Why IMT-Advanced

3G networks faced elemental issues in trying to accommodate the projected demand for mobile Internet service. One such issue is the high cost of either expanding the network or the network operation in general. Such costs became a substantial consideration when addressing the 3G network performance in densely populated areas or when trying to overcome coverage deadspots. Of particular importance is the performance at the cell-edge, that is, connection quality at overlaps between the coverage areas of neighboring cells, which have been repeatedly remarked to be low in 3G networks. Such problems would usually be addressed by increasing the deployment of Base Stations (BS), which in addition to their high costs entail additional interconnection and frequency optimization challenges.

Figure 1.2 IMT-Advanced Timeline.

Certain performance aspects of 3G networks were also expected to be more pronounced. Some aspects were due to the scaling properties of the 3G networks, for example, delay performance due to increased traffic demand. The general support for different levels of mobility also suffered greatly in WCDMA-based networks. Perhaps most critical was the indoors and deadspot performance of 3G networks, especially when various studies have indicated that the bulk of network usage is made while being at either the office or at home.

Combined, the above issues made it cumbersome for operators to respond to the ever increasing demand. Meanwhile, handling specific heterogeneities have made it harder for both operators and user equipment vendors to maintain homogeneous and streamlined service and production structures. For example, the spectrum mismatch between even neighboring countries in 3G deployments prevented users from roaming between different networks—and at times even requiring the user to utilize (and synchronize between) different handsets. At the same time, despite the availability of multi-modal user equipment for a long time, it has thus far been difficult to maintain handovers across the different technologies.