Transcript 12._3G_WLAN_Internetworking_architectures

EA C451
BITS Pilani
Pilani|Dubai|Goa|Hyderabad
Vishal Gupta
BITS Pilani
Pilani|Dubai|Goa|Hyderabad
Agenda: 3G –WLAN Internetworking
Architectures
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
• Modern cellular networks are capable of providing better mobility,
whereas WLANs are known for their relatively higher bandwidth.
• Ubiquitous data services and very high data rates across heterogeneous
networks may be achieved by the use of a WLAN as a complementary
technology to cellular data networks.
• The interworking mechanisms, are expected to be equipped with
integrated authentication, integrated billing, roaming, terminal
mobility, and service mobility.
• There are many architectures proposed. By and large, these proposed
integration architectures can be categorized as tight coupling, loose
coupling, and peer-to-peer networking (also referred as no-coupling).
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
Coupling Architectures
• The Tight Coupling Architecture
• The Loose Coupling Architecture
HLR
Loose coupling
point
Gr
Gc
Mobile
station
MS
Iu-ps
UTRAN
Gi
SGSN
Uu
MS
Um
GRPS
RAN
Gb
Gn/p
GGSN
External
Packet data
network
Gn/p
SGSN
Tight coupling
point
HLR:Home location register
SGSN:Serving GPRS support node
GGSN:Gateway GPRS support node
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Source:
Ch22BITS Pilani, Deemed to be University under
Section
3 of UGC Act, 1956
Tight Coupling
• With tight coupling the WLAN is connected to the 3GPP (GPRS) core
network in the same way as any other radio access network (RAN), such as
GPRS RAN and UMTS terrestrial RAN (UTRAN).
• In other words, an IEEE 802.11 WLAN is connected to the 3G cellular
core network via a Serving GPRS Support Node (SGSN) emulator.
• Both data and UMTS signaling are transported by the IEEE 802.11
WLAN to the 3G core network via an SGSN emulator.
• Thus, the IEEE 802.11 Basic Service Set (BSS) acts as another SGSN
coverage area to the UMTS core network.
• The WLAN data traffic goes through the GPRS core network before
reaching the external packet data networks.
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
Tight Coupling
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
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The key functional element in the system is the GPRS Interworking Function
(GIF), also referred to as an SGSN emulator.
The GIF is the function that makes the SGSN consider the WLAN as a typical
GPRS Routing Area (RA) composed of only one cell.
GIF and all interconnected WLAN terminals use a 48-bit IEEE 802 MAC
address.
The WLAN Adaptation Function (WAF) is the main component, which helps
the Mobile Node to identify the MAC address of the GIF.
There is a WAF implemented in every dual mode MN as well as the GIF for 3G
signaling and data exchange over the IEEE 802.11 WLAN.
The WAF also provides the following functions:
– Signaling the activation of WLAN interface as the MS enters a WLAN area.
– Discovering the MAC address of the GIF.
– Helping the SGSN page a mobile station over the Gb interface
– Transferring Logical Link Control (LLC) Protocol Data Units (PDU) from mobile
station to the GIF and vice-versa
– Supporting QoS by implementing transmission scheduling in the GFS and the MN.
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
Tight Coupling
Advantages of Tight Coupling:
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Since the WLAN and GPRS networks connect to the same (GGSN), IP addresses
are assigned by the same pool. Hence, the mobility across the two networks
do not require a change of an IP address.
Seamless service continuation across WLAN and 3G networks,
Less complicated mobility management mechanisms (since it follows
GPRS/UMTS mobility management mechanisms),
Ability to use the GPRS/UMTS Authentication, Authorization, and Accounting
(AAA) system,
Ability to use the GPRS/UMTS infrastructure for routing (e.g., core network
resources, subscriber database, billing systems),
Increased security (GPRS/UMTS security can be applied on top of WLAN security)
Common provisioning and customer care
Access to core GPRS/UMTS services (Short Message Service (SMS), locationbased service, Multimedia Message Service (MMS),
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BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
Tight Coupling
Drawbacks of Tight Coupling
• 3G core network interfaces are required to be exposed to WLAN, which is
a challenge as the two domains are likely developed and deployed
independently by different operators. This puts a strong limitation on the
actual commercial avail- ability of this kind of integration.
• Tight coupling architecture is primarily designed for WLANs owned by
cellular operators.
• Large volume of WLAN traffic will go through the 3G core network,
possibly making the latter a network bottleneck.
• WLAN needs to have a protocol stack compatible with that of the 3G
networks.
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
Loose Coupling
• A loosely coupled architecture transports UMTS signaling over the
IEEE 802.11 WLAN to the 3G core network, while data flows directly
to the IP based network.
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
Loose Coupling
Advantages
• This type of architecture imposes minimal requirements to modify current
WLAN standards, and allows for the flexibility and independence of
implementing individually different mechanisms within each network.
• It is the preferred solution for both the 3G and WLAN communities as it
allows the gradual deployment of hotspots with no or little modification
on the 3G networks.
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956
Loose Coupling
Drawbacks
• The 3G networks may need to be augmented with extra functionalities
such as Mobile IP for mobility management and AAA support.
• Since the 3G network and the WLAN are likely to be in different IP
address domains, the MN will be allocated an IP address from the
pool of addresses of the connected network. This changing of an IP
address may result in loss of connectivity.
• Therefore, in the loose coupling architecture, handoffs are less
efficient and mobility management is generally more complicated when
the user is in an active session.
BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956