BITS Pilani Pilani | Dubai | Goa | Hyderabad EA C451 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, Coupling Architectures The Tight Coupling Architecture The Loose Coupling Architecture External Packet data network Gi Loose coupling point HLR SGSN Gb Gr Gn/p Iu-ps UTRAN GRPS RAN Tight coupling point MS Mobile station Um Uu GGSN Gc HLR:Home location register SGSN:Serving GPRS support node GGSN:Gateway GPRS support node Source: Ch22- P indd
BITS 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 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 WLAN to the 3G core network via an SGSN emulator. Thus, the IEEE 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
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 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: 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), location- based service, Multimedia Message Service (MMS),.
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 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
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.