ICC'2011

A Dual-Radio Framework for MAC Protocol Implementation in Wireless

Sensor Networks

Manjunath D, Mun Choon Chan, and Ananda A LNational University of Singapore

ICC'2011 2

Outline of This Talk

An overview of the background, problem, and the proposed solution

Analytical and experimental analysis of the proposed solution

Implementation and evaluation of our framework

Conclusions

ICC'2011 3

Background: Sensor Network MAC Protocols

Categories Synchronous protocols (e.g., SMAC [Infocom’02]) Asynchronous protocols

Sender-initiated techniques (e.g., BMAC [SenSys’04]) Receiver-initiated techniques (e.g., AMAC [SenSys’10])

Hybrids of synchronous and asynchronous techniques (e.g., SCP [SenSys’06])

ICC'2011 4

Problem

Even after a decade of research, sensor network MAC protocols still spend significant energy in idle-listening and/or control operations This is true even for the most recent AMAC

[Sensys’10] Such idle-listening and control operations are

inevitable These operations are part of the MAC functionality

ICC'2011 5

Proposed Solution

Our solution is based on the two key observations In typical sensor network MAC protocols,

there are two categories of operations Bandwidth-independent operations

• Durations of idle-listening and control operations are independent of the physical data rate

Bandwidth-dependent operations• Durations of transmission and reception of data packets are

functions of data rate

6

Proposed Solution It is well-known that there are two types of

sensor network specific radio transceivers1. Time-wise energy efficient transceivers2. Bit-wise energy efficient transceivers

ICC'2011

Parameter CC1000 CC2420Data rate 19.2 Kbps 250 Kbps

Tx Power 31.2 mW 52.2 mW

Rx/ID Power 22.2 mW 56.4 mW

Time-wise energy efficiency (Power)

Tx energy/bit 1625 nJ 208 nJ

Rx energy/bit 1156 nJ 225 nJ

Bit-wise energy efficiency

ICC'2011 7

Proposed Solution Unlike existing multi-radio systems, we do not

propose a new MAC protocol We show that how a given MAC protocol can

be re-implemented using dual radios so that in-evitable operations can be efficiently handled Bandwidth-independent operations are served on

time-wise energy efficient transceivers like CC1000 CC2420 like bit-wise energy efficient transceivers

are used to serve bandwidth-dependent operations We demonstrate significant energy savings by

re-implementing SMAC, BMAC, and SCP

ICC'2011 8

Proposed Solution: Analytical Analysis

In order to motivate the necessity for dual radios, we model BMAC, the most popular sensor network MAC protocol

We analyze by comparing energy consumption of single and dual-radio BMAC protocols

We mainly consider three parameters, number of nodes, load, and packet size

ICC'2011 9

Proposed Solution: Analytical Analysis

Power consumption vs. Number of nodes

ICC'2011 10

Proposed Solution: Analytical AnalysisPower consumption vs. Load

ICC'2011 11

Proposed Solution: Analytical AnalysisPower consumption vs. Packet size

ICC'2011 12

Proposed Solution: Experimental Analysis

Methodology of the analysis We analyze a representative protocol from

each of the three categories of MAC protocols

Bandwidth-independent and bandwidth-dependent operations are analyzed separately

ICC'2011 13

Experimental Analysis of Bandwidth-Independent Operations

-60%

Synchronous protocols (SMAC [Infocom’02])

Power consumption of a node with 10% duty-cycling

14

Asynchronous Protocols (BMAC [SenSys’04])Sender

Receiver

savings range from 37% to 46%

savings is about 60%

15

Hybrid Protocols (SCP [SenSys’06])Sender

Receiver

savings range from 50% to 55%

savings range from 69% to 81%

ICC'2011 16

Operation of RTS/CTS/DATA/ACK Exchange

Experimental Analysis of Bandwidth-Dependent Operations

ICC'2011 17

Dual-Radio Framework: Implementation

We re-implement BMAC and SCP by modifying their existing single-radio versions on TinyOS (1.x)

It is not necessary to re-implement SMAC separately Its dual-radio re-implementation results in a

operation similar to dual-radio SCP Moreover, SMAC and SCP protocols share same

synchronization procedure

ICC'2011 18

Dual-Radio Framework: Implementation

Energy saving operations are implemented on CC1000 Periodic radio wakeup, channel polling, and Tx

and Rx of preambles constitute these operations in BMAC

In SCP, such operations include achieving synchronization, radio wakeup, channel polling, and Tx and Rx of wakeup tones

Data is communicated on CC2420

ICC'2011 19

Dual-Radio Framework: Evaluation

Our dual-radio setup

ICC'2011 20

Dual-Radio Framework: Evaluation

Evaluations are carried out in two scenarios1. Using a classical set-up of a sender and a

receiver nodes2. In a more realistic scenario of multiple nodes

where not every node is in the vicinity of another

We compare dual-radio versions against single-radio versions running on CC2420

ICC'2011 21

Dual-Radio Framework: Evaluation

Evaluation results on a pair of sender and receiver nodes

state energy savingsWake-up 55% to 64%

Idle/Rx 3% to 46%

Tx 44% to 45%

Total 36% to 47%

Dual-Radio BMAC state energy savings

Wake-up 43% to 57%

Idle/Rx 44% to 50%

Tx 41% to 44%

Total 44% to 49%

Dual-Radio SCP/SMAC

ICC'2011 22

Dual-Radio Framework: Evaluation

Evaluation results of dual-radio BMAC on a setup of six nodes

Setup Wup (mJ) Id/Rx (mJ) Tx(mJ) Total (mJ)single-radio 102.33 3197.78 1569.67

dual-radio 62.28 1178.42 487.01 1733.97dual-radio with power control

52.94 403.62 467.13

Sum of the energy consumed at all six nodes

-65%-81%4874.03

928.99

ICC'2011 23

Conclusions Idle-listening and control operations of sensor

network MAC protocols are inevitable Our dual-radio framework is efficient in

serving such unavoidable operations The framework is generic to all the

mainstream categories of sensor network MAC protocols

The framework is easy-to-implement and significant savings of up to 81% is being observed