indication value (CTIV). CTIV represent the global traffic information of that cluster or PAN.
6) The Coordinator broadcast CTIV to other nodes using Frame Control Field of beacon frame
7) The node finally decides the CSMA/CA parameters referencing NTIV and CTIV to minimize the collisions and retransmisson
NACA : A New Adaptive CSMA/CA Algorithm of IEEE802.15.4 in Beacon-enabled Networks.
By Junkeun Song, Kee-Young Shin, Misun Yu, etc
Note : This resume is created for self-learning only. Author and Publisher hold copyrights
Cluster Gate Array
November 27, 2008
High Speed Network Lab