Cisco Cisco ASR 5000
Serving GPRS Support Node (SGSN) Overview
Features and Functionality ▀
SGSN Administration Guide, StarOS Release 18 ▄
The SGSN can now limit data rates (via QoS) on a per-RNC basis. Some RNCs support HSPA rates (up to 16 Mbps in
the downlink and 8 Mbps in the uplink) and cannot support higher data rates - such as those enabled by HSPA+
(theoretically, up to 256 Mbps both downlink and uplink). Being able to specify the QoS individually for each RNC
makes it possible for operators to allow their subscribers to move in-and-out of coverage areas with different QoS
levels, such as those based on 3GPP Release 6 (HSPA) and 3GPP Release 7 (HSPA+).
the downlink and 8 Mbps in the uplink) and cannot support higher data rates - such as those enabled by HSPA+
(theoretically, up to 256 Mbps both downlink and uplink). Being able to specify the QoS individually for each RNC
makes it possible for operators to allow their subscribers to move in-and-out of coverage areas with different QoS
levels, such as those based on 3GPP Release 6 (HSPA) and 3GPP Release 7 (HSPA+).
For example, when a PDP context established from an RNC with 21 Mbps is handed off to an RNC supporting only 16
Mbps, the end-to-end QoS will be re-negotiated to 16 Mbps. Note that an MS/UE may choose to drop the PDP context
during the QoS renegotiation to a lower value.
Mbps, the end-to-end QoS will be re-negotiated to 16 Mbps. Note that an MS/UE may choose to drop the PDP context
during the QoS renegotiation to a lower value.
This data rate management per RNC functionality is enabled, in the radio network controller (RNC) configuration
mode, by specifying the type of 3GPP release specific compliance, either release 7 for HSPA+ rates or pre-release 7 for
HSPA rates.
mode, by specifying the type of 3GPP release specific compliance, either release 7 for HSPA+ rates or pre-release 7 for
HSPA rates.
Ignore Context-ID during 4G/3G Handovers
HSS and HLR, when operating as separate network nodes, are required to use the same context-ID for a given APN-
configuration of a subscriber. During inter-RAT cell reselections and handovers between 2G/3G and 4G, if the SGSN
does not find a matching APN-configuration for the given context-ID learnt from the peer node, then the PDP does not
get established. This could result in SRNS relocation failures when none of the PDP's learnt from the SGSN has a
matching context-ID in the HLR.
configuration of a subscriber. During inter-RAT cell reselections and handovers between 2G/3G and 4G, if the SGSN
does not find a matching APN-configuration for the given context-ID learnt from the peer node, then the PDP does not
get established. This could result in SRNS relocation failures when none of the PDP's learnt from the SGSN has a
matching context-ID in the HLR.
New commands have been added to enable the operator to configure the SGSN to ignore the context-ID provided by the
peer and to use the PDP- type and address information to search through HLR subscription and to update the context-ID
information within the PDP. For details, refer to the description for the
peer and to use the PDP- type and address information to search through HLR subscription and to update the context-ID
information within the PDP. For details, refer to the description for the
rau-inter
command under the Call-Control
Profile Configuration Mode Commands section of the Command Line Interface Reference.
Interface Selection Based on UE Capability
The SGSN selects S6d/Gr interface based on whether hss-peer-service or map service is associated with the SGSN or
GPRS service. If both the services are associated, then the selection is made based on configuration of the CLI
command
GPRS service. If both the services are associated, then the selection is made based on configuration of the CLI
command
prefer subscription-interface
under the Call Control Profile mode. With this feature enhancement,
the SGSN now allows selection of S6d/ Gr interface only if the UE is EPC capable. A new CLI option
epc-ue
is added
to the command
prefer subscription-interface
under the Call Control Profile mode for this enhancement. If
this keyword is configured the S6d/Gr interface is selected only if UE is EPC capable. If this keyword is not configured
the SGSN selects the S6d/Gr interface based on whether hss-peer-service or map service is associated with the SGSN or
GPRS service (this is also the default behavior). The interface selection based on UE capability is done only at the time
of Attach / new SGSN RAU / SRNS. Interface selected during Attach / new SGSN RAU / SRNS may change while
doing inter PLMN RAU (intra SGSN) procedures.
the SGSN selects the S6d/Gr interface based on whether hss-peer-service or map service is associated with the SGSN or
GPRS service (this is also the default behavior). The interface selection based on UE capability is done only at the time
of Attach / new SGSN RAU / SRNS. Interface selected during Attach / new SGSN RAU / SRNS may change while
doing inter PLMN RAU (intra SGSN) procedures.
Intra- or Inter-SGSN Serving Radio Network Subsystem (SRNS) Relocation (3G
only)
Implemented according to 3GPP standard, the SGSN supports both inter- and intra-SGSN RNS relocation (SRNS) to
enable handover of an MS from one RNC to another RNC.
enable handover of an MS from one RNC to another RNC.
The relocation feature is triggered by subscribers (MS/UE) moving from one RNS to another. If the originating RNS
and destination RNS are connected to the same SGSN but are in different routing areas, the behavior triggers an intra-
SGSN Routing Area Update (RAU). If the RNS are connected to different SGSNs, the relocation is followed by an
and destination RNS are connected to the same SGSN but are in different routing areas, the behavior triggers an intra-
SGSN Routing Area Update (RAU). If the RNS are connected to different SGSNs, the relocation is followed by an