2 research outputs found
Performance Analysis of Markov Modulated 1-Persistent CSMA/CA Protocols with Exponential Backoff Scheduling
This paper proposes a Markovian model of 1-persistent CSMA/CA protocols with
K-Exponential Backoff scheduling algorithms. The input buffer of each access
node is modeled as a Geo/G/1 queue, and the service time distribution of each
individual head-of-line packet is derived from the Markov chain of the
underlying scheduling algorithm. From the queuing model, we derive the
characteristic equation of network throughput and obtain the stable throughput
and bounded delay regions with respect to the retransmission factor. Our
results show that the stable throughput region of the exponential backoff
scheme exists even for an infinite population. Moreover, we find that the
bounded delay region of exponential backoff is only a sub-set of its stable
throughput region due to the large variance of the service time of input
packets caused by the capture effect. All analytical results presented in this
paper are verified by simulations.Comment: 24 pages including 11 figure
Stability and Queueing Analysis of IEEE 802.11 Distributed Coordination Function
A widely adopted two-dimensional Markov chain model of the IEEE 802.11 DCF
was introduced by Bianchi to characterize the backoff behavior of a single node
under a saturated traffic condition. Using this approach, we propose a queuing
model for the 802.11 DCF under a non-saturated traffic environment. The input
buffer of each node is modeled as a Geo/G/1 queue, and the packet service time
distribution is derived from Markov state space of 802.11 DCF with the
underlying scheduling algorithm. The DCF defines two access mechanisms, namely
the Basic access mechanism and the request-to-send/clear-to-send (RTS/CTS)
access mechanism. Based on our model, performance analyses of both schemes are
studied with probabilistic exponential backoff scheduling. We obtain the
characteristic equation of network throughput and expressions of packet
queueing delay. Specifically, we obtain the stable throughput and bounded delay
regions with respect to the retransmission factor according to the basic
queueing analysis. For both access schemes, the bounded delay region is a
subset of the stable throughput region. Our results show that the RTS/CTS
access mechanism is more stable and performs better than the Basic access
mechanism. The analysis in this paper is verified by simulation results.Comment: 26 pages, 7 figures, and 2 tabl