چكيده به لاتين
In this thesis, resource management problem for the downlink of a cloud radio access network (C-RAN) is studied. Multi-tier base stations (BSs) with different transmit powers are employed to expand coverage and to improve network capacity of fifth-generation networks (5G). Among available technologies to realize the 5G, C-RAN is more economical and energy efficient, due to both centralized processing and joint resource allocation. Therefore, C-RAN is more promising for accademic and industry communities. Each of the BSs in a C-RAN is connected to the base band units pool (BBU Pool) via capacity-limited backhaul links and each user is connected to a subset of BSs that is called a cluster. The BBU Pool transmits each user’s data to a cluster of BSs through the backhaul links; the BSs in each cluster then cooperatively serve users through joint beamforming. The main objective of this thesis is resource allocation in the C-RAN with taking into account the limitations on the radio resources. Therefore, efficient algorithms are presented to solve the joint optimization problem under the two following design criteria: 1) minimization of total power consumption at the network, and 2) maximization of the system utility (data rate). In the first criterion, the optimization problem of total system power consumption is discussed with considering target rate for each user and power budget of BSs. The total power consumed by network includes the BS transmission power, BS activation power and load-dependent backhaul power. In the objective function of problem, there are a discontinuous and non-convex indicator function. To tackle the problem, we utilize a logarithmic and exponential smooth function. Then problem is solved using transformation into a convex Semi-Definite Programming (SDP). In the second criterion, the weighted sum rate (WSR) maximization problem is discussed for a given power budget for the BSs, backhaul capacity and interference control constraints. In general, sum rate maximization problem is NP-hard. To overcome this, the equivalence between weighted sum rate maximization and weighted minimum mean squared error (WMMSE) is utilized.
Keywords: Cloud radio access network, power minimization, sum rate maximization, weighted minimum mean squared error.
