Title   name
KSIAM 2006 Annual Meeting
  Speaker   Bae, Yun Han  
  Date 2006-11-25
  Place 건국대학교
  File  의 1 번째 Real Media 동영상입니다. 의 1 번째 강연자료입니다.
Abstract : Recently, there has been a significant increase in research of wireless sensor networks (WSN).Network communication requirement of WSN is different from that of the traditional networkbecause the traditional performance criteria of network are throughput, latency and fairness,whereas in WSN, energy efficiency become more important. Making a system energy efficientin WSN is a challenging research topic and researchers have developed many algorithms [1,2,3].In this paper, we propose an analytical model of IEEE 802.15.4 which is standardized towardlow complexity, low power consumption and low data rate wireless data connectivity. This standardallows two network topologies: star and peer-to-peer. In a star topology, every sensors mustcommunicate through PAN coordinator. In a peer-to-peer topology, all devices can communicateeach other if both devices are within a physical range. In a star topology, network uses twotypes of network channel access mechanism. One is based on the slotted CSMA/CA in whichslots are aligned with the beacon enabled. Another access mechanism is based on the unslottedCSMA/CA without beacon frame.This paper concentrates on the MAC performance of the IEEE 802.15.4 network with starshaped non-beacon mode and unslotted CSMA/CA channel access mechanism under nonsaturatedmodes. We believe that many WSN applications such as [4] would benefit from thisanalytical model. Our approach is to model the stochastic behavior of one device as a discretetime Markov chain. Our Markov chain model is different from one of IEEE 802.11 [5], sinceno freezing of backoff counter operates during the transmission of other devices and two CCAsare needed in IEEE 802.15.4. Park et al. [6] also proposed analysis on IEEE 802.15.4 but theyfocused on saturated mode where devices have always packets to send.In this paper, we investigate MAC performance of the IEEE 802.15.4 in non-saturatedmode, where the packet arrival process to device follows Bernoulli process. We construct 3-dimensional Markov chain by adding the information of queue length, whose one-step transitionprobability matrix P has a form of QBD type. We derive the steady state distribution ofthe Markov chain by applying the matrix geometric method and probability generating functionof HoL-delay of a packet. We obtain several performance measures such as non-saturationthroughput, HoL-delay of a packet, average energy consumption and packet loss probability.