T312 and N312 in UMTS.

[fahmi]

Hello experts,

I have read that both T312 and N312 were broadcast to the UE in SIB 1 and that the T312 was started when UE initiated the establishment of the DPCH i.e. when the RRC Connection Request message was sent.

Here I have some confusion, when the UE get the T312 value from the RNC (consedering that the RRC Connection Request is the first message between the UE and the RNC) ?
Could you please explain to me the chronological steps and the relation between T312 and N312.

BR,
Fahmi.

[tukangoptim]

hi Fahmi, pls see attached,
hope it helps

[usama0795]

There are actually 2 types of T312 and N312 (N312 / N312 for connected mode / T312 / T312 for connected mode.

N312: This parameter defines the maximum number of "in sync" indications received from L1 during the establishment of a physical channel (UE counter used in idle mode). When a physical dedicated channel establishment is initiated by the UE, the UE starts a timer T312 and wait for layer 1 to indicate N312 "in sync" indications. On receiving N312 "in sync" indications, the physical channel is considered established and the timer T312 is stopped and reset. If the timer T312 expires before the physical channel is established, the UE considers this as a "physical channel failure".

N312 for connected mode: This parameter defines the maximum number of "in sync" indications received from L1 during the establishment of a physical channel (UE counter used in connected mode). When a physical dedicated channel establishment is initiated by the UE, the UE shall start a timer T312 and wait for layer 1 to indicate N312 "in sync" indications. On receiving N312 "in sync" indications, the physical channel is considered established and the timer T312 is stopped and reset. If the timer T312 expires before the physical channel is established, the UE considers this as a "physical channel failure".

T312:The parameter defines the timer for supervising successful establishment of a physical channel (UE timer used in idle mode). When a physical dedicated channel establishment is initiated by the UE, the UE should start a timer T312 and wait for layer 1 to indicate N312 "in sync" indications. On receiving N312 "in sync" indications, the physical channel is considered as established and the timer T312 is stopped and reset. If the timer T312 expires before the physical channel is established, the UE should consider this as a "physical channel failure".

T312 for connected mode: The parameter defines the timer for supervising successful establishment of a physical channel (this UE timer is used in connected mode). When a physical dedicated channel establishment is initiated by the UE, the UE should start a timer T312 and wait for layer 1 to indicate N312 "in sync" indications. On receiving N312 "in sync" indications, the physical channel is considered as established and the timer T312 is stopped and reset. If the timer T312 expires before the physical channel is established, the UE should consider this as a "physical channel failure".

[nupong]

As I understood, even UE in idle mode (no need RRC Connection Request), UE could listen SIB from network

[fahmi]

Yes, In fact SIB1 is broadcasted on BCH. So that even in idle, the UE gets the T312 and N312 values from the RNC and use them.