On Optimal Relay Placement and Sleep Control to Improve Energy Efficiency in Cellular Networks
The authors consider the joint optimization of Relay Station (RS) placement and RS sleep/active probability in order to enhance the energy efficiency of a one-dimensional cellular network. When the RSs are always active, they derive the conditions for optimal RS placement that minimizes transmission power of Base Stations (BSs) and RSs, subject to a user rate requirement. The closed-form placement solution is obtained for a path-loss exponent of two, and a simple numerical method for the solution under general values of the path-loss exponent is proposed and evaluated. When the circuit power consumption of active RSs is considered, RSs should enter sleep mode to save power.