We focus on what wireless systems might look like 10-15 years from now, if certain technological constraints are lifted. We then see integrated wireless systems that may cover perhaps a whole city center, with thousands of radio transmitters/receivers working in a very tightly coordinated ways. These systems may begin to be deployed in small scales, e.g. within buildings, or in restricted environments such as along highways with dense traffic, and then gradually grow in scale and complexity.
The key aspect that would be radically improved by multipoint transmission that provides macro-diversity would be the shadow fading: Users who are shadowed from one transmitter may not be so severely shadowed from other transmitters. This principle is used today in OFDM-based broadcasting systems such as DAB or digital TV. The challenge is to employ it, to the extent that it is sensible, also for non-broadcasting scheduled packet data transmission.