Results 1 - 10
of
445
Performance Analysis of the IEEE 802.11 Distributed Coordination Function
, 2000
"... Recently, the IEEE has standardized the 802.11 protocol for Wireless Local Area Networks. The primary medium access control (MAC) technique of 802.11 is called distributed coordination function (DCF). DCF is a carrier sense multiple access with collision avoidance (CSMA/CA) scheme with binary slott ..."
Abstract
-
Cited by 1869 (1 self)
- Add to MetaCart
Recently, the IEEE has standardized the 802.11 protocol for Wireless Local Area Networks. The primary medium access control (MAC) technique of 802.11 is called distributed coordination function (DCF). DCF is a carrier sense multiple access with collision avoidance (CSMA/CA) scheme with binary slotted exponential backoff. This paper provides a simple, but nevertheless extremely accurate, analytical model to compute the 802.11 DCF throughput, in the assumption of finite number of terminals and ideal channel conditions. The proposed analysis applies to both the packet transmission schemes employed by DCF, namely, the basic access and the RTS/CTS access mechanisms. In addition, it also applies to a combination of the two schemes, in which packets longer than a given threshold are transmitted according to the RTS/CTS mechanism. By means of the proposed model, in this paper we provide an extensive throughput performance evaluation of both access mechanisms of the 802.11 protocol.
Wireless mesh networks: a survey
- COMPUTER NETWORKS
, 2005
"... Wireless meshnet8Ex8 (WMNs)consist of meshrout6L and meshclient8 where meshroutfix have minimal mobilit and formtr backbone of WMNs. They provide netide access for bot mesh andconvent1)fi8 clientt TheintL gratLfl of WMNs wit ot8 net8866 such as t1Int6fiPx1 cellular, IEEE 802.11, IEEE 802.15, IEEE 8 ..."
Abstract
-
Cited by 687 (12 self)
- Add to MetaCart
Wireless meshnet8Ex8 (WMNs)consist of meshrout6L and meshclient8 where meshroutfix have minimal mobilit and formtr backbone of WMNs. They provide netide access for bot mesh andconvent1)fi8 clientt TheintL gratLfl of WMNs wit ot8 net8866 such as t1Int6fiPx1 cellular, IEEE 802.11, IEEE 802.15, IEEE 802.16, sensor netsor1L ets can be accomplishedtccomp tc gatomp and bridging functng1 in t1 meshroutfijx Meshclient can be eit8fi st8fij1)6x or mobile, and can form aclient meshnet16S amongtng1fifiELj and wit meshroutLfifi WMNs are antLfifl1)6fl t resolvets limit18fiflfl andt significantfl improvetp performance of ad hocnetLEP8L wireless local area net1Pxx (WLANs), wireless personal areanet16fij (WPANs), and wirelessmetess1fifljfl areanet1LPS (WMANs). They are undergoing rapid progress and inspiring numerousdeploymentS WMNs will deliver wireless services for a largevariet ofapplicat6fifl in personal, local, campus, andmet8Lfix1)6fi areas. Despit recent advances in wireless mesh netjLfiP1)6 many research challenges remain in allprotjfiS layers. This paperpresent adetEfl81 stEonrecent advances and open research issues in WMNs. Syst1 architL881)6 andapplicat)68 of WMNs are described, followed by discussingts critssi factss influencingprotenc design.Theoret8fiL netore capacit and tdst1LLSjx tt1LL protLLSj for WMNs are exploredwit anobjectE1 t point out a number of open research issues. Finally,tnal beds,indust681 pract68 andcurrent strent actntx1) relatt t WMNs arehighlight8x # 2004 Elsevier B.V. Allrl rl KedI7-8 Wireless meshnet186flfl Ad hocnet8jEES Wireless sensornetor16fl Medium accessconts1fi Routs1 prots1fiS Transport protspor ScalabilitS Securiti Powermanagement andcontfi8fl Timingsynchronizat ion 1389-1286/$ - seefront matt # 2004 Elsevier B.V. Allright reserved. doi:10....
Mobile ad hoc networking: imperatives and challenges
, 2003
"... 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-exi ..."
Abstract
-
Cited by 317 (8 self)
- Add to MetaCart
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 MANET's characteristics, capabilities, applications, and design constraints. The paper concludes by presenting a set of challenges and problems requiring further research in the future.
Characterizing the capacity region in multi-radio multi-channel wireless mesh networks
- in ACM MobiCom
, 2005
"... 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 nei ..."
Abstract
-
Cited by 244 (0 self)
- Add to MetaCart
(Show Context)
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.
Performance of Reliable Transport Protocol over IEEE 802.11 Wireless LAN: Analysis And Enhancement
, 2002
"... EEE 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 Distributed Coordination Function(DCF), which is a Carrier Sense Multiple Access with Col ..."
Abstract
-
Cited by 226 (3 self)
- Add to MetaCart
EEE 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 Distributed Coordination Function(DCF), which is a Carrier Sense Multiple Access with Collision Avoidance(CSMA/CA) with 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.
Modeling per-flow throughput and capturing starvation in CSMA multi-hop wireless networks
- In Proc. of IEEE Infocom
, 2006
"... Abstract — Multi-hop wireless networks employing random access protocols have been shown to incur large discrepancies in the throughputs achieved by the flows sharing the network. Indeed, flow throughputs can span orders of magnitude from near starvation to many times greater than the mean. In this ..."
Abstract
-
Cited by 159 (18 self)
- Add to MetaCart
(Show Context)
Abstract — Multi-hop wireless networks employing random access protocols have been shown to incur large discrepancies in the throughputs achieved by the flows sharing the network. Indeed, flow throughputs can span orders of magnitude from near starvation to many times greater than the mean. In this paper, we address the foundations of this disparity. We show that the fundamental cause is not merely differences in the number of contending neighbors, but a generic coordination problem of CSMA-based random access in a multi-hop environment. We develop a new analytical model that incorporates this lack of coordination, identifies dominating and starving flows and accurately predicts per-flow throughput in a large-scale network. We then propose metrics that quantify throughput imbalances due to the MAC protocol operation. Our model and metrics provide a deeper understanding of the behavior of CSMA protocols in arbitrary topologies and can aid the design of effective protocol solutions to the starvation problem. I.
IEEE 802.11 Protocol: Design and Performance Evaluation of an Adaptive Backoff Mechanism
, 2000
"... 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 ..."
Abstract
-
Cited by 126 (2 self)
- Add to MetaCart
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).
MiSer: An Optimal Low-Energy Transmission Strategy for IEEE 802.11 a/h.
, 2003
"... Abstract Reducing the energy consumption by wireless communication devices is perhaps the most important issue in the widely-deployed and exponentially-growing IEEE 802.11 Wireless LANs (WLANs). TPC (Transmit Power Control) and PHY (physical layer) rate adaptation have been recognized as two most e ..."
Abstract
-
Cited by 99 (5 self)
- Add to MetaCart
(Show Context)
Abstract Reducing the energy consumption by wireless communication devices is perhaps the most important issue in the widely-deployed and exponentially-growing IEEE 802.11 Wireless LANs (WLANs). TPC (Transmit Power Control) and PHY (physical layer) rate adaptation have been recognized as two most effective ways to achieve this goal. The emerging 802.11h standard, which is an extension to the current 802.11 MAC and the high-speed 802.11a PHY, will provide a structured means to support intelligent TPC. In this paper, we propose a novel scheme, called MiSer, that minimizes the communication energy consumption in 802.11a/h systems by combining TPC with PHY rate adaptation. The key idea is to compute offline an optimal rate-power combination table, and then at runtime, a wireless station determines the most energyefficient transmission strategy for each data frame by a simple table lookup. Another key contribution of this paper is to provide a rigorous analysis of the relation among different radio ranges and TPC's effect on the interference in 802.11a/h systems, which justifies MiSer's approach to ameliorating the TPC-caused interference by transmitting the CTS frames at a stronger power level. Our simulation results show that MiSer delivers about 20% more data per unit of energy consumption than the PHY rate adaptation scheme without TPC, while outperforming single-rate TPC schemes significantly thanks to the excellent energy-saving capability of PHY rate adaptation.
Sift: A MAC Protocol for Event-Driven Wireless Sensor Networks
, 2003
"... Nodes in sensor networks often encounter spatially-correlated contention, where multiple nodes in the same neighborhood all sense an event they need to transmit information about. Furthermore, in many sensor network applications, it is sufficient if a subset of the nodes that observe the same even ..."
Abstract
-
Cited by 90 (1 self)
- Add to MetaCart
Nodes in sensor networks often encounter spatially-correlated contention, where multiple nodes in the same neighborhood all sense an event they need to transmit information about. Furthermore, in many sensor network applications, it is sufficient if a subset of the nodes that observe the same event report it. We show that traditional carrier-sense multiple access (CSMA) protocols like 802.11 do not handle the first constraint adequately, and do not take advantage of the second property, leading to degraded latency and throughput as the network scales in size.
A Scalable Model for Channel Access Protocols in Multihop Ad Hoc Networks
, 2004
"... A new modeling framework is introduced for the analytical study of medium access control (MAC) protocols operating in multihop ad hoc networks. The model takes into account the e#ect of physical-layer parameters on the success of transmissions, the MAC protocol on the likelihood that nodes can acces ..."
Abstract
-
Cited by 84 (6 self)
- Add to MetaCart
(Show Context)
A new modeling framework is introduced for the analytical study of medium access control (MAC) protocols operating in multihop ad hoc networks. The model takes into account the e#ect of physical-layer parameters on the success of transmissions, the MAC protocol on the likelihood that nodes can access the channnel, and the connectivity of nodes in the network. A key feature of the model is that nodes can be modeled individually, i.e., it allows a per-node setup of many layer-specific parameters. Moreover, no spatial probability distribution or a particular arrangement of nodes is assumed; the model allows the computation of individual (per-node) performance metrics for any given network topology and radio channel model. To show the applicability of the modeling framework, we model multihop ad hoc networks using the IEEE 802.11 distributed coordination function and validate the results from the model with discreteevent simulations in Qualnet. The results show that our model predicts results that are very close to those attained by simulations, and requires seconds to complete compared to several hours of simulation time.