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Nonsaturation Throughput Enhancement of IEEE 802.11b Distributed Coordination Function for Heterogeneous Traffic under Noisy Environment

Dhanasekaran Senthilkumar,A Krishnan,

国际自动化与计算杂志 , 2010,
Abstract: In this paper, we propose a mechanism named modified backoff (MB) mechanism to decrease the channel idle time in IEEE 802.11 distributed coordination function (DCF). In the noisy channel, when signal-to-noise ratio (SNR) is low, applying this mechanism in DCF greatly improves the throughput and lowers the channel idle time. This paper presents an analytical model for the performance study of IEEE 802.11 MB-DCF for nonsaturated heterogeneous traffic in the presence of transmission errors. First, we introduce the MB-DCF and compare its performance to IEEE 802.11 DCF with binary exponential backoff (BEB). The IEEE 802.11 DCF with BEB mechanism suffers from more channel idle time under low SNR. The MB-DCF ensures high throughput and low packet delay by reducing the channel idle time under the low traffic in the network. However, to the best of the authors' knowledge, there are no previous works that enhance the performance of the DCF under imperfect wireless channel. We show through analysis that the proposed mechanism greatly outperforms the original IEEE 802.11 DCF in the imperfect channel condition. The effectiveness of physical and link layer parameters on throughput performance is explored. We also present a throughput investigation of the heterogeneous traffic for different radio conditions.
Probabilistic Modeling of IEEE 802.11 Distributed Coordination Functions  [PDF]
Rui Fang,Zequn Huang,Louis F. Rossi,Chien-Chung Shen
Computer Science , 2014,
Abstract: We introduce and analyze a new Markov model of the IEEE 802.11 Distributed Coordination Function (DCF) for wireless networks. The new model is derived from a detailed DCF description where transition probabilities are determined by precise estimates of collision probabilities based on network topology and node states. For steady state calculations, we approximate joint probabilities from marginal probabilities using product approximations. To assess the quality of the model, we compare detailed equilibrium node states with results from realistic simulations of wireless networks. We find very close correspondence between the model and the simulations in a variety of representative network topologies.
An Improved Analytical Model for IEEE 802.11 Distributed Coordination Function under Finite Load  [PDF]
Rama Krishna CHALLA, Saswat CHAKRABARTI, Debasish DATTA
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2009, DOI: 10.4236/ijcns.2009.23026
Abstract: In this paper, an improved analytical model for IEEE 802.11 distributed coordination function (DCF) under finite load is proposed by closely following the specifications given in IEEE 802.11 standard. The model is investigated in terms of channel throughput under perfect and slow Rayleigh fading channels. It is shown that the proposed model gives better insight into the operation of DCF.
PERFORMANCE STUDY OF DISTRIBUTED COORDINATION FUNCTION OVER IEEE 802.11A PHYSICAL LAYER
S. SELVAKENEDDY
Journal of Engineering Science and Technology , 2006,
Abstract: IEEE 802.11a is one of the latest standards to be released by the IEEE Project 802 for wireless LANs. It has specified an additional physical layer (PHY) to support higher data rates, and is termed as the orthogonal frequency division multiplexing (OFDM). In order to exploit its benefits, one of the medium access control (MAC) protocols specified in the IEEE 802.11 specification is called distributed coordination function (DCF). DCF is a carrier sense multiple access with collision avoidance (CSMA/CA) scheme with slotted binary exponential backoff. The frames can be transmitted using the basic access scheme or the RTS/CTS scheme in DCF. It was demonstrated previously that the RTS/CTS mechanism works well in most scenarios for the previously specified PHYs. In this work, a simple simulator is developed to verify the scalability of the RTS/CTS mechanism over OFDM PHY, which supports much higher data rates.
Dynamic tuning of the IEEE 802.11 distributed coordination function to derive a theoretical throughput limit  [cached]
Huang Yi-Hung,Kuo Chao-Yu
EURASIP Journal on Wireless Communications and Networking , 2011,
Abstract: IEEE 802.11 is the most popular and widely used standard for wireless local area network communication. It has attracted countless numbers of studies devoted to improving the performance of the standard in many ways. In this article, we performed theoretical analyses for providing a solution to the maximum throughput problem for the IEEE 802.11 distributed coordination function, and an algorithm using a binary cubic equation for obtaining a much closer approximation of the optimal solution than previous algorithms. Moreover, by studying and analyzing the characteristics of the proposed algorithm, we found that the effects of backoff counter consecutive freeze process could be neglected or even disregarded. Using the NS2 network simulator, we not only showed that the proposed theoretical analysis complied with the simulated results, but also verified that the proposed approach outperformed others in achieving a much closer approximation to the optimal solution.
Real-Time Performance Analysis of Infrastructure-based IEEE 802.11 Distributed Coordination Function  [PDF]
Feng Xia,Ruixia Gao,Linqiang Wang,Ruonan Hao
Computer Science , 2011,
Abstract: With the increasing popularity of wireless networks, wireless local area networks (WLANs) have attracted significant research interest, which play a critical role in providing anywhere and anytime connectivity. For WLANs the IEEE 802.11 standard is the most mature technology and has been widely adopted for wireless networks. This paper analyzes real-time performance of the IEEE 802.11 standard that adopts the MAC protocol of Distributed Coordination Function (DCF) operating in infrastructure mode. Extensive simulations have been done to examine how the network performance in terms of realtime metrics including effective data rate, latency and packet loss rate will be impacted by some critical parameters (e.g. CWmin and packet payload). The results are presented and analyzed. The analysis of simulation results can provide support for parameter configuration and optimization of WLANs for realtime applications.
Stability and Queueing Analysis of IEEE 802.11 Distributed Coordination Function  [PDF]
Dongjie Yin,Pui King Wong,Tony T. Lee
Computer Science , 2011,
Abstract: 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.
Modelling and Analysis of the Distributed Coordination Function of IEEE 802.11 with Multirate Capability  [PDF]
F. Daneshgaran,M. Laddomada,F. Mesiti,M. Mondin
Computer Science , 2008,
Abstract: The aim of this paper is twofold. On one hand, it presents a multi-dimensional Markovian state transition model characterizing the behavior at the Medium Access Control (MAC) layer by including transmission states that account for packet transmission failures due to errors caused by propagation through the channel, along with a state characterizing the system when there are no packets to be transmitted in the queue of a station (to model non-saturated traffic conditions). On the other hand, it provides a throughput analysis of the IEEE 802.11 protocol at the data link layer in both saturated and non-saturated traffic conditions taking into account the impact of both transmission channel and multirate transmission in Rayleigh fading environment. Simulation results closely match the theoretical derivations confirming the effectiveness of the proposed model.
Modified Isochronous Coordination Function for Enhancement of VoIP Call Capacity over IEEE 802.11 WLAN  [cached]
Gupta Sanjaya,Sahu Vijay,Lall Brejesh
EURASIP Journal on Wireless Communications and Networking , 2008,
Abstract: VoIP over IEEE 802.11 wireless local area network (WLAN) is growing very fast and is providing a cost effective alternative for voice communications. WLANs were initially set up to handle bursty nonreal time type of data traffic. Therefore, the wireless access protocols initially defined are not suitable for voice traffic. Subsequently, updates in the standard have been made to provision for QoS requirements of data, especially the real time traffic of the type voice and video. Despite these updates, however, transmitting voice traffic over WLAN does not utilize the available bandwidth (BW) efficiently, and the number of simultaneous calls supported in practice is significantly lower than what the BW figures would suggest. Several modifications have been proposed to improve the call capacity, and recently isochronous coordination function (ICF) was introduced to mitigate the problem of low call capacity. In this paper, we propose a modified ICF which further improves the performance in terms of the call capacity. The proposed scheme uses multiplexing and multicasting in the downlink to substantially increase the call capacity.
Modified Isochronous Coordination Function for Enhancement of VoIP Call Capacity over IEEE 802.11 WLAN  [cached]
Sanjaya Gupta,Vijay Sahu,Brejesh Lall
EURASIP Journal on Wireless Communications and Networking , 2007, DOI: 10.1155/2008/218076
Abstract: VoIP over IEEE 802.11 wireless local area network (WLAN) is growing very fast and is providing a cost effective alternative for voice communications. WLANs were initially set up to handle bursty nonreal time type of data traffic. Therefore, the wireless access protocols initially defined are not suitable for voice traffic. Subsequently, updates in the standard have been made to provision for QoS requirements of data, especially the real time traffic of the type voice and video. Despite these updates, however, transmitting voice traffic over WLAN does not utilize the available bandwidth (BW) efficiently, and the number of simultaneous calls supported in practice is significantly lower than what the BW figures would suggest. Several modifications have been proposed to improve the call capacity, and recently isochronous coordination function (ICF) was introduced to mitigate the problem of low call capacity. In this paper, we propose a modified ICF which further improves the performance in terms of the call capacity. The proposed scheme uses multiplexing and multicasting in the downlink to substantially increase the call capacity.
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