Evaluation of handover target cell determination algorithms for heterogeneous cellular environments

We describe a handover procedure as consisting of two main phases: the first one is the measurement collection and evaluation which is processed parallel to the target cell determination algorithm; the second phase is the handover triggering and execution process. We mainly focus on the first part of the handover procedure and more precisely on the target cell determination algorithm. In GSM, the main criterion used to choose the target base station (BS) and to trigger off a handover is the path loss criterion. We introduce three target cell decision handover algorithms which are based on the combination of three criteria. We focus on the target cell determination algorithm. In GSM, this choice is done implicitly when computing the handover triggering conditions. Furthermore, in GSM standard specifications, only a path loss-like condition is taken into account to determine the target BS. We propose the target cell determination algorithm to be processed before the handover triggering conditions are evaluated. The target cell determination algorithm outputs a list of candidate cells for handover. The first cell of the list is the preferred cell towards which the mobile station (MS) should handover prior to any other one. Once this list has been determined, the handover triggering conditions are evaluated taking into account the first cell characteristics (path loss, capacity and type) of the list