Preemption and QOS management algorithms for coordinated and uncoordinated base stations

This paper addresses the problem of resource allocation and quality of service (QoS) management in a downlink communication system where the users are allowed to be attached to and receive data from one or several cooperating base stations (BSs) under orthogonal frequency division multiple access (OFDMA). Under the assumption that only information regarding the link path loss is available at each transmitter, the problem of power and bandwidth allocation to minimize transmission power subject to minimum rate (i.e., QoS) constraints is written as a convex optimization problem. Considering that the transmission power per BS is limited, the Lagrange multipliers of the optimization problem are exploited either to efficiently identify which are the candidates to be preempted whenever unaffordable power consumption arises, or to relax the target rate constraints for the ongoing connections. In the second case, the Lagrange multipliers are used in combination with the Newton- Raphson algorithm to adjust the QoS of the users in the system according to the available BS power.