Towards a Sensor Network Architecture:Lowering the Waistline

Culler et.al.

UCB

Vertically Integrated

• Constrained resources have lead to vertically integrated designs.

• Unable to interoperate.

• Reduces synergy between research groups.

• Impedes progress

Authors’ Believe

It is the central tenet of this paper that the primary factor currently limiting progress in sensor nets is not any specific technical challenge (though many remain, and deserve much further study) but is instead the lack of an overall sensor network architecture.

Nature of an architecture

• An architecture is set of principles that guide where functionality should be implemented along with a set of interfaces, functional components, protocols and physical hardware that follow those guidelines.

Sensor-net Protocol (SP)

• Sensor networks can also have a narrow waist – SP.

• It should be a best-effort single hop broadcast.

• Rich interface to allow multiple network layer components above to optimize for a range of potential link layers below in a hardware independent fashion.

Location of SP

• Applications differ in their communication patterns and need to be tied to their associated network protocols.

• Do not benefit from a common, universally routable addressing scheme.

SP Protocol Location.

The Emergence of Networking Abstractions andTechniques in TinyOS

Culler et.al.

UCB

Focus is on Networking abstractions.

• Four Categories– General : Widely used. Tiny OS provides both the

mechanism as well as policy e.g. tree-based routing.– Specialized: widely used. Tiny OS provides only

mechanism. App dictates policy e.g. Power management.

– In flux: Implemented as part of application e.g. epidemic protocols.

– Absence: widely discussed in literature but scarcely used in the application e.g Receive queues.

Neighbor Table

• Common Multi Hop Developments – List of neighboring nodes– Typical Information appearing in

neighborhood tables includes • addresses,• Link quality estimates• Routing metadata• Hop count

Send and Intercept Interfaces.

Common Techniques

• Communication Scheduling and Snooping

• Cross Layer Control

• Static Resource Allocation

Specific to Generic

• Over period of time, application specific abstractions will become more generic e.g Tree based routing.

• Application specific abstractions dominate because:– Motes only run one app at a time.– Power management is always app specific– Limited resources– Real time requirements.

A Unifiying Link Abstraction for Wireless Sensor Networks.

Culler et.al.

UCB

SP – Sensornet Protocol

• It sits between the network and link layer.

• It is best effort single hop communication specific.

• It is translucent.

• Simple, one bit for urgency and reliability.

SP Design

Advantages

• Multiple network protocols and link technologies to coexist.

• Design of SP is largely agnostic to single-hop and multi-hop networks.

Main operations

• Data Transmission– Shared message pool– Messages specify control information such as reliability– After transmission, SP provides feedback.

• Data Reception– Message is dispatched to associated network protocol. Filtering

may occur.

• Neighbor Management– Link Layer and Network layer cooperate to maintain and update

neighbor information.– Maintains information regarding link quality and power

scheduling.

Neighbor Table, Message Pool

SP send

SPNeighbor

Link Protocols

• Slotted Protocols– IEEE 802.15.14– Nodes periodically sends beacons

• Channel Sampling protocols– B-MAC– Long Preamble to wake up– Piggyback

Network Protocols

• Collection Routing– Mint Route, expected number of

transmissions to the root.– Route update beacons and data messages.

• Dissemination– Trickle, uses Cancel command to cancel

broadcast if suppress message is received.

• Aggregation– Synopsis Diffusion.

Results

Results

Network protocols above SP

Concluding Remarks

• The unified abstraction presented here is only a step towards an “overall sensor network architecture.”