An Asymmetric Access Point for Solving the Unfairness Problem in WLANs

In atypical deployment of IEEE 802.11 wireless LANs in the infrastructure mode, an access point acts as abridge between the wireless and the wired parts of the network. Under the current IEEE 802.11 Distributed Coordination Function (DCF) access method, which provides equal channel access probability to all devices in a cell, the access point cannot relay all the frames that it receives on the downlink. This causes significant unfairness between upload and download connections, long delays, and frame losses. This unfairness problem comes from the not-so-complex interaction of transport-layer protocols with the MAC-layer access method. The main problem is that the access point requires more transmission attempt probability than wireless stations for correct operation at the transport layer. In this paper, we propose to solve the unfairness problem in a simple elegant way at the MAC layer. We define the operation of an Asymmetric Access Point that benefits from a sufficient transmission capacity with respect to wireless stations so that the overall performance improves. The proposed method of operation is intrinsically adaptive so that when the access point does not need the increased capacity, it is used by wireless stations. We validate the proposed access method by simulation to compare it with other solutions based on IEEE 802.11e. Unlike many papers in this domain, which only validate MAC-layer modifications through simulation or analytical modeling, we provide measurement data gathered on an experimental prototype that uses wireless cards implementing the proposed method.

[1]  Scott Shenker,et al.  Observations on the dynamics of a congestion control algorithm: the effects of two-way traffic , 1991, SIGCOMM 1991.

[2]  Carla-Fabiana Chiasserini,et al.  Smart traffic scheduling in 802.11 WLANs with access point , 2003, 2003 IEEE 58th Vehicular Technology Conference. VTC 2003-Fall (IEEE Cat. No.03CH37484).

[3]  Albert Banchs,et al.  Distributed weighted fair queuing in 802.11 wireless LAN , 2002, 2002 IEEE International Conference on Communications. Conference Proceedings. ICC 2002 (Cat. No.02CH37333).

[4]  A. Girotra,et al.  Performance Analysis of the IEEE 802 . 11 Distributed Coordination Function , 2005 .

[5]  Peter Steenkiste,et al.  Effort-limited fair (ELF) scheduling for wireless networks , 2000, Proceedings IEEE INFOCOM 2000. Conference on Computer Communications. Nineteenth Annual Joint Conference of the IEEE Computer and Communications Societies (Cat. No.00CH37064).

[6]  Xiaowen Wang,et al.  Performance enhancement of 802.11 wireless LAN for asymmetric traffic using an adaptive MAC layer protocol , 2002, Proceedings IEEE 56th Vehicular Technology Conference.

[7]  Scott Shenker,et al.  Some observations on the dynamics of a congestion control algorithm , 1990, CCRV.

[8]  Lyndon Ong,et al.  An Introduction to the Stream Control Transmission Protocol (SCTP) , 2002, RFC.

[9]  Srinivasan Seshan,et al.  Efficient TCP over networks with wireless links , 1995, Proceedings 5th Workshop on Hot Topics in Operating Systems (HotOS-V).

[10]  Vasilios A. Siris,et al.  Optimal CWmin selection for achieving proportional fairness in multi-rate 802.11e WLANs: test-bed implementation and evaluation , 2006, WINTECH.

[11]  Paramvir Bahl,et al.  Characterizing user behavior and network performance in a public wireless LAN , 2002, SIGMETRICS '02.

[12]  Prasun Sinha,et al.  Understanding TCP fairness over wireless LAN , 2003, IEEE INFOCOM 2003. Twenty-second Annual Joint Conference of the IEEE Computer and Communications Societies (IEEE Cat. No.03CH37428).

[13]  Martin Heusse,et al.  Performance anomaly of 802.11b , 2003, IEEE INFOCOM 2003. Twenty-second Annual Joint Conference of the IEEE Computer and Communications Societies (IEEE Cat. No.03CH37428).

[14]  Raj Jain,et al.  Analysis of the Increase and Decrease Algorithms for Congestion Avoidance in Computer Networks , 1989, Comput. Networks.

[15]  Ilenia Tinnirello,et al.  Kalman filter estimation of the number of competing terminals in an IEEE 802.11 network , 2003, IEEE INFOCOM 2003. Twenty-second Annual Joint Conference of the IEEE Computer and Communications Societies (IEEE Cat. No.03CH37428).

[16]  Scott Shenker,et al.  Observations on the dynamics of a congestion control algorithm: the effects of two-way traffic , 1991, SIGCOMM '91.

[17]  Douglas J. Leith,et al.  Using the 802.11e EDCF to achieve TCP upload fairness over WLAN links , 2005, Third International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt'05).

[18]  A. Salkintzis,et al.  Support of IP QoS over wireless LANs , 2004, 2004 IEEE 59th Vehicular Technology Conference. VTC 2004-Spring (IEEE Cat. No.04CH37514).

[19]  Andrzej Duda,et al.  Idle sense: an optimal access method for high throughput and fairness in rate diverse wireless LANs , 2005, SIGCOMM '05.

[20]  Marco Conti,et al.  Design of an enhanced access point to optimize TCP performance in Wi-Fi hotspot networks , 2007, Wirel. Networks.

[21]  A. M. Abdullah,et al.  Wireless lan medium access control (mac) and physical layer (phy) specifications , 1997 .

[22]  R. Srikant,et al.  Fair scheduling in wireless packet networks , 1999, TNET.

[23]  Theodore S. Rappaport,et al.  Measured Traffic Statistics and Throughput of IEEE 802.11b Public WLAN Hotspots with Three Different Applications , 2006, IEEE Transactions on Wireless Communications.

[24]  Haitao Wu,et al.  Performance of reliable transport protocol over IEEE 802.11 wireless LAN: analysis and enhancement , 2002, Proceedings.Twenty-First Annual Joint Conference of the IEEE Computer and Communications Societies.

[25]  Ravi Prakash,et al.  Service differentiation mechanisms for IEEE 802.11-based wireless networks , 2004, 2004 IEEE Wireless Communications and Networking Conference (IEEE Cat. No.04TH8733).

[26]  David Malone,et al.  TCP fairness in 802.11e WLANs , 2005, 2005 International Conference on Wireless Networks, Communications and Mobile Computing.

[27]  Jordi Casademont,et al.  Outdoor IEEE 802.11g cellular network performance , 2004, IEEE Global Telecommunications Conference, 2004. GLOBECOM '04..

[28]  Yan Grunenberger,et al.  Experience with an implementation of the Idle Sense wireless access method , 2007, CoNEXT '07.

[29]  Arturo Azcorra,et al.  Applications and challenges of the 802.11e EDCA mechanism: an experimental study , 2005, IEEE Network.

[30]  L. Sanchez,et al.  An experimental study of Snoop TCP performance over the IEEE 802.11b WLAN , 2002, The 5th International Symposium on Wireless Personal Multimedia Communications.

[31]  Mark Handley,et al.  Datagram Congestion Control Protocol (DCCP) , 2006, RFC.

[32]  Kai Xu,et al.  Improving TCP performance in integrated wireless communications networks , 2005, Comput. Networks.

[33]  Henning Schulzrinne,et al.  Balancing uplink and downlink delay of VoIP traffic in WLANs using Adaptive Priority Control (APC) , 2006, QShine '06.

[34]  Chong-Ho Choi,et al.  WLC29-5: TCP Fairness for Uplink and Downlink Flows in WLANs , 2006, IEEE Globecom 2006.

[35]  Martin Heusse,et al.  WLC29-2: Performance of Wireless LAN Access Methods in Multicell Environments , 2006, IEEE Globecom 2006.

[36]  Paramvir Bahl,et al.  Distributed fair scheduling in a wireless LAN , 2000, IEEE Transactions on Mobile Computing.

[37]  Martin Heusse,et al.  Bandwidth allocation for DiffServ based quality of service over 802.11 , 2003, GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489).

[38]  H. Balakrishnan,et al.  How network asymmetry affects TCP , 2001, IEEE Communications Magazine.