3GPP all IP architecture

The 3GPP all IP architecture relies on mobile IP (MIP) infrastructure for roaming between different access gateways. Thus, MIP home agent and foreign agent are introduced in reference architecture.A wireless IP network consist of two components: a wireless access network and a fixed corenetwork. There are important issues that should be addressed in wireless IP networks in order toprovide a seamless service in both fixed and mobile environments. Perhaps the most challenging issue is resource management and quality of service provisioning. This is even more difficult considering that there is no native resource management or quality of service control function in traditional IP networks. Current wired IP only offers the best effort service model which treats all packets from all users equally. In wireless environments due to specific characteristics of wireless channel, QoS provisioning is even more challenging. Furthermore, each wireless access network, has potentially its own wireless technology and administrative policies which makes it more difficult to have a uniform resource management mechanism. The goal of this section is to discuss resource management architectures for integrating different wireless networks in order to provide seamless connectivity. The proposed architectures adopt IP as the common network layer protocol. To minimize the amount of change inside the network, we use the existing resource management mechanisms proposed for IP networks as much as possible. In all proposed architectures, the core network is based on the Diffserv model.

DiffServ-Based Architecture

In DiffServ-Based architecture, not only the core network is DiffServ-capable but also the access networks are DiffServ-capable. In this architecture acellular network overlaid by DiffServ domains operates as the radio access network.In the previous subsection, we discussed how the static nature of DiffServ can degrade the radio resource utilization in wireless access networks. Therefore, a more fine-grained architecture based on IntServ was proposed. It was also mentioned that because of limited radio resources, the number of flows and consequently the amount of state information required for IntServ/RSVP7 operation is quite reasonable with respect to the scalability requirement. These assumptions are reasonable for low-bandwidth systems, e.g. a 3G networks. However, when the access network operates on a high-bandwidth IP-based wireless technology, e.g. a wireless LAN, these assumptions do not stand for the following reasons: Typically, such technologies have high capacities in order of several Mbps. Therefore, it is possible to have a large number of flows simultaneously in the network. Considering that future cellular technologies such as 4G will expand the available radio resources to the same orders, then this will be problematic even in those environments.

• Due to the inherent IP-based architecture of these technologies, traffic flows have different characteristics and requirements than those in conventional cellular networks. The applications intended for such environments are delay-tolerant and do not require strict QoS guarantees (web browsing compared to voice calls for instance). Also, their generated traffic is bursty in nature and hence it is difficult to describe their bandwidth requirements accurately a priori. The types of applications supported by conventional cellular networks are limited which facilitate the classification of their requirements. This is not true in wireless LAN environments.

• Mobility patterns are different in WLAN-based hot spot environments compared to those in conventional cellular networks. Hot spot traffic is more chaotic and hence more difficult to predict. As a result, it is not possible in practice to reserve appropriate amount of resources beforehand for each individual connection which may handoff to the hot spot.In contrast, traffic aggregates are usually more smooth and predictable thanks to the law of large numbers. This suggest that class-based resource management is more feasible in wireless environments.

• The wireless environment is rapidly changing. Wireless channel capacity fluctuates over time with interferences. So, it is difficult to achieve strict QoS guarantees similar to those in wireline networks with fairly stable channel quality. In this case coarse grained QoS guarantees like those offered by DiffServ are sufficient and in fact more appropriate for the target application types. For all above reasons we believe that the DSB architecture is a more appropriate candidate for future all-IP wireless networks than the ISB architecture.