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Title: Comparison of Enhanced Slotted Mode vs Periodical Power Off

Abstract: This contribution summarizes the comparison of the enhanced slotted mode with the periodical power off of the modem.

Recommendation: FYI

Source:

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Background Slotted Mode Operation

– ZTE proposed this approach to expand SCI for the battery operated M2M devices to increase their battery life. (C22-20110725-015_ZTE_Slot Cycle Index Expansion)

Periodical Power Off– Another approach under discussion is to let the

application to control the wireless modem’s on and off instead of increasing SCI.

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Comparison

Increasing SCI Power-off Modem

Power consumption Less when sleeping period is short

Less when sleeping period is long

Synchronization time fast slow

Clock maintained in modem

yes no

Clock maintained in the application processor

Not necessary yes

Spec change required yes no

Impact network capacity none yes

Backward compatibility yes yes

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Power Consumption (1) Slotted Mode Operation

– Assume modem consume 1mA in sleep period of the slotted mode operation. (note modem clock not shared with AP’s clock)

– For example, if SCI = 1 hour, the modem consume 1 mAH during a cycle.

Periodical Power Off– Assume modem takes 15 seconds to complete initialization

• 10 seconds without radio transmission and consume 50mA• 5 seconds with radio transmission and consume 300mA

– The total power consumption per cycle • (10 x 50 + 5 x 300)/3600 = 0.55 mAH

– Note: AP needs to maintain power for operation

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Power Consumption How Often to Wake Up

Example: C00-20110124-019 It may need to wake up once to twice per hour roughly

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Standard Impacts Slotted Mode Operation

– It needs to change the 1x spec to increase the length of SCI via either modifying existing messages or defining new messages.

Periodical Power Off– APP in the mobile device can negotiate with the M2M

server for next power-on time so that the server could transmit the data or message at the modem power-on period. Since mobile’s initialization duration may vary, it might need a mechanism to make sure the delivery of the data or message during waking period of the device. It could be implementation dependant.

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Performance Impacts Slotted Mode Operation

– No need to transmit the registration message when the mobile device wakes up.

Periodical Power Off– Need to transmit the power-down and power-up

registration messages on every power cycle of modem. This will impact the network capacity when a lot of M2M devices are deployed.

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Time Synchronization Slotted Mode Operation

– If the sleep period is not too long, the clock will not drift too much. The modem will sync with network fast.

Periodical Power Off– Each power cycle of modem will require the modem

clock to re-synchronize with the network timing. It will take longer time to complete the synchronization.

– The AP clock needs to be synchronized with the application server’s timing.

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Compatibility & Feasibility Slotted Mode Operation

– The extended SCI will not impact the existing modems. But the existing modems do not have this advantages.

– The implementation should be possible.

Periodical Power Off– The approach is applicable to the legacy modem.– If using two-ASIC solution, i.e. AP is separated from the

modem, it is feasible to power down the modem. However if it is a single-ASIC solution, i.e. the AP and modem are integrated into one ASIC, it needs to further check ASIC spec to verify the feasibility.

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Conclusion Summary

– If the modem needs to sleep for a relative short period, the enhanced slotted mode performs better.

– If the modem needs to sleep for a long period, the power-off modem may have advantage.