LTE Radio and Cellular Technology served with LTE baseline 2 X 2 MIMO simply by combining the single APs of two adjacent sectors forming virtual MIMO arrays. Inter-eNB cooperation is the conventional solution for building a CA between adjacent sites based, for example, on fast and broadband fiber interconnections among all involved eNBs. Typically, the CA will be lim- ited to a few eNBs. Specifically for the UL, from time to time replacement of the eNBs forming the CA might be useful to adapt to varying IF con- stellations. For moving UEs, different eNBs might appear and disappear as strongest interferers due to varying shadowing conditions, with a typical large-scale parameter correlation of about 50 m in urban environments. Especially useful is intersite cooperation in countries like South Korea or China, where fiber deployment has reached a quite mature status. But one should keep in mind that, even if fibers are available, there might be sig- nificant leasing fees for using these fibers, generating a lot of unwanted operational expenditure (OPEX) for an MNO. Distributed antenna systems (DASs) are based on RRHs that might be located at the edges of a building, at different locations in a shopping mall, or on different nearby buildings. The eNB with the CU serving the RRHs is located at one site, SO the CAs are formed without any backbone network. The RRHs are typically connected to the baseband processing unit (BBU) over the open base station architecture initiative (OBSAI) [25] or common public radio interface (CPRI) [26], which carry data samples, resulting in very high data rates. For this reason, small distances will require fiber con- nections between BBU and RRH. Larger DAS deployments might face similar infrastructure challenges, as has been known for inter-eNB coop- eration, if already existing fibers cannot be relied upon. d. Distributediselforganizing (DSO) CAs with or without inclusion of relay nodes (RNs) have been developed to overcome backbone restrictions and specifically to relax latency requir