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Blog
utorak, prosinac 7, 2010

BISS tech blog is all about GPRS and UMTS technology, events, procedures, gossip and what's happening in this fast-changing world. You will also read what's happening in the mobile world plus a whole range of topics in the IT world. 

This blog was introduced, together with specific topics, in other to help users and telecom operators to better understand necessary procedures in mobile world.

Our first topic is about errors that can cause PDP Context activation rejections.

Text below is brief description about attach and PDP activation procedure together with most common rejection causes.

Read it carefully and do not hesitate to ask questions, we'll be glad to help to explain each cause in more detailed manner.

For more information see the Reference list below.

Introduction

  • Session Management (SM) establishes, modifies and releases packet data sessions with well defined QoS between UE and GGSN
  • Packet session attributes are called PDP contexts

  • A UE may have more than one PDP context simultaneously, each with a SM protocol entity



 

PDP Context Contents

  • PDP = Packet Data Protocol (generic name)

  • protocols to be used: IP (likely), X.25



 

Session Management Procedures

  • SM procedures require existing GMM context

  • SM procedures are:

PDP context activation

  • PDP address, QoS etc. are set

  • UE must be in PMM-CONNECTED state

PDP context modification

  • QoS etc. is modified

  • UE must be in PMM-CONNECTED state

PDP context deactivation

  • packet data session is released

  • PDP context also deactivated when UE moves to PMM-IDLE or PMM-DETACHED state



PDP Context Activation by UE

 

 

  • Request (1) contains NSAPI, PDP type, QoS, PDP address (static, dyn.)

  • Reject may occur due to insufficient resources, unknown PDP address or PDP type, unsupported or not subscribed options wished

  • Request (8) may occur if network does not offer requested QoS

PDP Context Activation by network

 

 

  • If HLR cannot determine a SGSN or the SGSN cannot find the UE with specified IMSI, the PDP Context Activation Procedure fails (3.b, 5.b)

  • After the SGSN‘s request the UE performs the PDP Context Activation

Causes in PDP Context Activation Procedure:

 

In a request, the Cause Value indicates the reason for the request. The Cause shall be included in the request message.

 

In a response, the Cause Value indicates the acceptance or the rejection of the corresponding request. In addition, the Cause Value may indicate what was the reason for the corresponding request. The Cause value shall be included in the response message.

 

Cause values are shared with the GTP' protocol specified in 3GPP TS 32.295.

 

'Request accepted' is returned when a GSN has accepted a control plane request.

'Non-existent' indicates a non-existent or an inactive PDP context.

'IMSI not known' indicates a non-existent MM context.

'MS is GPRS Detached' indicates an idle MM context.

'MS is not GPRS Responding' and 'MS Refuses' may be used by SGSN to reject a Network-Requested PDP Context Activation.

'Version not supported' is returned when the recipient does not recognize the version number in the request message.

'Request IMSI', 'Request IMEI', 'Request IMSI and IMEI' and 'No identity needed' are used by GGSN to notify SGSN what to do.

'No resources available' is a generic temporary error condition indicating that some kind of resource is used up for that moment excluding the conditions all dynamic PDP addresses are occupied and no memory is available.

'All dynamic PDP addresses occupied' indicates that the GSN does not have a free dynamic PDP address to allocate any longer.

'No memory available' indicates that the GSN does not have enough memory to use.

'Service not supported' is a generic error indicated that the GSN do not support the requested service.

'User authentication failed' indicates that the external packet network has rejected the user's service request.

'System failure' is a generic permanent error condition.

'Roaming restriction' indicates that the SGSN cannot activate the requested PDP context because of the roaming restrictions.

'P-TMSI Signature mismatch' is returned if either:

- the P-TMSI Signature stored in the old SGSN does not match the value sent by the MS via the new SGSN; or

- the MS does not provide the P-TMSI Signature to the new SGSN while the old SGSN has stored the P-TMSI Signature for that MS.

'Semantic error in the TFT operation', 'Syntactic error in the TFT operation', 'Semantic errors in packet filter(s)' and 'Syntactic errors in packet filters(s)' and 'PDP context without TFT already activated' are indications of abnormal cases involving TFTs.

The abnormal TFT cases and the use of the cause codes are defined in 3GPP TS 24.008.

'Invalid message format', 'Mandatory IE incorrect', 'Mandatory IE missing' and 'Optional IE incorrect' are indications of protocol errors described in the section Error handling.

'GPRS connection suspended' indicates that the GPRS activities of the mobile station are suspended.

'Authentication failure' indicates that the user authentication failed in the new SGSN.

'Context not found' indicates that the PDP Context referenced in an Active Secondary Context Request message was not found in the receiving GGSN.

'Relocation failure' indicates that the SRNS relocation failed in the new SGSN side.

'Unknown mandatory extension header' signals in a response message that the corresponding request included an extension header for which comprehension was required but unknown to the receiving end.

'APN Restriction type incompatibility with currently active PDP Contexts' conveys to an SGSN that a PDP Context was not allowed to be created or moved by the GGSN because if it had been created or moved, the rules for PDP Context coexistence as described in 3GPP TS 23.060, sub-clause 15.4, would have been broken.

'MS MBMS Capabilities Insufficient' is used by the SGSN to notify the GGSN that the MS MBMS Bearer Capabilities are less than the Required MBMS Bearer Capabilities.

'MBMS Bearer Context Superseded' indicates that the SGSN has already established an MBMS bearer plane with another GGSN.

'Invalid Correlation-ID' indicates that the Correlation-ID was already in use in the SGSN.

 


The SM Cause information elements for radio side are shown in the Table 1.

 


The MM Cause information elements for radio side are shown in the Table 2.

 


The SM Cause information elements on core side for radio side are shown in the Table 3.

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