LTP5901-IPM datasheet(18/36 Pages) LINER

18 / 36 page

LTP5901-IPM/LTP5902-IPM

59012ipmfa

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

Typical perForMance characTerisTics

As described in the SmartMesh Network Overview sec-

tion, devices in network spend the vast majority of their

time inactive in their lowest power state (doze). On a

synchronous schedule a mote will wake to communicate

with another mote. Regularly occurring sequences which

wake, perform a significant function and return to sleep

are considered atomic. These operations are considered

atomic as the sequence of events can not be separated

into smaller events while performing a useful function.

For example, transmission of a packet over the radio is an

atomicoperation.Atomicoperationsmaybecharacterized

in either charge or energy. In a time slot where a mote

successfully sends a packet, an atomic transmit includes

setup prior to sending the message, sending the message,

receiving the acknowledgment and the post processing

needed as a result of the message being sent. Similarly in

a time slot when a mote successfully receives a packet, an

atomic receive includes setup prior to listening, listening

until the start of the packet transition, receiving the packet,

sendingtheacknowledgeandthepostprocessingrequired

due to the arrival of the packet.

To ensure reliability each mote in the network is provided

multiple time slots for each packet it nominally will send

and forward. The time slots are assigned to communicate

upstreamwithatleasttwodifferentmotes.Whencombined

with frequency hopping this provides temporal, spacial

and spectral redundancy. Given this approach a mote will

often listen for a message that it will never receive, since

the time slot is not being used by the transmitting mote.

It has already successfully transmitted the packet. Since

typically 3 time slots are scheduled for every 1 packet to

be sent or forwarded, motes will perform more of these

atomic“idlelistens”thanatomictransmitoratomicreceive

sequences. Examples of transmit, receive and idle listen

atomic operations are shown in Figure 11.

LTP5901-IPM Datasheet(PDF) 18 Page - Linear Technology