‘Shield’: Protecting High-Priority Channel Access Attempts

Slides:



Advertisements
Similar presentations
IEEE CSMA/CA DCF CSE 6590 Fall /7/20141.
Advertisements

Contents IEEE MAC layer operation Basic CSMA/CA operation
Lecture 5: IEEE Wireless LANs (Cont.). Mobile Communication Technology according to IEEE (examples) Local wireless networks WLAN a.
14.1 Chapter 14 Wireless LANs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1 QoS Schemes for IEEE Wireless LAN – An Evaluation by Anders Lindgren, Andreas Almquist and Olov Schelen Presented by Tony Sung, 10 th Feburary.
110/15/2003CS211 IEEE Standard Why we study this standard: overall architecture physical layer spec. –direct sequence –frequency hopping MAC layer.
CS640: Introduction to Computer Networks Aditya Akella Lecture 22 - Wireless Networking.
Lecture #2 Chapter 14 Wireless LANs.
Opersating Mode DCF: distributed coordination function
MAC layer Taekyoung Kwon. Media access in wireless - start with IEEE In wired link, –Carrier Sense Multiple Access with Collision Detection –send.
IEEE Project started by IEEE for setting standard for LAN. This project started in (1980, February), Name given to project is year and month.
Ethernet. Problem In an Ethernet, suppose there are three stations very close to each other, A, B and C. Suppose at time 0, all of them have a frame to.
Computer and Data Communications Semester Mohd Nazri Mahmud Session 4a-12 March 2012.
IEEE Wireless LAN Standard. Medium Access Control-CSMA/CA IEEE defines two MAC sublayers Distributed coordination function (DCF) Point coordination.
Submission doc.: IEEE /569r1 November 2001 M. Benveniste -- AT&T Labs, ResearchSlide 1 An Access Mechanism for Periodic Contention-Free Sessions.
Doc.: IEEE /0840r1 Submission AP Assisted Medium Synchronization Date: Authors: September 2012 Minyoung Park, Intel Corp.Slide 1.
Chapter 6 Medium Access Control Protocols and Local Area Networks Wireless LAN.
Wi-Fi. Basic structure: – Stations plus an access point – Stations talk to the access point, then to outside – Access point talks to stations – Stations.
WLAN. Networks: Wireless LANs2 Distribute Coordination Function (DCF) Distributed access protocol Contention-Based Uses CSMA/ CA – Uses both physical.
MAC Sublayer MAC layer tasks: – Control medium access – Roaming, authentication, power conservation Traffic services – DCF (Distributed Coordination.
Wireless Protocols. 2 Outline MACA 3 ISM: Industry, Science, Medicine unlicensed frequency spectrum: 900Mhz, 2.4Ghz, 5.1Ghz, 5.7Ghz.
Doc.: IEEE /171 Submission July 2001 Mathilde Benveniste, AT&T Labs - ResearchSlide 1 HCF Access through Tiered Contention Mathilde Benveniste.
Doc.: IEEE /457 Submission December 2000 Mathilde Benveniste, AT&T Labs - ResearchSlide 1 An Enhanced-DCF Proposal Based on ‘Tiered Contention’
MAC Layer Protocols for Wireless Networks. What is MAC? MAC stands for Media Access Control. A MAC layer protocol is the protocol that controls access.
MAC for WLAN Doug Young Suh Last update : Aug 1, 2009 WLAN DCF PCF.
Design and Implementation of a Reservation-based MAC Protocol for Voice/Data over IEEE Ad-Hoc Wireless Networks Shiann-Tsong Sheu, Tzu-Fang Sheu.
Submission doc.: IEEE /599r1 November 2001 M. Benveniste -- AT&T Labs, ResearchSlide 1 ‘Cyclic Prioritized Multiple Access (CPMA): An Access Mechanism.
DSSS PHY packet format Synchronization SFD (Start Frame Delimiter)
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties. Wireless LANs Session
Submission doc.: IEEE /596r1 November 2001 M. Benveniste -- AT&T Labs, ResearchSlide 1 ‘Neighborhood Capture’ in Wireless LANs Mathilde Benveniste.
Doc.: IEEE /145r1 Submission March 2001 Mathilde Benveniste, AT&T Labs - ResearchSlide 1 E-DCF with Backoff Adaptation to Traffic Mathilde Benveniste.
Doc.: IEEE /110 Submission May 2000 Sunghyun Choi, Philips ResearchSlide 1 QoS Support in : Contention-Free MAC Perspective Sunghyun Choi.
AIFS – Revisited Mathilde Benveniste
Wireless MAC.
EA C451 (Internetworking Technologies)
Medium Access Control MAC protocols: design goals, challenges,
Computer Communication Networks
Topics in Distributed Wireless Medium Access Control
Lecture 27 WLAN Part II Dr. Ghalib A. Shah
An Access Mechanism for Periodic Contention-Free Sessions
IEEE : Wireless LANs ALOHA, Slotted ALOHA
Chapter 2 Wireless LANS and PANS
CS 457 – Lecture 7 Wireless Networks
Computer Communication & Networks
IEEE Wireless LAN wireless LANs: untethered (often mobile) networking
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Proposal for Collaborative BT and b MAC Mechanisms.
Neighborhood Capture and OBSS
AIFS – Revisited Mathilde Benveniste
Overlapping coverage issues with n BSSs
Specification overview
Chapter 6 Medium Access Control Protocols and Local Area Networks
Introduction to Wireless Networks
Specification overview
EDCA Backoff Rules Mathilde Benveniste
Ethernet – CSMA/CD Review
Performance Evaluation of an Integrated-service IEEE Network
Overlapping BSS Co-Existence
MAC continued.
Wireless LAN Simulation IEEE MAC Protocol
E-DCF with Backoff Adaptation to Traffic
HCF Channel Access And Inter-BSS Channel Sharing
HCF medium access rules
Overlapping coverage issues with n BSSs
Neighborhood Capture and OBSS
of the IEEE Distributed Coordination Function
VTS Robust Multicast/Broadcast Protocol
Outdoor Mesh MAC Protocol Issues & Considerations
HCF Channel Access And Inter-BSS Channel Sharing
Enhanced Backoff Scheme in CSMA/CA for IEEE
Dr. John P. Abraham Professor UTPA
Presentation transcript:

‘Shield’: Protecting High-Priority Channel Access Attempts doc.: IEEE 802.11-00/457 November 2001 November 2001 ‘Shield’: Protecting High-Priority Channel Access Attempts Mathilde Benveniste AT&T Labs, Research M. Benveniste -- AT&T Labs, Research

CFS and PCFS: Definitions November 2001 CFS and PCFS: Definitions Definitions Contention free session (CFS) Any frame exchange sequence that may occur without contention following a successful channel access attempt. A CFS may involve one or more stations. A CFS may be initiated by any station. A Contention-Free Burst and an RTS/CTS exchange are both examples of a CFS Periodic contention free period (PCFS) A CFS that must occur at regular time intervals. A Contention-Free Period is an example of a PCFS M. Benveniste -- AT&T Labs, Research

CFS and PCFS: Definitions November 2001 CFS and PCFS: Definitions Definitions Contention free session (CFS) Any frame exchange sequence that may occur without contention following a successful channel access attempt. A CFS may involve one or more stations. A CFS may be initiated by any station. A Contention-Free Burst and an RTS/CTS exchange are both examples of a CFS Periodic contention free period (PCFS) A CFS that must occur at regular time intervals. A Contention-Free Period is an example of a PCFS CFS/PCFS origin For simplicity, but without loss of generality, we assume that CFSs/PCFSs are initiated by APs only M. Benveniste -- AT&T Labs, Research

November 2001 Overview This is one of 5 independent submissions relating to HCF access and OBSS mitigation. These are: (1) CPMA: An Access Mechanism for Contention-Free Sessions CPMA a protocol for prioritized contention-based access (2) An access mechanism for Periodic Contention-Free Sessions Regularly spaced sessions (3) ‘Shield’: Protecting High-Priority Channel Access Attempts  Prevents CFS/PCFS corruption in case of collision with an (E)STA (4) ‘Neighborhood capture’ in wireless LANs Preventing a capture effect (5) HCF Access Mechanisms: Inter-BSS NAV protection Virtual carrier sense for CFS/PCFSs M. Benveniste -- AT&T Labs, Research

Channel Access for CFSs/PCFSs November 2001 A CFS may collide with (E)DCF transmissions if there are idle gaps longer than PIFS following a transmission Such gaps occur in CPMA: if an AP retires; or at the head of sequence of contiguous CFSs all HCF access methods using random backoff CFS structure protects a CFS in case of a collision with an (E)DCF transmission the CFS is delayed for subsequent transmission, interference-free the channel is reserved by causing a break in the current idle, if one exists M. Benveniste -- AT&T Labs, Research

‘Shield’ - Protection from collision with DCF txs November 2001 ‘Shield’ - Protection from collision with DCF txs DIFS CFS body PIFS AP starts a CFS after its backoff expires Busy channel CFS Shield A CFS is started with a short frame (e.g., PLCP header without MAC data) -- the ‘shield’ The AP will wait for an idle period of PIFS to transmit following the shield If an (E) DCF transmission collides with the shield, the AP will hear the transmission and defer initiation of the CFS body After completion of the (E)DCF transmission, the CFS will start - following a PIFS idle Transmission of the shield before the CFS body is not needed always Not needed if AP knows that the idle gap between the CFS and the previous transmission is equal to PIFS; i.e., when the backoff delay is 1, during the last busy period The algorithms presented here can be combined with a variety of schemes for RF resource allocation. An example is illustrated above. Three channels are available in each cell, each allocated to one of three antenna faces (i.e. to one logical cell each). If all the logical cells to which a channel is allocated transmit simultaneously on that channel, the quality of transmission would be inadequate. In order to increase the signal-to-interference ratio, each frame on the channel must be apportioned so that the different co-channel logical cells use different parts of the frame. In this example, the problem reduces to bandwidth allocation of a single channel among potentially interfering BSSs. We consider only the APs that are allowed to use the same channel. We wish to allocate a portion of each frame of the channel among the logical cells. M. Benveniste -- AT&T Labs, Research

Sample CFS structure November 2001 CFS cycle CFS body PIFS S I F S S I F S S I F S P I F S Other CFSs and Contention Period D 1 + p o l l D2+ack+poll D 3 + a c k D4+poll + p o l U 1 + a c k U2+ack U4+ack Beacon D I F S Shield N o S I F S S I F r e s p o n s e S I F t o C F - P o l l N A V CFS_Max_Duration F M. Benveniste -- AT&T Labs, Research

Benefit of the ‘shield’ November 2001 Benefit of the ‘shield’ Any (E)DCF transmissions colliding with the ‘shield’ will cause postponement of the start of the CFS body until the channel is clear The CFS is thus assured of no (E)DCF conflict because of its shorter AIFS While the colliding (E)DCF transmission is unsuccessful, the CFS body will be transmitted without conflict Channel time is saved this way if CFSs are longer than DCF transmissions This method can be applied also to PCFSs if there is no other mechanism to protect them from collisions with (E)DCF transmissions, as there is in PCF A special ‘shield’ may also be used in Inter-BSS NAV protection M. Benveniste -- AT&T Labs, Research