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Proceedings ArticleDOI

Defending concealedness in IEEE 802.11n

TL;DR: The performance of the proposed opportunistic four-way access mechanism is evaluated in a practical 802.11n indoor mesh testbed, that shows a significant performance improvement compared to the standard access mechanisms.
Abstract: IEEE 802.11 distributed coordination function supports two access mechanisms - the basic access and the four-way access, both of which are vulnerable to the hidden and the exposed node problem (collectively called the concealed node problem). Though most of the works in literature suggest to overlook this problem due to the associated overhead to solve them, this paper shows that the problem becomes severe for high speed wireless mesh networks. An opportunistic four-way access mechanism is designed to defend this problem in IEEE 802.11n mesh networks that supports high data rates. The performance of the proposed scheme is evaluated in a practical 802.11n indoor mesh testbed, that shows a significant performance improvement compared to the standard access mechanisms.
Citations
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Journal ArticleDOI
TL;DR: The proposed approach uses the standard carrier sense multiple access (CSMA) technology along with an opportunistic collision avoidance (OCA) method that blocks the communication for hidden nodes and opportunistically allows exposed nodes to communicate with the peers.
Abstract: This paper proposes an opportunistic approach to mitigating the hidden and exposed node problem in a high-throughput mesh network, by exploiting the frame aggregation and block acknowledgment (BACK) capabilities of IEEE 802.11n/ac wireless networking standard. Hidden nodes significantly drop down the throughput of a wireless mesh network by increasing data loss due to collision, whereas exposed nodes cause under-utilization of the achievable network capacity. The problem becomes worse in IEEE 802.11n/ac supported high-throughput mesh networks, due to the large physical layer frame size and prolonged channel reservation from frame aggregation. The proposed approach uses the standard carrier sense multiple access (CSMA) technology along with an opportunistic collision avoidance (OCA) method that blocks the communication for hidden nodes and opportunistically allows exposed nodes to communicate with the peers. The performance of the proposed CSMA/OCA mechanism for high throughput mesh networks is studied using the results from an IEEE 802.11n+s wireless mesh networking testbed, and the scalability of the scheme has been analyzed using simulation results.

24 citations


Cites background from "Defending concealedness in IEEE 802..."

  • ...Our earlier paper [13] presents a theoretical model for the performance of IEEE 802....

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  • ...As shown in [13], reducing hidden nodes through a tunable CS threshold only is not sufficient to have a reasonable performance benefit in high throughput...

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References
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Journal ArticleDOI
TL;DR: In this paper, 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, is presented.
Abstract: 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 the distributed coordination function (DCF). The 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, we provide an extensive throughput performance evaluation of both access mechanisms of the 802.11 protocol.

8,072 citations

Proceedings ArticleDOI
01 Oct 1994
TL;DR: This paper studies media access protocols for a single channel wireless LAN being developed at Xerox Corporation's Palo Alto Research Center and develops a new protocol, MACAW, which uses an RTS-CTS-DS-DATA-ACK message exchange and includes a significantly different backoff algorithm.
Abstract: In recent years, a wide variety of mobile computing devices has emerged, including portables, palmtops, and personal digital assistants. Providing adequate network connectivity for these devices will require a new generation of wireless LAN technology. In this paper we study media access protocols for a single channel wireless LAN being developed at Xerox Corporation's Palo Alto Research Center. We start with the MACA media access protocol first proposed by Karn [9] and later refined by Biba [3] which uses an RTS-CTS-DATA packet exchange and binary exponential back-off. Using packet-level simulations, we examine various performance and design issues in such protocols. Our analysis leads to a new protocol, MACAW, which uses an RTS-CTS-DS-DATA-ACK message exchange and includes a significantly different backoff algorithm.

2,000 citations


Additional excerpts

  • ...…2014 07 January, 2014 2 / 20 Sandip Chakraborty (CSE, IITG) COMSNETS 2014 07 January, 2014 3 / 20 Two-way handshaking (Basic Access) Sandip Chakraborty (CSE, IITG) COMSNETS 2014 07 January, 2014 3 / 20 Two-way handshaking (Basic Access) A B C D E F Sandip Chakraborty (CSE, IITG) COMSNETS…...

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01 Jan 1999

488 citations

Journal ArticleDOI
TL;DR: The state of the art in WMN metrics is analyzed and a taxonomy for WMN routing protocols is proposed and performance measurements for a WMN, deployed using various routing metrics, are presented and corroborate the analysis.
Abstract: WMNs are low-cost access networks built on cooperative routing over a backbone composed of stationary wireless routers. WMNs must deal with the highly unstable wireless medium. Therefore, the design of algorithms that consider link quality to choose the best routes are enabling routing metrics and protocols to evolve. In this work, we analyze the state of the art in WMN metrics and propose a taxonomy for WMN routing protocols. Performance measurements for a WMN, deployed using various routing metrics, are presented and corroborate our analysis.

319 citations

Proceedings ArticleDOI
13 Jun 2005
TL;DR: It is concluded that, for the heterogeneous data rate environments, the RTS/CTS threshold should be redefined as a frame transmission time rather than as a frames size.
Abstract: IEEE 802.11 medium access control (MAC), called distributed coordination function (DCF), provides two different access modes, namely, 2-way (basic access) and 4-way (RTS/CTS) handshaking. The 4-way handshaking has been introduced in order to combat the hidden terminal phenomenon. It has been also proved that such a mechanism can be beneficial even in the absence of hidden terminals, because of the collision time reduction. We analyze the effectiveness of the RTS/CTS access mode, in current 802.11b and 802.11a networks. Since the rates employed for control frame transmissions can be much lower than the rate employed for data frames, the assumption on the basis of the 4-way handshaking introduction, i.e., a short transmission time for the RTS control frame, is no longer valid. As a consequence, the basic access mode results in the optimal access solution in most cases, even in heavy load conditions with hidden nodes. We compare the 2-way and 4-way access performances through both analytical and simulation tools. We also discuss the operating conditions at which the switch from one access mode to another is desired for the cases of uniform and heterogeneous data rates among the stations. We conclude that, for the heterogeneous data rate environments, the RTS/CTS threshold should be redefined as a frame transmission time rather than as a frame size.

53 citations


"Defending concealedness in IEEE 802..." refers background in this paper

  • ...For, IEEE 802.11b/g networks, solutions of hidden and exposed nodes require extra controlling overhead, which severe for a low to moderate loaded network....

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