inactivity timer start vs long cycle start

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inactivity timer start vs long cycle start

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what does inactivity timer start and long cycle start means in LTE?


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  • In short, the Long DRX cycle follows defined periodicity (each cycle starts at specified subframe offset at configured intervals). Inactivity timer is (re)started whenever the UE decodes a uplink grant or downlink allocation from the PDCCH.

    A picture might illustrate this better, so you could take a look at e.g. this presentation:

    Also 3GPP TS 36.321 (LTE MAC) and 3GP PTS 36.331 (RRC) describe the DRX parameters and their functionality, albeit in textual format.

  • Hi Cellular Expert,

    I have a question about "Inactivity timer" in page 8 of Chapter_21_PowerEff_Slides.ppt.

    I think this timer is drx-InactivityTimer defined in TS36.331 but is this same of "user inactivity timer" which is explained in following links?

  • Hi, the "user inactivity timer" refers to possible implementation -dependent timer in the network to release the RRC connection (or detect the UE has been lost etc. although this can be detected from other things such as UE not anymore transmitting any CQI reports etc.) after no data has been exchanged for a specified time. This has nothing to do with connected mode DRX operation in the UE.

    The drx-InactivityTimer is on the other hand clearly specified, and used in the UE in case the connected mode DRX operation is configured.