Self-Organizing Neighborhood Wireless Mesh Networks
Researchers in Microsoft Research Redmond, Cambridge, and Silicon Valley are working
to create wireless technologies that allow neighbors to connect
their home networks together. There are many advantages to enabling such connectivity
and forming a community mesh network. For example, when enough neighbors cooperate
and forward each others packets, they do not need to individually install an
Internet "tap" (gateway) but instead can share faster,
cost-effective Internet access via gateways that are distributed in their
neighborhood. Packets dynamically find a route, hopping from one neighbor's
node to another to reach the Internet through one of these gateways. Another
advantage is that neighbors can cooperatively deploy backup technology and
never have to worry about losing information due to a catastrophic disk
failure. A third advantage is that this technology allows bits created locally
to be used locally without having to go through a service provider and the
Internet. Neighborhood community networks allow faster and easier dissemination
of cached information that is relevant to the local community.
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Community-based multi-hop wireless networks is disruptive to the current broadband
Internet access paradigm, which relies on cable and DSL being
deployed in individual homes. It is important because it allows
free flow of information without any moderation or selective rate
control. Compared to the large DSL and cable modem systems that
are centrally managed, mesh networking is organic in nature -- everyone in the neighborhood contributes network resources and
cooperates.
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However, to realize the
community-based goal, one has to solve many challenging problems including;
capacity and range enhancement, privacy and security, self-stablizing and
multi-path multi-hop routing, auto-configuration, bandwidth fairness, etc.
In addition to solving the tough problems, success also depends on
spectrum etiquette, business models, and economics. We are investigating
some of the fundamental technical problems that continue to remain
challenging despite several decades of research in packet radio networks.
We have deployed testbed networks in our office buildings and in a local
apartment complex.
We implement ad-hoc routing and link quality measurement in a module
that we call the Mesh Connectivity Layer (MCL). Architecturally, MCL
is a loadable Microsoft Windows driver. It implements a virtual network adapter,
so that to the rest of the system the ad-hoc network appears as an
additional (virtual) network link. MCL routes using a modified
version of DSR (an IETF protocol) that we call Link Quality Source
Routing (LQSR). We have modified DSR extensively to improve its
behavior, most significantly to support link quality metrics.
The MCL driver implements an interposition layer between layer 2 (the
link layer) and layer 3 (the network layer). To higher layer software,
MCL appears to be just another Ethernet link, albeit a virtual
link. To lower layer software, MCL appears to be just another protocol
running over the physical link.
This design has several significant advantages. First, higher layer
software runs unmodified over the ad-hoc network. In our testbeds, we
run both IPv4 and IPv6 over the ad-hoc network. No modifications to
either network stack were required. Network layer functionality (for
example ARP, DHCP, and Neighbor Discovery) just works. Second, the
ad-hoc routing runs over heterogeneous link layers. Our current
implementation supports Ethernet-like physical link layers (e.g. 802.11
and 802.3) but the architecture accommodates link layers with
arbitrary addressing and framing conventions. The virtual MCL network
adapter can multiplex several physical network adapters, so the ad-hoc
network can extend across heterogeneous physical links. Third, the
design can support other ad-hoc routing protocols as well.
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Collaborators
- Researchers from Microsoft Research Redmond, Microsoft Research Cambridge,
and Microsoft Research Silicon Valley.
- As an intern, Yih-Chun Hu implemented DSR
within the MCL framework;
this was our starting point for developing LQSR.
Publications
- A. Adya, P. Bahl, R. Chandra, and L. Qiu.
Architecture and Techniques for Diagnosing Faults in IEEE 802.11 Infrastructure Networks.
To appear in Mobicom 2004.
- R. Draves, J. Padhye, and B. Zill.
Routing in Multi-radio, Multi-hop Wireless Mesh Networks.
A revised version will appear in Mobicom 2004.
- P. Bahl, R. Chandra, and J. Dunagan.
SSCH: Slotted Seeded Channel Hopping for Capacity Improvement in IEEE 802.11 Ad-Hoc Wireless Networks.
A revised version will appear in Mobicom 2004.
- R. Draves, J. Padhye, and B. Zill.
Comparison of Routing Metrics for Static Multi-Hop Wireless Networks.
ACM SIGCOMM, Portland, OR, August 2004.
- L. Qiu, P. Bahl, A. Rao, and L. Zhou.
Fault Detection, Isolation, and Diagnosis in Multi-hop Wireless Networks.
Microsoft Technical Report, Microsoft Research-TR-2004-11, December 2003.
(pdf, 320 Kbytes)
- K. Jain, J. Padhye, V. Padmanabhan, and L. Qiu.
Impact of Interference on Multi-hop Wireless Network Performance.
ACM Mobicom, San Diego, CA, September 2003.
(pdf, 296 Kbytes)
- A. Adya, P. Bahl, J. Padhye, A. Wolman, and L. Zhou.
A Multi-Radio Unification Protocol for IEEE 802.11 Wireless Networks.
Microsoft Technical Report, Microsoft Research-TR-2003-41, June 2003.
(pdf, 376 Kbytes)
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