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Softswitch in Wireless Networks

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(1)

Study on Application of

Softswitch in Wireless Networks

組員:陳中賢 陳俊豪 陳億宗 吳青坡

(2)

Outline

Introduction

Overview of NGN Based on Softswitch Network Architectures of Softswitch- Involved Wireless Networks

A Typical Call Scenario in Softswitch- Involved Wireless Networks

(3)

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

(4)

Overview of NGN Based on Softswitch

NGN 3 characters

„

an open network architecture

Š decomposed Î flexible

„

a service-oriented network

Š call control function 分出 service control function Î/ new & inter-network service

„

a packet-switched backbone network

Š Connect though gateway

(5)

Overview of NGN Based on Softswitch

NGN 3 functional layers

„ Transport layer

Š Transport of all kinds of traffics across the NGN

„ Signaling

„ Any kinds of media

„ Call control & Signaling layer Í Softswitch

Š Call Control based on signaling message received from Transport layer

Š Handle establishment and teardown of media connections by controlling components in the Transport layer

(6)

Overview of NGN Based on Softswitch

„

Service & Application layer

Š 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

(7)

NGN 3 functional layers

(8)

Overview of NGN Based on Softswitch

Softswitch 3 Functions

„ Call control function with various signaling protocol

Š ISUP, H.323, SIP, Megaco/H.248

Š Provides the call control portion of the legacy switch in circuit- switched network

„ Control media gateway

Š Transform of the media between packet-switch network and circuit-switched network

Š Provides the call switching portion of the legacy switch in circuit-switched network

(9)

Overview of NGN Based on Softswitch

„

Provide necessary control abilities to the service plane elements

Š Implement various services and applications

Š Service plane elements include Application Sever and Media Server

(10)

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

Š Base Transceiver Station(BTS)

Š 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

(11)

GSM Introduction

Network and Switching Subsystem(NSS)

„ Mobile services Switching Center(MSC)

Š Network Subsystem中心元件

Š 控管行動電話用戶的功能(註冊,認証,位置更新,

handovers和漫遊)

Š 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)

(12)

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

(13)

GSM Introduction

(14)

Network Architectures of Softswitch- Involved Wireless Networks

Softswitch-involved GSM network

Softswitch-involved UMTS R99 network Softswitch-involved UMTS R4 network

(15)

Network Architectures of Softswitch-

Involved Wireless Networks

(16)

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

(17)

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)

(18)

Softswitch-involved GSM

network

(19)

Softswitch-involved UMTS R99 network

Differences between GSM and UMTS R99

„ MS Î UE(User Equipment)

„ BSS Î RNS(Radio Network Subsystems)

Š BTS Î Node B

Š 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

(20)

Softswitch-involved UMTS R99

network

(21)

Softswitch-involved UMTS R4 Network

Differences between UMTS R99 and R4

„

MSC Î MG + MSC server(IP)

Softswitch = MSC server

(22)

ERICSSON Softswitch in

Mobile Networks White Paper

(23)

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.

(24)

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

(25)

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

(26)

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

(27)

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

(28)

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)

(29)

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.

(30)

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

參考文獻

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