Lozano Solsona, AngelHeath, R. W., Jr.Andrews, Jeffrey G.2015-04-132015-04-132013Lozano A, Heath RW, Andrews JG. Fundamental limits of cooperation. IEEE Transactions on Information Theory. 2013 Sep 19; 59(9): 5213-26. DOI 10.1109/TIT.2013.22531530018-9448http://hdl.handle.net/10230/23405Cooperation is viewed as a key ingredient for interference/nmanagement in wireless networks. This paper shows that/ncooperation has fundamental limitations. First, it is established/nthat in systems that rely on pilot-assisted channel estimation the/nspectral efficiency is upper-bounded by a quantity that does not/ndepend on the transmit powers; in this framework, cooperation/nis possible only within clusters of limited size, which are subject/nto out-of-cluster interference whose power scales with that of the/nin-cluster signals. Second, an upper bound is also shown to exist/nif the cooperation extends to an entire (large) system operating/nas a single cluster; here, pilot-assisted transmission is necessarily/ntranscended. Altogether, it is concluded that cooperation cannot/nin general change an interference-limited network to a noiselimited/none. Consequently, existing literature that routinely assumes/nthat the high-power spectral efficiency scales with the logscale/ntransmit power provides only a partial characterization. The/ncomplete characterization proposed in this paper subdivides the/nhigh-power regime into a degrees-of-freedom regime, where the/nscaling with the log-scale transmit power holds approximately,/nand a saturation regime, where the spectral efficiency hits a ceiling/nthat is independent of the power. Using a cellular system as an/nexample, it is demonstrated that the spectral efficiency saturates/nat power levels of operational relevance.application/pdfeng© 2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works./nThe final published article can be found at http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6482234info:eu-repo/semantics/articlehttp://dx.doi.org/10.1109/TIT.2013.2253153Wireless communicationsInterference,Cooperative systemsWireless networksinfo:eu-repo/semantics/openAccess