MERLIN: Integrating energy-efficient MAC and Routing MERLIN: A Synergetic Integration of MAC and Routing for Distributed Sensor Networks A.G.Ruzzelli, M.J.O ’ Grady, R.Tynan, G.M.P.O ’ Hare. Adaptive Information Cluster project (AIC) and Smart Media Institute (SMI) Department of Computer Science University College Dublin Ireland.

MERLIN: Integrating energy-efficient MAC and Routing Summary Overview of WNSs and protocols Motivation Phase1: MERLIN design –Motivation and objectives –Fundamental concept –MAC details –Routing details Phase2: Simulation and results –Scheduling performance –Comparison against SMAC+ESR Conclusion

MERLIN: Integrating energy-efficient MAC and Routing Sensor network characteristics Energy consumption: primary objective The wake-up concept Very low duty cycle (even less than 5%) Small packets smaller than in ad-hoc networks (e.g. temperature data is few bytes) Low data traffic per node

MERLIN: Integrating energy-efficient MAC and Routing Communication reliability: Nodes are prone to fail and bad channel condition might affect the transmission Scalability: Medium Access control should be able to deal with large scale networks Unique global addressing: Low processing capability High end-to-end latency of packets Important issues of protocols for WSNs

MERLIN: Integrating energy-efficient MAC and Routing What does MERLIN address? Energy-efficiency by an adaptive node activity scheduling End-to-end latency reduction Separate MAC and Routing layers in low duty-cycle multi-hop networks cause an extremely high latency –(e.g. SMAC +DSR at 5% duty  >35s delay for packets of 10 hops away nodes ) Communication reliability failure, interference, depletion, mobility  Addressing a single node can result in high error probability Node-to-Gateway routing Protocol generality Initial idea presented at IWWAN04: A.G. Ruzzelli, Evers, Dulman, Van Hoesel, Havinga. “ On the design of an energy-efficient low-latency integrated protocol for Wireless Sensor networks" What MERLIN does NOT address: Node-to-node routing located at several hop distance

MERLIN: Integrating energy-efficient MAC and Routing Design goals MAC+Routing integration into a simple architecture; No usage of handshake mechanisms; No specific node addressing; Reduce latency while ensuring a very low energy consumption Increasing communication reliability while limiting packet overhead;

MERLIN: Integrating energy-efficient MAC and Routing Initial idea: Timezone division Gateway Node (European EYES project, NL) Nodes with the same color are in the same time zone Every node sets its zone and forward the sync packet to more distant nodes. A node division both in time and space is generated, i.e. timezone

MERLIN: Integrating energy-efficient MAC and Routing Division of the network in timezones Nodes report to the closest gateway Nodes within the same zone wake up, transmit and go into sleep simultaneously

MERLIN: Integrating energy-efficient MAC and Routing Timezone data traffic Upstream multicast: Packets are forwarded to lower zones Zone 2 Zone 3 Zone 1 Downstream multicast: Packets transmitted to higher zones Local broadcast: Packets reach all neighbours. No forwarding performed Sleeping

MERLIN: Integrating energy-efficient MAC and Routing Global allocation Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 Frame The allocation of further zones can be obtained by appending the same table. The allocation of further frames is obtained by flanking the same table.

MERLIN: Integrating energy-efficient MAC and Routing Accessing the table Nodes in the same timezone contend the slot for local broadcast only once each 4 frametimes If Mod(FRAME#, NZONE) = Mod(myZone,NZONE) To access the current slot in the table: SLOT# = GlobalTime/SLOTTIME currentSlot = Mod(SLOT#, NSLOT) NZONE = 4 NSLOT =9

MERLIN: Integrating energy-efficient MAC and Routing Recall that Nodes in the same zone share the same slot for activity transmission in MERLIN (multicast) do not address a specific receiving node How can simultaneous transmission be handled? How can correct/incorrect receptions be notified? Intra-zone MAC features Zone N Zone N+1 Zone N-1

MERLIN: Integrating energy-efficient MAC and Routing Burst tones can help Properties –Are signal impulse  Do not contain any coded information –Are robust  Several simultaneous burst can still be identified as one burst –They are shorter that a normal ACK Utilization Multicast: Bursts identify correct receptions BACK In transmission to the gateway Broadcast: Bursts identify reception errors BNACK In local broadcast

MERLIN: Integrating energy-efficient MAC and Routing Asynchronous transmission Mechanism Tx1 Tx2 Tx1 CCA PreamblePacketPreamblePacket Listen Sleep Rando m Burst* * burstACK if local broadcast, burst NACK if multicast CCA Sleep Listen Transmit CCA Sleep Tc S l o t l e n g t h Tc Tx1 Tx2 Rx1 CCA Listen Sleep Rx2 Burst* Rx2

MERLIN: Integrating energy-efficient MAC and Routing Disadvantages 1)MERLIN does not address a specific receiving node  multiple copy of the same msg sent can be generated   increase overhead! 2) Some collisions due to the Hidden Terminal Problem (HTP) Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 A B Zone 3 A B ?

MERLIN: Integrating energy-efficient MAC and Routing Routing characteristics (I) 3 small buffers of upstream, downstream and local broadcast are provided Packets organised in multiple msgs of the same data traffic type; Packets contain a msg-ID index of included msgs; Nodes, which lose the contention, keep on listening to the beginning of the transmitted packet then go into sleep; Nodes discard from their buffer the msgs already fowarded. Pro : Reduce overhead in transmission! Con : Small increase of node activity; Increase complexity. Channel contention messages Msg-index Discard msgs already forwarded from their queue P a c k e t Listen to the packet index Controlled multipath

MERLIN: Integrating energy-efficient MAC and Routing Routing characteristics (II) Timezone maintenance Timezone update are sent periodically; Failed reception of timezone update from zone N-1 node to zone N node triggers a upstream multicast of Timezone Update request (TUR) –N-1 node/s reply  Connection reestablished N-1 failed  local broadcast TUR –At least one reply  change of zoen to N+1 N failed  downstream broadcast TUR TUR

MERLIN: Integrating energy-efficient MAC and Routing Assessment Simulation tool: OmNet++ Framework: EU EYES project Evaluation against SMAC+ESR In Progress: Philips Sand node implementation

MERLIN: Integrating energy-efficient MAC and Routing Scenario and Setup Scenarios 5 nodes two-hops 70 nodes Random multihop Metrics: Energy consumption per RX packet Network lifetime E-to-E latency Total packet overhead % sleeping time Parameters: Duty cycle (acting on CW and frametime size) Low traffic conditions (12 packet/min) High traffic conditions (60 packet/min) Sources Forwarder Destinations

MERLIN: Integrating energy-efficient MAC and Routing Low traffic 2-hops scenario

MERLIN: Integrating energy-efficient MAC and Routing High traffic 2-hops scenario

MERLIN: Integrating energy-efficient MAC and Routing Multihop scenario: Lifetime Note: These graphs have little relevance if not related to the EtoE latency

MERLIN: Integrating energy-efficient MAC and Routing Multihop scenario: Latency/energy Given a certain sustainable latency, MERLIN consumes between 2 and 2.5 times less energy than SMAC+ESR

MERLIN: Integrating energy-efficient MAC and Routing Total packet overhead The MAC routing integrated nature MERLIN results in a smaller packet overhead than SMAC+ ESR.

MERLIN: Integrating energy-efficient MAC and Routing Conclusion Description and simulated results of MERLIN have been presented; MERLIN is suitable for large scale sensor networks with energy consumption as main goal; MERLIN is suitable for communication to a from the gateway The multicast mechanism with burst ACK showed large improvement on the communication reliability The integrated nature and the absence of handshake mechanisms help reducing the EtoE packet delay EtoE delay can be traded-off for a longer network lifetime Results showed lifetime being extended by a factor of 2.5 of MERLIN with respect to SMAC

MERLIN: Integrating energy-efficient MAC and Routing Thank you for your kind attention