Dynamic tuning of the IEEE 802.11 protocol to achieve a theoretical throughput limit
TL;DR: A distributed algorithm is proposed that enables each station to tune its backoff algorithm at run-time and indicates that the capacity of the enhanced protocol is very close to the theoretical upper bound in all the configurations analyzed.
Abstract: In wireless LANs (WLANs), the medium access control (MAC) protocol is the main element that determines the efficiency in sharing the limited communication bandwidth of the wireless channel. In this paper we focus on the efficiency of the IEEE 802.11 standard for WLANs. Specifically, we analytically derive the average size of the contention window that maximizes the throughput, hereafter theoretical throughput limit, and we show that: 1) depending on the network configuration, the standard can operate very far from the theoretical throughput limit; and 2) an appropriate tuning of the backoff algorithm can drive the IEEE 802.11 protocol close to the theoretical throughput limit. Hence we propose a distributed algorithm that enables each station to tune its backoff algorithm at run-time. The performances of the IEEE 802.11 protocol, enhanced with our algorithm, are extensively investigated by simulation. Specifically, we investigate the sensitiveness of our algorithm to some network configuration parameters (number of active stations, presence of hidden terminals). Our results indicate that the capacity of the enhanced protocol is very close to the theoretical upper bound in all the configurations analyzed.
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TL;DR: This paper presents a detailed study on recent advances and open research issues in WMNs, followed by discussing the critical factors influencing protocol design and exploring the state-of-the-art protocols for WMNs.
4,205 citations
01 Jul 2003
TL;DR: The important role that mobile ad hoc networks play in the evolution of future wireless technologies is explained and the latest research activities in these areas are reviewed, including a summary of MANETs characteristics, capabilities, applications, and design constraints.
Abstract: Mobile ad hoc networks (MANETs) represent complex distributed systems that comprise wireless mobile nodes that can freely and dynamically self-organize into arbitrary and temporary, ‘‘ad-hoc’’ network topologies, allowing people and devices to seamlessly internetwork in areas with no pre-existing communication infrastructure, e.g., disaster recovery environments. Ad hoc networking concept is not a new one, having been around in various forms for over 20 years. Traditionally, tactical networks have been the only communication networking application that followed the ad hoc paradigm. Recently, the introduction of new technologies such as the Bluetooth, IEEE 802.11 and Hyperlan are helping enable eventual commercial MANET deployments outside the military domain. These recent evolutions have been generating a renewed and growing interest in the research and development of MANET. This paper attempts to provide a comprehensive overview of this dynamic field. It first explains the important role that mobile ad hoc networks play in the evolution of future wireless technologies. Then, it reviews the latest research activities in these areas, including a summary of MANETs characteristics, capabilities, applications, and design constraints. The paper concludes by presenting a set of challenges and problems requiring further research in the future. � 2003 Elsevier B.V. All rights reserved.
1,430 citations
07 Nov 2002
TL;DR: This paper proposes a scheme named DCF+, which is compatible with DCF, to enhance the performance of reliable transport protocol over WLAN and introduces an analytical model to compute the saturated throughput of WLAN.
Abstract: IEEE 802.11 medium access control (MAC) is proposed to support asynchronous and time bounded delivery of radio data packets in infrastructure and ad hoc networks. The basis of the IEEE 802.11 WLAN MAC protocol is a distributed coordination function (DCF), which is a carrier sense multiple access with collision avoidance (CSMA/CA) with a binary slotted exponential back-off scheme. Since IEEE 802.11 MAC has its own characteristics that are different from other wireless MAC protocols, the performance of reliable transport protocol over 802.11 needs further study. This paper proposes a scheme named DCF+, which is compatible with DCF, to enhance the performance of reliable transport protocol over WLAN. To analyze the performance of DCF and DCF+, this paper also introduces an analytical model to compute the saturated throughput of WLAN. Compared with other models, this model is shown to be able to predict the behavior of 802.11 more accurately. Moreover, DCF+ is able to improve the performance of TCP over WLAN, which is verified by modeling and elaborate simulation results.
864 citations
28 Aug 2005
TL;DR: This paper provides necessary conditions to verify the feasibility of rate vectors in next generation fixed wireless broadband networks, and uses them to derive upper bounds on the capacity in terms of achievable throughput, using a fast primal-dual algorithm.
Abstract: Next generation fixed wireless broadband networks are being increasingly deployed as mesh networks in order to provide and extend access to the internet. These networks are characterized by the use of multiple orthogonal channels and nodes with the ability to simultaneously communicate with many neighbors using multiple radios (interfaces) over orthogonal channels. Networks based on the IEEE 802.11a/b/g and 802.16 standards are examples of these systems. However, due to the limited number of available orthogonal channels, interference is still a factor in such networks. In this paper, we propose a network model that captures the key practical aspects of such systems and characterize the constraints binding their behavior. We provide necessary conditions to verify the feasibility of rate vectors in these networks, and use them to derive upper bounds on the capacity in terms of achievable throughput, using a fast primal-dual algorithm. We then develop two link channel assignment schemes, one static and the other dynamic, in order to derive lower bounds on the achievable throughput. We demonstrate through simulations that the dynamic link channel assignment scheme performs close to optimal on the average, while the static link channel assignment algorithm also performs very well. The methods proposed in this paper can be a valuable tool for network designers in planning network deployment and for optimizing different performance objectives.
825 citations
TL;DR: Analytically study the performance of the IEEE 802.11 protocol with a dynamically tuned backoff based on the estimation of the network status and results indicate that the capacity of the enhanced protocol approaches the theoretical limits in all the configurations analyzed.
Abstract: In WLANs, the medium access control (MAC) protocol is the main element that determines the efficiency of sharing the limited communication bandwidth of the wireless channel. The fraction of channel bandwidth used by successfully transmitted messages gives a good indication of the protocol efficiency, and its maximum value is referred to as protocol capacity. In a previous paper we have derived the theoretical limit of the IEEE 802.11 MAC protocol capacity. In addition, we showed that if a station has an exact knowledge of the network status, it is possible to tune its backoff algorithm to achieve a protocol capacity very close to its theoretical bound. Unfortunately, in a real case, a station does not have an exact knowledge of the network and load configurations (i.e., number of active stations and length of the message transmitted on the channel) but it can only estimate it. In this work we analytically study the performance of the IEEE 802.11 protocol with a dynamically tuned backoff based on the estimation of the network status. Results obtained indicate that under stationary traffic and network configurations (i.e., constant average message length and fixed number of active stations), the capacity of the enhanced protocol approaches the theoretical limits in all the configurations analyzed. In addition, by exploiting the analytical model, we investigate the protocol performance in transient conditions (i.e., when the number of active stations sharply changes).
554 citations
Cites background from "Dynamic tuning of the IEEE 802.11 p..."
...This procedure is repeated whenever an empty slot is detected on the channel....
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...In the next section we show how the Dynamic IEEE 802.11 protocol is implemented....
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...The analytical formulas for the other unknown quantities of (2) are defined in Lemma 1 whose proof can be found in [4] and [24]....
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...Hence, for a given network configuration (i.e., number of active stations,) and for a given traffic configuration (i.e. the value of that characterizes the average message length), is only a function of the value, and (with standard procedures) we can compute the value of, say , which minimizes the…...
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References
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TL;DR: Two protocols are described for CSMA and their throughput-delay characteristics are given and results show the large advantage CSMA provides as compared to the random ALOHA access modes.
Abstract: Radio communication is considered as a method for providing remote terminal access to computers. Digital byte streams from each terminal are partitioned into packets (blocks) and transmitted in a burst mode over a shared radio channel. When many terminals operate in this fashion, transmissions may conflict with and destroy each other. A means for controlling this is for the terminal to sense the presence of other transmissions; this leads to a new method for multiplexing in a packet radio environment: carrier sense multiple access (CSMA). Two protocols are described for CSMA and their throughput-delay characteristics are given. These results show the large advantage CSMA provides as compared to the random ALOHA access modes.
2,361 citations
TL;DR: The busy-tone multiple-access mode is introduced and analyzed as a natural extension of CSMA to eliminate the hidden-terminal problem and results show that BTMA with hidden terminals performs almost as well as CSMA without hidden terminals.
Abstract: We consider a population of terminals communicating with a central station over a packet-switched multiple-access radio channel. The performance of carrier sense multiple access (CSMA) [1] used as a method for multiplexing these terminals is highly dependent on the ability of each terminal to sense the carrier of any other transmission on the channel. Many situations exist in which some terminals are "hidden" from each other (either because they are out-of-sight or out-of-range). In this paper we show that the existence of hidden terminals significantly degrades the performance of CSMA. Furthermore, we introduce and analyze the busy-tone multiple-access (BTMA) mode as a natural extension of CSMA to eliminate the hidden-terminal problem. Numerical results giving the bandwidth utilization and packet delays are shown, illustrating that BTMA with hidden terminals performs almost as well as CSMA without hidden terminals.
1,754 citations
Book•
01 Jan 2000
TL;DR: TCP/IP Illustrated, Volume 1 is a complete and detailed guide to the entire TCP/IP protocol suite - with an important difference from other books on the subject: rather than just describing what the RFCs say the protocol suite should do, this unique book uses a popular diagnostic tool so you may actually watch the protocols in action.
Abstract: TCP/IP Illustrated, Volume 1 is a complete and detailed guide to the entire TCP/IP protocol suite - with an important difference from other books on the subject. Rather than just describing what the RFCs say the protocol suite should do, this unique book uses a popular diagnostic tool so you may actually watch the protocols in action.By forcing various conditions to occur - such as connection establishment, timeout and retransmission, and fragmentation - and then displaying the results, TCP/IP Illustrated gives you a much greater understanding of these concepts than words alone could provide. Whether you are new to TCP/IP or you have read other books on the subject, you will come away with an increased understanding of how and why TCP/IP works the way it does, as well as enhanced skill at developing aplications that run over TCP/IP.
1,384 citations
Additional excerpts
...9 is the recommended value [17]....
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TL;DR: The performance investigation reveals that an IEEE 802.11 network may be able to carry traffic with time-bounded requirements using the point coordination function, however, the findings suggest that packetized voice traffic must be handled in conjunction with an echo canceler.
Abstract: The draft IEEE 802.11 wireless local area network (WLAN) specification is approaching completion. In this article, the IEEE 802.11 protocol is explained, with particular emphasis on the medium access control sublayer. Performance results are provided for packetized data and a combination of packetized data and voice over the WLAN. Our performance investigation reveals that an IEEE 802.11 network may be able to carry traffic with time-bounded requirements using the point coordination function. However, our findings suggest that packetized voice traffic must be handled in conjunction with an echo canceler.
1,080 citations
Book•
01 Jan 1982
TL;DR: This course provides an introduction to the modeling and analysis of various random phenomena occurring in operations research and businesses such as inventory theory, queueing theory, genetics, demography, epidemiology, competing populations.
Abstract: Outline of the Course: This course provides an introduction to the modeling and analysis of various random phenomena occurring in operations research and businesses such as inventory theory, queueing theory, genetics, demography, epidemiology, competing populations. The course covers topics such as renewal processes, discrete and continuous time Markov chains and depending on time some extra topics from simulation, martingales and optimization of Markovian systems. The course also includes selected financial applications such as pricing and hedging with partial information, and stock selling problems.
1,069 citations
"Dynamic tuning of the IEEE 802.11 p..." refers methods in this paper
...To be more precise, we develop an analytical model to study the throughput of a -persistent IEEE 802.11 protocol....
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