Ad Hoc/Sensor Networking and Multihop WLANs May 2005 doc.: IEEE 802.11-05/0461r2 May 2005 Ad Hoc/Sensor Networking and Multihop WLANs Date: 2005-05-18 Authors: Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair <stuart.kerry@philips.com> as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at <patcom@ieee.org>. CH Yeh, Queen's University CH Yeh, Queen's University

May 2005 doc.: IEEE 802.11-05/0461r2 May 2005 Abstract This talk presents problems that will be introduced when current MAC protocols are applied to multihop networking, including mobile ad hoc networks, sensor networks, and multihop WLANs. We point out the issues to be addressed, current status for research and development, and incentives for deploying multihop networking. CH Yeh, Queen's University CH Yeh, Queen's University

Examples for Multihop Networks May 2005 Examples for Multihop Networks Ad hoc networks (MANET) Sensor networks Home networks with repeaters Mesh networks Multihop WLANs Others: Multihop cellular networks CH Yeh, Queen's University

Mobile Ad Hoc Networks (MANET) May 2005 Mobile Ad Hoc Networks (MANET) Mobile stations communicate with each other directly Absence of any predefined infrastructure High mobility possible Every node acts as a router Wireless Link Node CH Yeh, Queen's University

Wireless Sensor Networks May 2005 Wireless Sensor Networks Large number of small devices Static stations communicate with each other directly Sinks for gathering data Every relay node acts as a router Sink Sink CH Yeh, Queen's University

May 2005 Home Networks Intelligent appliances (IAs) communicate with access point (AP) directly or through a repeater IEEE 802.11 or ultrawideband (UWB) may be used CH Yeh, Queen's University

May 2005 Mesh Networking AP MP Mesh points (MPs) communicate with each other wirelessly Only some of the access points have wired connections to the Internet Every node also acts as a router CH Yeh, Queen's University

Multihop WLANs May 2005 Combining ad hoc networks and wireless LANs Mobile stations communicate with each other directly Packets are routed to APs to access the Internet Each participating node also acts as a router CH Yeh, Queen's University

Ad Hoc Cellular Networks May 2005 Ad Hoc Cellular Networks Combining ad hoc networks and cellular networks Mobile stations communicate with each other directly Packets are routed to APs to access the Internet Each participating node also acts as a router CH Yeh, Queen's University

Advantages for Multihop Networking May 2005 Advantages for Multihop Networking Ad hoc networks Infrastructureless Sensor networks Great commercial values WLAN Mesh Range extension with lower infrastructure cost Multihop WLAN/cellular networks Range extension without additional infrastructure Dead zone elimination/mitigation Lower power consumption Higher speed (due to shorter distance) Lower interference and better spatial reuse Higher throughput (potentially) CH Yeh, Queen's University

Why Commercial Ad Hoc Networking Has Not Happened May 2005 Why Commercial Ad Hoc Networking Has Not Happened Routing protocols were not standardized till 2004 The number of laptop computers did not reach a critical mass Lack of killer applications E.g., ad hoc networking in conference venues is replaced by WLAN coverage Poor performance (in ad hoc networking environments) based on current products Low throughput due to relaying Some problems remain unsolved Difficult configuration CH Yeh, Queen's University

New Driving Forces for Multihop Networking May 2005 New Driving Forces for Multihop Networking VOIP over WLAN 802.11 becoming available on smart phones Reaching critical mass Extended range is beneficial for WLAN access Energy efficiency is critical Proliferation of 802.11 hot spots Range extension = making more money Feasible with higher speeds and advanced technology National/muni WiFi to be deployed Range extension = infrastructure cost reduction Extending 802.11 to sensor networking Huge market CH Yeh, Queen's University

Problems with Current WLAN MAC in Multihop Networking Environments May 2005 Problems with Current WLAN MAC in Multihop Networking Environments High collision rate TCP and 802.11 in multihop networking environments Interference problems Interference-range hidden/exposed terminal problem Additive interference problem Problems associated with power control Heterogeneous hidden/exposed terminal problem Single-channel MAC difficult QoS and fairness problems Alternate blocking problems Fairness problems Exposed terminal problem CH Yeh, Queen's University

Interference-range Hidden/Exposed Terminal Problem May 2005 doc.: IEEE 802.11-05/0461r2 May 2005 Interference-range Hidden/Exposed Terminal Problem The interference range is typically larger than that of transmission range A potential transmitter D that cannot be reached by the CTS message of B may send a packet and collide with B’s reception A B D E (a) (b) (c) RTS CTS Data RLT also solves various other problems. Will be presented in Globecom’03 CH Yeh, Queen's University CH Yeh, Queen's University

Additive Interference Problem May 2005 doc.: IEEE 802.11-05/0461r2 May 2005 Additive Interference Problem A receiver is outside the interference radius of any other transmitters (except for its own transmitter), but the sum of nearby interference collide the reception anyway Relatively difficult to solve RLT also solves various other problems. Will be presented in Globecom’03 CH Yeh, Queen's University CH Yeh, Queen's University

Heterogeneous Terminal Problem May 2005 Heterogeneous Terminal Problem E D F C H CTS G B A CH Yeh, Queen's University

Alternate Blocking Problem May 2005 Alternate Blocking Problem CTS CTS A B C D E CH Yeh, Queen's University

Exposed Terminal Problem May 2005 Exposed Terminal Problem Data CTS Data CTS A B C D A B C D (b) (a) CH Yeh, Queen's University

Issues Needed to Be Addressed May 2005 Issues Needed to Be Addressed Resolving/mitigating aforementioned problems Routing Mobility Energy efficiency Security, privacy, and reliability Incorporating emerging technologies Applicability to sensor networks Cooperation from users Billing and Business model CH Yeh, Queen's University

Distinction from TGs May 2005 TGs focus on the following context: Residential networks Office networks Campus/public networks Safety/military networks Mesh points are different from laptops/smart phones/PDAs Infrastructure Power supply available Stationary in nature Single-hop networking from mobile stations (users) to mesh points Likely outcome Aiming at relatively smaller number of mesh points Likely based on infrastructure mode between mesh points Minimum/moderate changes to current MAC (esp. for mobile stations) Question: Evolve from TGs solutions or start a new effort? CH Yeh, Queen's University

Distinction from TG5 Current TG5 proposals May 2005 Distinction from TG5 Current TG5 proposals Synchronized MAC Hierarchical/clustered architecture Lower mobility than MANET Relatively smaller range Relatively lower speed Not applicable to 802.11 PHY CH Yeh, Queen's University

Current Status in Research and Development May 2005 doc.: IEEE 802.11-05/0461r2 May 2005 Current Status in Research and Development Four experimental routing protocol RFCs standardized by IETF Numerous ad hoc network testbeds in universities Some commercial products based on AODV, 802.11, and/or proprietary solutions Intensively researched in academia and industry Military applications for about 3-4 decades Renewed interests for about 1 decade Mainly focused on routing Problems well known Interesting techniques and solutions but some may be complex or even infeasible CH Yeh, Queen's University CH Yeh, Queen's University

Concluding Remarks Everything will be ad hoc in the future May 2005 Concluding Remarks Everything will be ad hoc in the future Multihop networking will be a norm, rather than an exception Time to look into multihop networking issues Emerging technologies should be incorporated CH Yeh, Queen's University

May 2005 References Sadeghi, B., “On hidden and exposed terminal problems,” IEEE 802.11-05/0065r0. Yeh, C.-H., “The advance access mechanism for differentiated service, power control, and radio efficiency in ad hoc MAC protocols,” Proc. IEEE VTC’03F, 2003. CH Yeh, Queen's University