gprs 3g roaming

GPRS Roaming -Connectivity & Scenarios

2 © Nokia Siemens Networks Company confidential

BSC

BTSMSC

HLR/AuCEIR

PoIBilling System

OSS

IN

SMSC

SGSN GGSN

PDN

DNS

FW

DHCP

VAS

MS

CS

PS

GPRS Network Architecture (Recap)


GPRS Network – Logical (Recap)

Mediation

PLMN 1

ISP

SGSN

GGSNFW

DNS

CG

VAS

HLR MSS• MS sends “Attach Request" to

SGSN.

• SGSN sends "Create PDP Context Request" to respective GGSN

• MS sends "Activate PDP Context Request" to SGSN.

• SGSN checks against HLR.• SGSN sends “Attach Accept" to the

MS

• SGSN queries DNS fro GGSN IP Address.

• SGSN sends "Activate PDP Context Accept" to the MS and MS is assigned IP address.

• GGSN sends "Create PDP Context Response" back to SGSN with IP Address.

• DNS returns with corresponding GGSN IP..

• GTP Tunnel is established between SGSN & GGSN.• GPRS traffic starts flowing towards ISP OR VAS according to the service.

Call Flow


There are three important aspects of GPRS Roaming between two networks;

GPRS Location update: The user should be able to do the location update in visited SGSN. For this, the existing SS7 connectivity through GMSC, between two networks, is used.

GPRS Traffic (DNS & PS Data):The user should be able to use its own defined services without any change in handset settings. The user always uses its Home GGSN to access its services. This requires the connectivity between the GN network of two operators. Border Gateway Router & GRX connectivity is used for this purpose.

Charging:Since user is always connected to its HOME GGSN, the charging is controlled by the home network. The visited SGSN also generates the CDRs for the visited subscriber for the settlement through TapOuts.

GPRS Roaming


GPRS Network – Roaming

Mediation

PLMN 1

ISP

SGSN

GGSNFW

DNS

CG

VAS

HLR MSS

BGR/FW

PLMN-B

GRX

Direct GRX Connectivity

• BGR is connected to GRX (GPRS Roaming Exchange) Directly OR through ISP Router.

• Border Gateway Router (BGR) /FW is connected on Gn Vlan.

6 © Nokia Siemens Networks Company confidential Mediation

PLMN 1

ISP

SGSN

GGSNFW

DNS

CG

VAS

HLR MSS

BGR/FW

PLMN-B

GRX

GPRS Network – RoamingGRX Connectivity through ISP

PS: In Home OR Roaming Scenario, the users uses his HOME GGSN as it uses own Home Services & Settings.

• BGR can be connected to GRX (GPRS Roaming Exchange) through ISP Router.

•The GN Networks gets routed to each other network on the GTP Ports through BGR & GRX..

•The SGSN/GGSN of both the networks get connected to each other for GPRS Traffic.

•The DNS is configured with the GRX DNS as the ROOT DNS.

•All the DNS queries other than the Home APNs gets routed to GRX DNS.

GPRS Roaming – Call Flows


PLMN 1

ISP

SGSNDNS

CG

HLR MSS

BGR/FW

PLMN-B

GRX

GPRS Call Flow – InRoamer

GGSN

GGSNFW

VAS

• MS sends "Activate PDP Context Request" to SGSN with its own APN.

• As this APN is not in DNS, DNS responds back with GRX DNS address.

• SGSN Queries GRX DNS.• GRX reverts back with Home DNS IP address. The Home DNS provides the right GGSN Address.

• GTP Tunnel is established between Visited SGSN & Home GGSN.

• User accesses its services through home GGSN.

• SGSN Queries its DNS for GGSN IP for this APN.


ISP

GGSNFW

DNS

CG

VAS

BGR/FW

PLMN-B

GRX

GPRS Call Flow – OutRoamer

PLMN 1

SGSN

HLR MSSSGSN

• The APN resolution query comes to the Home DNS from visited SGSN.

• The Home DNS replies back with the correct GGSN IP Address.

• SGSN sends the “Create PDP Request to GGSN and GTP tunnel between Visited SGSN & Home GGSN is established.

• User accesses its services through home GGSN.

GPRS Roaming - ICR


Intra Circle Roaming refers to enabling the same services to the subscriber belonging to a PLMN while moving in another PLMN in same telecom license service area.

•This uses few specific features in the SGSN which are;• EPLMN (Equivalent PLMN) – With this feature, the defined PLMN

is treated as Home Equivalent PLMN. Because of this, the Routing Area Update procedure is used to update the location in visited SGSN rather than normal Cell Reselection/Attach procedure.

• Roaming Restriction: With this feature, only a defined combination of RAs (Routing Areas) & IMSIs can be allowed for Location Update in the SGSN.

•As in normal Roaming Scenarios, normal GT routing (Through GMSC) is used for GPRS Location Update. i.e. SS7 connectivity of SGSN with the Remote HLR is through GMSC only.•A connectivity between Home GN (SGSN/GGSN) network & Visited GN (SGSN/GSN) network is required.

GPRS - IntraCircle Roaming


GRX Cloud

GRX Cloud

Operator A Operator B

DNS Query

GPRS Traffic

BGR BGR

DNS DNS

GGSN

SGSN

GGSN

SGSN

• Existing GRX link is used for the connectivity between two GN Networks. • The DNS query goes through GRX connectivity.• The GPRS Traffic also goes through the same GRX connectivity.

• No Additional configurations are required in DNS for ICR partner.• Since in ICR scenario, the data traffic is expected to be on the higher side, cost incurred

by both the operators on GRX connectivity will go on the higher side.

GN Connectivity – GPRS IntraCircle RoamingThrough GRX


GRX Cloud

GRX Cloud


DNS Query

GPRS TrafficBGR BGR

DNS DNS

GGSN

SGSN

GGSN

SGSN

• Existing GRX link is used for the connectivity between two GN Networks but for DNS query only.

• The DNS query goes through GRX connectivity.• The BGRs of the both the operators are directly connected using secured tunnels.• The GPRS Traffic goes through this Secured link between two operators.• No Additional configurations are required in DNS for ICR partner.• This saves the cost of both the partners towards the GRX connectivity.

GN Connectivity – GPRS IntraCircle RoamingPartial GRX


GRX Cloud

GRX Cloud


DNS Query

GPRS TrafficBGR BGR

DNS DNS

GGSN

SGSN

GGSN

SGSN

• GRX Links is not required for any purpose of ICR Roaming scenarios. • The DNS is configured with the APNs of ICR partner with their corresponding GGSN Ips.

• The APNs get directly resolved by visited DNS.• The BGRs of the both the operators are directly connected using secured tunnels.• The GPRS Traffic goes through this Secured link between two operators.• This saves the cost of both the partners towards the GRX connectivity.

GN Connectivity – GPRS IntraCircle RoamingDirect Connectivity – Preferred Mode

Operational Issues


Location Update: (When the LU is not happening in SGSN)•Bring the handset into Always Online Mode.

- G, E or Dotted Arrows appear on the handset screen.•If not check for some other number belonging to same PLMN in some other area of the same SGSN.

- If issues persists in the other numbers also in different areas, check the GT routing in SGSN.

- If at other place, same PLMN sim is working• check the Services on that Sim card.• Check GPRS services in that cell (BTS Site). The services in the cell can be

checked by using the home SIM in the same area.

ICR – Operational Issues

PDP Establishment: (When Location Update is successful.)•Check for the services of that number in SGSN profile.•If services are defined for that APN,

- Check for the APN resolution for same PLMN through SGSN.•If APN does not get resolved in the SGSN,

- check the DNS entries for that APN in the specific PLMN Zone.•IF DNS Entries & Servcies are OK, Check for the connectivity between Visited SGSN and Home GGSN.In some cases, it has also been observed that the OSPF routing malfunctions in the FW and losses the connectivity with remote Gn Network.


Throughput Issue: (When PDP is through)•The visited Subscriber is not able to access the throughput in visited area.•Check for the Services with the Home number in the same area.•If expected throughput is observed with Home Number,

- Check the QoS of the subscriber profile.- Check for the Inter Connectivity link utilization.- Check for the errors in this link.- Check the ISP BW of the visited PLMN.

•If expected throughput is not observed using home number also,- Check the services in other area with the Home Number.

•If services are OK in other areas, Get the previous area checked for the RF/Gb Resources.•If expected throughput is not observed in other area also using home number also,

- Check for the Gb Utilization in the areas.- Check for the PAPU Throughput Utilization.- Check for the PAPU CPU Utilization.- Check for the FW/Switch CPU Utilization.

ICR – Operational Issues

The connectivity between the two operators is very important wrt to availability & Utilization for the proper services between the ICR partners.

Thank You !!!!

gprs 3g roaming

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