Evolution of IP in Wireless Networks
Antti Nuopponen
T-110.456 Next generation cellular networks
Agenda
● Short overview of current wireless networks
● All-IP UMTS
● UMTS release 6
● Evolution of cdma2000 to All-IP
● Summary
What we have today
● GSM
● Offers good enough speech service
● GPRS / EDGE
● Offers packet data service that is usable with low bandwidth applications
● cdma2000
● Services like in GSM / GPRS /EDGE
● WLAN
● Offers fast packet data service
What we have today – UMTS
● Offers a new radio access network UTRAN
● More subscribers can be served
● Data packet service similar to GPRS with more bandwidth
● Security build on GSM
● Mutual authentication
● Open encryption algorithms with long keys
● Network and application security separated
UMTS release 99 network
(Figure from A. Ahtiainen 21.1.2004)
All-IP UMTS network (release 5)
● IP Multimedia Subsystem (IMS)
● Provides traditional telco services on top of IP
● Services are based on Session Initiation Protocol (SIP)
● VoIP, presence services, instant messaging etc.
● Strong user authentication in addition to network
authentication – makes it possible to access IMS from different access networks
● Traditional Internet services attached to IMS
● IMS provides security and roaming services that are not typically provided by the service it self
● Allows fast deployment of new services
All-IP UMTS network (2)
● Minor modifications to PS core network for QOS support
● High-Speed Downlink packet access (HSDPA)
● Provides up 10Mbps on the downlink
● User bit rates in large macrocell can exceed 1Mbps
● User bit rates in small microcell can exceed 5Mbps
● Supports both real-time and non-real-time QOS classes
SIP session management
● Call session control function (CSFS) and proxy CSFS are the main components
● Session opening
● Contact to P-CSFS in visited network
● P-CSFS forwards signaling to home network CSFS
● Home CSFS authenticates user using Home Subscriber server (HSS) which also generates session keys
● Service control always in home network
➔ Same services always available
All-IP UMTS network layout
(Figure from A. Ahtiainen 21.1.2004)
UMTS release 6
● Radio enhancements
● MIMO antennas
● Terminal power saving features
● Improvements in inter-system and inter- frequency measurements
● Optimized voice communication
● RTP, UDP, and IP headers not transmitted between MS and BSC
● Additional signaling to transfer requirer information
UMTS release 6
● Support for multicast broadcasts and multicast services
● 3GPP / 3GPP2 IMS harmonization
● WLAN / UMTS interworking
● Emergency calls in packet network
● Radio network sharing between operators
● New services
● Presence, instant messaging, conferencing
UMTS-WLAN interworking
● Open coupling
● Only billing is shared
● No interaction between networks
● Loose coupling
● WLAN authentication is integrated into UMTS network
● Quick to implement – fast market entry
● Handovers not possible
UMTS-WLAN interworking
● Tight coupling
● WLAN connected to UMTS core using Iu interface
● Makes WLAN to UMTS handovers possible
● WLAN provides new access method to UMTS
● User authentication integrated into UMTS core network using EAP-SIM and Radius / Diameter between AP and AAA server
UMTS security
● UMTS release 99
● Provides mutual authentication
● Attack based on faking a base station are not possible
● Provides signaling integrity protection
● Uses open algorithms with long keys
● All-IP UMTS (release 5)
● Access network authentication as in release 99
● Additional authentication to IMS using SIP
All-IP UMTS security
● Network security
● Circuit switched networks relied on physical security
● IP protocols and integration to Internet poses a new set of threats
● IMS data security relies on PS network physical security
● Applications can use own security mechanism
such as IPsec or SSL since they operate on top of IP
Traditional telco services over IP
● Speech
● Call setup using SIP
● Voice over IP (VoIP)
● Optimizations in radio link
● SMS
● Can be replaced with instant messaging applications
Billing challenges
● In 2G all services provided by operators and billing based on service usage
● 2.5G made 3rd party services possible
● With All-IP 3G everybody can offer services to mobile users
● In 3G operators might end up selling bandwidth
➔ Operators need a new billing model
● Amount of billing tickets increases significantly
➔ Challenges to billing servers
Billing alternatives
● Data amount based billing
● Marginal are significantly lover that in current GSM
● Content based billing
● Operator looks into IP payloads and charges bases on content
● Internet access only through proxies
● Won't work on a long run
● I-Mode type of revenue sharing
3GPP2 evolution
● Enhancement of the cdma2000 radio interface
● 1xEV-DO – data only, 2.4Mbps (peak)
● 1xEV-DV – data and voice, 3.12Mbps (peak)
● Evolution of core network at the IP level
● Coexistence of CS and PS networks makes over-the-air access performance suboptimal
● Two evolution models to all IP
● Sequential phase evolution
● “Mix and match” phase evolution
● Service evolution
3GPP2 All-IP NAM
● CDMA2000 All-IP network architecture model (NAM) based on three major protocols
● SIP for control of multimedia sessions
● DIAMETER for AAA
● Mobile IP (both IPv4 and IPv6) for mobility support in core network
All-IP NAM – Architecture
● Independence from lower layers
● Phased migration
● Radio efficiency
● Improvements of reliability and QOS
● User / control plane separation
● IP migration
● Consist of three main functionalities
● Access, network, and multimedia
All-IP NAM access functionality
● Consist of three components; Access Gateway (AGW), Access network (AN), and AAA
● Hides access-specific aspects to the other functionalities
● Contains layer 2 specific access functions
● Access Network
● Contains BTS, BSC, MM, and PCF
● Performs mobility management
● Access Gateway
● Supports different access network technologies
● Provides foreign agent service (Mobile IPv4)
All-IP NAM network functionality
● Purpose is to provide end-to-end IP connectivity between MS and other IP entities
● Access functionality appears as a link layer to network functionality
● Controls access functionality through core QoS manager
● Functionality provided by core QoS manager, IP home agent (HA), AAA, and subscription QoS manger
All-IP NAM multimedia service application control functionality
● Implements the call control and services /
applications that provide the multimedia services
● Access independent
● Works on top of end-to-end IP provided by network functionality
● Services can reside inside or outside of the operator's network
Summary
● The killer application for fast cellular networks is still missing
● GSM / EDGE technologies will continue to live in rural areas
● UMTS deployment and wide use not foreseeable in a near future
● Cellular networks are evolving towards packet switched IP networks
➔ Cellular networks will merge into the Internet
