Energy optimization in unsynchronized TDD systems for joint uplink downlink scheduling

Energy is an important resource in wireless communications systems that has to be optimized in order to guarantee low interference in the network as well as efficient use of the available resources. One of the prominent options within the Long Term Evolution (LTE) standard is the Time Division Duplexing (TDD) option where both Uplink (UL) and Downlink (DL) share the same bandwidth and they are allocated on different times. One of the major problems in the practical implementation of TDD systems is that adjacent cells may have different loads for their UL and DL, so that the resources are allocated in a different portion between UL-DL. Such an unsynchronization among cells generates interference that downgrades the system performance. This paper calculates the optimum amount of energy that should be allocated to each entity in the system to mitigate the interference effect and to guarantee minimum Quality of Service (QoS) satisfaction at all receivers. Closed form expressions and computer simulations show the advantages of the proposed energy allocation scheme.