Monday, November 9, 2009

Paging in UMTS (Idle Mode )

*Establishing radio connection in UTRAN always initial by UE

Idle Mode Paging:
Paging info in Idle Mode is carried by Paging Type 1
-> Each message can have several Paging Recordes
-----> Each Record has Paging Request for different mobile
-> Some times it may not have Paging records but it may be representing change in broadcast info
------> BCCH modification info element containe value tag in MIB
------> When mobile reads the above PagingType, UE reads BCCH to get MIB.
-> For incoming call, once UE reads PagingType1 and understands that Paging Records is for self, it informs MM Layer to initiate call establishment procedure
-> To save Battery draining which caused by continuously listening to Paging channel PCH
-----> The mechnaism of DRx is introduced.
-----> Caliculated using IMSI, The DRX (CN domain specific cycle length co-efficient) will be present in SIB1
-----> The calicuated result mentions the Paging occasion, the same value is known to N/w and UE which is known as Paging occasion. These are frame numbers. As both are holding same value n/w makes sure that paging messages will be delivered these frame numbers and UE also monitors at that time only.
-----> To save the power, which is caused by reading Paging channel for each occasion, PICH (indicator channel) is introduced
-----> N/W making the DRX cycle length bigger makes UE to listen PICH : But this results longer call setup time for mobile terminated call. The reason being, UE listens to Paging Channel in bigger timer intervals.

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