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两步接入过程一般在下列情况时发生：ü在RLC不确认模式下。ü手机通告其多时隙能力。ü手机向网络通告其Qos能力。
注：PacketResourceRequest中带有TLLI，用于BSS进行手机接入争抢判决。
一步还是二步接入由channelrequest中ie:establishmentcause决定01111*一步；01110*二步
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channel request为packet dl ack/nack中的一个IE。该状态处于数据传输模式
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On receipt of the Immediate Assignment message, the MS starts timer T3190.The MS stops T3190 on receipt of the first valid RLC/MAC block
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MS initiates the attach procedure by an Attach Request including IMSI or P-TMSI and old RAI toward the SGSN
In case P-TMSI has been sent and the SGSN has changed, SGSN asks the old SGSN to authenticate the MS
In case this authentication failed, SGSN performs an authentication procedure with the MS
If needed, SGSN informs the HLR and/or VLR (combined attached)SGSN sends an attach accept including a P-TMSI if a new one has been allocated
If P-TMSI was changed, the MS acknowledges the received TMSI with an Attach Complete message
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After the GPRS Detach procedure, the MS moves from READY State to IDLE state
It can be initiated by the MS or the network
The Detach Type can be a GPRS only, IMSI only or combined
If the GPRS Detach is not due to a switch off of the MS, the network send a GPRS Detach Accept message to the MS
The MS may also be implicitly detached by the network without notifying the MS after the mobile reachable timer expired or after an irrecoverable radio error causes disconnection of the logical link.
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A PDP context must be activated before data can be transmitted or received
One PDP context is related to one MS and one NSAPI. One PDP context can be either active or inactive
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The deactivation occurs in three cases:
after the deactivation procedureafter expiration of the READY TIMERafter a GPRS detach6.1.3.3.1PDP context deactivation initiated by
the MS
In order to deactivate a PDP context, the MS sends a DEACTIVATE PDP CONTEXT REQUEST message to the network, enters the state PDP-INACTIVE-PENDING and starts timer T3390. The message contains the transaction identifier in use for the PDP context to be deactivated and a cause code that typically indicates one of the following causes:
# 26: insufficient resources;
# 36: regular PDP context deactivation; or# 37: QoS not accepted.
The network shall reply with the DEACTIVATE PDP CONTEXT ACCEPT message. Upon receipt of the DEACTIVATE PDP
CONTEXT ACCEPT message, the MS shall stop timer T3390. Both the MS and the network shall initiate local release of the logical link if it is not used by another PDP context.6.1.3.3.2PDP context deactivation initiated by
the network
In order to deactivate a PDP context, the network sends a
DEACTIVATE PDP CONTEXT REQUEST message to the MS and starts timer T3395. The message contains the transaction identifier in use for the PDP context to be deactivated and a cause code that typically indicates one of the following causes:# 36: regular PDP context deactivation;# 38: network failure; or# 39: reactivation requested.
The MS shall, upon receipt of this message, reply with a
DEACTIVATE PDP CONTEXT ACCEPT message. Upon receipt of
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The MS sends a RA Update Request message including the old RA identifier (RAI) and the Update Type. The PCU adds the Cell Id, RAC and LAC where the message has been received and pass the message to the SGSNSecurity function may be executed
SGSN validates the MS’s presence in the new RA. If one check fails, the SGSN rejects the procedure.The MM context is updated
SGSN returns a RA update accept to the MS. A new P-TMSI may be allocated
In case P-TMSI is reallocated, MS acknowledges it by sending a RA update complete
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