Transcript Wireless and Mobile Network Architectures

Wireless and Mobile Network Architectures
VoIP Service for Mobile Networks
Chapter 16
03, 05,06
[email protected]
Network Computing LAB
김응도
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
 VoIP is considered as a promising trend in
telecommunication.
 Integrating mobile phone services with VoIP in particular
has become an important issue.
 Telecommunications and Internet Protocol
Harmonization over Network (TIPHON) specifies the
mechanism (i.e. a mediation gatekeeper) to provide the
service control functions for convergence of IP
networks, mobile networks, fixed wireless networks, and
PSTN.
 Several scenario are defined in TIPHON to illustrate
different ways of integrating IP and mobile networks.
 We use GSM as an example of mobile networks to
describe mobile/IP integration, where the mobile
signaling protocol is GSM MAP
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
TIPHON IP and mobile integration scenario.
IP Network
Mobile
Network
(VLR)
Mediation
Gatekeeper
VLR
BSC/BTS
MSC
HLR
http://netcom.kw.ac.kr
Gateway
Signaling
Gateway
BSC/BTS
Kwangwoon Univ.
Wireless and Mobile Network Architectures
contents
 GSM on the Net
 The iGSM Wireless VoIP Solution


The H.323 Network
The iGSM Architecture
 iGSM Procedure and Message Flows



Registration
Deregistration
Call Delivery to the IP network
 Implementation Issues


Reducing GSM Tromboning Effect
Misrouting Due to User Mobility
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
GSM on the Net
 Based on a concept similar to TIPHON, Ericsson’s
GSM on the Net utilizes a corporate intranet to
integrate an enterprise communication network with the
public GSM network
 This system supports both terminal mobility and user
mobility.
Terminal mobility : whereby a terminal can be moved around the
service area without losing contact with the system
 User mobility : whereby, using various types of terminals, a user can
move around the service area without losing contact with the system

 Each of the elements in the corporate network is
connected to a switched Ethernet with 10Mbps
bandwidth.
 They communicate with each other using the H.323
family of protocols.
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
GSM on the Net
Corporate offices
GSM Network
IP Phone/PC
Access
node
VLR
BSC/BTS
MSC
HLR
http://netcom.kw.ac.kr
Intranet
Gateway
Service
node
GSM/BTS
Kwangwoon Univ.
Wireless and Mobile Network Architectures
GSM on the Net
 Service node




Enables user mobility.
Controls calls among different types of terminals.
Translates addresses between PSTN and GSM on the Net.
Provides authentication, resource management, least-cost
routing, and administration for user identity and service profile.
 Access node



Resembles the MSC, VLR, and BSC to manage connection,
mobility, and radio resources.
Does not provide trunks; instead, controls only the
communication between the endpoints.
Consist of network access controller (NAC), and the radio
network server (RNS)
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
 GSM/BTS

Provides wireless access for a GSM MS in the IP network
 Gateway


Provides interfaces between GSM on the Net and other
networks (particularly the GSM network)
Consists of both voice and SS7 gateway functionality
 Terminal equipment

Can be an IP phone, PC, DECT phone, or GSM mobile
station.
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
The iGSM Wireless VoIP soultion
 We proposes the iGSM service that realizes another
TIPHON scenario supporting user mobility for GSM
subscribers to access VoIP service.
 GSM Network에서 GSM 서비스를 받던 사용자가 GSM
MS없이 IP Network으로 이동하여 자신의 MSISDN 으로
수신되는 전화를 받기 위해서 H.323 terminal을 사용할 수
있다.
 iGSM solution is different from GSM on the Net


Unlike GSM on the Net, iGSM is a value-added service to
the public GSM Networks.
iGSM network does not introduce wireless access equipment
in the IP network; rather, iGSM service is implemented using
standard platforms(general IP gateway / gatekeeper)
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
The iGSM Wireless VoIP soultion
 We describe the iGSM architecture and the protocols
for location update and call delivery.
 We discuss how the tromboning effect in standard
GSM systems can be avoided when accessing the IP
Network.
 We investigate the problem of misrouting a call
caused by user mobility.
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
H.323 Network
The iGSM system consists of the GSM and H.323 (IP) networks.
ITU-T H.323 covers the technical requirements for multimedia communications
Over packet-based networks that may not provide a guaranteed quality of
service
MP
MP
MC
H.323
Gatekeeper
MC
MC
ISDN
H.323
Gateway
LAN
PSTN
MC
H.323
Multipoint
Control Unit MP
H.323 Terminal
(phone or PC)
http://netcom.kw.ac.kr
<H.323 Architecture>
Kwangwoon Univ.
Wireless and Mobile Network Architectures
H.323 architecture
 Terminal

Customer premises equipment (CPE) that provides audio, video,
and data communications capability for point to point or
multipoint conferences in the H.323 network
 Gateway

Perform call control function and the communication protocol
translation mechanism between an H.323 endpoint and
endpoint of a circuit-switched network, such as ISDN,PSTN
 Gatekeeper



Optional in an H.323 network
May be colocated with a terminal, gateway, or multipoint
control unit
Provide these functions that address translation, admissions
control, bandwidth control, and zone management.
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
H.323 architecture
 Multipoint control unit (MCU)

Utilizes multipoint controllers to support multipoint
conferences
 Multipoint controller


Provides control functions to support conferences between
three or more endpoints in a multipoint conference.
Every MCU contains an MC.
 Multipoint process (MP)


Receives audio, video, and data streams from the
endpoints involved in a multipoint conference.
An MP is optionally included in a gateway, gatekeeper, or
MCU
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Kwangwoon Univ.
Wireless and Mobile Network Architectures
The iGSM Architecture
 iGSM gateway is implemented to perform two major
functions besides the standard H.323 mechanisms


GSM MAP and H.225 RAS (registration, admission, status)
protocol translation.
GSM/PSTN/IP call setup and release
 An iGSM gatekeeper is implemented to serve as the
VLR for iGSM subscribers who visit the IP network.



Every iGSM gatekeeper is assigned an ISDN number that can
be recognized by the HLR.
The iGSM gatekeeper maintains a list of all iGSM subscribers.
Based on this list, the gatekeeper performs MSISDN-totransport address translation and GSM roaming management
procedures for the iGSM subscribers.
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
iGSM architecture
MS
BTS/BSC
H.323 Terminal
VLR
IP network
MSC
iGSM
Gateway
GSM
HLR
Gatekeeper
iGSM VLR
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
iGSM procedures and Message Flows
 Every iGSM subscriber has a record in the datebase.







MSISDN of the MS
Transport address of the H.323 terminal for the subscriber in
the IP network.
Password of the iGSM subscriber
HLR address of the iGSM subscriber
IMSI of the MS
User profile which indicates the service features and
restrictions the iGSM subscriber
Presence indication of the iGSM subscriber in the IP network.
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
H.323
수신된
iGSM
HLR은
terminal
registration
deregistration을
IMSI를
Pass를
통해
turn
통해
과정을
HLR은
on
user
validate

oldVLR에
profile을
끝낸다
user검사
profile
알린다
기록
 수정
 
iGSM gatekeeper는
user
moves
MSISDN
password
입력
MAP_INSERT_SUBSCRIBER_DATA
IRQ(InsSubDataAck)
MAP_UPDATE_LOCATION_ack
MAP_CANCEL_LOCATION
fromIRQ(UpdateLoc,
theand
GSM
network
IMSI,
VLR, MSC
(user
num)
profile)
을
iGSM
을 전달
iGSM
전달  전달, passwd)

Gatekeeper로
to oldVLR로
the IPgateway로
network
RASgateway로
RRQ(MSISDN
전
송
iGSM
oldVLR은
Gateway
Gateway는
iGSMGSM
IRR(InsSubsData,
MS의
ACK를
RFC(Registration
MAP으로
기록을
HLR로
지운다
변환
전송
user
HLR로
Comfirm)
profile)
MAP_UPDATE_LOCATION(IMSI,
을 gatekeeper로 전달
를
전송
VLR, MSC num)
전송
Registration
MS
BTS/BSC
1
H.323 terminal
VLR
MSC
7,8
IP network
3
4
GSM
HLR
5
2
3
4
6
http://netcom.kw.ac.kr
iGSM
Gateway
6
5
Gatekeeper
iGSM VLR
Kwangwoon Univ.
Wireless and Mobile Network Architectures
Message flow for iGSM registration
H.323
Gatekeeper
terminal
(new VLR)
PRQ(MSISDN)
2
IRQ
3
4
5
IRR
Gateway
3
4
6
RCF
IRR
http://netcom.kw.ac.kr
6
Old VLR
MAP_UPDATE_LOCATION
MAP_INSERT_SUBSCRIBERDATA
7
IRQ
5
6
HLR
MAP_CANCEL_LOCATION
MAP_CANCEL_LOCATION_ack
8
MAP_INSERT_SUBSCRIBER_DATA_ack
MAP_UPDATE_LOCATION_ack
Kwangwoon Univ.
Wireless and Mobile Network Architectures
deregistration
 In this case of the iGSM gatekeeper is the “OLD VLR”
 iGSM subscriber moves from the IP Network to the GSM Network.
Gatekeeper
HLR
Gateway
H.323 terminal
(old VLR)
MAP_CANCEL_LOCATION(IMSI)
1
1
IRR (CanLoc, IMSI)
1
2
IACK (CanLocAck)
URQ(unregister Request)
UCF(Unregister
Confirmation)
2
MAP_CANCEL_LOCATION_ack
2
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
Call delivery to the IP network
12
11
HLR
3
3
2
H.323 terminal
8
2
7
iGSM
Gateway
GSM
Gateway
MSC
4
IP network 10
6
9
5
3
Gatekeeper
2
iGSM VLR
1
Originating Switch
1
PSTN
http://netcom.kw.ac.kr
iGSM가입자의
MSISDN입력(0-936105401)
GMSC
query
the
location
ofatIAM
iGSM
subscriber
Getekeeper는
Gateway
H.323
얻은
iGSM
Ringing
MSRN을
subscriber의
subscriber가
terminal은
tone
sends
is
통해
Gateway와terminal의
the
generated
gatekeeper와
GMSC는
MSRN을
수신하면,
H.225(Q.931)
수신한
H.323
the
ARQ
message를
H.323
Set-up
gateway는
주소를
terminal은
and ACF
msg
통
0to: HLR
special
digit
,
936
:
GMSC


MSISDN을
통해
HLR은
가입자가
IP
해
를
RAS
terminal
MSRN
H.323
Connect

terminal에
생성
H.225
message
 RAS
Alerting
전달
LCF(Location
를

gateway에
message
CallACF
Proceeding
Confirm)
isReject)
전달
sent
to
message를
통하여
ARQ
(Admission
Gateway와
교환(이때
Request)
trunk
ARJ(Admission
설정
and
Originating
switch
send
SS7
IAM
message
to
network에
있음을
확인

HLR send
를
(Admissions
gateway
gateway로

gateway는
Confirm)
전달
 originating
gateway는
exchange
Alerting
message를
 iGSMreply
(충분한
수신
SS7
가능
ANM로
routing
변형되어
정보를
받았다)
message
switch에
전달
GMSC
gateway(MAP_PROVIDE_ROAMING_NUMBER)
MAP_PROVIDE_ROAMING_NUMBER_ack
gatekeeper로부터
대화
SS7 ACM
시작message로
MSRN을
변형하여
통해 GMSC에
terminal의
with
전달

Gateway
LRQ(Location
Request)를
MSRN
을 HLR에
전달 transport
HLR은
GMSC에
call-signaling
channel
address 획득
Gatekeeper에
전달.
MAP_SEND_ROUTING_INFORMATION_ack
Kwangwoon Univ.
Wireless and Mobile Network Architectures
Message flow for iGSM call setup
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
Implementation Issues
 iGSM을 구현함에 있어서 고려해야 할 두가지 이슈
 Reducing GSM Tromboning Effect
 Investigating misrouting of user mobility
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
Reducing GSM Tromboning Effect
 Tromboning occurs when the caller and the called MS
are in the same city but the GMSC is in another city.
 Both GSM MSCs and iGSM gateways can serve as
GMSCs for iGSM subscribers


If an iGSM subscriber is assigned a GSM MSC as his GMSC,
call delivery follows the procedure iGSM call delivery and
tromboning occurs.
If an iGSM subscriber is assigned a iGSM gateway as his
GMSC, call delivery tromboning can be avoided
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
Reducing GSM Tromboning Effect
iGSM IP network
PSTN
iGSM user
Switch
2
IP Network
iGSM user
iGSM
5
Gateway
1
3
caller
iGSM IP network
iGSM 2
Gateway
4
Gatekeeper
iGSM VLR
<PSTN-to-IP Cal Setup>
1
caller
Gatekeeper
iGSM VLR
<IP-to-IP Cal Setup>
 Two kinds of subscribers are anticipated in iGSM


The GMSCs of the iGSM subscribers are standard GSM
MSCs. In this case, the subscibers typically subscribe to
the standard GSM services at the beginning, and determine
to include the iGSM service later
The GMSC of the subscribers is the iGSM gateway. In this
case, the subscribers typically subscribe to the iGSM
service from the beginning
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
Reducing GSM Tromboning Effect
 The first kind of subscribers



call delivery follows the standard GSM procedure
A subscriber visits the IP network, tromboning may occur
as in traditional GSM networks
The GSM operator would prefer this scenario if the iGSM
gateway and gatekeeper are owned by other ISPs.
 The second kind of subscribers


Call-delivery tromboning avoided when the subscriber visits
the IP network.
The GSM operator is likely to own the iGSM gateway and
gatekeeper
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
Misrouting Due to User Mobility
 To support user mobility, the subscriber needs to
explicitly perform registration to inform the system in
which location area he resides when the terminal has
been changed.
 Missing  call deliveries may be misrouted
 This problem can be eliminated if the subscriber
always turns off the MS when he moves to the H.323
terminal
 The turn-off action results in a GSM detach message,
which deregisters the MS.
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
Misrouting Due to User Mobility
4
1
GSM MS
2
IP Phone
MSC
VLR
A
p
GSM
VoIP
Gateway
HLR
3
p B
A
GSM
VLR
B
p
VoIP network
step1
step2
step3
http://netcom.kw.ac.kr
Kwangwoon Univ.
Wireless and Mobile Network Architectures
Misrouting Due to User Mobility
 The misrouting problem is avoided if the subscriber
explicitly or implicitly registers with the GSM MS step3.
 Implicit registration occurs in two cases


The subscriber originates a call. In this case, VLR A finds that
the VLR record for the subscriber does not exit. VLR A will
ask the MS to perform a registration operation, as described
in the VLR failure restoration procedure
The subscriber moves to another LA in the GSM network.
Registration is automatically initiated by the GSM MS.
 Both case, after the HLR has modified the subscriber’s
record, it also cancels the subscriber’s VLR record in
VLR B
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Kwangwoon Univ.