Recently

a new generation mobile communication system

which is named B3G (Beyond 3G) or 4G

has been put into the schedule and become one of the hotspots of international research.On the other hand

Multi-In-Multi-Out (MIMO) system is a very promising frame for B3G

not only for its high potential of increasing frequency efficiency

improving communication quality and possessing flexibility structure

but also for its capability of providing plenty of room for all kinds of new technologies.Based on this frame

a novel network constructing policy-Group Cell and its special handover method-Group Handover are put forward to combat the frequent handover problem in smaller cells.In this paper

the basic idea of the two concepts is explained in detail

and problems together with research directions in this area are investigated.