`
`1
`
`Joint RAN WG1 and RAN WG2 on LTE
`Athens, Greece, 27th – 31th March 2006
`
`: 3.1
`Agenda Item
`: LG Electronics
`Source
`: Disucssion on LTE Paging and DRX
`Title
`Document for : Discussion and Decision
`
` R2-061014
`
`Introduction
`This document discusses how to specify Paging and DRX procedure and PCH channel in LTE. In this document, the
`DRX procedure is defined as a procedure controlling inactivity of a UE in active mode for UE battery power saving.
`
`Differences between Paging and DRX
`We consider that the paging procedure is used by aGW to find at which cell in a tracking area a UE is and to offer
`efficient UE battery power management. The paging procedure is applied only to a UE in idle mode. Since a paged UE
`has no short UE id (e.g. C-RNTI) allocated by a cell, a paging message will carry a longer UE id e.g. IMSI and TMSI.
`This paging procedure should be distinguished with the DRX procedure for an active UE.
`
`The DRX procedure for active mode is used by eNode B to offer efficient UE battery power management. The paging
`procedure is applied only to a UE in active mode. If DL/UL traffic is temporarily inactive, eNode B may apply this
`DRX procedure to a UE in active mode. If this DRX procedure is applied, the UE would discontinuously monitor DRX
`signaling sent on DL according to a cycle set by the eNode B. Since an active UE has a short UE id (e.g. C-RNTI)
`allocated by a cell, eNode B can lead a UE with DRX to wake up by indicating the short UE id.
`
`In summary, Idle mode Paging and active mode DRX are different as follows:
`
`
`RRC mode
`Controlling network node
`Signalled Area
`Signalled UE identity
`
`Paging Procedure
`Idle mode
`aGW: paging initiation
`eNode B: paging transmission
`A tracking area
`A long identity (e.g. IMSI, TMSI)
`allocated by NAS
`
`DRX Procedure
`Active mode
`eNode B
`A cell
`A short identity (e.g. C-RNTI)
`allocated by AS in eNode B
`
`
`
`What long and short identies are needs to be further studied. However, we think that UE identies for idle and active
`mode would be different.
`
`Air Interface for Paging and DRX
`In the section above, we discuss how paging and DRX procedures are different. We think the differences between them
`should be considered when we design the LTE air interface.
`
`At this moment, the PCH channel is defined in TR 25.813 for transmitting a paging message. However, it is not so clear
`whether or not PCH is also used for DRX of an active UE.
`
`In case of the DRX procedure, a short UE identity which may be equal to or less than 16 bits could be easily embedded
`into L1/2 control information at the first symbol of a sub-frame. It is because L1/2 control information e.g. for DL/UL
`
`3GPP
`
`Ericsson v. IV II LLC
`Ex. 1006 / Page 1 of 2
`
`

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`
`2
`
`SCH would use the short UE identity as well. Thus, wake-up signaling of active UEs with a short UE identity may be
`compatible with L1/2 control information.
`
`On the other hand, a long UE identity which may be 32 bits may not be compatible with L1/2 control information. It is
`because L1/2 control information e.g. for DL/UL SCH would not use the long UE identity. Thus, a paging message with
`the long UE identity could not be embedded into L1/2 control information. However, if PICH is necessary, PICH could
`be embedded into L1/2 control information because PICH would carry a short size of quick indications.
`
`Therefore, the following points could be concluded.
`
`1) Only a UE in idle mode shall monitor a PCH channel based on a long UE identity for UE power saving.
`
`2) A UE in active mode may monitor L1/2 control information with a short UE identity in a cycle set by eNode B
`for UE power saving.
`
`3)
`
`4)
`
`If an active UE with DRX is scheduled, eNode B will insert the short identity of the UE into L1/2 control
`information including scheduling information according to the set cycle.
`
`If an active UE with DRX is not scheduled, , eNode B will not insert the short identity of the UE into L1/2
`control information according to the set cycle.
`
`Paging Indicator Channel
`PICH may have a benefit for UE battery saving because UE is quickly able to check its own paging by simply decoding
`Paging Indications on PICH. Decoding a paging indication will be quicker than decoding a paging message. Thus, the
`PICH channel may be need in LTE for efficient UE power saving. Furthermore, PICH could do frequency hopping for
`frequency diversity. The hopping information could be given from system information. Alternatively, L1/2 control
`information could be used instead of PICH.
`
`Conclusion
`It is proposed to discuss the following points:
`
` Two UE power saving schemes are used based on RRC mode i.e. the paging procedure for idle moe and DRX
`procedure for active mode.
`
` The paging procedure for idle mode relies on the PCH channel, possibly with short indications such as PICH
`or L1/2 control information.
`
` The DRX procedure for active mode relies on L1/2 control information which is used for DL/UL SCH.
`
`3GPP
`
`Ex. 1006 / Page 2 of 2
`
`