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LTP5901-IPR/LTP5902-IPR

59012iprfa

For more information www.linear.com/LTP5901-IPR or www.linear.com/LTP5902-IPR

Typical perFormance characTerisTics

In mesh networks data can propagate from the manager

to the nodes, downstream, or from the motes to the man-

ager, upstream, via a sequence of transmissions from one

device to the next. As shown in Figure 8, data originating

from mote P1 may propagate to the manager directly or

through P2. As mote P1 may directly communicate with

the manager, mote P1 is referred to as a 1-hop mote. Data

originatingfrommoteD1,mustpropagatethroughatleast

one other mote, P2 or P1, and as a result is referred to as

a 2-hop mote. The fewest number of hops from a mote to

the manager determines the hop depth.

As described in the Application Time Synchronization

section,Eternaprovidestwomechanismsforapplications

to maintain a time base across a network. The synchro-

nization performance plots that follow were generated

using the more precise TIMEn input. Publishing rate is

the rate a mote application sends upstream data. Syn-

chronization improves as the publishing rate increases.

Baseline synchronization performance is provided for a

network operating with a publishing rate of zero. Actual

performance for applications in network will improve

as publishing rates increase. All synchronization testing

was performed with the 1-hop mote inside a temperature

chamber. Timing errors due to temperature changes and

temperature differences both between the manager and

this mote and between this mote and its descendents

therefore propagated down through the network. The

synchronization of the 3-hop and 5-hop motes to the

manager was thus affected by the temperature ramps

even though they were at room temperature. For 2°C/

minute testing the temperature chamber was cycled

between –40°C and 85°C at this rate for 24 hours. For

8°C/minute testing, the temperature chamber was rapidly

cycled between 85°C and 45°C for eight hours, followed

by rapid cycling between –5°C and 45°C for eight hours,

and lastly, rapid cycling between –40°C and 15°C for

eight hours.

Figure 8. Example Network Graph

Figure 7a. Supply Current vs Packet Rate

Figure 7b. Packet Latency vs Reporting Interval

PACKET RATE (PACKETS/s)

0.8

1.0

1.2

2.0

59012IPR F07a

0.6

0.4

0.2

1.6

1.8

1.4

REPORTING INTERVAL (s)

1.0

1.5

2.5

59012IPR F07b

0.5

2.0

5 HOPS

4 HOPS

3 HOPS

2 HOPS

1 Hop

MANAGER

1 HOP

2 HOP

3 HOP

5800IPM F08

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