• Journal of Broadcast Engineering
• /
• v.15 no.4
• /
• pp.487-497
• /
• 2010

In this paper, we propose a hard handover scheme which adaptively decides important handover parameters such as hysteresis and time-to-trigger values considering the load difference between the target and serving cells. First of all, the hysteresis value can be automatically adjusted according to the load difference, thus it is used to decide the handover trigger time. As a result, through the adaptive hysteresis scheme, handover drop rate is improved. However, this adaptive hysteresis scheme has a problem that the ping-pong effect, which occurs due to the frequent movement of mobile stations at the cell boundary, is increased. Therefore, to solve this problem, we propose a novel adaptive time-to-trigger scheme with the time-to-trigger which is in inverse proportion to the hysteresis value already established by the adaptive hysteresis scheme which adapts to the changing load difference between the target and serving cells. The simulation results show that the proposed adaptive time-to-trigger scheme based on the adaptive hysteresis is better than existing schemes in terms of handover drop rate and ping-pong generation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.3A
• /
• pp.240-249
• /
• 2011

In this paper, we consider a cell management and handover method in an IEEES02.16e based femto-cell systems. In a femto-cell system, Mobile Stations (MS) and Base Stations (BS) are temporarily overloaded during the process of MOB_NBR-ADV message because it includes huge information of macro-cell and a large number of femto-cells. Also, MS can be handover into another cell frequently, i.e. ping-pong phenomenon, if it is located in a overlapped cell area. In a femtocell system, so-called ping-pong phenomenon will burden the network opreation. In this paper, we propose construction of MOB_NBR-ADV message and it provides fast scanning and efficent handover by means of preselecting the candidate target femto-cells. Also, an adaptive method of hysteresis margin for handover is proposed. The simulation results show that the proposed schemes improve the MS's handover-related performance in terms of scanning power and scanning time compared with the conventional managements scheme of femto-cell systems.