LTE, LTE-Advanced and WiMAX: Towards IMT-Advanced Networks

Access Network Architecture

The introduction of 3GPP's X2 interface marked a particular evolutionary step in the design of access network infrastructure. Traditionally, base stations were connected to network cores in centralized star configuration, with each base station directly and independently connected to the access core. Such configuration, exercised up until the earlier releases of UTRAN, results in substantial handover latencies, especially when it came to IP-based mobility. Similarly with WiMAX, which is neutral to the choice of network core, support has been made to realizing flat architectures.

A direct advantage of flat architecture is greatly reduced handover latency times, which was mandated by the IMT-Advanced requirements letter. This advantage, consequently, results in reduced disruptions for multimedia IP handover as the users traverse the network [12]. Through internetworking base stations, user context can be transported from a serving base station to the target one without having to go back to the network core. As was observed, additional optimizations are also possible in instances where the user terminal moved between a base station and its children relay stations.

Careful network design, however, is required in order to achieve these desirable characteristics. Design considerations would include aspects such as where is it best to connect the access network to the core or the identifying topology configurations that match the projected traffic load while ...