Section 2: Section Title

1
Control Plane Roaming LBS Roaming Meeting, San
Francisco November 28, 2006 Revised Version
2
Control Plane Overview

• Different LBS technology than the User Plane
• Uses the SS7/IS-41 network instead of packet
  data networks
• Control Plane defined in TIA/3GPP2 standards
  (IS-881/X.S0002)
• Standards include roaming architecture
• A few CP deployments out there, with a few more
  on the way
• Growing number of Control Plane enabled mobiles
• Control Plane roaming is important and seems
  straightforward

3
Control Plane Architecture and Interfaces
HLR
L2
LCS Client
MPC
E3
L1
Base Station
MS
E12
MSC / BSC
E5
PDE
4
IS -881 Non-Roaming Call Flow
5
IS-881 Registration (with MPCAddr)
6
IS-881 Roaming Call Flow
7
Issues with Control Plane Roaming

• Most operators
• Dont comply entirely with IS-881
• Use a Roaming Service Provider (RSP)

8
Non-compliance with IS-881

• Operators have not implemented IS-881 entirely
• MPCAddr not delivered in REGNOT
• Operators using LOCREQ/SMSREQ instead of LPREQ
  from H-MPC HLR query
• This avoids the need to upgrade the HLR
• IS-881 specifies L3 interface to use IS-41
• Operators have not implemented L3 interface yet
• It is feasible to use an RLP-like IP interface
  instead of a standards based L3 interface
• H-MPC maps MSCID of MSC from LOCREQ/SMSREQ to IP
  address of V-MPC

9
RSPs and CRXs

• Roaming Service Providers (RSPs)
• Are in the business of facilitating roaming
• Provide an interconnection point for operators
  SS7/IS-41 networks, settlement, and other value
  adds
• Most operators use RSP services
• CDMA Roaming eXchange Providers (CRXs)
• Facilitate packet data roaming
• Provide a central exchange point for IP data
  traffic, settlement and other value adds
• Most operators use CRX services
• RSPs/CRXs Aicent, Syniverse, VeriSign

10
Expected Control Plane Roaming Architecture
Visited Operator
Home Operator
RSP
MSC/VLR
HLR
HLR
IP Network (L3)
H-MPC
H-MPC
V-MPC
V-PDE
LCS Client
IS-41 Signaling
IP Traffic
11
RSP Issue

• Most operators prefer to use RSP for roaming
• RSP provide peering point for SS7/IS-41 exchange
  between operators
• RSP provides intermediary HLR function
• During registration, home operator receives
  generic MSCID provided by RSP
• Home operator wont be able to map generic MSCID
  to correct V-MPC for L3 interface
• Also the message used on the L3 interface to
  invoke the V-MPC needs to pass the serving MSCID
  to allow the V-MPC to execute local IS-881
  procedures (e.g., invoke the serving MSC)

12
RSP Issue Illustrated

• MS registers, and RSP replaces MSC/VLR MSCID
  with generic RSP MSCID
• LCS Client queries H-MPC for roaming MS
• H-MPC uses LOCREQ/SMSREQ to receive MSCID (RSP
  HLR) from HLR
• H-MPC needs to map MSCID (RSP HLR) to the IP
  address of V-MPC
• Because MSCID is generic RSP MSCID, the H-MPC
  doesnt know where the V-MPC is

Visited Operator
Home Operator
MSCID MSC/VLR
RSP
MSC/VLR
HLR
MSCID RSP HLR
HLR
MSCID RSP HLR
IP Network (L3)
RSP HLR ?
H-MPC
H-MPC
V-MPC
V-PDE
LCS Client
13
RSP Issue Solution 1

• RSP provides the serving MSCID to home operator
• LCS Client queries H-MPC for roaming MS
• H-MPC uses LOCREQ/SMSREQ to receive serving
  MSCID from HLR
• H-MPC maps serving MSCID to the IP address of
  V-MPC
• H-MPC performs L3 transaction with V-MPC
  (passing serving MSCID)

Visited Operator
Home Operator
MSCID MSC/VLR
RSP
MSC/VLR
HLR
MSCID MSC/VLR
HLR
MSCID MSC/VLR
Visited Op 127.4.64.1
IP Network (L3)
127.4.64.1
H-MPC
H-MPC
V-MPC
V-PDE
LCS Client
14
RSP Issue Solution 2

• MS registers, and RSP replaces MSC/VLR MSCID
  with generic RSP MSCID
• H-MPC always creates IP connection (L3) with RSP
• RSP maps MS IMSI in L3 messaging to V-MPC IP
  Address
• RSP connects to V-MPC (passing serving MSCID)
  and provides response to H-MPC

Visited Operator
RSP
Home Operator
MSCID MSC/VLR
MSC/VLR
MSCID RSP HLR
HLR
MSCID RSP HLR
HLR
IMSI maps to V-MPC
IP Network (L3)
H-MPC
H-MPC
V-MPC
V-PDE
LCS Client
15
Solutions to Issues

• Full IS-881 compliance (works with RSP)
• Non-compliant IS-881 deployment solutions
• Full interconnection (dont use RSP)
• RSP solutions
• 1 - But pass serving MSCID (somewhat undermines
  the reasons for using an RSP)
• 2 - RSP performs proxy of L3 interface
• L3 interface
• Use IS-881 standards interface
• Use RLP-like L3 interface