This paper considers optimum allocation of transmission powers in next generation networks. The proposed framework is general enough to cover both emerging heterogeneous network (HetNet) architectures and cognitive radio (CR) networks. There are two types of users in our model. Type 1 users (T1U) represent either femtocell users in a HetNet, or secondary users in a CR network. Type 2 users (T2U) represent either macrocell users in a HetNet, or primary users in a CR network. T1Us share the same frequency band with T2Us, and they form an uplink to their intended base station (i.e., either the femtocell base station or the secondary base station) while causing interference to T2Us. The optimum power allocation strategy maximizing the aggregate communication rate of T1Us is found under individual transmission power constraints and a total interference power constraint at T2Us. It is shown that the optimum power allocation exhibits a binary structure, which means links are either "on" or "off", up to at most one exceptional fractional power level. Further, it is shown that T1Us transmitting at positive power correspond to the ones having better "joint" power and interference channel gains. Applications of these results are illustrated for well-known fading models such as Rayleigh, Rician-K, and Nakagami-m fading.
In this work, the issue of joint transmitter receiver filter optimization for channel shortening is addressed for a frequency selective multiuser multiple input multiple output system. The channel impulse response is shortened according to the minimum mean square error criterion and under a maximum transmit power limit. Channel duality is used to solve the problem due to the simplicity of the uplink, and then the solution is transformed to the downlink channel if required. The proposed method covers the equalization and shortening of both the broadcast, multiple access, interference, and MIMO frequency selective channels as special cases.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.