Title :
Impact of Interference Coupling - Loss of Convexity
Author :
Boche, Holger ; Naik, Siddharth
Author_Institution :
Heinrich Hertz Inst., Tech. Univ. of Berlin, Berlin, Germany
Abstract :
In interference coupled wireless systems, where it is not possible to "orthogonalize" all the users in the system, we characterize the impact of interference coupling on the convexity of certain utility functions and problems. We introduce a general class of competitive user utility functions and natural competitive user utility functions. We further introduce the signal-to-interference based utility functions, which are based on physical layer parameters in wireless systems. We prove the conditions, which when satisfied result in a competitive user utility function being a signal-to-interference ratio based utility function. We further show that there exists no natural competitive user utility function, which is convex or concave. Furthermore, we show that a sum of weighted combination of natural competitive user utility functions is not convex or concave. Such functions are commonly encountered in wireless communication systems, e.g. rate or MMSE as a function of signal-to-interference ratio. We show that such rate maximization or MMSE minimization problems are not convex programs under our specified conditions.
Keywords :
electromagnetic coupling; least mean squares methods; radiofrequency interference; MMSE minimization; competitive user utility functions; convexity loss; interference coupled wireless systems; interference coupling; natural competitive user utility functions; signal-to-interference ratio; Costs; Delay; Interference; Physical layer; Power system modeling; Quality of service; Resource management; Throughput; Wireless communication; Wireless networks;
Conference_Titel :
Global Telecommunications Conference, 2009. GLOBECOM 2009. IEEE
Conference_Location :
Honolulu, HI
Print_ISBN :
978-1-4244-4148-8
DOI :
10.1109/GLOCOM.2009.5426117