Study on Application of
Softswitch in Wireless Networks
組員:陳中賢 陳俊豪 陳億宗 吳青坡
Outline
Introduction
Overview of NGN Based on Softswitch Network Architectures of Softswitch- Involved Wireless Networks
A Typical Call Scenario in Softswitch- Involved Wireless Networks
Introduction
NGN is proposed as an integrated architecture involving various legacy networks
UMTS has defined a migration to a packet- switched core network
Utilizing softswitch to migrate from GSM to both UMTS and NGN
2G Î 3G
GSM Î UMTS+NGN
Overview of NGN Based on Softswitch
NGN 3 characters
an open network architecture
decomposed Î flexible
a service-oriented network
call control function 分出 service control function Î/ new & inter-network service
a packet-switched backbone network
Connect though gateway
Overview of NGN Based on Softswitch
NGN 3 functional layers
Transport layer
Transport of all kinds of traffics across the NGN
Signaling
Any kinds of media
Call control & Signaling layer Í Softswitch
Call Control based on signaling message received from Transport layer
Handle establishment and teardown of media connections by controlling components in the Transport layer
Overview of NGN Based on Softswitch
Service & Application layer
Provides the control, logic and execution for the services or applications
Softswitch is the core element of the NGN in the Call Control & Signaling Layer
NGN 3 functional layers
Overview of NGN Based on Softswitch
Softswitch 3 Functions
Call control function with various signaling protocol
ISUP, H.323, SIP, Megaco/H.248
Provides the call control portion of the legacy switch in circuit- switched network
Control media gateway
Transform of the media between packet-switch network and circuit-switched network
Provides the call switching portion of the legacy switch in circuit-switched network
Overview of NGN Based on Softswitch
Provide necessary control abilities to the service plane elements
Implement various services and applications
Service plane elements include Application Sever and Media Server
GSM Introduction
Mobile Station
無線電傳送器,顯示螢幕和數位訊號處理器, SIM卡
手機都有一個IMEI, SIM卡上有IMSI
Base Station Subsystem
兩個部分
Base Transceiver Station(BTS)
Base Station Controller(BSC)
BSC管理一或多個BTSs
BSC控管radio channel setup,frequency hopping和 handovers
BSC是MS和MSC之間的連接
GSM Introduction
Network and Switching Subsystem(NSS)
Mobile services Switching Center(MSC)
Network Subsystem中心元件
控管行動電話用戶的功能(註冊,認証,位置更新,
handovers和漫遊)
MSC可與PSTN 或 ISDN間用ITUT Signaling System Number 7 (SS7)溝通
Visitor Location Register(VLR)
Home Location Register(HLR)
Authentication Center(AUC)
Operations and Maintenance Center(OMC)
GSM Introduction
Mobile Station透過radio interface Um與 Base Station Subsystem相互通訊
Base Station Subsystem以A Interface連結 到Mobile Switching Center再與Network and Switch Subsystem相聯結
GSM Introduction
Network Architectures of Softswitch- Involved Wireless Networks
Softswitch-involved GSM network
Softswitch-involved UMTS R99 network Softswitch-involved UMTS R4 network
Network Architectures of Softswitch-
Involved Wireless Networks
Softswitch-involved GSM network
NSS divides into IP NSS, Circuit NSS Softswitch, MG and SG in IP NSS can serve as a MSC replacement for GSM networks
Circuit NSS includes all the remaining circuit-based elements
MSC, HLR and AC
Softswitch & GMSC coexist
Softswitch-involved GSM network
Softswitch control the MG and SG by Megaco protocol
Must provide extra functionalities for Wireless Network
Mobility Management(MM)
Radio Resource(RR)
Softswitch-involved GSM
network
Softswitch-involved UMTS R99 network
Differences between GSM and UMTS R99
MS Î UE(User Equipment)
BSS Î RNS(Radio Network Subsystems)
BTS Î Node B
BSC Î RNC(Radio Network Controller)
Above changes are all in BSS
Control the RNC with lu-cs interface
Control the BSC with A interface
Since the NSS keeps the same, things are mostly unchanged to softswitch
lu-cs interface needs to be concerned
Softswitch-involved UMTS R99
network
Softswitch-involved UMTS R4 Network
Differences between UMTS R99 and R4
MSC Î MG + MSC server(IP)
Softswitch = MSC server
ERICSSON Softswitch in
Mobile Networks White Paper
A Typical Call Scenario in Softswitch- Involved Wireless Networks (0/5)
Terminations
Logical entities on an MG that act as sources or sinks of media streams.
Contexts
An association between a number of
terminations for the purposes of sharing
media between those terminations.
A Typical Call Scenario in Softswitch- Involved Wireless Networks (1/5)
BSS Softswitch MG PSTN
1.Setup
2.Call Proceeding
3.Megaco : Add Request Context($),
Termination($) 4.Add Reply, (C1),(T1)
‧Softswitch receives Setup Message from MS
‧Softswitch requests the MG based on call-routing to establish a new context and termination
MS
A Typical Call Scenario in Softswitch- Involved Wireless Networks (2/5)
BSS Softswitch MG PSTN
‧Softswitch requests the BSS to set up a traffic channel over the radio interface with MS.
5.Allocate Channel
8.Allocate Complete 6.Assignment Cmd
7.Assignment Comp
MS
A Typical Call Scenario in Softswitch- Involved Wireless Networks (3/5)
BSS Softswitch MG PSTN
‧Requests the MG to add a new termination to C1.
‧A path is created from one side of MG to the other.
9.Add Request, (C1), ($) 10.Add Reply, (C1), (T2)
11. IAM
12. ACM 13. Alerting
MS
BSS Softswitch MG PSTN
‧Modify the context established on the MG.
‧Ring-back tone Î Full two-way media path
15.Modify Request,(C1),(T1) 16.Modify Reply, (C1), (T1) 17.Modify Request,(C1),(T2) 18.Modify Reply, (C1), (T2)
MS
A Typical Call Scenario in Softswitch- Involved Wireless Networks (4/5)
14. ANM
BSS Softswitch MG PSTN
20.Connect Ack
19. Connect
‧Softswitch sends a Connect message to the MS
‧MS responds with a Connect acknowledge MS
A Typical Call Scenario in Softswitch-
Involved Wireless Networks (5/5)
Conclusion
The 3G wireless networks and the NGN have similar objectives and architectures.
So Applying softswitch into the wireless
networks not only helps the revolution from 2G to 3G, but also provides a smooth
migration towards the NGN.
As the wireless network keeps evolving, the softswitch may be further decomposed into more dedicated functional entities, as
suggested in UMTS Release 5.
References
Qiang Wei, Sen Su, Junliang Chen, “Study on Application of Softswitch in Wireless Networks”,
Communication Technology Proceedings
, 2003. ICCT 2003.International Conference
on Vol.1, 9-11 April 2003 Page:127-130 vol.1“Softswitch in Mobile Networks”,
Ericsson
White Paper, April 2005.3GPP, GSM Specifications: http://www.3gpp.com 3GPP, UMTS Specifications: http://www.3gpp.com